A T cell-based ubiquitin-mediated mRNA vaccine provides cross-protection against H1N1 and B influenza viruses in mice

Given the persistent antigenic drift of seasonal influenza viruses and the continuous threat of emerging pandemics, there is an urgent necessity to develop novel influenza vaccines capable of conferring broad-spectrum immunity against multiple viral subtypes. CD8⁺ T cells provide a promising approach to achieving such protection because of their ability to recognize conserved internal antigens. Particularly, the highly cross-reactive internal nucleoprotein of influenza virus demonstrates remarkable efficacy in safeguarding against infection caused by diverse strains. Ubiquitination modification is critical for the differentiation and functionality of CD8⁺ T cells, thereby modulating the immune response. In this study, three mRNA vaccines were designed using the influenza virus nucleoprotein as an immunogen, including wild-type N protein (WT-N), ubiquitinated wild N protein (Ub-WT-N), and ubiquitinated rearrangement N protein (Ub-Re-N). After immunizing C57BL/6 mice, both WT-N and Ub-WT-N vaccines elicited antibody production, while the Ub-Re-N group exhibited enhanced cellular immune response without inducing antibody production. Subsequently challenged with influenza viruses, the vaccinated mice showed significant protection against mortality and weight loss caused by H1N1 and influenza B strains. Notably, depletion of CD8⁺ T cells led to a substantial reduction in the protective efficacy of the Ub-Re-N vaccine. In conclusion, the mRNA vaccine encoding Ub-Re-N confers potent defense against influenza virus infection through induction of a robust antigen-specific T cell response.