A digitally immune-optimized influenza vaccine broadly neutralizes swine and human H1N1 influenza viruses and protects from heterologous challenge.

Influenza A virus (IAV) zoonotic transmission and continuous evolution in multiple host species heighten the risk of emerging novel strains at the human-animal interface. Digitally immune-optimized hemagglutinin (HA), neuraminidase (NA), and matrix-2 (M2) vaccine antigens were engineered and combined as a single DNA expression construct (DVX-H1N1) to maximize immune responses to human seasonal, pandemic, and zoonotic H1N1 IAVs. Immunization of mice with DVX antigens induced broad neutralizing antibody responses to human- and swine-origin H1N1 isolates. The DVX-H1N1 candidate was then evaluated in the well-recognized swine challenge model for human influenza in comparison to two benchmark controls representing conventional whole inactivated virus (WIV) vaccines that were either homologous or heterologous to the H1N1 pandemic 2009 subclade 1A.3.3.2 challenge strain, A/swine/England/1353/2009 (H1N1). Serology demonstrated that DVX-H1N1 immunization induced immune responses across a broad spectrum of human and swine H1N1 strains representing antigenic drift and reassortment. Following intranasal virus challenge, nasal shedding of viral RNA was significantly suppressed in the DVX-H1N1 and the homologous control WIV vaccinated groups in comparison to naive controls and the heterologous WIV vaccinated groups. These findings demonstrate that in both swine and mouse models, the DVX-H1N1 vaccine induced broad immune responses and, in pigs, controlled viral infection comparable to conventional strain-matched, but unlike mismatched WIV vaccines.

IMPORTANCE

Influenza A virus (IAV) transmission across the animal-human interface is a recognized global health threat. Swine are a key animal reservoir enabling the emergence of novel strains with pandemic potential, posing a threat for animal health and zoonotic spillover to humans. Vaccination remains the most effective intervention against influenza, with current strategies relying on human seasonal strain selection guided by biannual World Health Organization (WHO) recommendations. This approach is challenging owing to viral antigenic drift, reassortment in animal reservoirs, and imperfect antigenic matching between vaccine strains and circulating viruses. These factors reduce vaccine effectiveness and increase threats posed by emerging novel strains, emphasizing the need for next-generation influenza vaccines that improve vaccine-mediated protection and longevity of immunity against an evolving virus. We describe a proof-of-concept digitally immune-optimized antigen vaccine platform with broad immunogenicity and robust efficacy in the swine model, a translational system with the potential to mitigate influenza threats at the human-animal interface.