Adeno-Associated Virus As A Vector

One of the obstacles to successful cell-replacement therapy is apoptotic death of donor cells following transplantation [3, 5]. Adult retinal stem cells (RSC) were recently discovered in mammals [1, 7, 25] and could be harnessed to treat retinal degeneration disorders. However, first these cells must be successfully delivered to the diseased eye. A potential solution to the loss of transplanted tissue is over-expression of an anti-apoptotic protein by adult RSC, which would render the cells resistant to post-transplant apoptosis. The desired protein can be delivered to the cells via a viral vector, such as adeno-associated virus (AAV). AAV is a commonly used viral vector because it is not associated with any known disease and, in the absence of its helper virus, it integrates its genome into that of the host. There are different strains of AAV associated with varying infection efficiencies in different target cells [14]. To determine which strain is best suited to deliver exogenous genes to adult RSC, infection with a panel of different serotypes encoding green fluorescent protein (GFP) was attempted on mouse- and rat-derived RSC. After 45 minute viral incubation with AAV serotypes 1, 2, 5, 7 or 8, none of the mouse- or rat-derived retinal stem cells displayed fluorescence, indicating unsuccessful infection. Following 18 hour vial incubation with AAV serotypes 1, 7 or 8, positive infection was detected with serotype 1 in both cell lines. The method of delivery has to be further perfected; nonetheless, serotype 1 of AAV proved to be the optimal vector for adult RSC infection and thus for delivery of exogenous genes, such as those encoding anti-apoptotic proteins. This, in turn, may hold a promise for new lines of therapy for retinal degeneration.