Gene Therapy in the Second Eye of RPE65 Deficient Dogs Rescues Retinal Function

Abstract

Purpose: : To evaluate whether prior subretinal gene therapy in the RPE65 -/- dog using an AAV2/2 construct containing human Rpe65 results in immune responses that interfere with rescue when the contralateral eye is similarly treated.

Methods: : Nine RPE65 -/- dogs underwent subretinal injection of an AAV2/2 vector containing the human Rpe65 gene coding region driven by the human Rpe65 promoter. Subretinal injection of the same vector construct was performed in the contralateral eye 90-180 days after the first injection. Rescue of retinal function was assessed by electroretinography and vision testing. Serum was collected to assess immune response to AAV2 and RPE65 (IgM and IgG levels by ELISA).

Results: : Rod and cone rescue was present in 16 of 18 injected eyes, and remained static up to 2 years post treatment. There was no significant difference in rod or cone response between the first or second injected eyes. Vision testing found significant improvement relative to pre-treatment values with no significant difference between the first or second treated eyes. A circulating immune response to the vector and RPE65 was detected but the level of response did not correlate with degree of rescue in the second eye.

Conclusions: : Successful rescue using AAV2 gene therapy in the second eye is possible in the RPE65 -/- dog. This has important implications for treatment of human Leber congenital amaurosis type II patients.

Keywords: gene transfer/gene therapy • retinal pigment epithelium • immune tolerance/privilege