Immunization of mice with a mutant of Cryptococcus neoformans. Characterization of the mutant, actively acquired resistance to experimental cryptococcosis in mice.

In 69% of subdermally and 50% of subcutaneously immunized mice, immunity against Cryptococcus neoformans was obtained. The vaccine consisted of a gamma-irradiated mutant, which grew well at 5 degree C and at room temperature. Many subcultures and animal passages did not restore this mutant to the encapsulated, pathogenic wild type.