Abstract
Purpose :
Gene transfer to the retina by adeno-associated viruses (AAV) has the potential to treat retinal diseases by the long term expression of a therapeutic polypeptide in situ. Sub-retinal administration of AAV has been shown to be safe and effective in delivering its gene cargo to RPE and photoreceptors in non-human primates (NHP) and in initial clinical trials. However, this method results in a locally restricted expression of the therapeutic gene, which may be insufficient in instances where more diffuse expression is desired. Also, it may in some instances induce potential mechanical damage that could be detrimental to a diseased, fragile retina. Intravitreal (IVT) administration is a less invasive, office-based approach that is likely capable of producing a wider area of retinal transduction given the appropriately chosen serotype and promoter. Naturally occurring AAV serotypes cannot efficiently cross the inner limiting membrane (ILM) and penetrate the retina in order to deliver its cargo. New serotypes are being developed to overcome this limitation.
Methods :
In this study, we delivered IVT to both NHP and rabbit eyes four AAV variants: AAV2.CMV-GFP, 7m8.CMV-GFP, ShH10.CMV-GFP, and 2.5T.CMV-GFP. We evaluated transgene expression and distribution within the retina. New Zealand White rabbits (n=4 eyes/group) were injected IVT with 5E8 vg/eye or 5E7 vg/eye in 50 μL. African Green Monkeys (n=6 eyes/group) were injected IVT with 5E11 vg/eye in 50 μL. GFP expression was evaluated by fluorescence fundus imaging weekly for rabbits and at weeks 4, 8, and 12 for NHP. Retinal structure and inflammation was evaluated by OCT at the same time points.
Results :
GFP expression was detected as soon as week 1 in rabbits and week 8 in NHP. In the rabbit retina, GFP expression was localized at the ray whereas in the NHP eye, strong GFP expression was detected in the fovea and peripheral retina. Different variants showed varying levels of GFP expression. In rabbits, 7m8 was able to transduce rabbit retinal cells at the lowest dose (5E7) whereas all the other three vectors required ten times more particles in order to achieve similar GFP levels. In NHP, 7m8 outperformed AAV2 and ShH10 while 2.5T showed no GFP expression.
Conclusions :
The AAV serotypes studied efficiently transduced retinal cells after a single IVT injection in both rabbits and non-human primates.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.