Solving This Viral Puzzle Unlocks Cause (And Maybe Treatment For) Alzheimer’s Disease

For years, scientists have struggled to understand the mysterious link between the herpes simplex-1 (HSV-1) virus and Alzheimer's disease. While laboratory tests suggested a connection, the exact mechanism behind the virus's role in brain damage remained elusive—until now. New research has uncovered a surprising twist in the puzzle: it’s not just HSV-1 at work, but a second viral infection that may trigger the virus to become destructive in the brain. Could this revelation change how we think about the causes of Alzheimer's and how to prevent it?

Key Takeaways

• Researchers have discovered that the varicella zoster virus (VZV), responsible for chickenpox and shingles, can reactivate dormant HSV-1 in the brain, potentially triggering Alzheimer’s disease.

• Both HSV-1 and VZV are incredibly common, with a significant portion of the global population carrying them dormant in their bodies.

• Vaccination for VZV, such as the shingles vaccine, may help lower the risk of Alzheimer’s by preventing the reactivation of HSV-1.

Shingles Vaccine: More Than Just Preventing Pain—Could It Protect Your Brain?

For years, researchers have been investigating what they believed was the link between the herpes virus and Alzheimer’s disease.

Laboratory tests have consistently shown that there was probably some sort of connection, but scientists have been stymied trying to untangle exactly how the presence of the herpes virus in brain tissue might bring on the neuronal damage that could lead to full-blown Alzheimer’s.

Finally, scientists believe they’ve discovered the missing part of the puzzle… another virus.

In the lab, scientists have been able to build models of mini-brains that demonstrate how an infection with the cold sore virus herpes simplex-1 (HSV-1) may set off processes among neurons that are characteristic of the destructive progress of Alzheimer’s disease in the human brain.

However, they’ve recognized that their grasp of what happens in the brain during this memory-robbing illness was incomplete.

For example, many people carry around copies of dormant HSV-1 in their bodies for years without the virus creating health problems of any sort. So, why would this virus sometimes rest harmlessly in brain tissue but at other times set off swaths of brain cell destruction?

The answer, according to research at Tufts, is that it may take a second viral infection to reawaken HSV-1. It is that reawakening that initiates the early stages of Alzheimer’s disease.

A Second Virus Triggers HSV-1 To Damage Memory 

Tests show that when the varicella zoster virus (VZV), which can cause chickenpox and shingles, arrives on the scene, it can stimulate HSV-1 to become destructive within the brain.1 What’s more, an VZV infection may not be the only inflammatory event that could set HSV-1 in motion.

“Our results suggest one pathway to Alzheimer’s disease, caused by a VZV infection which creates inflammatory triggers that awaken HSV in the brain,” says researcher Dana Cairns, PhD, who is in the Biomedical Engineering Department at Tufts. “While we demonstrated a link between VZV and HSV-1 activation, it’s possible that other inflammatory events in the brain could also awaken HSV-1 and lead to Alzheimer’s disease.”

Why You Are At Risk 

Unfortunately, statistics show that both viruses are widespread. The World Health Organization reports that among the 6.5 billion people around the world under the age of 59, more than half (3.7 billion) are infected with HSV-1. And half of all Americans carry the virus around in their bodies and may occasionally experience mild swelling and pain from the virus. Or it can remain quietly dormant for decades.

The VZV virus is even more widespread. It is estimated that about 95 percent of people around the world have been infected with it before the age of 20. Interestingly, VZV, which is also a type of herpes virus, can get into nerve tissues and remain dormant for prolonged periods.

As you grow older, VZV’s activity can cause shingles, a disease that gives rise to painful nodules and blisters on the skin. This isn’t rare: It takes place in about one in three people.

The Tufts researchers report that the Alzheimer’s danger arrives only after VZV leads to HSV-1 reactivation which, in turn, gives birth to blisters, sores and other inflammatory difficulties.

Dr. Cairns issues this warning, “It’s a one-two punch of two viruses that are very common and usually harmless, but the lab studies suggest that if a new exposure to VZV wakes up dormant HSV-1, they could cause trouble.

“It’s still possible that other infections and other pathways of cause and effect could lead to Alzheimer’s disease, and risk factors such as head trauma, obesity, or alcohol consumption suggest they may intersect at the re-emergence of HSV in the brain.”

Vaccines May Help Keep Alzheimer’s At Bay 

The Tufts researchers believe that the reduced risk occurs when the vaccine interrupts the process of viral reactivation, inflammation and neuronal damage that can lead to Alzheimer’s disease.

My take on this is that this research may convince a lot of people to get a shingles vaccine. But it also presents good evidence to, as I’ve often urged, keep your immune system strong by eating a healthy diet, limiting processed foods and getting consistent daily exercise. This helps protect you from any type of infection and is linked to a lower risk of all types of dementia.

Summary

Scientists have uncovered a potential new pathway to Alzheimer’s disease, where the herpes simplex-1 (HSV-1) virus, which often remains dormant in the body, may be triggered into action by the varicella zoster virus (VZV), which causes chickenpox and shingles. This viral "one-two punch" could lead to significant brain damage. With vaccines already available for VZV, they may offer more than just protection from shingles; they could also reduce the risk of Alzheimer's. The findings underscore the importance of keeping the immune system strong and potentially turning to vaccination as a preventive measure.

Frequently Asked Questions

What is the connection between HSV-1 and Alzheimer’s disease?

HSV-1, a virus that causes cold sores, has been linked to Alzheimer’s disease, with researchers finding it may contribute to neuronal damage in the brain.

How does the varicella zoster virus (VZV) play a role in Alzheimer’s?

VZV, which causes chickenpox and shingles, can reactivate dormant HSV-1, potentially triggering the process that leads to Alzheimer’s disease.

Can a shingles vaccine prevent Alzheimer’s disease?

Research suggests that the shingles vaccine may reduce the risk of Alzheimer’s by preventing the reactivation of HSV-1 triggered by VZV.

Are there other viruses that could trigger Alzheimer’s disease?

While HSV-1 and VZV are the focus of recent research, other inflammatory events or infections could also contribute to Alzheimer’s, though further research is needed.

How common are HSV-1 and VZV infections?

Both viruses are widespread, with over half of the global population carrying HSV-1, and nearly 95% of people being infected with VZV before age 20.