Possible cell-free prion replication.

Abstract

Spongiform encephalopathies, such as scrapie or bovine spongiform encephalopathy in animals, or kuru, Creutzfeld-Jakob disease (CJD) and Gerstmann-Sträussler-Scheinker disease (GSS) in man, seem to be caused by a transmissible agent whose nature is still a matter of debate. The properties of this agent which has been designated as prion, differ from those of any other known infectious agents, including viruses and viroids. Several lines of evidence suggest that the prion is devoid of nucleic acid and is identical with a modified form of a normal host protein. This lack of nucleic acid poses the question of how a protein moiety can propagate itself as a transmissible agent. Here it is proposed that prion replication is a process similar to crystallization and as such, the propagation of prions can take place as a sort of chain-reaction in an in vitro cell-free system.