Proteinaceous infectious particle

Prusiner S. B. Novel proteinaceous infectious particles cause scrapie. Science 216 136-144,1982. 

A, Proteinaceous Infectious Particle Without Genome Is Causative Agent... 

Prions (small proteinaceous infectious particles) are a unique class of infectious agent causing spongiform encephalopathies such as bovine spongiform encephalopathy (BSE) in cattle and Creutzfeldt-Jakob disease (CJD) in humans. There is considerable concern about the transmission of these agents from infected animals or patients. Risk of infec-tivity is highest in brain, spinal cord and eye tissues. There are still many unknown factors regarding de-... 

Like other neurodegenerative disorders, such as Alzheimer s and Parkinson s disease, prion diseases are characterized by the formation and accumulation of an aberrantly folded protein in the brain. However, a unique feature of prion diseases is their transmissibility. Prions (acronym for proteinaceous infectious particles) are mainly composed of PrPSc, polysaccharides, and lipids, but lack nucleic acids longer than 25 nucleotides, arguing against an essential role for DNA/RNA in mediating infectivity [35, 36]. Indeed, recent experiments support the protein-only hypothesis recombinant PrP expressed in and purified from bacteria and subsequently misfolded in vitro can transmit the disease [37-40]. 

Prions are now thought to be what were formerly called slow viruses, because the resulting diseases took months or years or decades to develop (Voet and Voet, 1995, p. 1116). These particular diseases pertain to the mammalian nervous systan. None of the diseases exhibit inflammation or fever, indicating that the immune system is neither activated nor impaired by the disease. As has been indicated, the word prion stands for proteinaceous infectious particle, and the protein itself is called PrP, for prion protein. 

A prion - short for proteinaceous infectious particle - is a unique type of infectious agent. Prions are composed of abnormal isoforms of a normal host-encoded membrane protein, termed prion protein (Prl ). Abnormally folded prion protein catalyses the refolding of normal prions into abnormal forms. Prions are not considered life. However, their biological origin and their potential effect on animals and human beings warrant a brief discussion. 

In his 1998 review following his Nobel Prize, Prusiner mentions that he "never imagined the irate reaction of some scientists to the word prion." Perhaps the most striking feature of the prion story is that in fact, the "proteinaceous" infectious particle is made of a unique protein species of 27-30 kDa, later designated PrP (for prion protein) by Prusiner. ... 

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