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Thursday, 1 March, 2001, 11:06 GMT
Alzheimer's breakthrough raises cure hope
Elderly man BBC
Alzheimer's usually afflicts elderly people
Scientists have developed a way to rid the brain of the deposits that are thought to cause Alzheimer's disease.

They hope that successful tests on mice could eventually lead to a treatment for the incurable degenerative condition.

A team from Massachusetts General Hospital, US, used antibodies to destroy the deposits - known as amyloid plaques - that had been created in the brains of laboratory mice.

Other work on a vaccine has concentrated on preventing the formation of amyloid plaques - rather than their destruction.

Amyloid plaques are made up of a tangle of proteins. They collect in the brains of Alzheimer's patients, gradually killing off more and more brain cells.

A new imaging technique enabled the scientists for the first time to track the impact of the treatment on the brains of the mice while they were still living. It showed that 70% of the plaques had disappeared within eight days.

Until now, it has only been possible to confirm the presence of plaques in the brain at post mortem.

The scientists used a multi-photon microscope to beam infrared light deep into the tissues of the brain without causing any harm. This enabled them to detect flaws, or lesions, in the brain that are usually too small to be seen.

Antibody solution

The scientists painted an antibody solution on to the brains of mice bred to develop amyloid plaques. The antibodies were tagged with fluorescent markers to enable them to be picked up under the microscope.

Neurologist Dr Bradley Hyman said: "Three to eight days later, in the group that was treated, more than half the plaques were gone.

"In the group that was not treated, we could find 80% of the plaques we saw before."

Dr Hyman stressed that much more work was needed before the technique could be applied to humans. The microscope is not currently able to penetrate through the thickness of the human skull.

Also, it is very difficult to test mice for actual symptoms of Alzheimer's to ascertain whether the disappearance of the plaques actually leads to a change in behaviour.

Dr Hyman said: "We really view this as more of a proof of principle that the plaques are potentially reversible rather than as model for direct and therapeutic applications."

The researchers believe the antibodies are able to destroy the plaques by attracting cells called microglia - the brain's equivalent of immune system cells called monocytes.

Dr Richard Harvey, director of research at the UK Alzheimer's Society, warned that amyloid plaques were not the only cause of Alzheimer's in humans. The condition is also associated with tangles of nerve cells.

He said: "It is interesting that these antibodies have the potential to clear plaques from the brain rather than just prevent their formation.

"But we don't yet know whether preventing or clearing plaques is going to prevent or slow Alzheimer's in humans."

Dr Harvey also said that researchers would have to find a more suitable way to administer a vaccine to humans than by directly painting it on to the brain.

The research is published in the journal Nature Medicine.

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See also:

20 Dec 00 | A-B
Alzheimer's disease
21 Dec 00 | Health
Alzheimer's vaccine breakthrough
06 Nov 00 | Health
Alzheimer's: how mice beat it
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