2015—2017年我国部分地区猪非典型瘟病毒的遗传变异分析

Phylogenetic Characterization of Atypical Porcine Pestivirus in Partial Regions of China during 2015-2017

猪非典型瘟病毒(atypical porcine pestivirus,APPV)是一种能引起仔猪先天性震颤的病原。为了解我国APPV感染状况、基因组以及遗传变异特征,采用套式RT-PCR方法,对2015—2017年我国22个省(自治区、直辖市)93个猪场的285份血清样本进行了APPV核酸检测和E 2基因序列分析;并对发病猪组织样本进行了APPV全基因组扩增与序列测定和遗传变异分析。结果显示,检测样本的APPV阳性率为25.26%(72/285,95%CI=20.3%~30.7%),且阳性率逐年升高;猪场APPV阳性率为38.71%(36/93,95%CI=59.7%~94.8%)。扩增出的35条APPV E 2基因的核苷酸序列相似性为83.4%~100.0%,推导氨基酸序列相似性为90.5%~100.0%。基于E 2基因的遗传变异分析显示,APPV临床毒株可被分为4个亚群,大多数国内APPV临床毒株可归入亚群1,与美国的000515株遗传关系较近;少数临床毒株与Bavaria S5/9、NL1 Farm1等欧美毒株同属于亚群2;6条测定序列被划分至亚群3;亚群4的成员均来自广东;其中亚群3与亚群4均由国内APPV临床毒株构成。全基因组序列遗传变异分析表明,全球APPV毒株可归为2大分支,本研究中测序的毒株CHheb1701与所有国外毒株属于同一分支,且与GX04/2017遗传关系最近,与美国毒株000515同聚为一簇;而第二分支中的毒株均来自我国广东省。以上研究表明,我国猪群中APPV感染已较为普遍,毒株多样且变异广泛,同时,也提示毒株可能有不同的来源,为进一步开展APPV的防控及相关研究奠定了重要基础。

Atypical porcine pestivirus(APPV)is a pathogen that causes congenital tremors in newborn piglets.To investigate the epidemical and phylogenetic characterization of APPV in China,285 serum samples collected from 93 pig farms distributed among 22 provinces,during 2015-2017,were detected for APPV,and the sequences of E 2 gene were further analyzed in this study.Meanwhile,the full-genomic sequencing and phylogenetic analysis on an APPV strain from a piglet with congenital tremors were also carried out.The results showed that APPV-positive rate of the tested samples was 25.26%(72/285,95%CI=20.3%to 30.7%),with a prevalence of 38.71%(36/93,95%CI=59.7%to 94.8%)at farm level,and the positive rate has increased year by year from 2015 to 2017.The nucleic acid homology of thirty-five APPV E 2 gene sequences obtained from the positive samples is 83.4%-100.0%and the similarity of deduced amino acids was 90.5%-100.0%.Phylogenetic analysis of the E 2 gene showed that they were highly diverse,and all listed strains could be divided into four subgroups.Most of the Chinese strains belong to subgroup 1,which are closely related to 000515 from the United States;and few sequenced strains are clustered into subgroup 2,together with European strains Bavaria S5/9 and NL1 Farm1,as well as ISDVDL2014016573 from the United States;six obtained sequences belong to subgroup 3;and all the strains in subgroup 4 are from Guangdong province;and the subgroups 3 and 4 are all composed of the Chinese strains.Whole-genomic sequence alignment shows that the identity of CHheb1701 with other referenced strains is 81.3%to 98.6%.The phylogenetic analysis indicates that all APPV strains could be divided into two main branches.The CHheb1701 is clustered into the branch containing all previous strains from the countries out of China and it is closed to Chinese virus GX04/2017 and the US strain 000515,which are clustered into the same subbranch.Meanwhile,another branch is composed of Chinese strains only from Guangdong province.The results above indicate that APPV is widely distributed in China,with wide variations,and the strains in China might be introduced from different resources.This study provides valuable information for further prevention and research of APPV.