New Evidence That Alzheimer’s Is Transmissible

Clues about causes for a mysterious disease

A post-mortem analysis of nearly 30 brains provides further support for a theory that Alzheimer’s might be transmissible, according to a study published this week in Swiss Medical Weekly and reported in Nature News.

The researchers looked at the brains of seven patients who had died of Creutzfeldt-Jakob disease (CJD), a rare degenerative brain disorder caused by infectious prions, small protein particles that are nearly indestructible. Decades before their deaths, the patients all received grafts of dura mater, a thick membrane that protects the spinal cord, taken from cadavers in order to treat a severe head injury or to repair the covering after surgery. The prions, it seems, were brought with the transplant, which likely caused CJD to develop over time.

But in five of the brains, the researchers saw evidence of Alzheimer’s disease as well—plaque-like buildups of a protein composite called beta amyloid slow the brain’s function, one of the defining characteristics of the condition. The patients had died between the ages of 28 and 63, generally too young to develop so much plaque buildup.

When the researchers compared these brains to those from patients that had died of CJD but hadn’t received the dura transplants, they found that the non-transplant patients didn’t have the beta amyloid plaques. Those findings indicate to the researchers that the seeds for the beta amyloid might have come with the graft, along with the prions that caused CJD in the first place, which might have caused Alzheimer’s to develop.

These findings are in line with a similar study published in Nature in September.

The researchers emphasize that the prions and plaques aren’t infectious, so CJD and Alzheimer’s couldn’t be transmitted under normal conditions. Even the dura grafts are no longer common practice because of the risk of developing CJD. But this and the previous study provide mounting evidence that Alzheimer’s can be transmitted through transplants. And though both studies have small sample sizes, the researchers believe these findings could help scientists better understand the underlying causes of Alzheimer’s, which could someday lead to improved treatments for the disease.