Transport of the Pathogenic Prion Protein through Landfill Materials

Abstract

Transmissible spongiform encephalopathies (TSEs, prion diseases) are a class of fatal neurodegenerative diseases affecting a variety of mammalian species including humans. A misfolded form of the prion protein (PrP TSE ) is the major, if not sole, component of the infectious agent. Recent TSE outbreaks in domesticated and wild animal populations has created the need for safe and effective disposal of large quantities of potentially infected materials. Here, we report the results of a study to evaluate the potential for transport of PrP TSE derived from carcasses and associated wastes in a municipal solid waste (MSW) landfill. Column experiments were conducted to evaluate PrP TSE transport in quartz sand, two fine-textured burial soils currently used in landfill practice, a green waste residual material (a potential burial material), and fresh and aged MSW. PrP TSE was retained by quartz sand and the fine-textured burial soils, with no detectable PrP TSE eluted over more than 40 pore volumes. In contrast, PrP TSE was more mobile in MSW and green waste residual. Transport parameters were estimated from the experimental data and used to model PrP TSE migration in a MSW landfill. To the extent that the PrP TSE used mimics that released from decomposing carcasses, burial of CWD-infected materials at MSW landfills could provide secure containment of PrP TSE provided reasonable burial strategies (e.g., encasement in soil) are used.

Prion transmission

“…Various studies have demonstrated the binding and persistence of PrP Sc to soil and soil minerals. [93][94][95][96][97] Importantly, rodent-adapted scrapie remains infectious in bioassays when bound to soil minerals 93 and surprisingly, soilimmobilized prions have enhanced infectivity via the oral route compared to unbound prions. 94 Together, data suggest that soil is likely to be an important environmental reservoir of prion infectivity; however, it should be noted that to date no studies have demonstrated the presence of PrP Sc or prion infectivity in naturally contaminated soils.…”

Humic substances interfere with detection of pathogenic prion protein

“…Laboratory studies designed to examine prion adsorption to and persistence in soils typically rely on extraction of PrP TSE from soil particles followed by immunodetection (e.g., immunoblotting, enzyme-linked immunosorbent assay) as the primary means of measurement (Cooke et al, 2007;Huang et al, 2007;Jacobson et al, 2009Jacobson et al, , 2010Johnson et al, 2006;Leita et al, 2006;Ma et al, 2007;Maddison et al, 2010;Russo et al, 2009;Seidel et al, 2007). To date, effective elution of PrP TSE from soil particles has been accomplished only with anionic detergents such as sodium dodecyl sulfate (SDS) or sodium N-lauroylsarconsinate (sarkosyl) (Cooke et al, 2007;Johnson et al, 2006;Seidel et al, 2007).…”

Temperature influences the interaction of ruminant PrPTSEwith soil

“…Previous studies have indicated that prions bind rapidly, and largely irreversibly to soils, do not migrate through soil columns and can persist for years. 20,22,23 Furthermore, the interaction of prions with soil does not remove infectivity. 24,25 This interaction of prions with soil is influenced not only by the soil type but also by the prion source.…”