In the end it will be microbes—bacteria, viruses and fungus—found to be at the root of all disease and aging, and specifically Alzheimer’s, contends geneticist Dr. Rudolph “Rudy” Emile Tanzi.
“The two biggest threats to healthy aging have had to do with dealing with infection,” said Tanzi, who specializes in Alzheimer’s and the brain at Massachusetts General Hospital (MGH) and Harvard Medical School. “Think about it. When we increased the lifespan from 35 to 50, it was by covering the sewers. When we increased the lifespan from 50 to 75, it was with the use of antibiotics. Now we are looking for viruses in all of the major life-threatening diseases of our time—Alzheimer’s, cancer, Parkinson’s—and guess what? Infection is now cropping up in all of them.”
And though evidence continues to mount that could prove his theory, Tanzi says scientists are just beginning to scratch the surface of the culprits that can trigger the spiral into Alzheimer’s disease.
It’s one of the reasons scientists in Tanzi’s lab at MGH are mapping the microbiome of the brain—the population of microorganisms, some helpful and some pathological, that exists inside the brain—utilizing autopsied brain samples that tested positive for Alzheimer’s disease pathology. Researchers with The Brain Microbiome Project are looking for the most common germs found in the brain to attempt to determine which ones ultimately lead to Alzheimer’s disease. With the information, they hope to develop therapeutics for preventing and treating the disease that is projected to destroy the brains of nearly 14 million Americans by 2050.
Tanzi, Robert Moir and their team of Harvard researchers found more evidence this month to support the belief that microbes are indeed at the heart of Alzheimer’s disease. The team reported in the journal Neuron findings that suggest herpes viruses can set off the cascade of events that leads to Alzheimer’s disease.
In separate experiments, researchers studied how neurons in mice responded to the presence of herpes simplex 1 (HSV-1), the virus that causes cold sores and herpes virus 6 (HHV-6), the virus that causes the childhood skin disease roseola. (Most people catch these viruses early in life, and typically, they remain dormant. However, as we age, they almost always migrate up to the brain.)
In these experiments, scientists genetically bred some of the mice to have neurons that could create the human version of a protein called amyloid beta. Normally produced in the brain, amyloid beta is thought to be responsible for the plaques that eventually lead to Alzheimer’s.
Tanzi said, since 2010, his research has shown that:
- Amyloid beta protein is an antimicrobial peptide produced and used by the brain to protect itself against germs.
- But for unknown reasons amyloid beta protein is overproduced in Alzheimer’s sufferers and encourages the brain into engaging in processes that eventually lead to the disease.
- Neurons use amyloid beta to kill or trap (clump around) microbes to protect the brain.
