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Gene Therapy Restores Vision in Dog
from the Associated Press

By MALCOLM RITTER, AP Science Writer

NEW YORK (AP) - Using gene therapy, scientists have restored vision in dogs with a version of a rare disease that blinds human infants. The work may lead to treatments for several genetic forms of blindness.

The dogs had a version of Leber congenital amaurosis, an untreatable condition that causes near total blindness in infancy. Perhaps 10,000 Americans have it, and about 1,000 of them have the particular genetic defect corrected in the dogs, said researcher Dr. Jean Bennett.

If the gene therapy works in Leber patients, it might pave the way for treating a variety of hereditary vision diseases that strike the retina, known collectively as retinitis pigmentosa, which affects 100,000 to 200,000 Americans, said Dr. Gerald Chader, chief scientific officer of the Foundation Fighting Blindness.

``It should open the floodgates,'' said Chader, whose organization helped finance the research.

Bennett, an associate professor of ophthalmology the University of Pennsylvania, and colleagues report their experiments on three Briard dogs in the May issue of the journal Nature Genetics.

She said she hopes initial experiments in people can begin within about two years.

The dogs were blind because they lacked a particular gene. Without it, their eyes could not make a pigment necesssary to perceive light. The therapy was designed to deliver working copies of the gene to their eyes.

Researchers used eye surgery to deliver a dose of the gene, carried by a virus that deposited the gene within eye cells. They treated one eye in each animal and used the other eye for comparison.

Four months after treatment, several tests showed the animals had regained at least some sight in the treated eye. Most dramatically, the dogs were allowed to wander in a room cluttered with furniture. The dogs were much better at avoiding objects on the same side of their bodies as the treated eye than on the other side.

The dogs also seemed to be using the treated eye to look around, Bennett said.

Researchers also measured how much the dogs' pupils contracted in response to light. The treated eyes showed a better response than untreated eyes did, although it was not as good as normal dog eyes show.

The treatment's effects have lasted nine months so far, Bennett said.

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Date last modified August 1, 2001