Method for Treating Fungal Infections Using Cell Lytic Enzymes

The present invention encompasses a method for treating fungal infections in animals comprising administering to animals in need of antifungal treatment an effective amount of fungal cell lytic anzymes extracted from Coprinus, Lycoperdon, or Bolbitius in conjunction with conventional antimycotic agents such as amphotericin B or Nystatin. The fungal cell lytic enzymes are extracted from Coprinus, Lycoperdon, and Bolbitius by conventional enzyme isolation techniques. The fungal cell lytic enzymes retain their activity in vivo, are relatively non toxic and destroy fungi by degrading fungal cell walls and weakening the fungal cell walls so that conventional antimy cotic agents are far more effective. The method of the present invention is particularly useful in treating infections by apportunistic fungi such as Aspergillus fumigatus and Candida albicans. The method of the present invention is also useful for treating Trichophyton mentagrophytes infections.

Fungal cell lytic enzymes are available from Lycoperdon, Coprinus, and Bolbitius. Lycoperdon depressum, Lycoperdon gigantea, and Lycoperdon pyriforme are preferred sources of fungal cell lytic anzymes. The specimens are collected in the field or cultured on solid or in liquid media.

Fresh, frozen or lyophilized whole specimens of Lycoperdon such as L. pyriforme, etc. are homogenized in water, saline, buffer or other suitable diluent. The homogenate is expressed through cloth and the resultant liquid centrifuged or filtered. The supernatant contains a crude enzyme mixture containing chitinase and various other enzymes. The crude extract is either stored at 4.degree. C, lyophilized or purified as detailed below.

For enzyme production in culture, synthetic or natural media are used as long as essential nutrients are present. Such nutrients are well-known and include substances such as carbon source, a nitrogen source and inorganic compounds, etc., in appropriate amounts. Culturing of the organisms is carried out at a temperature of, for example, 20.degree.-35.degree. C and at a pH of, for example, 4-8 for a period of 2-15 days. In liquid media, culturing is carried out under aerobic conditions either by shaking or by stirring and aeration of the submerged culture. As a result, enzymes accumulate in both the culture medium and in the fungal mycelium.

Enzymes are extracted as follows: In the case of a solid medium, the mycelium and medium are homogenized and the resultant homogenate extracted with several volumes of water, saline, buffer or other suitable diluent. The resultant crude enzyme solutions are centrifuged or filtered in the liquid culture, the vegatative mycelium is separated from both by filtration or centrifugation. The filtrate or supernatant contains crude enzyme. A further crude enzyme solution is obtained by either homogenizing the vegetative mycelium immediately or by lyophilizing the mycelium and then homogenizing it in a suitable diluent. The resultant solution is filtered or centrifuged.

Enzyme solutions obtained by any of the above methods are purified and concentrated by one or more of the conventional enzyme-purifying methods such as precipitation by organic solvents, salting out, lyophilization, gel filtration and dialysis.

In a similar manner fungal cell lytic enzymes are prepared from Coprinus species such as Coprinus comatus, ATCC 12640 or ATCC 22314 or Coprinus atramentarius ATCC 22313* or field harvested counterparts. Other Coprinus sources are listed on page 181 of ATCC Catalog of Strain, 11th ed. 12301 Parklawn Drive, Rockville, Maryland. Bolbitius species are sources of cell lytic enzymes and provide copious amounts of such enzymes.

The enzymes referred to are mixtures of chitinase, chitobiase, and .alpha. 1-3, .alpha. 1-6, .beta. 1-4 glucanases and .beta. 1-3 glucanase (laminarinase). Independent sources of laminarinase, chitinase and other carbohydrases are well known, Enzymes, Enzyme Handbook, Bartman Supp I, pp 312, Springe-Verlag, N.Y., N.Y., and references therein. However, no such enzyme or mixture of enzymes has previously been injected and shown to be of low toxicity and able to destroy fungal growths in vivo. Therefore, suitable sources of fungal cell lytic enzyme mixtures can be obtained from carefully selected sources - Coprinus, Lycoperdon, and Bolbitius.

Fungal cell lytic enzymes of the present invention are especially useful in combination with conventional antifungal agents such as nystatin, amphotericin-B, griseofulvin and other agents named in Chapter 12 of Cutting's Handbook of Pharmacology, 4th Edition, Appleton-Century-Crofts, N.Y., N.Y., pages 79-85.

Coprinus extracts have an LD.sub.50 in mice of about 750 mg/kg and lycoperdon extracts have an LD.sub.50 in mice of about 700 mg/kg. Effective amounts of the fungal cell lytic enzymes are about .5 mg/kg to 5 mg/kg of a purified preparation in a pharmaceutical carrier injected daily for two or three days. Dosage depends on purity of extracts from a particular species. Extracts of the present invention may be formulated in a variety of pharmaceutical carriers, buffers and emoluents.

