The N-terminal sequence of prion protein consists an epitope specific to the abnormal isoform of prion protein (PrP(Sc))

The conformation of abnormal prion protein (PrP(Sc)) differs from that of cellular prion protein (PrP(C)), but the precise characteristics of PrP(Sc) remain to be elucidated. To clarify the properties of native PrP(Sc), we attempted to generate novel PrP(Sc)-specific monoclonal antibodies (mAbs) by immunizing PrP-deficient mice with intact PrP(Sc) purified from bovine spongiform encephalopathy (BSE)-affected mice. The generated mAbs 6A12 and 8D5 selectivity precipitated PrP(Sc) from the brains of prion-affected mice, sheep, and cattle, but did not precipitate PrP(C) from the brains of healthy animals. In histopathological analysis, mAbs 6A12 and 8D5 strongly reacted with prion-affected mouse brains but not with unaffected mouse brains without antigen retrieval. Epitope analysis revealed that mAbs 8D5 and 6A12 recognized the PrP subregions between amino acids 31-39 and 41-47, respectively. This indicates that a PrP(Sc)-specific epitope exists in the N-terminal region of PrP(Sc), and mAbs 6A12 and 8D5 are powerful tools with which to detect native and intact PrP(Sc). We found that the ratio of proteinase K (PK)-sensitive PrP(Sc) to PK-resistant PrP(Sc) was constant throughout the disease time course.