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Story available at http://www.billingsgazette.net/articles/2006/07/07/news/state/65-mad-cow.txt

Published on Friday, July 07, 2006.
Last modified on 7/7/2006 at 12:08 am

By JENNIFER McKEE
Gazette State Bureau

HELENA -- Montana scientists have discovered that brain-wasting killers such as mad cow disease can also affect the hearts of its victims, infusing heart muscle with waxy deposits making it harder for infected hearts to beat.

In a paper published today in the online edition of the journal Science, researchers at Montana's Rocky Mountain Laboratories in Hamilton showed that special laboratory mice infected with scrapie, a brain-wasting disease in sheep, also had large deposits of the scrapie agent in their hearts.

Scrapie is one of a family of brain-wasting diseases -- including chronic wasting disease in deer and elk, mad cow disease in cattle and Creutzfeldt-Jacob disease in people -- associated with twisted, malformed proteins called prions.

The prions congregate in the brains of victims and are associated with Swiss-cheeselike holes in brain tissue that are always fatal.

What causes the diseases, known as transmissible spongiform encephalopathies, is unclear, although one hypothesis is that the proteins themselves cause infection.

RML's Bruce Chesebro, a virologist and lead author of the paper, said the discovery is the first time prion proteins have been shown to cause heart problems and will probably prompt other researchers to start looking at the heart in future prion research.

"We don't have a clue as to why this deposited in the heart, as opposed to the liver," he said. "We don't really understand that."

The study involved special mice. Prions are misshapen proteins. That same protein when it's not twisted is common in the body, although researchers aren't exactly what role healthy prion proteins play.

Scientists engineered the mice in Chesebro's experiment to have a different kind of healthy prion protein. That way, when the mice were inoculated with an infectious brain-wasting disease, such as scrapie, the resulting prions would behave in a certain way.

Chesebro said that at this point, it's not clear whether the deposits of prion in the hearts of the mice are related to their unique makeup, or whether it's common in many victims of prion diseases, but no one ever thought to look.

"We have no evidence in this paper that prions can invade human hearts, but we're interested in investigating those questions," he said.

The prion deposits formed a kind of waxy, protein plaque called amyloids.

Alzheimer's disease is also an amyloid disease because it is associated with waxy, protein plaques in the brain.

Amyloid heart disease is also found in people, although it is rare.

Anthony Fauci, head of the National Institutes of Allergy and Infectious Diseases, the arm of the National Institutes of Health that oversees RML, noted that connection with prion heart disease.

"Although much work remains to be done, the diseased hearts seen in this mouse study have similarities to human amyloid heart disease, which is potentially significant," Fauci said in a statement.

The Montana scientists conducted the experiment with researchers at The Scripps Research Institute in California.


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