by Bret Stetka © 2018
Infectious Theory Draws Fresh Interest Alzheimer’s Disease – Dr Leslie Norins is willing to hand over $1 million of his own money to anyone who can clarify something: is Alzheimer’s disease, the most common form of dementia worldwide, caused by a germ? By “germ” he means microbes like bacteria, viruses, fungi and parasites. In other words, Norins, a physician turned publisher, wants to know if Alzheimer’s is infectious.
It’s an idea that just a few years ago would’ve seemed to many an easy way to drain your research budget on bunk science. Money has poured into Alzheimer’s research for years, but until very recently not much of it went toward investigating infection in causing dementia. But this “germ theory” of Alzheimer’s, as Norins calls it, has been fermenting in the literature for decades. Even early 20th century Czech physician Oskar Fischer—who, along with his German contemporary Dr Alois Alzheimer, was integral in first describing the condition—noted a possible connection between the newly identified dementia and tuberculosis.
If the germ theory gets traction, even in some Alzheimer’s patients, it could trigger a seismic shift in how doctors understand and treat the disease. Norins received his medical degree from Duke in the early 1960s, and after a stint at the Centers for Disease Control and Prevention he fell into a lucrative career in medical publishing. He eventually settled in an aged community in Naples, Florida, where he took an interest in dementia and began reading up on the condition.
After scouring the medical literature he noticed a pattern. “It appeared that many of the reported characteristics of Alzheimer’s disease were compatible with an infectious process,” Norins tells NPR. “I thought for sure this must have already been investigated, because millions and millions of dollars have been spent on Alzheimer’s research.” But aside from scattered interest through the decades, this wasn’t the case.
In 2017, Norins launched Alzheimer’s Germ Quest Inc., a public benefit corporation he hopes will drive interest into the germ theory of Alzheimer’s, and through which his prize will be distributed. A white paper he penned for the site reads: “From a two-year review of the scientific
literature, I believe it’s now clear that just one germ—identity not yet specified, and possibly not yet discovered—causes most AD. I’m calling it the ‘Alzheimer’s Germ’.” Norins is quick to cite sources and studies supporting his claim, among them a 2010 study published in the
Journal of Neurosurgery showing that neurosurgeons die from Alzheimer’s at nearly two-and-a-half times the rate of the general population.
Another study from that same year, published in The Journal of the American Geriatric Society, found that people whose spouses have dementia are at a 1.6 times greater risk for the condition themselves. Contagion does come to mind. And Norins isn’t alone in his thinking. In 2016, 32 researchers from universities around the world signed an editorial in the Journal of Alzheimer’s Disease calling for “further research on the role of infectious agents in [Alzheimer’s] causation.” Based on much of the same evidence Norins encountered, the authors concluded that clinical trials with antimicrobial drugs in Alzheimer’s are now justified.
NPR reported on an intriguing study published in Neuron in June that suggested that viral infection can influence the progression of Alzheimer’s. Led by Mount Sinai genetics professor Joel Dudley, the work was intended to compare the genomes of healthy brain tissue with that affected by dementia. But something kept getting in the way—herpes. Herpes Dudley’s team noticed an unexpectedly high level of viral DNA from two human herpes viruses, HHV-6 and HHV-7. The viruses are common and cause a rash called roseola in young children (not the sexually transmitted disease caused by other strains).
Some viruses have the ability to lie dormant in our neurons for decades by incorporating their genomes into our own. The classic example is chickenpox: A childhood viral infection resolves and lurks silently, returning years later as shingles, an excruciating rash. Like it or not, nearly all of us are chimeras with viral DNA speckling our genomes. But having the herpes viruses alone doesn’t mean inevitable brain decline. After all, up to 75 per cent of us may harbor HHV-6.
The hallmark pathology of Alzheimer’s is accumulation of a protein called amyloid in the brain. Many researchers have assumed these aggregates, or plaques, are simply a byproduct of some other process at the core of the disease. Other scientists posit that the protein itself contributes to the condition in some way. The theory that amyloid is the root cause of Alzheimer’s is losing steam. But the protein may still contribute to the disease, even if it winds up being deemed infectious.
Work by Harvard neuroscientist Rudolph Tanzi suggests it might be a bit of both. Along with colleague Robert Moir, Tanzi has shown that amyloid is lethal to viruses and bacteria in the test tube, and also in mice. He now believes the protein is part of our ancient immune system that like antibodies, ramps up its activity to help fend off unwanted bugs. So does that mean that the microbe is the cause of Alzheimer’s, and amyloid a harmless reaction to it? According to Tanzi it’s not that simple. Tanzi believes that in many cases of Alzheimer’s, microbes are probably the initial seed that sets off a toxic tumble of molecular dominoes. Early in the disease amyloid protein builds up to fight infection, yet too much of the protein begins to impair function of neurons in the brain. The excess amyloid then causes another protein, called tau, to form tangles, which further harm brain cells.
But as Tanzi explains, the ultimate neurological insult in Alzheimer’s is the body’s reaction to this neurotoxic mess. All the excess protein revs up the immune system, causing inflammation—and it’s this inflammation that does the most damage to the Alzheimer’s-afflicted brain.
Bret Stetka is a writer based in New York and an editorial director at Medscape. His work has appeared in Wired, Scientific American and on TheAtlantic.com. (Source: NPR.org, 9 September 2018; http://tinyurl.com/y8luzmrd)
Another study… found that people whose spouses have dementia are at a 1.6 times greater risk for the condition themselves.
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