两株分离自疫苗免疫猪场的PRRSV毒株的遗传演化分析

Genetic variation analysis of two PRRSV strains isolated from immunized intensive pig farms in China

猪繁殖与呼吸综合征(PRRS)是严重影响全球养猪业的传染病,疫苗免疫是防控该病的重要措施,但猪繁殖与呼吸综合征病毒(PRRSV)容易发生变异从而降低了免疫预防的效果。本研究从免疫了高致病性PRRS疫苗的发病猪场,分离出2株PRRSV毒株,并测定了其全基因组序列,分别命名为:PRRSV/pig/CHN/JTS/201606和PRRSV/pig/CHN/TG/201711。为了探讨临床中分离得到的这2株PRRSV毒株与该场所使用疫苗之间的关系,我们进行了全基因序列的遗传变异和重组分析,结果显示,这2个毒株都以PRRSV-pig-CHN-TJ-200-610(EU860248.1)疫苗毒株为骨架,其中PRRSV/pig/CHN/JTS/201606毒株在ORF1a蛋白的1429-1522 aa区域存在独特的94 aa的缺失,PRRSV/pig/CHN/TG/201711毒株在1013-1132aa区域存在120 aa的缺失。综上,本研究结果表明,PRRSV疫苗株基因组中核苷酸的突变和缺失产生的新毒株是造成猪场疫苗免疫失败的原因。

Porcine reproductive and respiratory syndrome(PRRS)is one of the most expensive diseases in the global pig industry.Immunoprophylaxis is one of the important measures to prevent and control the disease.However,the protective immunization effects could weaken by the variation of the virus.The genome-wide genetic variation characteristics of two PRRSV strains isolated from highly pathogenic PRRSV strains derived from vaccine strain immunized in different intensive pig farms were analyzed.The two PRRSV strains were named PRRSV/pig/CHN/JTS/201606 and PRRSV/pig/CHN/TG/201711.To further explore the relationship between the isolated virus strains and the vaccine strains used in this field,we then carried out the genetic variation and recombination analysis.And the results showed that PRRSV-pig-CHN-TJ-200610(EU860248.1)strain was the backbone of the three strains.Compared to all the PRRSV strains available at GenBank,PRRSV/pig/CHN/JTS/201606 strain had a unique 94aa deletion in the 1429-1522aa region of ORF1a protein.Compared to PRRSV-pig-CHN-TJ-200610,PRRSV/pig/CHN/TG/201711 had a 120aa deleted at 1013-1132aa region of ORF1a protein.In summary,this study showed that the deletions and nucleotide mutations in the whole genome of vaccine like PRRSV strains provide clues for the understanding of immune failure in the PRRSV vaccine immunized pig farms.