Abstract B004: Route dependent T-cell activation by mRNA cluster therapies

Abstract Purpose: Our group has developed a novel mRNA cluster vaccine (RNA lipid particle aggregates) in human clinical application (Mendez et al., Cell 2024, NCT04573140). This study aimed to refine delivery strategies and assess the capacity of off-the-shelf RNA-LPA formulations to induce antigen-specific T-cell responses in vivo. We sought to evaluate whether different routes of administration influence the immunogenicity of an mRNA vaccine encoding neoepitopes delivered via a lipid particle aggregate (LPA). Methods: CB57Bl/6 mice were implanted with Lewis lung carcinoma (LLC) i.v. or B16F10-OVA cells subcutaneously. We designed mRNA vaccines targeting p53 and KRAS mutations in LLC and determined the optimal route of administration in melanoma bearing animals. Blood was collected via retro-orbital on days 14 and 21, and peripheral blood mononuclear cells (PBMCs) were isolated for downstream flow cytometry. CD8+ T-cell populations were quantified via flow cytometry using a SIINFEKL-specific tetramer staining. Results: Mice receiving i.v. administration of RNA-LPA encoding for KRAS or p53 neoepitopes had trends towards improved survival outcome. When comparing i.v. to intramuscular treatment of RNA-LPAs, i.v. administration appeared superior. Following i.v. administration, animals exhibited a robust antigen-specific CD8+ T cell response, with 22-29% of PBMCs staining positive for the SIINFEKL-specific tetramer. In contrast, mice receiving i.m. administration (either full-length OVA or SIINFEKL fragment) or left untreated showed negligible tetramer-positive T-cells. Conclusion: Intravenous administration of RNA-LPA appears superior to intramuscular delivery for eliciting robust antigen-specific CD8+ T cell responses in vivo. Citation Format: Yodarlynis Campaneria, Christiano Marconi, Darrice Montgomery, Puttawat Suphaprueksapong, Nagheme Thomas, Andria Doty, Hector Mendez-Gomez, Elias Sayour. Route dependent T-cell activation by mRNA cluster therapies [abstract]. In: Proceedings of the AACR Special Conference in Cancer Research: Mechanisms of Cancer Immunity and Cancer-related Autoimmunity; 2025 Sep 24-27; Montreal, QC, Canada. Philadelphia (PA): AACR; Cancer Immunol Res 2025;13(9 Suppl):Abstract nr B004.