福建省新发猪圆环病毒3型分子流行病学调查及其Cap基因分子特征

Molecular epidemiological investigation of new porcine circovirus type 3 in Fujian province and molecular characteristics of its Cap gene

为了解2015―2017年福建省新发猪圆环病毒3型(PCV3)的流行现状、分子生物学特征和遗传演化规律,收集福建省不同地区186个猪场的267份疑似PCV3感染猪的组织病料进行分子流行病学调查,并对其Cap基因进行了遗传变异分析。结果显示,福建地区PCV3猪场总阳性率为30.11%,疑似样品总阳性率为21.72%,且呈逐年增高的趋势;17株PCV3福建分离株与其他17株国内外参考毒株Cap基因核苷酸序列及氨基酸序列同源性较高,分别为96.0%~100.0%和96.3%~100.0%,表明这些毒株可能有相同的进化来源;氨基酸多序列比对发现,Cap基因氨基酸序列最有特征性的是第168位(R→K)和173位(L→F)的氨基酸替换,该位点的突变可能是该地区流行的PCV3毒株的一个重要分子特征;同时,抗原性分析发现第173位(L→F)的突变还位于Cap蛋白的抗原表位区内。遗传进化树分析结果表明,17株PCV3福建分离株中有2株属于3a亚型,其余15株属于3b亚型,表明当前福建地区PCV3流行毒株主要为3b亚型。

To study the epidemic status,molecular characteristic and phylogenetic relationship of new porcine circovirus type 3(PCV3)in swine farms of the Fujian province.During 2015to 2017, 267suspected PCV3infected swine tissue samples were collected from 186large-scale pig farms in different areas of Fujian province to detect the PCV3by PCR,and theCap gene of 17PCV3isolates were sequenced and analyzed.The results showed that the total positive rate of PCV3in pig farms and suspected samples were 30.11% and 21.72%respectively,which showed an increasing trend year by year.The nucleotide sequences and amino acid sequences of Cap gene of 17PCV3isolates shared higher homology with other 17domestic and foreign reference strains,which were 96.0%-100.0%and 96.3%-100.0%,respectively.It suggested that these strains may have the same source of evolution.The multiple sequence alignment of amino acid revealed that the most characteristic change of Cap amino acid sequence were the amino acid substitution at position aa168(R →K)and aa173(L→F),and the mutation at these sites may be an important molecular'feature of the prevalent PCV3strain in this area.And antigenic analysis showed that the mutation at aa173(L →F)was also located in the antigenic epitope regions of Cap protein.Phylogenetic analysis of Cap gene showed that 2of 17PCV3isolates belonged to 3a subtype,and the remaining 15isolates belonged to ,3b subtype,indicating that the predominant PCV3strains in Fujian were mainly 3b subtypes.