Abstract
Purpose :
Stargardt disease is an inherited juvenile macular dystrophy caused by mutations in the ABCA4 gene. The Abca4−/−mouse model is critical to test the efficacy of gene therapy approaches for future human applications. Since the size of ABCA4 gene exceeds the packaging capacity of single recombinant AAV virion, it necessitates a split-gene, dual AAV vector approach. Therefore, it is essential to evaluate the effect of dual AAV vector delivered reconstituted ABCA4 expression in the context of Stargardt disease pathology.
Methods :
Retinal structure and function of control WT (n = 12) and Abca4−/− (n = 12) mice were evaluated at 1,2,3,6,9,12,16,20 and 24 months using fundus imaging (FFA, AF at 488nm and 798nm), PS-OCT, full-field Electroretinography (ffERG) and histopathology. A separate cohort of WT and Abca4−/− animals were challenged with blue light (wavelength 430nm; intensity of 50mW/cm2 for 15 minutes/day for 1 week). During light illumination, a glass slip was placed on the cornea of the exposed eye. Abca4−/− (6-months-old) mice were injected sub-retinally with the AAV9.ABCA4 dual vector mix, 5′ or 3’ vector alone or sham. Retinal structural and functional changes of all groups were assessed weekly followed by harvesting the eyes for histology 2 months after injection.
Results :
Abca4−/− mice demonstrated significant lipofuscin accumulation from age 3 months to 6 months as well as corresponding loss of retinal function on ffERG. Inner, outer retina and cone function were found to be significantly reduced compared to age-matched WT controls (n=12, p<0.05). Histological analysis demonstrated mild photoreceptor loss at age of 6 months in Abca4−/− mice. However, blue light exposure caused significantly more damage to the retinal structure and function in Abca4−/− mice (n=12, p<0.01). AAV dual vector administered Abca4−/−eyes demonstrated reduced lipofuscin deposits (~50-60%) and significantly recovered retinal function (n=12, p<0.01). ABCA4 protein was expressed in the eyes receiving the dual vectors observed by immunofluorescence staining, but not the single vectors alone.
Conclusions :
Our data illustrates the utility of our hybrid AAV9 capsid ABCA4 dual vectors for treatment of Stargardt disease by reversing the associated retinal pathology.
This abstract was presented at the 2023 ARVO Annual Meeting, held in New Orleans, LA, April 23-27, 2023.