Method for Inhibiting Microbial Binding to Surfaces

The present invention relates to compounds with a variety of biological activities and more particularly, to a series of block copolymers that have a wide variety of effects on living cells and organisms.

The present invention is a class of compounds that has a wide variety of profound biological effects. Background material concerning several of these biological activities is discussed hereinbelow.

Immune Stimulating Compounds

The immune system is a highly complex system of cells and tissues that requires the cooperation of a large number of different cell types. The systems of the body that make up the immune system network are variously categorized as belonging to the hematopoietic system, the reticuloendothelial or phagocytic system and the lymphoid system.

The hematopoietic system is located in the bone marrow and is responsible for supplying the various precursor and accessory cells of the immune systems. The reticuloendothelial system is made up of the phagocytic cells that are responsible for destroying or neutralizing foreign material that may enter the body. The lymphoid system is made up of lymphocytes, and is responsible for the overall regulation of the immune system and for the production of antibodies.

The tissues of the lymphoid system are generally classified as the central tissues and the peripheral tissues. Two central lymphoid tissues of mammals are bone marrow and thymus. In addition, fowl have a third central lymphoid organ, the bursa of Fabricius, which is critical to the development of the immunoglobulin-producing cells. It is thought that the mammals have a bursal equivalent associated with the intestinal tract. Lymph nodes, spleen, tonsils, intestinal lymphoid tissue (Peyer's patches) and other collections of lymphocytes constitute the peripheral lymphoid tissues.

In mammals, the bone marrow, if considered as a single tissue, is the largest tissue of the body. In the average human adult the total weight of the bone marrow is about 3 kg. Marrow fills the central core of nearly all bones. Bone marrow has three types of tissue: vascular tissue, adipose tissue and the tissue directed to hematopoiesis or blood cell formation. The vascular tissue is the circulatory system that supplies nutrients and removes wastes from the actively growing cells. The hematopoietic tissue is responsible for the formation of erythrocytes, platelets, granulocytes and monocytes, and lymphocyte precursors. Adipose tissue consists of fat cells which contribute little to the function of the bone marrow.

The other central lymphoid tissue is the thymus- a bilobed organ situated in the anterior thoracic cage over the heart. In other species, the thymus may be distributed along the neck and thorax in several lobules.

Embryologically, the thymus emerges from the third and fourth branchial pouches. The human thymus is a fully developed organ at birth and weighs 15 to 20 grams. By puberty it weighs 40 grams, after which it atrophies or involutes becoming less significant structurally and functionally. Atrophy of the thymus with age is a characteristic of all species which is associated with aging and the cessation of growth. The incidence of age related diseases increases as the thymus shrinks and thymus-dependent immunity decreases. This age-associated decrease in thymic weight, called involution, is accompanied by changes in the thymic structure and a general decline in thymic function. Transient involution of the thymus may also occur as a consequence of a stress or infection. Thymic involution may be controlled hormonally; castration slows involution while injection of corticosteroid hormones accelerates involution. Numerous studies have demonstrated that the thymic involution associated with increasing age parallels a reduction of T-lymphocyte-mediated immunity and increased incidence of diseases associated with aging. Many diseases and treatments can accelerate involution of the thymus; virtually none are known to enhance growth of the thymus or reverse involution.

Anatomically, the thymus is a pouch of epithelial cells filled with lymphocytes, nourished and drained by the vascular and lymphatic systems and innervated by the autonomic nerves. The epithelial cells and other structural cells divide the thymus into a complex assembly of continuous lobes, each of which is heavily laden with lymphocytes. The epithelial cells produce hormones and regulate some of the activities of the lymphocytes. The lymphocyte population is greatest in the cortex or outer portion of each lobule. The inner section, the medulla, has more epithelial cells and fewer lymphocytes but the lymphocytes are more mature.

Lymphocytes can generally be classified as either T-lymphocytes or as B-lymphocytes. B-lymphocytes are responsible for the production of antibodies (immunoglobulin) in response to a challenge by a particular antigen. T-lymphocytes are responsible for the general regulation of the immune system and are also the principal mediators in cell-mediated immune responses. They also influence the proliferation of bone marrow cells and are probably involved in the growth and differentiation of other organs as well.

All lymphocytes are ultimately derived from stem cells in bone marrow. These lymphocyte precursors are dispersed into the blood where they course through many organs. However, critical events take place in the thymus and bursa of Fabricius (or its mammalian equivalent) that imprint the lymphocytes with special functions and that regulate the development into either T or B-lymphocytes.

Life-span studies of lymphocytes of most mammalian species divide lymphocytes into two fractions--those with a short span (mostly large lymphocytes) of 5 to 7 days and the small lymphocytes with a life span measured in months or even years. The former are usually B-lymphocytes and the latter are usually T-lymphocytes.

B-lymphocytes respond to immunologic phenomena very differently from a T-lymphocyte in practically every instance. T-lymphocytes are formed in the thymus from lymphoblasts that left the bone marrow. This maturation is expressed morphologically as a reduction in cell size to about 7 .mu.m in diameter. The thymic cortex is rich in lymphocytes of all sizes. These thymocytes are not morphologically distinguishable from lymphocytes in other tissues, but they are immature and antigenically identifiable by the presence of several cell surface antigens including the .o slashed., or T antigen, a distinctive surface marker antigen that separates the T-lymphocyte from the B-lymphocyte.

Enumeration of lymphocytes indicate that 65% to 85% of all lymphocytes in the blood are of the T type. Lymphocytes of the thoracic duct fluid are nearly 90% to 95% of the T variety and those in the Peyer's patches or the gut are 50% to 65% T-lymphocytes. The T-lymphocyte population of lymph nodes, particularly in the deep conical region, is high, but is low in the tonsil and the appendix.

When the T-lymphocyte contacts a recognizable antigen in the appropriate context, it passes through a phase of growth and cell division known as lymphocyte transformation to produce a large population of its own kind. The antigen must first be "processed" by macrophages and then presented to T-lymphocytes.

T-lymphocytes are actually divided into several subsets and the role they play in the immune system is complex. The T-lymphocyte is responsible for the phenomenon known as the cell-mediated immune response. In a cell-mediated immune response, the T-lymphocytes that recognize a cell-bound antigen begin producing and secreting a wide variety of proteins that affect the activity of other types of cells in the immune system. These proteins include lymphokines that attract, activate and hold phagocytes at the site of the antigen and interferons that provide protection against virus infection.

The T-lymphocyte is also an important regulator of B-lymphocyte function. The antigen-exposed T-lymphocyte may have either of two direct and opposite effects on B-lymphocytes depending on the subclass of T-lymphocyte. The major subclasses are the helper cell and the suppressor cell. Helper T-lymphocytes are necessary for a complete B cell response to T-lymphocyte-dependent antigens. T-lymphocyte dependent antigens tend to be the more complex antigens such as bacterial proteins, virus proteins and other large complex proteins in general.

Unlike helper T-lymphocytes, suppressor T-lymphocytes block the development of effector B and T lymphocytes. Specific suppressor T-lymphocytes have now been demonstrated to play a large role in tolerance to many proteins, both in antibody and cell-mediated immune responses. In addition, genetic unresponsiveness to some antigens is due to the greater stimulation of suppressor T-lymphocytes than of helper T-lymphocytes by these antigens.

Thus, in the normal, healthy animal, the thymus is normally active only during the early years of life. During these early years of thymic activity, the thymus supplies the animal with the T-lymphocytes which will serve the animal for the rest of its life. In certain diseases, such as rheumatoid arthritis, the thymus may regain some activity during adult life. This demonstrates that the adult thymus retains capacity to function and that involution is not necessarily permanent. At least partial function might be restored if the appropriate agents were available.

Acquired T-lymphocyte deficiency diseases of adults are characterized by a depletion of circulating T-lymphocytes. The symptoms expressed in these diseases include an inability to mount a cell-mediated immune response to an antigen challenge. An example of an acquired T-lymphocyte deficiency disease is acquired immune deficiency syndrome, or AIDS.

AIDS is a disease caused by the human T-lymphocyte lymphotrophic virus (LAV or HTLV-III). The virus specifically attacks T-4 helper lymphocytes, a subgroup of T-lymphocytes that plays a major role in defending the body against infectious diseases. Depletion of this subset of lymphocytes is manifested by an increased incidence of opportunistic infections like Pneumocystis carinii and certain cancers. More specifically, the virus enters the T-lymphocyte and incorporates viral encoded DNA into the DNA of the host T-lymphocyte. As long as the infected T-lymphocyte remains inactivated, the virus will quietly remain in the DNA of the host cell. This will not kill the cell but may impair its function. When the infected T-lymphocytes are activated by stimuli such as a specific antigen, the viral DNA in the host DNA is expressed and produces new viral particles. The host T-lymphocyte is then killed and lysed, releasing new viral particles that can invade and kill other T-lymphocytes. The loss of T-4 lymphocytes is profound and occurs even faster than can be accounted for by direct viral killing of the cells. This has led some investigators to postulate that the infection somehow shuts off the production of T-4 lymphocytes. In any case, the thymus in the normal adult is no longer functioning and the killed T-lymphocytes cannot be replaced, leaving the patient vulnerable to subsequent infections. Especially striking are recent studies of the thymuses of deceased AIDS patients ranging in age from 10 months to 42 years. AIDS victims have profound thymic involution- much more extensive than in age-matched patients who died of other causes.

The cure of a person with AIDS will probably require one agent to eliminate the virus and other agents to cause the body to replace T cells that have been killed by the virus. The first step is to eliminate the AIDS virus from the patient. This will have to be supported by other therapies to induce restoration of immune function. Studies to date with macrophage activating agents, interferon inducers and lymphokines have been disappointing, possibly because their targets, T-lymphocytes, do not exist in sufficient numbers. Interleukin 2 restores the function of one subset of non T-cells (natural killer cells) but has no effect on a host of other serious defects. More drastic measures can be performed. One potential method of restoring the immune system is by transplanting bone marrow from healthy donors. However, this is a dangerous procedure. It may produce lethal graft versus host disease unless the patient's donor is an identical twin.

Another area where there is a need to re-establish not only the immune system, but also the hematopoietic system, is in total body irradiation for treatment of leukemia. When a patient undergoes high dose total body irradiation, the entire immune system is destroyed. The usual treatment after the irradiation is to perform a bone marrow transplant with marrow from a close relative. If the transplant is successful, the new marrow will produce new cells, thereby restoring both red blood cells and white blood cells to the body. However, this is a dangerous treatment that is successful in only a fraction of the cases. Localized radiation of tumors and several types of chemotherapy also produce suppression of T-cell mediated immunity.

What is needed is a safe and effective method of re-establishing T-lymphocyte function. One method of re-establishing T-lymphocyte function is by treating existing T-lymphocytes so that they resume their normal immune functions. Agents that have been shown to be effective in certain situations in stimulating T-lymphocytes include macrophage activating factors, interferon inducing agents, lymphokines and cytokines. However, in a disease such as AIDS or in the case of irradiation in which the T-lymphocyte population has been destroyed, this type of treatment is not effective because the number of T-lymphocytes is severely depleted. In these cases, an effective method of causing the thymus to produce new T-lymphocytes would be the treatment of choice. However, to date, there is no effective treatment that will cause the thymus to reverse the process of involution and produce new T-lymphocytes.

Autoimmune Diseases

Autoimmune diseases are characterized by the development of an immune reaction to self components. Normally, tissues of the body are protected from attack by the immune system; in autoimmune diseases there is a breakdown of the self-protection mechanisms and an immune response directed to various components of the body ensues. Autoimmune diseases are for the most part chronic and require lifelong therapy. The number of recognized autoimmune diseases is large and consists of a continuum ranging from diseases affecting a single organ system to those affecting several organ systems. With increased understanding of the molecular basis of disease processes, many more diseases will likely be found to have an autoimmune component. Specific examples of autoimmune diseases are presented below.

Systemic lupus erythematosus (SLE) is an inflammatory, multisystem disease characterized clinically as a relapsing disease of acute or insidious onset that may involve any organ in the body. Clinically, symptoms are due to disease affecting the skin, kidneys, serosal membranes, joints and heart. Anatomically, all sites have in common vascular lesions with fibrinoid deposits and immunologically, the disease involves antibodies of autoimmune origin, especially antinuclear antibodies (ANA). The ANA are directed against both DNA and RNA. Autoantibody development appears to be multifactorial in origin, involving genetic, hormonal, immunologic and environmental factors.

The morphologic changes seen in organs result from the formation of circulating immune complexes and their deposition in a variety of tissues. Although many organs can be affected, some are affected more than others. Lesions of joints, the kidneys, heart, and serous membranes are responsible for most of the clinical signs. The course of SLE is extremely variable and unpredictable. An acute onset with progressive downhill course to death within months can occur. The usual course however, is characterized by flareups and remissions spanning a period of years or even decades. It usually arises in the second or third decades of life, but may become manifest at any age.

Acute attacks are usually treated by adrenocortical steroids or immunosuppressive drugs. These drugs often control the acute manifestations. With cessation of therapy the disease usually reexacerbates. The prognosis has improved in the recent past; approximately 70 to 80% of patients are alive 5 years after the onset of illness and 60% at 10 years. Lifelong therapy is required to control the disease.

At one time SLE was considered to be a fairly rare disease. Better methods of diagnosis and increased awareness that it may be mild and insidious have made it evident that its prevalence may be as high as 1 case per 10,000 population. There is a strong female preponderance--about 10 to 1.

Rheumatoid arthritis is a systemic, chronic, inflammatory disease that principally affects the joints and sometimes many other organs and tissues throughout the body. The disease is characterized by a nonsuppurative proliferative synovitis, which in time leads to the destruction of articular cartilage and progressive disabling arthritis. The disease is caused by persistent and self-perpetuating inflammation resulting from immunologic processes taking place in the joints. As is the case with most autoimmune diseases, the trigger that initiates the immune reaction remains unidentified. Both humoral and cell-mediated immune responses are involved in the pathogenesis of rheumatoid arthritis. The majority of patients have elevated levels of serum immunoglobulins and essentially all patients have an antibody called rheumatoid factor (RF) directed against a component of another antibody class.

