Evaluation of immune protective efficacy of recombinant adenovirus vector vaccine containing RBS of influenza virus subtype H1N1.

The current seasonal influenza vaccine is only 20%-60% effective on average, and its protective effect lasts only 6-8 months. Additionally, some viruses are prone to antigenic drift, which prevents the vaccine from being fully effective. Furthermore, due to antigenic drift, they are unable to effectively address the threat of pandemics, continuing to pose a threat to global health. There is an urgent need to develop vaccine strategies that go beyond traditional vaccines. The human adenovirus type 5 (Ad5) vector is biologically safe and capable of inducing strong systemic and mucosal immune responses. Currently, the Ad5 vector is widely utilized in vaccine development against various pathogens. Here, we developed and evaluated an adenovirus-based influenza vaccine (rAd5-GFP-RBS). This vaccine focuses on the receptor-binding site (RBS) of hemagglutinin. The vaccine was delivered intranasally to C57BL/6J mice and induced robust systemic and mucosal immune responses, evidenced by significantly higher IgG levels in serum and bronchoalveolar lavage fluid. Notably, the IgG antibody titer in the alveolar lavage fluid of the rAd5-GFP-RBS group was significantly higher than that in the PBS group (∗∗∗p < 0.001). Following H1N1 PR8 challenge, vaccinated mice exhibited significantly enhanced survival, significantly reduced weight loss, and decreased lung pathology compared to controls. Histopathology and immunohistochemistry confirmed lower viral antigen levels in vaccinated mice. Measured influenza-specific antibodies demonstrated strong immune response, highlighting the vaccine's potential for excellent protective immunity. These findings support rAd5-GFP-RBS as promising candidate for influenza protection, providing a platform for rapid vaccine development against emerging strains. Further optimization could improve vaccine durability and efficacy.