A preferred embodiment of the present invention is the administration of fungal cell lytic enzymes in conjunction with drugs such as nystatin or amphotericin-B. Generally one regimen should follow the other with 24 hours. Those skilled in the pharmaceutical arts will recognize that the dose of fungal cell lytic enzymes and conventional antifungal agent will have to be varied to control stubborn fungal infections or to account for individual responsiveness.

U.S. Pat. No. 3,682,778 describes methods for extracting cell lytic enzymes from various Coprinus species. M. V. Tracey, Biochem Journal 61, 579-8(1955) discloses extracts of many Lycoperdon species and compares the chitinase activities of these extracts to chitinase activities of Coprinus extracts. Britich Patent Nos. 1,048,887 and 1,410,079 describe bacterial sources of cell lytic enzymes and their in vitro activity against pathogenic fungi and Kokai et al., Chem Abs 79, 133662V describes .beta.-1-3-glucanase and chitinase as a fungicide for rice blight. Miura, Tohoku Journal of Exp. Med 59, No. 4 403(1954) indicates that in vitro activity of bacterial chitinase might suggest its use as a topical dermatomycosis agent. The method of the present invention is distinguished in that fungal cell lytic enzymes extracted from Coprinus, Lycoperdon, and Bolbitius in combination with antimycotic drugs such as amphotericin B or nystatin provide an effective treatment for fatal fungal infections. The enzymes have unexpectedly low toxicity.

The hereinafter set forth examples are intended to illustrate the invention and should not be construed as a limitation of the invention.

Toadstools of the Coprinus genus are collected when autolysis is just commencing, as shown by the darkening of the gills and the collection of dark fluid at the base. The collected toadstools are allowed to autolyse at 4.degree. C for 36 hours and the fluid is then expressed through muslin. The resulting liquid, referred to as the "crude extract", is freeze dried.

A known amount of the crude extract is dissolved in water and centrifuged at 2,000 rpm for 10 minutes to remove insoluble material. The supernatant is separated on a Biogel P-200 (BioGel is trademark of Bio Rad Labs of Richmond, Calif.) column and fractions are collected. The fractions are monitored in a spectrophotometer at 280 nm for protein and tested for Chitinase activity and a variety of other carbohydrases by conventional specific assays, and using various accepted substrates, e.g. the non-specific substrate Aspergillus fumigatus mycelium (freeze dried) and specific substrates, for example, Chitin, Laminarin, Nigeran, Dextran, Cellulose, etc. The active fractions are pooled and freeze dried.

The activity of crude extracts of toadstools and commerical purified enzymes against fungal growth in vitro is shown below.

Mixtures of laminarinase and chitinase or crude extracts of Coprinus comatus (C.c.) and Coprinus atramentarius (C.a.) at levels of 0.25 mg/ml are added to freeze dried mycelium of Aspergillus fumigatus. The rate of Chitin degradation was measured by the method of Reissig, Strominger and Leloir, J. Biol. Chem. 1955, 219, 959-966.

Preparations of enzymes and crude extracts are also tested against the growth of the fungus Aspergillus fumigatus in liquid culture. The reduction in growth of this fungus at 2 days when treated with different doses of enzymes of crude extracts are measured by the reduction in the dry weight of the mycellium.

It is shown that crude extracts of certain toadstools which contain chitinase in conjunction with certain other enzymes, are particularly potent against freeze dried mycelium and in reducing the growth of the fungus Aspergillus fumigatus in vitro. Combinations of purified enzymes are relatively poorly effective against such fungal growth in vitro.

The activity of such preparations against the lethal effects of Aspergillus fumigatus infection in mice is shown below. Mice are infected with approximately 5 .times. 10.sup.6 spores of Aspergillus fumigatus and subsequently treated with various concentrations of purified enzymes or crude extracts of C.c. and C.a. The mean survival time of the mice is measured in days.

The combined effect of enzyme compositions and drugs is enhanced by the sequential administration of these materials, particularly when the enzyme is given first followed by the drug.

Mice are challenged with approximately 5 .times. 10.sup.6 spores of Aspergillus fumigatus injected intravenously. After one day the mice receive 1.5 mg of a mixture of crude extracts of C.c. and C.a. (enzymes) intraperitoneally and after two days an injection of one of the following drugs at the following doses, also intraperitoneally:

Amphotericin (0.6 .mu.g), Griseofulvin (37.5 .mu.g) and Nystatin (12.5 .mu.g). The median time of death of the mice, in days, (the first day when 50% of the mice in each group are dead), is given below:

These results demonstrate the potent action of sequential administration of crude fungal extracts and drugs in protecting mice against the lethal effects of infection with Aspergillus fumigatus.

It has been shown that crude extracts of toadstools from the Coprinus genus are potent against chitin and against the growth of fungi in vitro. They are also capable of preventing the lethal effects of fungal infection in mice. Mixtures of enzymes available commercially, i.e., Chitinase and Laminarinase are relatively poorly effective compared even with the crude extracts described herein.