The key event in the pathogenesis of the arthritis is the formation of antibodies directed against other self antibodies. Why these antibodies are formed is unknown at present. It has been suggested that the process is initiated by the formation of antibodies or immunoglobulins against an unknown antigen, possibly an infectious agent. When the antibodies combine with the antigen, conformational changes occur in a portion of the antibody molecule creating new antigenic determinants. The appearance of new determinants evokes an antibody response against the antibody molecule and results in the formation of anti-immunoglobulin antibodies or rheumatoid factor. T cells may also be involved in the pathogenesis of rheumatoid arthritis. A large number of T cells are found in the synovial membrane, outnumbering B cells and plasma cells. Additionally, procedures to decrease the population of T cells (such as draining the thoracic duct), result in remission of symptoms.

The most destructive effects of rheumatoid arthritis are seen in the joints. Classically, it produces symmetric arthritis, which principally affects the small joints of the hands and feet, ankles, knees, wrists, elbows, shoulders, temporo-mandibular joints and sometimes the joints of the vertebral column. The clinical course is highly variable. After approximately 10 years, the disease in about 50% of the patients becomes stabilized or may even regress. Most of the remainder pursue a chronic, remitting, relapsing course. After 10 to 15 years, approximately 10% of patients become permanently and severely crippled. The disease usually has its onset in young adults but may begin at any age and is 3 to 5 times more common in women than in men.

Rheumatoid arthritis is a very common disease and is variously reported (depending on diagnostic criteria) to affect 0.5 to 3.8% of women and 0.1 to 1.3% of men in the United States.

Multiple sclerosis is another disease that is thought to be caused by autoimmune mechanisms. The cause of multiple sclerosis is unknown but seems to be multifactorial. Susceptibility or resistance may be genetically determined; something in the environment interacts with the human host at the proper age to cause biochemical and structural lesions in the central nervous system. The systemic immune response and the response of the central nervous system become involved. Although the cause and pathogenesis of multiple sclerosis are unknown, it is widely believed that immune abnormalities are somehow related to the disease. Three possible mechanisms have been postulated: infection, autoimmunity, and a combination of the two. Suppression or modulation of the immune responses may be the key.

The graphic distribution of multiple sclerosis indicates that the disease is acquired from an environmental factor. Approximately 200 studies of the geographic distribution of multiple sclerosis have been conducted and have shown that regions of high prevalence (30 to 80 cases per 100,000 population) in northern Europe between 65 and 45 degrees north latitude and in the northern United States and southern Canada, as well as in southern Australia and New Zealand. In contrast, regions of low risk, including most of Asia and Africa, have a prevalence of 5 or fewer cases per 100,000.

Myasthenia gravis is an autoimmune disorder caused by antibodies directed against the acetylcholine receptor of skeletal muscle. Present information indicates at least three mechanisms whereby acetylcholine receptor antibody may interfere with neuromuscular transmission and thus induce myasthenia gravis. Acetylcholine receptor antibody may interfere (directly or indirectly) with acetylcholine receptor function. In both experimental allergic myasthenia gravis and human myasthenia gravis, the extent of acetylcholine receptor loss parallels the clinical severity of the disease, suggesting that acetylcholine receptor antibody-induced acceleration of acetylcholine receptor degradation is important in the development of myasthenia gravis. Complement-mediated destruction of the postsynaptic region is the third possible cause. Other disorders, especially those presumed to be autoimmune in origin, can occur in association with myasthenia gravis. Thyroid disease, rheumatoid arthritis, systemic lupus erythematosus, and pernicious anemia all occur more commonly with myasthenia gravis than would be expected by chance.

The prevalence of myasthenia gravis in the United States is one per 20,000.

The foundation of therapy for autoimmune diseases is treatment with immunosuppressive agents. The basis for this therapy is attenuation of the self-directed immune response with the primary aim being to control symptoms of the particular disease. The drugs utilized to achieve this aim are far from satisfactory, in that adverse side effects are numerous and control of the disease is many times difficult to achieve. The problem is compounded by the chronicity of the disease with effective therapy becoming more difficult with time. An indication of the severity of particular diseases is seen in the willingness to accept greater risks associated with therapy as the disease progresses. Currently available therapy is distinctly non-selective in nature, having broad effects on both the humoral and cell-mediated arms of the immune system. This lack of specificity can limit the effectiveness of certain therapeutic regimens. The main groups of chemical immunosuppressives are alkylating agents, antimetabolites, corticosteroids, and antibiotics. Each will be discussed briefly.

The corticosteroids, also called adrenocorticosteroids, are fat-like compounds produced by the outer layer, or cortex, of the adrenal gland. The adrenal cortex is an organ of homeostasis influencing the function of most systems in the body. It is responsible for adaptation of the body to a changing environment. Therapeutic use of the corticosteroids for autoimmune disease is based on their two primary effects on the immune system: anti-inflammatory action and destruction of susceptible lymphocytes. They also effect a redistribution of lymphocytes from peripheral blood back to the bone marrow. The use of corticosteroids is not without adverse side effects however, particularly during the course of lifelong treatment which is required for many of the autoimmune diseases. Major side effects of steroids are:

1. Cushing syndrome

2. Muscle atrophy

3. Osteoporosis

4. Steroid induced diabetes

5. Atrophy of the adrenal glands

6. Interference with growth

7. Susceptibility to infections

8. Aseptic bone necrosis

9. Cataract development

10. Gastric ulcer

11. Steroid psychosis

12. Skin alterations

13. Nervous state accompanied by insomnia

Attempts to minimize side effects incorporate alternate day or less frequent dosage regimens.

A recently developed immunosuppressive agent is the antibiotic cyclosporin A. The antibiotic has greatest activity against T cells and does not seem to have much direct effect on B cells. The drug is being evaluated for the treatment of autoimmune diseases for which it shows some promise. Side effects include hair growth, mild water retention, renal toxicity, and, in older patients, nervous system disorder symptoms have been observed.

Other drugs are used alone or in combination with those listed above and include gold salts and antimalarials, such as chloroquine. Another class of drugs, the nonsteroidal anti-inflammatory drugs, are used extensively in arthritis. These drugs provide analgesia at low doses and are anti-inflammatory after repeated administration of high doses. Nonsteroidal anti-inflammatory drugs all act rapidly and their clinical effects decline promptly after cessation of therapy. They do not prevent the progression of rheumatoid arthritis and do not induce remissions. Immunostimulants, such as levamisol, have also been used in many autoimmune diseases but side effects have generally limited their use.

Growth Promoting Compounds

With an ever-increasing world demand for food, there is constant pressure to increase the rate of production of food. In the early 1950s, researchers unexpectedly discovered that an antibiotic ingredient in chicken mash was a "growth factor." The finding drastically changed the nation's livestock and poultry production and was an economic boon for pharmaceutical companies. Food animals are now raised under highly controlled conditions and receive specialized feed with a variety of growth promoting additives.

Routine antibiotic administration to animals has become almost universal since the discovery that the addition of small amounts of antibiotics such as penicillin, tetracycline and sulfamethazine, to animal feed increases the growth of pigs and cattle. In 1979, about 70% of the beef cattle and veal, 90% of the swine, and virtually 100% of broilers reared in the United States consumed antibiotics as part of their daily feed. This use, accounting for nearly 40% of antibiotics sold in the United States, is estimated to save consumers $3.5 billion a year in food costs.

Animals raised under modern conditions optimized for growth promotion receive rations containing high proportions of protein, usually in the form of soybean or cottonseed meal, and high percentages of grains such as corn or milo, a type of sorghum. Feed additives which have been used include such hormones as diethylstilbestrol, which also increases the rate of weight gain, and tranquilizers that prevent the effects of the stress brought on by confinement conditions from causing disease or weight loss.

Cattle ordinarily require 10 pounds of feed to produce one pound of weight gain. Under optimal growth promoting conditions and with enriched feed they gain one pound with only 6 pounds of feed.

Modern farming has greatly reduced the labor required to raise farm animals. In broiler chicken raising, where intensive methods have had the most dramatic effect, it took 16 hours of labor to raise a flock of 100 broilers in 1945; in 1970 that figure was reduced to 1.4 labor hours, in part because of the use of automated confinement facilities and associated advances in breeding and nutrition.

Although hormones and antibiotics have greatly increased the rate of growth of food animals, the use of such additives has not been without problems. One of the hormones that was commonly used as a growth stimulant, diethylstilbestrol, or DES, has been shown to be a carcinogen and has been banned from further use in most countries.

When antibiotics are mixed in animal feed, the compounds are spread throughout the environment exposing microorganisms to the antibiotics. The constant exposure of the microorganisms to antibiotics puts biological pressure on the microorganisms to develop a resistance to the antibiotics. This can result in a microorganism that is resistant to antibiotics and causes especially severe and difficult to treat infections.

An antibiotic-resistant microorganism is potentially a serious pathogen because it is difficult to control. If the organism causes an infection in an animal or in a human, the infection may not be controlled with conventional antibiotics. If the infection is serious, there may not be time to determine which antibiotics are effective against the infecting bacteria. The problem has been especially serious when antibiotic-resistant organisms in meat are consumed by people who themselves take antibiotics for treatment of disease. Antibiotics inhibit many of the normal microorganisms in the respiratory and gastrointestinal tracts. This allows the resistant ones to proliferate rapidly and produce more serious disease. The combination of antibiotic-resistant organisms from food and ineffective antibiotic treatment of people has caused most of the deaths due to Salmonella food poisoning reported in the United States in the past several years.

As a result of the increasing appearance of antibiotic-resistant bacteria in feed lots and several serious epidemics caused by antibiotic resistant bacteria, there is increasing governmental pressure to ban the use of antibiotics in animal feed. Consequently, there is an immediate and increasing need for new, safe and effective growth stimulators of farm animals.

Reducing Enteric Microorganisms

While many enteric microorganisms are beneficial to their host and reside in the host's gut without adverse consequence, many other enteric microorganisms are pathogenic and cause various and often severe disease states. For example, typhoid fever is caused by Salmonella, bacillary dysentery is caused by Shigella, and cholera is caused by Vibrio. These disease states remain a major public health threat in lesser developed countries. One approach to managing these diseases would be to treat patients, either before or after manifestation of disease symptoms, to reduce the number of microorganisms in the gut.

Additionally, the prevalence of Salmonella in animals, particularly birds, more particularly poultry such as chickens, turkeys, pheasant, quail, geese, ducks, emus, ostriches and other ratites, constitutes a constant source of expense to the farming and food industries and a health threat to consumers.

Further, pet fecal odor is a significant problem, particularly for house bound pets such as cats. Fecal odor is caused by certain intestinal microorganisms, and is diminished or eliminated if odor-producing microorganisms are reduced in the intestinal tract of the pet.

Consequently, there is an urgent and immediate need for compositions and methods for reducing enteric microorganisms and pathogens in humans, in farm animals, particularly Salmonella in poultry such as chickens, and in household pets.

Antitumor Compounds

Malignant, or cancerous, tumors are defined by their invasion of local tissue and their ability to spread or metastasize to other parts of the body. The incidence of tumors is high--it is the second leading cause of death in both children and adults. A malignant tumor, by definition, always kills (unless treated) because of its invasive and metastatic characteristics. The tumor grows locally by encroachment into the normal tissues surrounding it. The tumor spreads to distant sites by the breaking off of malignant cells. These cells then move through the blood and lymphatic systems, attach themselves, and begin to grow as new colonies.

The factors controlling tumor growth are poorly understood. Tumors in laboratory animals may be transplanted to a second host using only a single tumor cell. This facility suggests that only one normal cell need become transformed (cancerous) for tumor growth to begin. It is thought, however, that many transformed cells die or remain latent or dormant for extended periods before successful tumor growth is established. Tumors have been experimentally induced in animals by chemical, physical, and viral agents, and by radiation and chronic irritation.

Leukemia is a term given to tumors of the blood-forming organs. The acute and chronic leukemias, together with the other types of tumors of the blood, bone marrow cells (myelomas), and lymph tissue (lymphomas), cause about 10% of all cancer deaths and about 50% of all cancer deaths in children and adults less than 30 years old. At least 4 million people now living are expected to die from these forms of cancer, assuming there are no major advancements made in the treatment of these diseases.

Conventional treatment regimens for leukemia and for other tumors include radiation, drugs, or a combination of both. In addition to radiation, the following drugs, usually in combinations with each other, are often used to treat acute leukemias: vincristine, prednisone, methotrexate, mercaptopurine, cyclophosphamide, and cytarabine. In chronic leukemia, for example, busulfan, melphalan, and chlorambucil can be used in combination. All of the conventional anti-cancer drugs are highly toxic and tend to make patients quite ill while undergoing treatment. Vigorous therapy is based on the premise that unless every leukemic cell is destroyed, the residual cells will multiply and cause a relapse.

Most of the conventional chemotherapeutic drugs that are being used in tumor therapy do not specifically kill tumor cells. Reliance is placed on the fact that, in most cancers, the cancerous cells grow faster than normal cells and will therefore utilize more of the toxic chemotherapeutic drug thereby specifically killing the cancer cell. Administration of the conventional chemotherapeutic drugs requires careful attention to the amount and concentration of the drug or combination of drugs so that the cancer cells will be killed but normal cells will survive. For this reason, it is difficult to kill all cancerous cells by conventional chemotherapy.

What is needed are compounds that will specifically and completely kill cancerous cells while not affecting normal cells. Ideally, the new compounds would take advantage of physical characteristics inherent only in the tumor cell. For example, a tumor cell may be more sensitive than normal cells to changes in ion concentrations within the cell. If a compound could detrimentally vary the internal ion concentrations of the tumor cells, then the compound could specifically kill the tumor cell while not adversely affecting normal cells.

Ionophoric Compounds

Ionophores are defined as substances capable of interacting stoichoimetrically with metal ions so as to transport the ions across a hydrophobic barrier such as a cell membrane.

It has been generally accepted that cell membranes consist of a phospholipid bilayer interspersed with globular protein molecules. The hydrophilic phosphate portions of the phospholipid are oriented at the outer edges of the membrane while the hydrophobic lipid portions face toward the center. The cell membrane is selectively permeable and will permit water, certain nutrients and essential metal ions to pass freely into the cell when needed. However, due to the double layer of nonpolar lipids in its center, the membrane is normally impermeable to highly polar molecules.

