This animation gives a very simplified view of how prions cause fatal neurodegenerative diseases of the brain in man and animals

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1. The prion protein, PrP, is a normal constituent of many cell types in the body, notably nerve cells (neurons) in the brain. The name prion (pronounced pree-on) is derived from”proteinaceous infectious particle”. In its normal conformation, the prion protein (termed PrP^c) is innocuos. Its function in the body is still unknown. However, PrP^c can undergo a conformational change, adopting a harmful, disease-causing shape, termed PrP-scrapie, or PrP^Sc. Scrapie is a transmissible spongioform encephalopathy of sheep identified in Iceland already in the l8th century.

The conversion of the PrP^c-form to the PrP^Sc-form occurs at an extremely low frequency. The process may be compared to the transformation of Robert Louis Stevenson’s novel character Dr Jekyll to Mr Hyde – the same entity, but in two manifestations, a “kind” innocuous one, and a “vicious”, lethal one. PrP^Sc has unusual properties. It is stable to treatments at high temperatures ( 100°C), UV-light, and ionizing irradiation, enzymes that normally destroy proteins and nucleic acids, and some detergents. Such treatments would destroy all known viruses.