The mRNA-LNP Vaccine Encoding Viral VP2 Confers Effective Protection Against Very Virulent Infectious Bursal Disease Virus (vvIBDV)

Infectious bursal disease (IBD) is an acute, highly contagious, and immunosuppressive disease of poultry caused by the infectious bursal disease virus (IBDV). For more than 30 years, the very virulent IBDV (vvIBDV) characterized by high mortality has been widely prevalent worldwide, inflicting considerable economic losses on poultry-producing regions and thereby hampering the healthy development of the industry. However, the existing live vaccines carry the risk of restoring virulence and are susceptible to interference from maternal antibodies, while inactivated vaccines often result in insufficient protection. Therefore, it is urgent to develop novel vaccines with improved safety and efficacy. In this study, an mRNA vaccine encoding the VP2 protein of vvIBDV was developed for the first time. Efficient protein expression of mRNA-HLJVP2 was confirmed through in vitro transfection experiments. Immunization experiments in chickens demonstrated that the mRNA-HLJVP2-LNP with three different doses induced specific neutralizing antibodies and significantly increased the proportions of IL-4-secreting CD4+ T cells and IFN-γ-secreting CD8+ T cells. In the following challenge experiment, the mRNA-HLJVP2-LNP immunization groups exhibited good protective efficacy, with the single immunization group (20 μg dose) providing effective protection for chickens from death and bursa lesions induced by vvIBDV challenge. This study provides a promising candidate vaccine for the control of the vvIBDV and highlights its potential for clinical application in the prevention of IBD.