What is known – and unknown – about prions
• Prions are responsible for a number of diseases classified as transmissible spongiform encephalopathy diseases (TSEs), including bovine spongiform encephalopathy (BSE or mad cow disease), scrapie (in sheep), Creutzfeldt-Jakob disease (CJD), Chronic Wasting Disease, Fatal Familial Insomnia, Gerstmann-Sträussler-Scheinker syndrome, and kuru (found in members of the cannibalistic Foré tribe in Papua New Guinea). These diseases affect the brain tissue and are fatal and untreatable.
• The precise mechanism of prion infection is still a mystery. Most known pathogens (bacteria, viruses, etc.) contain nucleic acids which are necessary for reproduction and can be broken down by ultraviolet radiation. However, prions were found to resist ultraviolet radiation yet respond to agents that disrupt proteins. The observation that prions can reproduce without nucleic acids goes against conventional scientific thinking. However, all evidence suggests that prions can alter biological properties without changing their amino acid sequence and can transfer a pathological conformation. • CJD is the most common form of human prion disease. It comprises a group of disorders including sporadic CJD and variant CJD (vCJD), which has been linked to BSE. All forms of CJD are progressive neurological disorders which are fatal and for which there is, as yet, no cure. In the UK there are between 50 and 65 deaths each year from sporadic CJD. To date there have been more than 150 deaths from vCJD. • In vCJD the prion is widely distributed throughout the body, in addition to the central nervous system, raising concerns that the agent may be transmitted by contaminated surgical instruments used on lymphoid tissues – for example, the spleen or tonsils – and possibly by blood transfusion. CJD has occasionally been transmitted by contaminated neurosurgical instruments, tissue grafts, including corneal and dura mater grafts, and contaminated human pituitary hormones.
