80. Delayed Inflammatory Response to Intravitreal AAV Gene Transfer in Non-Human Primates

Introduction Adeno-associated virus (AAV) gene therapy in the eye via intravitreal injection has recently advanced into clinical trials. Here, we wanted to investigate the immunological response to AAV capsids within the vitreous of non-human primates. Methods Bilateral injections of AAV gene delivery were evaluated in five rhesus macaques. An intravitreal injection (IVT) was performed in one eye of the non-human primate, while a subretinal injection was performed in the contralateral eye. For the IVT eye, AAV2 or synthetic ancestral Anc80 capsid with GFP transgene was used at a concentration of 1E+11 particles. The surgical procedure for two animals was a normal IVT injection as performed in the clinic and the other two animals received an inner limiting membrane peel before viral injection. In the subretinal injection (SR) eye, animals were treated with AAV8 or 9, carrying the GFP or LacZ transgene at a concentration of 1E+10 or 1E+11 particles. Animals were monitored for 5/6 weeks before being sacrificed for histological analysis. Results In all eyes, inflammation in the first 2 weeks was mild or moderate and self-resolving. At weeks 3-5, all IVT treated eyes developed vitritis. None of the eyes injected subretinally developed vitritis. The most severe eye belonged to the IVT group, which developed hyphema and most of the IVT eyes developed anterior cataracts. Inflammation was well controlled with 4mg to 12mg of Triescence (triamcinolone acetonide) injected intravitrally. One animal was not given Triescence at the onset of inflammation (week 3), which became unmanageable within 48 hours, leading to the ultimate termination of the animal. Within the IVT group, similar amounts of late inflammation were seen between the intravitreal and peel/puddle eyes. Conclusion Our studies demonstrate that, in stark contrast to subretinal injection, an intravitreal injection of AAV expressing a non-self transgene has the potential to develop clinically significant inflammation at doses normally tolerated in the subretina. This inflammation can be treated with early administration of Triescence. Left untreated, the animal will develop severe immunological infiltration. These results warrant further study to determine the antigenic nature and inflammatory mechanism leading to the low inflammatory threshold to intravitreal AAV gene transfer.