Inactivation of Lipid Containing Viruses With Butylated Hydroxytoluene

This invention relates to new and useful improvements in the inactivation of lipid-containing viruses and more particularly seeks to provide an effective treatment of diseases caused by said viruses with butylated hydroxytoluene, hereinafter called BHT, having the well-known molecular structure: ##STR1##

In the late thirties and early forties, the medical community achieved a large measure of control over bacterial infections of animals with the discovery that sulfonamide and penicillin compounds of minor toxicity to a host would effectively inactivate or prevent the growth of many species of bacteria. Since that time, many other antibiotics have been found to control a wide spectrum of bacteria.

The smaller and more elusive viruses have proven more resistant to control by medical scientists. As a result, most viral-mediated diseases still remain without satisfactory medical treatments. Pathogenic viruses can be classified into two general types with respect to the viral structure, those that contain lipids and those that do not. Some well known lipid-containing pathogenic viruses are the pox viruses, the various herpes viruses, influenza viruses, C-type tumor viruses, and Newcastle's Disease virus. Many other pathogenic viruses do not contain lipids, e.g., polio and certain common colds.

Most agents currently in use or under investigation as chemical therapeutic agents against viruses operate on nucleic acid polymers. This type of treatment is medically disturbing due to the similarity of human nucleic acid polymers and those of infecting viruses. Genetic lesions may lead to resistant viral mutants and/or modified cellular DNA, either or both of which may have drastic long-term effects.

BHT is one of several antioxidants that are commonly added to foods to maintain freshness and prevent spoilage by oxidation processes. It is frequently added to dried cereals, cooking oils, canned goods, and various animal foods. It is on the Food and Drug Administration's GRAS (generally recognized as safe) list. In fact, the average daily intake of BHT in the United Stated has been estimated at 2 mg per person and it is accumulated in the body fat because it is not readily excreted.

Literature references report that BHT in large doses causes bile duct proliferation in mice, is toxic to developing insect larvae, and reduces the growth rate of cultured mammalian cells. Some individuals show chemical intolerance to BHT. On the other hand, data show that BHT reduces chemical carcinogenesis, protects against damage due to choline deficiency, protects against poisoning by carbon tetrachloride, and, under certain conditions, retards aging in mice. It is also applied topically in cosmetic preparations.

It has been reported, based on a small sample, that United States residents, because of the previously mentioned consumption and excretion factors, have 1.30.+-.0.82 parts per million of BHT in body fat tissue. What effect this may have on viruses hosted by humans is not known. Higher levels, and in non-fat tissue, could be achieved by ingestion orally or systemically of larger amounts of BHT than normally consumed as food additives.

The effectiveness of BHT as an antioxidant for certain foods is probably due in good part to its high solubility in fats and its extremely low solubility in water. This places the BHT molecule in regions where its antioxidant activity is most effective in preventing rancidity. These same hydrophobic characteristics, when considered for living systems, suggest that BHT may have strong interactions with the hydrocarbon zones of membrane structures, and perturbing effects of BHT on membrane associated function, have, in fact, been observed by Metcalfe, 23 J. Pharm. Pharmac. 817 (1971) and Eletr et al., 339 Biochim. Biophys. Acta. 190 (1974). The interaction of BHT with membranes and the results of this interaction are very likely distinct from and independent of its antioxidizing action.

We have unexpectedly found that BHT is surprisingly effective in the inactivation of lipid-containing viruses. BHT has been shown effective against such lipid-containing viruses as herpes simplex, .phi.6 and PM2 but ineffective against such non-lipid viruses as polio and .phi.23-1-a. We have further found that BHT is effective in reducing the duration of or controlling the start of herpes simplex skin lesions on humans and eye infections in rabbits.

The FIGURE is a graph demonstrating results achieved with the present invention.

In vitro studies have been made with herpes simplex virus type 1, strain KOS (hereinafter HSV); a syncytial-forming mutant derived from the KOS strain, designated HSV-syn 20; polio virus, type 2, attenuated, P712 ch2ab; PM2 (a bacteriophage) isolated by Espejo et al., 34 Virology 738 (1968); .phi.6 (bacterial virus) isolated by Vidaver et al., 11 J. Virol. 799 (1973); and .phi.23-1-a isolated by Vidaver. Both .phi.6 and .phi.23-1-a infect the plant pathogen Pseudomonas phaseolicola strain HB10Y.

