Variability in expression of antigens responsible for serotype specificity in Candida albicans

1 Departamento de Inmunologia, Microbiología y Parasitología, Facultad de Medicina y Odontologia, Apartado 699, E-48080 Bilbao, Vizcaya, Spain 2 Departamento de Enfermeria l, Universidad del País Vasco, Apartado 699, E-48080 Bilbao, Vizcaya, Spain ABSTRACT Summary: The monoclonal antibody (mAb) B9E, which reacts with a cell wall surface determinant of Candida albicans serotype A, and a polyclonal monospecific antiserum against the antigen 6 (IF6) were used to investigate the expression of the antigens responsible for the serotype specificity in C. albicans under different growth conditions. By indirect immunofluorescence, both antibodies reacted with the cell wall surface of serotype A yeast cells and germ tubes grown in vitro but no reactivity was observed with serotype B yeast cells. In some cases, only a weak reactivity restricted to a zone close to the parent yeast cell was observed in serotype B germ tubes stained with mAb B9E. Both antibodies reacted strongly with yeast cells and germ tubes present in kidney abscesses from rabbits infected with both serotypes, but only serotype A yeast cells and germ tubes present in smears from patients with vulvovaginal candidiasis reacted with B9E and IF6 antibodies. The expression of antigens reactive with both antibodies was modulated by the pH of the environment in which the fungus was grown. Both antibodies showed a similar pattern of reactivity when studied with a spectrofluorometer. Serotype A yeast cells showed maximum reactivity when cells were grown on Sabouraud dextrose broth supplemented with yeast extract at pH 4.6. The lowest reactivity was observed in cells grown at pH 2.0. Conversely, the reactivity of serotype B yeast cells increased at alkaline pH values, the highest being in cells grown at pH values of 7.2 and 9.5. A precise use of the methods employed in studies on C. albicans serotype prevalence will be important to avoid the influence of pH on the expression of antigens conferring serotype specificity. 3 Author for correspondence: Jose Ponton. Tel: +34 4 4647700 ext. 2746. Fax: +34 4 4648152. e-mail: oipposaj @ lg.ehu.es Keywords: Candida albicans , serotypes, pH, monoclonal antibodies