Complete Genome Sequences of Three Sub-genotype 2.1b Isolates of Classical Swine Fever Virus in China

INTRODUCTION: Classical swine fever (CSF) has caused severe economic losses in pig production in many countries. Recent CSF outbreaks in China are mainly associated with sub-genotype 2.1 of CSF virus (CSFV). Although there is abundant information regarding 2.1 isolates, few data are available on whole-genome analysis. MATERIAL AND METHODS: The biological and genome characteristics of three recently emerged Chinese CSFV isolates, i.e. SD2014-1, SD2014-2, and SD2014-3, were fully analysed. RESULTS: Sequence analysis showed that the isolates shared 83.4%–95.0% nucleotide identity with eight other CSFV isolates. In addition, the 5′ untranslated region (5′UTR) and the non-structural (NS) proteins NS3, NS4A, and NS4B were more conserved than other regions of the genome. Phylogenetic analysis based on the complete genome sequences or full-length structural protein E2 gene sequences revealed that the three isolates belonged to sub-genotype 2.1b. In addition, several unique molecular characteristics of the 5′UTR, 3′UTR, and E2 were identified. CONCLUSION: The genomic variations of the three isolates will support further analysis of virulence determinants and the evolutionary trend of CSFV.