SUMMARYPurified DNAs from Marek's disease virus (MDV) and the herpesvirus of turkeys (HVT) were randomly sheared and cloned into the M 13 bacteriophage. Two-hundred and ten MDV and 130 HVT clones were sequenced to give representative samples of the genome sequences. The predicted amino acid sequences from these gammaherpesviruses were compared to known sequences from other herpesviruses using computer analysis. Thirty-five MDV and 24 HVT genes were identified by comparison with varicella-zoster virus (VZV), an alphaherpesvirus. However, only 14 MDV and seven HVT genes, giving generally lower homology scores, were found by comparison with Epstein-Barr virus (EBV), a gammaherpesvirus, indicating that MDV and HVT sequences bear greater similarity to VZV than to EBV sequences. A number of sequences were mapped by hybridizing labelled M13 clones to Southern blots of restriction fragments of MDV or HVT DNA. The results were consistent with the MDV and HVT genomes being collinear with VZV.

SUMMARYThe Marek's disease virus (MDV) homologue of the herpes simplex virus (HSV) gene encoding glycoprotein B (gB) has been identified within BamHI fragments 13 and K 3 of the 'highly oncogenic' strain RB 1B 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 MDVinfected 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.

The nucleotide sequences of the BamHI-H fragment of the HPRS16 strain of Marek's disease virus (MDV) and of its attenuated derivative HPRS16/att have been determined. The results show that in addition to the tandem expansion of a 132 bp sequence from two copies in HPRS16 virus to eight copies in HPRS16/att, nucleotide substitutions, deletions, and insertions were also noted. Several potential open reading frames (ORFs) were identified. One of these (ORF 13) encoded a deduced protein, mol wt 32 kD, which is likely to be the serotype-1 specific phosphoprotein expressed in tumours (1) and mapped to an EcoRI fragment within BamHI-H (2). Our results suggest that this ORF is unlikely to be the B antigen (3). ORF 4, which had some similarity to CD4 and immunoglobulin M heavy chain, was encoded by a transcript that originated within the first copy of the 132 bp repeat. ORF 21, which mapped entirely within UL, encoded a deduced protein at least 322 amino acids long that had some similarity to varicella zoster virus (VZV) alpha trans-inducing protein. None of these ORFs was altered significantly by attenuation, except ORF 4 and another small ORF (ORF 3), 5' of the 132 bp repeats, which would probably fail to be transcribed because of truncation of an RNA transcript.