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Katharine Liang, Kenton Woodard, Richard Samulski; AAV-mediated treatment of retinal degeneration in the Nrf2 knockout mouse. Invest. Ophthalmol. Vis. Sci. 2013;54(15):1361.
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© ARVO (1962-2015); The Authors (2016-present)
Reactive oxygen species (ROS) are involved in a wide variety of aging processes, including retinal degeneration, making it an excellent therapeutic target. Under conditions of chronic oxidative stress, normal redox homeostasis is deregulated, resulting in ROS accumulation and subsequent cellular damage. One therapeutic strategy is overexpression of the transcription factor Nrf2, which drives downstream antioxidant gene expression. We applied novel AAV vectors to regulate oxidative stress in the Nrf2-deficient mouse, which exhibits an age-related retinal degeneration. Our research provides a targeted molecular approach to drive antioxidant gene expression, and offers a promising alternative to currently limited therapeutics for multifactorial diseases involving ROS deregulation.
We have engineered AAV2.5-CBh-Nrf2 vector using a chimeric capsid vector and promoter selected for retinal transduction via intravitreal injection. Functional efficacy of AAV-Nrf2 was evaluated using in vitro luciferase reporter and fluorescent ROS detection assays. Downstream gene activation was assessed by western blot. AAV-Nrf2 was delivered to via intravitreal injection during early stage retinopathy. Therapeutic efficacy was assessed using electroretinogram (ERG, Ganzfield Dome) and optical coherence tomography (OCT, Bioptigen).
AAV2.5 combines the improved transduction properties of AAV1 with reduced antigenic cross-reactivity against antibodies directed at both parental serotypes while keeping the receptor binding properties of AAV2. Preliminary data supports the efficiency of AAV2.5 transgene delivery via intravitreal injection in the rodent retina. Preliminary ERG and OCT data suggests that AAV-Nrf2 is sufficient for rescue from age-related retinopathy seen in Nrf2-deficient mice. In vivo analysis is ongoing and update of Nrf2 expression is being monitored by both western and histological analysis.
AAV vector development combined with gene replacement offers a unique opportunity to optimize and test both efficient transgene delivery as well as potent therapeutic potential. Future studies to determine if a master regulator of a wide variety of antioxidant genes is promising or toxic to a therapeutic target will provide significant insight into future applications of this therapeutic approach.
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