Scientists have developed a device that filters from blood the mutant proteins that cause the human form of mad cow disease. This new tool could boost the safety of donated blood.
Infectious proteins called prions cause mad cow disease, scrapie in sheep, and variant Creutzfeldt-Jakob disease (vCJD) in people. Since the early 1980s, doctors have diagnosed more than 200 cases of the fatal human disease worldwide, most of which seem to have resulted from eating beef tainted with prions. However, there's evidence that at least three people contracted the disease from blood transfusions that carried prions.
Scientists are working to reduce the risk of obtaining prions from beef. Researchers in the United States and Japan reported online Dec. 31, 2006 in Nature Biotechnology that they have engineered cattle that are free of the proteins that mutate to cause mad cow disease.
However, Robert Rohwer of the Veterans Affairs Medical Center in Baltimore, who studies vCJD and other prion-related diseases, notes that if these cattle enter the food supply, disease risk won't drop right away. Prions can linger in a person's blood from beef that they ate years ago.
"This is a disease with a very long incubation period during which people infected with vCJD appear completely normal," Rohwer says.
To develop a way to extract prions from blood, Rohwer and his colleagues …