Choroideremia is caused by a mutation in the CHM gene on the X chromosome and affects an estimated 1 in every 50 000 people. The condition causes progressive loss of vision due to degeneration of the choroid, retinal pigment epithelium, and retina. There is no treatment for choroideremia and eventually the photoreceptor cells-the rods and cones in the retina that respond to light by sending signals to the visual processing areas of the brain-also degenerate leading to complete blindness by middle age.
"The cellular degeneration in this disease is fairly slow, providing a reasonably large window of time in which to intervene before the onset of visual loss"*, explains Professor
MacLaren and colleagues assessed the effect of gene therapy on retinal and visual function in six patients aged 35-63 years with different stages of choroideremia. They injected patients' retinas with a vector-a genetically engineered adeno-associated virus (AAV)-to deliver a corrective copy of the gene into the appropriate part of the eye to halt photoreceptor cell death.
The treatment caused no harm and resulted in improvements in subjective measurements of vision. Six months after delivery of the gene, all patients recovered their visual acuity from before the procedure, and two patients showed substantial improvements in how well they could see, with one reading over three additional lines on an eye chart. Importantly, the patients developed increased sensitivity to light, compared to a loss in sensitivity in the untreated eyes.
According to Professor MacLaren, "This is first time that gene therapy has been used to treat patients with normal visual acuity before the onset of clinically significant retinal thinning. Our findings hold great promise for gene therapy to prevent loss of sight in other retinal diseases such as age-related macular degeneration."*
Writing in a linked Comment,
Keywords for this news article include: Biotechnology, Lancet, Genetics, Blindness, Treatment, Eye Diseases, Gene Therapy, Choroideremia, Bioengineering, Vision Disorders, Sensation Disorders, Nervous System Diseases, Neurologic Manifestations.
Our reports deliver fact-based news of research and discoveries from around the world. Copyright 2014, NewsRx LLC
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