Efficacy of CpG-ODN and Freund's immune adjuvants on antibody responses induced by chicken infectious anemia virus VP1, VP2, and VP3 subunit proteins

ABSTRACT Chicken infectious anemia virus is an important pathogen that causes severe anemia and immunosuppression in chickens, leading to serious economic losses worldwide in the poultry industry. However, no commercialized inactivated vaccine, subunit vaccine, or genetically engineered vaccine that is effective for controlling this virus is available. In this study, 3 recombinant plasmids were constructed to produce corresponding viral proteins in an Escherichia colisystem. The immune effects of the subunit proteins accompanied by CpG-ODN or Freund's immune adjuvants were evaluated and analyzed in systemic animal experiments. The results showed that VP1 induced the highest antibody titers with the participation of VP2 protein, indicating better protection under combined treatment, and the CpG-ODN adjuvant induced higher antibody titers and smaller dispersion of antibody titers than Freund's adjuvants. This is the first study to demonstrate that VP1 protein formulated with VP2 and CpG-ODN adjuvant can induce highest antibody titers and markedly enhance the immune response, indicating its promise as a vaccine candidate.