Glycosylation of the major human Pneumocystis carinii surface antigen

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Abstract
It has recently been shown that the major rat P. carinii surface antigen is important for initial host‐organism attachment, possibly through binding to fibronectin, mannose‐binding protein, or surfactant protein A. Since a carbohydrate/lectin interaction may be involved in adhesion, we undertook this study to characterize the glycosylation of the major human P. carinii surface glycoprotein (gp95). We have used purified gp95 as a source of antigen, and in lectin binding and deglycosylation studies it was found that approximately 9% of gp95 consists of N‐linked carbohydrates of mainly high‐mannose and bisected complex‐type glycans. Using a polyclonal antibody raised against purified gp95 and crossed affinoimmunoelectrophoresis and the lectins Con A and WGA, gp95 exhibited carbohydrate‐dependent microheterogeneity. We therefore suggest that gp95 is composed of subtypes which differ in N‐linked glycosylation.