Immunity to histoplasmosis induced in mice by components of Histoplasma capsulatum.

Six strains of Histoplasma capsulatum were characterized for immunogenic capacity as vaccines. The yeast phase of strain 3154 was used as the challenge organism in the immunization experiments. Vaccines prepared from various elements of strains G10, G17M, 2645, and 3330 were used to immunize mice. After challenge, the potency ratios were determined. The vaccine prepared from the mycelial phase of G10 cell-free extract and the cell-free extract prepared from the yeast phase of G17M yielded similar potency ratios. The two vaccines, G10 and G17M, had similar chemical composition with high carbohydrate and low protein content. The remaining vaccines prepared from either cell-free extracts or whole cells gave potency ratios that varied from 1.5 to 20.0, and did not correlate with chemical composition.