390. Impact of a Treatment with Antioxidant on Gene Transfer Efficiency After Recombinant Adeno-Associated Vector Injection in a Mouse Model of Duchenne Muscular Dystrophy

Recombinant adeno-associated virus (rAAV)-based vectors are promising tools for the treatment of Duchenne muscular dystrophy (DMD) by gene therapy. Following rAAV injection in murine and canine models of DMD, several groups have reported significant phenotype improvements without notable toxicity, raising hope for future clinical translations. However, the long term maintenance of therapeutic benefits is an important, and yet unresolved issue. In previous studies conducted in DMD mice, we and others have demonstrated that rAAV-mediated transgene expression decreases progressively, even when clinically relevant vector doses are injected. Our team described several “restriction” factors having a negative impact on rAAV transduction, notably a loss of vector genomes resulting from muscle cell necrosis but also an oxidative damage affecting transgene mRNA. These first results support the fact that the tissue context in which rAAV vectors are delivered is of critical importance and can significantly affect their efficiency. In addition, they open new avenues for improvement since we can now consider counteracting these restriction phenotypes prior to rAAV injection. In the case of DMD, oxidative stress seems to occupy a central position in both muscle cell pathophysiology and rAAV transgene mRNA degradation. Therefore, we designed an innovative strategy using a relevant antioxidant agent routinely used in human medicine: N-acetylcysteine. DMD mice, pre-treated or not with this compound, were subsequently injected with a rAAV vector carrying a reporter transgene. The transduction efficiency, together with the expression and activity of the transgene, were carefully monitored and compared two months later. The outcome of this innovative approach will certainly pave the way for future combinatorial protocols using pharmacological agents and rAAV vectors in DMD muscles.