PrP(c) mRNA, but not PrP(Sc) is found in the salivary glands of scrapie-infected sheep

Transmission studies in transmissible spongiform encephalopathies (TSEs) have become increasingly important due to the possible transmission of bovine spongiform encephalopathy to humans resulting in new variant Creutzfeldt-Jacob disease. The horizontal transmission of scrapie, a TSE of sheep, is poorly understood. Possible sources of horizontal transmission are the submandibular and parotid salivary glands. TSEs like natural sheep scrapie are characterized by the conversion of a normal protease sensitive prion protein, PrP(c), to an abnormal protease resistant prion protein, PrP(Sc). Since the presence of PrP(Sc) is an indicator of disease, the salivary glands of scrapie-infected sheep were examined for the presence of PrP(Sc). Although PrP(c) mRNA was detected in the salivary glands, PrP(Sc) was not found in the salivary glands of scrapie-infected sheep. These data suggest that the salivary glands are unlikely sources of horizontal transmission of natural sheep scrapie.