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Alzheimer's Immunization Improves Mouse Memory

Single dose works even though no plaque is reduced

MONDAY, April 8, 2002 (HealthDayNews) -- Just one dose of a new Alzheimer's immunization appears to reverse some memory loss in mice.

Researchers were surprised to find that the rodents' memory improved even though the amount of abnormal protein deposits known as plaques were not reduced, says a new study in the May issue of Nature Neuroscience.

"We find that you don't need to reduce the plaques in order to improve memory," said Kindra Strupp, a spokeswoman for Eli Lilly and Co. in Indianapolis. The study was conducted by researchers from Lilly, Washington University School of Medicine, and Louis Pasteur University.

Substances known as plaques and tangles are present in the brains of all Alzheimer's patients. Researchers suspect that plaques and tangles interfere with normal neuron function. But many people without Alzheimer's also have plaques and tangles, leaving scientists unsure of the exact role they play in the brain disease.

Plaques are largely made up of a protein called beta amyloid. This is considered "deposited" beta amyloid, and there is also a "soluble" form of beta amyloid in the brain.

The research team injected an antibody, called m266, into mice that were genetically engineered to have an Alzheimer's-like disease. After only one day, memory was improved in the mice.

The researchers theorize that the antibody attaches itself to soluble beta amyloid and helps to clear it out of the brain. This suggests, according to the study, that beta amyloid may be causing neurological and memory problems even before the plaques form.

Not everyone agrees with this theory, however.

Aryeh Routtenberg, a professor of psychology and neurobiology at the Institute for Neuroscience at Northwestern University in Evanston, Ill., believes this study "illustrates very clearly that beta amyloid are suspect as a model for Alzheimer's."

Routtenberg suggested that perhaps the antibody is having a stimulating effect on the memory, much like an amphetamine does to the body.

Four million Americans have Alzheimer's disease, according to the Alzheimer's Association. That number is expected to jump to 14 million by 2050. One in 10 Americans over 65 and about 50 percent of those over 85 years of age have the incurable disease.

Strupp said she didn't know if there were any significant side effects in the mice from the treatment, but explained that this type of immunization, known as passive immunization, generally has fewer side effects.

In passive immunization, the antibody is injected directly into the body to do its work, whereas a standard vaccine stimulates the body to launch an immune response by developing its own antibodies.

Strupp cautioned that this research is still in the early stages. "We can't extrapolate to humans at this point," she said.

Last month, human trials of a different Alzheimer's vaccine, produced by Elan Corp. and Wyeth-Ayerst Laboratories, were halted when it was discovered that the vaccine was provoking a potentially deadly immune system response in some patients.

What to Do: If you'd like to learn more about plaques and tangles and their suspected role in Alzheimer's disease, read this information from the Neurology Channel or this article from the University of Washington.

SOURCES: Kindra Strupp, spokeswoman, Eli Lilly and Co., Indianapolis; Aryeh Routtenberg, Ph.D., professor of psychology and neurobiology, Institute for Neuroscience, Northwestern University, Evanston, Ill.; advanced online edition May 2002 Nature Neuroscience
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