Intravitreal Administration of an AAV8 Retinoschisin Vector to the RS1-KO Mouse Results in Cell Type-Specific Gene Expression and Rescue of the Disease Phenotype

Abstract

Purpose: : To evaluate AAV8-mediated retinal gene delivery and rescue following intravitreal injection in retinoschisin (Rs1)-knockout (RS1-KO) mouse.

Methods: : AAV8-CMV-EGFP and a novel delivery vector (AAV8-hRSp4), employing an AAV type 8 capsid with a 3.5 kb human retinoschisin promoter driving a truncated human RS1 gene were injected bilaterally or unilaterally to the vitreous cavity of 6-7 week and 7 month old wild type and Rs1-KO mice. Eight weeks later, AAV8-CMV-EGFP injected eyes were evaluated histologically. RS1 expression in Rs1-KO mouse retina was observed with immunolabeling 8 and 11 weeks after treatment. EGFP and RS1 expression in the optic nerve and ciliary body was evaluated at the same time points. Functional rescue of AAV8-hRSp4 treated groups was evaluated by the scotopic ERG. Age matched untreated Rs1-KO mice or untreated fellow eyes were used as control.

Results: : Intravitreal injection of AAV8-CMV-EGFP reporter construct resulted in the transduction of multiple layers of the Rs1-KO mouse retina including the retinal pigment epithelium, photoreceptors, inner nuclear layer cells, and ganglion cells. Intravitreal AAV8-hRSp4 administration to Rs1-KO mice resulted in robust retinoschisin expression with a retinal distribution similar to that observed in uninjected wild type retina. In two separate experiments, the ERG showed significant improvement in the b/a wave ratio 11 - 15 weeks after treatment (n = 8, p = 0.04, and n = 5, p = 0.012). No off-target expression was observed in the optic nerve and ciliary body.

Conclusions: : AAV8-hRSp4 delivered intravitreally produced efficient tissue and cell specific expression and rescued retinal function in Rs1-KO mouse. This demonstrates the potential of this construct and route of delivery for treating patients with X-linked juvenile retinoschisis.

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