Preparation and immunogenicity studies of NvIBDV VP2-ferritin nanoparticles.

Background: Infectious bursal disease (IBD), caused by infectious bursal disease virus (IBDV), is a highly contagious disease that is prevalent worldwide and poses a significant threat to the poultry industry. While commercially available vaccines are used for prevention, IBD outbreaks remain frequent.

Objective: The continuous mutation of virulent strains and their ability to evade traditional vaccine protection complicate IBD control, which necessitates the development of novel vaccines and a deeper understanding of viral mutation mechanisms.

Method: Utilizing the self-assembly capability of ferritin (Fe), the hypervariable region (HVR) protein of a novel variant IBDV (NvIBDV) VP2 was displayed on the ferritin shell, forming regular nanoparticles. The full-length NvIBDV VP2 protein and the NvIBDV VP2-HVR-Fe fusion protein were prokaryotically expressed in E. coli and purified to prepare a VP2 protein vaccine and a VP2-Fe nanoparticle vaccine. An inactivated NvIBDV vaccine served as a control for evaluating immunogenicity and protection.

Results: Recombinant prokaryotic expression vectors pET-VP2-Fe (encoding VP2-HVR-Fe) and pET-VP2 (encoding full-length VP2) were successfully constructed. Soluble VP2-Fe and VP2 proteins were expressed and purified. Electron microscopy confirmed the formation of a cage-like nanoparticle structure for VP2-Fe. Immunization of SPF chickens with NvIBDV VP2-Fe nanoparticles induced a robust immune response characterized by high antibody titers and a significantly high protection rate against viral challenge.

Conclusion: The successfully constructed recombinant subunit nanoparticle vaccine, which displays the NvIBDV VP2 HVR on ferritin, effectively increased the antibody titer and provided superior immune protection. This approach offers a feasible strategy for developing novel IBDV subunit vaccines.