Abstract
Purpose :
Efficacy and safety of gene therapies for retinal diseases (RDs) have been proven with preclinical success translated into clinical effectiveness. However, this approach is rarely chosen for dominant forms. Based on our previous published work, we focused on dominant-negative mutations in the transcription factor CRX. We developed a mutation-independent AAV vector that could circumvent the clinical and genetic heterogeneity of CRX mutations. We also tested the neuroprotective potential of our gene therapy product for CRX-independent retinopathies.
Methods :
AAV-CRX is an AAV2/5 allowing the expression of human CRX specifically in photoreceptors, using Rhodopsin Kinase 1 promoter. The efficacy of AAV-CRX for different CRX-associated diseases was assess tested by injecting at P30 either CrxRip/+ mice, a model of Leber Congenital Amaurosis, or Tg(CRXR41W) mice, carrying the human CRXR41W mutation causing cone dystrophy. The effects on CRX-independent RD was also tested in rd10 mice by injecting at P14. The efficacy was assessed by immunohistochemistry, electroretinogram (ERG) and using a Dark/Light box test.
Results :
AAV-CRX injection led to specific expression of CRX in photoreceptors with no toxicity. Three months after subretinal injection in CrxRip/+ mice, we observed: i) a rescue of rod and cone opsin expression, ii) a rescue of outer segment formation, iii) some degree of ERG response whereas it remained flat in controls iv) a fully restored behavioral response to light stress. Tg(CRXR41W) characterization revealed a dose-dependent deleterious effect of CRXR41W expression. Indeed, heterozygous Tg(CRXR41W) carrying a single insertion displayed a functional retina while homozygous Tg(CRXR41W) exhibited reduced retinal function after 3 months. These results support the relevance of increasing the amount of CRXWT to counteract the dominant-negative effect of mutant CRX. The beneficial effects of AAV-CRX were observed in Tg(CRXR41W) mutant mice with a cone only retina (Nrl-/- background). Finally, we showed that AAV-CRX has also a beneficial effect on CRX-independent RD by preserving rod photoreceptors in rd10 mice.
Conclusions :
Overall, our gene therapy approach shows promising results for treating CRX-associated RDs, as well as CRX-independent retinopathies. It also highlights the potential interest of gene therapy to treat patients with RD carrying dominant-negative mutations.
This abstract was presented at the 2022 ARVO Annual Meeting, held in Denver, CO, May 1-4, 2022, and virtually.