Fresh, frozen or lyophilized whole specimens of Lycoperdon depressum are homogenized in water, saline, buffer or other suitable diluent. The homogenate is expressed through cloth and the resultant liquid centrifuged or filtered. The supernatant contains crude enzyme mixture containing chitinase and other enzymes.

The activity of these extracts is illustrated by the following tests:

Mice are infected with 5 .times. 10.sup.6 spores of Aspergillus fumigatus and subsequently treated with crude extracts from Lycoperdon depressum. The mean survival time of the mice is measured in days.

Other experimental data exemplifying the methods of the present invention are summarized as follows:

1. Mixtures of Chitinase and Laminarinase ("LC") are too toxic for use (lethal dose about 14 mg/kg) and less effective than the products on which the claim is based (e.g. CC).

2. Divided doses (e.g. 3 .times. 1.5 mg CC per mouse) cures Aspergillus infection when appropriately administered and is more effective than this total amount given as a single dose.

Mice are given a single treatment of either 4.5 mg, 3 mg or 1.5 mg CC 24 hr before their anticipated death i.e. 11 days after challenge.

Mean survival (days)

S.e. of means .+-. 3.5

2 Levels of enzyme and drug are used in this experiment.

Level 1: Sub-curative giving only marginal increase in survival when given alone 24 hr after challenge.

Level 2: curative (in the case of CC extract) or maximum sub-toxic dose of drug. Program for enzyme + drug enzyme 24 hr after challenge -- drug 48 hr after challenge

1. In all cases synergy occurred between drugs and enzymes at low levels.

2. Whith amphotericin + enzyme, mice are completely cured while highest permissible sub-toxic doses of amphotericin alone are only moderately effective in prolonging life.

3. Lycoperdon depressum and L. pyriforme extracts from fresh material and culture provide similar results.

Treatment programs were as follows:

1. ALS 300 ul 24 hr before AF challenge/saline

2. ALS/AF/3 .times. l.5 mg CC at 24 hr intervals after challenge

3. ALS/AF/5 .times. 1.5 mg CC at 24 hr intervals after challenge

4. ALS/AF/1.5 mg CC/0.6 .mu.g Amphotericin "

5. ALS/AF/1.5 mg CC/0.6 .mu.g A/1.5 mg CC/0.6 .mu.g A

6. als/af/1.5 mg CC/saline/1.5 mg CC/saline

7. ALS/AF/saline/0.6 .mu.g A/saline/0.6 .mu.g A

Alternate enzyme/drug injections at levels which have little effect on survival when administered alone are most effective in increasing survival

Mice were infected intravenously with 2 .times. 10.sup.5 cells of C. albicans and treated with enzymes alone or with drug supplement as follows:

1. C. albicans challenge/saline

2. C. albicans/3 .times. 1.5 mg CC at 24 hr intervals after challenge

3. C. albicans/5 .times. 1.5 mg CC at 24 hr intervals after challenge

4. C. albicans/1.5 mg CC/0.6 .mu.g Amphotericin

5. C. albicans/1.5 mg CC/0.6 .mu.g A/1.5 mg CC/0.6 .mu.g A

6. c. albicans/1.5 mg CC/saline/1.5 mg CC/saline

7. C. albicans/saline/0.6 .mu.g A/saline/0.6 .mu.g A

1. Treatments 2 and 4 which cure mice with AF infections also prolong mean survival of Candida infected animals to 23.2 and 22 days, respectively.

2. Increasing the enzyme dose or alternating drug and enzyme markedly prolongs survival.

The shaved backs of Duncan Hartley guinea pigs are inoculated with Trichophyton mentagrophytes, a common dermatophyte. When infection is established (about 5 days) treatment is initiated, using enzymes in various concentrations and in different vehicles. The course of infection is followed by culturing samples of skin and hair taken from around the infected site before, during and after completion of treatment. Each animal receives a single daily treatment of approximately 0.5 g vehicle + enzyme.

5% w/w/CC in Carbopol proves effective in clearing infection after 8 treatments. The amount of inoculum (expressed as no. of colonies/animal) is significantly reduced after only 4 treatments.

1. AF challenge/saline at 24 and 48 hr after challenge

2. AF/1.5 mg CC at 24 hr/saline at 48 hr after challenge

3. AF/1.5 mg CC at 24 hr/1.5 mg CC at 48 hr

4. AF/0.6 .mu.g Amphotericin at 24 hr/saline at 48 hr

5. AF/0.6 .mu.g Amphotericin at 24 hr/0.6 .mu.g at 48 hr

6. AF/1.5 mg CC + 0.6 .mu.g A at 24 hr/saline at 48 hr

7. AF/1.5 mg CC + 0.6 .mu.g A at 24 hr/1.5 mg CC + 0.6 .mu.g A at 48 hr

8. AF/1.5 mg heat-inactivated CC + 0.6 .mu.g A at 24 hr/1.5 mg HICC + 0.6 .mu.g A at 48 hr