Single mucosal vaccination targeting nucleoprotein provides broad protection against two lineages of influenza B virus

Abstract Nucleoproteinis highly conserved among each type of influenza viruses (A and B) and has received significant attention as a good target for universal influenza vaccine. In this study, we determined whether a recombinant adenovirus encoding nucleoproteinof type B influenza virus(rAd/B- NP) confers protection against influenza virusinfection in mice. We also identified a cytotoxic T lymphocyte epitope in the nucleoproteinto determine B- NP-specific CD8 T-cell responses. We found that B- NP-specific CD8 T cells induced by rAd/B- NPimmunization played a major role in protection following influenzaB virusinfection using CD8 knockout mice. To assess the effects of the administration routes on protective immunity, we immunized mice with rAd/B- NPvia intranasal or intramuscular routes. Both groups showed strong NP-specific humoral and CD8 T-cell responses, but only intranasal immunization provided complete protection against both lineages of influenzaB viruschallenge. Intranasal but not intramuscular administration established resident memory CD8 T cells in the airway and lung parenchyma, which were required for efficient protection. Furthermore, rAd/B- NPin combination with rAd/A- NPprotected mice against lethal infection with both influenza A and B viruses. These findings demonstrate that rAd/B- NPcould be further developed as a universal vaccine against influenza.