2019—2021年我国部分地区PRRSV ORF5基因遗传变异分析

Genetic Variation Analysis on ORF5 Gene of PRRSV in China

为了解2019—2022年我国南方地区猪繁殖与呼吸障碍综合征病毒(PRRSV)ORF5基因遗传变异情况,自广东、广西、湖南、江西4个省份的种猪场和育肥场,采集疑似PRRSV感染样品进行RT-PCR检测,并对部分阳性样品进行病毒分离培养和ORF5基因测序。结果显示:PRRSV总检出率为26.12%,其中育肥场场检出率(86.36%)高于种猪场(52.00%);共成功分离到97株病毒并对其进行了ORF5测序分析,发现Sublineage 1.8占比最高(51.55%),其次为Lineage 5(15.46%),Sublineage 1.5、Lineage 8、Lineage 3占比依次为13.40%、10.31%和9.28%;类NADC34毒株在2021年有3个省份(广东、广西和湖南)被首次检出,且当年检出率达13.40%。GP5蛋白分析结果显示,分离株中第13和151位氨基酸以及中和表位变异较多。对其中1株毒株进行重组分析发现,该毒株以类NADC30毒株为主要亲本,其多处基因组与JXA1和IA2014毒株发生了重组。结果表明:我国南方地区PRRSV流行较为普遍,尤其是在育肥猪群中;流行毒株类型较为复杂,但类NADC30毒株是优势毒株;流行毒株毒力位点及中和表位突变较为普遍,且部分毒株出现了重组,这有可能会影响毒株致病性以及现有疫苗的免疫保护效果,需要继续加强监测和研究。

In order to investigate the status of genetic variation of ORF5 gene of porcine reproductive and respiratory syndrome virus(PRRSV)in southern China from 2019 to 2022,samples suspected of PRRSV infection were collected from pig breeding farms and fattening farms in Guangdong,Guangxi,Hunan and Jiangxi for RT-PCR detection.For some positive samples,virus isolation and culture as well as ORF5 gene sequencing were performed.The results showed that the total detection rate of PRRSV was 26.12%,and higher in fattening farms(86.36%)compared to that in breeding farms(52.00%);a total of 97 strains were successfully isolated and ORF5 sequencing was carried out,it was found that,Sublineage 1.8 accounted for the highest proportion(51.55%),followed by Lineage 5(15.46%),and Sublineage 1.5,Lineage 8 and Lineage 3 accounted for 13.40%,10.31%and 9.28%respectively.NADC34-like strain was firstly detected in Guangdong,Guangxi and Hunan in 2021,and the detection rate in that year was 13.40%.It was found that,by GP5 protein analysis,the amino acids at the positions of 13th and 151th and neutralizing epitopes of the isolates varied greatly.Recombination analysis of one isolate showed that,NADC30-like strain was the major parent,and its multiple places of genomes recombined with JXA1 and IA2014 strains.In conclusion,PRRSV was widely prevalent in southern China,especially in fattening pigs;complex types of prevalent strains were observed,but NADC30-like strain was the dominant strain;mutations in virulence sites and neutralizing epitopes of PRRSV were commonly observed,and some strains had recombined,which might affect the pathogenicity of the strains and the immune protection effect of current vaccines,and should be further monitored and studied.