2006—2016年广西猪繁殖与呼吸综合征病毒流行毒株四个基因的进化动态分析

Evolutionary dynamics of Nsp2,ORF5,ORF6 and ORF7 genes of porcine reproductive and respiratory syndrome virus field strains in Guangxi Province from 2006 to 2016

为研究广西猪繁殖与呼吸综合征病毒（PRRSV）流行毒株的遗传进化情况,对2006—2016年间,来自广西各地的部分PRRSV阳性病料进行了病毒Nsp2、ORF5、ORF6、ORF7基因的扩增、测序及进化分析。结果,获得的Nsp2-1、Nsp2-2、ORF5、ORF6、ORF7基因的片段长度分别是1 667、1 649、603、525、172 bp,均为美洲型毒株;Nsp2、ORF5、ORF6、ORF7基因核苷酸及其推导的氨基酸序列的同源性分别为86.8%~100%和61.7%~100%、80.8%~100%和80.5%~100%、90.6%~100%和89.9%~100%、85.6%~100%和87.1%~100%;基于Nsp2、ORF5、ORF6及ORF7基因核苷酸序列分别绘制的进化树可将所有毒株分为6个亚群,而广西流行的PRRSV毒株主要分布在以JXA1株为代表的亚群6。Nsp2、ORF5、ORF6和ORF7的平均进化速率分别为1.69×10^-1、1.58×10^-2、9.71×10^-4、1.86×10^-3 substitutions/site/year。Nsp2基因是最容易发生变异的,其次是ORF5基因与ORF7基因,而ORF6基因最稳定。本研究为掌握PRRSV的分子流行病学及遗传进化规律提供了相关的基础数据。

To investigate the molecular evolution of porcine reproductive and respiratory syndrome virus（PRRSV）field isolates,the Nsp2,ORF5,ORF6 and ORF7 genes were amplified from positive clinical samples in Guangxi province from 2006 to 2016,then were sequenced and analyzed.In result,the acquired Nsp2-1 and Nsp2-2 fragments are 1667 and 1649 bp in size,respectively,ORF5 gene is 603 bp in size,ORF6 gene is 525 bp in size,and ORF7 gene is 372 bp in size.The PRRSV field isolates all belonged to North American genotype PRRSV（NA-PRRSV）.The homology identity of the nucleotide and deduced amino acid of Nsp2,ORF5,ORF6 and ORF7 genes were 86.8%-100% and 61.7% —100%,80.8% —100% and 80.5% —100%,90.6%—100% and 89.9%—100%,85.6%—100% and 87.1%—100%,respectively.The phylogenetic analysis showed that all the PRRSV isolates were divided into six subgroups based on Nsp2,ORF5,ORF6 and ORF7 genes,and most of the isolates from Guangxi Province belonged to subgroup 6,which was represented by JXA1 strain.The average substitution rates of Nsp2,ORF5,ORF6 and ORF7 genes of PRRSV isolates were1.69×10^（-1）,1.58×10^（-2）,9.71 ×10^（-4） and 1.86 ×10^（-3） substitutions/site/year,respectively,indicating thatNsp2 gene is the most easily mutated,followed by ORF5 gene,then by ORF7 gene,and ORF6 gene was the most stable among the four genes.The results of this study provided fundamental data for PRRSV molecular epidemiology and evolution.