Monday, January 1, 2007

SAN FRANCISCO (AP) — Scientists have genetically engineered a dozen cows to be free from the proteins that cause mad cow disease, a breakthrough that may make the animals immune to the brain-wasting disease.

A team of researchers from the U.S. and Japan reported Sunday that they had “knocked out” the gene responsible for making the proteins, called prions. The disease didn’t take hold when brain tissue from two of the genetically engineered cows was exposed to bad prions in the laboratory, they said.

Specialists said the work may offer another layer of security to people concerned about eating infected beef, although any food derived from genetically engineered animals must be approved by the Food and Drug Administration.

“This research is a huge step forward for the use of animal biotechnology that benefits consumers,” said Barbara Glenn of the Biotechnology Industry Organization, a Washington industry group that includes the company that sponsored the research. “This is a plus for consumers worldwide.”

The cows are being injected directly with mad cow disease, known as bovine spongiform encephalopathy, or BSE, to ensure the cattle are immune to it.

Those results won’t be known until later this year, at the earliest, according to the Sioux Falls, S.D.-based biotechnology company Hematech Inc., which sponsored the research. It can take as long as two years for mad cow disease to be detected in infected animals.

The research published in the online journal Nature Biotechnology could be used as a tool to help researchers better understand similar brain-wasting diseases in humans, Miss Glenn and others said.

Scientists remain mystified by the biological purposes of normal prions, which humans also produce. But they think that even one prion going bad can set off the always fatal and painful brain disease — known as variant Creutzfeldt-Jakob disease in humans.

Similar prion-based diseases are found in sheep, deer and elk.

Miss Glenn and others stressed that the mad cow threat to the United States is extremely low, in large part because of government regulations enacted after outbreaks in Europe.

“At the moment, we don’t have a high threat of BSE,” said Val Giddings, a scientist who consults with biotechnology companies. “But if BSE were ever to become a problem, this could turn out to be a good technological fix to it.”

Also, Hematech’s chief scientist, James M. Robl, said companies still are spending millions of dollars annually to protect their cows from the disease.

In the lab, Mr. Robl and his colleagues, including a scientist from the U.S. Department of Agriculture, scraped skin cells from cows and “turned off” the gene that makes prions. Scientists are certain the brain-wasting diseases are caused by the misshapen prions, one of the most mystifying particles in biology. The research published Sunday suggests the proteins have little value.

All the prion-free cows that the research team created were born healthy, although Mr. Robl noted that because they are only 2 years old, they will have to be watched to see whether the lack of prions has any health effects.

“It furthers the mystery of prions, for sure,” Mr. Robl said.

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