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New laboratory research suggests that prions from chronic wasting disease in deer could infect people and create an entirely new kind of brain disorder.

The research is not proof that chronic wasting disease can infect people, but advances what science knows about that fear.

The researchers cautioned that the ability of chronic wasting disease prions to infect human brain tissue and cause disease could take years or decades of the disease first passing between deer in the wild, and might not occur at all.

"CWD is possibly the most worrisome prion zoonosis (animal disease that infects people) because it affects free-ranging animals, making it difficult to control its spread and because it is highly efficiently transmitted (among deer)," the researchers wrote. "Our results have far-reaching implications for human health."

The research, conducted by prominent scientists in the field of prion disease from four universities, was published last month in the Journal of Biological Chemistry.

It is the latest report in the field that came into prominence in the 1990s, when mad cow disease jumped the species barrier and began causing fatal brain illnesses in people in Great Britain.

Prions are infectious brain proteins that are believed to contain no DNA or other so-called living material. It is believed that they cause brain disease by converting normal prion protein in the brain to an abnormal, misfolded form, which, in turn, leads to the death of brain cells.

Chronic wasting disease, a related prion deer disorder, first was discovered in Wisconsin's wild deer population in 2002.

Since then there have been theoretical concerns about whether it, too, could jump the species barrier and infect humans, especially since so many people in Wisconsin eat venison. However, there has not been a documented case of that happening.

"It is clearly not proof, but it's suggestive," said Judd Aiken, a prion researcher at the University of Alberta. "It raises a warning flag."

One of the concerns is that the longer chronic wasting disease remains in Wisconsin, the more likely it is that prions are accumulating in soil, said Aiken, a professor of prion biology.

The more prions build up in the environment, the greater the chance that the disease will spread among deer.

"These agents can persist for many, many years, if not decades," Aiken said.

In addition, the longer the disease remains in the deer herd, the more likely it is that it will adapt, theoretically raising the potential that it might someday become infectious to humans or other animals such as cattle.

Indeed, the researchers of the new study used a test-tube process designed to mimic what occurs in the wild when one deer infects another deer. Only after doing that several times did they find that deer prions had the ability to convert normal human prion protein into infectious prion protein, at least in a test tube.

The process suggests that the more that happens in deer, the more likely it is that a strain of deer prion will develop that also can infect humans, said Claudio Soto, co-author of the study.

"The jury is still out on whether CWD can go into humans," said Soto, a professor of neurology at the University of Texas Houston Medical School. "The more CWD is in the wild, the more virulent it may be to humans."

Soto said the next step is to inject the prions that were developed in the lab into the brains of mice that have been genetically engineered to produce normal human prion protein.

If those mice develop a fatal brain disease, there will be more reason to be concerned that the deer disease may one day spread to people.

That experiment already has been started, Soto said, but it may take another year or two to know the results.