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K.M. Binley, K. Balaggan; Development of a Hypoxia–regulated angiostatic lentivector gene therapy as a treatment for choroidal ocular neovascularisation . Invest. Ophthalmol. Vis. Sci. 2004;45(13):3142.
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Purpose: The aim of this study is to develop a long–term, regulated gene therapy strategy to achieve local, targeted, sustained delivery of an angiostatic molecule for the treatment of neovascular age–related macular degeneration (AMD). In this study we have evaluated the potential of using a hypoxia responsive promoter (OBHRE) to drive gene expression in the context of an equine infectious anaemia viral vector (EIAV). Methods: EIAV vectors carrying a CMV driven GFP reporter gene expression cassette were pseudotyped with either VSV–G or Rabies–G envelope proteins. Following subretinal administration the expression profile was evaluated at both early (1 week) and late (6 month) time points. Hypoxia activates a signalling cascade that leads to the stabilisation of the ubiquitous transcription factor, HIF–1 and the activation of genes that possess a hypoxia response element such as VEGF and erythropoietin. We have integrated a synthetic optimised hypoxia responsive promoter (OBHRE) that is highly activated under hypoxic conditions into the EIAV vector (EIAV.OBHRE) and evaluated the expression profile in human retinal pigment epithelial (RPE) cells. Results: Subretinal administration of EIAV.OBHRE. results in efficient transduction of the RPE. Expression is evident at 1 week post administration and persists for up to 6 months. EIAV.OBHRE mediates very high levels of expression under hypoxic conditions but has a low basal activity in normoxia in all cell types examined to date including human RPE cells. Conclusion: The combination of the persistence of expression from the EIAV vector in the RPE cells and the hypoxia controlled expression achieved with the OBHRE promoter is an attractive system for controlled delivery of angiostatic molecules for the long–term management of ocular neovascular disorders such as AMD.
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