我国两个不同地区猪繁殖和呼吸综合征病毒分离株ORF5基因序列比例

猪繁殖和呼吸综合征病毒(porcine reproductive and respiratory syndrome virus,PRRSV)为动脉炎病毒科成员之一,可引起感染母猪流产、死胎及断奶仔猪呼吸困难和死亡.该病毒呈球形,有囊膜,大小45nm～83nm,基因组为单股RNA,大小约15kb,有8个阅读框(ORF),分别编码2种非结构蛋白和6种结构蛋白,其中ORF5编码病毒糖基化膜蛋白(GP5)1,2].GP5蛋白为该病毒主要结构蛋白之一,含有病毒线性中和抗原表位.该蛋白可诱导感染细胞发生细胞凋亡3,4].目前,PRRSV有欧洲型和美州型两个血清型,其结构蛋白基因同源性为54%～70%5,6].不同美洲型PRRSV野毒株基因也有一定差异.由ORF5基因推导的氨基酸序列有4个相对保守区,但其N端和C端氨基酸残基可变性较大.由该基因构建的重组质粒具有良好免疫原性7,8].尽管一些欧美国家已普遍使用Resp PRRS弱毒疫苗,但该病仍时有发生9,10].我国于1996年亦已证实存在该病,并有不断蔓延趋势,已造成我国养猪业严重经济损失.

Comparison of the Open Reading Frame 5 Genome Sequence of Two PRRSV Wild Isolates from Different Regions in P. R. China

To elucidate the characteristics of molecular epidemiology of PRRSV in China, the nucleotide sequence of open reading frame 5 (ORF5) coding regions from two wild PRRSV strains, J1 and S1, isolated in northern and mid-eastern regions of China was determined by RT-PCR. Comparison showed that only 4 different bases between J1 and S1 strains resulted in 3 amino acid (aa. )changes in their deduced proteins. There were 3 and 2 different aa. between the deduced aa. sequences of J1, S1 strains and the American prototype ATCC virus VR2332 respectively, while there existed 16 and 15 aa. changes between the 2 isolates and the modified live vaccine strains derived from VR2332. The putative protein molecular weight, isoelectric point, signal region, glycosylation site and possible transmembrane helices of ORF5 of each strains were similar to that of VR2332 strain. These results showed that the two isolates belong to the same genotype and they may come from USA.