Biochemical evidence for the proteolytic degradation of infectious prion protein PrPsc in hamster brain homogenates by foodborne bacteria

PrPSc is a general term to describe the infectious agent causing transmissible spongiform encephalopathy (TSE), and the protease-resistant form of cellular PrPC. In this study, we have identified several protease-secreting bacteria able to degrade PrPSc under more or less native conditions (30 degrees C, pH 8), focusing on strains isolated mainly from cheese. One hundred and ninty-nine protease-secreting isolates belonging to the Actinomycetales and Bacillales were screened for the expression of PrPSc degrading activity by a Western blot procedure. Only 6 strains belonging to the following species were found to exhibit such an activity: Arthrobacter nicotianae, Bacillus licheniformis, Brachybacterium conglomeratum, Brachybacterium tyroferrmentans and Staphylococcus sciuri and Serratia spp. As revealed by a general protease assay based on dye-labeled Azocoll substrate, the PrPSc degrading activity was not directly correlated to the total level of secreted proteolytic activity of these organisms. This indicates that specific proteases are required for the degradation of PrPSc. Our study also suggests the potential use of such starter bacteria or their proteases for application in PrPSc degradation and decontamination under native conditions. (c) 2005 Elsevier GmbH. All rights reserved.