Detection of bovine spongiform encephalopathy-specific PrPSc by treatment with heat and guanidine thiocyanate

The conversion of a ubiquitous cellular protein (PrPC), an isoform of the p rion protein (PrP), to the pathology-associated isoform PrPSc is one of the hallmarks of transmissible spongiform encephalopathies such as bovine spon giform encephalopathy (BSE), Accumulation of PrPSc has been used to diagnos e BSE, Here we describe a quantitative enzyme-linked immunosorbent assay (E LISA) that involves antibodies against epitopes within the protease-resista nt core of the PrP molecule to measure the amount of PrP in brain tissues f rom animals with BSE and normal controls. In native tissue preparations, li ttle difference was found between the two groups. However, following treatm ent of the tissue with heat and guanidine thiocyanate (Gh treatment), the E LISA discriminated BSE-specific PrPSc from PrPC in bovine brain homogenates . PrPSc was identified by Western blot, centrifugation, and protease digest ion experiments. It was thought that folding or complexing of PrPSc is most probably reversed by the Gh treatment, making hidden antigenic sites acces sible. The digestion experiments also showed that protease-resistant PrP in BSE is more difficult to detect than that in hamster scrapie. While the co ncentration of PrPC in cattle is similar to that in hamsters, PrPSc sparse in comparison. The detection of PrPSc by a simple physicochemical treatment without the need for protease digestion, as described in this study, could be applied to develop a diagnostic assay to screen large numbers of sample s.