RPE65 Lentivirus-Mediated Gene Therapy in Rpe65R91W Mouse Model Restores Retinal Function

Abstract

Purpose:: Among the genes involved in Leber's Congenital Amaurosis (LCA), mutations in Rpe65 account for 10-15% of the cases. The severity of the disease as well as the mutation type is heterogeneous. However the correlation genotype/phenotype is not clearly established yet and the phenotype of the Rpe65^-/- mouse model may thus not necessarily correspond to the phenotypes of human Rpe65 patients. Consequently, we wanted to evaluate the effect on retinal activity of our lentivirus-mediated gene therapy in the new knock-in mouse model expressing the mutated Rpe65_R91W gene (Samardzija et al. # ARVO 2007), a mutation found in LCA patients.

Methods:: An HIV-1-derived lentiviral vector expressing either the GFP or the Rpe65 cDNA under the control of a 0.8 kb fragment of the human Rpe65 promoter (R0.8) was produced by transient transfection of 293T cells. LV-R0.8-RPE65 or GFP was injected into P5 or 1 month old R91W mice. Animals were followed 1, 2 and 3 or 4 months post-injection by ERG and optomotor response recordings to assess for retinal function.

Results:: For some animals, the retinal activity induced by visual stimuli was improved after Rpe65-gene transfer for both treatments started at P5 or 1 month old. Better scores were also observed for optomor response after Rpe65 gene transfer compared to GFP transfer. Correlation between transgene expression and functional rescue has to be determined

Conclusions:: We were able to show that lentivirus-mediated Rpe65 gene transfer not only increases retinal activity of Rpe65_R91W mouse model but also allows to improve the behavior of these mice in a visually-induced reflex. These results demonstrate that the whole visual circuitry is functional. In addition, both treatments at P5 and 1 month old appear to improve retinal activity. Further experiments will allow to determine if the therapeutic window is longer in this mutant context than the one we described previously for the Rpe65^-/- mice (Bemelmans et al. 2006).

Keywords: gene transfer/gene therapy • retinal degenerations: hereditary • retinal pigment epithelium