Different ionophores often have an affinity for one ion or one group of ions over another. The ions most commonly transported across cell membranes include Na.sup.+, K.sup.+, Li.sup.+, Rb.sup.+, Cs.sup.+, Ca.sup.+2, Mg.sup.+2, Ba.sup.+2, Cu.sup.+2, Fe.sup.+2, Ni.sup.+2, and Zn.sup.+2. For example, the negatively charged fungal antibiotic ionophore A23187 selectively forms an electrically neutral "encounter complex" with positively charged calcium ions. This hydrophobic molecule is capable of moving across a number of different cell membranes, and once the complex enters the cell, the calcium ion is released. This increase in intracellular free calcium has been shown to stimulate the secretion of a variety of substances such as histamine from rodent mast cells and human basophils, amylase and insulin from the pancreas, the hormone vasopressin from the pituitary, the neurotransmitter dopamine from neurons, seratonin from platelets, and catecholamines from adrenal glands. In addition, the A23187 calcium ionophore has been shown to activate sea urchin eggs.

With an ever-increasing world demand for food, there is constant pressure to increase the efficiency of production of food. Ruminant nutritionists have long sought means to manipulate and improve the efficiency of ruminal fermentation. Dietary manipulation was initially used to achieve this goal, but during the last decade a number of active antibiotic compounds, produced by various strains of Streptomyces, were discovered which improve metabolic efficiency. Although originally administered to poultry as anticoccidials, these carboxylic polyether antibiotic compounds, including monensin, lasalosid, salinomycin and narasin, have been found to exhibit ionophoric activity.

Since their discovery, antibiotic ionophores have been used extensively as feed additives to increase the efficiency of the production of poultry and ruminants. Studies have indicated that, when ionophores are added to feed, the growth of pathogens and other microorganisms within the digestive tract is inhibited, thus enhancing the efficient utilization of nutrients in the feed.

The various antibiotic ionophores appear to improve the efficiency of conversion from grain to meat by increasing the efficiency of metabolism in the rumen, improving nitrogen metabolism, and by retarding feedlot disorders such as chronic lactic acidosis and bloat. These effects are caused by a shift in the rumen microflora from bacteria less efficient in fermenting ingested feed to more bacteria that are more efficient. The change in rumen microflora population is brought about by a differential susceptibility of the bacteria to ion flux across their membranes. This influx of ions causes the bacterial cells to swell and burst.

Although antibiotic ionophores have greatly increased the efficiency of production of feed animals, the use of such additives has not been without problems. When antibiotics are mixed in animal feed, the compounds are spread throughout the environment exposing microorganisms to the antibiotics. The constant exposure of the microorganisms to antibiotics causes a resistance to antibiotics which in turn causes infections which are especially severe and difficult to treat.

An antibiotic-resistant microoorganism is potentially a serious pathogen because it is difficult to control. If the organism causes an infection in an animal or in man, the infection may not be controlled with conventional antibiotics. If the infection is serious, there may not be time to determine which antibiotics are effective against the infecting bacteria. The problem has been especially serious when antibiotic-resistant organisms in meat are consumed by people who themselves take antibiotics for treatment of disease. Antibiotics inhibit many of the normal microorganisms in the respiratory and gastrointestinal tracts. This allows the resistant ones to proliferate rapidly and produce more serious disease. The combination of antibiotic-resistant organisms from food and ineffective antibiotic treatment of people has caused most of the deaths due to Salmonella food poisoning reported in the United States in the past several years.

It is believed there is currently no single class of compounds that possesses such a wide range of biological activities. Such a class of compounds would provide a new and powerful arsenal for the treatment of disease and for increasing the world's food supply.

In accordance with the present invention, a new class of biologically-active copolymers capable of affecting biological systems in many different ways is provided. The biologically active copolymers of the present invention are capable of stimulating the growth of an organism, stimulating the motor activity of an organism, and stimulating the production of T-cells in the thymus, peripheral lymphoid tissue, and bone marrow cells of an animal.

The biologically active copolymers of the present invention also have a wide variety of effects on individual cells. These compounds have ionophoric activity, i.e., they cause certain ions to be transported across cell membranes. The compounds can cause non-cytolytic mast cell degranulation with subsequent histamine release. In addition, it has been found that certain members of this class of biologically-active copolymers are capable of specifically killing certain cancer cell lines. The biologically active copolymers are also effective against certain microorganisms.

The biologically active copolymers of the present invention can be administered orally to animals to provide specific effects on certain microorganisms that reside in the gut of the animal. For example, certain biologically-active copolymers can be administered to chickens to kill various species of coccidia that cause coccidiosis. Additionally, biologically active copolymers are administered to humans or animals to reduce the number of microorganisms in the gut. A preferred use is administering the biologically active copolymers of the present invention to poultry to reduce the number of Salmonella and other microorganisms in the poultry gut.

The biologically-active copolymers can also be added to cattle feed to effect a change in the population of microorganisms normally resident in the rumen. Under normal conditions, the microorganisms digest the cellulose eaten by cattle to form the end-product methane. Methane is essentially unusable by the cattle. By administering the biologically-active copolymers of the present invention orally to the cattle, the copolymer differentially affects the rumen microorganisms so that there is a shift in the rumen population of microorganisms resulting in an increase in propionic acid production and a decrease in lactic acid and methane. Cattle are capable of using propionate in their own metabolism, thereby increasing the efficiency of food conversion.

Methane produced by ruminant animals is a major contributor to the greenhouse effect. Methane and other hydrocarbon combustion by-products are major constituents of the greenhouse gases. The greenhouse effect is theorized to produce major climatological change in the planet's atmosphere due to the warming of the planet. The planet gets warmer because the gases in the atmosphere, such as methane, trap the radiation from the sun and do not allow the heat to reradiate away from the planet. The greenhouse gases form a thermal blanket that inhibits the release of the radiation from the sun that bombards the earth.

Addition of the biologically-active polymers to the feed of ruminants changes the microbial flora of the gut and thus reduces the amount of methane produced by the ruminants. The reduction of methane aids not only in the increased growth of the ruminants, but has the additional effect of reducing the gas that is a major factor in producing the greenhouse effect.

The biologically-active polymers also have a role in inhibiting the adhesion of microorganisms to surfaces. Adhesion of microorganisms to surfaces is the first step in the causation of many medical, dental and public health problems. If microorganisms can be prevented from attaching to a surface, then fewer microorganisms will be capable of either invading that surface or being carried to another site of attachment. If fewer microorganisms are capable of attaching, then the microorganisms will be less able to create the associated disease.

Biologic effects of the copolymers of the present invention vary with the structure of the polymer. The ability to modify the structure of these polymers to optimize particular biologic effects provides the potential to design synthetic compounds with a precision and ease not possible in other systems.

The biologically-active copolymer of the present invention comprises a copolymer of polyoxyethylene (POE), which is hydrophilic, and polyoxypropylene (POP), which is hydrophobic. The block copolymer is built on a tetrafunctional ethylenediamine initiator. In the preferred embodiment of the biologically-active copolymers of the present invention, the block copolymers that comprise the biologically-active copolymers of the present invention have the following general formulas: ##STR1## wherein: the mean aggregate molecular weight of the hydrophobe portion of the octablock copolymer consisting of polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is between approximately 5000 and 7000 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes between approximately 10% and 40% of the total molecular weight of the compound; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the total molecular weight of the octablock copolymer constitutes between approximately 60% and 90% of the compound.

In another embodiment of the biologically-active copolymer of the present invention, the block copolymer comprises a polymer of hydrophilic polyoxyethylene (POE) built on an ethylenediamine initiator. Polymers of hydrophobic polyoxypropylene (POP) are then added to the blocks of hydrophilic polyoxyethylene (POE). This results in an octablock copolymer with the following general formula: ##STR2## wherein: a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes between approximately 10% to 40% of the total molecular weight of the compound;

the mean aggregate molecular weight of the hydrophobe portion of the octablock copolymer consisting of polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is between approximately 5000 and 7000 daltons; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the total molecular weight of the octablock copolymer constitutes between approximately 60% and 90% of the compound.

The biologically-active copolymer of the present invention is usually administered by a subcutaneous, intravenous, or intramuscular injection of an effective amount of the copolymer into an animal or human. The biologically-active copolymer of the present invention can be taken orally if it is desired that the copolymer have an effect on alimentary canal microorganisms. Normally, very little of the copolymer is absorbed from the alimentary canal.

Accordingly, it is an object of the present invention to provide compounds that have a wide variety of biological activities.

Another object of the present invention is to provide compounds that can stimulate the T-cell immune system.

Another object of the present invention is to provide a compound that will stimulate the growth of the thymus in an adult animal.

Another object of the present invention is to provide compounds that can stimulate the production of bone marrow cells.

A further object of the present invention is to stimulate bone marrow and emhance recovery from radiation or other insults toxic to the bone marrow.

Another object of the present invention is to provide compounds that can accelerate and prolong growth.

Yet another object of the present invention is to provide compounds that can stimulate motor activity in animals and humans.

Another object of the present invention is to provide compounds that have ionophore activity.

Another object of the present invention is to provide compounds that can cause non-cytolytic mast cell degranulation.

Another object of the present invention is to provide compounds that can specifically kill certain tumor cell lines.

Another object of the present invention is to provide compounds that can kill or eliminate microorganisms that reside in the gut.

Another object of the present invention is to specifically immunosuppress an animal against an antigen or a hapten.

Yet another object of the present invention is to provide compounds that are capable of altering the metabolism of ruminant animals so that the efficiency of feed conversion is increased.

Another object of the present invention is to lessen the amount of greenhouse gasses in the atmosphere by reducing the amount of methane released by ruminant animals.

Yet another object of the present invention is to inhibit the adhesion of microorganisms to biological surfaces and to surfaces contacted by biological surfaces in order to reduce the amount of microorganisms that are available for disease production.

These and other objects, features and advantages of the present invention will become apparent after a review of the following detailed description of the disclosed embodiment and the appended claims.

The present invention comprises a class of biologically active copolymers which have a wide variety of biological functions which are useful in treating various pathological conditions in both humans and animals and which can also be used to increase the efficiency of food production.

The biologically-active copolymers of the present invention comprise a surface active compound with hydrophobic segments and a small proportion of hydrophile that is built upon an initiator compound. The initiator compound typically has one or more active hydrogens upon which the hydrophobic or hydrophilic polymer units are condensed. Compounds that can be used as initiators in producing the biologically active copolymers of the present invention include, but are not limited to, methylamine, ethylamine, propylamine, butylamine, amylamine, hexylamine, aniline, the alkylene polyamines, especially aliphatic primary diamines such as ethylenediamine, propylenediamine, diethylenetriamine, triethylenetetramine, tetraethylenepentamine, hexamethylenediamine, phenylenediamine, and the like. Alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, isopropanolamine, tri(t-propanol)amine, 2-amino-1-butanol, N-butyl-di(2-propanol)amine can also be used as initiators.

Furthermore, heterocyclic compounds containing a hetero nitrogen atom can be employed, such as piperazine, 2 methylpiperazine, 2,5-dimethylpiperazine, imidazimidazole, pyrazolidine, pyrazolidone, hydantoin, dimethyl hydantoin and the like. Hydroxyl amine and the hydroxylamine derivatives and aminophenol and aminophenol derivatives can also be used as initiators to produce the biologically active copolymers of the present invention.

The compositions of this invention are surface active mixtures of conjugated polyoxypropylene-polyoxyethylene compounds based on the reactive hydrogen compounds wherein chains of oxypropylene groups having a defined molecular weight are attached to the initiator of the reactive hydrogen compound at the sites of the reactive hydrogen atoms and wherein chains of oxyethylene groups are then attached to the ends of the oxypropylene chains. Alternatively, the chains of oxyethylene groups having a defined molecular weight can be attached to the initiator of the reactive hydrogen compound at the sites of the reactive hydrogen atoms and then chains of oxypropylene groups can be attached to the ends of the oxyethylene chains.

The compositions are prepared by condensing either ethylene oxide or propylene oxide with the reactive hydrogen on the initiator compound. After the first block of monomer units have been added to the initiator molecule, a second block of either propylene oxide or ethylene oxide is condensed with the reactive hydrogen on the end of the first block. It is to be understood that butylene oxide can be substituted, either all or part, for propylene oxide in the biologically active copolymers of the present invention.

It is to be noted that it is not necessary to use pure propylene oxide in producing the oxypropylene chains of the biologically active copolymers of the present invention. Small amounts, for example, up to 5 weight percent, of ethylene oxide can be included in the propylene oxide employed to prepare the hydrophobic reactive hydrogen compound-propylene oxide condensate. Likewise, the ethylene oxide condensed with the hydrophobic propylene oxide-reactive hydrogen compound condensate can also contain small amounts, such as up to about 5 weight percent, of propylene oxide.

It is further to be noted that when molecular weight is stated in this specification and claims, unless otherwise noted, there is meant the average theoretical hydrophobe molecular weight which equals the total of the grams of the propylene oxide employed per mole of reactive hydrogen compound. The end groups of polyether chains are hydroxyl groups. The number averaged molecular weight can be calculated from the analytically determined "OH Number" expressed in mg KOH/g sample. It should be understood that the absolute value of the molecular weight of a polydisperse compound can be different depending upon the methodology used to determine the molecular weight.

Alternatively, copolymers can be fractionated by a variety of methods, such as gel permeation chromatography, and analyzed for weight percent of oxyethylene and for unsaturation by proton NMR analysis. An example of such an analysis is as follows: Copolymer is dissolved in tetrahydrofuran at a concentration of 20 mg/mL. A Model 600E Powerline chromatographic system equipped with a column heater module, a Model 410 refractive index detector and Maxima 820 software package (all from Waters, Div. of Millipore, Milford, Mass.) is used to fractionate the copolymer. The chromatographic system is equipped with Ultrastyragel 10.sup.3 A and 500 A in series (Waters, Div. of Millipore, Milford, Mass.). Column size is 7.8 mm internal diameter by 30 cm. Precolumn filters #A-315 with removable 2 .mu.m fits (Upchurch Scientific, Oak Harbor, Wash.) are used for protection of the columns. 200 .mu.L (4 mg) of the copolymer in tetrahydrofuran is added to the column and the sample is run with the columns at 40.degree. C. and the detector at 45.degree. C.

