Jennifer Lovejoy, Arivale Chief Science Officer, PhD
Researchers at Mt. Sinai in New York were trying to find differences between healthy brain tissue and the brain tissue of people with Alzheimer’s disease when they made an accidental and surprising discovery, NPR reports.
They found the brains of people with Alzheimer’s had levels of two human herpes viruses – HHV-6 and HHV-7 – up to twice as high as those in the brains of people without the disease. They published their findings this month in Neuron.
Those findings appear to show that the two common herpes viruses – better known for causing a skin rash called roseola in children younger than 2 – are involved in Alzheimer’s.
The study suggests herpes viruses crossed into brain tissue and were able to interact with genetic variants in the brain known to increase a person’s risk for Alzheimer’s. Researchers also found these Alzheimer’s risk variants appear to make a person’s brain more susceptible to infection with the two herpes viruses.
Researchers have long suspected that bacteria and viruses may be involved in how Alzheimer’s develops. Hundreds of reports have suggested an association between Alzheimer’s and a number of bacteria and viruses, some of which singled out the herpes virus specifically.
But unlike prior studies, researchers were able to demonstrate an association between these two specific herpes viruses and Alzheimer’s and found evidence the viruses may interact with the brain in a way that might speed up the progression of Alzheimer’s.
Of course, it’s important to note that a direct, causal relationship has not been established between the herpes viruses and Alzheimer’s. Doing so has been difficult because Alzheimer’s has a long disease course and researchers don’t have the ability to routinely test the brain tissue of those involved, making it hard to follow the disease course over time.
While NPR states the findings suggest it may be possible that antiviral drugs could one day be used to prevent Alzheimer’s, evidence suggests Alzheimer’s is a multi-faceted disease, and it’s unlikely targeting just one risk – such as a viral infection – is going to prevent the disease. There are many factors beyond genetics and viral infections that have been associated with Alzheimer’s, including diet, physical activity, social interaction, education level, and cardiovascular disease, among other things.
One clinical feature in Alzheimer’s is the formation of plaques and neurofibrillary tangles in the brain. Unfortunately, reducing the plaques once they’re already established has not shown promise in reducing the symptoms of Alzheimer’s.
This study suggests that viruses may increase plaque formation as well as alter the immune system. Clearly, it’s not realistic to avoid viruses over the course of a lifetime, and having a history of a herpes viral infection does not mean you’re going to carry an increased risk for Alzheimer’s disease.
The take-home message is that viruses may be one of a litany of influencing factors on the development or perhaps the acceleration of Alzheimer’s.
This research is promising in that it presents a novel approach to the treatment of a condition that, at this time, has no cure. In the meantime, there’s good evidence that healthy lifestyle habits – good nutrition, exercise, and managing stress – as well as keeping socially and mentally active may help prevent or delay cognitive decline with aging.
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[Arivale Hot Topics address health stories currently in the news. The Arivale Clinical Team’s commentary on these news articles is not a review of the scientific evidence, nor an endorsement of a specific study, and is not meant as official medical opinion.]