[Prions, epidemic of Creutzfeldt-Jakob variant disease and global emergency].

We present here the current understanding of "prion" theory and global risk for epidemics of variant Creutzfeldt-Jakob disease (vCJD). Prion is the infectious agent of all transmissible spongiform encephalopaties (TSEs). It is regarded as an aggregate of a pathological conformer (PrPSc) of a normal cellular glycoprotein (PrPC) encoded by a gene, in humans on chromosome 20. The differences between PrPSc and PrPC are largely if not exclusively conformational; PrPC is mostly alpha-helical while PrPSc, beta-pleeted. Furthermore, mutations within the coding sequence (open reading frame) of PrP gene are linked with phenotypic expression of CJD, Gerstmann-Straussler-Scheinker disease (GSS) and fatal familial insomnia (FFI). VCJD is caused by transmission from cattle infected with bovine spongiform encephalopathy (BSE). PrP purified from vCJD-affected brains is characterised by the so called fourth type of glycosylation pattern. The neuropathological hallmark of vCJD is the florid plaque, an amyloid plaque surrounded by a corona of spongiform change. VCJD affects mostly young people (range: 13-74 years) and it is clinically distinguishable from sporadic CJD. The extent of epidemics is currently unknown; but its dynamic (102 cases until July 2001) may suggest "the worst" scenario.