Method for Prophylactic Treatment of the Colonization of a Staphylococcus Aureus Bacterial Strain by Bacterial Cell Surface Protein With Fibronectin and Fibrinogen Binding Ability

The present invention relates to a cell surface protein having an ability of binding to fibronectin, fibrinogen, collagen, and/or laminin, process for its preparation, as well as the use of such a cell surface protein.

The object of the present invention is to obtain a possibility of blocking fibronectin, fibrinogen, collagen, and/or laminin in a traumatic wound tissue in order to prevent adherence of pathogenic bacterial strains on fibronectin, fibrinogen, collagen, and/or laminin.

Staphylococci and streptococci are usually often regarded as a group of gram positive bacteria, which develops purulent matter (pus) at infections, so called pathogenic cocci. This group does not only contain the classical Staphylococcus aureus and Streptococcus pyogenes (group A streptococcus), but also other staphylococci and streptococci, such as Staphylococcus epidermis, Staphylococcus haemolyticus, Staphylococcus hyicus, streptococci of Groups B, C, G, and H, viridans streptococci, etc. Even gram negative bacteria such as Escherichia coli can cause such infections.

These pathogenic bacterial strains causes different infections in man and in animals all the way from small selfhealing skin infections, to serious sepsis (blood infection). At the infection of animals by these strains the animals are not only suffering, but also great economical damages are caused to the owners of the animals due to production cut-off. Mastitis in milking cows is such an economically damaging infection.

In man such bacterial strains cause i.a. heart valve infections, but also other infections as the commonly known "hospital illness", i.e., most often an infection of an open wound, which shows difficulties in healing, can produce large amounts of pus, and can cause reoperation. Particularly, the heart valve infections threatens risk groups already exposed within the hospital care.

The term wound used means that normally covering epithelial cellular layer, and other surface structures have been damaged by mechanical, chemical, or other influence. The term wound can hereby be divided into two main groups, viz: surface wounds, and deep wounds. The term surface wound means a trauma on the surface of the body or a surface in direct connection to the cavities of the body, i.e., the gastro-intestinal duct, mouth cavity, urethra, milk ducts, etc. The term deep wounds means trauma in the inner of a body caused by violent outer assault or by surgical incisions in different tissues.

When a wound is caused, fibronectin, fibrinogen, collagen, and/or laminin are exposed in the wound tissue. These proteins form together with so called proteoglucans a net work structure in different reinforcement tissues, and is the structure onto which connective tissue (fibroblasts) and epithelial cells grow at a natural wound healing.

The natural wound healing can, however, be prevented by pathogenic bacteria colonizing therein, primarily by pyogenic cocci, and secondly by other pathogenic strains, such as E. coli and other gram negative rod shaped bacteria.

Examples of such a colonizing of damaged tissue are:

i) colonizing of wounds in skin and connective tissue, which wounds have been caused by a mechanical violence, chemical damage, and/or thermal damage;

ii) colonizing of wounds on mucuous membranes, such as in the mouth cavity, or in the mammalian glands, urethra, or vagina;

iii) colonizing on connective tissue proteins, which have been exposed by a minimal tissue damage (microlesion) in connection with epithelial and endothelial (mastitis, heart valve infection).

It has now surprisingly been shown possible to isolate proteins from bacterial cell surfaces, which proteins adhere to fibronectin, fibrinogen, collagen and/or laminin, which cell surface proteins are derived from bacterial strains mentioned above.

Such cell surface proteins can thereby be used for the treatment of wounds, e.g., for blocking protein receptors or for immunization (vaccination). In the latter case the body creates specific antibodies, which can protect against invasion of bacterial strains comprising such a cell surface protein. Hereby the antibodies block the adherence of the bacterial strains to a damaged tissue.

The characteristics of the present invention are evident from the accompanying claims.

By means of the present invention it is thus achieved that pathogenic bacterial strains can be effectively prevented from colonizing a traumatic wound tissue.

When using the present cell surface proteins for the purpose of immunization (vaccination) in mammals including man, the protein is dispersed in a sterile, isotonic saline solution, optionally while adding a pharmaceutically acceptable dispersing agent.

A suitable dosage to obtain immunization is 0.5 to 4/.mu.g of cell surface proteins per kg body weight and injection of immunization. In order to obtain a durable immunization, vaccination should be carried out on three consecutive occasions with an interval of 1 to 3 weeks. Furthermore, one carries out the immunization in accordance with science and tested practice.

