Inhibition of experimental choroidal neovascularisation by lentivirus mediated delivery of pigment epithelium derived factor

Abstract

Abstract: : Purpose: Current treatments for choroidal neovascularisation (CNV) are inherently ablative and of short–lived efficacy. Angiostatic gene delivery may provide long–term control of this aberrant neovascularisation after a single intraocular procedure. PEDF is a naturally occurring potent angiostatic that is pluripotent, counteracting not only VEGF, but also other proangiogenic stimuli such as FGF, PDGF and IL–8. We assessed the efficacy of PEDF gene delivery using a lentiviral vector in an improved model of CNV. Methods: HIV–1 vectors encoding PEDF under the control of a SFFV promoter were used (HIV.SFFV.PEDF). Vector was administered subretinally into the right eyes of C57bl/6J mice. As controls, other mice were injected with PBS, or vector encoding eGFP (HIV.SFFV.eGFP). The left eyes in all groups were not injected and served as internal controls. A diode laser was used to focally rupture Bruch’s membrane in all eyes 1 week after subretinal injection. Early and late phase fluorescein angiography was performed 2 weeks after laser induction and the areas of the induced membranes quantified using image analysis software. Fluorescein leakage from these membranes was also quantified as an assessment of vascular permeability. Results: Subretinal delivery of HIV.sFFV.PEDF produced a 28% reduction in CNV area as compared with internal controls (p=0.03). No angiostatic effect was demonstrated in the HIV.SFFV.eGFP (p= 0.80), or PBS (p= 0.67) groups, as compared with internal controls. No deleterious effects on normal retinal vasculature were observed. Conclusions: Controlling CNV remains the major therapeutic challenge in patients with exudative AMD. Adenovirus (Ad) and adeno–associated virus (AAV) mediated delivery of PEDF has been shown to have an inhibitory effect on experimental CNV. Intraocular transgene expression with Ad vectors is short–lived. However, it is likely that sustained angiostatic gene expression will be necessary to inhibit the proangiogenic stimuli in patients with CNV. In addition, it is desirable to limit transgene expression to the abnormal vascular endothelial cells, or to the adjacent RPE. We have previously demonstrated efficient sustained RPE specific transgene expression using an HIV–1 vector with minimal adverse effects. This specificity, and higher levels of transgene expression as compared with AAV vectors, make the HIV–1 vector a potentially highly attractive vehicle for delivering angiostatic genes in patients with CNV.

Keywords: gene transfer/gene therapy • choroid: neovascularization • age–related macular degeneration