(146c) Immune Modulating Lipid Nanoparticle Targets Antigen Presenting Cells and Enhances Vaccine Efficacy

Cancer is responsible for approximately ten million deaths each year and is one of the greatest challenges to global health. Immunotherapeutic cancer vaccines have shown promising preclinical results for several decades but have struggled to show effectiveness in clinical trials. Recent advancements in lipid nanoparticle (LNP) formulation have stimulated interests to develop mRNA-LNP vaccines for multiple diseases, including cancer. Despite their therapeutic potential, low vaccine immunogenicity and the immunosuppressive tumor microenvironment must be overcome for cancer vaccines to be clinically effective against solid tumors. One effective approach to increase immunogenicity is to increase mRNA delivery to antigen presenting cells. This study utilizes an immune modulating, naturally-derived ligand that binds a transmembrane receptor on immune cells. We hypothesized that post-modifying a LNP with the ligand would increase LNP targeting to antigen presenting cells through active targeting of the receptor. Additionally, the targeted LNP would result in a more effective vaccine leading to stronger T-cell responses.

For LNP modification, a thiol was introduced onto the ligand through an end-group modification. LNPs were then formulated with a maleimide functionalized PEG lipid conjugate for click chemistry with the thiolated polysaccharide. Several different LNP formulations were produced with varied amounts of lipid-PEG-maleimide in order to alter the final density of the ligand on the outside of the LNP. All LNP formulations were confirmed to bind to and engage with the desired receptor by using an engineered reporter cell line. A luciferase assay system confirmed that all LNP formulations had endosomal escape within 80% of the unmodified LNP. Next, LNPs were delivered in vivo using a Cre-Lox mouse model, where cells express tdTomato if successful delivery and translation of cre recombinase mRNA occurs. Using In Vivo Imaging Systems (IVIS) revealed enhanced fluorescence in the spleen, indicating increased uptake of LNP, in mice receiving ligand modified LNPs. Splenocyte isolation of these mice and flow cytometric staining of immune cells, revealed increased uptake of LNPs in antigen presenting cells. Additionally, splenocytes of mice vaccinated with ligand modified LNPs were isolated for an ELISPOT assay which showed increased T-cell responses over control LNPs. Lastly, vaccinating mice in a solid tumor model with ligand modified LNPs showed a greater reduction in tumor growth rate, then mice vaccinated with unmodified LNPs.

Our data has revealed that an immune modulating ligand can be used to target LNPs to the spleen, and specifically the antigen presenting cells in the spleen. Current work is focused on better understanding how the ligand’s immune modulating properties effect the immune response and its translation to other tumor and disease models.