AAV dose-dependent transduction efficiency in retinal ganglion cells and functional efficacy of optogenetic vision restoration

Optogenetics is a promising approach for restoring vision to the blind after photoreceptor degeneration. The ability to restore vision through AAV-mediated delivery of light-sensitive proteins, especially channelrhodopsins, into retinal ganglion cells has been extensively demonstrated in animal models. For clinical application, knowledge of viral dose-dependent functional efficacy is desired. In this study, using a triple-knockout blind mouse model and a highly light-sensitive channelrhodopsin variant, we evaluated viral dose-dependent vision restoration through retinal ganglion cell expression by using optomotor behavioral assays. Our results show that both the restored light sensitivity and visual acuity reached peak levels at a medial viral dose of 10⁸ vg. With increasing dose, transduction efficiency continued to increase while protein expression peaked at the dose of ~10⁹ vg and declined at higher doses. Also, a significant increase in retinal gliosis and inflammatory responses started at the dose of ~10⁹ vg, and a marked increase was observed at the dose of ~10¹⁰. These results provide valuable insights into viral dose design for clinical studies.