猪流行性腹泻病毒陕西渭南株的遗传变异

Genetic Variation Analysis of Porcine Epidemic Diarrhea Virus of WN Strain in Shaanxi Province

从陕西省渭南某规模化猪场采集疑似猪流行性腹泻(PED)仔猪病料进行病毒检测,旨在从基因遗传变异方面分析疾病发生的可能原因。通过RT-PCR从疑似仔猪20份小肠样品中检测到9份PED病毒阳性样品,并扩增出PED病毒M、ORF3和S基因的部分序列。序列分析结果表明,与CV777疫苗株对比,样品渭南(WN)株PEDV M基因高度保守,同源性为98.2%;ORF3基因存在11处碱基突变,同源性为98.2%;S基因突变较大,存在4个插入区域,分别是164~166、177~179、181~186和416~418nt,内分核心中和表位区(COE,499~638位氨基酸)存在9个氨基酸突变位点。遗传分析显示,WN株M基因与中国近期分离毒株亲缘关系较近;ORF3基因与同处在G1群中的中国毒株亲缘关系较近,而与CV777疫苗株亲缘关系较远;S基因与中国早期分离毒株及CV777疫苗株亲缘性较远,与当前的流行株亲缘关系密切。这些结果表明,WN株与CV777疫苗株相比,有明显的遗传变异倾向,可能导致目前PEDV疫苗免疫效果下降,PED疫情大规模流行。

Suspected piglet samples of porcine epidemic diarrhea virus（PEDV）infection were collected from one large-scale swine farms in Weinan,Shaanxi province,and then the possible reason for the occurence of PED in vaccine immune swine farm was detected by genetic variation analysis.It showed that nine positive PEDV samples were detected in 20 intestinal contents samples from suspected piglet by the method of RT-PCR.And then the sequence of the M gene,ORF3 gene,and partial Sgene of PEDV were amplified from the positive samples.Sequence analysis shows that M gene of PEDV in WN strain is relatively conserved,sharing 98.2% nucleotide sequence homology with the CV777 strain;11nt mutations were detected in the ORF3 gene,which sharing 98.2% nucleotide sequence homology with the CV777strain;the S gene in WN strain is variable with 4 insertions regions,including164-166 nt,177-179 nt,81-186 nt and 416-418 nt,and 9aa mutations in COE（499-638aa）region,which contains the epitope regions inducing the production of neutralizing antibodies for PEDV.Genetic analysis shows that the M gene in WN strain keeps a closer relationship with the isolated strains in China recently than other isolated strains;the ORF3 gene keeps a closer relationship with the isolated strains of China in G1 than the CV777 strain in G2;the Sgene has a closer relationship with the epidemic isolated strains recently than the CV777 strain and the isolated strains in China early times.It shows that obvious genetic variation has been occurred in WN strain of PEDV,which may be responsible for the poor immunity protection of vaccines for PEDV and the large-scale spread of PED in swine farms currently.