Formation of virus-like particles when the polyprotein gene (segment A) ofinfectious bursal disease virus is expressed in insect cells

The baculovirus expression vector system was used to examine the expression of the full-length infectious bursal disease virus (IBDV) segment A cDNA, which encodes the structural proteins in a polyprotein precursor that is au tocatalytically cleaved to VPX, VP3, and VP4. No VP2 was observed in lysate s of recombinant baculovirus infected cells indicating the lack of processi ng of VPX to VP2 in this system. Virus-like particles (VLP) were purified f rom the infected insect cells, and on negative staining electron microscopy , looked very similar to authentic IBDV particles in shape and size, sugges ting that processing of VPX to VP2 is not necessary for capsid assembly.