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M. M. Hamilton, D. E. Brough, C. King, L. L. Wei; Prolonged Gene Expression Using an Alternative Serotype Vector With RGD. Invest. Ophthalmol. Vis. Sci. 2009;50(13):1456.
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Adenoviral vectors are efficient gene delivery vehicles and are widely used in pre-clinical and clinical gene therapies. Abnormal blood vessel growth in the eye plays a factor in many common causes of blindness. Pigment Epithelium-Derived Factor (PEDF) is a potent antiangiogenic and neurotrophic factor that is normally produced in the eye. PEDF can block new blood vessel growth and trigger selective regression of abnormal blood vessels in animal models of ocular disease when delivered via an adenovector serotype 5 (Ad5). However, despite the efficacy and safety of Ad5-based therapy, gene expression is transient and there is a medical need for less frequent and non-invasive intraocular delivery. These data suggest that incorporation of an RGD peptide in the fiber of an Ad35 vector may result in a vector with expanded tropism that can provide greater benefit for treatment of chronic ocular diseases.
To assess transgene persistence, mice received a single, intravitreal (IVT) injection of Ad35 with or without the RGD motif expressing green fluorescent protein (GFP), luciferase or human PEDF. At specified timepoints, eyes were monitored either visually for GFP expression or harvested, and then assayed for luciferase activity or PEDF levels. In vivo biological activity was then investigated by evaluating prevention or regression of choroidal neovascularization (CNV) using mouse models with laser-induced rupture of Bruch’s membrane.
Preliminary studies demonstrate that following a single, IVT injection of an Ad35 vector containing RGD results in: 1) prolonged gene expression out to ~3 or 4 months in the eye; and 2) both prevention and regression of choroidal neovascularization in a mouse laser-induced CNV model.
These studies show that transgene levels are prolonged in the eye following a single, IVT injection of an Ad35 vector with RGD in the fiber. Interestingly, this was not observed using an Ad35 vector lacking RGD. Moreover, a single IVT injection of Ad35.PEDF with RGD results in both prevention and regression of abnormal blood vessel growth in experimental ocular models. These studies support further investigation into the mechanism and impact of the RGD motif on Ad35 vector performance and transgene persistence. These results suggest that incorporation of RGD in the fiber of Ad35 vectors may result in prolonged therapeutic effects which would reduce the frequency or need of intraocular administrations.
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