Immunization of Mice with Viable Coccidioides Immitis

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Abstract
Summary: Mice which were vaccinated with a nonliving vaccine prepared from the mycelium-arthrospore phase of Coccidioides immitis survived challenge doses with a virulent strain administered intraperitoneally. However, the immunity was insufficient to protect the animals against similar challenge doses administered by the intranasal route. After vaccination with viable arthrospores obtained from strains of varying virulence, protection was provided against both intraperitoneal and intranasal challenge. Immunity evoked by the subcutaneous administration of a riboflavin-dependent auxotroph of very low virulence afforded protection against intranasally administered challenges of up to 200 arthrospores. The immune response was augmented by vaccinating the mice concurrently by both the subcutaneous and the intranasal routes. When the auxotroph was administered by the intranasal route exclusively, the extent of immunity afforded was, within limits, a function of dosage. The reversion of the auxotroph to prototrophy and virulence in vivo currently contraindicates its use in other than experimental studies.