Magazine article Science News

Alzheimer's Culprit May Fight Germs: Amyloid-Beta Protein Attacks Pathogens in Mice, Worms

Magazine article Science News

Alzheimer's Culprit May Fight Germs: Amyloid-Beta Protein Attacks Pathogens in Mice, Worms

Article excerpt

A notorious Alzheimer's disease villain may also be a germ-busting superhero. Amyloid-beta gums up the brains of people with Alzheimer's but also takes out brain invaders, scientists report in the May 25 Science Translational Medicine.

As strong as steel, tough strands of A-beta protein imprison pathogens that threaten the body and brain, experiments in mice and worms show. Those results raise the possibility that A-beta plays a role in the immune system and its accumulation in Alzheimer's might be prompted by infection.

Earlier studies have shown that A-beta can kill germs in lab dishes, but the new experiment shows A-beta protection in living mice and worms. Mice engineered to have the human form of A-beta survived a brain infection of Salmonella bacteria better than mice without the human A-beta, Robert Moir and Rudolph Tanzi, both of Harvard Medical School, and colleagues found. In worms, A-beta helped stave off the yeast Candida.

When researchers injected Salmonella into mice's brains, A-beta quickly sprang into action in the hippocampus, a brain area damaged in Alzheimer's. A-beta swarmed the microbes and formed aggregates called fibrils and plaques. "Overnight you see the plaques throughout the hippocampus where the bugs were, and then in each single plaque is a single bacterium," Tanzi says. That rapid response was surprising, he says. "No one expected that."

And those prisons are probably permanent, Moir says. "In A-beta, those fibrils set like concrete, and the bugs have no chance of ever getting out."

Alzheimer's has been linked to a host of bacterial, fungal and viral infections, says immunologist Kevan Hartshorn of Boston University School of Medicine. …

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