Variation in the bluetongue virus neutralization protein VP2.

To determine the extent and nature of the antigenic variation of four U.S.A. serotypes of bluetongue virus (BTV), the complete nucleotide sequence was determined for cDNA clones representing the L2 dsRNA of BTV serotype 13, the gene that codes for the outer capsid neutralization antigen (VP2). The predicted amino acid sequence of the protein was compared with the VP2 sequences of the U.S.A. serotypes of BTV-10, BTV-11 and BTV-17. Diagon comparisons, hydropathic plots and analyses of potential secondary structure of the four proteins indicated that all four VP2 proteins were structurally similar. However, the VP2 protein of BTV-13 was found to exhibit only 40% homology with the VP2 species of the other three viruses. The comparative sequence data indicated that there were regions of the proteins with greater variability than other regions, as expected for proteins that vary antigenically but are structurally similar.