Gene Therapy Restores Vision in Dog

From: xgl (
Date: Mon Apr 30 2001 - 12:10:52 MDT

Friday April 27 5:01 PM ET
Gene Therapy Restores Vision in Dog

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

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

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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