1株重组型番鸭细小病毒的分子特征解析

Unveiling the molecular characteristics of a recombinant Muscovy duck parvovirus

为了对1株番鸭细小病毒(MDPV)分离株NY18株的分子特征予以准确揭示,通过设计重叠PCR引物,扩增NY18株的完整基因组并进行了测序。结果显示,NY18株基因组由5071个碱基组成,5′和3′端末端倒置重复序列(inverted terminal repeats,ITR)均由424个碱基组成,其外侧385个碱基形成回文发夹结构。Simplot 3.5.1和RDP4软件分析表明,NY18株经历了2次重组事件,第1次重组产生在VP3基因的1.1 kb区域,第2次重组事件产生在P9启动子至Rep基因上游约100 bp区域内。2次重组均以经典型MDPV YY株作为主要亲本,而经典型鹅细小病毒(GPV)强毒株DY16和鹅胚化的弱毒疫苗株SYG61v作为次要亲本参与了重组。NY18株的ITR与经典型MDPV FM和YY株的同源性为97.9%和99.1%,而与GPV强毒株YZ99-6的同源性仅有86.0%,表明NY18株ITR仍来自于经典型MDPV。以VP1基因1.1 kb重组区片段构建遗传进化树,NY18株与经典型GPV处于同一分支,而以非重组区的Rep1基因1774 bp和VP1基因氨基端694 bp、羧基端405 bp片段分别构建遗传进化树,NY18株则与经典型MDPV处于同一分支。结果表明,NY18株既不同于经典型MDPV也不同于GPV,其本质是1株重组型的MDPV。

In order to unveil the molecular characteristics of the Muscovy duck parvovirus strain NY18,the complete genome was amplified using the overlapped PCR primers and sequenced.The genome of the NY18 strain is composed of 5071 nucleotides.The inverted terminal repeat(ITR)at the 5′and 3′end is composed of 424 nucleotides,among which the 385 bases on the outside forms the palindromic hairpin structure.Recombination analysis using Simplot 3.5.1 and RDP4 software showed that the NY18 strain genome experienced two recombination events.The first recombination event occurred in the 1.1 kb region of the VP3 gene,and the second recombination event occurred in a region spanning from the P9 promoter to the upstream 100 bp of the Rep gene.In both recombinant events,the classical MDPV YY strain acted as the main parent,and the classical virulent strain DY16 and the attenuated vaccine strain SYG61 v of GPV acted as the minor parents,respectively.The ITR nucleotide homology of strain NY18 with classical MDPV FM and YY strain was 97.9%and 99.1%,respectively,which was significantly higher than that of the virulent strain YZ99-6 of GPV(86.0%),demonstrating that ITR of strain NY18 still originated from the classical MDPV.In the phylogenetic tree constructed with the 1.1-kb recombinant region of the VP1 gene,strain NY18 lied in the same branch with all the classical GPV strains,while in three phylogenetic trees constructed with the non-recombination genetic region,including the 1774 bp fragment of the Rep1 gene,and the N-terminal 694 bp and the C-terminal 405 bp fragments of the VP1 gene,strain NY18 grouped with all the classical MDPV strains.Collectively,the present study demonstrated that NY18 strain is different from the classical MDPV and GPV strains and is a recombinant MDPV in essence.