All proton NMR analyses are performed in accordance with the NF procedure "Weight Percent Oxyethylene" on a Bruker 300 MHz instrument. The weight percent oxyethylene is calculated from the proton NMR spectra.

It is well recognized in the field of alkylene oxide chemistry that the polyoxyalkylene compositions one obtains by condensing an alkylene oxide with a reactive hydrogen compound, are actually mixtures of compounds rather than a single molecular compound. The mixture contains closely related homologues wherein the statistical average number of oxyalkylene groups equals the number of moles of the alkylene oxide employed and the individual members in the mixture contain varying numbers of oxyalkylene groups. Thus, the compositions of this invention are "mixtures" of compounds which are defined by molecular weight of the polyoxypropylene chains and weight percent of oxyethylene groups.

The biologically-active copolymers of the present invention comprise a surface active compound with four hydrophobic segments and a small proportion of hydrophile. Typical examples have eight segments or octablock structure with a core of either a hydrophobic or hydrophilic central structure and a hydrophilic or hydrophobic outer structure as shown in the following schematic structures. ##STR3##

The entire molecule is poorly soluble in water and is either a nonionic or weakly cationic surface active agent. The steric configuration and physicochemical properties of the molecule, rather than the chemical nature of the constituent parts, are thought to be responsible for the biologic effects of the copolymer.

The biologically active compounds of the present invention comprise blocks of polyoxypropylene and polyoxyethylene built on an alkylenediamine initiator. The blocks of polyoxypropylene (POP) and polyoxyethylene (POE) have the following structures: ##STR4##

The polymer blocks are formed by condensation of ethylene oxide and propylene oxide onto a tetrafunctional ethylenediamine initiator at elevated temperature and pressure in the presence of a basic catalyst. There is some statistical variation in the number of monomer units which combine to form a polymer chain in each copolymer. The molecular weights given are approximations of the average weight of copolymer molecule in each preparation. A further description of the preparation of these block copolymers is found in U.S. Pat. No. 2,674,619 and U.S. Pat. No. 2,979,528. (Also see "A Review of Block Polymer Surfactants", Schmolka, I. R., J. Am. Oil Chemists' Soc., 54:110-116 (1977) and Block and Graft Copolymerization, Volume 2 edited by R. J. Ceresa, John Wiley & Sons, New York (1976).

Chemical Structure

In one embodiment of the biologically active copolymers of the present invention, the block copolymer comprises a polymer of hydrophobic polyoxypropylene (POP) built on an ethylenediamine initiator. Polymers of hydrophilic polyoxyethylene (POE) are then built on the block of hydrophobic polyoxypropylene (POP). This results in an octablock copolymer with the following general formula: ##STR5## wherein: the mean aggregate molecular weight of the hydrophobe portion of the octablock copolymer consisting of polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is between approximately 5000 and 7000 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes between approximately 10% to 40% of the total molecular weight of the compound;

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the total molecular weight of the octablock copolymer constitutes between approximately 60% and 90% of the compound; and

In another embodiment of the present invention, the block copolymer comprises a polymer of hydrophilic polyoxyethylene (POE) built on an ethylenediamine initiator. Polymers of hydrophobic polyoxypropylene (POP) are then built on the block of hydrophilic polyethylene (POE). This results in an octablock copolymer with the following general formula: ##STR6## wherein:

The molecular weight of the hydrophobe portion of the octablock copolymer consisting of polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is between approximately 5000 and 7000 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes between approximately 10% and 40% of the total molecular weight of the compound;

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes between approximately 60% and 90% of the compound.

This type of polymer is called reverse copolymer because its structure is the reverse of octablock copolymers that have polyoxypropylene (POP) in the center flanked by blocks of polyoxyethylene (POE).

The octablock copolymers comprising the biologically active copolymers of the present invention include, but are not limited to, the block copolymers Tetronic.RTM. and reverse Tetronic.RTM. manufactured by the BASF Corporation (BASF Corporation, Parsippany, N.J.). These include copolymers wherein

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes between approximately 5% and 20% of the total molecular weight of the compound;

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes between approximately 80% and 95% of the compound.

A preferred biologically active copolymer is the octablock copolymer T110R1 (BASF Corporation, Parsippany, N.J.) which corresponds to the following formula: ##STR7## wherein:

The mean molecular weight of the hydrophobe portion of the octablock copolymer represented by polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is approximately 4750 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes approximately 10% of the compound by weight; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes approximately 90% of the compound by weight.

A preferred biologically active copolymers is the octablock copolymer T130R2 (BASF Corporation, Parsippany, N.J.) which corresponds to the following formula: ##STR8## wherein:

The mean molecular weight of the hydrophobe portion of the octablock copolymer represented by polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is approximately 5750 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes approximately 20% of the compound by weight; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes approximately 80% of the compound by weight.

Another preferred embodiment of the biologically active copolymers of the present invention is the compound designated T1501 (BASF Corporation, Parsippany, N.J.) which corresponds to the following formula: ##STR9## wherein: the mean molecular weight of the hydrophobe portion of the octablock copolymer represented by polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is approximately 6750 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes approximately 10% of the compound by weight; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes approximately 90% of the compound by weight.

The most preferred embodiment of the biologically active copolymers of the present invention is the octablock copolymer T150R.sub.1 (BASF Corporation, Parsippany, N.J.) which corresponds to the following formula: ##STR10## wherein:

The mean molecular weight of the hydrophobe portion of the octablock copolymer represented by polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is approximately 6750 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes approximately 10% of the compound by weight; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes approximately 90% of the compound by weight.

Biological Activities

Although not wanting to be bound by the following theory, it is believed that the biologically active polymers of the present invention act by the following mechanism:

Investigators have demonstrated hormone-mediated interactions between the thymus and the central nervous system. The biologically active copolymers of the present invention are capable of affecting this relationship. It is believed that the present invention acts by mimicking the conformation and physicochemical properties of natural hormones and neuropeptides. The biologic responses induced by the biologically active copolymers of the present invention include:

1. Stimulation of rate and duration of growth of animals;

2. Gross morphologic changes in the uterus and adrenal glands;

3. Increased motor activity including excessive grooming;

4. Diuresis;

5. Noncytolytic release of histamine from mast cells by a temperature, calcium, energy dependent mechanism which is similar to from that of somatostatin and ACTH.

It is believed that there is a structural analogy between the biologically active copolymers and hormones, such as somatostatin, adrenocorticotropic hormone (ACTH), and .beta.-endorphin. These peptides have in common a sequence of basic amino acids adjacent to spans of hydrophobic amino acids. These features are thought to be essential for function. Interaction of the oligoamine residues with cell surface anions and stabilization by adjacent hydrophobic moieties initiates the molecular program resulting in effector functions of the peptide. The block polymers have the same structural features: a central basic ethylenediamine flanked by spans of hydrophobic polyoxypropylene (POP). By means of inhibition with monovalent amines, evidence suggests that the central ethylenediamine groups function like the basic moieties of peptide hormones in stimulating release of histamine from mast cells.

In vitro studies provide direct evidence that the biologically active copolymers of the present invention act in a manner analogous to somatostatin and ACTH. Mast cells have been used as a model to study receptor mediated mechanisms through which these hormones induce their biological receptor-mediated mechanisms. Minute quantities of the polymers cause histamine release from mast cells by a temperature dependent process which requires energy and calcium and can be blocked by specific inhibitors in a manner very similar to that of somatostatin and ACTH.

Both agonistic and antagonistic effects of hormones may be elicited by the polymers. Biologic effects of the polymers vary with the structure of the polymer. The ability to modify the structure of these polymers to optimize particular biologic effects provides potential to design synthetic drugs with a precision and ease not possible in other systems.

Many chelating agents, such as ethylene-diaminetetraacetic acid (EDTA) consist of oligoamine sites flanked by hydrogen bonding groups. The addition of flanking hydrophobic moieties produces ionophores which are able to transport ions across lipid containing membranes. The compounds of the present invention have this general structure and can act as ionophores in transporting pharmacologically active compounds across artificial membranes. Consequently, the compounds of the present invention represent a new chemical type of ionophore. Some neuropeptide hormones (e.g., substance P) have ionophore activity.

The biologically-active copolymers of the present invention are also effective in causing the cortex of the thymus to begin producing new T-lymphocytes thereby replenishing the immune system with these vital regulatory cells. The copolymers also induce proliferation of large numbers of post-thymic T-cells in the lymph nodes and other peripheral lymphoid tissues.

The biologically active copolymers of the present invention also exhibit adjuvant and inflammatory activities which vary depending on the length and arrangement of the blocks of polyoxyethylene and polyoxypropylene. The reverse octablock copolymers cause active, calcium dependent histamine release from murine mast cells in vitro and the efficacy of histamine release is related to inflammatory activity in vivo.

The biologically active copolymers of the present invention when injected into an animal or a human with an antigen are effective in specifically immunosuppressing the animal or human against that antigen. For purposes of definition, antigens can be broken down into two groups: immunogens and haptens.

lmmunogens are compounds which, when introduced into a mammal, will result in the formation of antibodies. Representative of the immunogens are proteins, glycoproteins and nucleoproteins, such as peptide hormones, serum proteins, complement proteins, coagulation factors, and viral or bacterial products. The following is a partial list of representative immmunogens.

Haptens are compounds which, when bound to an immunogenic carrier and introduced into a chordate, will elicit formation of antibodies specific for the hapten. Representative of the haptens are steroids such as estrogens and cortisones, low molecular weight peptides, other low molecular weight biological compounds, drugs such as antibiotics and chemotherapeutic compounds, industrial pollutants, flavoring agents, food additives, and food contaminants, and/or their metabolites or derivatives.

The biologically active copolymers of the present invention also are active in reducing enteric microorganisms in the gut of humans and animals. Enteric microorganisms and pathogens such as, but not limited to, Salmonella, Escherichia, Klebsiella, Enterobacter, Pseudomonas, Serratia, Shigella, Campylobacter, Proteus, Edwardsiella, Yersinia , Eimeria and Vibrio are reduced in the gut by treatment with the biologically active copolymers of the present invention.

For example, Salmonella counts in the gut of chickens or other animals are reduced by administering an effective amount of the copolymers of the present invention to the chicken or other animal. A preferred method of administration for treatment to reduce enteric microorganisms in humans and animals is oral ingestion. For example, the copolymers can be administered to animals by admixing the copolymers with standard feed mixtures, which subsequently are fed to animals to be treated.

The biologically active copolymers of the present invention are also active in interfering with the adherence of microbiological organisms to surfaces. Surfaces, as used in this application, refer to both biological surfaces and to non-biological surfaces. Examples of biological surfaces include external surfaces of biological organisms, such as skin or teeth, or internal surfaces such as the mouth, throat, gut, urinary, or genital tract linings. Surfaces can also include tissue or cellular surfaces. Examples of non-biological surfaces include surfaces, whether internal or external, which come into contact with biological materials such as cutting surfaces for meat in the meat processing industry or in the home, medical instruments such as dental or surgical tools, or non-biological implements placed the body such as pins, rods or catheters.

Treating the biological or non-biological surfaces, as used in this application, includes any method of exposing the surface to a solution with or without the block copolymer. Such methods would include bathing, dipping, spraying, wiping, immersing, submerging, plunging, sprinkling, peppering, swabbing, and other applications of the block copolymer to a surface, internal or external, biological or non-biological.

Reducing the number of microorganisms bound to a surface includes decreasing the total number of microorganisms by approximately 25%, more desirably, by approximately 55%. Reducing can be used in terms of reducing the total number of microorganisms bound to a surface and in reducing the ability of microorganisms to bind to surfaces. Reducing is defined as to bring down, as in extent, amount, or degree. Reducing also means to diminish, to grow or cause to grow less or smaller, as in number, amount, or intensity. Other meanings of the term reducing include decrease, lessen, reduce, dwindle, abate, diminish, and subside.

Approximately is used herein to refer to numbers close to the stated value such that the substance to which the number refers to performs substantially the same function to achieve substantially the same result. Alternatively, approximately is generally understood to be in the range of 10% of the stated value.

The block copolymers interfere with the adherence of microbial organisms to surfaces. Though not wishing to be bound by any particular theory, it is thought the block copolymers interfere with adherence by coating the surfaces and coating any microbial organisms that may be present. Interference with the adhesion of the microbiological organism to a surface can prevent the initiation of a disease state if the surface is the cellular surface of a larger organism such as an animal or plant. Interference with the adhesion of the microbiological organism to a surface can also inhibit the transference of the organisms to other surfaces and thus prevent the spread of infection by the microorganism.

The interference by the polymer in the adhesion of microbiological organisms may also be used in products that are used to treat or coat non-biological surfaces, such as tables, floors, meat-processing equipment or implements, which are in contact with biological surfaces contaminated by microbiological organisms, such as dental or surgical tools. The polymer may be incorporated into disinfectants which may have enhanced activity because of the removal of attached microbiological organisms, and not merely from the killing of microbiological organisms.

Surfaces, both biological and non-biological surfaces, can be treated with the block copolymer compositions to prevent microbial attachment. Though not wishing to be bound by any particular theory, it is thought that the block copolymers undergo a change in solubility that is dependent on the pH of the solution. The block copolymers are poorly soluble in aqueous solutions above approximately pH 6. When the pH of the solution is lowered below approximately pH 6, more particularly to pH 5.5 or 5.6, the block copolymers become soluble. An acidic solution, with the block copolymers in solution, could be washed over a surface, either biological or non-biological, with an alkaline surface. The alkaline surface would change the pH of the microenvironment where the solution touches the table, and the block copolymers would become insoluble. The block copolymers would then leave the solution and coat the surface, thus preventing microbial adherence to the surface and coating any microbes that might have been present on the surface.

The interference with the adhesion of the microbiological organism may also inhibit the penetration and invasion by the microbiological organism into a biological surface such as a plant or animal. This interference could block the infective process at an early stage and possibly lower the risk of infection.

