Cows engineered to lack mad cow disease

Then, using those cells as a "starter kit," they produced 12 calves through cloning processes — the fusing of the cells into the eggs of cows. Three were slaughtered so their brains could be studied and nine are still living.

"The cloning process itself is very large scale," said Robl, who estimated that Hematech implants about 15,000 cloned embryos into 4,000 cows annually. Most of the pregnancies are terminated before birth to collect cells for the company's research in developing human medicines, he said.

Robl said a more immediate use of the technology could be to produce prion-free cows to produce cow serum, a popular laboratory tool used for myriad biological experiments.

Since three cows in the United States were diagnosed with BSE beginning in December 2003, most labs order their cow serum from New Zealand.

But Hematech isn't much interested in producing serum for scientists and has no plans to become a beef producer.

Instead, the company is genetically engineering cows to produce antibiotics and other medicines for people.

The company embarked on the mad cow disease project five years ago to ensure it could produce medicines that were free from the brain-wasting disease. BSE is caused when one misshapen prion prompts normal prions to turn bad, slowly boring lesions in the brain and making infected animals go mad.

It's thought that people eating infected beef can contract the human variant of the disease, which also occurs spontaneously.

At least 180 people worldwide have died after eating meat infected with mad cow disease in the last two decades. Symptoms can take years to develop.

But scientists are certain the brain-wasting diseases are caused by the misshapen prions, one of the most mystifying particles in biology. No one knows the function of normal prions and the research published Sunday suggests the proteins have little value.

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

"It furthers the mystery of prions, for sure," Robl said.

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