传染性法氏囊病病毒结构的冷冻电镜初步分析

Preliminary structural analysis of infectious bursal disease virus by cryo-electron microscopy

为研究传染性法氏囊病病毒(infectious bursal disease virus,IBDV)的结构和基因组在其衣壳内部的包装信息,通过IBDV感染DF-1细胞并分离纯化得到完整的IBDV颗粒,利用单颗粒冷冻电镜技术获得了近生理条件下的IBDV在≈6.6?分辨率下的三维结构。结果显示:IBDV病毒衣壳是由260个VP2三聚体蛋白组成的单层衣壳,三角剖分函数T=13;在IBDV衣壳内部观察不到dsRNA基因组和RNA聚合酶的电子密度,这与其他dsRNA病毒如胞质型多角体病毒(cytoplasmic polyhedrosis virus,CPV)、蓝舌病毒(bluetongue virus,BTV)、轮状病毒(rotavirus,RV)明显不同。该结果暗示,IBDV可能采用了与其他dsRNA病毒不同的方式进行基因组组装、转录和复制,这为进一步揭示IBDV基因组的转录、复制和组装的分子机制及IBDV的起源和进化提供了结构学依据。

In order to investigate the structure of infectious bursal disease virus(IBDV)and how the doublestranded RNA(dsRNA)segments of IBDV are organized inside its capsid and how the genome segments are transcribed and assembled,we first obtained IBDV particles by infecting DF-1 cell with IBDV and purified the virus particles;we then determined the three-dimensional structure of IBDV using a single-particle cryo-electron microscopy(cryo-EM)at≈6.6?resolution.The results showed that IBDV possessed a T=13 single shell with 260 VP2 trimers.Unexpectedly no characteristic densities of dsRNA and RNA-dependent RNA polymerase were observed inside the IBDV capsid,which was in contrast to the structures of cytoplasmic polyhedrosis virus(CPV),bluetongue virus(BTV)and rotavirus(RV).These facts implicate that IBDV might adopt different mechanisms to organize,transcribe and assemble its genome segments,and that IBDV might originate and evolve differently from other dsRNA viruses.