Virus-like particle vaccines of Infectious bursal disease virus expressed in Escherichia coli  are highly immunogenic and protect against virulent strain

Abstract Objectives Infectious bursal disease virus (IBDV) is a highly contagious, acutely infectious agent that causes immunosuppression in chickens. we expressed IBDV VP2 protein in Escherichia coli (E. coli) to develop an effective virus like particles (VLPs) vaccine and evaluated its immunogenicity. Methods The VLPs produced in E. coli were used as immunogen mixed with Montanide™ ISA 71VG, ISA 71RVG or white oil adjuvants. VLPs without adjuvant, commercial subunit vaccine, inactivated vaccine and attenuated vaccine were used as controls. These test vaccines were intramuscularly injected into 19-day-old SPF chickens, which were challenged with IBDV virulent strain at 30 days after vaccination. Results The adjuvants boosted antibody production, and the adjuvant groups (except white oil) produced higher antibody levels than the non-adjuvanted controls and the commercial vaccine groups. In terms of cellular immunity, the VLPs plus adjuvant combinations produced higher levels of cytokines, IL-2, IL-4, and IFN-γ, than the controls. Conclusion IBDV VLPs plus ISA 71RVG adjuvant can be used as an optimal vaccine combination for improving the immune efficacy of IBD subunit vaccines which can protect against virulent strain.