Genetic diversity of equine arteritis virus

Equine arteritis viruses (EAV) from Europe and America were compared by phy logenetic analysis of 43 isolates obtained over four decades. An additional 22 virus sequences were retrieved from GenBank. Fragments of the glycoprot ein G(L) and the replicase genes were amplified by RT-PCR, prior to sequenc ing and construction of phylogenetic trees. The trees revealed many distinc tive lineages, consistent with prolonged diversification within geographica lly separated host populations. Two large groups and five subgroups were di stinguished. Group I consisted mainly of viruses from North America, whilst group II consisted mainly of European isolates. In most instances, where t he geographic origin of the viruses appeared to be at variance with the phy logenetically predicted relationships, the horses from which the viruses we re recovered had been transported between Europe and America or vice versa, Analysis of the replicase gene revealed similar phylogenetic relationships although not all of the groups were as clearly defined. Virus strains CH 1 (Switzerland, 1964) and S1 (Sweden, 1989) represented separate 'outgroups' based on analysis of both genomic regions. The results of this study confi rm the value of the G(L) gene of EAV for estimating virus genetic diversity and as a useful tool for tracing routes by which EAV is spread. In additio n, computer-assisted predictions of antigenic sites on the G(L) protein rev ealed considerable variability among the isolates, especially with respect to regions associated with neutralization domains.