Sequence analysis of the equid herpesvirus 2 chemokine receptor homologues E1, ORF74 and E6 demonstrates high sequence divergence between field isolates.
Equid herpesvirus 2 (EHV-2), in common with other members of the subfamily Gammaherpesvirinae, encodes homologues of cellular seven-transmembrane receptors (7TMR), namely open reading frames (ORFs) E1, 74 and E6, which each show some similarity to cellular chemokine receptors. Whereas ORF74 and E6 are members of gammaherpesvirus-conserved 7TMR gene families, E1 is currently unique to EHV-2. To investigate their genetic variability, EHV-2 7TMRs from a panel of equine gammaherpesvirus isolates were sequenced. A region of gB was sequenced to provide comparative sequence data. Phylogenetic analysis revealed six 'genogroups' for E1 and four for ORF74, which exhibited approximately 10-38 and 11-27 % amino acid difference between groups, respectively. In contrast, E6 was highly conserved, with two genogroups identified. The greatest variation was observed within the N-terminal domains and other extracellular regions. Nevertheless, analysis of the number of non-synonymous (d(N)) and synonymous (d(S)) substitutions per site generally supported the hypothesis that the 7TMRs are under negative selective pressure to retain functionally important residues, although some site-specific positive selection (d(N)>d(S)) was also observed. Collectively, these data are consistent with transmembrane and cytoplasmic domains being less tolerant of mutations with adverse effects upon function. Finally, there was no evidence for genetic linkage between the different gB, E1, ORF74 and E6 genotypes, suggesting frequent intergenic recombination between different EHV-2 strains.
Sharp
Emma L
EL
Department of Infectious Diseases, Animal Health Trust, Kentford, Newmarket CB8 7UU, UK.
Farrell
Helen E
HE
Sir Albert Sakzewski Virus Research Centre, University of Queensland, Herston, QLD 4029, Australia.|Department of Infectious Diseases, Animal Health Trust, Kentford, Newmarket CB8 7UU, UK.
Borchers
Kerstin
K
Institute for Virology, FU Berlin, Königin-Luise-Str. 49, 14195 Berlin, Germany.
Holmes
Edward C
EC
Department of Biology, The Pennsylvania State University, PA 16802, USA.
Davis-Poynter
Nicholas J
NJ
Sir Albert Sakzewski Virus Research Centre, University of Queensland, Herston, QLD 4029, Australia.|Department of Infectious Diseases, Animal Health Trust, Kentford, Newmarket CB8 7UU, UK.
D000595:Amino Acid Sequence; D000818:Animals; D018929:Cell Culture Techniques; D017124:Conserved Sequence; D017931:DNA Primers; D004279:DNA, Viral / Q000235:genetics / Q000302:isolation & purification; D014644:Genetic Variation; D008969:Molecular Sequence Data; D016366:Open Reading Frames; D010802:Phylogeny; D016133:Polymerase Chain Reaction; D019707:Receptors, Chemokine / Q000235:genetics*; D018144:Rhadinovirus / Q000145:classification / Q000235:genetics* / Q000302:isolation & purification; D016415:Sequence Alignment; D017386:Sequence Homology, Amino Acid; D014764:Viral Proteins / Q000737:chemistry / Q000235:genetics*
D017931:DNA Primers; D004279:DNA, Viral; D019707:Receptors, Chemokine; D014764:Viral Proteins