ANALYSIS OF MANNOPROTEINS FROM BLASTOCONIDIA AND HYPHAE OF CANDIDA-ALBICANS WITH A COMMON EPITOPE RECOGNIZED BY ANTI-COMPLEMENT RECEPTOR TYPE-2 ANTIBODIES

Mannoproteins of approximately 50 kDa from blastoconidia and 60 kDa fr om hyphae of Candida albicans reacted in Western blots (immunoblots) w ith either a polyclonal rabbit antiserum (CA-7) or a monoclonal antibo dy (CA-A) to the C. albicans C3d-binding protein (complement receptor type 2). The glycosylated nature of these proteins was demonstrated by their reactivity with concanavalin A and by selective labeling with t he biotin-hydrazide reagent following periodate oxidation. Differences in the oligosaccharides of these proteins were observed in regard to their reactivity with lectin-peroxidase reagents and sensitivity to gl ycosidases such as N-glycanase or endoglycosidase F (but not endoglyco sidase H). The 60-kDa mannoprotein reacted with wheat germ agglutinin, while the 50-kDa mannoprotein did not. Treatment of the 60-kDa mannop rotein with the glycosidases mentioned above resulted in its conversio n into a species of 40 to 45 kDa. Enzyme treatment had no obvious effe ct on the electrophoretic mobility of the 50-kDa species from blastoco nidia. Both the 50- and 60-kDa glycoproteins remained immunoreactive a fter treatment with the glycosidases. Reactivities of the two mannopro teins to neuraminidase also differed. Finally, the 50-kDa (blastoconid ia) and the 60-kDa (hyphae) mannoproteins were purified by using ion-e xchange chromatography and electroelution. The purified proteins diffe red in net charge, the 60-kDa species having a more acidic pl. Functio nal activity of the purified mannoproteins was demonstrated, as each i nhibited the rosetting of antibody-sensitized sheep erythrocytes conju gated with iC3b or C3d by hyphae. Thus, an epitope(s) common to both a mycelial and blastoconidial mannoprotein is associated with a structu rally different oligosaccharide for each growth form.