Every now and then I come across an article or hear a story on the news that makes me take a step back and realize how incredibly far the science of genetics has come. As of May 1, 2007, testing for a gene therapy treatment has begun that may lead to a cure for a type of blindness in humans called Leber's congenital amaurosis (LCA). LCA is described as “a type of inherited childhood blindness caused by a single abnormal gene [which] prevents the retina from detecting light properly, resulting in progressive deterioration and severely impaired eyesight.” Clinical testing in humans comes as a result of the amazing success of the treatment in dogs born with LCA. After treatment the dogs recovered enough sight to successfully navigate an obstacle course!
So, how does gene therapy work? As we all know by now, proteins and enzymes are the major players in every biological process occurring in our body. Genes are the code for creating these proteins, and when a certain gene is mutated or lacking, a genetic disorder can result. Specifically, LCA results from mutations in the RPE65 gene which codes for a protein needed by retinal cells in order to respond to light.
Gene therapy relies on the tricky nature of the virus. Viruses are capable of inserting their genome into the genome of the host which they are infecting. Scientists are able to modify the virus, (or “vector” when used in this capacity) removing harmful disease causing genes and replacing them with therapeutic genes. The virus can then be introduced to target cells where they infect and insert the desired gene. In the case of LCA, an adeno-associated virus is modified to carry the RPE65 gene. The vector is then injected through small incisions in the eye which allow access to the surface of the retina. Here the retinal cells can incorporate the viral genome into their own and begin producing the lacking protein.
The success of this treatment in humans is still unknown as trials are still in the works, but based on the success of the treatment in dogs, I think it is safe to get a little excited about the prospects of this therapy!
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