Gut infections and cytomegalovirus may contribute to Alzheimer’s progression through inflammation.
Researchers from Arizona State University and Banner Alzheimer’s Institute have uncovered a potential connection between a common gut infection and Alzheimer’s disease in certain individuals. This discovery focuses on cytomegalovirus (HCMV), a virus that many people encounter early in life. While most individuals experience no symptoms or only mild illness, the virus may linger in the body in an active state, particularly in the gut. The findings suggest that in some cases, the virus might travel to the brain through the vagus nerve, a key pathway linking the gut and brain. Once there, the virus can trigger immune responses and other changes that are commonly associated with Alzheimer’s disease.
The researchers believe they have identified a unique subtype of Alzheimer’s disease that may account for a significant proportion of cases. This form includes hallmark features like amyloid plaques and tau tangles in the brain but also shows distinct biological markers related to HCMV, including specific antibodies and immune cell activity. The team’s findings have sparked new questions about the potential for existing antiviral drugs to treat or prevent this specific form of Alzheimer’s.
Key to this research was the role of microglia, the brain’s immune cells. Microglia are activated during infections to protect the brain, but prolonged activation can lead to chronic inflammation and neuronal damage. This inflammatory response has long been linked to neurodegenerative diseases, including Alzheimer’s. The team’s earlier work found that postmortem brains of Alzheimer’s patients were more likely to show a specific marker, CD83, on microglia. These findings hinted at a connection between immune responses in the brain and the presence of HCMV.
In this latest study, the researchers examined samples from patients’ intestines, brain tissue, and spinal fluid. They found evidence of HCMV infection and specific antibodies in these areas, further supporting the theory that the virus could play a role in triggering Alzheimer’s in certain individuals. The researchers also detected the virus within the vagus nerve, suggesting a possible route for the infection to travel from the gut to the brain. Using human brain cell models, they demonstrated that exposure to HCMV could lead to increased production of amyloid and tau proteins, both of which are closely linked to Alzheimer’s disease. Additionally, the virus’s presence caused neuronal damage and death in these models.
It’s important to note that while most people are exposed to HCMV during their lifetime, only a subset appears to develop the chronic intestinal infection linked to this potential pathway for Alzheimer’s. This means that exposure alone is not enough to cause concern. However, the findings build on a century-old hypothesis that infections might contribute to Alzheimer’s. Past efforts to identify specific pathogens have been inconclusive, but this study brings new clarity to the discussion.
The team is now working on a blood test to detect active HCMV infections in people with Alzheimer’s. This test could be used alongside other Alzheimer’s diagnostics to identify individuals who might benefit from antiviral treatments. Such an approach could open up new avenues for managing or even preventing the disease in those affected by this form.
This research was made possible by collaborations with institutions such as the Translational Genomics Research Institute, UMass Chan Medical School, and Rush University Medical Center. Arizona’s unique biorepositories provided critical samples, including brain and body donations, allowing researchers to study tissues from the same individuals. This comprehensive approach helped link gut infections to systemic and neurological changes associated with Alzheimer’s.
The findings highlight the importance of exploring how infections can influence brain health. While further research is needed to confirm these results and test potential treatments, the study represents a significant step forward in understanding Alzheimer’s. The researchers are hopeful that this work will inspire others to investigate the role of infections in neurodegenerative diseases, paving the way for new treatments that could improve the lives of those living with Alzheimer’s and their families.
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Chronic gut infection may play role in Alzheimer’s disease progression
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