[The non-conventional transmissible agents at the origin of transmissible subacute spongiform encephalopathies]

The transmissible subacute spongiform human encephalopathies are neurological diseases, always fatal and with a prolonged incubation time. In infected patients, an accumulation of a host protein from the genes, the prion protein, is observed in proportionality to the infectious load. The prion protein gene is the major determinant of the genetic susceptibility in relation to subacute spongiform encephalopathies. On neuropathological examination, patients have a characteristic triad: neuronal vacuolisation, neuronal death and glial reaction. The nature of agents involved in these subacute spongiform encephalopathies is not known. Most authors think that the causal agent is a pathological form of the PrP protein partially resistant to proteinase K (the prion). For others, it is a more classical structure including an independent genome for which the prion protein will be either the receptor or the virulent factor. The apparition of bovine spongiform encephalopathy in the United Kingdom and of the new variant of Creutzfelt-Jakob disease brings into question the discovery of new subacute spongiform diseases and involves the proposition of efficacious protective measures for public and animal health.