Identification and characterization of conserved and variable regions in the neutralization VP2 gene of bluetongue virus.

To determine the extent and nature of genetic variation among three serotypes of bluetongue virus (BTV), the nucleotide sequences of the outer capsid gene (L2) encoding the neutralization antigen (VP2) of serotypes BTV-11 and BTV-17 were determined. The predicted amino acids of the two proteins were then compared with that of BTV-10 (M. A. Purdy, H. Ghiasi, C. D. Rao, and P. Roy, 1985, J. Virol. 55, 826-830). The results indicated that although the three genes were closely related (70% conserved), the variation is extensive in comparison to the gene encoding the inner capsid polypeptide, VP3, which is 98% conserved in these serotypes (H. Ghiasi, M. A. Purdy, and P. Roy, 1985, Virus Res. 3, 181-190). Several regions with clustered amino acid substitution were identified. Based on predicted secondary structure and hydrophilicity, these variable regions represent potential antigenic sites. In contrast to the variable regions, other sequences and the overall VP2 structure (including cysteine, proline, and glycine residues) were highly conserved.