Abstract
Purpose :
To assess the applicability of the Orbit™ Subretinal Delivery System [OSDS™, 2nd Generation, 510(k) cleared] and OSDS™ prototypes of differing needle curvatures for subretinal injection (SRI) in dogs of different ages.
Methods :
WT dogs (n=8, age: 10-72 weeks) were used to test different OSDS™ devices for SRI of an AAV2/5-CBA-tdTomato-WPRE vector (vol: 0.1-0.18 mL, titers: 1.5-10E11 vg/mL). Perioperative surgical notes and video recordings were analyzed. Non-invasive fundus photography and cSLO/OCT retinal imaging including OCTA were performed in most dogs at 5 and 9 wks post-injection (PI). Following termination, eyes were processed for histology/IHC to examine the occurrence of surgically-induced lesions, inflammation, and reflux of the viral vector into the suprachoroidal space. All dogs were maintained during the in vivo period on a 5-week tapering course of systemic and topical steroids.
Results :
Successful SRI was achieved in 13 out of 14 eyes, yet this required in 8 eyes multiple needle advancements and/or changing devices to select the design best suited for young dogs. Subretinal hemorrhage was seen immediately after the SRI in 7 eyes that was resorbed by 3 wks PI in 6 eyes. The retinal blebs were fully reattached at 1 wk PI. TdTomato fluorescence was detected in vivo in all injected eyes at 5 wks but decreased at 9 wks PI in 3 eyes with clinical inflammation. Localized TdTomato expression was found in the suprachoroidal space (SCS) of 12 eyes along the path through which the cannula had been inserted. Labeling was strongest in the sclera (and to a lesser extent in the choroid) adjacent to the injection site and became less intense further away. Clinical signs of inflammation that were confirmed by histology (H&E) and IHC (CD4, CD8, CD20, Iba1, and CD18 positive cells) in the retina and choroid were seen in 6 eyes treated with viral titers in the 1.5-10E11 vg/mL range.
Conclusions :
The OSDS™ is a reliable device to achieve controlled subretinal injections in dogs including young puppies despite the presence of a cellular tapetum that likely caused some resistance to needle extension. Evidence of reflux of AAV into the SCS along the path used to insert the cannula was seen. An immune reaction to the AAV capsid or transgene may have contributed to choroidal inflammation observed in some eyes.
This abstract was presented at the 2024 ARVO Annual Meeting, held in Seattle, WA, May 5-9, 2024.