马传染性贫血病毒驴白细胞弱毒疫苗株致弱过程中不同代次病毒LTR的进化分析

Genetic evolution of equine infectious anemia virus LTR region during attenuation in vitro

为揭示马传染性贫血病毒(EIAV)弱毒疫苗的减毒机理,本研究对EIAV弱毒疫苗株在体外驴白细胞传代过程中不同代次毒株的长末端重复序列(LTR)进行扩增和分析。结果显示:随着病毒在体外传代次数的增加,各病毒株遗传多样性逐渐增加,并与致弱前亲本株EIAVDV117的遗传距离逐渐增大;EIAV在体外传代过程中LTR的变异主要集中在U3区和R区的转录起始位点,但随着传代次数的增加,在负调节区丢失了GATA结合位点,并在增强子区出现了E-box基序。此外,传代初期低代次病毒株与后期的高代次弱毒株在负调节区的AP-1结合位点和转录起始位点以及TAR的起始位点存在明显差异。

Long terminal repeat（LTR） is an important region for equine infectious anemia virus（EIAV） genome in determining virulence and cell tropism.In this study,we examined the LTR populations in EIAV quasispecies of representative vaccine strains during its attenuation process in donkey monocyte-derived macrophages（MDMs） in vitro.The results demonstrated that the complexity and sequence diversity of LTRs in these quasispecies increased over passages in MDMs.The genetic distances of these MDMs-adapted EIAV strains to the parental virulent strain EIAVDV117 were gradually augmented with the increase of passages.Significant variations were identified in the U3 region and at the transcription start point.In addition,the loss of transcription-factor GATA motif in the negative regulating element（NRE） and acquirement of transcription factor binding motif E-box within the enhancer became more frequent as passage increased.Dramatic differences in the AP-1 motif of NRE,the transcription start position and the first residue of trans-activation responsive element were identified between the low passage pathogenic strains and the high passage attenuated strains.