中文摘要：

为了掌握高致病性猪繁殖与呼吸综合征病毒（PRRSV）的变异情况,揭示该病的发生规律,根据GenBank登录的PRRSV基因序列设计引物,采用RT-PCR法对2005年-2010年间送检的282份病料进行了PRRSV核酸检测,对其中9份阳性样品进行了ORF5-7基因片段扩增和测序,所得序列与GenBank下载的PRRSV CH-1a、VR2332、HB-2、LV株的ORF5序列进行同源性比较,并与国内已发表的27株PRRSV ORF5序列进行遗传进化树分析,对GP5蛋白潜在糖基化位点和数目进行预测与分析。结果表明,病料PRRSV核酸阳性检出率为18.8%（53/282）;9个流行毒株同属于一个基因亚群,其ORF5序列同源性为95.0%-99.2%,氨基酸序列同源性为92.0%-99.0%;与4个参考毒株的ORF5序列同源性依次为93.4%-95.5%、87.6%-89.4%、91.2%-92.7%和63.0%-64.0%,氨基酸序列的同源性依次为91.0%-94.0%、85.6%-88.6%、89.6%-92.0%和54.7%-58.2%;GP5糖基化位点分析表明,5个糖基化位点有3株,4个糖基化位点有5株,3个糖基化位点有1株;这些糖基化位点分布在第30位-第55位氨基酸之间,以第44、55位点保守,另3个位点存在变异。我国猪群中PRRSV流行毒株变异幅度较大,GP5糖基化位点不同可能与毒力存在一定联系。

英文摘要：

In order to grasp the information of porcine reproductive and respiratory syndrome virus（PRRSV） genetic variation and to reveal the regularity of this disease development,a pair of primers were designed based on PRRSV sequences in GenBank.Two hundred and eighty-two samples collected from 2005 to 2010 were detected by reverse transcript polymerase chain reaction（RT-PCR）.ORF5-7 genes of nine PRRSV isolates were amplified from these positive samples and were sequenced.Sequences obtained were aligned with other strains of CH-1a,VR2332,HB-2 and LV from GenBank.Moreover,phylogenetic tree was constructed based on 27 PRRSV ORF5 genes,and the potential numbers of glycosylation sites of GP5 were done.The results showed that PRRSV positive rate was 18.8%（53/282）.Among the nine isolates,ORF5 gene sequence similarity was 95.0%-99.2%,and amino acid sequence similarity was 92.0%-99.0%.The alignment of 9 isolate ORF5 sequences with that of PRRSV strains CH-1a,VR2332,HB-2 and LV from GenBank,nucleotide sequence similarity were 93.4%-95.5%,87.6%-89.4%,91.2%-92.7%,63.0%-64.0%,respectively,and amino acid sequences similarity were 91.0%-94.0%,85.6%-88.6%,89.6%-92.0%,54.7%-58.2%.The nine isolates from 2005 to 2010 belonged to Northern American genotype subgroup.Analysis of glycosylation sites showed that three isolates contained five sites,four sites in other five isolates,only one isolate had three sites.These glycosylation sites localized between the 30th and 55th amino acids,and the 44th and 55th amino acids were relatively conservative,and the other three amino acids showed frequent variation.This study suggests that the epidemic strains of PRRSV in China have great variation;the differences of the glycosylation sites in GP5 protein between different isolates may be associated with the virus virulence.