2007-2010年河北省部分地区猪繁殖与呼吸综合征分子流行病学

Molecular epidemiology of the porcine reproductive and respiratory syndrome virus(PRRSV) in some areas of Hebei from 2007 to 2010

为了弄清河北省秦皇岛、唐山、廊坊、邯郸等部分地区流行的猪繁殖与呼吸综合征病毒(PRRSV)的ORF5和Nsp2基因变异情况,对采自以上地区在2007-2010年期间的临床发病猪肺组织,提取其RNA,通过RT-PCR扩增样本中PRRSV的ORF5和Nsp2基因,对目的基因测序,并以VR-2332、CH-la、MLV、LV、HB-1、HB-2、JXA1、HUB1、HEB1等毒株为参考序列,进行序列分析和进化树分析。扩增出42个ORF5基因,14个Nsp2基因,通过完整的ORF5和部分Nsp2基因序列比较分析发现所有毒株均为美洲型,且大多数毒株与国内2006-2007年间分离的JXA1、HUB1、HEB1等高致病力毒株同源关系很近。42个ORF5基因编码的氨基酸序列分析表明GP5蛋白的糖基化位点数量和位置已发生变异,主要中和表位存在氨基酸变异(L/F39→I39),与毒力相关的13位和151位点为强毒株的氨基酸特性(R13、R151)。14个Nsp2基因推导的氨基酸系列比较发现,1株PRRSV Nsp2基因未发生缺失突变,而剩余的13个毒株Nsp2基因均发生了氨基酸缺失,在481位和532～560位2处分别缺失1和29个氨基酸。系统发育进化树结果显示河北部分地区流行株分为2个小分支,1个毒株与HB-1聚为1支;河北流行株的大多数毒株在另一个分支,与高致病力毒株JXA1等聚为一支。本研究结果揭示了河北省部分地区流行的PRRSVORF5和Nsp2基因的变异特征,丰富了河北省的PRRSV分子流行病学资料,提示要针对ORF5和Nsp2基因的变异采取PRRSV的防控措施。

In order to examine the genetic variation of PRRSV ORF5 and Nsp2 gene, a total of 42 clinical samples （lungs） from the diseased pigs with PRRSV were collected from different places of Hebei province from 2007 to 2010. The ORF5 and Nsp2 gene of PRRSV were amplified by RT-PCR and sequenced. The sequences of 42 ORF5 and 14 Nsp2 genes were compared with those of VR-2332,CH-la,MLV,LV,HB-1,HB-2,JXA1, HUB1 and HEB1 strains. Sequence and phylogenetic analyses showed that all these 42 isolates belonged to the North American type. Most of the isolates had the closer genetic relationship with the highly pathogenic PRRSV isolates（such as JXA1, HUB1 and HEB1 etc. ）. Amino acid analysis of the GP5 protein revealed that isolates with 4 patterns of potential glycosylation site were observed and were variable in the primary neutralizing epitope（L/F^35→I^39）. 13 of 14 isolates exhibited two discontiguous sequence deletions that were identical to those of JXA1：a one-amino-acid （phenylala nine） deletion at position 481 and a 29-amino-acid deletion at positions 532-560 of Nsp2. In the phylogenetic tree, the Hebei prevail strains were divided into two different branches： 1 of all isolates were closely related to HB-1 and belonged to branch Ⅰ ;while others isolates were part of branch Ⅱ ,including highly pathogenic PRRSV JXA1. In conclusion,our data contribute to the understanding of molecular variation and epidemiology surveillance of PRRSV in Hebei province of China.