Transmissible spongiform encephalopathies (TSEs), such as bovine spongiform encephalopathy (BSE) in cattle, scrapie in sheep, and Creutzfeldt-Jakob disease (CJD) in humans, are all fatal neurological disorders resulting from the deposition of a misfolded form of the prion protein (designated PrPSc) in the central nervous system. Accumulation of PrPSc can also be found in other tissues the organism. Of greatest concern to public health is the potential presence of the aberrant form of PrPSc in muscle tissue of infected cattle. Recently PrPSc studies on experimentally infected rodents showed that PrPSc was present in the muscle tissue. To assess the relative risk associated with this finding, Michael Beekes and colleagues, from the Robert Koch-Institut, investigated the time course of PrPSc accumulation in the muscle tissue of infected rodents both and find the defective form of the prion protein is present prior to clinical symptoms. The accumulation of PrPSc is seen close to the onset of symptoms but is greatest after clinical symptoms are well established. Deposition appears to occur through the spinal motor neurons into the myofibers of the muscle tissue. This animal model provides an excellent source for investigation of the timing and mechanisms for PrPSc spread in an infected animal, but should not be extrapolated to an indication that cattle with BSE likewise will have PrPSc build-up in muscle tissue prior to clinical symptoms as this rodent model has much higher levels of infectivity and PrPSc production than do other non-experimental produced TSEs.
TITLE: Preclinical deposition of pathological prion protein PrPSc in muscles of hamsters orally exposed to scrapie
Robert Koch-Institut, Berlin, Germany.
Phone: +49 30-4547-2396; Fax: +49-30-4547-2267; E-mail: BeekesM@rki.de
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