Non-Viral Gene Transfer to the Retina of Mice and Monkeys Following Intravenous Administration

Abstract

Abstract: : Purpose: The success of gene therapy is limited by the gene delivery system. A new approach to retina gene therapy enables the widespread expression of a therapeutic gene throughout the retina with intravenous non-viral gene transfer. Methods: The SV40 promoter expression plasmid encoding the exogenous gene, e.g., either luciferase or b-galactosidase, is encapsulated in the interior of pegylated immunoliposomes (PIL), which function as an artificial virus of about 85 nm in diameter. The PIL is targeted across the cellular barriers in the eye with a receptor-specific monoclonal antibody (MAb). The targeting MAb, which is conjugated to the tips of strands of polyethylene glycol projecting from the surface of the PIL, is directed at either the transferrin receptor (TfR) in mice or the insulin receptor (IR) in Rhesus monkey. Owing to expression of the TfR or IR on both the blood-retinal barrier and the plasma membrane of ocular cells, the PIL carrying the gene is delivered to the nuclear compartment of cells in the eye. Results: In mice, the b-galactosidase gene was expressed throughout the entire retina, with exception of the photoreceptor cells, following targeting with the TfRMAb-PIL. The reduced gene expression in the photoreceptor cells with the TfRMAb-PIL was correlated with minimal TfR expression in the outer nuclear layer (ONL). In contrast, diffuse gene expression in the photoreceptor cells and inner segments was observed in the primate retina following intravenous administration of the HIRMAb targeted PIL. Immunocytochemistry showed that the IR is expressed in the primate ONL (Fig.). Conclusions: This approach makes feasible adult transgenics in 24 hours, and enables the delivery of therapeutic genes throughout the entire retina without viral vectors or ocular injections. Fig.: ß-Galactosidase histochemistry of the monkey retina reveals widespread gene expression.  

Keywords: gene transfer/gene therapy • retina • blood supply