Glycosylation patterns of the envelope glycoproteins of an equine-virulent Venezuelan encephalitis virus and its vaccine derivative

The equine-virulent Venezuelan encephalitis virus, Trinidad donkey (TRD), was compared to its vaccine derivative, TC-83 virus, by examining the glycosylation of the two structural envelope glycoproteins (E₁ and E₂). The number of size classes of glycopeptides on the glycoproteins was determined by P-6 column chromatography following Pronase digestion. The E₁ glycoprotein had three glycopeptide size species and the E₂ glycoprotein contained four size species ranging in mol. wt. from 1900 to 2700. Both viruses contained similar glycopeptide size species, although the relative amounts on the E₂ glycoproteins appeared to be somewhat different. All of the glycopeptide species appeared to be complex, since all were labelled with glucosamine, mannose, galactose and fucose. No mannose-rich species could be detected. The different glycopeptide species appeared to be sialylation isomers of a smaller core glycopeptide with an apparent mol. wt. of 1800 which was the sole product following desialylation of the larger glycopeptides. The number of oligosaccharide attachment sites present on both E₁ and E₂ of each virus was determined using reverse-phase high pressure liquid chromatography. This analysis indicated that the E₁ glycoprotein of both viruses had six or seven similar sugar-labelled peptide fragments following trypsin digestion. However, the E₂ glycoprotein of TRD virus contained three oligosaccharide attachment sites, whereas TC-83 E₂ glycoprotein had only two.