Tomatine as a versatile adjuvant boosts mRNA vaccine responses

The potent adaptive immune response of mRNA vaccines requires that sufficient antigens translated from mRNA cargos and highly efficient activation of innate immunity. However, it remains unclear if simple introduction of an adjuvant can help mRNA vaccines achieve these functions. In this study, a nature product, tomatine, was experimentally incorporated into the widely used nanocarriers, serving a multi-functional adjuvant to improve mRNA expression efficiency and activate innate immunity. Tomatine based liposome (T-LPX) exhibited elevated uptake in dendritic cells (DCs) via caveolin-mediated endocytosis and improved mRNA translation via the increased expression of DExH-box helicase 29 mediated by tomatine, leading to a marked increase in mRNA expression efficiency and ensuring highly efficient antigen presentation. Additionally, tomatine was shown to activate nucleotide-binding oligomerization domain (NOD)-like receptor pathway, thereby promoting the secretion of IFN-<i>γ</i> and upregulating the co-stimulatory molecules (CD80 and CD86) in DCs. Finally, T-LPX loaded with a tumor antigen-encoding mRNA was investigated and found to elicit potent immune responses against the E.G7-OVA murine tumor. Furthermore, such versatile adjuvant effect of tomatine was also demonstrated to equally apply to the other nanocarrier (lipid nanoparticle) and antigen. The tomatine-based LNP-mRNA vaccine against SARS-CoV-2 presented enduring humoral and cellular immune responses. These findings underscore tomatine's potential as a versatile adjuvant for mRNA nano-vaccines, with promising applications in both cancer therapy and infectious disease prevention.