Abstract: The cellular prion protein PrPC has been extensively studied because it can adopt a pathogenic three-dimensional conformation that causes rare, but invariably fatal, neurodegenerative prion diseases in humans and other mammals. The disease-causing conformer of the protein is called PrPSc, of which oligomeric aggregates constitute prion agents that can bind to, and convert further, PrPC molecules into PrPSc (Prusiner, 1998). Thus, in the poorly understood process of prion propagation, there is transfer of biological information encoded solely by protein conformation. Prions can spread within a tissue secondary to a spontaneous conversion of PrPC to PrPSc or upon transmission of prion agents between individuals.