Isolation of bluetongue virus-1 from cattle in India and phylogenetic analysis of the complete coding sequence of the segment-2 gene.

The isolation of BTV-1 serotype from cattle in India and its phylogenetic relationship based on VP2 gene has been reported. Virus (JBP42/12/Ind) is isolated in BHK-21 cell line from blood sample tested positive for BTV antigen in sandwich ELISA from asymptomatic cattle. Full length VP2 gene of cattle isolate was amplified, cloned and sequenced. On BLAST analysis virus isolate was identified as BTV-1 serotype. Phylogenetic tree based on complete VP2 coding region segregated Indian isolates, Australian isolates and African/European isolates in three distinct clusters. Segregation of Indian BTV-1 isolates at close proximity to the monophyletic cluster of Australian BTV-1 isolates indicates the present isolate as "eastern topotype' of BTV. Multiple alignments of VP2 gene nucleotide sequences suggest that, Indian BTV-1 isolate is more closely related to Australian BTV-1 isolates; where 14.1% to 14.4% and 6.8% to 7.4% divergence was observed at nucleotide and deduced amino acid sequence level respectively.