Circumventing cellular immunity by miR142-mediated regulation sufficiently supports rAAV-delivered OVA expression without activating humoral immunity

Recombinant adeno-associated virus-mediated (rAAV-mediated) gene delivery can efficiently target muscle tissues to serve as biofactories for secreted proteins in prophylactic and therapeutic scenarios. Nevertheless, efficient rAAV-mediated gene delivery is often limited by host immune responses against the transgene product. The development of strategies to prevent antitransgene immunity is therefore crucial. The use of endogenous microRNA-mediated (miRNA-mediated) regulation to detarget transgene expression from antigen-presenting cells (APCs) has shown promise for reducing immunogenicity. However, the mechanisms underlying miRNA- mediated modulation of antitransgene immunity by APC detargeting are not fully understood. Using the highly immunogenic ovalbumin (OVA) protein as a proxy for foreign antigens, we show that rAAV vectors containing miR142-binding sites efficiently repress costimulatory signals in DCs, significantly blunt the cytotoxic T cell response, allow for sustained transgene expression in skeletal myoblasts, and attenuate clearance of transduced muscle cells in mice. Furthermore, the blunting of humoral immunity against circulating OVA correlates with detargeting of OVA expression from APCs. This demonstrates that incorporating APC-specific miRNA-binding sites into rAAV vectors provides an effective strategy for reducing transgene-specific immune response. This approach holds promise for clinical applications where the safe and efficient delivery of a prophylactic or therapeutic protein is desired.