Phylogeographical analysis of bovine herpesvirus 4: demonstration that inter strain recombination events took place after acquisition of the bo17 gene from an ancestor of the african buffalo

Recently, our phylogenetic study revealed that the Bovine herpesvirus 4 (BoHV 4) Bo17 gene has been acquired from an ancestor of the African buffalo around 1.5 million years ago, implying that cattle subsequently acquired BoHV 4 by cross species transmission (Markine-Goriaynoff et al., 2003, 77:1784-1792). In the present study, we pursued our investigation on the origin and the evolution of BoHV 4. Firstly, with the goal in mind to further precise the origin of the Bo17 gene, the C2GnT M gene sequence was determined for each subspecies of African buffalo and for three types of Asian buffalo. Phylogenetic analyses of these new sequences further supported our conclusion that the Bo17 gene has been acquired from an ancestor of the African buffalo, possibly of the Syncerus caffer caffer subspecies from East-Africa origin. Secondly, to investigate the phylogeographical relationships among BoHV-4 strains isolated from four different continents, phylogenetic analyses were performed based on six different regions distributed throughout the genome. Analyses of these regions revealed a clear correlation between the phylogenetic relationships among BoHV-4 strains and their geographical origin, leading to the concept of BoHV-4 geographical clades. These analyses also demonstrated that since the acquisition of the Bo17 gene, recombination events occurred at different time in the past between ancestors of actual geographical clades. These recombinations provided an opportunity to learn how after acquisition of the Bo17 gene in Africa around 1.5 million years ago, BoHV-4 has spread to the world to form phylogenetically related geographical clades.