Repeat intravitreal delivery of rAAV2 increases retinal ganglion cell transduction in non-human primate

Abstract

Purpose : Ocular inflammation or formulation constraints may limit intravitreal (IVT) doses of rAAV2 for gene therapies, so maximal transduction and effectiveness may not be achieved with a single treatment. To address these limitations, the potential for repeat rAAV2 IVT delivery to increase retinal ganglion cell (RGC) transduction was evaluated in non-human primate (NHP).

Methods : NHPs (n=8) were injected IVT (OU) with rAAV2.eGFP (1.12 x 10¹¹ vg) on Day 0. On Day 7, a second IVT injection (OU) delivering rAAV2.tagRFP (1.29 x 10¹¹ vg) was administered to 4 of the 8 animals. Ocular tolerability assessments and fundus imaging of eGFP expression were performed 3, 5, and 8 weeks after treatment. Ocular tissues were collected at 8 weeks and retinal whole mounts prepared after immunolabeling RGCs. eGFP and tagRFP expression in RGCs was quantitated by analysis of confocal images of the whole retina with emphasis on the foveal region. Transduction efficiency of repeat rAAV2 treatment was determined by quantitating eGFP and tagRFP colocalization with RGCs in the foveal region and whole retina.

Results : Repeat IVT rAAV2 injection was well tolerated with no serious adverse events or posterior segment inflammation. The transduction pattern was characterized by strong expression in the fovea/parafovea region, punctate expression in the peripheral retina, and localized perivascular expression. Low transduction was observed in the foveal pit and no transduction was observed in the central retina outside of the parafovea. Repeat IVT rAAV2 injection transduced 21.1±8.6% of RGCs in the fovea/parafovea region compared to 22.8±7.1% of RGCs with the first rAAV2 injection. Of RGCs transduced with a repeat injection, 13.2±6.2% were previously transduced with the first injection and 7.8±3.1% were newly transduced RGCs resulting in 30.6±9.6% total RGC transduction (p<0.0005). Whole retina analysis showed that a repeat rAAV2 injection transduced 3.1±1.1% of RGC area compared to 5.4±1.9% of RGC area with the first injection. Of the RGC area transduced with a repeat injection, 1.5±0.5% was previously transduced with the first injection and 1.6±0.7% was new transduction resulting in 7.0±2.2% total RGC transduction (p<0.0005).

Conclusions : Additional transduction of RGCs can be attained by repeat IVT delivery of rAAV2 and may provide visual benefit for patients undergoing gene therapy.

This is a 2020 ARVO Annual Meeting abstract.