Neurotoxicity but not infectivity of prion proteins can be induced reversibly in vitro

Prion diseases include Creutzfeldt-Jakob disease in humans, scrapie in sheep and bovine spongiform encephalopathy. The hallmark of prion diseases is the accumulation of an abnormal isoform (PrP(Sc)) of the cellular prion protein accompanied by neuronal cell death and astroglial proliferation. To characterize the correlation between PrP secondary and quarternary structure and their biological effects we assayed soluble and aggregated forms of PrP 27-30, the N-terminal truncated form of PrP(Sc), as well as the corresponding recombinant PrP(90-231) for their neurotoxicity and infectivity. PrP was kept soluble in 0.2% SDS and subsequently re-aggregated either by diluting the SDS or by adding acetonitril. The neurotoxicity of the re-aggregated states were comparable to that of prion rods (PrP 27-30) whereas the soluble forms had no neurotoxic effects. The solubilized PrP 27-30 showed no significant infection upon re-aggregation as determined by bioassays in Syrian golden hamsters. The recombinant PrP did not exhibit infectivity in any state.