Genetic characterisation of the Egyptian vaccinal strain Abu-Hammad of bovine herpesvirus-1.

The Egyptian Abu-Hammad vaccinal strain of bovine herpesvirus-1 (BHV-1) was genetically characterised by comparing HindIII endonuclease genomic fingerprints of the Egyptian BHV-1 with reference strain Cooper 1 of BHV-1 subtype 1 (BHV-1.1). Analyses of nucleotide (nt) and deduced amino acid (aa) sequences and phylogeny of the major viral immunogen, glycoprotein D (gD), were used to compare the Egyptian BHV-1 with related alphaherpesviruses. HindIII restriction digests revealed close identity between the Egyptian BHV-1 and reference BHV-1.1. Both nt and aa sequence alignments revealed variable degrees of sequence similarity with other alphaherpesviruses. Possible mutational frameshifts were observed at nt 509 and 615 of the Egyptian BHV-1 gD. The Egyptian vaccinal BHV-1 was grouped with BHV-1.1 in a distinct branch of the phylogenetic tree. Conservation of five cysteine residues and glycosylation domains emphasised the importance of the amino terminus for immunological and biological function of alphaherpesvirus gD. The most divergent domain of 17 residues at positions 168-184 and an additional cysteine residue at position 178 distinguish the Egyptian BHV-1 from other herpesviruses. This work demonstrated that HindIII genomic fingerprinting and sequencing of the gD gene are useful for genetic characterisation of BHV-1. They may also be applied to epidemiological studies and development of BHV-1 vaccines.