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S. E. Boye, S.-H. Minh, S. L. Boye, B. Rohrer, P. Humphries, T. M. Redmond, M. Seeliger, W. W. Hauswirth; AAV-Mediated RPE65 Expression Confers Functional Rescue to Cone Photoreceptors in the RPE65-/-Rho-/- Mouse. Invest. Ophthalmol. Vis. Sci. 2007;48(13):4518.
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It has been shown that cone responses in the RPE65 deficient retina are masked by desensitized rod responses with altered kinetics. All animal models treated thus far with AAV-RPE65 (RPE65-deficient dog,Rpe65-/- mouse, and rd12 mouse) contain both rod and cone photoreceptor populations. While a restoration of both rod and cone function has been suggested in these animals, these studies did not provide direct evidence of pure cone rescue. This study utilizes the Rpe65-/- Rho-/- double knockout mouse in which rod phototransduction is eliminated. The purpose of this study was to test whether AAV-RPE65 treatment, when designed for RPE-only expression, confers pure cone rescue to an RPE65 deficient animal, providing further support for the recovery of cone function in human LCA2 patients.
Subretinal injections of pTR-VMD2-RPE65 (exclusive RPE-targeted expression of RPE65) were performed on P14 Rpe65-/- Rho-/- mice in one eye only. Electroretinographic and immunohistochemical analyses of treated and untreated eyes were carried out 4 weeks post-injection. An antibody raised against RPE65 was used to detect cells transduced by the AAV vector.
Dark adapted scotopic ERG recordings from both treated and untreated eyes indicated that rod function had been eliminated in this animal model. Light adapted photopic ERGs revealed that AAV-mediated RPE65 expression conferred functional rescue to cone photoreceptors. At highest stimulus intensities recorded, maximum b-wave amplitudes were as high as 40 µV whereas no signal could be detected in untreated eyes. IHC revealed RPE65 expression exclusively in the retinal pigment epithelium of treated, but not untreated eyes.
AAV- mediated RPE65 delivery to the RPE in Rpe65-/- Rho-/- mice confers functional rescue to cone photoreceptors. This is the first study to show that RPE targeted AAV gene therapy provides pure cone rescue in an RPE65 deficient animal model and supports the continued development of this vector for use in treatment of human LCA2.
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