A Novel AAV Capsid-Mediated RS1 Gene Therapy Restored Retinal Function to Wild-Type Levels in Rs1R213W Mouse Model.

Purpose: X-linked juvenile retinoschisis (XLRS) is a retinal disease caused by retinoschisin 1 (RS1) gene variants, potentially leading to severe visual impairment and blindness. This study aimed to develop a novel adeno-associated virus (AAV) serotype and evaluate its therapeutic potential in an XLRS mouse model. Methods: A novel RS1 mouse model was established using the CRISPR-Cas9 gene editing system and underwent phenotypic characterization. AAV.IVT18-scRS/CMV-RS1, comprising a rationally designed novel capsid (AAV.IVT18) and an optimized RS1 gene expression cassette, was then constructed and delivered via intravitreal injection into mutant and wild-type (WT) mice at 3 to 4 weeks of age. Retinal structure, function, and inflammation levels were evaluated after treatment. Results: A novel mouse model harboring the patient-derived RS1 missense variant R213W was generated, accurately recapitulating the human phenotype. We developed a novel AAV serotype, AAV.IVT18, which efficiently transfected photoreceptor and bipolar cells by intravitreal injection, and optimized the expression cassettes of RS1. AAV.IVT18-mediated expression of RS1 ameliorated retinoschisis in the mouse model and normalized the b/a ratio of the mouse electroretinogram (ERG). Remarkably, the ERG b-wave amplitudes of the treated groups began to increase at 8 weeks post-injection and recovered to the WT mouse level by 16 weeks of injection. Inflammatory activation in Rs1R213W mice was alleviated by treatment. Conclusions: The novel AAV capsid-mediated RS1 gene therapy effectively improved retinal structure and function while downregulating inflammation in Rs1R213W mice. These results provide a robust foundation for future clinical trials on XLRS gene therapy, offering the potential to improve the vision and quality of life of patients.