Study links vaccine to higher stroke risk.(amyloid beta vaccine)

2002 DEC 11 - (NewsRx.com & NewsRx.net) -- In what may be a new warning sign about a once-promising therapy for Alzheimer disease, researchers report that in animal studies a vaccine that clears the brain of toxic deposits also tends to double the risk of stroke.

Researchers have been intensively studying the idea that the brain-destroying disease could be controlled by removing deposits of a toxic substance called amyloid beta that accumulates in the brains of Alzheimer disease patients, filling the spaces between cells.

While researchers are uncertain if amyloid beta is the cause of Alzheimer or the result of another mind-destroying process, some earlier animal studies found that a vaccine that prompts the body to remove amyloid beta was able to stop progression of the disease and even restore some brain function.

The promising results led an Irish pharmaceutical firm, Elan Corp., to test an amyloid beta vaccine on 360 human patients, but the clinical trial was suspended early in 2002 after 15 patients developed inflammation of tissues in the brain. Elan has since said it would no longer test the original vaccine, but will continue to monitor patients who received it.

Now a new study, appearing November 15 in the journal Science, suggested that a vaccine against amyloid beta may have other problems - a significant increase in bleeding in the brain.

Swiss, German and American researchers used a lab mouse strain that had been genetically manipulated to develop the major symptoms of Alzheimer disease, including the formation of amyloid beta.

The mice were injected with a vaccine that caused their bodies to make antibodies against amyloid beta. After 5 months, the researchers said there was a 23% reduction of the amyloid beta in the test mice compared with animals that did not receive the vaccine.