By Stanley B. Prusiner. At the time, the notion was heretical. Even viruses, among the simplest microbes, rely on such material to direct synthesis of the proteins needed for survival and replication. Such dual behavior was then unknown to medical science. Today, however, a wealth of experimental and clinical data has made a convincing case that we are correct on all three counts.
Prions are indeed responsible for transmissible and inherited disorders of protein conformation.
They can also cause sporadic disease, in which neither transmission between individuals nor inheritance is evident. Moreover, there are hints that the prions causing the diseases explored thus far may not be the only ones. Prions made of rather different proteins may contribute to other neurodegenerative diseases that are quite prevalent in humans. They might even participate in illnesses that attack muscles. The known prion diseases, all fatal, are sometimes referred to as spongiform encephalopathies.