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为了监测PRRSV流行毒株的基因变异情况,采用RT-PCR方法对四川省广元市某疑似猪繁殖与呼吸综合征病毒(PRRSV)发病猪场病料进行分子鉴定,获得1株PRRSV命名为SC-GY株,并对SC-GY株的Nsp2、ORF5及ORF3基因进行测序比对和系统进化树构建。结果表明,SC-GY株为Nsp2基因发生30个氨基酸不连续缺失、ORF3基因第17位插入1个丝氨酸(S)的美洲型高致病性PRRSV变异毒株,其Nsp2、ORF5、ORF3基因与VR2332、SC2012、CH-1a、JXA1、HUN4、NADC30、HENAN-XINX等国内外代表毒株的核苷酸同源性分别为70.3%~97.9%,82.4%~97.6%,83.1%~98.2%,编码氨基酸同源性分别为62.3%~96.3%,78.0%~95.7%,81.6%~96.5%;而与LV等欧洲型毒株的核苷酸同源性分别为18.9%,60.8%,63.7%,编码氨基酸同源性分别为14.0%,54.9%,57.2%。基因遗传进化树分析表明,SC-GY株与JXA1、TJ、HUN4等前期分离的毒株以及近期在四川周边分离的SC2012、SCwhn09CD、SCwhn14DY等毒株都相距较远。由此表明,该地区PRRSV在当前高频度活疫苗免疫下,流行毒株基因仍在不断变异,猪场应减少PRRSV活疫苗的免疫并加强对临床PRRSV流行毒株的监测。
In order to monitor the genetic variation of PRRSV epidemic strains, RT-PCR method was used to identify the pigs infected with the suspected porcine reproductive and respiratory syndrome virus (PRRSV) in Guangyuan, Sichuan Province. One strain of PRRSV named SC- GY strain. The Nsp2, ORF5 and ORF3 genes of SC-GY strain were sequenced and compared. The phylogenetic tree was constructed. The results showed that the SC-GY strain was a 30-amino acid deletion mutant of Nsp2 gene and a serine (S) -type mutant strain of PRRSV with serine (S) inserted at the 17 position of ORF3 gene. The Nsp2, ORF5 and ORF3 The nucleotide homology of the representative strains in domestic and abroad such as VR2332, SC2012, CH-1a, JXA1, HUN4, NADC30 and HENAN-XINX were 70.3% -97.9%, 82.4% -97.6%, 83.1% -98.2% The amino acid homologies were 62.3% -96.3%, 78.0% -95.7% and 81.6% -96.5%, respectively. The nucleotide homologies with European strains such as LV were 18.9%, 60.8% and 63.7% , Encoding amino acid homology 14.0%, 54.9%, 57.2% respectively. Genetic tree analysis showed that strains SC-GY and JXA1, TJ, HUN4 and other previously isolated strains, as well as SC2012, SCwhn09CD and SCwhn14DY strains isolated recently in Sichuan Province were far apart. This shows that the PRRSV in the region under the current high-frequency live vaccine immunization, the strains of the epidemic strains are still constantly mutated pigs should reduce the immune of PRRSV live vaccine and strengthen the clinical monitoring of PRRSV epidemic strains.