Were blind, but now dogs see


Bennett’s team tried the gene therapy on mice like the one on her shoulder before successfully repeating it in dogs like Lancelot (in photo behind her right arm). Bennett took Lancelot with her to Washington when she testified before Congress about the procedure May 23.

Photo by Daniel R. Burke

Every once in a while, medical researchers come up with treatments for diseases that can truly be called miraculous.

Jean Bennett, assistant professor of ophthamology, recently performed one of those once-in-a-while miracles.

Bennett is part of a team of scientists studying the use of gene therapy to treat a rare eye disorder called Leber congenital amaurosis (LCA), which makes infants permanently blind. And this month, her team reported that they had successfully restored sight to dogs suffering from the same disease.

“The results were just astounding. We didn’t expect anything nearly as dramatic as what we saw,” Bennett said.

Bennett’s team already had extensive knowledge of the genetic defect that caused LCA, thanks to a decade of research into the disease. LCA occurs when a protein needed to deliver a vitamin A-like substance to retinal cells is missing from genes. In addition to humans, mice and dogs have been found to have the genetic defect.

Scientists had already reversed blindness in mice with LCA using gene therapy to deliver the missing protein. But that did not guarantee success in larger animals.

Bennett’s husband, Associate Professor of Ophthamology Albert Maguire, used the same surgical procedure he perfected in mice to inject a virus carrying the missing protein into the retina of one eye of each of the dogs in the experiment.

“We had expected only a small increase in the retinal signal at a very low level,” Bennett said. Instead, they found a huge increase.

“We also spoke with the animals’ caretakers, and they said, ‘Every time we pass these dogs, they’re watching us.’”

Obstacle-course tests confirmed the success of the therapy.

Since the results were published in the May issue of Nature Genetics, “the news spread like wildfire,” she said. “I’m getting hundreds of calls and e-mails from people around the world with children who have this disease, and they understand what the implications are.”

The 46-year-old mother of three sympathizes with them. “I can relate when [people] call saying they’d do anything for their child. I know I’d do anything for mine.”

Bennett also said that owners of dogs suffering from the disease have called to ask about the therapy. “We know this works for the Swedish briard, but we need to know more about the gene structure of other breeds.”

Bennett’s team has a way to go before it can test the treatment on humans. First they want to make sure the reversal is permanent. Then they want to repeat the experiment on other breeds of dogs, making sure that the therapy is safe. “These studies will take at least two years,” she said.

But she is confident that she will be able to give all those people contacting her good news eventually. “I feel that we haven’t given these people unrealistic hopes,” she said. “They also appreciate that there’s someone working on this.”

Originally published on May 31, 2001