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Catherine O'Riordan, Matthew Adamowicz, Frederick Amy, Shelley Nass, Maryellen Mattingly, Denise Woodcock, Michael Lukason, Jennifer Sullivan; Translational fidelity of photoreceptor specific AAV capsids and promoter elements. Invest. Ophthalmol. Vis. Sci. 2019;60(9):2974.
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© ARVO (1962-2015); The Authors (2016-present)
The efficacy of AAV gene therapy for inherited retinal degenerative diseases has now been established in both preclinical studies and clinical trials. To guide the selection of an optimal AAV serotype for the treatment of rod photoreceptor mediated retinal dystrophies, such as Retinitis Pigmentosa, the efficacy of AAV5 and a novel variant AAV2HBKO were compared in the context of the mouse and NHP retina.
The AAV2HBKO variant, was generated by targeted mutation of arginine 585 and 588 in the parental AAV2 capsid, both arginines are implicated in heparin sulphate binding and when changed to alanine generate a variant, AAV2HBKO, which is devoid of heparin sulphate binding (Sullivan et al., 2018). AAV5 and AAV2HBKO vectors expressing EGFP under control of either a ubiquitous promoter or a rod cell specific promoter. were generated for further evaluation.
AAV5 and AAV2HBKO, in conjunction with the ubiquitous promoter, were found to be effective, and comparable at transducing both rod and cone photoreceptors as well as retinal pigmented epithelial cells, following subretinal injection into nondegenerate mouse eyes. In contrast, use of a a rod cell specific promoter, resulted in restriction of EGFP expression to rod photoreceptors, following subretinal delivery of either serotype to the mouse retina. AAV5 and AAV2HBKO, in the context of the rod cell specific promoter and EGFP transgene, were additionally tested in the cynomolgus monkey (Macaca fascicularis) retina, to determine if there were species specific tropism or promoter performance differences. . For both vector groups, the intensity of EGFP expression was comparable, and expression was observed in the outer nuclear layer, specifically in the rod photoreceptors, as determined by co-localization of rhodopsin protein staining.. Additionally, there was a slight difference in the pattern of transduction between the two vectors, with the AAV5 vector showing transduction patterns consistent to the edge of the bleb, in contrast the AAV2HBKO vector which showed transduction patterns that extended beyond the edge of the bleb.
In conclusion the performance of both AAV5 and AAV2HBKO in the context of the rod specific, human rhodopsin promoter is comparable for both the mouse and NHP retinae, and the results presented here should help inform AAV serotype and promoter selection for basic and translational retinal research.
This abstract was presented at the 2019 ARVO Annual Meeting, held in Vancouver, Canada, April 28 - May 2, 2019.
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