Recombinant avian-derived antiviral proteins cIFITM1, cIFITM3, and cViperin as effective adjuvants in inactivated H9N2 subtype avian influenza vaccines

Vaccine adjuvants, serving as non-specific immune enhancers, play a pivotal role in the immunoprevention and control of animal diseases. This study utilized prokaryotic expression systems to express and purify chicken-derived cIFITM1, cIFITM3, and cViperin, which were then formulated as adjuvants with H9N2 avian influenza virus antigens to create inactivated vaccines. These vaccines were administered to SPF chickens to investigate their immunopotentiating functions. Additionally, the proteins were assessed for their ability to act as standalone immune enhancers. The results demonstrated that cIFITM1, cIFITM3, and cViperin significantly elevated serum hemagglutination inhibition (HI) antibody titers. Notably, when used individually, these proteins markedly enhanced the antiviral capabilities of challenged chickens, leading to alleviated clinical symptoms, reduced tracheal virus replication, diminished virus shedding, and lessened histopathological damage, with cIFITM1 exhibiting the most pronounced effect. Furthermore, the protective efficacy of two H9N2 recombinant virus inactivated vaccines supplemented with cIFITM1 adjuvant was validated, achieving a 100 % vaccine protection efficiency. In conclusion, cIFITM1, cIFITM3, and cViperin as adjuvants for influenza vaccines effectively inhibit virus replication and shedding, highlighting their significant potential in influenza prevention and control.