Populations of herpes simplex virus glycoprotein gC with and without affinity for the N-acetyl-galactosamine specific lectin of Helix pomatia

Abstract

Two fractions of herpes simplex virus glycoprotein gC were isolated and characterized by means of immunosorbent-purification with monoclonal antibodies against gC and Helix pomatia lectin (HPA) affinity chromatography. About 25 per cent of the glycoprotein gC population demonstrated affinity for the lectin, compatible with presence of N-acetylgalactosamine as terminal sugar of the oligosaccharide. The HPA-binding populations of gC appeared as two electrophoretic bands with lower molecular weights than the non-binding gC. The gC subfraction without affinity for the HPA was subjected to treatments aiming to desialylize the carbohydrate moiety. Only 5 per cent of the initially non-reactive fraction of gC became reactive to HPA after the treatments, suggesting that masking of penultimate N-acetylgalactosamine by sialic acid was not a main reason for lack of HPA affinity. Results of treatment with alkaline Na BH4 demonstrated presence of oligosaccharide-peptide linkages sensitive to beta-elimination suggesting O-glycosidic type of linkage. The subfraction of gC demonstrating affinity for HPA as well as gC devoid of HPA binding capacity both revealed affinity for Con A. Therefore N-glycosidically as well as O-glycosidically linked oligosaccharides seemed to be present on the one and same glycoprotein. On the basis of the results presented we assume that the glycosylation of HSV glycoprotein gC may lead to, at least, two populations of the glycoprotein gC, one with terminal N-acetylgalactosamine residues of oligosaccharides O-glycosidically linked to the polypeptide and the other without affinity for HPA. However, both populations of gC contain similar proportions of oligosaccharides of the high mannose or complex types with N-glycosidic carbohydrate-peptide linkages as indicated by their affinity for Con A.