Abstract
Developing a more effective seasonal influenza vaccine is necessary to reduce the global health and economic burdens caused by influenza virus infections. Next-generation influenza vaccines using computationally optimized broadly reactive antigen (COBRA) methodology elicit protective immune responses against strains over multiple seasons. Most influenza virus vaccines are currently administered intramuscularly and elicit systemic immune responses. Intranasal administration elicits mucosal immune responses at the site of infection, as well as systemic immunity. It was hypothesized that COBRA-derived hemagglutinin and/or neuraminidase recombinant protein combined with the c-di-AMP adjuvant will elicit broadly reactive mucosal and systemic immune responses when administered intranasally against seasonal influenza viruses in mice and ferrets that were pre-immune to influenza viruses. Multivalent COBRA-based antigens were formulated with c-di-AMP adjuvant and administered intranasally. Animals were vaccinated with either a trivalent COBRA H1, H3, and influenza B rHA vaccine, bivalent COBRA N1 and N2 rNA, or a pentavalent mixture of COBRA rHA and rNA antigens. Mice and ferrets vaccinated with COBRA rHA proteins had sera with HAI activity against a panel of influenza A and B strains isolated from multiple seasons. Vaccines containing rHA in the formulation had less weight loss and viral lung titers compared to animals vaccinated with rNA only or mock vaccinated animals following challenge. Pentavalent COBRA HA and NA vaccines delivered intranasally were the most effective vaccine combination tested with the broadest protective immunity against drifted seasonal influenza viruses.