Evaluation of Minimal EIAV Based Vectors for Intraocular Gene Tranfer

Abstract

Abstract: : Purpose: We have developed a non-primate lentiviral vector system based on the equine infectious anaemia virus (EIAV) that is able to transduce both dividing and non-dividing cells in vivo. In comparison to previously described lentiviral vector systems the latest EIAV vector system has been substantially optimised. The EIAV vectors have been minimised such that no EIAV accessory genes are required for virus production or are delivered to the target cells. In addition, these minimal vectors have no regions of homology thereby minimising the possibility of recombination to generate RCL (replication competent lentivirus). The aims of this study were to define the potential role of an EIAV based vector in ocular gene therapy. Methods: EIAV vectors carrying a GFP transgene driven by a CMV promoter were pseudotyped with either VSV-G or rabies envelopes. Following intravitreal, anterior chamber (AC) or subretinal administration in adult C57Bl-6J mice, the transduction profile was assessed by ophthalmoscopy and histologically at various time points up to 6 months following injection. Results: Subretinal injection resulted in efficient transduction of the RPE. Anterior chamber administration resulted in transduction of the trabecular meshwork and corneal endothelium. Transgene expression persisted for up to 6 months (the longest time point examined). No clinical signs of toxicity were seen on biomicroscopy and there was no histological evidence of an inflammatory cell infiltrate. Intravitreal administration did not result in transduction of any cells. Conclusions: AC administration of a minimal EIAV vector results in stable and efficient transduction of the corneal endothelium and trabecular meshwork and could therefore be used for treating corneal disorders and for delivering therapeutic molecules to the anterior segment. Subretinal injection results in stable and efficient transduction of RPE with relative tissue specificity and a minimal immune response. This is potentially valuable in delivering therapeutic genes for the correction of inherited RPE specific genetic diseases and to deliver neurotrophic factors in the management of acquired retinal diseases. There is also the potential role of this vector to deliver angiostatic molecules in the management of choroidal and retinal neovascularisation as the RPE is in close proximity to the sites of neovascularisation in these conditions.

Keywords: gene transfer/gene therapy • neovascularization • retinal pigment epithelium