The adhesion of a microorganism to a surface is an initial step in the colonization of the surface by many microorganisms, such as bacteria, viruses, fungi, and other parasitic organisms. Bacteria includes both gram-positive bacteria and gram-negative bacteria, and other non-gram staining types of bacteria. Usually there is a specific attachment molecule on the microorganism that interacts specifically with a receptor on the surface. This specificity of attachment may limit the attachment of the microorganisms to specific cellular types within a larger organism or may limit the species that the microorganism can colonize. Many bacteria have molecules on their outer surface that specifically attach to cellular receptors present only on specific cellular types. The adhesion to the cellular surface can be mediated by bacterial pili, or by smaller attachment structures such as a fringe or glycocalyx. For example, Escherichia coli adheres betters to intestinal lining cells than to oral lining cells, whereas streptococcci adhere better to the oral lining cells.

The disease state created by microorganisms is initiated and maintained because the microorganism can adhere to, colonize and subsequently penetrate, the cellular surface of the larger organism. Bacterial adherence to cellular surfaces creates the characteristic disease state associated with that bacteria. For example, adherence of Shigella to intestinal surfaces leads to the disease of shigellosis or bacterial dysentery. One of the major diseases in swine is caused by the filamentous structures on the surface of enteropathic E. coli. which binds specifically to porcine intestinal cells. In humans, pathogenicity of M. pneumoniae and N. gonorrhoeae is dependent on bacterial structures which mediate adherence to tracheal and urethral cells, respectively.

Another area in which bacterial attachment plays a role in pathogenicity is in dental disease. Attachment of bacteria to oral surfaces can lead to such dental diseases as dental caries (cavities) or periodontal disease, destruction of the gums and underlying tissues. Much of the tooth loss found in the human population is due to the destruction of oral tissues by bacteria. Interference with the adherence of the bacteria to these surfaces could inhibit the formation of dental plaque and the attendant problems of caries and periodontal disease.

A major concern of public health officials and the consumer public at large is the contamination of food animals by microbial organisms. In the farming operation, discussed above, the crowded conditions inherent in mass production fanning lead to high rates of infection among the animals if an infectious agent is introduced. If the infectious agent can be prevented from adhering to the animal, the spread of infection could be slowed.

If an animal, carrying an microorganism or infectious agent, comes into a slaughter house, the microorganism can be transferred from the initially infected animal to other animals. Even though the animals are dead, the microorganism can still adhere to the animal surfaces and be transmitted to other slaughtered animals at differing stages of processing or even transferred to the consumers who buy the processed meat in stores or restaurants.

During the last decade, the importance of poultry and eggs as vehicles for human salmonellosis has become a major concern of United States regulatory agencies, the poultry/egg consuming public, and the poultry industry. Indeed, control of salmonellosis in commercial poultry has been identified by the Southeastern Poultry and Egg Association and the National Broiler Council as one of the major problems facing the United States poultry industry. The more recent emergency of egg-born Salmonella enteritidis (SE) infections in humans has increased industry and regulatory agency interest in this particular strain of Salmonella in egg producing poultry. Furthermore, the emergence of Salmonella enteritidis phage type IV in Europe and a number of developing countries continues to cause concern not only because of the zoonotic potential of this isolate, but also due to the animal health problems associated with this more virulent organism.

Due to the molecular structure, surface-active properties, and charge, the polymers of the present invention could interfere with Salmonella enteritidis attachment to poultry skin and meat in commercial processing plants where cross-contamination of poultry carcasses with this, and related intestinal pathogens, has become a major problem. An estimated 8-9 billion broiler chickens will be raised and processed in the United States alone in 1994. Currently several expensive procedures are utilized by major poultry companies with the intent of reducing salmonellae and related food-borne pathogens. The presently commercially-available compounds for preventing samonellae attachment to poultry skin and meat within poultry processing plants all have serious detractors which include low efficacy, high cost, potential human toxicity problems, off-flavors, and environmental pollution problems.

It is to be understood that the preferred biologically-active compound may differ in structure depending upon the biological activity that one desires to elicit.

Administration of the Biologically Active Copolymers

The biologically-active copolymers of the present invention are generally poorly soluble in water. Although the compounds can be injected into an animal or human in aqueous media, it is preferable that the biologically-active copolymers of the present invention be injected as an oil-in-water or water-in-oil emulsion. A mineral oil or other oily substance such as Drakeol 6VR or Drakeol 5 (Penreco, Butler, Pa.) can be used as the oil phase of the emulsion. The aqueous phase can be physiologic phosphate buffered saline or other physiologic salt solution. The ratio of oil to water is preferably between approximately 80:20 and 1:100.

Typically, an oil-in-water emulsion is prepared by mixing between approximately 0.5 to 50 grams of the biologically active copolymers with 5.0 ml of mineral oil in a homogenizer. Next, 95.0 ml of phosphate buffered saline (0.85M sodium chloride, pH 7.3) containing 0.2% polyoxyethylene sorbitan monooleate (Tween 80, Atlas Chemical Industries, Wilmington, Del.) and 50 mg bovine serum albumin (BSA, Sigma Chemical Co., St. Louis, Mo.) is added. The mixture is homogenized thoroughly to form a fine emulsion. The BSA and Tween 80 are used to stabilize the emulsion. It is to be understood that the method of preparing the emulsion, the proportions of oil and water and the type of oil used are not critical. An effective emulsion could be prepared by using a blender, by sonication or other means well known to those of ordinary skill in the art. It is to be further understood that other carriers, emulsifiers, aqueous solutions and adjuvants that are known to those of ordinary skill in the art can be used with the biologically active copolymers of the present invention.

Water-in-oil emulsions are prepared as follows. A stock oil-emulsifier mixture is prepared by blending mineral oil with approximately 5% to 10% of a water-in-oil emulsifier. A mixture of 94.5% oil (Drakeol, Penreco, Butler, Pa.), 4.5% Sorbitan monooleate (Span 80, Atlas Chemical Industries, Wilmington, Del.) and 0.5% polyoxyethylene sorbitan monooleate (Tween 80, Atlas Chemical Industries, Wilmington, Del.) is commonly used. A commercial blend, Freund's incomplete adjuvant (Difco, Detroit, Mich. or Sigma Chemical, St. Louis, Mo.), is also suitable. Approximately 0.5 to 5.0 grams of the biologically active copolymers are added to either 60 ml of the oil emulsifier mixture or to 40 ml of a physiologic saline solution similar to that used in the oil-in-water emulsion described above. The oil-emulsifier mixture is placed in a blender. The physiologic salt solution is added in three aliquots with vigorous homogenization to insure that a fine water-in-oil emulsion is prepared. Again, it is to be understood that the method of preparing the emulsion is not critical. Numerous variations of the composition of the aqueous and oil phases, their proportions and means of emulsification will be apparent to those skilled in the art and could be used with biologically active copolymers in practicing the invention.

The biologically active copolymers of the present invention are effective with only one injection of compound being administered to an animal. However, in certain cases, subsequent injections may be necessary to achieve maximum stimulation of the immune system or other desired effect. The mode of injection can be subcutaneous, intramuscular or intravenous. A preferred mode of injection is subcutaneous. Intravenous injection is hazardous because of the toxic effects of embolic emulsions.

The optimum amount of the biologically active copolymers in an injection varies with the size of the animal being treated. With animals such as rats or mice, the optimum amount of biologically active copolymers is between approximately 0.5 and 5 mg per animal. With larger animals a larger quantity of biologically active copolymers is required in the injection for optimum results. With humans, cattle or swine, the dose varies with the age, size and condition of the individual but approximates 5 to 500 mg in most cases.

The poor solubility of the block copolymers can be exploited to provide selective coating of surfaces. Though not wishing to be bound by any particular theory, a change in the solubility of the block copolymers can be effected by changing the pH of the solution containing the block copolymers. The block copolymers are in an emulsion form when the pH of the solution is above approximately pH 6. If acetic acid is added to lower the pH to below approximately pH 6, the block copolymers become soluble. A desirable pH range for solubility of the block copolymer is approximately pH 5.5 to 5.6. If the pH is then raised to above approximately pH 6, the block copolymers become insoluble, leave the solution and coat the surrounding surfaces.

The pH of the surrounding milieu causes the shift in solubility of the block copolymers from an insoluble phase to a soluble phase, or from a soluble phase to an insoluble phase. This phase change leads to the reduction of bacteria retained in the gut of an organism. For example, in humans, substances which are swallowed are subjected to pH conditions in the stomach which are much lower than pH 6. This highly acidic condition is followed by the alkaline conditions of the small intestine which then neutralize the swallowed substances. These physiological conditions would have the following effect on the block copolymers. The block copolymers, in an oil and water emulsion, are ingested. In the stomach, due to the gastric acids, the pH of the solution is reduced to below pH 6 and the block copolymers become soluble. Upon reaching the small intestine, the pH of the solution is raised above pH 6 and the block copolymers become insoluble. Because the block copolymers are no longer soluble, they form a coating on the surfaces of the tissues of the small and large intestines and also coat the bacteria. This coating, formed by the block copolymers leaving the solution, interferes with the attachment of bacteria and thus reduces the number of bacteria that can bind in the intestines.

The change in solubility of the block copolymers due to pH shifts can also be used in the meat processing industry. The block copolymers are dissolved in a solution wherein the pH is kept below approximately pH 6 by a nontoxic acid solution, such as acetic acid. The meat to be processed is then added to the acidic solution with block copolymers. Localized pH changes, which occur in the microenvironment of the surface of the added meat, increase the local pH to above approximately pH 6 so that the block copolymers are no longer soluble at the surface of the meat. The insoluble copolymers than form a protective coating on the surfaces of the meat and prevent attachment by bacteria. Thus, the meat is protected from bacterial contamination throughout the processing procedures. At the final step before packaging, the meat can be rinsed in an acidic solution to resolubilize the block copolymers and remove the block copolymers from the meat surfaces.

Any of the proposed uses of the block copolymers, to reduce attachment and thus colonization, of microorganisms could take advantage of this solubility shift due to pH changes. The pH of surfaces, including nonbiological surfaces, could be selectively lowered and raised to create or remove protective coatings of the block copolymers. Protective coatings could be easily removed by an acidic solution, and a new protective coating could be easily reapplied once the surface's pH was adjusted by a more alkaline wash.

The solubility shift of the block copolymers is theorized to be temperature independent. Thus, surface temperatures would not have to change, just the surface pH would change to effect a change in the solubility of the block copolymers. This temperature independence allows for protective coatings to be applied in processes which must remain cold, such as the processing of meat. Cold conditions also help control the rate of microbial growth.

The following specific examples will illustrate the invention as it applies in particular to stimulating the immune system in mice and rats. It will be appreciated that other examples will be apparent to those of ordinary skill in the art and that the invention is not limited to these specific illustrative examples.

FIG. 1 shows histamine release from mast cells that have been exposed to several copolymers of the present invention.

FIG. 2 shows influx of sodium ions into red blood cells that have been exposed to several copolymers of the present invention.

FIG. 3 shows the relationship between footpad swelling and sodium flux and several of the copolymers of the present invention.

FIG. 4 shows the effect of T150R1 on mouse thymus in vivo.

FIG. 5 shows the effect of the copolymer of the present invention on motor activity in rats.

FIG. 6 shows the differential tumoricidal activity of T150R1 on K-652 cells and HL-60 cells as measured by cell viability.

FIG. 7 shows the differential tumoricidal activity of T150R1 on K-652 cells and HL-60 cells as measured by tritiated thymidine uptake.

FIG. 8 shows the differential tumoricidal activity of T150R1 and T150R2 on K-652 cells and HL-60 cells as measured by release of lactic dehydrogenase.

FIG. 9 shows active immunosuppression by T150R1.

FIG. 10 shows adoptive immunosuppression by cells from a rat treated with T150R1.

FIG. 11 shows stimulation of thymus cell proliferation by T150R1 in Lewis rats as measured by increased number of cells.

FIG. 12 shows stimulation of thymus cell proliferation by T150R1 in Lewis rats as measured by increased in vivo incorporation of tritiated thymidine .

The mast cell degranulation activity of several of the copolymers of the present invention are shown in this Example. Block copolymers were obtained from BASF Corporation, Parsipanny, N.J., and are shown in the following Table A.

The copolymers in Table A range in physical form from viscous liquids to flakes. Measurement of the liquid copolymers was made using a positive displacement pipette based on a density approximately equal to that of water (range 1.01-1.03). Since the solubility of these materials in aqueous medium decreases with increasing temperature, all dilutions were made in cold (4.degree. C.) buffer.

Mouse peritoneal mast cells were obtained by lavage from female C3H mice (Charles River, Wilmington, Mass.). For each experiment one or two animals were sacrificed using dry ice vapors and the peritoneal cavity injected with 10 ml ice cold Dulbecco's phosphate-buffered saline (hereinafter PBS) (Gibco, Grand Island, N.Y.) containing 10 Ul heparin. The peritoneum was massaged for 30 seconds and the fluid withdrawn. Cells were washed twice in PBS and counted using Alcian blue. The average yield was 4-6.times.10.sup.6 cells/animal with mast cells comprising 3-5% of the total cells. Cells were resuspended in Tyrode's solution (see Pearce, F. L. and White, J. R. (1984) Agents Actions 14, 392) containing 1 mg/ml bovine serum albumin (Miles Laboratories, Naperville, Ill.). Tyrode's solution was made using distilled, deionized water with 137 mM NaCl, LiCl, or KCl as the major cation species with 1 mM CaCl.sub.2 added as indicated.

Cells were prewarmed to 37.degree. C. for 5 minutes and then added in 200 .mu.l aliquots (2-5.times.10.sup.3 mast cells) to polypropylene tubes containing an equal volume of buffer with or without copolymer. Total histamine content of the cells was obtained by lysing the cells in 3% perchloric acid. Cells were incubated for 30 minutes at 37.degree. C. and then centrifuged for 5 minutes at 1500.times.g at 4.degree. C. Supernatants were analyzed for histamine content using the automated fluorometric method (See Siraganian, R. P. (1974) Anal. Biochem. 57, 383). All samples were tested in duplicate and the results are presented as means of sample pairs. Net percent histamine release was calculated by the following formula: ##EQU1##

All of the copolymers shown in Table A were tested for their ability to cause non-cytolytic histamine release. The five copolymers were incubated at a concentration of 100 .mu.g/ml with the mast cells. At the end of 30 minutes incubation with the copolymer, the percent net histamine release was measured. These results are summarized in FIG. 1. As shown, the rates obtained for these copolymers revealed a spectrum of activity with the T130R2 copolymer showing the greatest histamine release and the T150R8 showing the least activity.