When using the present cell surface proteins for topical, local application the protein is dispersed in an isotonic saline solution to a concentration of 25 to 200/.mu.g per ml. The wounds are then treated with such an amount only to obtain a complete wetting of the wound surface. For an average wound thus only a couple of milliliters of solution are used in this way. After treatment using the protein solution the wounds are suitably washed with isotonic saline solution or another suitable wound treatment solution.

Below, an immunization of young cows against mastitis is shown. Topical use of cell surface protein can also be used for preventing mastitis by treating udders/teats with a solution comprising cell surface proteins, which prevents pathogenic, mastitis-inducing organisms to adhere thereto.

In accordance with the invention a mixture of cell surface proteins with different binding properties can be used, particularly if the binding properties of an infecting, bacterial strain are unknown, and there is a great demand for a rapid prevention of a massive bacterial epidemic infection; or the infection is caused by a mixture of bacteria.

The invention will be described more in detail in the following with reference to some Examples.

A strain of Staphylococcus aureus, which binds to fibronectin was grown on a liquid medium (TS-broth), trypticase-soya-extract (Oxoid, Ltd., England).

After finished growth the bacteria were isolated by centrifugation and were washed with a saline solution (0.9% NaCl in water). The bacteria were then decomposed using a bacteriolytic enzyme (Lysostaphin.RTM., Sigma, 5 mg/liter of cell culture). Fibronectin binding components were isolated by affinity chromatography on immobilized fibronectin bound to a dextran gel (Sepharose, CL-4B, cyanobromide activated). The fibronectin binding components were then eluated by adding chaotropic ions (e.g. NaSCN, KSCN) in an aqueous solution. The eluation can also be carried out using an acidic solution, acetic acid solution having pH<3.

Fibronectin binding components consisting of proteins having their molecular weights within the range of 11,000 to 165,000, preferably 40,000 to 165,000 were isolated. The proteins may comprise a carbohydrate residue, whereby, however, it is the protein residue which is fibronectin binding, which is shown by the fact that the effect is totally eliminated after a treatment using protease, or heating to 80.degree. to 100.degree. C.

The amino acid composition of the protein components obtained is evident from the Table below:

In the Example the affinity chromatography has been used for purification/isolation of the protein. Other biochemical separation methods are ion exchange chromatography, and molecular sieve; electrophoresis incl. isotacophoresis; electrofocusing.

A conventional cultivation of S. aureus gives a cell surface protein of the above. For an efficient industrial production of receptors for vaccine, and other care the gen needs to be cloned in a suitable organism in order to obtain high yields.

A purified fibronectin binding cell surface protein has proved to be immunogenous at the immunization of rabbit and ruminants, and has thereby developed formation of antibodies.

Vaccination of SRB-heifers (1:st calf cow) with a fibronectin binding protein in accordance with the Example above.

Three SRB-heifers (Swedish Red-and-White Cattle) were vaccinated subcutaneously in the thorax region using 400 .mu.m of fibronectin binding component (M.sub.w 165,000 and 87,000). These injections were repeated twice with 14 days inbetween. Antibody determinations in serum and in milk by means of ELISA-method (Enzyme Linked Immuno Sorbent Assay) showed a very potent immuno response determinable in large dilutions of milk and serum already at the moment for the second immunization.

Two weeks after the second injection, i.e., at the moment for the third immunization injection the immuno response was regarded as stimulated enough to carry out an experimental udder infection (mastitis) in the three animals. These three animals, as well as two control animals from the same stock were exposed to an experimental udder infection using a strongly udder pathogenic strain isolated from acute bovine mastitis (S. aureus) in order to develop mastitis in the five animals. The test was carried out by washing, dispersing in an isotonic saline solution and then injecting into the teat and udder cavity using a standardized injection technique, 500 bacteria from a bacterial cultivation grown in a broth medium (TS-broth).

