Ab-Externo AAV-Mediated Gene Delivery to the Suprachoroidal Space Using a 250 Micron Flexible Microcatheter

Abstract

BackgroundThe current method of delivering gene replacement to the posterior segment of the eye involves a three-port pars plana vitrectomy followed by injection of the agent through a 37-gauge cannula, which is potentially wrought with retinal complications. In this paper we investigate the safety and efficacy of delivering adeno-associated viral (AAV) vector to the suprachoroidal space using an ab externo approach that utilizes an illuminated microcatheter.Methods6 New Zealand White rabbits and 2 Dutch Belted rabbits were used to evaluate the ab externo delivery method. sc-AAV5-smCBA-hGFP vector was delivered into the suprachoroidal space using an illuminated iTrackTM 250A microcatheter. Six weeks after surgery, the rabbits were sacrificed and their eyes evaluated for AAV transfection using immunofluorescent antibody staining of GFP.ResultsImmunostaining of sectioned and whole-mounted eyes demonstrated robust transfection in all treated eyes, with no fluorescence in untreated control eyes. Transfection occurred diffusely and involved both the choroid and the retina. No apparent adverse effects caused by either the viral vector or the procedure itself could be seen either clinically or histologically.ConclusionsThe ab externo method of delivery using a microcatheter was successful in safely and effectively delivering a gene therapy agent to the suprachoroidal space. This method presents a less invasive alternative to the current method of virally vectored gene delivery.

Retinal Gene Therapy: Surgical Vector Delivery in the Translation to Clinical Trials

“…In pre-clinical settings, ab externo SR injection has been successfully tested in mice (Fischer et al, 2013), rabbits (Peden et al, 2011; Martorana et al, 2012), and pigs (Smet et al, 2012). The procedure involves penetration of the conjunctiva, sclera, choroid, and RPE at the equatorial region in order to reach the subretinal space without disrupting the retina.…”

Animal models of age related macular degeneration

“…The suprachoroidal space is another potential space for the delivery of angiogenic substances and gene therapy vectors (Peden et al, 2011). Zahn et al used a scleral cut down and cyclodialysis spatula to access the suprachoroidal space in rabbits and implanted pellets impregnated with VEGF and FGF-2 or a control solution (Zahn et al, 2009a).…”

Modulation of Transgene Expression in Retinal Gene Therapy by Selective Laser Treatment

“…Subretinal AAV has been extensively studied in the retina and RPE, including in mice, [22][23][24] rats, 25,26 dogs, 27-30 nonhuman primates, 5,23 and humans [31][32][33][34] and more recently also in rabbit retina. 35 The vector titer in our study was determined based on previous publications, which used concentrations similar to those applied subretinally in most recent clinical trials. 31 Subretinal Injection of rAAV2.GFP Six eyes of six rabbits were used for subretinal injection of rAAV2.GFP.…”