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WASHINGTON, April 27 (Reuters) - Doctors said on Friday they used gene therapy to restore the sight of blind dogs by injecting a virus carrying normal genes into the eye, and the technique soon could be used to make blind people see.

Giving new meaning to the idea of a seeing-eye dog, doctors at the University of Pennsylvania Medical Center's Scheie Eye Institute brought sight to three blind Briard puppies that were born with a variation of the human disease Leber congenital amaurosis (LCA). This severe form of degeneration of the retina renders human infants blind.

Dr. Jean Bennett, who led the study, said she hoped that the first human clinical trial involving the technique would begin in about two years. She said she was "very optimistic" that gene therapy could restore the sight of babies with LCA.

"This is really the first demonstration that functional vision can be restored to an animal," Bennett said in an interview. "It's the first time that any kind of rescue of retinal degeneration has been demonstrated in a large animal with an eye anatomically similar to that of a human. It's really a big leap forward."

University of Florida and Cornell University experts helped in the research appearing in the journal Nature Genetics.

A RARE, INHERITED DISEASE

LCA is a rare, hereditary disease caused by mutations in a gene important for eye function. About 2,000 people in the United States suffer from LCA, which currently is untreatable and results in blindness from birth or shortly thereafter.

Normally, a protein transports a Vitamin A-like compound to the retina -- the structure in the back of the eye composed of layers of light-sensitive nerve cells onto which light is focused -- that is necessary for sight.

In some cases of animal and human LCA, the protein (called wild-type RPE65 gene) that transports the Vitamin A-like compound is missing, which results in blindness. Researchers earlier had established that an apparently harmless virus could be used to carry healthy copies of the RPE65 gene into the cells of the retina.

The mutated RPE65 gene causes an estimated 15 percent of LCA cases, with the rest attributed to other mutations.

The researchers nine months ago used a single injection to introduce thousands of copies of the corrective gene into the right eyes of the three young Briards. Their left eyes were untreated to test the success of the therapy.

The researchers called the results astonishing. They found that the function of the treated eye was similar to that of a sighted dog's eyes. The treated dogs were able to navigate through a maze, even when the lighting was dim. The treated dogs avoided collisions with objects in front and to the right (the side injected), but collided with objects to the left.

"MY GOD, IT'S SEEING SOMETHING"

"You look at these dogs and you say, 'My God, it's seeing something,"' said the University of Pennsylvania's Dr. Albert Maguire, a co-author of the study and Bennett's husband.

"The ones that don't get treated just sit in the corner ... because they don't want to walk into the wall. They're not dumb animals. They just sort of quietly sit there. The ones that are treated will actually get up and explore the room. They'll look at things. They'll look at you."

Maguire said the research team has asked the National Institutes of Health for a grant to proceed to testing the gene therapy technique in people with LCA. He said the treatment method potentially could be used in the future on other forms of retinal disease, such as macular degeneration.

"It works so well that this is the particular disease that we want to push to see if it can be a proof of principle in humans (that gene therapy can restore sight)," Maguire said.

Gerald Chader, chief scientific officer of the Foundation Fighting Blindness, which helped fund study, suggested that the work would satisfy the Food and Drug Administration's desire to see that a treatment is safe and effective in a large animal before granting permission to begin human clinical trials.

"Genetic medicine is now making things we could only once dream of a reality," Chader said in a statement.

18:30 04-27-01
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