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Like a Prion, Alzheimer's Protein Seeds Itself in the Brain
Posted: Tuesday, July 17, 2012 11:17 PM
Joined: 12/6/2011
Posts: 3326

From Alzheimer's Daily News:

(Source: ScienceNews) - The Alzheimer's-related protein amyloid-beta is an infectious instigator in the brain, gradually contorting its harmless brethren into dangerous versions, new evidence suggests. This study adds to the argument that A-beta is a prion, a misfolded protein that behaves like the contagious culprits behind Creutzfeldt-Jakob disease in people, scrapie in sheep and Mad Cow Disease.

There's no evidence that Alzheimer's can spread from person to person, but thinking of Alzheimer's as a prion disease could change the way researchers approach treatment and prevention strategies. The results may also raise troubling implications for people who participated in a clinical trial in which they received a form of A-beta made in the lab.


In this study, researchers injected purified A-beta protein to seed one side of mice's brains and monitored it with a fluorescent molecule that became visible as the protein accumulated. After about 300 days, the A-beta had accumulated throughout the brain, similar to what happens in Alzheimer's. "It really does spread," said Kurt Giles of UCSF. "We inoculate in one part of the brain, but the pathology spreads through the whole brain."


It's not clear what form of A-beta is responsible for the prion-like activity. Small forms called oligomers or large clumps of fibrils could be to blame for the spreading. Nor is it known what accounts for the different potencies of the brain-derived and synthetic A-beta.


In a clinical trial halted in 2002, people with mild to moderate Alzheimer's were immunized with synthetic A-beta in an effort to clear their brains of A-beta buildup. If synthetic A-beta behaves like a prion, these people could face a heightened risk for A-beta buildup, Giles and colleagues wrote. There's currently no evidence of this, says pathologist Eliezer Masliah of the University of California(SD). "Even though it's something to be aware of, I think the likelihood of that is very small."


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