Antigenic variations of Candida albicans in vivo and in vitro--relationships between P antigens and serotypes

Serum samples from patients with candidosis and from rabbits experimentally infected with serotype B C. albicans strains consistently showed higher antibody titers against Candida strains with serotype A antigens than strains with serotype B antigens, in indirect fluorescent antibody tests. When sera from rabbits infected with C. albicans serotype B strains were absorbed with blastospores of the homologous strain they continued to react against strains of C. albicans serotype A and a C. tropicalis strain with serotype A antigens. Serotype A-specific antisera reacted against tissue forms of C. albicans serotype B in vivo and against serotype B germ tubes, but not their parent blastospores, in vitro. These findings suggest that C. albicans B serotype cells may sometimes express, in vitro or in vivo, one or several antigens so far considered as specific of serotype A. The results have implications for the classical concept of C. albicans serotypes and for the serological diagnosis of candidosis in relation with the previously described strain P variable antigens.