我国猪繁殖与呼吸综合征病毒NT0901分离株分子特征

猪繁殖与呼吸综合征病毒(PRRSV)是目前引起国内外养猪业严重经济损失的重要病原之一,病毒基因和毒力变异较大。PRRSV NT0801株分离自我国发病猪群,毒力较强,但NSP2基因不存在高致病性PRRSV 30个氨基酸的缺失。为了进一步阐明该分离株的分子特征,本研究对该毒株全基因序列进行了测定和分析,结果该毒株基因组全长15 439 bp,其中包含29 nt Poly(A)。与高致病性PRRSV毒株JXA1比较,核酸序列同源性为96.7%,推导的GP3和GP5氨基酸序列同源性分别为97.2%和98.5%,但NSP2基因无30个氨基酸的缺失;与传统型毒株ch-1a比较,推导的GP3和GP5氨基酸序列同源性分别为92.9%和91.5%;基因进化树分析结果显示其介于高致病性和传统PRRSV毒株之间。与其它不同毒力PRRSV分离株基因序列比较,未发现明显重组信号。不同毒力毒株氨基酸残基比对分析结果显示,15个位点潜在毒力相关氨基酸残基中,该毒株有9个与高致病性PRRSV毒株一致,3个与高致病性PRRSV毒株不同,但与传统型和JXA1疫苗株相同,1个位点只与JXA1疫苗株相同,2个与其它毒株都不相同。表明该分离株与高致病性PRRSV密切相关,PRRSV流行毒株变异与基因突变有关,从而为该病毒毒力基因定位研究奠定了基础。

Molecular characterization of a porcine reproductive and respiratory syndrome virus isolate NT0801 from China

Porcine reproductive and respiratory syndrome virus (PRRSV) is one of the important pathogens causing serious economic losses to swine industry worldwide. PRRSV is genetically and pathologically heterogenous. PRRSV NT0801 strain was isolated in a pig farm with clinical signs and had high pathogenesis in piglets. But its NSP2 gene did not have 30 amino acids deletion as highly pathogenic JXA1 strain. To elucidate the genetic characteristics of PRRSV NT0801 strain, the full-length genome of NT0801 isolate was sequenced and analyzed. The results showed that the genome of PRRSV NT0801 was 15439bp in length, including 29nt Poly(A) tail. Compared with the highly pathogenic JXA1 strain, it had the nucleotide sequence identity of 96.7%, amino acid sequence homology of 97.2% and 98.5% in GP3 and GP5, respectively. Phylogenetic analysis indicated that NT0801 isolate was located between the traditional strain and the highly pathogenic strain. But no obvious recombination signal was observed, compared with other PRRSV isolates with different virulence. The alignment of amino acid sequence of NT0801 with other PRRSV isolates demonstrated that three out of nine sites, being consistent with the highly pathogenic strain, were different from those in highly pathogenic while same as those in traditional strains and JXA1 vaccine strain. And one out of 9 sites was same as that of JXA1 vaccine strain exclusively, two out of 9 sites were different from all the strains. These results indicated that PRRSV NT0801 strain is closely related to highly pathogenic PRRSV, although there has no 30 amino acids deletions in NSP2 region. The epidemic PRRSV strains variation results from the gene mutation. It should be useful for studying on the virulence genes located in different ORFs of PRRSV in the future.