Abstract: To study the genetic varations of ORF5 and NSP2 genes of porcine reproductive and respiratory syndrome virus (PRRSV) isolates in Jiangxi province from 2013 to 2014, the complete ORF5 gene and subsequence of NSP2 gene of PRRSV were amplified by RT-PCR from lung samples of swine in Jiangxi.Sequence comparison and genetic variation analysis were conducted by DNAStar and Mega 6.0.The results showed that the homologies of ORF5 genes among the 12 PRRSV isolates were 83.7% to 99.8% and 82.1% to 99.5% in nucleotide and amino acid sequences, respectively.Compared to the reference strains JXA1, VR-2332 and LV, the homologies were 84.9% to 99.7%, 85.2% to 91.0% and 62.4% to 64.8%, respectively.Nsp2 sequences were amplified from positive samples and compared with the other published sequences, it indicated that 12 PRRSV isolates from Jiangxi belonged to Northern American genotype, 12 isolates had 30 amino acids discontinuous deletions in NSP2 protein which showed a typical structure as previously reported for highly pathogenic PRRSV.The phylogenetic tree of ORF5 of 12 isolates indicated that 10 PRRSV isolates were in the same branch with the highly pathogenic PRRSV, which showed that the highly pathogenic PRRSV had become the dominant PRRSV epidemic strain in Jiangxi.

Key words: porcine reproductive and respiratory syndrome virus (PRRSV); ORF5 gene; NSP2 gene; variation analysis