Abstract
Purpose :
Suprachoroidal injection of adeno-associated virus (AAV) enables diffuse, peripheral transgene expression in eyes of nonhuman primates without invasive vitreoretinal surgery, but long-term expression may be limited without immunosuppression. Here, we investigate local ocular inflammatory and host immune responses to AAV8 delivered by suprachoroidal, subretinal, and intravitreal approaches.
Methods :
Rhesus macaques without pre-existing neutralizing antibodies (NAbs) against AAV8 were given 100mL AAV8 expressing enhanced GFP under a CMV promoter (up to 7 x 1012 vg/eye) delivered to both eyes by suprachoroidal or subretinal injections using 700mm transscleral microneedles or intravitreally using a standard 0.5” needle. We analysed GFP expression using scanning laser ophthalmoscopy and retinal anatomy by fundus photography and optical coherence tomography (OCT) in vivo, followed by histological analyses ex vivo. We evaluated host humoral responses to the GFP transgene using ELISA and NAbs against AAV8 using an in vitro transduction inhibition assay. We also measured cellular immune responses to GFP and AAV8 using ELISpot assays to detect IFN-γ-secreting T-cells from PBMCs.
Results :
Suprachoroidal AAV8 produced diffuse, circumferential GFP expression, while subretinal injections generated focal transgene expression. Both suprachoroidal and subretinal AAV8 triggered minimal anterior chamber inflammation, but demonstrated chorioretinitis and perivascular inflammation at 1 month that improved by 3 months. By contrast, intravitreal AAV8 produced only scant peripapillary GFP expression, and showed minimal anterior or posterior uveitis. Suprachoroidal AAV8 elicited more local infiltration of inflammatory cells than subretinal or intravitreal injections. Animals that received suprachoroidal or subretinal AAV8 showed greater anti-GFP antibody titers, while intravitreal AAV8 triggered more serum Nab response. None of the animals showed T-cell responses to AAV8 capsid, although one animal that received suprachoroidal AAV8 showed a T-cell response to GFP at 1 month.
Conclusions :
Without immunosuppression, suprachoroidal AAV8 elicits more chorioretinal inflammation than subretinal injections, but less systemic humoral response to AAV8 than intravitreal delivery. Our study provides insight into the immune consequences of AAV delivery to different compartments surrounding the outer blood-retinal barrier.
This is a 2020 ARVO Annual Meeting abstract.