A new nasal vaccine for Alzheimer’s disease has cleared plaques from the brains of affected mice and will be tested in humans in 2006.

Most previous attempts to produce a therapeutic vaccine have involved antibodies against beta amyloid, a naturally-occurring protein which is widely considered to cause the disease. In Alzheimer’s patients, beta amyloid forms plaques that seem to destroy neurons. But the antibody approach ran into problems three years ago, when a promising vaccine trial was halted after 15 of 360 volunteers developed swelling in the brain.

Now Howard Weiner, at Brigham and Women’s Hospital in Boston, US, and his colleagues have tried a new strategy. Weiner was intrigued by the fact that brain inflammation in the earlier trial coincided with exceptional clearance of beta amyloid.

He did some experiments and found that mice with Alzheimer’s treated to develop multiple sclerosis-like brain inflammation also cleared the beta amyloid from their brains. “Sometimes inflammation is good,” he says.

His team discovered that in inducing inflammation they were activating cells in the brain known as microglia, whose job it is to ingest unwanted material. In this case, the microglia were ingesting the beta amyloid. Interestingly, in mice without beta amyloid plaques, no activation took place.

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