Nucleotide Sequence and Characterization of the Marek's Disease Virus Homologue of Glycoprotein B of Herpes Simplex Virus

The Marek's disease virus (MDV) homologue of the herpes simplex virus (HSV) gene encoding glycoprotein B (gB) has been identified within BamHI fragments I3 and K3 of the 'highly oncogenic' strain RB1B of MDV. The entire nucleotide sequence of the gene has been determined and its predicted amino acid sequence shown to share gross overall structural features with the gB genes of HSV, varicella-zoster virus (VZV) and other mammalian herpesviruses. In particular, all 10 cysteine residues were conserved in MDV gB and there was extensive homology throughout the gene with VZV, HSV and pseudorabies virus except for the N and C termini. The overall percentage amino acid identity between MDV gB and gB of the alphaherpesviruses had a mean of 50% which was almost twice that between cytomegalovirus and Epstein-Barr virus. Northern blot analysis showed that the main RNA transcribed from this gene is approx. 2.7 kb in size. Antibodies raised against synthetic peptides (residues 250 to 271 and 304 to 330) allowed the identification of a family of serologically related glycoproteins of Mr 110K, 64K and 48K in extracts of MDV-infected cells using immunoblots. Furthermore, the antisera were able to differentiate between the antigens of MDV and herpesvirus of turkeys in immunoblots. Immunofluorescence tests indicated that MDV gB is associated with granules in the cytoplasm and is present at the surface of MDV-infected cells.