Optimization of a liver Trm cell-inducing mRNA vaccine by reduction of type I interferon response

Abstract

CD8+ tissue-resident memory T cells provide rapid frontline protection at pathogen invasion sites, making them attractive targets for vaccine-mediated immunity. We previously developed an NKT cell-adjuvanted mRNA lipoplex vaccine capable of inducing liver Trm cells and sterile protection against malaria in mice. Here, we show that type I interferon (IFN-I) signalling through dendritic cells -- not T cells -- is a key brake on liver Trm induction by this vaccine. Optimising mRNA manufacturing to reduce immunostimulatory contaminants substantially dampened IFN-I production, boosted antigen expression in the lymphoid tissues, and drove significantly greater Trm accumulation. These enhanced responses translated into superior protection against parasite challenge. Our findings identify DC-intrinsic IFN-I signalling as a tractable target, and mRNA manufacturing quality as a critical and underappreciated lever, for maximising Trm-based vaccine efficacy.