Differences in Proteinase K Resistance and Neuronal Deposition of Abnormal Prion Proteins Characterize Bovine Spongiform Encephalopathy (BSE) and Scrapie Strains

Abstract

Prion diseases are associated with the accumulation of an abnormal isoform of host-encoded prion protein (PrP(Sc)). A number of prion strains can be distinguished by "glycotyping" analysis of the respective deposited PrP(Sc) compound. In this study, the long-term proteinase K resistance, the molecular mass, and the localization of PrP(Sc) deposits derived from conventional and transgenic mice inoculated with 11 different BSE and scrapie strains or isolates were examined. Differences were found in the long-term proteinase K resistance (50 microg/ml at 37 degrees C) of PrP(Sc). For example, scrapie strain Chandler or PrP(Sc) derived from field BSE isolates were destroyed after 6 hr of exposure, whereas PrP(Sc) of strains 87V and ME7 and of the Hessen1 isolate were extremely resistant to proteolytic cleavage. Nonglycosylated, proteinase K-treated PrP(Sc) of BSE isolates and of scrapie strain 87V exhibited a 1-2 kD lower molecular mass than PrP(Sc) derived from all other scrapie strains and isolates. With the exception of strain 87V, PrP(Sc) was generally deposited in the cerebrum, cerebellum, and brain stem of different mouse lines at comparable levels. Long-term proteinase resistance, molecular mass, and the analysis of PrP(Sc) deposition therefore provide useful criteria in discriminating prion strains and isolates (e.g., BSE and 87V) that are otherwise indistinguishable by the PrP(Sc) "glycotyping" technique.