Science Recreates Mad Cow Disease

Scientists have produced a prion protein that can trigger the development of a neurological disorder in mice that is similar to “mad cow” disease, according to a new study supported by the National Institute on Aging (NIA), a part of the National Institutes of Health. The findings demonstrate that prions, an unusual class of infectious proteins, can make copies of themselves without the presence of viral DNA or RNA, damage brain tissue, and cause neurological diseases. The work by Nobel Laureate Stanley B. Prusiner, M.D., and colleagues at the University of California, San Francisco, and Heinrich-Heine Universitat in Germany, appears in the July 30, 2004, issue of Science. For the study, Dr. Prusiner and his colleagues produced prion protein fragments in bacteria, folded them into larger protein structures called amyloid fibrils, and then injected them into the brains of susceptible mice. The mice began exhibiting symptoms of disease in their central nervous systems between 380 and 660 days after they were given the synthetic prion proteins. The amyloid form of the prion protein, which is thought to cause prion disease, was also found in the brains of the diseased mice. The researchers then administered brain extracts from these animals to another group of mice, which subsequently developed similar symptoms 90 to 150 days later. The disorder seems to be distinct from that caused by other known strains of prions, suggesting that the synthetic prion didn’t merely activate a pre-existing prion in these mice and that the synthesized prion protein itself is sufficient to make infectious and disease-causing prions.

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