Abstract 10631: Exosome-Encapsulated Adeno-Associated Viruses as a Novel Cardiotropic Vector for Gene Therapy in Heart Failure

Abstract

Adeno-associated viruses (AAVs) are the vectors of choice for long-term delivery of genes to the heart and due to their safety in clinics. Despite its many favorable features, a notable drawback is the presence of preexisting neutralizing antibodies (NAb), which bind to free AAVs and impair their clinical effect. Here, we describe delivery of AAVs encapsulated in extracellular vesicles (eAAV), as a superior cardiac gene delivery system that offers higher NAb resistance. Methods: Ultracentrifuge-isolated eAAVs were characterized using TEM, DLS, qNano, nanoflow cytometry, ExoView, qPCR and Western blot. Gene delivery efficacy of free AAV and eAAVs were compared with and without NAbs using human cardiomyocytes in vitro, and in mice in vivo, using flow cytometry (with mCherry) and bioluminescence imaging (with luciferase). Therapeutic efficacy of gene delivery by free AAV and eAAV in presence and absence of NAb was determined using a cardiac contractile gene SERCA2a in a mouse model of myocardial infarction (MI). eAAV uptake and trafficking was studied both in vitro and in vivo using fluorescence dye-labeled eAAV. Results: eAAV outperformed free AAV in delivering genes even in the presence of NAbs, both in vitro and in vivo. SERCA2a delivered by eAAV significantly improved cardiac function (ejection fraction, %EF, ~60%) compared to when delivered by free AAV (~40%) or saline control (~20%), in intramyocardially injected MI mice with NAb. Fluorescence-tagged eAAVs injected to mouse hearts were internalized into all cell types (CMs and non-CMs), but, eAAV-mCherry was primarily expressed in CMs, indicating that eAAV-mediated gene delivery is cardiotropic. eAAVs were uptaken in to acidic endosomal (Rab5 & 7 positive) compartments of cultured cardiomyocytes and delivered significantly higher amounts of luciferase to the nucleus of human CMs compared to free AAVs. This uptake of eAAVs was inhibited by the proton pump inhibitor in endosomes, Bafilomycin A1. Conclusion: Our study demonstrated that eAAV-mediated gene delivery can circumvent neutralizing antibody (NAb) issue for gene therapy. eAAVs are cardiotropic and deliver genes to the nucleus via uptake into acidic endosomes. eAAV is a superior gene delivery vector and a new platform to treat heart failure.