Gene Therapy and RPE Transplantation in the RPE65 -/- Mutant Mouse

Abstract

Abstract: : Purpose:Three strategies have been used to treat the RPE65 -/- mouse and the Briard dog, both models of a form of Leber's Congenital Amaurosis(LCA). Oral gavage of 9-cis retinal, RPE transplantation, and gene therapy have all been reported to rescue function in this model of LCA. To date no therapy has been shown to produce permanent rescue. To determine which strategy is most effective, we are comparing RPE transplantation with somatic gene therapy in the same mouse model. Methods:Methods for RPE transplantation have been published (IOVS 43:3307, 2002) as have our lentiviral vector constructs (Vision Res 42:551, 2002). The lentiviral vector uses a CMV promoter with the wild type murine RPE65 gene. A concentrated viral suspension, approximately 1-2 microliters, is injected into the subretinal space of one eye of mutant mice at 3-7 months of age. The site is assessed by biomicroscopy through the cornea. Corneal electroretinograms (ERGs) are obtained repeatedly from both eyes of each mouse in each litter before and after surgery. One eye receives treatment, the other does not. Retinas are examined histologically. Results:Both methods produce an increase in ERG amplitude within 1-2 weeks after surgery with a similar magnitude and consistency and independent of the age of the mice. For RPE transplants the ERG amplitude increases about two fold. This maximum effect diminishes over several months. For gene therapy the maximum increase detected so far is similar, but the results at present are limited. Neither technique influences the contralateral control eye. Conclusions:Both gene therapy and RPE transplantation can rescue functionin the Rpe65 -/- mutant. So far the therapeutic effects have had a similar time course, magnitude and consistency.

Keywords: retinal degenerations: cell biology • electroretinography: non-clinical • gene transfer/gene therapy