Characterization of antigens specific to the surface of germ tubes of Candida albicans by immunofluorescence.

To characterize germ tube-specific antigens of Candida albicans, rabbit antiserum prepared to Formalin-treated yeast possessing germ tubes was adsorbed with stationary-phase blastospores. By immunofluorescence and enzyme-linked immunosorbent assay, this antibody did not react with blastospores but detected germ tube-specific antigens in hyphal forms. Germ tube-specific antigens appeared 30 min after placing blastospores in appropriate conditions for germ tube formation. Hyphae, formed by allowing yeast to germinate for 24 h, still retained germ tube-specific antigens, but blastospores budding off these hyphae were unstained, as were log-phase blastospores. Germ tube-specific antigens were sensitive to heat, sodium metaperiodate oxidation, dithiothreitol reduction, and proteolysis with pronase, trypsin, or chymotrypsin, whereas antigens common to blastospores and germ tubes were stable to boiling, treatment with proteolytic enzymes, and dithiothreitol reduction. Thus, surfaces of germ tubes can be distinguished from those of blastospores not only immunologically, but also by the sensitivity of germ tube-specific antigens to proteolytic treatments.