Enzymatic release of germ tube-specific antigens from cell walls of Candida albicans

Abstract

The differences between blastospores and germ tubes of Candida albicans, as previously shown by immunofluorescence, were further studied by comparing digests of cell walls of both growth forms. Organisms were surface labeled with 125I, and cell walls were digested enzymatically. When Zymolase digests were treated with polyclonal, polyspecific antiserum to C. albicans 441B, which stains only germ tubes in immunofluorescence assays, components of molecular weights 200,000 and 155,000 were immunoprecipitated from digests of germ tubes of strain B311, but nothing was recovered from blastospores. Whereas the 200,000-molecular-weight component was found in the three strains tested, the 155,000-molecular-weight component was found only in strain B311. When Zymolase digests were treated with unadsorbed antiserum, which stains both blastospores and germ tubes in immunofluorescence assays, an additional component was precipitated from digests of both growth forms with a molecular weight greater than the 200,000-molecular-weight marker. All three antigens were mannoproteins, as was shown by their abilities to bind concanavalin A and to be labeled by 125I. Also, all antigens were located on the cell surface, as was shown by the following criteria: adsorption of antisera with live organisms removed antibody to these components, and antibody eluted from surfaces of whole organisms precipitated all components. Components common to both growth forms, as well as germ tube-specific components, were detected in trypsin and chymotrypsin digests, but their molecular weights differed from those of Zymolase digests. Thus, germ tube-specific surface determinants as well as determinants common to both growth forms were detected on enzymatically released cell wall components.