Prion Diseases as Transmissible Zoonotic Diseases

Lee, Jeongmin; Kim, Su Yeon; Hwang, Kyu Jam; Ju, Young Ran; Woo, Hee-Jong

The word "prion", distinguished from virus or virion, was coined by Prusiner to refer to the scrapie pathogen in sheep; prion means a proteinaceous infectious particle [13] . PrP Sc , a scrapie form of a prion known to be pathogenic and misfolded, does not always induce clinical symptoms; therefore, the PrP Sc that induces clinical symptoms is marked as a disease prion: PrP d . However, prions already exist in animals and humans in the cellular form of the protein (PrP C ), which does not have any pathogenic properties. The primary amino acid sequences and the state of modification in both isoforms of PrP Sc and PrP C are identical; however, they have different three-dimensional structures, which give them distinct biochemical and biophysical properties. Also, alterations in amino acid sequences change the conformation of these proteins, resulting in a thermodynamically stable protein variant (PrP Sc ) that can cause diseases in both animals and humans [14] .