In Vivo Potency Testing of Subretinal rAAV5.hCNGB1 Gene Therapy in the Cngb1 Knockout Mouse Model of Retinitis Pigmentosa

Retinitis pigmentosa type 45 (RP45) is an autosomal-recessively inherited blinding disease caused by mutations in the cyclic nucleotide-gated channel subunit beta 1 ( ) gene. In this study, we developed and tested a novel gene supplementation therapy suitable for clinical translation. To this end, we designed a recombinant adeno-associated virus (rAAV) vector carrying a genome that features a novel human rhodopsin promoter (hRHO194) driving rod-specific expression of full-length human (rAAV5.hCNGB1). rAAV5.hCNGB1 was evaluated for efficacy in the knockout ( ) mouse model of RP45. In particular, increasing doses of rAAV5.hCNGB1 were delivered through single subretinal injection in 4-week-old mice and the treatment effect was assessed over a follow-up period of 9 months at the level of (1) retinal morphology, (2) retinal function, (3) vision-guided behavior, and (4) transgene expression. We found that subretinal treatment with rAAV5.hCNGB1 resulted in efficient expression of the human CNGB1 protein in mouse rods and was able to normalize the expression of the endogenous mouse CNGA1 subunit, which together with CNGB1 forms the native heterotetrameric cyclic guanosine monophosphate-gated cation channel in rod photoreceptors. The treatment led to a dose-dependent recovery of rod photoreceptor-driven function and preservation of retinal morphology in mice. In summary, these results demonstrate the efficacy of gene supplementation therapy in the mouse model of RP45 and support the translation of this approach toward future clinical application.