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Prusiner, Stanley Ben

prion disease protein cjd

(1942–) US biochemist: discoverer of prions, a new biological principle of infection.

Prusiner attended the medical school of the University of Pennsylvania, spent a year at the Wenner-Gren Institute in Stockholm and thereafter moved to the University of California at San Francisco. While Prusiner was working in the Department of Neurology a patient of his died from Creutzfeldt-Jakob disease (CJD). The disease, a dementia, produces no response from the body’s own defences, and very little was known other than that CJD, kuru and scrapie (a similar disease affecting sheep) could be transmitted through extracts of diseased brains. In 1972 Prusiner began to search for the causative infectious agent. Ten years later he and his colleagues obtained a preparation that contained a single infectious agent from the brains of diseased hamsters. Experimental evidence showed this to be a single protein. Prusiner named this protein a prion, an acronym derived from ‘proteinaceous infectious particle’. At this stage his work was regarded with some scepticism by the scientific community.

Even more strange, in 1984 Prusiner and his colleagues isolated a gene probe and showed that the prion gene was found naturally in all animals tested, including man. This raised the question whether the prion could be the causal agent of dementia-type disease, when the gene was a normal component of the body. It was discovered that the prion protein (designated PrP) could fold into two distinct conformations, one of which resulted in the disease (PrPSc). It was then shown that the disease-causing prion protein (PrPSc) had infective properties and could initiate a chain reaction in which normal (PrP) protein is converted into the PrPSc form. This PrPSc form was found to be stable and resistant to destruction by organic solvents and high temperatures (over 100° C). Incubation periods for the disease vary from months to years, during which time the disease-causing PrPSc can accumulate to levels resulting in brain damage. Since prions are present as natural proteins they do not induce an immune response. The long incubation time for the prion-based disease adds to the difficulty of isolating the prion protein. Prion diseases may be inherited, laterally transmitted, or occur apparently spontaneously. All known prion diseases are fatal.

Prusiner found that the hereditary forms of the prion diseases such as CJD are due to mutations in the prion gene. Structural prion variants accumulate in different regions of the brain producing different symptoms. Transmission of prion disease from one species to another varies and depends on structural closeness of prions from different species. The CJD epidemic was first detected in 1985, but due to the long incubation period did not peak until 1992. A new variant of CJD (nvCJD) may have arisen from BSE (bovine spongiform encephalopathy) transmitted by ingesting beef or beef products.

Prusiner’s work opened new methods of understanding dementia-type illnesses such as Alzheimer’s and established a theoretical basis for the treatment of prion diseases. His work added prions to the list of well-known infective agents: bacteria, viruses, fungi and parasites.

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