Abstract 848: Preclinical development of the lipid nanoparticle-based mRNA vaccine with multiple natural T cell epitopes for pancreatic cancer

Abstract Background: Immunotherapy has recently emerged as a promising avenue in cancer treatment; however, its effectiveness on pancreatic ductal adenocarcinoma (PDAC) is hindered by the lack of effector T cells in the tumor microenvironment. One of the strategies to overcome the resistance of PDAC to immunotherapy involves identifying immunogenic tumor-associated and specific antigens for the development of personalized cancer vaccines. The mRNA platform has become an attractive platform for antigen presentation. The delivery of mRNA cancer vaccines via lipid nanoparticles (LNPs) enables intracellular delivery and controlled release of the payload, offering improved vaccine efficacy. However, mRNA vaccines presenting human T cell epitopes often lack a preclinical model for antitumor immune efficacy testing. Methods: A syngeneic mouse model of PDACs was established by implanting KPC tumor cells into the livers by hemispleen surgery. mRNA vaccines expressing five 25-mer peptide regions were synthesized. Two mouse CD8+ T cell epitopes were predicted. Their MHC binding was tested by the T2 binding assay. CD8+ T cells specific for these two epitopes were examined by ELISpot assays and were quantified by ImmunoSpot ELISpot Reader to identify changes in IFN- secretion. Results: Using mass spectrometry analysis, we successfully identified natural HLA class I and class II-binding epitopes in the neoplastic tissues of human PDACs. For the design of mRNA vaccine, we chose five 25-mer peptide regions that each contains both class I and class II epitopes punctuated by AAY and GPGPG linkers and followed by an MITD sequence, which all aim to improve the efficiency of antigen presentation to dendritic cells. Using NetMHC, we predicted H2Kb or H2Db-binding epitopes LYPFPLAL and SMVQMTFL, within these five human peptide regions. The T2 binding assay showed a lack of evident binding of both peptides to the T2-Kb or T2-Db cells. However, The ELISpot assay showed that LYPFPLAL, but not SMVQMTFL, can induce the IFN- expression from CD8+ T cells derived from splenocytes of the KPC tumor mice vaccinated by a peptide vaccine containing both peptides. Therefore, this result confirmed that LYPFPLAL is a mouse CD8+ T cell epitope and can be used to monitor antigen-specific CD8+ T cell response in response to the mRNA vaccine treatment in the syngeneic mouse model of PDACs. Conclusions: Antitumor efficacy of our above-designed mRNA vaccine can be tested in the syngeneic mouse hemispleen model of KPC tumors. Mouse LYPFPLAL epitope-specific CD8+ T cell response can serve as a surrogate marker for the antitumor efficacy of this mRNA vaccine in mouse models for PDAC. Citation Format: Josephine Chang, Kevin Zheng, Yiming Li, Wanting Shan, Lei Zheng, Hai-Quan Mao, Juan Fu, Jiawei Zhou. Preclinical development of the lipid nanoparticle-based mRNA vaccine with multiple natural T cell epitopes for pancreatic cancer [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 848