Characterization of glycoprotein B of the gammaherpesvirus equine herpesvirus-2

Twenty-two monoclonal antibodies (MAbs) were generated to the gammaherpesvirus equine herpesvirus-2 (EHV-2). Using Western blot analysis, eight MAbs recognized an Escherichia coli glutathione S-transferase (GST)-glycoprotein B (gB) fusion protein and, using overlapping GST-SB fusion proteins, a neutralization epitope was mapped to amino acids 29-74. One of the gB-specific MAbs was used to characterize the glycosylation and kinetics of synthesis of EHV-2 gB. EHV-2 gB is synthesized as a 97 kDa polypeptide that is co-translationally modified to a 130 kDa high-mannose precursor that forms a 260 kDa dimer shortly after synthesis. Each 130 kDa precursor is endoproteolytically cleaved to disulphide-linked subunits of 75 and 58 kDa prior to further processing to complex oligosaccharide-containing subunits of 89 and 65/62 kDa. The 89 and 65/62 kDa subunits of EHV-2 gB contain 39 and 17 kDa of N-linked oligosaccharides, respectively, and do not contain any O-linked oligosaccharides. Western blot analysis of purified EHV-2 virions established that gB exists as a 320 kDa dimer in the virion envelope.