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

Abstract

In order to investigate the structure of infectious bursal disease virus (IBDV) and how the double-stranded 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 Å 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.

Keywords

• cryo-electron microscopy
• infectious bursal disease virus
• organization of dsRNA genome