广西首例猪圆环病毒3型的发现及其衣壳蛋白序列分析

【目的】明确猪圆环病毒3型(Porcine circovirustype 3,PCV3)在广西猪群中的致病性及流行病学特点,为有效防控其暴发流行提供参考依据。【方法】采用PCR对广西某猪场腹泻死亡仔猪的病料样品进行PCV3检测,并对其唯一结构蛋白质(Cap)的结构进行同源模拟,构建遗传进化树;同时在线(http://www.cbs.dtu.dk/services/)预测Cap蛋白信号肽、糖基化位点和B细胞抗原表位。【结果】在广西某猪场腹泻死亡仔猪的病料样品中检测到PCV3。PCR扩增产物经核苷酸序列测定分析后截取Cap基因序列(645 bp),命名为PCV3/CN/Guangxi001/2017。PCV3/CN/Guangxi001/2017与13株国内PCV3毒株和5株美国PCV3毒株的Cap基因序列同源性分别在96.9%~99.4%和98.3%~99.5%,属于3b亚群;而与PCV1毒株和PCV2毒株的核苷酸序列同源性只有43.0%和45.8%,且B细胞抗原表位差异明显,在PCV1特有的B细胞抗原表位(92~103 aa)、PCV2特有的B细胞抗原表位(69~83 aa、117~131 aa和231~233 aa)及PCV1、PCV2共有的B细胞抗原表位(156~162 aa和179~192 aa)均无相似性。【结论】广西猪群中已存在PCV3感染,鉴于PCV2与PCV3间无交叉免疫保护特性,实际生产中应通过加强清洁消毒、灭鼠杀虫、定期监测、自繁自养等生物安全措施防控PCV3暴发流行。

The first report of porcine circovirus type 3 infection in Guangxi and sequence analysis of its capsid protein

Objective]The present study explored the pathogenicity and epidemiology characters of porcine circovi-rus type 3(PCV3)in Guangxi in order to provide the references for prevention and control of PCV3.Method]PCV3 were detected by PCR from epidemic materials of piglets died from diarrhoea. Homology modeling was conducted on its only structural protein(Cap),and phylogenetic tree was constructed. Signal peptide,glycosylation site and cell B epitope of Cap protein of PCV3 were redicteded on-line(http://www.cbs.dtu.dk/services/).Result]Epidemic materials of piglets died from diarrhoea was positive for PCV3. Its PCR amplification products was analyzed by nucleotide sequence,then gene sequence of Cap was intercepted(645 bp)and named PCV3/CN/Guangxi001/2017. PCV3/CN/Guangxi001/2017 shared 96.9%-99.4%and 98.3%-99.5%homology with Cap gene sequence of 13 PCV3 strains isolated from China and 5 PCV3 strains isolated from American respectively. However,its nucleotide sequence homology to PCV1 and PCV2 were only 43%and 45.8%,and differences in cell B epitope was obvious. Cell B epitope(92-103 aa)peculiar to PCV1,cell B epitope(69-83 aa,117-131 aa and 231-233 aa)peculiar to PCV and shared cell B epitope(156-162 aa and 179-192 aa)in PCV1 and PCV2 had no similarity.Conclusion]PCV3 has been emerging in pig herd in Guangxi. Since there is no cross immunity between PCV2 and PCV3,biosafety control measures including sterilization,insecticides,rodenticides,regu-lar monitoring and self-supportive should be performed in pig farm to prevent outbreak of PCV3.