Expression of IBD virus VP2 gene in eukaryotic expression system for use as DNA vaccine

Infectious bursal disease (IBD) is highly contagious immunosuppressive disease of great economic significance. The VP2 protein of the virus that bears both conformational and sequential virus neutralizing epitopes has been reported to induce protective antibody response. In this study, VP2 gene of Indian highly virulent field isolate have been cloned in pcDNA 3.1 (+) eukaryotic expression vector at EcoRI site. The orientation of the gene was confirmed by digestion with ApaI enzyme. The recombinant pcDNA plasmid having VP2 in right orientation (pcDNA.vp2.ibd) was grown in bulk and transfection grade plasmid was purified by QIAquick Midi columns. The purified plasmid was used to transfect 70–80% confluent Vero cells by calcium phosphate method. The transfected cell lysate was analysed by SDS-PAGE at 48 h and 72 h post-transfection which showed expression of 42 kDa VP2 protein. This protein reacted with anti-IBDV chicken serum in western blot confirming it to be IBDV specific. To check, if this recombinant in functionally active in vivo, this recombinant plasmid was injected in rabbits. It produced IBDV specific antibodies that reacted in indirect ELISA and dot-ELISA. The antibodies developed in rabbits after immunization did not neutralize the virus in cell culture indicating them to be non-neutralizing type. This construct is being evaluated for its efficacy in inducing protective immune response.