Expanding spectrum of prion diseases

Prions were initially discovered in studies of scrapie, a transmissible neurodegenerative disease (ND) of sheep and goats thought to be caused by slow viruses. Once scrapie was transmitted to rodents, it was discovered that the scrapie pathogen resisted inactivation by procedures that modify nucleic acids. Eventually, this novel pathogen proved to be a protein of 209 amino acids, which is encoded by a chromosomal gene. After the absence of a...