| |
Scientists have used gene therapy to restore sight to blind dogs with the canine equivalent of a rare human vision disease. The results, reported in the May issue of Nature Genetics, may lead to a treatment for infants with a form of the disorder, Leber's Congenital Amaurosis (LCA), that is responsible for an estimated 1000 cases of blindness in the United States.
The disease results from defects in cells that help the retina make light-detecting pigments. Because a single gene is sometimes responsible, researchers decided to put working copies of the gene back into the body. In preliminary experiments, this gene therapy halted the degeneration of vision in mice. To see if the technique could be successfully applied to animals with more humanlike eyes, Jean Bennett at the University of Pennsylvania Medical Center began experiments in dogs that have LCA.
Bennett and her colleagues at Cornell University and the University of Florida transferred the working gene with a so-called adeno-associated virus, which had been crippled so that it would not replicate in the animals. Borrowing techniques from eye surgeons, the team delivered a small amount of virus directly to the diseased area. When previously blind puppies were tested 3 months after the injection, they had near normal vision. Though their performance on neural tests of vision was not quite as good as that of normal dogs, they were able to navigate an obstacle course flawlessly, while control dogs with LCA failed the test. The results seem to last: 9 months after the treatment, the dogs still perform well on the visual tasks.
This bodes well for humans. John Flannery, a vision scientist at the University of California, Berkeley, says that the experiments indicate that "actually treating Leber's patients is on the horizon" after decades of research. He predicts that techniques developed as the research proceeds into human testing in the next few years will allow doctors to rapidly develop treatments for patients with blindness resulting from other, more common genetic defects.
--JOSH GEWOLB
Related sites
Jean Bennett's home page
Site about Leber's Congenital Amaurosis
|
