FIGURE 4.

Representative decontamination treatment evaluation experiments showing examples of a non-efficient, partially efficient and completely efficient treatment for prion decontamination. Electrophoresis and total protein staining of the Proteinase K (PK)-digested PMSA products of three representative experiments are shown as examples of decontamination treatment evaluation by PMSA. Three replicates (R1, R2, and R3) of either 1 or 5 prion-coated zirconia-silica (Zr-Si) beads treated by autoclaving at 121°C for 20 min and submitted to a PMSA round at three time points (t1, t2, and t3), serve as an example of a non-effective inactivation treatment, since rec-PrP^res with the characteristic ∼16 kDa predominant band could be detected in all replicates at t2 and t3. Samples at t1 were negative which, being a time point chosen as a control of the process, indicates that the propagation kinetics were as expected. Positive control samples (Control), performed with untreated prion-coated beads of the same type at t1 and t3 demonstrate that the PMSA allowed propagation as expected, and negative controls (Neg C.), performed using non-coated beads of the same time show there was no cross contamination or spontaneous generation during the process. A sample of substrate, not digested with PK, was also included to facilitate size comparisons. As an example of a partially effective treatment, the experiment performed using Teflon^® beads treated with 1N NaOH for 1 h is shown. Finally, an example of a completely effective inactivation, the experiment carried out with prion-coated steel beads treated with commercial bleach for 1 h is shown. MW, Molecular weight marker.