Complete Genome Characterization of Bluetongue Virus Serotype 15 in China

PurposeThe aims of present study were to obtain the complete genome sequence of Chinese BTV-15 strain and analyze its evolutionary characterization.

MethodWhole-genome sequence of the BTV-15 strain (B105/YN/1996) isolated from China in 1996 was obtained by full-length cDNA amplification and high-throughput sequencing techniques.

ResultsSequence comparisons and phylogenetic analyses showed the genome length of B105/YN/1996 was 19 154 bp, with ten segments ranging from 822 bp (Seg-10) to 3 944 bp (Seg-1) encoding proteins with amino acid residues of 216 (NS3a) to 1 302 (VP1). Seg-1, -2, -3, -4 and -6 of the B105/YN/1996 were closely related to the equivalent genomic segments of BTV-15 strain isolated from Australia in 2012, while Seg-7, -8, -9 and -10 of the virus showed the highest sequence identity levels with Chinese BTV-15 strain V447, BTV-4 strain YTS4 and BTV-1 strain Y863, and Seg-5 of the B105/YN/1996 was the most close to BTV-1 strain IND1992/02 isolated from India. In the constructed phylogenetic tree, Seg-2 and Seg-6 of the B105/YN/1996 grouped into the Eastern topotype, and the Seg-3, Seg-4 clustered within the Far-eastern topotype, while Seg-7 and Seg-10 formed separated Eastern-1 and Eastern-2 topotype respectively.

ConclusionDifferent segments of the B105/YN/1996 displayed highly diverse in genetic evolution, suggesting that B105/YN/1996 was a gene recombination strain. The Seg-3, Seg-4, Seg-7 and Seg-10 of the B105/YN/1996 formed the unique topotype, suggesting the independent lineage evolution of the BTV-15 strain in China.