Viruses may trigger Alzheimer’s

Study finds that certain viruses affect the behavior of genes involved in disease.

WASHINGTON — Viruses that sneak into the brain might play a role in Alzheimer’s, scientists have reported in a provocative study that promises to reignite long-debated theories about what triggers the mind-robbing disease.

The findings don’t prove viruses cause Alzheimer’s, nor do they suggest it’s contagious.

But a team led by researchers at New York’s Mount Sinai Health System found that certain viruses — including two extremely common herpes viruses — affect the behavior of genes involved in Alzheimer’s.

The idea that infections earlier in life might set the stage for Alzheimer’s decades later has simmered at the edge of mainstream medicine for years. It’s been overshadowed by the prevailing theory that Alzheimer’s stems from sticky plaques that clog the brain.

The new study has some specialists who never embraced the infection connection saying it’s time for a closer look, especially as attempts to block those socalled beta-amyloid plaques have failed.

The study also fits with mounting evidence that how aggressively the brain’s immune system defends itself against viruses or other germs may be riskier than an actual infection, said Alzheimer’s specialist Dr. Rudolph Tanzi of Massachusetts General Hospital.

Tanzi, with Harvard colleague Dr. Robert Moir, has performed experiments showing that sticky betaamyloid captures invading germs by engulfing them — and that’s why the plaque starts forming.

“The question remained, OK, in the Alzheimer brain what are the microbes that matter, what are the microbes that trigger the plaque?” said Tanzi, who had no role in the new research.

The team from Mount Sinai and Arizona State University discovered viral suspects — by accident. The study, funded by the National Institutes of Health, wasn’t hunting viruses but looked for new drug targets for Alzheimer’s.

The first clues that viruses were around “came screaming out at us,” said Mount Sinai geneticist Joel Dudley, a senior author of the research published in the journal Neuron.

The team found viral genetic material at far higher levels in Alzheimer’s-affected brains than in normal ones. Most abundant were two human herpes viruses that infect most people during childhood, often with no symptoms.

Since 1980, other researchers have linked a variety of bacteria and viruses, to an increased risk of Alzheimer’s.

The new study went further: Researchers used computer models to check how the viral genes interacted with genes, proteins and amyloid buildup

They found a lot of interactions, suggesting viruses could switch on and off Alzheimer’s-related genes.