CAPILLARY ELECTROPHORESIS OF THE SCRAPIE PRION PROTEIN FROM SHEEP BRAIN

Scrapie in sheep and goats causes a progressive, degenerative disease of the central nervous system and is the prototype of other transmissi ble spongiform encephalopathies (TSE) found in humans and in animals. In samples of TSE-affected brains, unique rod-shaped structures are fo und acid are infectious. These rods are composed of a protease-resista nt, post-translationally modified cellular protein (PrPsc)? that has a molecular mass of ca. 27 000 on sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Laboratory tests used for the diagnosis of scrap ie detect PrPsc. The overall concentration of PrPsc in tissues is low. The present methods to diagnose scrapie are lengthy, require relative ly large quantities of starting material to detect PrPsc and lack sens itivity. We explored the use of free zone capillary electrophoresis an d immunocomplex formation to detect PrPsc in the brain tissue of infec ted sheep. Brain tissue from both infected (as confirmed by histologic al and biological tests) and from normal animals was used to prepare t he PrPsc. After treatment with proteinase K and non-ionic detergents, PrPsc was solubilized and reacted with a rabbit antiserum specific for a peptide of the prion protein. Immunocomplex formation was observed for the samples from scrapie-infected brain but not for samples from n ormal brain. When a fluorescein-labeled goat anti-rabbit immunoglobuli n was used as a second antibody, the detection of immunocomplex format ion was enhanced both by the immunological technique and by using lase r-induced fluorescence for detection. This same rabbit antiserum was u sed on immunoblot analysis. Three bands were observed for material fro m an infected sheep but none in preparations from brain material from normal sheep. Capillary electrophoresis can be used to show immunocomp lex formation when PrPsc is present in sheep brain.