For decades, the idea that a bacteria or virus could help cause Alzheimer’s disease was dismissed as a fringe theory. But not so much anymore. On [July 11], a team of researchers from Harvard Medical School reported in the journal Neuron the latest bit of evidence suggesting herpesviruses can spark the cascade of events that leads to Alzheimer’s disease, a fatal form of dementia that afflicts at least 5 million Americans.
The researchers studied how neurons in mice responded to the presence of herpes simplex 1 (HSV-1), the virus that causes cold sores. In a separate experiment involving a 3D model of the human brain grown in a dish, they also studied human herpesvirus 6 (HHV-6), the germ responsible for causing the childhood skin disease roseola.
In the current study, both viruses seemed to provoke an identical reaction. The mice’s brains grew new deposits of amyloid-β plaques practically “overnight,” according to senior author Rudy Tanzi, a geneticist.
Viruses are only one of the things that could set off Alzheimer’s, he pointed out. The same sort of seeding might happen in people whose genes cause them to make too much amyloid-β, in the absence of infection. And genetics might help explain why only some people’s infections cause the brain to start producing amyloid-β en masse. “Just having the virus isn’t enough,” Tanzi said.
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