The following results were obtained:

i) very sparse growth in certain milk samples from vaccinated cows, only;

ii) very high number of bacteria in most milk samples from non-vaccinated animals;

iii) cell count determinations showed generally low cell counts in the vaccinated animals;

iv) cell count determinations showed generally high cell counts in the non-vaccinated animals;

v) the vaccinated animals produced unchanged volumes of milk;

vi) the non-vaccinated animals showed markedly decreased milking volumes (>10%);

vii) determination of acute phase reactants type "C reactive protein", and albumin in the vaccinated animals showed no change of the values obtained prior to the innoculation;

viii) determination of acute phase reactants type "C reactive protein", and albumin in the non-vaccinated animals showed strongly increased values.

The results obtained show that antibodies against fibronectin binding protein are secreted into udder and are present in local wound lesions in an amount enough to sterically prevent the surface receptors of an infecting bacterial strain to bind to exposed fibronectin in the udder tissue.

Blocking of an infection in an open skin wound by wound treatment using fibronectin binding cell surface protein from S. aureus.

Standardized wound damages (2.times.2 cm) were made on the back of pigs (20-25 kgs) using a so called dermatom. These wounds placed in two rows of 8 wounds on each side of the spine were subjected to a thermical damage (250.degree. C., 3 min). After thermal treatment the wounds were covered with a sterile bandage for 1.5 hrs, whereupon the wounds were infected with S. aureus strain (SA 113(83A)). Prior to bacterial infection the wounds on one side of the spine were treated with fibronectin binding cell surface protein, according to the Example above, solved in a sterile isotonic saline solution (100 .mu.g per ml of NaCl-solution). In wounds pretreated in this way the development of an infection was prevented by, at the same time, washing the wounds twice a day using a sterile isotonic saline solution. Non-treated wounds showed in the lesions, bad infections within 2 to 4 days although washing twice a day using NaCl-solution; infections which did not heal untreated with antibiotics during an observation period of one week. The results of this experiment show that surface exposed fibronectin is blocked by pretreating lesions using 100 .mu.g/ml in NaCl, in such a way that infections are prevented. Bacteria applied can easily be removed by rinsing which is impossible in wounds not treated with cell surface protein.

Besides fibronectin other connective tissue binding proteins have been detected in different microorganisms, which bind to those connective tissue structures present in man and animal, viz. collagen, and laminin according to the table below:

The binding of Staphylococci to immobilized fibronectin--a model to simulate binding to traumatic tissue (surgical wounds and mastitis).

A polymer surface was treated with different serum proteins, such as albumine and fibronectin. The polymer surface was then incubated with the respective protein dispersed in a sodium phosphate buffered saline solution (0.2M sodium phosphate, pH 7.4, and 0.145M NaCl) for 2 hrs at ambient temperature. The polymer surface was then dried by blowing air using a fan. Then the treated surface was subjected to a Staphylococci (strain SA 113(83A)) in a buffer solution, and dispersed in the presence of bovine milk, respectively. Already after a couple of minutes an uptake of bacteria was determined in both these testing systems, while a surface treated in the same way using albumin in the same, and in a 10-fold higher concentration of protein solution does not show an active bacterial uptake (untreated surface is however hydrophobic and binds staphylococci unspecific). The binding of strain SA 113(83A) can be inhibited by first incubating the bacteria with an antiserum obtained from rabbit vaccinated with a purified receptor protein.

In a similar way a surface has been treated with laminin, and then, as above, bacteria have been added, in this case a Group A streptococcus strain. Thereby it has been shown that the streptococcus strain binds to the surface.

A polymer surface was treated with fibronectin (immobilized) in accordance with Test 3 above. Then the surface was treated with a cell surface protein (M.sub.w 87,000) of Example 1 above solved in a physiologic saline solution, 100 .mu.g per ml. Then the surface was treated with a Staphylococci (strain SA 113(83A)) dispersed in a buffer solution (phosphate buffer, 0.2M Na-phosphate, pH 7.4, and 0.145 NaCl). After the treatment with staphylococci the polymer surface was rinsed with a physiological saline solution for eliminating loosely attached bacteria. At a subsequent analysis it was determined that no active binding of the staphylococci had taken place. The analysis was carried out by determining bacterial cell mass ATP (adenosine triphosphate) by means of bioluminescense technique. In short the analysis is carried out by incubating the polymer surface with 50 .mu.l of 1.25N trichloro acetic acid to extract cellular ATP. The amount of ATP is determined and compared with a standard curve for ATP in a Luminometer 1250 (LKB-Produkter, Bromma, Sweden).