Host defense in cryptococcosis. I. An in vivo model for evaluating immune response.

An inbred mouse model was used to evaluate in vivo host immune response to Cryptococcus neoformans. Within 1 week of immunization, mice developed delayed type hypersensitivity reactions (DTH) to cryptococcal extracts derived from either culture filtrates or disrupted cells. There was no significant cross reactivity with extracts of other fungi. Previous immunization provided considerable protection against subsequent challenge with multiple strains of cryptococci. DTH also developed after nonimmunized mice were challenged with C. neoformans; however, in this situation DTH was not associated with prolonged survival. These studies indicate that mice can be immunized and protected against cryptococcosis and that this protection is associated with acquisition of DTH to cryptococcal antigens.