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Gina Martorana, Monica Levine, Marc Peden, Shannon Boye, Zachary Lukowski, Jeffrey Min, Craig Meyers, Sanford Boye, Mark Sherwood; Comparison of Suprachoroidal delivery via an Ab-Externo approach with the iTrack Microcatheter versus Vitrectomy and subretinal delivery for 3 different AAV Serotypes for Gene Transfer to the Retina. Invest. Ophthalmol. Vis. Sci. 2012;53(14):1931.
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Due to the invasive nature of subretinal injection and its potential to cause retinal damage, especially when performed under fragile, degenerate retina, there is impetus to develop less invasive delivery methods by which viral vector can gain access to the posterior retina. In this study, we compared the efficacy ofadeno-associated viral (AAV) the delivery to the suprachoroidal space using the posterior iTrack illuminated microcatheter (iScience, CA) versus standard three-port pars plana vitrectomy/subretinal injection. We made additional comparisons between the ability of three different AAV serotypes to transfect tissues, and evaluated whether transduction was affected by vector concentration.
Eight age-matched New Zealand White rabbits were used to evaluate the two delivery methods. The iTrack illuminated microcatheter was used to deliver vector or balanced saline solution (BSS) to eleven of the eyes; the remaining five eyes received vitrectomy/subretinal injection. The eyes were randomly assigned to receive AAV2, AAV5, or AAV2(triple) vector containing 3 tyrosine-phenylalanine mutations on its capsid surface. BSS served as the negative control. Within each group, two vector doses were administered (either 1x1012 and 4x1012, or 1x1012 and 9x1012 particles/mL). Rabbits were sacrificed 4 weeks post injection, and the eyes enucleated, sectioned and stained with antibodies directed against GFP and PNA lectin (a cone marker).
AAV-mediated GFP expression was found in eyes that received both vitrectomy/subretinal and iTrack injections. Expression varied among individual treatment groups. Immunostaining of sectioned eyes revealed strong, intermediate, minimal or no GFP expression from AAV2(triple), AAV2, AAV5 or BSS-injected eyes, respectively. Transduction profiles were not affected significantly by vector concentration.
The ab-externo, suprachoroidal iTrack approach successfully mediates AAV transduction of the posterior retina, similar to that seen with pars plana vitrectomy/subretinal injection. AAV2(triple) and AAV2 viral serotypes showed much stronger retinal transfection than the AAV5.
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