Could a Virus Give You Alzheimer’s Disease?
When people contemplate how they want to die, very few vote for Alzheimer’s. Rather, we work crossword puzzles and learn languages and keep fingers crossed that bad genes and dissolute habits, or simple bad luck, don’t lead to our cognitive decline. But doing word games and having good genetics and so on may have less to do with your vulnerability to Alzheimer’s, it turns out, than whether you had a certain type of virus early in life.
Scientists have long suspected that microbes may have something to do with the genesis of Alzheimer’s Disease. While most Alzheimer’s research has focused on trying to find pharmaceutical cures for sticky amyloid plaque in the brain, the idea that a virus could be the primary trigger gained credence several years ago when researchers discovered that the brain tissue of Alzheimer’s victims were virtually swarming with certain types of herpes virus—including the type that causes cold sores in children—at levels up to twice as high as in those without Alzheimer’s.1 The more advanced the Alzheimer’s, the higher the level of viruses found.
The researchers hadn’t been looking for viruses and in fact were previously skeptical of the idea that microbes might play a role.2 They were investigating differences between normal brains and brains affected by Alzheimer’s in an effort to identify targets for new drugs, and after examining 950 human brains from four different brain banks, they came to the surprising discovery.
Lead researcher Dr. Joel Dudley of the Icahn School of Medicine at Mount Sinai Hospital in New York explains, “Viruses were the last thing we were looking for. But when we started analyzing the differences [between normal brain tissue and Alzheimer’s brain tissue], it just sort of came screaming out at us from the data.” The researchers at that point investigated 515 types of viruses to see if there was a connection and found that two strains, Herpes 6A and Herpes 7, always were far more abundant in Alzheimer’s-affected brains.
Up to 90 percent of the population had one of these forms of herpes during infancy, manifesting as a rash, although few know it.3 That doesn’t mean, however, that 90 percent of us will develop Alzheimer’s. The scientists suspect that the herpes virus may remain dormant in the victim’s system after infection but can be reactivated by certain types of stress later in life. Scientists aren’t clear how or why that reactivation occurs, although they found some evidence that the virus itself may be switching on Alzheimer’s-related genes.4 What they do know is that once switched on, the virus contributes to the build-up of plaque and tangles in the brain, perhaps because it triggers an immune response that causes inflammation associated with Alzheimer’s.
According to an article published recently in the journal Neuron, the researchers don’t think viruses by themselves cause Alzheimer’s, but rather, that viruses cause brain cells to work in ways that accelerate the disease. Some scientists think there still isn’t enough evidence to support the idea that viruses play a key role in Alzheimer’s development. They suggest that the herpes virus might proliferate in Alzheimer’s-ridden brains after the fact because the brain is weakened and more susceptible to infection. But, another new study may change their minds. The study, also reported in Neuron, involved mice who were exposed to herpes. After exposure, the mouse brains started a protective reaction centered on the amyloid protein in the brain, and that in turn triggered the formation of plaques.
Scientists believe other types of microbes also can serve as triggers, including bacteria that cause walking pneumonia and several types of spirochatete. According to Dr. Simon Ridley, Director of Research at Alzheimer’s Research UK, “A large number of different microbes including viruses, bacteria, and fungi have been found in the brains of older people - but there do appear to be more of them in the brains of people who have died with Alzheimer’s disease.“ And Dr. Rudolph Tanzi, of Mass General Hospital, who is conducting research on bacteria and other microbes in the brain commented, “The Mount Sinai paper tells us the viral side of the story. We still have to work out the microbe side of the story. The brain was always thought to be a sterile place. It’s absolutely not true.”
Researchers emphasize that there’s no evidence indicating that Alzheimer’s is contagious, even if there is a viral component. They do, however, suggest that pharmaceutical research should be tweaked to consider the new findings. So far, most drugs have targeted the amyloid plaque, attempting to reduce or eliminate it, but these drugs have largely failed. Even when the drugs successfully reduce amyloid plaque, patients do not seem to reap improved brain function. Now some scientists believe that antiviral medications may be more effective, particularly for people in the early stages of Alzheimer’s. The National Institutes for Health has recently funded a study to see if antivirals can benefit people in the early stages of Alzheimer’s Disease.
While research continues, the best thing you can do towards prevention is to keep your immune system optimized, regularly supplement with natural antipathogens, and it still makes sense to slow down the build-up of amyloid plaque in the brain by supplementing with a carnosine-based formula.
- 1. Hamilton, Jon. “Researchers Find Herpes Virus in Brains Marked by Alzheimer’s Disease.” 21 June 2018. NPR. 9 July 2018. https://www.npr.org/sections/health-shots/2018/06/21/621908340/researchers-find-herpes-viruses-in-brains-marked-by-alzheimers-disease
- 2. Belluck, Pam. “A Common Virus May Play Role in Alzheimer’s Disease, Study Finds.” 21 June 2018. The New York Times. 9 July 2018. https://www.nytimes.com/2018/06/21/health/alzheimers-virus-herpes.html
- 3. Knapton, Sarah. “Alzheimer’s Disease could be caused by virus, experts warn.” 9 March 2016. The Telegraph. 9 July 2018. https://www.telegraph.co.uk/news/science/science-news/12188092/Alzheimers-disease-could-be-caused-by-herpes-virus-warn-experts.html
- 4. Neergaard, Lauran. “New evidence that viruses may play a role in Alzheimer’s. 21 June 2018. Associated Press. 9 July 2018. https://apnews.com/8e4ebccd8f09446d982eb63b85aafa9c