Universal influenza DNA vaccine encoding conserved CD4+ T cell epitopes protects against lethal viral challenge in HLA-DR transgenic mice.

The goal of the present study was to design a vaccine that would provide universal protection against infection of humans with diverse influenza A viruses. Accordingly, protein sequences from influenzaA virusstrains currently in circulation (H1N1, H3N2), agents of past pandemics (H1N1, H2N2, H3N2) and zoonotic infections of man (H1N1, H5N1, H7N2, H7N3, H7N7, H9N2) were evaluated for the presence of amino acid sequences, motifs, that are predicted to mediate peptide epitope binding with high affinity to the most frequent HLA-DRallelic products. Peptides conserved among diverse influenza strains were then synthesized, evaluated for binding to purified HLA-DRmolecules and for their capacity to induce influenza- specific immunerecall responses using human donor peripheral blood mononuclear cells (PBMC). Accordingly, 20 epitopes were selected for further investigation based on their conservancy among diverse influenza strains, predicted population coverage in diverse ethnic groups and capacity to recall influenza-specific responses. A DNA plasmid encoding the epitopes was constructed using amino acid spacers between epitopes to promote optimum processing and presentation. Immunogenicity of the DNA vaccinewas measured using HLA-DR4 transgenic mice and the TriGrid™ in vivo electroporation device. Vaccination resulted in peptide- specific immuneresponses, augmented HA-specific antibody responsesand protectionof HLA-DR4 transgenic mice from lethal PR8 influenza viruschallenge. These studies demonstrate the utility of this vaccine format and the contribution of CD4+ T cell responsesto protectionagainst influenza infection.