A team of American and Japanese scientists has created cows that lack the protein responsible for mad cow disease according to a report in the January 2007 issue of Nature Biotechnology. A thorough clinical examination of the animals up to the age of 20 months indicates that they are healthy, and laboratory tests of their brain tissue suggests that they are likely to be resistant to mad cow disease, which can be transmitted to humans through consumption of affected beef.
Mad cow disease (or bovine spongiform encephalopathy) is caused by a misfolded form of a particular protein known as a 'prion' protein. Kuroiwa and colleagues genetically engineered cows that are identical to ordinary cows except that they lack the prion protein. Because scientists don't understand the function of this protein in its correctly folded form, it was unclear whether prion-free cows would be healthy. The authors' comprehensive health assessment put this concern to rest, at least for young animals.
Studies to determine whether prion-free cows are resistant to mad cow disease take many years and are currently underway. However, preliminary laboratory tests showed that the animals' brain tissue blocks the spread of misfolded prion protein, unlike the brain tissue of ordinary cows.
Yoshimi Kuroiwa (Kirin Brewery Co, Tokyo, Japan and Gemini Science Inc, La Jolla, CA, USA)
James Robl (Hematech, Inc, Sioux Falls, SD, USA)
Juergen Richt (National Animal Disease Center, USDA, Ames, IA, USA)
Abstract available online.
(C) Nature Biotechnology press release.
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