Two new studies raise the possibility that a vaccine to counteract Alzheimer's disease may prove effective despite an earlier setback, according to a report in Nature Medicine.

Trials of the Alzheimer's vaccine were halted earlier in 2002 when some of the 360 patients developed inflammation in the brain.

The patients in the new trials were given a modified form of the vaccine designed to clear the tangles of amyloid-beta protein that cause the plaques found in the brains of Alzheimer's patients.

Previous research had shown that the vaccine cleared the plaques in mice and reversed symptoms of brain damage similar to that found in Alzheimer's disease patients.

Researchers at the University of Zurich have found that the human patients given the modified vaccine also accumulated antibodies against amyloid-beta, a critical step in getting rid of plaques. The vaccine did not affect a second form of amyloid-beta that occurs in the nerve cells of healthy people as well as Alzheimer's disease patients. An attack on the second, longer form of amyloid-beta could cause autoimmune disease and other complications.

In a second study, Canadian and German researchers found that the modified vaccine, when given to mice, generated antibodies against amyloid-beta by removing amyloid-beta from plaques. The vaccine worked well if the mice were injected with only a small portion of amyloid-beta. Researchers speculate that this more refined vaccine could bypass the inflammatory side effects in humans.

Other sources: Nature Medicine