Experimental phycomycosis in mice; examination of the role of acquired immunity in resistance toAbsidia ramosa

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Abstract
Summary: Attempts were made to stimulate acquired immunity to experimentalAbsidia ramosainfection in mice. Unprotected animals inoculated with large doses ofA. ramosaspores frequently developed acute phycomycosis of the central nervous system. Mice previously exposed to sub-lethal doses of spores showed a high resistance to subsequent challenge withA. ramosa. No consistent increase in resistance was observed in mice vaccinated with killedA. ramosaspores, hyphal walls, intracellular mycelial antigens or various combinations of these, with Freund's incomplete adjuvant.Antibodies to soluble mycelial antigens were inconsistently present in the sera of mice vaccinated with sub-lethal doses of viable spores. They were generally present in the sera of animals vaccinated with mycelial extracts or hyphal walls but not killed spores.Delayed hypersensitivity reactions toA. ramosamycelial antigens could usually be elicited by intradermal tests in mice exposed to viable spores but irregularly in those vaccinated with non-viable preparations. Positive reactions were also frequently given by older mice not deliberately exposed toA. ramosa.Although mice previously exposed to viableA. ramosaspores were highly resistant to intravenous or intracerebral challenge with this fungus, they were more likely to develop persistent local granulomata on subcutaneous injection of spores than were unvaccinated animals.