闽粤地区PPV7与PCV2的混合感染调查及PPV7 Cap基因的遗传变异分析

Investigation of Co-infection of PPV7 and PCV2 and Genetic Variation Analysis for PPV7 Cap Gene in Fujian and Guangdong

【目的】调查闽粤地区猪细小病毒7型(Porcine parvovirus type 7,PPV7)与猪圆环病毒2型(Porcine circovirus type 2,PCV2)的混合感染情况,并掌握两地PPV7 Cap基因的分子遗传特征。【方法】收集闽粤地区69个猪场的432份发病猪血液进行PPV7和PCV2的PCR检测,并对阳性样品的PPV7 Cap基因进行克隆测序。利用DNAStar软件对两地PPV7 Cap基因的核苷酸序列及氨基酸序列进行分析,并采用Mega 7.0软件绘制遗传进化树。【结果】闽粤地区PPV7阳性率为21.99%(96/432),场阳性率为53.62%(37/69),PCV2阳性率为54.17%(234/432),两者共感染率为13.43%(58/432)。应用PCR方法成功扩增出17株PPV7 Cap基因序列。核苷酸相似性分析发现,17株PPV7 Cap基因序列之间相似性在85.6%~100%,与国内外参考毒株相似性在85.8%~99.0%。氨基酸序列比对发现,17株PPV7 Cap蛋白氨基酸序列相似性为87.6%~100%,与国内外参考毒株间的氨基酸相似性为82.6%~98.7%。基于Cap基因的遗传进化分析表明,PPV7可分为PPV7a~PPV7e 5个主要的进化分支,其中9株属于PPV7a进化分支,3株属于PPV7b分支,4株属于PPV7c分支,仅有1株属于PPV7e分支。【结论】PPV7在闽粤地区广泛流行,并且与PCV2有较高的共感染率,可能为猪圆环病毒相关疾病(Porcine circovirus associated disease,PCVAD)的潜在致病因子。闽粤两地PPV7毒株具有丰富的遗传多样性,而PPV7a分支毒株为目前的主要优势毒株。本研究为闽粤地区PPV7的防控及疫苗研究提供理论依据及数据参考。

【Objective】To investigate the co-infection situation of Porcine parvovirus(PPV7)and Porcine circovirus type 2(PCV2)in Fujian and Guangdong,and to understand the molecular genetic characteristics of PPV7 Cap gene.【Method】The blood sample of 432 infected pigs from 69 pig farms in Fujian and Guangdong were collected to detect PPV7 and PCV2 by PCR.The PPV7 Cap gene of positive samples was cloned and sequenced.The DNAStar software was used to analyze the nucleotide and amino acid sequences of PPV7 Cap gene,and Mega 7.0 software was used to draw the genetic evolution tree.【Result】The results showed that the positive rate of PPV7 was 21.99%(96/432),the positive rate of farms was 53.62%(37/69),and the positive rate of PCV2 was 54.17%(234/432),and the co-infection rate of PCV2 and PPV7 was 13.43%(58/432).The 17 PPV7 Cap gene sequences were amplified using PCR.Nucleotide homology analysis revealed that the homology of the 17 PPV7 Cap gene sequences was 85.6%-100%,and the homology with reference strains was 85.8%-99.0%.Amino acid sequence comparison analysis revealed that the amino acid homology of the 17 PPV7 Cap protein sequences was 87.6%-100%,and the amino acid homology with reference strains was 82.6%-98.7%.Phylogenetic analysis of Cap gene showed that PPV7 could be divided into five main evolutionary branches of PPV7a-PPV7e,among which 9 isolates belonged to PPV7a subtype,3 isolates belonged to PPV7b subtype,4 isolates belong to PPV7c subtype,and only 1 isolates isolates belonged to PPV7e subtype.【Conclusion】This study indicated that PPV7 was widely prevalent in Fujian and Guangdong regions,and had a high co-infection rate with PCV2,which might be the pathogenic factor of Porcine circovirus associated disease(PCVAD).The genetic diversity of PPV7 isolates was abudant in both regions,and PPV7a was the dominant strain at present.The findings of this study provided theoretical basis and data reference for PPV7 prevention and control and vaccine research.