PrPSc of scrapie 263K propagates efficiently in spleen and muscle tissues with protein misfolding cyclic amplification

Transmissible spongiform encephalopathies (TSEs), or prion diseases, are transmissible neurodegenerative disorders of protein conformation. This group of diseases is caused by infectious agents, termed prions, which can convert normal conformation (PrPC) into misfolded protein (PrPSc). The infectivity of non-neuronal tissues has been wildly addressed, but the propagating features and the biochemical properties of prion generated from these tissues are only partially settled. In this study, utilizing protein misfolding cyclic amplification (PMCA), the in vitro conversion of PrPC into PrPSc in spleen and muscle tissues can be induced by PrPSc produced in vivo. The further propagation of newly formed PrPSc in normal brain and some of the biochemical properties of new PrPSc are similar as the brain-derived prions, implying the naturally infectious pathway of prion from peripheral generation to neuro-invasion. However, compared with the brain-derived PrPSc, the weaker resistance of new PrPSc to some inactivated agents, i.e. sodium hydroxide and thermal inactivation, are observed. Our data provide the reliable evidence that the brain-derived PrPSc can utilize the PrPC from non-neuronal tissues for its propagation. Similarity of the replicative ability in PMCA in vitro and the infectivity in vivo highlights the possibility to use PMCA instead of bioassay to investigate the propagation of prion.