Cloning and expression of IBD virus VP2 gene in prokaryotic expression system

Infectious Bursal disease (IBD), a highly contagious immunosuppressive viral disease, causes great economic loss to the poultry industry worldwide. The VP2 protein of the IBDV contains conformational and sequential antigenic epitopes responsible for inducing protective antibody response. In this study, IBDV genome responsible for encoding VP2 protein was amplified by RT-PCR and amplicon was confirmed by electrophoresis in 1% agarose gel and nested PCR which showed a band of 1.4 kb and 643 bp as expected. The RT-PCR amplified VP2 gene sequence was cloned in pGEMT^R easy vector. From there it was sub-cloned in prokaryotic expression vector pPROEX-HT-b at EcoRI site. VP2 gene insert and its orientation in pPRPEX-HT-b was confirmed by restriction digestion using EcoRI and PstI restriction enzymes, respectively. The expression of VP2 was induced in E. coli cells by 1 mM IPTG and culture was collected at 1, 2, 3, 4, 6, and 9 h post induction and cells lysed with 1 x Laemmli buffer were analysed for presence of VP2 by SDS-PAGE. Analysis revealed expression of 42 kDa VP2 protein. This was confirmed to be IBDV specific by western blot analysis using anti-IBDV chicken serum. Maximum expression was found at 6 h post IPTG induction.