Genetic and antigenic characterization of bovine viral diarrhoea virus type 2 isolated from cattle in India

Previous studies have shown that bovine viral diarrhoea virus type 1 (BVDV-1) subtype b is predominantly circulating in Indian cattle. During testing for exotic pestiviruses between 2007 and 2010, BVDV-2 was identified by real time RT-PCR in two of 1446 cattle blood samples originating from thirteen states of India. The genetic analysis of the isolated virus in 5′ UTR, Npro, entire structural genes (C, Erns, E1 and E2), nonstructural genes NS2-3 besides 3′ UTR demonstrated that the nucleotide and amino acid sequences showed highest similarity with BVDV-2. The entire 5′ and 3′ UTR consisted of 387 and 204 nucleotides, respectively, and an eight nucleotide repeat motif was found twice within the variable part of 3′ UTR that may be considered as a characteristic of BVDV-2. The phylogenetic analysis revealed that the cattle isolate and earlier reported goat BVDV-2 isolate fall into separate clades within BVDV-2a subtype. Antigenic typing with monoclonal antibodies verified the cattle isolate also as BVDV-2. In addition, cross-neutralization tests using antisera raised against Indian BVDV strains circulating in ruminants (cattle, sheep, goat and yak) displayed significant antigenic differences only between BVDV-1 and BVDV-2 strains. This is the first identification of BVDV-2 in Indian cattle that may have important implications for immunization strategies and molecular epidemiology of BVD.