A Recombinant Subunit Vaccine against Chicken Infectious Anemia Virus Elicits Protective Immunity via VP2-assisted VP1 Refolding

Chicken infectious anemia virus (CIAV) is a globally significant immunosuppressive pathogen causing substantial economic losses to the poultry industry, with particularly severe outbreaks in China in recent years. The limitations of existing vaccines, such as the residual virulence of live attenuated vaccines, necessitate the development of novel, safer, and more effective vaccine strategies. This study aimed to develop a cost-effective subunit vaccine targeting the key viral antigens VP1 and VP2. The VP1 and VP2 genes were cloned and expressed in E. coli. A major challenge was overcome by innovating a “VP2-assisted co-refolding” strategy: VP1, which primarily formed inclusion bodies, was denatured and then refolded via gradient dialysis in the presence of soluble VP2, leveraging its natural chaperone-like function to restore conformational epitopes. The refolded VP1/VP2 protein complexes, emulsified at different ratios, were used to immunize 3-day-old SPF chickens, followed by challenge with a virulent CIAV strain. The results demonstrated that the vaccine formulation with a VP1:VP2 ratio of 1:1 provided the best protection, achieving a 71.4% (5/7) protective efficacy. This was evidenced by significantly reduced thymic atrophy, a higher thymus index. Our findings validate the feasibility of using an economical prokaryotic expression system coupled with a rational protein refolding strategy to produce a protective subunit vaccine candidate against CIAV, offering a promising alternative for disease control.