Molecular Therapy Tested on Cats with Naturally Occurring Degenerative Disease

Human and veterinary researchers successfully completed gene transfer research on six cats with alpha-mannosidase (AMD), an inherited disease that affects children, cats, guinea pigs and cows, in what might be the first surgery of its kind on cats. The research, which was published in the March 2005 issue of Annals of Neurology, could open a new field of therapy that does not rely on surgery or drugs, said Charles Vite, DVM, PhD, lead author. "With gene transfer we can replace proteins and fix the disease," Vite said. "It’s a pipe dream right now but there is hope."

Vite and four researchers from the University of Pennsylvania veterinary school, the Children’s Hospital of Philadelphia and the Naval Academy have been working on a treatment for progressive neurological degenerative diseases for the last six years. A fairly rare disease, AMD affects Persian cats as well as other cats, and is similar to other degenerative diseases that affect one in 5,000 children. Diseased cats do not make the mannosides protein, which affects sugar storage in the brain and spinal cells. Symptoms include tremors that start at five weeks and worsen over time. Most cats do not live past six months of age, Vite said. In humans the disease causes skeletal irregularities and mental retardation.

To treat the disease in cats, researchers injected a cloned mannosides gene into the brain of six eight-week-old lab animals that had been bred for the research. The gene was injected into brain cells so that the cells would reproduce, and diminish neurological signs of the disease. Cats were euthanized at six-month intervals to compare results of the treatment, and all of them showed signs of improvement, including less swelling of neurons and improvement of white matter, Vite said. One cat lived to be a year old. Researchers are not sure whether the disease stymies formation of white matter but they have found that the injected protein allows it to form, Vite said.

It will be at least two years before researchers can determine whether the therapy causes side effects and how long gene therapy is effective, but Vite is optimistic about future uses for gene therapy. "We want to get to the point where the therapy is safe and efficacious so that cats have a longer life without any signs of the disease," he said.

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