December 29, 2000

Continued research on an experimental Alzheimer's vaccine, which last year was shown to block the formation of beta amyloid peptide plaques in mice, has indicated that it may be helpful for treating memory loss as well.

Reported in Nature magazine, two independent studies (at the University of South Florida in Tampa and the University of Toronto) found the vaccine can largely ward off memory loss in mice stricken with a similar disease. ``This potentially could be a major breakthrough for us,'' said Zaven Khachaturian, senior science adviser to the Alzheimer's Association.

But he stressed that treatments that work in mice do not necessarily help people and that the mouse research did not deal with some key mental abilities lost in Alzheimer's, such as language and judgment.

The studies used strains of mice that develop beta amyloid plaques in their brains, along with measurable memory deficits, because of the genes they carry.

The researchers used different versions of a procedure in which the mice swam until they learned the location of an underwater exit platform. The animals were then tested to see how well they remembered where the platform was. Alzheimer's patients frequently have trouble remembering locations and how to get to places.

Both studies found that mice that had been repeatedly vaccinated performed markedly better than the untreated plaque-forming mice in the memory tests. On some occasions they did as well or nearly as well as ordinary mice.

As well as raising optimism that the vaccine is as effective on behavior as it is on reducing plaque build-up, the latest trials reinforce the theory that the plaque and dementia are in some way linked.

The vaccine is already being tested for safety in people. This past July, drug company scientists announced that preliminary results in human patients indicated the vaccine was safe. Those tests were not designed to assess any effect on symptoms.

The researchers who carried out the mouse studies said it is not clear why the vaccine protects memory.

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