Abstract
Purpose:
Recombinant AAV, with a number of clinical trials in progress, is a favored vector for retinal gene delivery. An array of naturally occurring or engineered serotypes can be used to provide specific targeting to different cell types within the retina. However, recent studies indicate that transduction efficiencies vary significantly between species. Serotypes highly efficient in preclinical rodent studies may be less potent when evaluated in non-human primates or indeed in human patients. Therefore the isolation/creation and evaluation of new AAV serotypes is required to optimize this gene delivery technology and provide an array of serotypes, some of which may potentially be efficacious in humans. In the current study, we have investigated the applicability of AAV2/rh10 for the retina by comparing the efficacy of this serotype with AAV2/8 as a means to achieve rhodopsin replacement in a rhodopsin knock-out mouse model (Rho-/-).
Methods:
A rhodopsin replacement gene driven from a rhodopsin promoter was produced in AAV2/8 and AAV2/rh10 using the triple transfection method and subsequent CsCl purification. At p3-4, Rho-/- pups were given a single subretinal injection of 4 x 10e9 vg of either rhodopsin replacement AAVs (AAV2/8-RHO or AAV2/rh10-RHO) mixed with AAV2/5-EGFP to trace injections. Performance of the treated retinas was followed up to 11 months post-delivery.
Results:
Significant preservation of rhodopsin expression, the outer nuclear layer, photoreceptor segments and their ultrastructure was observed using both fluorescence and electron microscopy in the treated retinas. Electroretinography (ERG) and optokinetic tracking responses (OKR) were also significantly improved in treated mouse eyes when compared to the untreated controls suggesting that functional vision was improved. In this model system, efficacy of AAV2/8 and AAV2/rh10 for gene delivery to photoreceptors was similar in all aspects tested.
Conclusions:
The results suggest that AAV2/8 and AAV2/rh10 are highly and similarly efficient in the mouse retina. Additional studies are required to test applicability of AAV2/rh10 in non-human primates and potentially in the clinic.
Keywords: 538 gene transfer/gene therapy •
648 photoreceptors •
702 retinitis