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Vectors based on adeno-associated virus serotype 2 (AAV2) have been used extensively in many gene-delivery applications, including several successful clinical trials for one type of Leber congenital amaurosis in the retina. Many studies have focused on improving AAV2 transduction efficiency and cellular specificity by genetically engineering its capsid. We have previously shown that vectors-containing single-point mutations of capsid surface tyrosines in serotypes AAV2, AAV8, and AAV9 displayed significantly increased transduction efficiency in the retina compared with their wild-type counterparts. In the present study, we evaluated the transduction characteristics of AAV2 vectors containing combinations of multiple tyrosine to phenylalanine mutations in seven highly conserved surface-exposed capsid tyrosine residues following subretinal or intravitreal delivery in adult mice. The multiply mutated vectors exhibited different in vivo transduction properties, with some having a unique ability of transgene expression in all retinal layers. Such novel vectors may be useful in developing valuable new therapeutic strategies for the treatment of many genetic diseases. [ABSTRACT FROM AUTHOR]

The RPE65 gene encodes the isomerase of the retinoid cycle, the enzymatic pathway that underlies mammalian vision. Mutations in RPE65 disrupt the retinoid cycle and cause a congenital human blindness known as Leber congenital amaurosis (LCA). We used adeno-associated virus-2-based RPE65 gene replacement therapy to treat three young adults with RPE65-LCA and measured their vision before and up to 90 days after the intervention. All three patients showed a statistically significant increase in visual sensitivity at 30 days after treatment localized to retinal areas that had received the vector. There were no changes in the effect between 30 and 90 days. Both coneand rod-photoreceptor-based vision could be demonstrated in treated areas. For cones, there were increases of up to 1.7 log units (i.e., 50 fold); and for rods, there were gains of up to 4.8 log units (i.e., 63,000 fold). To assess what fraction of full vision potential was restored by gene therapy, we related the degree of light sensitivity to the level of remaining photoreceptors within the treatment area. We found that the intervention could overcome nearly all of the loss of light sensitivity resulting from the biochemical blockade. However, this reconstituted retinoid cycle was not completely normal. Resensitization kinetics of the newly treated rods were remarkably slow and required 8 h or more for the attainment of full sensitivity, compared with <1 h in normal eyes. Cone-sensitivity recovery time was rapid. These results demonstrate dramatic, albeit imperfect, recovery of rodand cone-photoreceptor-based vision after RPE65 gene therapy. [ABSTRACT FROM AUTHOR]

Loss of cone function in the central retina is a pivotal event in the development of severe vision impairment for many prevalent blinding diseases. Complete achromatopsia is a genetic defect resulting in cone vision loss in 1 in 30,000 individuals. Using adeno-associated virus (AAV) gene therapy, we show that it is possible to target cones and rescue both the cone-mediated electroretinogram response and visual acuity in the Gnat2 cpfl3 mouse model of achromatopsia. [ABSTRACT FROM AUTHOR]