Splenic dendritic cell-targeting mRNA transfection of H-type ionizable lipid-based LNPs for enhancing tumor immunotherapy

Messenger RNA (mRNA) vaccine was emerging as a promising treatment for tumor immunotherapy. Highly efficient antigen-presenting ability in tumor immunotherapy through splenic dendritic cell (DC)-targeting mRNA delivery system was very important, but it remained a great challenge. In this study, a library of gemini-like ionizable lipid (termed H-type ionizable lipid, HIL) was synthesized and used for constructing mRNA-encapsulated nanoparticles (mRNA/HNPs) for in vivo mRNA delivery. Structure-activity relationship (SAR) analysis indicated that the spleen-targeting transfection efficiencies of mRNA were strongly correlated with the apparent p<i>K</i> _a values of mRNA/HNPs after intravenous injection. After formulation screening, the optimized mRNA/HNPs based on H18 lipid (mRNA/H₁₈NPs) with an average particle size of 124.4 ± 2.4 nm and a multilamellar concentric nanostructure were successfully prepared. Interestingly, without any ligand modification, the mOVA/H₁₈NPs exhibited splenic DC-targeting mRNA transfection, and markedly increased the amounts of IFN-γ⁺ CD8⁺ T cells and effector memory CD8⁺ T cells. Furthermore, in vivo results demonstrated that mRNA/H₁₈NPs encapsulating antigen-encoding mRNA including ovalbumin (OVA) or tyrosinase-related protein 2 (Trp2) effectively activated antigen-specific CD8⁺ T cells and resulted in significant antitumor efficacy in both B16-OVA or B16F10 tumor-bearing mouse models following intravenous administration. Especially, different from the mOVA/MC3-LNPs group, the mOVA/H₁₈NPs exhibited complete inhibition of tumor progression when it used as preventative cancer vaccines in B16-OVA tumor-bearing mouse model. These findings highlighted that mRNA/H₁₈NPs offer a promising splenic DC-targeting delivery system for mRNA vaccines.