THE GLYCOPROTEIN-B GENES OF MAREKS-DISEASE VIRUS SEROTYPE-2 AND SEROTYPE-3 - IDENTIFICATION AND EXPRESSION BY RECOMBINANT FOWLPOX VIRUSES

The nucleotide sequences of the glycoprotein B (gB) genes of Marek's d isease virus (MDV) serotypes 2 and 3 were determined (gB-2 and gB-3, r espectively). The genomic locations of these genes coincide with that of the gB gene of serotype 1 MDV (gB-1). Alignment with gB-1 (Ross et al., 1989, J. Gen. Virol. 70, 1789-1804) revealed predicted amino acid identities of 83 and 82% for gB-2 and gB-3, respectively. Excluding t he predicted N-terminal signal sequences, 8 of 9 potential N-linked gl ycosylation sites and all 10 cysteine residues in gB-1 are conserved i n both gB-2 and gB-3. In addition, the putative proteolytic cleavage s ites for processing of precursors (gp100s) to gp60s and gp49s are cons erved among the three gB homologs. Fowlpox virus (FPV) recombinants ex pressing either the gB-2 or the gB-3 gene were constructed. We detecte d expression of authentic gB-2 and gB-3 complexes in cells infected wi th these FPV recombinants. Digestion of immunoprecipitated gB-1 and gB -3 with endoglycosidases revealed that both gp60s are modified by the additions of O-glycans and complex carbohydrates after cleavage of gp1 00s, while gp100s and gp49s contain only high-mannose carbohydrates. W e confirm that the size differences between gB-1 and gB-3 complexes ar e due to different carbohydrate modifications, (C) 1994 Academic Press , Inc.