Recently, the use of mRNA-based vaccines for cancer immunotherapy has gained growing attention. Several studies have shown that mRNA delivered in a vectorized format can generate a robust and efficient immune response. In this work, a new lipopolyplex vector (multi-LP), incorporating the immune adjuvant α-galactosylceramide (α-GalCer) and a multivalent cationic lipid, was proposed for the in vivo delivery of mRNA into antigen-presenting cells. We demonstrate that dendritic cells (DCs) can be targeted in vivo by intravenous administration of a α-GalCer-/mRNA-loaded multi-LP vector, without the need for its functionalization with cell-specific antibodies or ligands. The multi-LP nanoparticles loaded with a reporter mRNA efficiently led to high expression of the enhanced green fluorescence protein in DCs both in vitro and in vivo, exhibiting an intrinsic selectivity for DCs. Finally, the TRP2-mRNA/α-GalCer-based multi-LP vaccine induced a significant therapeutic effect against a highly malignant B16-F10 melanoma tumor. This study provides the first evidence that a combination of antigen-mRNA and α-GalCer can be used as an effective antitumor vaccine, inducing strong innate and adaptive immune responses.

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