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BBC Breakfast Gene Therapy Interview with Prof. Ali

What are genes?
Genes are coded messages that describe how specific functions in each cell have to be done, e.g. there are genes that describe how to make the light sensitive machinery in the photoreceptor cells. If the gene is corrupted, this function can not be performed and the photoreceptor cells cannot detect light.

What is gene therapy?
Gene therapy aims to replace the mutated (corrupted) gene with a correct version in the cells where it is needed. To achieve this, we use viruses from which we remove the viral genes to make the virus harmless and replace them with the gene we want to put into the cells.

Gene therapy for photoreceptor defects
We were the first group to show that it is possible to repair a photoreceptor cell defect in mice using gene therapy. By injecting a viral vector containing a normal copy of the defective gene we were able to restore the structure and the function of the photoreceptor cells. Since then, we have been developing gene therapy in a variety of animal models of severe retinal dystrophy that also occur in patients, such as X-linked RP and certain forms of Leber’s congenital amaurosis (LCA).

Gene therapy for defects in the RPE
We have successfully managed to treat two animal models of RP caused by RPE defects with gene therapy. RPE defects that cause RP are relatively rare, but they have the advantage that the photoreceptor cells are inherently healthy and they should therefore survive if we can repair the RPE. In dogs with a defect in the RPE65 gene, we could not only show electric responses, but we could also detect a clear improvement in their ability to walk through a maze. This gave us definitive proof of improved vision after treatment.

Gene therapy for other diseases
Our group is also developing gene therapy for several conditions that are not caused by defects in a single gene, but may be due to a number of genetic or environmental factors. One example is blindness caused by the abnormal growth of blood vessels in the eye which occurs in diseases like diabetes and AMD. Another complex disease for which we are developing gene therapy is auto-immune uveitis, a disease in which the immune system damages the cells in the retina and which, if left untreated, will result in severe loss of vision.


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