Sustained AAV-mediated Dystrophin Expression in a Canine Model of Duchenne Muscular Dystrophy with a Brief Course of Immunosuppression

Adeno-associated virus-based vector (AAV)-mediated gene delivery has been successful in some animal models of human disease such as the mdx mouse model of human Duchenne muscular dystrophy (DMD). However, recent evidence of immune-mediated loss of vector persistence in dogs and humans suggests that immune modulation might be necessary to achieve successful long-term transgene expression in these species. We have previously demonstrated that direct intramuscular injection of AAV2 or AAV6 in wild-type random-bred dogs resulted in a robust immune response to capsid or capsid-associated proteins. We now demonstrate that a brief course of immunosuppression with a combination of anti-thymocyte globulin (ATG), cyclosporine (CSP), and mycophenolate mofetil (MMF) is sufficient to permit long-term and robust expression of a canine micro-dystrophin (c-micro-dys) transgene in the skeletal muscle of a dog model for DMD (canine X-linked muscular dystrophy, or cxmd dog) and that its expression restored localization of components of the dystrophin-associated protein complex at the muscle membrane. This protocol has potential applications to human clinical trials to enhance AAV-mediated therapies.