The ionophore activity of the biologically active copolymers was determined by measuring the influx of ions into human red blood cells.

Human blood anticoagulated with lithium heparin was washed 3 times in 0.9% NaCl by centrifugation for 10 minutes at room temperature at 150.times.g and diluted to 10% hematocrit in saline. For Na.sup.+ flux measurements the saline contained approximately 5 .mu.Ci .sup.22 Na.sup.+ /ml (Amersham Corp., Arlington Heights, Ill.). For determination of Ca.sup.++ flux, cells were diluted in saline containing 4 mM CaCl.sub.2 with .sup.45 Ca++ tracer (ICN Biomedicals, Inc., Irvine, Calif.) at approximately 10 .mu.Ci/ml. Cells were warmed to 37.degree. C. in a water bath and then added to equal volumes of prewarmed buffer containing copolymers and mixed by vortexing. For Na.sup.+ or Ca.sup.++ flux measurements, 50 .mu.l duplicate aliquots of each whole suspension were removed during incubation to measure total activity. At selected time points, 200 .mu.l duplicate aliquots were removed and added to 1.5 ml minicentrifuge tubes (American Scientific Products, McGaw Park, Ill.) containing 200 .mu.l SF1154 silicone oil (General Electric Co., Waterford, N.Y.).

For Na.sup.+ and Ca.sup.++ measurements, the supernatants above the oil were aspirated and the portion of the tube above the oil was washed twice by carefully adding and then aspirating distilled water. After removal of most of the oil the cells were resuspended in 250 .mu.l distilled water. Residual .sup.22 Na.sup.+ activity was measured using a gamma counter and remaining .sup.45 Ca.sup.++ activity was measured in a beta counter after mixing 100 .mu.l of the lysate with 3 ml Opti-Fluor LSC cocktail (United Technologies Packard). Determination of potassium efflux was performed as above except that the cells were mixed with copolymer in normal saline at a 10% final hematocrit. After centrifugation, supernatants were removed and assayed for potassium content by flame emission spectroscopy using an IL 443 Flame Photometer (Instrumentation Laboratory, Inc., Lexington, Mass.).

Residual counts in the pellets or the amount of K.sup.+ in the supernatants were normalized for pellet hemoglobin content which was determined using Drabkin's solution. There was no difference between hemoglobin content of pellets incubated with any of the copolymers used or with buffer alone indicating that copolymers are not cytolytic. All experiments were performed at least in duplicate.

Five copolymers were tested for their ability to cause influx of Na.sup.+ ions over a period of 30 minutes. The results of these tests are summarized in FIG. 2.

Comparison of the rates obtained for these copolymers revealed a spectrum of activity which correlated with their ability to trigger in vitro histamine release from murine mast cells and in vivo inflammation as determined by peak footpad swelling following subplantar injection in mice. These results are summarized in FIG. 3.

The larger the sodium flux observed with each copolymer, the more histamine release and inflammation the copolymer induced.

Three octablock and seven reverse octablock copolymers were obtained from the BASF Parsipanny, N.J. Resident peritoneal leukocytes were obtained by lavage as described in Example 7.2.

Six of seven reverse octablock copolymers were found to release significant amounts of histamine from mouse peritoneal mast cells. These results are summarized in Table B.

The amount of histamine released by the various copolymers was related to the level of inflammation at the site of injection, i.e., the more inflammatory the copolymer in vivo, the more histamine release in vitro.

Six week old female ICR outbred mice were injected in the rear footpads with an oil-in-water emulsion containing copolymer 1.25 mg T150R1, 2.5 mg mineral oil and 25 .mu.g bovine serum albumin in 0.05 ml of 0.01M phosphate buffered saline containing 0.1% Tween 80. Identical injections were made into both rear footpads. Controls were animals that were injected with emulsions without the T150R1. Animals were sacrificed at 4 days 1, 2, 3 and 6 weeks. Their thymuses were carefully dissected free of connective tissue and were weighed.

Microscopic examination revealed that the changes in the thymus were limited almost exclusively to the cortical lymphocytes. Their numbers were markedly reduced three days after injection, but approached normal at one week. After the transient decrease in the number of lymphocytes, the size of the thymus glands of treated animals increased markedly over those of controls. The medullary areas demonstrated little change, but the cortical areas were much larger than normal. The cortical areas of the thymus were composed of immature and mature small lymphoid cells. The reduction in size of the thymus in controls was the expected result of normal involution with aging. Thus, the injection of T150R1 prevented involution during the time studied. In several experiments carried out with identical protocol, the thymuses of treated animals were consistently nearly twice as large as those of the controls. Some treated mice were followed for over eighteen months and appear healthy.

Table C shows that the inhibition of involution of the thymus is long term. The weights of the body, thymus and spleens were after 18 months.

Histological examination of the thymuses showed little thymus tissue in control mice. Thymuses of injected mice had "young looking" thymus tissue.

Mice were injected via the tail vein with the following preparations:

1. Saline at 4.degree. C.

2. 2.5 mg of copolymer T150R1 in saline at 4.degree. C.

3. 1 g beads coated with T150R1 copolymer.

Each experimental group contained four mice. After 6 days, the mice were sacrificed and the thymuses were carefully dissected and weighed. The results of this experiment are summarized in FIG. 4.

This Example shows that the copolymer dissolved in cold saline and injected directly into the blood of an animal causes a marked increase in the weight of the thymus.

Mice were injected in the footpad with related copolymers and other forms of emulsion. Copolymers T130R2 and T1501 had weaker effects in stimulating the increased size of the thymus. The results of an experiment with water in oil emulsions is shown in Table D.

Mice were treated as in Example 7.6 and carefully observed for a period of several months. The following observations were made. The treated mice were larger than control mice. The treated mice appeared to exhibit increased motor activity including more general activity in the cage, excessive grooming and the treated mice ate more than the control mice.

The uterus of the treated female mice was larger and appeared to have increased vascularity. There was an increased prominence of Peyer's patches (gut associated lymphoid tissue) in the treated animals.

The biologically active copolymer of the present invention was administered to mice. The growth of the mice was then measured after six weeks.

Oil-in-water emulsions were prepared with 1 mg bovine serum albumin (BSA), 50 mg of the indicated copolymer (all copolymers were manufactured by BASF Corporation, Parsipanny, N.J.) and 100 .mu.l mineral oil (Drakeol 6VR, Penreco Refining Company, Butler, Pa.) in 2 ml of phosphate-buffered saline (PBS) with 0.2% Tween 80 (Sigma Chemical Co., St. Louis, Mo.). The mixture was homogenized in a homogenizer. The oil, copolymer and BSA were homogenized together before adding the phosphate buffered saline. The mixture was then further homogenized to form a fine emulsion.

Emulsions were prepared of each of the copolymers shown in Table D. Each of these copolymers is comprised of blocks of polyoxyethylene (POE) and polyoxypropylene (POP) arranged in the fashion previously described for copolymer T150R1. They differ from one another only in the size of the blocks. Each has characteristic physiochemical and biologic properties.

Mice were injected with 50 .mu.g of BSA, 2.5 mg copolymer and 5 mg oil in 0.1 ml of an oil-in-water emulsion divided between the two hind feet. Their weights six weeks later are summarized in Table E.

The mice injected with the emulsion containing the copolymer T150R1 were visibly larger than those injected with any of the other copolymers. All of the mice appeared healthy.

All of the copolymers used in Table E consist of blocks of polyoxypropylene (POP) and polyoxyethylene (POE) attached in the same reverse octablock configuration. The compounds differ from one another only in the size of the blocks of each compound. These differences, however, confer distinct physicochemical properties on the copolymers which correlate with their biologic activities.

Oil-in-water emulsions were prepared using 1 mg bovine serum albumin (BSA), 50 mg of either copolymer T1501 or T150R1 (BASF Corporation, Parsippany, N.J.) and 100 .mu.l mineral oil (Drakeol 6VR, Penreco, Butler, Pa.) in 2.0 ml phosphate buffered saline with 0.2% Tween 80 in a homogenizer as described above. The control oil-in-water emulsion was prepared identically except that no copolymer was used.

Copolymer T1501 has the following general structure: ##STR11## and copolymer T150R1 has the following general structure: ##STR12##

The hydrophobic polyoxypropylene block in each of the structures have a mean aggregate molecular weight of approximately 6750. They each contain approximately 10% hydrophilic polyoxyethylene.

The water-in-oil emulsion was prepared using 50 mg of either copolymer T1501 or T150R1, 1.2 ml Freund's incomplete adjuvant (Sigma Chemical Company, St. Louis, Mo.), and 0.8 ml Hank's balanced salt solution (Gibco, Grand Island, N.Y.), containing 1 mg bovine serum albumin (BSA). The control emulsion was prepared identically except that it contained no copolymer.

Mice were injected with 2.5 mg of copolymer in 0.1 ml of either the oil-in-water or water-in-oil emulsion. Controls consisted of mice injected with the same dose of an identical emulsion which contained no copolymer. The injections were given subcutaneously and the total dose was divided between the two hind feet. Their weights at six weeks are summarized in Table F.

The block copolymer designated T150R1 was highly effective in stimulating growth when used in both water-in-oil emulsion and in oil-in-water emulsion. The block copolymer designated T1501 was effective in stimulating growth in a water-in-oil emulsion.

The effect the biologically-active copolymer of the present invention has on the motor activity of rats was measured. The animals used in this Example were adult male Sprague-Dawley rats.

The rats were individually housed in suspended cages. All rats were housed for three weeks in the same room prior to initiation of the study.

Baseline measurements of horizontal locomotor activity were made for one week prior to administration of the copolymer. Horizontal activity was measured using an activity box (Omnitech, Inc., Columbus, Ohio) interfaced with a Vic 20 microcomputer.

The activity box has two rows of 8 photocells positioned at 90.degree. angles. When the light path to a photocell is broken, a voltage drop occurs and is recorded by the computer. Activity determinations were made on all nine rats at three day intervals.

The test and control solutions were prepared as o follows: The aqueous phase was prepared by mixing 100 ml of PBS and 0.2 ml of Tween-80. This mixture was stirred approximately 5 minutes. 200 .mu.l of oil (Drakeol, Penreco, Butler, Pa.) was added to 100 .mu.l of T150R1. This mixture of biologically active copolymer and oil was homogenized for two minutes in a homogenizer. Next, 1 ml of PBS with 2% Tween-80 was added and homogenized for another 2 minutes. Finally, an additional 1 ml of PBS with 2% Tween 80 was added and homogenized for 2 minutes. The control emulsion was prepared as above but without the addition of T150R1 copolymer.

All rats were injected with 100 .mu.l of either the control or the test emulsion. The test emulsion contained a total of 5mg of T150R1 copolymer. All injections were given subcutaneously on the dorsum of the neck. The effect of the compound on the activity of rats is shown in FIG. 5.

As shown FIG. 5, rats that were injected with the biologically active copolymer of the present invention demonstrated markedly increased activity over the control.

The effects of the biologically-active copolymer of the present invention on a human leukemic cell line were evaluated. The biologically-active copolymer (T150R1) tested had the following formula: ##STR13## wherein: The mean molecular weight of the hydrophobe portion of the octablock copolymer represented by polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is approximately 6750 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes approximately 10% of the compound by weight; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes approximately 90% of the compound by weight.

This biologically active copolymer is designated T150R1.

The effects of the biologically active copolymer T150R1 of the present invention on malignant human cells were evaluated by incubating various doses of the copolymer with K562 acute myeloblastic leukemia cells or HL-60 promyelocytic leukemia cells and determining viable cell numbers by the trypan-blue exclusion method and cellular proliferation as measured by incorporation of .sup.3 H-thymidine into DNA after two days of culture in CEM medium containing 5% fetal calf serum. The results are shown in FIGS. 6 and 7.

FIG. 6 shows that the biologically-active copolymer of the present invention was highly toxic to HL-60 cells, but only minimally affected the viability of K-562 cells. With a dose of biologically-active copolymer of 10 .mu.g per 10.sup.5 cells, the viability of HL-60 cells decreased to less than 35% that of control cells incubated with medium only. With 30 .mu.gB 10.sup.5 cells of biologically-active copolymer, over 90% of the cells were killed. In contrast, over 80% of the K-562 cells were alive with the 10 .mu.g dose and over 70% of the K-562 cells were alive with the 30 .mu.g dose of biologically-active copolymer.

As shown in FIG. 7, the biologically-active copolymer of the present invention strikingly inhibited DNA synthesis by both HL-60 and K562. The HL-60 was more greatly affected than the K562 cell line. However, with the 30 .mu.g dose at which greater than 70% of the K562 cells in the culture were alive, DNA synthesis by these cells was inhibited greater than 85%.

Thus, the biologically-active copolymer of the present invention showed both cytotoxic and cytostatic effects against two human leukemia cell lines. The fact that HL-60 was much more susceptible than was K562 shows that the copolymer was selective for the HL-60.

FIG. 8 shows the results of differential effect of the biologically active copolymers of the present invention on two different cell lines. In addition to the biologically-active copolymer T150R1 tested in Example 7.11, T130R1 represented by the following formula: ##STR14## wherein: The mean molecular weight of the hydrophobe portion of the octablock copolymer represented by polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) is approximately 5750 daltons;

a is a number such that the hydrophile portion represented by polyoxyethylene (C.sub.2 H.sub.4 O).sub.a (POE) constitutes approximately 10% of the compound by weight; and

b is a number such that the polyoxypropylene (C.sub.3 H.sub.6 O).sub.b (POP) portion of the octablock copolymer constitutes approximately 90% of the compound by weight.

Cell cultures were incubated with various concentrations of the two copolymers. After 24 hours of incubation, the level of lactic dehydrogenase (LDH) was measured in the supernatant and compared to the total LDH in untreated cells. The release of LDH into the surrounding medium is a measure of cell death. As shown in FIG. 8, the two cell lines responded very differently to the two drugs.

Thus, the tumoricidal compound of the present invention showed both cytotoxic effects against two human leukemia cell lines. HL-60 cell line was more sensitive to the T150R1 while the K-562 was much more sensitive to the T150R2 copolymer.

