A team of researchers has discovered a surprising link between a chronic gut infection caused by a common virus and the development of Alzheimer’s disease in a subset of people.
The finding could lead to new ways to treat or prevent the condition.
It is believed most humans are exposed to cytomegalovirus or HCMV — during the first few decades of life.
Cytomegalovirus is one of nine herpes viruses, but it is not considered a sexually transmitted disease.
The virus is usually passed through exposure to bodily fluids and spread only when the virus is active.
According to the new research, in some people, the virus may linger in an active state in the gut, where it may travel to the brain via the vagus nerve — a critical information highway that connects the gut and brain.
Once there, the virus can change the immune system and contribute to other changes associated with Alzheimer’s disease.
If the researchers’ hypotheses are confirmed, they may be able to evaluate whether existing antiviral drugs could treat or prevent this form of Alzheimer’s disease.
They are currently developing a blood test to identify people who have an active HCMV infection and who might benefit from antiviral medication.
Dr Ben Readhead is co-first author of the study and research associate professor with ASU-Banner Neurodegenerative Disease Research Center in the Biodesign Institute at Arizona State University (ASU).
He said: “We think we found a biologically unique subtype of Alzheimer’s that may affect 25 per cent to 45 per cent of people with this disease.
“This subtype of Alzheimer’s includes the hallmark amyloid plaques and tau tangles—microscopic brain abnormalities used for diagnosis—and features a distinct biological profile of virus, antibodies and immune cells in the brain.”
The research team suggests that some people exposed to HCMV develop a chronic intestinal infection.
The virus then enters the bloodstream or travels through the vagus nerve to the brain.
There, it is recognised by the brain’s immune cells, called microglia, which turn on the expression of a specific gene called CD83.
The virus may contribute to the biological changes involved in the development of Alzheimer’s.
