Prolonged Functional Optical Sensitivity in Non-Human Primate Motor Nerves Following Cyclosporine-Based Immunosuppression and rAAV2-Retro Mediated Expression of ChR2

Abstract

Peripheral optogenetic stimulation of motor activity offers enticing advantages over traditional functional electrical stimulation for the purposes of reanimating paralyzed muscles. When facilitated by intramuscular injection of viral gene therapy constructs, however, the process of transducing light sensitive ion channels along motor nerves faces several challenges including uptake of the virus at the neuromuscular junction as well as evasion of both virus and expressed gene products from the immune system. These hurdles to successful peripheral motor gene therapy are often amplified when attempting to translate these techniques to non-human primates. In this study, we examined the efficacy of a systemic immunosuppression regimen and use of a designer adeno-associated virus in prolonging functional opsin expression in targeted peripheral nerves of a macaque. Using a regimen of daily cyclosporine and either an intramuscular or intraneural injection of an rAAV2-retro based vector, we observed functional nerve expression of ChR2 via EMG activity locked to optical stimulation of a targeted nerve for up to 24 weeks post-injection. Throughout this experiment, we observed a gross timeline of expression including an initial increase of ChR2 expression over 9-13 weeks followed by an eventual decline after cessation of the immunosuppression regimen. These results suggest a potential strategy for successful translation of peripheral motor gene therapy to human subjects.