AAV9 gene therapy to target respiratory insufficiency in the D2.mdx mouse model of duchenne muscular dystrophy.

Duchenne muscular dystrophy (DMD) is an X-linked recessive disorder caused by a deficiency of dystrophin. Dystrophin deficiency leads to progressive muscle weakness, including involvement of the respiratory muscles, ultimately resulting in respiratory failure. Adeno-associated virus (AAV)-mediated gene therapy carrying a microdystrophin (µDys) transgene was recently approved by the Food and Drug Administration (FDA); however, its effects on the respiratory system remain unclear. Further, effective transduction of all muscle groups requires high systemic AAV doses, which are associated with dose-dependent toxicities. In this study, we investigated whether respiratory-directed gene therapy can 1) specifically target respiratory muscles and (2) reduce the total AAV-µDys dose required for therapeutic benefit. We compared the efficiency of AAV9-µDys delivery using different administration routes and dosages in D2.mdx mice, a mouse model of DMD. AAV9-µDys was administered either systemically at a high dose, locally at intermediate doses via intralingual and intrathoracic injections, or through a combination of systemic and respiratory-directed intermediate dosing. All treatments resulted in improved respiratory muscle dystrophin expression and decreased pathology; however, the intermediate and combination dosing led to lower liver vector genome expression. In conclusion, respiratory-targeted gene therapy can improve respiratory muscle pathology while reducing the need for high systemic AAV doses associated with liver toxicity.