Bursal Disease Viral Protein 2

Infectious bursal disease virus (IBDV) is a double-stranded RNA (dsRNA) virus of the Birnaviridae family. P2 and VP3 are the major viral structural proteins. They form the proteinaceous capsid, the structure of which was shown by cryoelectron microscopy and image reconstruction to exhibit a T=13 lattice (10, 13). The capsid shell is composed of homotrimeric subunits of VP2 and VP3; 260 VP2 trimers constitute the outer surface, while the 200 Y-shaped VP3 trimers line the inner surface. Consistently, VP2 carries the major neutralizing epitopes (2, 4), while it has been suggested that VP3, by virtue of its basic carboxy-terminal domain, interacts with the packaged dsRNA.