Rapid detection of creutzfeldt-jakob disease and scrapie prion proteins

Creutzfeldt-Jakob disease (CJD) and Gerstmann-Straussler syndrome (GSS) of humans as well as scrapie of animals are caused by prions. The scrapie prion protein isoform (PrP^Sc) is the only macromolecule identified to date which is a component of the infectious prion particle. PrP^Sc is converted to PrP 27-30 by limited proteolysis while the cellular isoform, designated PrP^C, is completely digested under the same conditions. ELISA studies demonstrated that native PrP 27-30 bound to plastic surfaces resisted proteolysis and exhibited little or no immunoreactivity but after denaturation with guanidinium thiocyanate (GdnSCN), immunoreactivity was greatly enhanced. PrP^Sc bound to nitrocellulose also exhibited enhanced immunoreactivity after denaturation. PrP^Sc was readily detected in brain extracts from scrapie-infected hamsters, mice, and sheep by dot-blot immunoassays using limited proteolysis followed by GdnSCN denaturation. The high sensitivity and specificity of the immunoassay allowed detection of regional differences in PrP^Sc in sheep brain. CJD prion protein isoform (PrP^CJD) was also detected in the brains of all 10 patients tested with neuropathologically confirmed CJD and in 1 patient with GSS. Enhanced immunoreactivity of PrP^Sc or PrP^CJD after denaturation cannot only be used for immunodiagnosis of prion diseases but may also form the basis of new assays in experimental studies directed at the chemical structure of the prion particle.