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Alzheimer's vaccine stopped plaque, not dementia

By MARIA CHENG

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AP

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LONDON -Some doctors have long suspected that if the plaque that builds up

in the brains of patients with Alzheimer's disease could be removed, they

could be saved. But a new vaccine that did just that suggests the theory is

wrong.

British researchers gave 64 patients with moderate Alzheimer's disease an

experimental vaccine designed to eliminate plaque from their brains. Some

patients were followed for up to six years.

Autopsies on seven patients who died of Alzheimer's during the study showed

that nearly all of the sticky beta-amyloid protein thought to be dangerous

had been removed. But all patients still had severe dementia.

" It may be that these toxic plaques trigger the neurodegeneration, but don't

have an ongoing role, " said Clive Holmes of the University of Southampton,

lead author, in a press statement. The study was published Friday in the

medical journal, The Lancet.

The study was paid for by the Alzheimer's Research Trust, a British charity.

Alzheimer's disease is the most common cause of dementia and affects about

25 million people worldwide.

Other experts said that the study's findings pointed to a major gap in our

understanding of the disease. Doctors have never been sure whether the brain

plaques are the cause of Alzheimer's disease or just a side effect.

" We still don't have enough understanding of what we should target, " said

Dr. Bengt Winblad, director of the Alzheimer's Centre at Sweden's Karolinska

Institute. Winblad was not connected to the study.

Aside from the plaque build-up, scientists also think that tangles of

another brain protein called tau play a major role in Alzheimer's. Because

those

tangles form later than the plaque, some experts think they should be the focus

instead.

" It may be harder to get a response from targeting plaque because that forms

years before people actually have Alzheimer's, " said Dr. Simon Lovestone,

professor of Old Age Psychiatry at King's College in London. " By the time you

do something, it may be too late. "

Winblad said there was a better connection between brain tangles and

Alzheimer's symptoms, but that no studies so far had looked at whether removing

tangles might improve or even reverse Alzheimer's disease in patients.

Still, experts say that attacking toxic plaque in the brain shouldn't be

abandoned just yet, since the formation of such plaques might be what sparks

Alzheimer's disease in the first place.

" Removal of the initial motor for the disease might slow progression, " wrote

H. St. -Hyslop and C. of the University of Cambridge

and the University of Toronto in an accompanying commentary in the Lancet.

Copyright 2008 The Associated Press. All rights reserved. This material may

not be published, broadcast, rewritten or redistributed.

2008-07-17 19:09:37

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