The recent "mad cow disease" scare has pushed a little known but highly controversial protein into the limelight: the prion (pronounced pree-on), a malfolded and infectious version of a normal cellular protein.
Prions are the suspected culprits behind a number of rare and fatal diseases, including mad cow disease (or bovine spongiform encephalopathy), scrapies, Creutzfeldt-Jakob disease, and kuru. But so far no one has definitively linked prions to these diseases or even proven they exist. A special news report by Rosie Mestel in this issue of Science draws on interviews with 24 researchers on all sides of the issue and takes a detailed look at the evidence for and against prions. Do they represent an entirely new disease process or are they, as some scientists are saying, the "cold fusion" of infectious disease research?