Researchers Seek Vaccine to Prevent
Three new studies in
mice are giving weight to the idea that an Alzheimer's vaccine may work in
humans. Such a vaccine is already in the early stages of a study in humans, and
researchers say these latest findings in animals bolster the hope that a
vaccine may prevent or treat the devastating brain disease.
studies, published in the December 21/28 issue of Nature, demonstrate that
particular physical changes seen in the brains of Alzheimer's patients are
correlated with the memory loss and other symptoms of the disease. More
important, two of the studies showed that preventing the physical damage with a
vaccine may also prevent Alzheimer's symptoms.
The studies all involved
mice genetically engineered to display some of the characteristics of the human
Alzheimer's disease. In each study, investigators focused on substances call
beta-amyloid proteins, which are constituents of the "plaques" that accumulate
in the brains of Alzheimer's patients.
Experimental vaccines are
targeting the beta-amyloid proteins, with the hope that preventing amyloid
deposition may prevent or slow the development of some Alzheimer-associated
Dr. David Westaway of the University of Toronto, Canada, was a
co-author on one of the studies. He told Reuters Health that the first
experiments with beta-amyloid vaccines focused on whether they could keep
plaques from forming. These animal findings, he Said, show that vaccination may
prevent the "real clinical presentation" of Alzheimer's specifically,
certain types of learning and memory problems.
The principle behind that
Alzheimer's vaccine is similar to that of any vaccine. Researchers believe that
exposing people to a small amount of beta-amyloid protein will train their
immune systems to fight the build-up of plaques in the brain. Animal research
has already suggested vaccination may clear plaques. Now, Westaway said, there
is evidence that doing this prevents Alzheimer's-like symptoms.
don't know if this will happen in humans," he said. "But with mice, we now have
a proof of principle."
Westaway's team and another research group led by
Dr Dave Morgan of the University of South Florida in Tampa demonstrated that
vaccinated mice retained their ability to wend through a water maze, while
untreated mice showed declines. The treated mice also had a reduction in brain
In an editorial accompanying the reports, Paul F. Chapman of
Cardiff University, UK, calls the studies "cause for optimism." "Their results
support the previous observation of a reduction in the formation of amyloid
deposits," he writes. "But they go further, to show that immunization also
offers the mice some protection from the "spatial" learning deficits that
normally accompany plaque formation."
However, whether the vaccination
wards off other types of cognitive losses remains unknown, according to
Chapman. And, he notes, some researchers believe another protein called tau is
at least equally as important as beta-amyloid in Alzheimer's. If this is true,
Chapman writes, a beta-amyloid vaccine may be ineffective.
But if it is
effective in humans, according to West away, the first use will be in
preventing Alzheimer's. "We want to catch it early on," he said. "But it may be
possible to treat it in more advanced stages, too."
About 4 million
Americans have Alzheimer's disease, and experts predict that over the next 50
years that number will jump to 14 million if no effective prevention is
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