Common viruses may be triggering the onset of Alzheimers disease: Shingles infection may activate dormant neurological herpes viruses, causing inflammation and accumulation of Alzheimers associated proteins in the brain

Alzheimer’s disease can begin almost imperceptibly, often masquerading in the early months or years as forgetfulness that is common in older age. What causes the disease remains largely a mystery.

But researchers at Tufts University and the University of Oxford, using a three-dimensional human tissue culture model mimicking the brain, have shown that varicella zoster virus (VZV), which commonly causes chickenpox and shingles, may activate herpes simplex (HSV), another common virus, to set in motion the early stages of Alzheimer’s disease.

Normally HSV-1 — one of the main variants of the virus — lies dormant within the neurons of the brain, but when it is activated it leads to accumulation of tau and amyloid beta proteins, and loss of neuronal function — signature features found in patients with Alzheimer’s.

“Our results suggest one pathway to Alzheimer’s disease, caused by a VZV infection which creates inflammatory triggers that awaken HSV in the brain,” said Dana Cairns, GBS12, a research associate in the Biomedical Engineering Department. “While we demonstrated a link between VZV and HSV-1 activation, it’s possible that other inflammatory events in the brain could also awaken HSV-1 and lead to Alzheimer’s disease.”

The study is published in the Journal of Alzheimer’s Disease.

Viruses Lying in Wait

“We have been working off a lot of established evidence that HSV has been linked to increased risk of Alzheimer’s disease in patients,” said David Kaplan, Stern Family Professor of Engineering and chair of the Department of Biomedical Engineering at Tufts’ School of Engineering. One of the first to hypothesize a connection between herpes virus and Alzheimer’s disease is Ruth Itzhaki of the University of Oxford, who collaborated with the Kaplan lab on this study.

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