Genetic characterization of the Egyptian vaccinal strain [Abu-Hammad] of bovine herpesvirus-1

ABSTRACT

The local Egyptian vaccinal strain [Abu-Hammad] of bovine herpesvirus-I [BHV-1] was genetically characterized based on two main molecular approaches; the Hind III endonuclease for genomic fingerprinting of the local BHV-1 compared to that of the reference strain [Cooper 1] of BHV-1 subtype 1 [BH V-1.1], and the analyses of nucleotide [nt] sequences, deduced amino acid [N sequences and phylogeny of the major viral immunogen, glycoprotein D [gD] of the local BHVmsu its counterparts of other related alpha-herpesviruses. The resulted sizes and c‘iccaophoretic patterns of the Hind III viral DNA fragments [A -to-M] revealed close identity between the local BHV-1 and reference BHV-1.1. Both nt and deduced aa sequence alignments revealed variable degrees of similarity of the local BHV-1 gD, which was high with BHV-1.1 and BHV-1.2; moderate with bovine herpesvrius-5; low with caprine herpesvirus-1 and suid herpesvirus-1 [pseudorabies virus]; or very low with human herpesvirus-1 and herpesvirus-2. A possible mutational frame shift at nt 509 and 615 was observed toward the carboxyl-terminus of the local BHV-1 gD. The gD nt and deduced aa sequence data enabled phylogenetic characterization of the local BHV-1 and correlated with the results of genomic fingerprinting after restriction endonuclease cleavage. Based on phylogenetic analyses, the Egyptian vaccinal BHV-1 was grouped as a BHV-1 subtype 1 in a distinguished branch within the phylogenetic tree, together with BHV1.1. Determined conservation offive cysteine residues and the glycosylation domains in the amino [N-] terminal half emphasized the importance of the N-terminus for immunological and biological function of gD among alpha-herpesviruses. Presence of the most divergent domain of 17 aa residues at positions 168-184 and an additional cysteine residue at position 178 could be used as tools to distinguish the local Egyptian BHV-1 from other related herpesviruses. Findings of this work showed that genomic fingerprinting, based on endonuclease Hind III cleavage, and direct sequencing of the gD gene-derived PCR amplicons were relevant tools for genetic characterization of BHV-1 strains / isolates. The comparative genetic analyses conducted were useful to trace conservation of the local BHV-1 among related alpha-herpesviruses and to establish genetic tools for national-wide epidemiological studies and development of novel efficient BHV-1 vaccines