Identification and comparative sequence analysis of a gene in equine herpesvirus 1 with homology to the herpes simplex virus glycoprotein D gene

Abstract

A homologue of the herpes simplex virus (HSV) glycoprotein D gene has been identified in the genome of equine herpesvirus-1 (EHV-1, equine abortion virus). An open reading frame in the middle of the short unique (US) region is capable of encoding a polypeptide of 402 amino acids that has 26% and 20% of its residues matching pseudorabies virus (PRV) gp50 and HSV-1 gD, respectively. Despite this low level of similarity, the positional identity of six cysteine residues and certain motifs, and the location of the EHV-1 gene, clearly define the EHV-1 polypeptide as one of a family of "gD-like" proteins. Two transcripts of 3.3-3.6 kb and 5.4-5.9 kb were identified, consistent with coterminal mRNAs for the EHV-1 gD gene and the adjacent upstream gene, respectively. Partial sequencing of other regions in US also revealed EHV-1 homologues of HSV-1 gE and gI genes, and a possible equivalent gene to PRV gX. By analogy with the ability of HSV-1 gD and PRV gp50 to induce strong anti-viral immune responses, the EHV-1 gD gene product is expected to be an excellent candidate for development as a vaccine antigen.

N-terminal sequence analysis of equine herpesvirus 1 glycoproteins D and B and evidence for internal cleavage of the gene 71 product

“…2(b). The signal cleavage site for EHV-1 gB was between Ala sS and Va186 as predicted, while for EHV-1 gD the cleavage site was between Arg 35 and Ala 36, nine amino acids downstream of the predicted site (Whalley et al, 1991;Flowers et al, 1991). An identical N-terminal sequence was obtained for purified EHV-1 gD expressed by a Chinese hamster ovary (CHO) cell line (J. E. Wellington, unpublished results).…”

“…. Amino acid sequences of N termini of processed EHV-I gD, small and large subunits of EHV-I gB, and the 42 kDa cleavage product of gene 7 I, aligned with amino acid sequences predicted from nucleotide sequences (Whalley et al, 1989(Whalley et al, , 1991Telford et al, 1992). V, Cleavage sites.…”

“…Q above the gD sequence represents the observation of a significant amount of glutamine at +4 from the cleavage site. (b) Schematic diagram representing translation products of the EHV-1 genes for gD and gB and EHV-1 gene 71 (Whalley et al, 1989(Whalley et al, , 1991Telford et al, 1992) showing cleavage sites (V), predicted cleavage sites (V), cysteine residues (C), potential N-linked glycosylation sites (lollipops) and hydrophobic regions (IN).…”

“…Thus the predicted unmodified molecular masses of the large and (Eisenberg et al, 1984;Whalley et al, 1989Whalley et al, , 1991Keller et al, 1986;Spaete et aI., 1988 ;W61fer et al, 1990;ClaessonWelsh & Spear, 1987;Tikoo et al, 1990;Telford et al, 1992). * VZV numbering based on initiating methionine at residue -63 relative to predicted start site of Davison & Scott (1986).…”

“…One exception is gene 71 (Telford et al, 1992) which has no known homologue in any of the herpesviruses sequenced to date, apart from the closely related EHV-4 (Nagesha et al, 1993). The signal cleavage sites of EHV-1 gD (Flowers et al, 1991;Audonnet et al, 1990;Whalley et al, 1991) and EHV-1 gB (Whalley et al, 1989) were predicted from deduced amino acid sequences using the (-3,-1) rule of von Heijne (1984) although these have not been verified by direct amino acid sequencing. EHV-1 gB is cleaved to yield subunits of approximately 76 and 54 kDa which are linked by disulphide bonds to form a 145 kDa heterodimer (Sullivan et al, 1989;Meredith et al, 1989).…”