| The eye represents an isolated and immune privileged region of the body where multiple gene polymorphisms have been identified. Therefore, gene therapy is an attractive therapeutic approach to ameliorate disease. Adenovirus has been used successfully in multiple clinical trials, has a large cloning capacity, does not integrate into genomic DNA, and is capable of expressing for long periods of time. The capsid of adenovirus has a fiber extending from the viral coat with a penton structure at the base of the fiber. These two structures are mainly what determine binding and entry of the virus into cells. Altering the fiber has been a successful way to re-direct the tropism of adenovirus towards the cell type intended for gene therapy.;Loss of RPE cells is characteristic of age related macular degeneration (AMD), the leading cause of blindness in people over 65. A low level but chronic inflammatory response of the innate immune system has been implicated in the progression of AMD. Specifically, activity of the alternative arm of the complement pathway has been observed. Genetic studies have identified that polymorphisms in complement regulatory proteins place individuals at an elevated risk for developing AMD. CD46 is a membrane bound complement regulator that is normally expressed on RPE cells with expression levels reduced in AMD patients.;A limitation to using a membrane bound complement inhibitor for gene therapy in AMD is that protection is limited to the site of expression. This can be overcome by designing an inhibitor that is secreted from cells. The optimal secreted inhibitor must be highly effective at blocking complement so that protection occurs even when the concentration of inhibitor is low, at sites distant from initial expression. It must also be small enough to readily diffuse through the eye.;Here we describe how we re-directed the tropism of adenovirus to specifically express in photoreceptors, the retinal cell type with the most polymorphisms, by altering the fiber/penton base and using a cell specific promoter. We also describe the first gene therapy approach to treating AMD using CD46 along with the first description of a novel secreted complement regulator. |
