Effects of different experimental conditions on the PrP^Sc core generated by protease digestion: Implications for strain typing and molecular classification of CJD

The discovery of molecular subtypes of the pathological prion protein PrP^Sc has provided the basis for a novel classification of human transmissible spongiform encephalopathies (TSEs) and a potentially powerful method for strain typing. However, there is still a significant disparity regarding the understanding and nomenclature of PrP^Sc types. In. addition, it is still unknown whether a specific PrP^Sc type is associated with each TSE phenotypic variant. In sporadic Creutzfeldt-Jakob disease (sCJD), five disease phenotypes are known, but only two major types of PrP^Sc, types 1 and 2, have been consistently reproduced. We further analyzed PrP^Sc properties in sCJD and variant CJD using a high resolution gel electrophoresis system and varying experimental conditions. We found that pH varies among CJD brain homogenates in standard buffers, thereby influencing the characteristics of protease-treated PrP_Sc. We also show that PrP^Sc type 1 and type 2 are heterogeneous species which can be further distinguished into five molecular subtypes that fit the current histopathological classification of sCJD variants. Our results shed light on previous disparities in PrP^Sc typing, provide a refined classification of human PrP^Sc types, and support the notion that the pathological TSE phenotype is related to PrP^Sc structure.