Abstract:

【Objective】 PRRSV were isolated from China in 2005-2007 to recognize the molecular biology character, phylogenetic relationship and the state quo of PRRSV prevalent isolates. 【Method】36 PRRSV isolates were isolated from 81 suspected clinical samples in 4 provinces which suffered PRRS in China in 2005-2007, ORF5 and Nsp2 genes of these isolates were sequenced and analyzed. 【Result】 36 isolates are North America PRRSV, which of ORF5 genes were composed of 603 nucleotides, encoded polypeptides of 200 amino acid residues, no gene deletion or inseration. Variations of the deduced amino acids of ORF5 gene mainly occurred at positions of 9 to 39. Nsp2 genes of PRRSV isolates were composed of 2940 or 2850 nucleotides. Compared with 15 PRRSV isolates, Nsp2 genes deletions of 21 PRRSV isolates were occured at positions of 481 and 532-596 amino acid. Compared with 14 PRRSV ORF5 and Nsp2 genes recorded by GenBank, most isolates show a close distance evolutionary relationship with Ch-1a, except for B02-2005, which may respect with PRRS vaccine virus. PRRSV isolates from different times show descendant homology compared with earlier isolates. 【Conclusion】 Based on amino acid sequence phylogenetic tree of ORF5 gene and Nsp2 gene, the 36 PRRSV isolates partly belong to subgroup Ⅳ represented by VR-2332, partly to subgroup Ⅰ represented by BJ-4, and partly to subgroup Ⅱ represented by Ch-1a. PRRSV ORF5, Nsp2 nucleotides and amino acids have taken place a larger variation, the genetic relationship of PRRSV isolates from different regions exist cross-cutting phenomenon, no obvious geographical characteristics.

Key words: porcine reproductive and respiratory syndrome virus, virus isolates, ORF5 gene, Nsp2 gene, genetic variation