Regulation of Retinal Function but Non Rescue of Vision in Rpe65-Deficient Dogs Treated With Doxycycline-Regulatable Aav Vectors

Abstract

Purpose: : Adeno-Associated viral (AAV) gene therapy has raised hope for the treatment of patients with Leber congenital Amaurosis, caused by mutations in the retinal pigment epithelium (RPE)-specific gene RPE65. The preliminary results of three clinical trials suggest some improvement in visual function. However, further improvements might be necessary to optimize vision recovery and this means developing vectors able to generate transgene expression at physiological levels. The purpose of this study was to investigate the ability of the doxycycline-regulatable system to regulate retinal function in RPE65-/- Briard dogs.

Methods: : Recombinant AAV vectors expressing RPE65 under the control of either the TetOff and TetOn doxycycline-regulated promoters and the CMV constitutive promoter were generated and administered subretinally to seven RPE65-deficient dogs.

Results: : We demonstrated that a single subretinal injection into RPE65-deficient dogs of an AAV2/4TetOff.rpe65 or AAV2/4TetOn.rpe65 vector containing the RPE65 transgene under a doxycycline-dependent expression system results in an effective regulation of retinal function for at least 19 months. All treated dogs displayed tightly regulated retinal rod and cone function with similar induction and de-induction kinetics.

Conclusions: : We demonstrate that the induction and de-induction of retinal function, as assessed by electroretinography, can be achieved using a doxycycline-regulatable system, but do not lead to any recovery of vision.

Keywords: gene transfer/gene therapy • retina • vitamin A deficiency