Immunity to histoplasmosis induced in mice by components of Histoplasma capsulatum

Twenty-three strains of Histoplasma capsulatum were studied. The data indicated that each strain had individual characteristics with regard to: macroscopic appearance of colonies, measurement of spore sizes, relative number of spores, virulence as determined by intravenous LD50 in mice, immunization capacity of vaccines, and chemical composition of the vaccines prepared from four strains. Strains G10, G17M, 2645, and 3330 were used to study the immunogenicity of the fungus, A cell free extract prepared from the mycelial phase of strain G10 and a cell free extract prepared from the yeast phase of strain G17M produced similar protection in immunized mice, G10 and G17M vaccines also had similar chemical composition with high carbohydrate content and low protein content. Strains 3154 and G17M were found to be the most virulent by the method employed. The sporulation number, as determined by a rank rating system, showed that each strain produced various numbers of both types of spores, The results indicated that Sabouraud's medium with phosphate ion produced abundant and numerous spores. The macroscopic description of each strain on various media indicated that each strain varies in morphological characteristics depending on the nutrition available.