Use of lectins for characterization of o-linked glycans of herpes simplex virus glycoproteins

The existence of O-linked glycans in viral glycoproteins was described in the early 1980s for enveloped viruses such as herpes simplex virus type 1 (HSV-1), vaccinia virus, and mouse hepatitis virus (1-4). Glycoprotein C of HSV-1 (designated gC-1) was demonstrated to contain domains, in which numerous O-linked glycans were concentrated to pronase-resistant clusters (5-7), thereby resembling the organization of mucins (8). Thus glycoprotein, containing nine sites for N-linked glycosylation in addition to the O-linked glycans, is responsible for several important biological activities, including virus receptor binding (9) and binding of factor C3b of the complement system (10). The function of the O-linked glycans in these activities remains unclear, but it is conceivable that their clustered appearance may cause gC-1 to adopt an extended fibrous conformation (11), as originally demonstrated for the O-linked glycans of mucins (8). Use of lectins facilitates a structural analysis of clustered O-linked glycans of gC-1 and it is possible that the methodology presented here may be of more general use, as similar arrangements of clustered O-linked glycans are present in an increasing number known glycoproteins of other enveloped viruses including herpes simplex virus type 2 (12,13), Epstein-Barr virus (14), and respiratory syncytial virus (15).