Phylogenetic comparison of the serotype-specific VP2 protein of bluetongue and related orbiviruses.

Regions of the VP2 gene from various bluetongue virus serotypes were sequenced and phylogenetic comparisons were performed. The sequences were characteristic for each BTV serotype and isolates of the same serotype could be grouped geographically, mimicking the topotyping characteristics of BTV VP3 gene sequences. PCR amplification and sequence analysis were used to show the close relationship between Caribbean BTV isolates and South African BTV isolates of the same serotype. Similarly, Australian BTV isolates showed a close genetic relationship with Asian BTV isolates of the same serotype. A multiple amino acid sequence alignment of fifteen BTV serotypes and other orbiviruses over a proposed major neutralization site showed this region (317 335 aa.) was highly variable and nucleotide sequences showed that BTV serotypes could be grouped into nucleotypes, or related serotypes, in broad agreement with the inter-relationships postulated by Erasmus (1990), using plaque-reduction tests.