A study from Harvard university has Dr. Doug Powell
wondering whether food-poisoning bacteria, such as salmonella, might be
responsible for Alzheimer’s disease.
The study found that the immune response to
infectious invaders is to trap them in a sticky cage of proteins.
After the fight, these cages of proteins are left
in the brain and are the plaque that’s “a hallmark of Alzheimer’s,” writes Gina
Kokata of the New York Times.
As people age, the membrane around the brain
becomes porous so infectious bacteria can get inside and then the immune
response kicks in. That explains why Alzheimer’s shows up in the brains of
older people.
So far, the research group has confirmed this
hypothesis in neurons growing in petri dishes as well as in yeast, roundworms,
fruit flies and mice.
There is much more work to be done to determine if
a similar sequence happens in humans, but plans — and funding — are in place to
start those studies, involving a multicenter project that will examine human
brains.
“It’s interesting and provocative,” said Dr.
Michael W. Weiner, a radiology professor at the University of California, San
Francisco, and a principal investigator of the Alzheimer’s Disease Neuroimaging
Initiative, a large national effort to track the progression of the disease and
look for biomarkers like blood proteins and brain imaging to signal the
disease’s presence.
The work began when Robert D. Moir, of Harvard
Medical School and Massachusetts General Hospital, had an idea about the
function of amyloid proteins, normal brain proteins whose role had long been a
mystery.
The proteins were traditionally thought to be
garbage that accumulates in the brain with age. But Dr. Moir noticed that they
looked a lot like proteins of the innate immune system, a primitive system that
is the body’s first line of defense against infections.
In one study, the group injected Salmonella bacteria
into the brains of young mice that did not have plaques.
