Expression of VP2 gene protein of infectious bursal disease virus detected in Korea.

The VP2 gene DNA (1.4 kb in approximate) of a very virulent infectious bursal disease virus (vvIBDV) Chinju strain detected in Chinju, Korea was cloned into the bacmid, a baculovirus shuttle vector, through transposition of the gene from initially cloned pFastBacHTa plasmid, a baculovirus expression vector, and was subsequently expressed in Spodoptera frugiperda (Sf) cells. Biological properties of the expressed VP2 subunit protein were characterized to aid in the development of genetically engineered diagnostic reagents and vaccines against the vvIVDV. When the VP2 DNA-recombinant bacmid was transfected and propagated in the Sf cells, the cells showed no occlusion formation, which is a positive evidence for the insertion of the VP2 DNA into the polyhedrin gene of the bacmid, whereas the occlusions were observed in the cells infected by the Autographa californica nuclear polyhedrosis virus, a wild baculovirus. The expression of VP2 DNA was identified by strong positive reaction in fluorescent antibody test using chicken anti-IBDV serum. The VP2 protein was determined as a polypeptide band with Mr of 48 kDa by the sodium dodecyl-polyacrylamide gel electrophoresis for the lysate of the Sf cells infected with the recombinant bacmid. The VP2 protein was successfully purified from the cell lysate by Ni-NTA affinity chromatography. The expressed VP2 subunit protein reacted specifically with chicken anti-IBDV serum in Western blotting.