The shifting biology of prions

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are ra re fatal neurodegenerative diseases of humans and animals. Although some TS Es, like scrapie in sheep, have been known to exist for centuries, bovine s pongiform. encephalopathy (BSE) was recognized only 15 years ago. New varia nt Creutzfeldt-Jakob disease (nvCJD) of humans is probably caused by consum ption of BSE-infected materials. The nature of the infectious agent is not fully elucidated, but substantial evidence suggests that it is devoid of nu cleic acids and consists at least in part of an abnormal form of a host pro tein termed PrPC. Despite their rarity, prion diseases have become an impor tant topic in public health and basic research because of the connection be tween nvCJD and BSE and also because of the unusual biological attributes o f the infectious agent. (C) 2001 Elsevier Science B.V. All rights reserved.