The effects of low concentrations of octablock copolymer T130R2 were determined on the HL-60 cell lines. T130R2 octablock copolymer causes inhibition of the proliferation and retards DNA synthesis over time. T130R2 causes cell lysis at concentrations greater than 10 .mu.g/ml after a 24 hour incubation. However, at lower concentrations, T130R2 causes a dose dependent increase in cell adherence starting at a concentration of approximately 1 .mu.g/ml to a concentration of approximately 30 .mu.g/ml. After 24 hours of incubation, over 50% of the normally nonadherent HL-60 cells are adherent. The data indicate that the HL-60 cells differentiate when exposed to the T130R2 copolymer. The evidence that supports this observation is as follows: (a) An incubation of at least 2 days was required to arrest growth; (b) T130R2-treatment caused cells to adhere to the bottom of the plate, which is an indication of differentiation into monocytic cells; (c) cell-cycle analysis showed two levels of blockade, namely, G0+G1-S and G2+M-G0-G 1 phases of cell-cycle.

In an experiment to investigate the effects of T150R1 on antibody production, groups of four mice were administered the antigen, bovine serum albumin, in an oil-in-water emulsion with or without T150R1. The mice were challenged 14 days later with BSA plus an adjuvant and the antibody response to the antigen was measured at 1, 2, and 3 weeks. As shown in FIG. 9, antibody tilers in the T150R1 treated animals were less than 1000:1 at all three time points whereas the control mice displayed increasing titers with an average titer greater than 4000:1 at three weeks following challenge.

In another experiment, mice were administered BSA in an oil-in-water emulsion with or without T150R1 as in the above experiment. Mice were sacrificed 14 days later. Thymus and spleen were removed and single cell suspensions of thymus or spleen were administered intravenously to syngenic recipient mice. Mice were challenged at the same time with BSA in an oil-in-water emulsion with adjuvant. Titers to the BSA were measured at 1, 2, and 3 weeks. These results are shown in FIG. 10.

As shown in FIG. 10, mice receiving thymus cells had titers below 1000:1 at all three time points. Those receiving spleen cells had titers below 1000:1 at 1 and 2 weeks and below 3500:1 at 3 weeks. Control mice which did not receive thymus or spleen cells had steadily increasing titers which at three weeks averaged greater than 4000:1. This experiment demonstrates adoptive transfer of immunosuppression with spleen and thymus cells.

The effect of T150R1 on the progression of experimental allergic encephalomyelitis (EAE), a well characterized animal model of multiple sclerosis, has been studied. In this animal model EAE is induced by injecting myelin basic protein (MBP), a component of the sheath covering certain nerves, in combination with complete Freund's adjuvant (CFA), a potent adjuvant, into Lewis rats, a strain particularly prone to developing autoimmune disease. Over a two week period following injection, the rats develop an ascending flaccid paralysis and characteristic lesions of the central nervous system. In a study designed to investigate T150S1, rats were injected with MBP-CFA with or without T150S1. Animals receiving MBP-CFA developed signs typical of EAE. The T150R1 rats, however, showed no evidence of paralysis. All rats were sacrificed at day 13 following injection, the thymuses were removed and single cell suspensions were made and cells were counted. As shown in FIG. 11, the thymus of T150R1 treated rats contained over 40 times the number of cells as the MBP-CFA only treated rats. As an additional control, the response to hen egg albumin injected with CFA and T150R1 was evaluated. These rats also had a greatly increased number of cells in the thymus.

The proliferative activity of thymus cells from T150R1 treated rats, as measured by tritiated thymidine uptake, was also markedly increased over the MBP-CFA animals. The in vitro response to challenge with MBP was also evaluated by measuring tritiated thymidine uptake. In this experiment, T150R1-MBP-CFA treated animals demonstrated higher levels of activity than the MBP-CFA treated animals at 24 hours (See FIG. 12). However, at 72 and 96 hours T150R1 treated animals had negligible thymidine incorporation while the MBP-CFA rats maintained levels of incorporation comparable to the 24 hour value.

Although not wanting to be bound by the following theory, it is believed the increased cellularity in the thymus is due to thymic stimulation with the dominant response being stimulation of specific suppressor cells. The ability to induce a specific suppressor cell response has implications for those diseases or conditions in which a specific tolerant state is desired.

Chickens are treated subcutaneously at one day of age with an oil-in-water emulsion of the copolymer T150R1. A 2.5 mg dose of the copolymer is administered. Relative bursal weights at 1, 3, and 6 weeks of age are determined and the results are set forth in Table G. A comparison is made of chickens treated with the polymer in the oil-in-water emulsion against chickens treated with the oil-in-water vehicle only. No difference in bursal weight is found at I week of age. Male and female chickens treated with the polymer have significantly smaller bursae at 3 weeks of age than chickens injected with the vehicle alone. At 6 weeks of age, there is no difference in bursal weights of the treated and untreated female chickens, but the difference in males is more pronounced. In fact, many of the male birds have effete bursae at 6 weeks. It is known in the art that testosterone and its analogs cause bursal atrophy which probably is due to enhanced B cell emigration. The pronounced effect on bursal weights in males in this experiment may be due to an additive effect of testosterone which reaches significant levels around the fourth week of age.

Antibody assays are done with sera collected from the treated chickens by commercial ELISA tests. It can be concluded from these tests that bursal atrophy is not caused by adventitial infection with infectious bursal disease virus as representative serum samples do not have measurable levels of antibodies to it, or to other common viruses of poultry. The observed results therefore are most likely the result of treatment with T150R1.

Chickens are treated subcutaneously at one day of age with an oil-in-water emulsion of the copolymer T150R1. The doses administered contain 1.0, 2.5 and 5.0 mg of the copolymer.

Morphometric data concerning the bursae of the treated birds are collected by using a SONY.RTM. television camera mounted on a light microscope to project images of tissue sections of bursae on a smooth surface. An electronic stylus is used to circumscribe bursal follicles along their outer perimeters and to trace the outer and inner (medullary) margins of the interfollicular epithelium (IFE). The stylus is coupled to an Apple IIe computer which employs a program to convert the electronic signals to square inches of area inscribed. A metric grid is projected and measured with the stylus in order to convert square inches to .mu.m.sup.2. The cortical area is defined as the difference between follicular area and the area inscribed by the outer margin of the interfollicular epithelium. The area of the interfollicular epithelium is defined as the difference between the medullary area and the area inscribed by the outer margin of the interfollicular epithelium. Twenty-five contiguous lymphoid follicles are measured in each bursa and the coefficient of variance (CV) of these measurements range from 10-35%. Each group analyzed has 20 chickens. The CV for the 20 observations ranges from 5-15%. The data collected at three days, one week, two weeks, and three weeks after treatment are presented in Tables H-K.

At three days of age, the medullae of chicks treated with 1.0 and 2.5 mg T150R1 are larger than medullae of the controls. This enlargement is also reflected in the cortico-medullary (C) ratios. Although the medullae tend to be smaller and the cortices larger in treated birds than in controls at 1 week of age, these trends are not statistically significant until they are considered together in the cortico-medullary ratios. Because the follicles of chickens treated with 1.0 mg T150T1 are unusually small at two weeks (as shown in Table J), a direct comparison with the other dosage groups is risky. Nevertheless, at two weeks the cortico-medullary ratio is higher than controls and not different from birds treated with 2.5 mg of the copolymer. At three weeks, the cortico-medullary ratio of birds treated with 2.5 mg T150R1 are greater than controls, but the difference is not as great and the previous perturbation in bursal development probably is subsiding. Although a few differences are observed in areas of the interfollicular epithelium, no pattern can be discerned and these differences are considered inconsequential. As shown in Tables I, J, and K, the 5.0 mg dose appears to be less effective than the 2.5 mg dose. Apparently a dose containing 1.0 mg or 2.5 mg of the copolymer T150R1 accelerates the maturation of the bursa of Fabricius.

Accordingly, precocious maturation of bursae should lead to more rapid growth of medullae which should begin to regress early. Early migration of medullary cells to the cortices should result in more rapid expansion of cortices than normal. As the cortical lymphocytes mature and migrate to the spleen, bursal involution should occur at an earlier age, and be evident in males earlier than females. These are the changes observed.

Chickens treated with 1.0 mg of the copolymer T150R1 in an oil-in-water emulsion at one day of age are immunized at one and two weeks with sheep red blood cells (SRBC) and killed Brucella abortus (BA) to elicit primary and secondary antibody responses, as described by the method of Bhanushali et al., (See Bhanushali, J. K., K. K. Murthy and W. L. Ragland, The effects of in ovo mibolerone treatment on the bursa of Fabricius and the humoral immune system of chickens: A dose-response study. Immunopharmacology 10:99-110, 1985) which is incorporated by reference herein. Results of an experiment with 20 chickens per group are shown in Table L. Most of the birds demonstrate no measurable primary response to either antigen. The total Ig response, but not the IgG secondary response, to sheep red blood cells is significantly higher in chickens which have been treated with a dose containing 1.0 mg T150R1 than in the other three groups. Secondary responses to Brucella abortus in treated birds are not different from birds injected with the vehicle alone.

In a subsequent immunization experiment, 40 chickens are treated with 1.0 mg T150R1 and 40 with the vehicle. The data are shown in Table M. The total secondary Ig responses to both Brucella abortus and sheep red blood cells are significantly increased but there is no significant effect on class switching to IgG, i.e., the effect is only on IgM.

In the first above-described experiment involving immunized chickens, heparinized blood is collected and buffy coats are prepared for blastogenic tests. Proliferation of lymphocytes stimulated with phytahemagglutinin and concanavalin A are not different from vehicle controls suggesting that the polymer has little effect in cell-mediated responses in chickens. Data are not shown.

It should be understood., of course, that the foregoing relates only to a preferred embodiment of the present invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.

Biologically active polymers of the present invention are administered to animals to reduce the number of enteric microorganisms in the gut of the animal. Preferred copolymers for reducing enteric microorganisms include T110R1, T130R2 and T150R1, described above in Table A. The preferred animal to treat with the biologically active copolymers of the present invention are poultry animals for the reduction of Salmonella.

A protocol for evaluation of effect of copolymer T150R1 on Salmonella of broiler chickens is described below.

Feed:

Standard unmedicated broiler starter ration supplied by the University of Georgia feed mill (UGA Broiler Starter), described in Table O, was used. Feed contained either zero or 10 ppm T150R1. The premix of copolymer supplied by CytRx was mixed for 15 minutes in a commercial type cement mixer. Chicks were given the appropriate feed ad libitum.

Reagents:

T150R1

Mazola corn oil

Hodgson Mill plain yellow corn meal (not enriched)

Premix Preparation:

Refer to Table N for weights of ingredients at each concentration; record lot numbers used.

1. Weigh corn oil into clean, tared mixing bowl on balance

2. Add T150R1 by weight, using all plastic syringe for small additions

3. Move bowl to mixer and beat corn oil/polymer mixture on speed 2 or 3 minutes, use splash guard on bowl

4. Weight cornmeal into tared 4 L beaker during mixing time

5. Reduce mixer speed to 1, add approximately 100 g cornmeal (from 4.) to mixture, beating 1 minute after addition

6. Repeat (5.) 4 times more

7. Stop mixer and scrape bowl and beater

8. With mixer at speed 1, add approximately 100 g cornmeal (from 4.) to mixture, beating 30 seconds after each addition

9. Repeat 4 times more

10. Stop mixer and scrape beater

11. Return mixer to speed 1, gradually add remaining cornmeal, over a 2 minute time span

12. Increase mixer to speed 2 and beat for 10 minutes more

13. Transfer to labeled ziplock bags for storage

14. Store at 4.degree. C.

15. Mix one pound premix with one ton of feed

Salmonella:

A .lambda. nalidixic acid resistant strain of S. typhimurium previously isolated from chickens was inoculated onto a slant of BG sulfa agar with 200 ppm added nalidixic acid and incubated for 24 hours. The slant was then washed with sterile saline and the resulting suspension used to generate a stock culture that was compared to a standard optical density curve to determine the concentration of Salmonella. 0.5 ml of the appropriate dilution of Salmonella was then lavaged into the crop of a chick on the indicated day.

Sampling:

On the indicated kill day, chicks were killed by cervical disarticulation and the ceca aseptically removed and sampled for Salmonella according to the standard protocol as follows.

Russell Research Center Salmonella Method

1. Preenrich initial sample (25 gram feed; chick ceca; chicken carcass rinse) in buffered peptone (BP) water (nine times the sample weight) and incubate for 24 hours at 35.degree.-37.degree. C.

2. Transfer 0.1 mL of BP into 9.9 mL tube or TT broth (Difco, Detroit, Mich.) and incubate for 24 hours at 42.degree. C.

3. From the TT, streak for isolation onto BG Sulfa and Modified Lysine Iron Agar (MLIA) plates and incubate for 24 hours at 35.degree.-37.degree. C.

4. Pick suspect Salmonella colonies from plates onto lysine from agar slants and incubate 24 hours at 35.degree.-37.degree. C.

5. Confirm Salmonella with flagellar (H) serology.

Experiments comparing the effects on Salmonella of the copolymer mixed in chicken were conducted according to the following protocol of inoculation and incubation.

The results of these experiments are presented in Tables 1-3.

The primary objective of Example XXI was to evaluate test compound T150R1, which has hydrophobe molecular weight of 6750, and percentage of hydrophile of 10%, alone and in combination with acetic acid, with regard to interference with Salmonella enteritidis recognition and binding to processed chicken skin and muscle tissue. Specifically, the aim of this study was to determine the optimal concentration of T150RI for prevention of Salmonella enteritidis (phage type 13A) attachment to chicken skin and meat and to determine whether or not additive or synergistic effects would occur when T150RI was combined with acetic acid using a sensitive assay system.

Test Substance:

T150RI was used for these studies (as provided by Shotwell & Carr, Inc.). Mallinckrodt glacial acetic acid, obtained through Baxter Health Care Corporation, Scientific Products Division, was also used for these investigations. Distilled water was obtained through the use of a MilliQ-UF Plus water purification system.

Identification

CytRx compound: T150RI

Lot #: 120-11

Quantity Received: 627.3 g

Date of Manufacture: May 24, 1993

Glacial acetic acid

Lot #: 3532

Baxter Catalog #2504

Original Quantity Received: 2.23 Kg

Distilled Water

Relative Purity: measured at a flow resistance at least 16.0M ohms per cm.

