Nanoparticles versus Dendritic Cells as Vehicles to Deliver mRNA Encoding Multiple Epitopes for Immunotherapy.

The efficacy of antigen-specific immunotherapy relies heavily on efficient antigen delivery to antigen-presenting cells and engagement of as many disease-relevant T cells as possible in various lymphoid tissues, which are challenging to achieve. Here, we compared two approaches to deliver mRNA encoding multiple epitopes targeting both CD4+ and CD8+ T cells: a lipid-based nanoparticle platform to target endogenous antigen-presenting cells in vivo versus ex vivo mRNA-electroporated dendritic cells. After intraperitoneal injection, the nanoparticle platform facilitated efficient entry of mRNA into various endogenous antigen-presenting cells, including lymph node stromal cells, and elicited robust T cell responses within a wider network of lymphoid tissues compared with dendritic cells. Following intravenous injection, mRNA-electroporated dendritic cells and the nanoparticle platform localized primarily in lung and spleen, respectively. When administered locally via an intradermal route, both platforms resulted in mRNA expression at the injection site and in robust T cell responses in draining lymph nodes. This study indicates that multiple epitopes, customizable for specific patient populations and encoded by mRNA, can be targeted to different lymphoid tissues based on delivery vehicle and route, and constitute the groundwork for future studies using mRNA to reprogram exogenous or endogenous APCs for immunotherapy.