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William A. Beltran, Simone Iwabe, Diego S. Fajardo, Sanford Boye, Wen-Tao Deng, William W. Hauswirth, Alfred S. Lewin, Gustavo D. Aguirre; rAAV-mediated Gene Delivery of Truncated Canine RPGR Causes Photoreceptor Dysplasia in Dogs with RPGR-ORF15 Stop Mutation. Invest. Ophthalmol. Vis. Sci. 2011;52(14):1418.
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To assess the efficiency and safety of RPGR replacement constructs delivered with a recombinant adeno-associated viral serotype 5 vector (rAAV2/5) in XLPRA1 dogs that carry a stop mutation in RPGR exon ORF15.
Three different promoters that included either segment of the proximal mouse opsin promoter (mOp), the human G-protein coupled receptor protein kinase 1 promoter (hGRK1), or the human interphotoreceptor retinoid binding protein promoter (hIRBP) were used to drive the expression of either the full-length human RPGR-ORF15 cDNA (hRPGR), or a shortened version of the canine RPGR cDNA (cRPGRshort). Four constructs (mOP-cRPGRshort, hIRBP-cRPGRshort, hGRK1-hRPGR, and hIRBP-hRPGR) were generated, packaged in rAAV2/5 vectors, and each was delivered via subretinal injection (150 ul at 1.51 x 1011 vg/ml) to the right eye of 2 mutant dogs at ~ 26-28 wks of age. Left eyes were sham-injected with BSS. Regular ocular examinations, and in vivo imaging (Spectralis HRA/OCT) were performed.
At 7 wks post-injection multifocal hyper-reflective lesions were observed by indirect ophthalmoscopy and cSLO/OCT imaging in the injected retinal area of the 2 dogs treated with hIRBP-cRPGRshort, and of 1 dog treated with mOP-cRPGRshort. These animals were euthanized, and histologic examination of the retinas showed severe multifocal retinal dysplastic lesions. A fourth dog treated with hGRK1-hRPGR had multifocal retinal detachments that were confirmed by histology. All 4 remaining animals did not show any adverse effects, and are still currently enrolled in the study.
Multifocal retinal dysplastic lesions were found following subretinal injection of an AAV2/5 vector to deliver a shortened canine RPGR-ORF15 cDNA in rods. Over-expression of the RPGR-ORF15 transgene may be responsible for this loss of normal retinal lamination in some treated animals.
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