Oral herpes could cause Alzheimer’s disease, new study says. But how?
New research shows for the first time that the cold sore-inducing herpes virus might cause Alzheimer’s disease, sitting quietly in the brain for years before symptoms of memory loss or cognitive decline appear.
The new research could provide a long awaited answer to what causes the devastating disease, potentially leading to a treatment involving antiviral drugs, according to the study published Wednesday in the journal Science Advances.
“I don’t think anyone has shown these kinds of responses to [herpes type 1], not in a way that shows direct causality,” senior author of the study David Kaplan told Stat.
What started with skin cells from human foreskin turned into a mini brain on a dish, the study said.
The researchers then inserted the herpes virus, or HSV-1, into the lab-grown brain. Within days, the neural cells formed plaque-like globs, joined together in clumps and became inflamed, all while the neurons’ ability to send electrical signals — needed for mental processing — failed, according to the study.
All of the observed changes are well-known signs of Alzheimer’s disease, which begins in the part of the brain responsible for forming memories and spreads until other parts of the organ shrink and die, according to the U.S. Department of Health and Human Services.
“These were profound changes, and all these responses — the physiological changes and the functional degradation — are important for the disease,” Kaplan told Stat. “And these were just normal cells” that did not include genes known to raise the risk for Alzheimer’s.
But the scientists wanted to experiment further. They inserted a herpes drug called valacyclovir into the mini brain and found that the inflammation and plaque-like globs became less apparent, and the brain as a whole functioned better, according to the study.
This, the researchers said, provides a glimmer of hope for future strategies to treat Alzheimer’s.
About 50% to 80% of U.S. adults have oral herpes, according to Johns Hopkins Medicine, and about 90% of adults are believed to have been exposed to the virus by age 50.
Some people never develop symptoms, which look like blisters in the mouth area, but once infected, a person will always have the virus lying dormant inside of them, occasionally experiencing outbreaks.
“The herpes virus typically travels through a nerve to the skin, where it causes a cold sore,” according to Healthline. “In rare cases, however, the virus travels to the brain. “
The new research suggests the virus could be more than just cold sores. One researcher says the plaque build-up and inflammation are defensive responses to the herpes, instead of a consequence of the disease itself, according to neuropathologist Ruth Itzhaki of the University of Manchester in England, Stat reported.
The study opens doors to new potential treatments, given the current five drugs on the market for Alzheimer’s “don’t even affect the underlying disease,” the outlet said.
Although the study provides the first evidence of “direct causality of Alzheimer’s disease by herpes virus in a 3D human brain model,” the scientists aren’t sure what other factors, such as lifestyle, could determine who develops the disease and who doesn’t.
This story was originally published May 8, 2020 at 12:59 PM with the headline "Oral herpes could cause Alzheimer’s disease, new study says. But how?."
