Herpes may cause Alzheimer's, study says
Alzheimer’s can be caused by a herpes virus that travels from the gut to the brain, and it may be responsible for up to 45% of cases, new research suggests.
What did the study find?
Scientists found evidence of cytomegalovirus or HCMV in the brains of people who had died with the neurodegenerative disease.
HCMV is one of nine herpes viruses, although it is not considered a sexually transmitted disease. Most people are exposed to HCMV before they are 40, but it generally lives dormant in the gut.
Looking at post-mortem brains of Alzheimer’s patients, however, the team found the virus in their intestines and the vagus nerve, a vital communication pathway between the gut and the brain.
Because of this, scientists think that in some cases the herpes virus may be active and travel to the brain via the vagus nerve. There, HCMV seems to activate the immune system, contributing to the creation of amyloid plaques and tau tangles that stop brain cells communicating.
Researchers also found that those with the intestinal infection had more immune cells linked to inflammation than those without, while their spinal fluid contained antibodies against HCMV.
How is the herpes virus spread?
HCMV is usually spread through exposure to bodily fluids and is only passed on when the virus is active.
'We think we found a biologically unique subtype of Alzheimer’s that may affect 25 to 45 per cent of people with this disease,' said Dr Ben Readhead, an expert in neurodegenerative disease at Arizona State University.
'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.'
What is being done to prevent Alzheimer's?
The researchers are working now on a blood test to identify individuals with the chronic intestinal infection so that they could be treated with antivirals to prevent Alzheimer’s.
Dr Eric Reiman, the study’s senior author and the executive director of Banner Alzheimer’s Institute in Arizona, said: 'We’re excited about the chance to have researchers test our findings in ways that make a difference in the study, subtyping, treatment and prevention of Alzheimer’s disease.”
Dr Sheona Scales, the director of research at Alzheimer’s Research UK, said: 'This small study found a virus that causes a persistent gut infection may change the immune system, possibly driving the disease processes behind Alzheimer’s. While it’s too early to say for sure what this means, it could help explain some of the earliest changes that lead to Alzheimer’s.
'Importantly, this research opens new possibilities for future treatments and ways to diagnose the disease.'
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