Transmissible Spongiform Encephalopathies

Abstract

Prion diseases, also termed transmissible spongiform encephalopathies (TSEs), are inevitably fatal neurodegenerative conditions which affect humans and a wide variety of animals. The most common form of prion disease in humans is sporadic Creutzfeldt-Jakob disease (sCJD). Human studies also point to a possible role for members of the classical complement cascade in prion pathogenesis; however, their precise role in prion disease is unknown. The majority of cases were caused by implantation of dura mater and injection of pituitary growth hormone. There is uncertainty surrounding the danger of transmission to humans represented by chronic wasting disease. In fact, even transmissibility of bovine spongiform encephalopathy (BSE) to humans relies on circumstantial evidence. Recent advances in neuroimaging, and especially in magnetic resonance imaging (MRI), have revealed that different human prion diseases have specific patterns. Tissue should be fixed in formalin for histologic assessment and snap-frozen for Western blotting. Western blotting of digested PrPSc reveals three distinct bands, corresponding to di-, mono-, and unglycosylated forms. Depending on the exact conditions under which the protease digestion and the Western blotting procedure are performed, between three and six different PrPSc types can be distinguished. The fact that the PrPSc types found in variant CJD (vCJD) patients and in BSE-diseased cattle are identical is one of the main arguments supporting the theory that BSE prions are responsible for the vCJD epidemic in humans.