AAV Variant-mediated Delivery of Retinoschisin Via Intravitreal Injection for Treatment of X-linked Retinoschisis

Abstract

Purpose: : X-linked retinoschisis (XLRS) is characterized by splitting of the layers of the retina and a loss of the ERG B-wave. Previous strategies for gene replacement therapy have shown promising results, although the most successful approaches have required a subretinal injection and the creation of a retinal detachment. A recently identified variant of AAV6, Shh10, is able to efficiently target Müller glia from the vitreous. Alternatively, a novel variant of AAV2, 7m8, is capable of delivering a transgene throughout the layers of the retina from an intravitreal injection, and expression can be restricted to photoreceptors using a cell-specific promoter. In this study we investigated the effects of gene-replacement therapy in Rs1h-deficient mice using these vectors, and tested the efficacy of expression from Muller glia, retina-wide or photoreceptor specific expression.

Methods: : AAV variants ShH10 or 7m8 were used to package RS1 cDNA. Virus was injected via an intravitreal injection in PN15 rs1h-/- mice. Electroretinograms were recorded on a monthly basis. Expression of RS1 was confirmed using immunohistochemistry and western blotting.

Results: : We demonstrate here that AAV variants 7m8 and Shh10 efficiently infect their target cell types via intravitreal injection in the mouse model of XLRS, the rs1h-/- mouse. Injection of 7m8 and ShH10 leads to production of RS1 that is delivered to its targets in the inner and outer retina. Expression of RS1 via intravitreal injection leads to rescue of the ERG B-wave.

Conclusions: : AAV variants ShH10 and 7m8 virus efficiently deliver RS1 cDNA to the retina, leading to high levels of expression of RS1 and rescue of the ERG. Intravitreal injections are a preferable method for gene delivery in this disease, which is characterized by structural abnormalities in the retina. We demonstrate here the efficiency of two AAV variants, developed using a directed evolution approach, for delivery of RS1 via intravitreal injections.

Keywords: gene transfer/gene therapy • retinal degenerations: hereditary • immunohistochemistry