Long-Term Preservation of Cones and Improvement in Visual Function Following Gene Therapy in a Mouse Model of Leber Congenital Amaurosis Caused by Guanylate Cyclase-1 Deficiency

Abstract

Leber congenital amaurosis (LCA) is a severe retinal dystrophy manifesting from early infancy as poor vision or blindness. Loss-of-function mutations in GUCY2D cause LCA1 and are one of the most common causes of LCA, accounting for 20% of all cases. Human GUCY2D and mouse Gucy2e genes encode guanylate cyclase-1 (GC1), which is responsible for restoring the dark state in photoreceptors after light exposure. The Gucy2e(-/-) mouse shows partially diminished rod function, but an absence of cone function before degeneration. Although the cones appear morphologically normal, they exhibit mislocalization of proteins involved in phototransduction. In this study we tested the efficacy of an rAAV2/8 vector containing the human rhodopsin kinase promoter and the human GUCY2D gene. Following subretinal delivery of the vector in Gucy2e(-/-) mice, GC1 protein was detected in the rod and cone outer segments, and in transduced areas of retina cone transducin was appropriately localized to cone outer segments. Moreover, we observed a dose-dependent restoration of rod and cone function and an improvement in visual behavior of the treated mice. Most importantly, cone preservation was observed in transduced areas up to 6 months post injection. To date, this is the most effective rescue of the Gucy2e(-/-) mouse model of LCA and we propose that a vector, similar to the one used in this study, could be suitable for use in a clinical trial of gene therapy for LCA1.

Absence of ocular malignant transformation after sub-retinal delivery of rAAV2/2 or integrating lentiviral vectors in p53-deficient mice

“…The clinical success of the RPE65 trials, combined with the increasing number of successful pre-clinical studies using rAAV [18][19][20][21] or lentiviruses, [22][23][24][25][26][27][28] suggest that more retinal gene therapy clinical trials are likely to start in the near future. It is, therefore, crucial to determine the oncogenic potential of these gene delivery vehicles in the context of the retina.…”

Gene supplementation therapy for recessive forms of inherited retinal dystrophies

“…However, there was no detectable improvement in rod-mediated ERG responses. In contrast, Mihelec et al 60 demonstrated a 65% rescue of cone ERG responses, cone vision and cone survival for up to 6 months, as well as a 35% rescue of rod function, after subretinal administration of an AAV2/8-based vector. Besides the difference in AAV serotype used, there are a number of variables that could account for the difference in efficacy, including the age at intervention, the promoter driving GUCY2D expression and the vector titre administered.…”

Massively parallel sequencing for early molecular diagnosis in Leber congenital amaurosis

“…For both AIPL1 and GUCY2D, proof-of-concept studies in animal models have shown beneficial effects of subretinal delivery of adeno-associated vectors containing the wild-type coding sequence. [42][43][44] The young age of these patients (10, 2, and 5 years) and the knowledge of their molecular defect identified them as potentially eligible for future gene therapy trials.…”