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Jacklyn H Salmon, Matthew Hirsch, Terete Borras, Brian C Gilger; Validation of Gene Delivery in Sheep Ocular Models Towards a Translation Strategy for Optimization of Human Eye Gene Therapy. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3338.
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Ocular gene addition therapies based on viral vectors have demonstrated clinical successes, however, these pioneering experiments remain non-optimized with persistent concerns regarding the required dose, the optimal route of administration, and the transduction efficiency/distribution to different eye compartments, in addition to systemic concerns. Therefore, ex vivo AAV vector optimization experiments in sheep eyes and subsequent data verification in sheep validates a translational strategy for the development of safer and more effective ocular delivery vectors for human therapy.
To characterize the sheep as a translational ocular model for AAV vector optimization, two ex vivo organ culture methods were investigated for the distribution of vector genomes and/or the efficiency of transduction. These systems included stationary cultures and whole organ ocular perfusion systems, both using fresh eyes collected from normal domestic sheep. AAV-eGFP and Ad-eGFP vector transduction was evaluated using anterior segment wedges with and without the iris, and processed for histological fluorescence and morphology assessment. In our second method, fresh sheep eyes were cultured using arterial perfusion / organ culture allowing the eyes to remain viable. Multiple AAV serotypes were individually administered via intravitreal or suprachoroidal injections and the tissues collected for analysis 24 hours later.
Stationary culture results demonstrated efficient transduction of the iris pigment epithelium and trabecular meshwork with significantly higher transduction by Ad5 compared to self-complementary AAV2, which was also confirmed in vivo following intravitreal injections. The data demonstrate that vector genomes administered by alternative routes localized to specific ocular compartments and preliminary results suggest that this distribution is dependent upon the AAV capsid serotype. ANY COMMENT ON RESULTS OF EX VIVO OCULAR PERFUSION?
Optimization of Ad and AAV vector transduction in sheep eyes cultured in different manners ex vivo and, subsequent validation in vivo, represents a translational strategy for the optimization of gene delivery technologies for the treatment of human ocular diseases.
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