(829) HARNESSING THE POTENTIAL OF mRNA VACCINES AGAINST HEPATITIS C VIRUS

Introduction/Rationale: Chronic hepatitis C virus (HCV) infection affects 58 million people globally and remains a major cause of cirrhosis and hepatocellular carcinoma. Aproximately 1 million new infections 250,000-related deaths occur annually, yet no vaccine exists. WHO has identified HCV as a top-priority virus requiring a vaccine to achieve viral hepatitis elimination. Increasing evidence implicates liver-resident memory CD8⁺ T (TRM) cells as key mediators of protection against hepatotropic pathogens. We therefore investigated whether mRNA vaccines can be engineered to establish robust intrahepatic TRM responses against HCV.

Methods: Nucleoside-modified mRNA encoding HCV genotype 3a NS5B polymerase was formulated in ALC-0315 or MC3 lipid nanoparticles (LNPs) or in DOTAP/DOPE liposomes to form lipid-complexed RNA (LPX). To enhance immunogenicity, LPX was co-formulated with the invariant NKT agonist α-galactosyl-ceramide analogue (α-GCB). BALB/c mice (n=5/group) received 5 µg mRNA per dose: via intramuscular, intradermal or intravenous routes. HCV-specific CD8⁺ T cells were quantified using flow cytometry, IFN-γ ELISPOT and intracellular cytokine staining in liver and the spleen.

Results: All formulations induced systemic and intrahepatic NS5B-specific CD8⁺ T cells, but only LPX-mRNA induced bona fide liver TRM cells. Co-delivery with α-GCB significantly increased TRM magnitude and numbers while homologous boosting further expanded durable intrahepatic TRM cells persisting to day 60 post-vaccination.

Conclusion: This study provides the first evidence that a HCV vaccine can elicit liver-resident memory CD8⁺ T cells. LPX’s hepatic tropism, combined with α-GCB driven NKT activation, efficiently imprints robust, durable liver TRM responses, supporting LPX-mRNA/α-GCB as a promising, platform for next-generation HCV vaccines