Antigenic relationship between Candida parapsilosis and Candida albicans serotype B.

We examined the antigenic relationship between Candida parapsilosis and C. albicans serotype B with respect to antigenic factors 13 and 13b, specific for the former species and common to both species, respectively. Acetolysis of C. albicans serotype B cell-wall mannan gave six oligosaccharides. Their chemical structure was determined by 1H-nuclear magnetic resonance (NMR) spectroscopy, methylation analysis, and partial acid hydrolysis. The structure of the hexasaccharide derived from C. albicans serotype B mannan was alpha-D-Manp-(1-2)-alpha-D-Manp-(1-3)-alpha-D-Manp-(1- 2)-alpha-D-Manp-(1-2)- alpha-D-Manp-(1-2)-D-Man (M6) which is identical to that from C. parapsilosis mannan. Inhibition of two precipitin reaction systems (anti-C. albicans serotype B serum and anti-C. parapsilosis serum to the respective homologous mannan), by oligosaccharides from homologous and heterologous mannans indicated that M6 from either C. albicans serotype B or C. parapsilosis was the most effective inhibitor. Moreover inhibition of the agglutination reaction between factor serum containing anti-factors 13 and 13b and C. albicans serotype B or C. parapsilosis cells by oligosaccharides from both mannans also indicated that the M6s were the most effective inhibitors. These results suggest that the M6s derived from the two species are identical in their chemical structure, although the structures of the whole mannans of the two species are not identical as demonstrated by gel diffusion precipitation patterns, and that M6s may be involved in the specificities of antigenic factors 13 and 13b. The amount of M6 is larger in C. parapsilosis cell-wall mannan, suggesting that high repeating frequency of M6 fragment may induce the antibody specific for C. parapsilosis.