Exploring PMCA as a potential in-vitro alternative method to mouse bioassays for the highly sensitive detection of BSE prions

Classical bovine spongiform encephalopathy (C-BSE) belongs to the transmissible spongiform encephalopathies (TSE), which are also designated prion diseases since they are caused by the conversion of the host-encoded cellular prion protein PrPC to its pathological isoform PrPTSE. BSE carries a zoonotic potential as BSE prions cause variant Creutzfeldt-Jakob disease in humans. To date, C-BSE infectivity can only be detected by bioassay, e.g. highly sensitive bovine PrP transgenic mice (e.g. Tgbov XV mice). Recently, highly sensitive in-vitro prion seeding activity assays, such as the Protein Misfolding Cyclic Amplification (PMCA), have been developed, which work particularly well for the template-assisted prion conversion of scrapie prions, while a similarly efficient bovine C-BSE-prion amplification remained unavailable. In the here described study, we have therefore compared the analytical sensitivities of the transgenic Tgbov XV mouse bioassay and our C-BSE PMCA protocol by analysing serial dilutions of a BSE-positive bovine brainstem homogenate pool. As both methods were shown to possess comparable sensitivities, we propose the C-BSE PMCA as a potential in-vitro replacement method, allowing the reduction and refinement of mouse bioassays for the detection of cattle derived classical BSE prions by reducing them to only specific analytical applications.