Over 30 million people around the world are living with Alzheimer’s disease, the most common type of dementia. Sadly, there’s no cure yet, and treatments only help with the symptoms. But my latest review brings new hope.
It presents strong evidence suggesting that the herpes virus might be a cause of Alzheimer’s. This means that antiviral drugs, which are generally safe, could potentially treat the disease. We might even be able to develop a vaccine to protect our children in the future.
The virus in question, herpes simplex virus type 1 (HSV1), is mostly known for causing cold sores.
It infects most people when they’re young and stays dormant in the peripheral nervous system, which is everything but the brain and spinal cord. Stress can activate the virus, leading to cold sores in some people.
Back in 1991, we discovered that HSV1 is present in the brains of many older people. And in 1997, we found that HSV1 in the brain is a strong risk factor for Alzheimer’s, especially in people with a particular gene called APOE4.
It seems that the virus can activate in the brain, maybe more than once, causing damage over time. The risk of getting Alzheimer’s is 12 times higher in people who have both HSV1 in their brain and the APOE4 gene, compared to those with neither.
Further research showed that HSV1 infection in cell cultures leads to the buildup of beta-amyloid and abnormal tau proteins. These are the same proteins that accumulate in the brain in Alzheimer’s disease.
We think HSV1 plays a big role in Alzheimer’s. As people age, their immune system weakens, allowing the virus to enter the brain and establish a dormant infection.
Stress, a weakened immune system, and inflammation caused by other infections can reactivate the virus. This reactivation can directly damage infected cells and cause inflammation.
For people with the APOE4 gene, this repeated activation could lead to Alzheimer’s, possibly because of more toxic products formed by HSV1 or less repair of damage.
What about new treatments? The data suggest that antiviral drugs, which stop new viruses from forming, could be used to treat Alzheimer’s.
In an earlier study, we found that acyclovir, an anti-herpes drug, blocks HSV1 replication and reduces beta-amyloid and tau levels in infected cell cultures.
It’s crucial to remember that all these studies, including ours, only show a link between herpes and Alzheimer’s. They don’t prove that the virus is the direct cause.
The best proof would be to show that Alzheimer’s can be greatly reduced by either targeting the virus with antiviral drugs or by vaccinating against it.
Interestingly, a large study in Taiwan showed successful prevention of Alzheimer’s using specific anti-herpes agents. We hope that data from other countries will show similar results, bringing us closer to understanding and potentially treating this devastating disease.
If you care about brain health, please read studies about vitamin D deficiency linked to Alzheimer’s and vascular dementia, and blood pressure problem at night may increase Alzheimer’s risk.
For more information about brain health, please see recent studies about antioxidants that could help reduce dementia risk, and epilepsy drug may help treat Alzheimer’s disease.
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