Indian Journal of Animal Research

Bluetongue (BT) disease caused by BT virus (BTV) is an acute haemorrhagic disease of domesticated and wild ruminants. 29 BTV serotypes have been identified so far throughout the world with 24 circulating in India conferring no cross protective immunity. Hence, the objective of the current study was to investigate the possibility of developing a recombinant subunit protein based vaccine for BT that is cross protective to all the known serotypes of BTV. VP2 is a major serotype determining protein and vaccination with VP2 was known to induce neutralizing antibody response. Since BTV circulates as 29 immunologically distinct serotypes, the current study aimed to identify conserved region of VP2. The amino acid sequence alignment showed that although VP2 was very variable among serotypes, several regions were relatively more conserved between serotypes; most conserved region (cVP2) of which was evident from 338-383aa. Moreover, selection pressure analysis revealed that all the codons in cVP2 region were under strong negative selection (dN/dS=0.16) suggesting strong structural and functional constraints on cVP2. In addition, two MHCI, MHCII each, and three B cell epitopes were predicted based on the physicochemical properties of the amino acids in cVP2 region. This suggests strong immunogenicity of cVP2 making it a suitable vaccine candidate. Taken together, cVP2 appears to be a promising target for a broad-spectrum subunit vaccine moiety for BT that can confer protection against the available serotypes of BTV. Since all the structural proteins of BTV will not be used in such subunit vaccines, observations from current study can also be extended to develop a marker vaccine for DIVA against BT.