Could Alzheimer’s be an autoimmune disease?

2022-09-28

Searching for an Alzheimer’s cure is among the world’s most pressing needs. Researchers in Canada have a new theory.

Alzheimer’s is a degenerative brain disease with no cure and no effective therapeutic treatments to stop or slow its progression. It impacts an estimated 50 million people around the world, and for those afflicted, invariably results in dementia and death.

In Australia Alzheimer’s affects up to 1 in 10 Australians over 65 years of age, and up to 3 in 10 over 85. It is not a normal part of ageing.

One prevailing theory suggests that a sticky protein called beta-amyloid builds up in the brain forming clumps known as plaques, which then acts to kill brain cells, directly causing Alzheimer’s disease. However, 30 years of research into the development of medical treatments designed to target these plaques have led to failure after failure.

Now, scientists at the Krembil Brain Institute, which is part of the University Health Network in Ontario, Canada suggest that new thinking around the disease is desperately needed.

They are asking: “Could Alzheimer’s be an autoimmune disease?”

“Yes,” says Dr. Donald Weaver, co-Director of the Krembil Brain Institute and author of new research published in the peer-reviewed journal, Alzheimer’s & Dementia. “We don’t think of Alzheimer’s as fundamentally a disease of the brain. We think of it as a disease of the immune system within the brain.”

The role of beta-amyloid in the brain is as an ‘immunopeptide’ – a messenger within the immune system which is involved in repairing the brain. “If we have head trauma, beta-amyloid repairs it. If a virus or a bacteria comes along, beta-amyloid is there to fight it,” explains Weaver.

But unfortunately, beta-amyloid can become confused.

“Beta-amyloid gets confused and can’t tell the difference between a bacteria and a brain cell,” says Weaver. “And so, it inadvertently attacks our own brain cells. This, then, becomes what we call an autoimmune disease.”

To test these ideas, the team surveyed the disease and patient literature to develop a detailed model describing the cause and effect relationship of Alzheimer’s disease (known as a mechanistic model).

This approach allowed them to step back and take a more holistic review of the workings of the disease at several different levels within the biological system — such as Alzheimer’s progression and effect on different sections of the brain’s nerve cells, and the larger immune disease response — and also to consider novel causes and inputs into the disease.

Tangible rethinking about Alzheimer’s disease as an autoimmune disease, and beta-amyloid as a normal part of our immune system, opens the door to new avenues and approaches to develop innovative new therapies, says Dr. Weaver, who hopes that this new conceptual framework could eventually present a new way to combat this insidious and devastating disease.

Cosmos, 28 September 2022
; https://cosmosmagazine.com