Abstract 104: AAV-Exosomes: A Novel Platform for Myocardial Gene Delivery for Cardioprotection

Abstract

Introduction: Adeno-associated viruses (AAVs) are viral vectors of choice for delivering genes for long-term expression due to their safety in clinics. However, pre-existing immunity to AAVs from naturally present neutralizing antibodies (NAbs, present in between 60% and 90% of population) poses a significant challenge for AAV-mediated gene delivery. NAbs prevent AAVs from infecting target cells, greatly reducing transduction efficiency and, therefore, the clinical efficacy. Thus, it is essential to develop novel AAV-based vectors that circumvent the effect of NAbs. Objectives: We aimed to investigate the ability of exosome-encapsulated AAVs (AAVExo) to evade NAbs and serve as a highly efficient gene transfer tool for cardiovascular therapeutics. Methods and Results: We developed a multi-step purification strategy using iodixanol density gradient to isolate AAVExo with minimal contamination from free AAVs (AAV1, 6 or 9). Biochemical assays, flow cytometry, IVIS Spectrum in vivo optical imaging and echocardiography were used to detect AAV-mediated gene delivery and evaluate cardiac function. AAV6Exo-mCherry and AAV9Exo-FLuc were resistant to NAbs and significantly improved expression of mCherry and firefly luciferase (FLuc) both in mouse and human (iPSC-derived) cardiomyocytes in vitro , and in murine hearts in vivo (in nude mice preinjected with NAbs), compared to free AAVs. To test the therapeutic efficacy of AAVExo-mediated gene delivery in the presence of NAbs, we injected AAV9-SERCA2a or AAV9Exo-SERCA2a into post-MI hearts of nude mice preinjected with IVIg (human intravenous immunoglobulin) preparation. Hearts treated with AAV9Exo-SERCA2a had significantly improved cardiac function compared to those treated with free AAV9-SERCA2a (%EF 62.6 ± 9.8 vs. 28.4 ± 5.3, respectively; 2 weeks after surgery). Conclusion: Delivery of AAVs protected by carrier exosomes is a promising approach to circumvent the issue of NAbs in AAV-based gene therapy, which can be used in the entire population of patients and may result in higher gene delivery efficacy.