A consensus HA DNA vaccine targeting clade 2.3.4.4 H5Nx influenza viruses provides broad cross-clade protection in mice and ferrets.

Abstract

Recurrent outbreaks of highly pathogenic avian influenza (HPAI) H5Nx viruses in birds pose a threat to human health due to their zoonotic potential. This underscores the urgent need for effective vaccines to mitigate the pandemic risk from evolving H5Nx viruses. We developed a DNA vaccine encoding a consensus hemagglutinin (HA) from clade 2.3.4.4 H5Nx viruses [pGX-27/HA (2.3.4.4)] and evaluated its immunogenicity and protective efficacy in mice and ferrets. Vaccination elicited strong neutralizing antibody and T cell responses, protecting mice against lethal challenge with homologous viruses. Unlike formalin-inactivated vaccines, the DNA vaccine conferred CD8⁺ T cell-mediated cross-protection against divergent clades 2.2.1.2 and 2.3.2.1. In ferrets, the vaccine induced neutralizing antibodies and conferred protective immunity, indicating translational potential. These results suggest that the HA (2.3.4.4) DNA vaccine provides broad immunity against multiple H5Nx clades and offers insights for developing next-generation vaccines against potential zoonotic influenza threats.