A Candida albicans surface antigen mediating adhesion and autoaggregation in Saccharomyces cerevisiae

In a previous study (M. Barki, Y. Koltin, M. Yanko, A. Tamarkin, and M. Rosenberg, J. Bacteriol. 175:5683-5689, 1993), a 3.3-kb DNA fragment from Candida albicans which confers adhesion and autoaggregation in Saccharomyces cerevisiae was isolated and partially characterized. In this report, evidence is presented that the adhesion-autoaggregation phenotype observed in S. cerevisiae cells transformed with the candidal DNA fragment is due to expression of a C. albicans surface antigen. Rabbit antiserum, prepared against transformant S. cerevisiae cells, was adsorbed with S. cerevisiae bearing the vector alone. Immunofluorescence micrography showed that the adsorbed antiserum bound to the surface of transformant S. cerevisiae cells as well as to C. albicans cells, but only marginally to the S. cerevisiae control. The adsorbed antiserum specifically inhibited autoaggregation of transformant cells. Further adsorption of the antiserum with transformant cells eliminated both inhibition and immunofluorescence. Autoaggregative activity and immunofluorescence of transformant cells were abolished following proteolytic treatment. Western blot (immunoblot) analysis of candidal extracts revealed that the absorbed antiserum recognized a major candidal antigen of ca. 30 kDa which was present on both yeast-phase and germ tube cells. The data suggest that the observed adhesion-autoaggregation phenotype is due to the presence of a specific candidal antigen on the outer surface of the transformant cells.