Virus stocks were diluted to approximately (2 to 4).times.10.sup.7 plaque-forming units per milliliter in appropriate buffered solutions. A 0.1-ml portion of BHT in different molar solutions in 95% ethanol was mixed with 5 ml of buffer, and then added to a 5-ml sample of the virus. After 30 minutes, the samples were diluted and assayed for plaque-forming units on appropriate host cells. The results are observed in the figure of the drawing which is a logarithmic graph where % survival is plotted against BHT concentration in milli-molar that was present during the 30 minute exposure.

Under the testing conditions, this clearly demonstrates BHT effectiveness against the two lipid-containing viruses, .phi.6 and HSV-syn 20 and ineffectiveness against the non-lipid containing polio virus.

Further testing with similar solutions was then conducted to show the BHT concentration required to inactivate 50% of a given virus, the results of which are shown in the following table:

Here again the effectiveness is demonstrated only against the lipid-containing viruses, no tests having been run above 5.times.10.sup.-4 (M) BHT concentration. It is interesting to note the difference between .phi.6 and .phi.23-1-a which normally infect the same host.

Laboratory experiments carried out on human or bacterial cells are all carried out in aqueous media. While the metabolic functions of cells are also carried out in an aqueous medium there remain some important considerations in getting BHT to the site of viral infection. In the test tube case, with isolated virus, the BHT must diffuse through water until it comes in contact with a surface or zone which has more suitable solubility properties such as a viral or cell membrane. Therefore, the delivery of BHT molecules to these sites is a requirement in order for BHT to be effective as an antiviral agent. Application of BHT to an infected tissue surface also has the problem of delivery of adequate BHT to inactivate the viral agents. Due to the low solubility of BHT in water a more suitable solvent must be used. Ideally the carrier solvent would be saturated with BHT and upon application to an infected area the BHT would exchange to the viral and cell membrane. Due to these considerations we have adopted various solvent mixtures including those shown below for application to skin and mucous membrane areas (% by weight).

Care must be taken to keep the container closed as evaporation may cause the BHT to precipitate. Other solvent carriers are 1% to saturation (about 20%) of BHT in mineral oil or petrolatum.

Twenty patients suffering with chronic recurring herpes on varying body sites, including lips, hands and genitalia were treated with the above ethanol solutions of BHT. The average previous episode in these patients lasted seven days from first eruptions of a vesicle until complete clearing. Starting with appearance of the vesicles, the patients applied small amounts of the above formulations directly to the infected area four times daily. In eighteen patients, the duration was diminished to an average of three days. There was no appreciable difference in the other two patients.

Thirty rabbits were divided into three groups and the eyes of all treated with cultured herpes simplex virus. A control group was not further treated, a second group was treated with iododeoxyuridine (IDU), which is accepted as an effective form of therapy for herpes infection of the eyes, and the third group was treated with a 5% solution of BHT in mineral oil. After 4 days, the eyes of the BHT and IDU groups were controlled and comparable, whereas the infection was progressive in the non-treated group.

For topical application of the non-toxic BHT, concentration in the carrier is not as important as total amount applied. Saturated solutions, however, decrease dilution of the BHT and increase transfer to the virus cells. Other appropriate pharmaceutical carriers may be used, bearing in mind the hydrophobic nature of BHT and sensitivity of tissue to be treated. Generally long polymers with hdyrocarbon side groups dissolve BHT but do not irritate tissues. A 1% solution is generally a minimum but 5-20% or up to saturation of a particular carrier is preferred.

Herpes simplex infections occur and recur at many areas and organs of the body, but particularly the skin and mucocutaneous areas. The most common sites are face (particularly around the lips) and neck, followed by anogenital area and then the sacrum and buttocks. It is seen anywhere on the skin including ears, nose, chest, abdomen, arms, palms, dorsa of the hands, fingers, thighs and legs. Other common sites are the eyes and cervix. Less often involved but observed are the mouth, respiratory tract and central nervous system. The BHT compositions herein are designed for topical application to all skin areas, eyes and mucocutaneous area such as lips, nares, prepuce, glans penis, cervix and vaginal tract. Mineral oil and petrolatum carriers are generally used with the more sensitive treatment areas.