Researchers from Arizona State University and Banner Alzheimer’s Institute have discovered a surprising link between a common virus and the development of Alzheimer’s disease in certain individuals.
This breakthrough, published in Alzheimer’s & Dementia, suggests that a chronic gut infection caused by cytomegalovirus (HCMV) could play a role in triggering Alzheimer’s in a specific subset of people.
HCMV is a member of the herpesvirus family, commonly contracted during childhood or early adulthood. Most people are exposed to it through bodily fluids, but it usually remains dormant and harmless.
However, the new research indicates that in some individuals, the virus stays active in the gut and may travel to the brain via the vagus nerve, which connects the digestive system to the brain.
Once in the brain, the virus appears to influence immune activity and contribute to changes associated with Alzheimer’s, such as amyloid plaques and tau tangles.
Dr. Ben Readhead, a lead author of the study, estimates that this subtype of Alzheimer’s could affect between 25% and 45% of patients with the disease.
“This form of Alzheimer’s shows the hallmark brain abnormalities but has a unique biological profile involving the virus, antibodies, and immune responses,” he explained.
The team’s findings are based on extensive research conducted in collaboration with multiple institutions, including the Translational Genomics Research Institute, Rush University Medical Center, and others.
They examined samples from the brain, spinal fluid, and intestines of Alzheimer’s patients, identifying traces of HCMV and its potential pathway to the brain.
The role of microglia, the brain’s immune cells, emerged as a crucial factor. These cells are designed to fight infections, but when overactivated, they can cause chronic inflammation and damage to neurons.
The researchers found that the presence of HCMV in the brain triggered microglia to express a gene called CD83, which is associated with this specific form of Alzheimer’s.
Further experiments using human brain cell models showed that HCMV exposure increased the production of amyloid and phosphorylated tau proteins—key markers of Alzheimer’s—and contributed to neuron damage.
These findings suggest that the virus may directly contribute to the disease’s progression in some individuals.
Interestingly, this form of Alzheimer’s seems to be linked to a chronic intestinal infection with HCMV rather than simple exposure to the virus, which is widespread.
While about 80% of people have antibodies to HCMV by age 80, only a subset shows signs of the virus in their intestines or brain. This indicates that most people exposed to HCMV are not at risk of this particular Alzheimer’s subtype.
The study builds on previous research that has long speculated about the role of infections in neurodegenerative diseases. Despite over a century of investigation, no single pathogen has been definitively linked to Alzheimer’s until now.
However, the researchers stress that their findings require further testing in independent studies to confirm the connection.
Arizona’s unique resources, such as the Brain and Body Donation Program at Banner Sun Health Research Institute, were instrumental in providing the tissue samples needed for this detailed investigation.
The ability to study multiple tissues from the same individuals allowed the researchers to trace the virus’s path from the gut to the brain and its systemic effects.
Looking ahead, the researchers are developing a blood test to identify people with chronic intestinal HCMV infections. This test, combined with new blood tests for Alzheimer’s biomarkers, could help identify individuals who might benefit from antiviral treatments.
The hope is that existing antiviral drugs could potentially treat or even prevent this form of Alzheimer’s disease.
“This discovery opens a new avenue for understanding and treating Alzheimer’s,” said Dr. Eric Reiman, the study’s senior author. “If we can confirm these findings, it could lead to meaningful advances in subtyping, prevention, and treatment.”
While much work remains, the research offers a promising step forward in uncovering how infections like HCMV may influence brain health and the development of Alzheimer’s in some people.
If you care about Alzheimer’s, please read studies about the likely cause of Alzheimer’s disease, and new non-drug treatment that could help prevent Alzheimer’s.
For more information about brain health, please see recent studies about diet that may help prevent Alzheimer’s, and results showing some dementia cases could be prevented by changing these 12 things.
The research findings can be found in Alzheimer’s & Dementia.
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