Rapid and sensitive determination of residual prion infectivity from prion-decontaminated surfaces.

Prion diseases are untreatable fatal transmissible neurodegenerative diseases that affect a wide range of mammals, including humans, and are caused by PrPSc, the infectious self-templating conformation of the host-encoded protein, PrPC. Prion diseases can be transmitted via surfaces (e.g., forceps, EEG electrodes) in laboratory and clinical settings. Here, we use a combination of surface swabbing and real-time quaking-induced conversion (RT-QuIC) to test for residual surface-associated prions following prion disinfection. We found that treatment of several prion-contaminated laboratory and clinically relevant surfaces with either water or 70% EtOH resulted in robust detection of surface-associated prions. In contrast, treatment of surfaces with sodium hypochlorite resulted in a failure to detect surface-associated prions. RT-QuIC analysis of prion-contaminated stainless steel wires paralleled the findings of the surface swab studies. Importantly, animal bioassay and RT-QuIC analysis of the same swab extracts are in agreement. We report on conditions that may interfere with the assay that need to be taken into consideration before using this technique. Overall, this method can be used to survey laboratory and clinical surfaces for prion infectivity following prion decontamination protocols.IMPORTANCEPrion diseases can be accidentally transmitted in clinical and occupational settings. While effective means of prion decontamination exist, methods for determining the effectiveness are only beginning to be described. Here, we analyze surface swab extracts using real-time quaking-induced conversion (RT-QuIC) to test for residual prions following prion disinfection of relevant clinical and laboratory surfaces. We found that this method can rapidly determine the efficacy of surface prion decontamination. Importantly, examination of surface extracts with RT-QuIC and animal bioassay produced similar findings, suggesting that this method can accurately assess the reduction in prion titer. We identified surface contaminants that interfere with the assay, which may be found in clinical and laboratory settings. Overall, this method can enhance clinical and laboratory prion safety measures.

Strain-Specific Targeting and Destruction of Cells by Prions.

Prion diseases are caused by the disease-specific self-templating infectious conformation of the host-encoded prion protein, PrPSc. Prion strains are operationally defined as a heritable phenotype of disease under controlled conditions. One of the hallmark phenotypes of prion strain diversity is tropism within and between tissues. A defining feature of prion strains is the regional distribution of PrPSc in the CNS. Additionally, in both natural and experimental prion disease, stark differences in the tropism of prions in secondary lymphoreticular system tissues occur. The mechanism underlying prion tropism is unknown; however, several possible hypotheses have been proposed. Clinical target areas are prion strain-specific populations of neurons within the CNS that are susceptible to neurodegeneration following the replication of prions past a toxic threshold. Alternatively, the switch from a replicative to toxic form of PrPSc may drive prion tropism. The normal form of the prion protein, PrPC, is required for prion formation. More recent evidence suggests that it can mediate prion and prion-like disease neurodegeneration. In vitro systems for prion formation have indicated that cellular cofactors contribute to prion formation. Since these cofactors can be strain specific, this has led to the hypothesis that the distribution of prion formation cofactors can influence prion tropism. Overall, there is evidence to support several mechanisms of prion strain tropism; however, a unified theory has yet to emerge.