Prion protein: detection in ‘spiked’ anaerobic sludge and degradation experiments under anaerobic conditions

Abstract

The behavior of the transmissible spongiform encephalopathies (TSE) causing agent denominated "prion protein" in anaerobic sludge (biogas reactor) was assessed with incubation tests. A widely applied screening method for BSE in cattle on the basis of the Western blotting protocol was adapted to detect the Proteinase K resistant, scrapie-form prion protein (PrPSC). As PrPsc source homogenized TSE infected brain tissue of animals late in the clinical phase of disease was taken (301V/VM mouse-BSE; bovine BSE and 22A/SV mouse-scrapie). The incubation under mesophilic conditions did not show any significant reduction of the PrPsc titer. Under thermophilic conditions contradictory results were obtained. The reduction time of PrPsc in water was equal to or longer than the PrPsc reduction time in anaerobic sludge. In comparison, with sterilized (121 degrees C, steam pressure) or poisoned (sodium azide, 1% w/v) sludge used as incubation matrix a much shorter time resulted until no prion protein could be detected.

Prion Stability and Infectivity in the Environment

“…In experimental studies, several prion strains have exhibited essentially no quantitative degradation when spiked in sludge under anaerobic (35°C) conditions and observed by a Western blot method during a 320 h observation period [85]. However, this method of detection would not work in the case of highly diluted, contaminated materials, such as would be expected in wastewater from slaughter houses or leachates from landfills.…”

Prions in the environment

“…84 Likewise, Kirchmayr et al found no significant decrease in PrP Sc after 16 days incubation in mesophilic anaerobic sludge and observed PrP Sc solids association. 80 PrP Sc degradation was observed in thermophilic anaerobic sludge, although maximum degradation occurred in sterilized samples. 80 Others found a large decrease in PrP Sc within 15 days after incubating BSE brain homogenates in municipal sewage at 20°C.…”

“…80 PrP Sc degradation was observed in thermophilic anaerobic sludge, although maximum degradation occurred in sterilized samples. 80 Others found a large decrease in PrP Sc within 15 days after incubating BSE brain homogenates in municipal sewage at 20°C. 82 Sheep scrapie brain homogenates were somewhat more resistant to degradation.…”

“…Differences between rodent PrP degradation and natural (sheep scrapie, BSE) PrP degradation were also seen in two other degradation studies. 80,82 Thus, caution should be taken when extrapolating rodent results to a natural prion system. Recently developed Tg mouse models expressing the elk, ovine, bovine or human prion protein (PrP c ) may be valuable research tools in studying the infectivity of environmental samples.…”

“…Recent studies simulating prion fate in wastewater found that PrP strongly partitioned into the sludge solids. 80,84 To date, only one study has directly evaluated the mobility of prions in soil. 75 In this study, recPrP was placed in a soil column and unsaturated pore water scrapie tissue, transgenic tissue might be used as PrP source material for environmental fate studies.…”