Nanoparticles targeting liver sinusoidal endothelial cells improve tolerance to vector and transgene antigens through tolerance spreading

Liver sinusoidal endothelial cells (LSECs) naturally cross-present antigens and induce T cell tolerance. Targeting LSECs with peptide-coupled nanoparticles offers an efficient strategy to induce antigen-specific immune tolerance. Previous preclinical and clinical studies have shown that peptide-coupled nanoparticles can effectively inhibit T cell responses to the selected cognate peptide epitopes. However, clinical situations such as viral-vector-mediated gene therapy would benefit from simultaneous tolerance induction to multiple epitopes/antigens, posing a significant challenge. In this study, we used mouse models of adeno-associated virus (AAV)-mediated gene transfer to assess the in vivo effects of peptide-loaded nanoparticles designed to tolerize immune responses to transgene- or/and capsid-derived epitopes. We report here for the first time that LSEC-targeting nanoparticles coupled to a single peptide epitope promoted extension of tolerance to multiple relevant epitopes/antigens and simultaneously tolerized both CD4 + and CD8 + T cell responses. This tolerance spreading, which we termed "Tspread," remained specific to the transgene- and capsid-derived antigens conveyed by the administered AAV vector and did not impair immune responses to an unrelated vaccine antigen. These findings delineate a novel LSEC-mediated tolerance spreading with important clinical implications for viral-vector gene therapy, where tolerance to multiple epitopes/antigens is essential for long-term expression of therapeutic genes.