Chemical, serologic and skin test activities of polysaccharides extracted from Histoplasma capsulatum and Blastomyces dermatitidis

Polysaccharides were extracted by the chemical method of Heidlberger, from each of three strains of Histoplasma capsulatum and Blastomyces dermatitidis. Significantly greater yields of polysaccharides were extracted from the culture broth filtrate than were extracted from the yeast phase cells. Studies of the constituents of these polysaccharides by paper chromatography and cysteine-sulfuric acid tests for pentose and hexose, micro-Kjedhahl nitrogen and other qualitative and quantitative chemical test suggest that the H. capuslatum and B. dermatitidis polysaccharides consisted of glucose unites with and occasional glucoseamine moiety. The capacity of the H. capuslatum and B. dermatitidis polysaccharides to produce visible antigen-antibody precipitates with homologous and heterogous antisera were investigated by the Oudin and Ouchterlony agar precipitation methods. These studies showed that the H. capuslatum and B. dermatitidis polysaccharides reacted only with their respective homologous antibody and that each produced a single band or precipitate. These data indicated that each antigen had a specific in vitro antigenic action, with one antigenically active component. Complement fixation and hemagglutination tests were employed using the H. capuslatum polysaccharide antigen. This study showed that the polysaccharide antigen could be used as a complement fixation antigen when hyperimmune guinea pig or rabbit sera were used as antibody. Hemagglutination test results were not reproducible. The H. capuslatum and B. dermatitidis polysaccharides were used as skin test antigens. The intradermal injection of microgram amounts of these polysaccharides into guinea pigs infected with H. capuslatum and B. dermatitidis produced skin test reactions equal to those given by the standard histoplasmin or blastomycin. A study of the skin test cross reaction of the H. capuslatum polysaccharides and B. dermatitidis polysaccharides in the guinea pigs infected with H. B. dermatitidis or H. capuslatum revealed specific skin test reactions without significant cross reactivity. H. capuslatum and B. dermatitidis polysaccharides antigens were injected intradermally into 136 human volunteers. Twenty positive reactions were observed and a comparison of the extent of induration produced by histoplasmin and 10 mcg of H. capuslatum showed that H. capuslatum polysaccharide produced skin test reaction equal to those observed with histoplasmin. Specific B. dermatitidis skin test reactions were observed following injection of the B. dermatitidis polysaccharides in a few people who showed strong reactions with H. capsulatum skin test materials. These studies suggest that fungal polysaccharides, isolated by relatively simple chemical methods, may be more suitable for use as skin test antigens than the currently available preparation of histoplasmin and blastomycin.