Abstract

Prions are lethal pathogens causing neurodegenerative diseases in humans and other animals. They appear devoid of nucleic acid and composed of polymerised conformational isomers of host-encoded cellular prion protein. Their unique biology, allied with the risks to public health posed by prion zoonoses such as BSE , has focussed much attention on understanding the molecular basis of prion propagation and the “species barrier” which controls cross-species transmission. Both are intimately linked to understanding how multiple prion “strains” are encoded by a protein-only agent, a challenging question in molecular biology which raises intriguing questions in evolution. It is increasingly clear that the underlying mechanisms, involving aggregation of a misfolded host protein, are of much wider relevance in commoner neurodegenerative diseases. Recent advances suggest that prions themselves may not be directly neurotoxic, but rather their propagation leads to production of toxic species which may be uncoupled from infectivity. A general protein-only model, developed to encompass prion strains and toxicity, may be of wider significance. Effective treatments for prion infection have been established and clinical trials are now being planned. In addition, emerging evidence suggests that the cellular prion protein may have a direct role in mediating aspects of neurotoxicity in Alzheimer’s disease which may allow common therapeutic approaches.