马传染性贫血弱毒疫苗株致弱过程中表面蛋白gp90的进化分析

Genetic evolution of the equine infectious anemia vaccine strain gp90 gene during attenuation process

为进一步研究马传染性贫血病毒(EIAV)弱毒疫苗的减毒机制,本实验对EIAV弱毒疫苗的原始种毒EIAVLN40、亲本病毒株EIAVDV、驴白细胞弱毒疫苗EIAVDLV121和EIAVDV减毒过程中的3个中间代次病毒(EIAVDLV32、EIAVDLV62和EIAVDLV92)的gp90基因进行测序分析。结果显示,适应白细胞培养的病毒株的进化距离更接近,与亲本病毒株处于进化树的不同分支。与强毒株相比,适应白细胞培养的病毒株在9个位点发生优势氨基酸的转换和V3区糖基化位点191NSSN194的缺失。此外,伴随EIAV毒力减弱的过程,有8个位点出现优势氨基酸残基的转换,在各代次病毒株中V4区具有糖基化位点237NNTW240和246NETW249的克隆所占的比例逐渐降低,其中EIAVDLV121的糖基化位点237NNTW240完全缺失。

Attenuated Equine infectious anemia virus（EIAVDLV121） is an effective lentiviral vaccine that was attenuated by successive passage in cultivated donkey monocyte-derived macrophages（MDMs）.The SU gene（gp90） may play an important role during virus attenuation.In this study,the genetic evolution of the vaccine SU gene was analyzed by comparing the gp90 sequences with that of the parental pathogenic strains of EIAVLN40 and EIAVDV,as well as 3 different passage of the virus during attenuation in MDMs.Phylogenetic analysis based on 102 sequences of the gp90 showed that the sequences of EIAVLN40,EIAVDV and MDMs-adapted EIAV were divided into three different branches,respectively.Compared with sequences from the pathogenic strains of EIAVLN40 and EIAVDV,the sequences from MDMs-adapted virus showed consistent conversions of amino acid residues at 9 sites and deletion of a N-glycosylation site（191NSSN194） in V3 region.Furthermore,amino acid residual conversions were also found at eight other sites with increased frequency during the passages.Two N-glycosylation sites（237NNTW240 and 246NETW249） in the V4 region were gradually lost in most of the clones from MDMs-adapted EIAV,of which the 237NNTW240 was deleted from all detected sequences of the vaccine strain EIAVDLV120.These data provided important information for the further study on biological characters of the Chinese EIAV attenuated vaccine.