Concentration and Administration

An initial concentration of 40 parts per million (ppm) T150RI was made in distilled water. This was performed by serial dilution as follows. Four mL of T150RI was added to 6mL of sterile distilled water and completely mixed by vortex. One mL of this dilution was completely mixed with 99 mL of sterile distilled water, resulting in 0.004 mL T150RI/mL of solution (equivalent to 4000 ppm). One mL of this dilution (4000 ppm) was completely mixed with an additional 99 mL of sterile distilled water, resulting in 0.00004 mL T150RI/mL of solution (equivalent to 40 ppm). This solution was hereafter referred to as the "stock solution."

The selected final concentrations for evaluation included 10, 1.0, 0.1 and 0.01 ppm T150RI. Prior to experiment implementation, the stock solution (40 ppm) was serially diluted by 10-fold dilutions (1 mL stock solution+9 mL of sterile distilled water) to achieve concentrations of 4.0, 0.4 and 0.04 ppm. As described below, 500 uL of the stock and each of these test concentrations was combined with 1,500 uL of culture vehicle containing skin or muscle tissue and radiolabeled Salmonella enteritidis, resulting in a 4-fold dilution in each case. Thus the final concentrations to which the tissues were exposed consisted of 10, 1.0, 0.1 and 0.01 ppm.

Dilutions of acetic acid were performed as follows: 200 mM acetic acid was obtained by combining 1 mL of glacial acetic acid (17.4M) with 86 mL of distilled water and thoroughly mixing. This solution (200 mM) then underwent a four-fold dilution in each test vial, as described below, to obtain a final concentration of 50 mM and served as the positive control for these experiments.

In parallel to these dilutions of T150RI alone, each concentration of test compound was combined with 50 mM (final concentration) acetic acid. In this case, 500 uL of the final incubation volume (2000 uL) was substituted with 200 mM acetic acid. This resulted in a four-fold dilution to a concentration of 50 mM. Acetic acid alone (50 mM) served as a positive control.

Test System

The ability to screen compounds potentially capable of altering or interfering with the attachment of bacteria to raw poultry skin and muscle provided the fundamental basis for the previous development of the test system which was used for these experiments. Skin and muscle samples from commercially processed broiler chickens, placed in a specially designed culture system with viable Salmonella enteritidis, provided information relative to the potential efficacy of the test articles for the exclusion of Salmonella enteritidis from broiler carcasses in commercial processing plants.

The test system utilizes a technique referred to as competitive binding. When live virulent Salmonella enteritidis are incubated with isolated skin or muscle samples, the organisms bind to the tissues in a time-related manner. By adding the test articles in the concentrations listed above, the ability of the test articles to interfere with this specific binding phenomenon was evaluated.

Skin and Muscle Tissue Source

In a typical commercial broiler chicken processing plant, the animals are killed and then placed in a vat of hot water (53.degree.-63.degree. C.) for a brief period of time to loosen the feathers (a process known as "scalding"). The carcasses are then eviscerated, inspected, and dumped into a common vat of cold (.about.10.degree. C.) water to rapidly chill the carcasses. It is at this step that much of the contamination of broiler carcasses occurs since even a few salmonella contaminated carcasses may contaminate the entire lot. It may be useful to note that a typical broiler processing plant will process 70,000-120,000 broiler chickens per day.

For the present experiments, commercially processed broiler chicken carcasses were obtained from a processing plant (post-chill) in Seguin, Tex., with which our laboratory has a working relationship (Tyson Foods). Whole carcasses were maintained and transported on wet ice to the laboratory for use in skin studies within 24 hours of slaughter and for use in meat studies within 48 hours of slaughter.

Isolation Procedure

Skin from the pectoral region was removed from the chicken carcasses and tightly stretched on a sterilized wood platform. Using a double-bladed scalpel apparatus developed in our laboratory, consisting of two blades separated by 0.71 cm, 0.5 cm.sup.2 samples were cut from the skin. Samples were retained in a glass beaker on wet ice until use in the assay. Six 0.5 cm.sup.2 skin samples were then placed in a 7 mL plastic scintillation vial (Kimble, Fisher Scientific) containing 1.3 mL sterile distilled water for use in the experiments with the following exception: treatment groups consisting of both 50 mM acetic acid and the various concentrations of the test compound contained 0.8 mL distilled water to accommodate the additional 0.5 mL of 200 mM acetic acid (added at the time of test compound addition).

Muscle samples were obtained from the pectoralis major and pectoralis minor. The skin was removed and cores of muscle tissue were obtained using a 6 mM diameter surgical biopsy punch (Weck #866810, Princeton, N.J.) and held in distilled water in a glass beaker on wet ice until use in the assay. Two 1.5 cm core segments (to provide approximately 6.8 cm.sup.2 of surface area) were placed in each 7 mL plastic scintillation vial containing 1.3 or 0.8 mL distilled water for use in these experiments (as described above for skin samples).

Culture Technique

Immediately following addition of the skin or muscle samples to the scintillation vials, 500 uL of either 40, 4.0, 0.4, or 0.04 ppm of T150RI was added and mixed by gentle vortexing. Additionally, 500 uL of distilled water (negative controls) or 500 uL of acetic acid was added to appropriate vials prior to mixing. The final volume of each vial, prior to addition of Salmonella enteritidis, totaled 1,800 uL. To each vial, 200 uL of a suspension of 5.times.10.sup.8 radiolabeled Salmonella enteritidis phage type 13A was added. Sample vials were then incubated at 10.degree. C. for 1 hour. All incubations were carried out using gentle horizontal rocking (30 oscillations/minute, Eberbach #122, Ann Arbor, Mich.).

Following the incubation period within each experiment, the incubation medium, containing free Salmonella enteritidis and treatment material, was aspirated from each vial using a glass Pasteur pipette attached to a vacuum apparatus. Two mL of sterile distilled water was then added to each vial and again removed by aspiration. This process was repeated twice more to remove residual unbound Salmonella enteritidis.

Following washing of the tissue samples with distilled water, 2.0 mL of tissue digestion cocktail (Scintigest, Fisher Scientific) was added. This mixture was allowed to incubate overnight at 60.degree. C. Following this incubation, 3 mL of scintillation cocktail (Ultima Gold, Packard Instrument Company, Downers Grove, Ill.) was added to the vials and mixed using a vortex apparatus. The vials were stored in darkness overnight prior to determination of disintegrations per minute (DPM) in a commercial scintillation counter (Packard Instrument Company, model #B4430, Downers Grove, Ill.).

Salmonella Source and Radiolabel

A primary poultry isolate of Salmonella enteritidis phage type 13 A was obtained from the United States Department of Agriculture National Veterinary Services Laboratory for use. Numerous studies from our laboratory have been published in which this isolate was used for challenge of live chickens and it clearly has substantial infectivity and virulence (10-13). This isolate has been aliquoted and is stored at -70.degree. C. For use in these studies, a 100 uL aliquot was thawed (containing approximately 1.times.10.sup.6 viable organisms) and placed in 10 mL of tryptic soy broth (Difco). This tube was incubated for 7 hours at 37.degree. C. to allow establishment of rapid growth. Following this initial incubation, 100 uL of the Salmonella enteritidis in tryptic soy broth was inoculated into 10 mL of fresh tryptic soy broth and incubated for an additional 7 hours. This procedure was repeated for one additional 8-hour period during which the Salmonella enteritidis, then in log-phase growth, were incubated in 10 mL tryptic soy broth containing 100 uL .sup.3 H-thymidine (specific activity 6.7 Ci/mmol and 1 mCi/mL, ICN, Irvine, Calif.) and 40 uL .sup.3 H-adenine (specific activity 32 Ci/mmol and 1 mCi/mL, ICN, Irvine, Calif.). At the end of this 8-hour final incubation period, the Salmonella enteritidis were pelleted by centrifugation (3,000.times.G) for 15 minutes. The supernate was discarded and the pellet resuspended in distilled water. This procedure was repeated twice more to remove free .sup.3 H-thymidine and .sup.3 H-adenine. Following the final resuspension, the optical density of the suspension was determined using a spectrophotometer (Milton Roy #20-D, Rochester, N.Y.). The concentration of Salmonella enteritidis in the suspension was determined by comparing the optical density with a standard curve. This standard curve was generated by determining the optical density of serial dilutions of a stock suspension of Salmonella enteritidis in log-phase growth and determining the number of viable Salmonella enteritidis/mL by simultaneous quantitative spread plate culture and colony counting. Generation of the standard curve required graphic plotting of the number of determined organisms on one axis vs. the optical density of each concentration on the alternative axis. This standard curve has been re-validated in our laboratory three times. The suspension was then diluted to 1.times.10.sup.9 Salmonella enteritidis/mL based on the spectrophotometrically determined concentration. The bacteria were re-pelleted by centrifugation (3,000.times.G) and quantitatively resuspended in cell culture medium. Finally, by comparing the known concentration of Salmonella enteritidis with the disintegrations/minute (DPM) of a 50 uL aliquot of the suspension, as determined by scintillation counting (Packard Instrument Company, model #B4430, Downers Grove, Ill.), the specific activity (DPM/cell) was calculated. By comparing the DPMs determined from assay of the culture vials, the number of Salmonella enteritidis bound to the skin or muscle samples were calculated.

Treatment Groups and Replicates

Each concentration of T150RI (10, 1.0, 0.1, and 0.01 ppm) was evaluated in 6 replicate vials at 10.degree. C. with each concentration of T150RI used alone or in combination with 50 mM acetic acid. Negative control consisted of 6 vials containing only distilled water in place of the test compound (without T150RI). Positive control consisted of the addition of 500 uL of 50 mM acetic acid (without T150RI) as described above. Each of these treatment groups were used for skin and muscle samples in separate experiments.

Parameters/Effects Measured

Disintegrations per minute (DPM) of radiolabeled Salmonella enteritidis bound to skin and muscle samples following washing were determined, using standard scintillation counting technique. Briefly, to the washed skin and muscle tissues, representing the radioactivity of the bound to the tissues in each standard 7 mL plastic scintillation vial (Kimble, Fisher Scientific), 2.0 mL of a tissue digestion cocktail (Scintigest, Fisher Scientific) were added to each vial to dissolve the tissues. This mixture was allowed to incubate overnight at 60.degree. C. Following this incubation, 3 mL of scintillation cocktail (Ultima Gold, Packard Instrument Company, Downers Grove, Ill.) was added to the vials and mixed using a vortex apparatus. The vials were incubated in darkness at room temperature overnight before radiation determination. The vials were then placed in a scintillation counter (Packard Instrument Company, model #B4430, Downers Grove, Ill.) and DPM determined during a two-minute counting period for each vial. The number of bacteria bound to the tissues was then determined for each vial by dividing the sample DPM by the specific activity (DPM/bacterial cell). Determination of the specific activity of individual salmonellae was described above.

Statistical Evaluation of Results

The mean number of Salmonella enteritis bound was compared between all treatment groups. Statistical analysis was performed between each treatment group using Analysis of Variance and significant differences were separated using Duncan's Multiple Range Test (SAS Institute, Cary, N.C.). This comparison readily allowed for the interpretation of T150RI mediated effects on inhibition of Salmonella enteritidis binding to skin and muscle samples. Furthermore, comparison between the efficacy of each concentration of T150RI alone, each concentration of T150RI with 50 mM acetic acid, 50 mM acetic acid alone (positive control) and distilled water along (negative control) was made.

Results

Discussion of Results

Skin Results

Inclusion of the test compound T150RI alone over the entire range of concentrations evaluated caused reduced Salmonella enteritidis binding to skin tissue in the present experiment. This reduction ranged from 47.7% of the control values to 63.8% of control values and was observed to be statistically significant at concentrations of 10, 0.1, and 0.01 ppm (Table 1 ). Inclusion of acetic acid (50 mM) alone did not reduce Salmonella enteritidis binding to chicken skin and did not enhance the efficacy of T150RI for the prevention of attachment to skin in the present experiment (Table 1).

Meat Results

Similarly, inclusion of T150R1 alone at the highest concentration evaluated, 10 ppm, significantly reduced Salmonella enteritidis attachment to meat samples in the present experiment (Table 2). However, lower concentrations of T150RI alone did not significantly affect Salmonella enteritidis binding to meat issue. In contrast to the results of the skin binding experiment discussed above, the inclusion of acetic acid (50 mM) alone caused a significant reduction in Salmonella enteritidis binding to chicken meat. When 50 mM acetic acid was combined with T150RI, a significant reduction in Salmonella enteritidis binding to the meat samples was observed at each concentration T150RI evaluated (0.01-10 ppm, Table 2). The reduction in Salmonella enteritidis binding to chicken meat mediated by the combination of T150RI and 50 mM acetic acid ranged from 58.8% (1 ppm T150RI) to 64% (0.01 ppm T150RI) of control values (Table 2).

Discussion

The ability of T150RI alone to reduce Salmonella enteritidis binding to either meat or skin by approximately 50% at concentrations as low as 10 ppm is certainly encouraging. At this concentration, the test compound T150RI appears to be colloidal due to the milk-like appearance of the dilution in water. Casual observation by the investigators over several days indicated that T150RI apparently separated from the aqueous vehicle. One question that must be considered relates to the concentration of T150RI that is actually in solution and not simply in suspension. Indeed, if the bioactive form causing the reduced Salmonella enteritidis binding to meat and skin were the soluble compound, there may only be a fraction of the 10 ppm dilution that is actually available for interference with bacterial attachment to the meat and skin. Future evaluations may be appropriately directed toward increasing the true solubility of the test compound and determination of the relative efficacy of soluble T150RI. The test compound T150RI more rapidly forms a homogenous suspension when diluted in 50 mM acetic acid than when diluted in distilled water, and further, increased acidification with acetic acid apparently completely dissolves the test compound as the opacity of the suspension clarifies. However, the efficacy of this type of dilution was not evaluated in the present experiments. Indeed, the present experiments were implemented to evaluate the separate addition of acetic acid and the aqueous suspension of T150RI.

It should be understood, of course, that the foregoing relates only to a preferred embodiment of the present invention and that numerous modifications or alterations may be made therein without departing from the spirit and the scope of the invention as set forth in the appended claims.