Identification of two germ-tube-specific cell wall antigens of Candida albicans

Outer cell wall layers of intact yeast- and mycelial-phase Candida albicans B311 were extracted with dithiothreitol. Antisera against mycelial-phase organisms were absorbed with yeast-phase organisms or yeast-phase extract and used to stain Western blots of sodium dodecyl sulfate-polyacrylamide gels loaded with yeast- and mycelial-phase extracts. Autoradiography of gels loaded with extracts from organisms surface labeled with 125I was used to detect surface antigens containing proteins. Antigen bands of interest identified in Western blots were cut from the blots and used to immunize rabbits. Two antigens were identified in the mycelial-phase extract which were not present in the yeast-phase extract. The first was a 19-kilodalton protein that was present in the cell walls of germ tubes but was not expressed on their surfaces. The second was a polysaccharide-rich high-molecular-weight antigen which was expressed on the surface of the germ tube. Treatment of mycelial-phase extract with protease and endo-beta-N-acetylglucosaminidase H demonstrated that this antigen was composed of polysaccharides linked through di-N-acetylchitobiose groups to proteins.