Discovery of Prions

American neurologist Stanley Prusiner announced in 1982 that he had identified the infectious agent behind scrapie and related brain-wasting diseases as a misfolded protein capable of causing normal copies of the same protein to misfold in turn, with no genetic material of its own, and coined the word prion, short for proteinaceous infectious particle, to describe it, though the protein itself was not fully isolated until two years later. Prusiner's protein-only theory of infection was highly controversial at the time, since every previously known infectious agent, from bacteria to viruses, relied on DNA or RNA to reproduce, but it built on an earlier hypothesis the British scientist John Stanley Griffith proposed in the 1960s, that an infectious agent made entirely of protein was theoretically possible. Continued research eventually validated Prusiner's theory and connected prions to a family of fatal neurodegenerative diseases including Creutzfeldt-Jakob disease in humans and bovine spongiform encephalopathy, popularly known as mad cow disease, and Prusiner received the 1997 Nobel Prize in Physiology or Medicine for the discovery.