Fate of Prions in Soil:  Detergent Extraction of PrP from Soils

Abstract

The transmissible spongiform encephalopathies (TSEs) are caused by infectious agents whose structures have not been fully characterized but include abnormal forms of the host protein PrP, designated PrP(Sc), which are deposited in infected tissues. The transmission routes of scrapie and chronic wasting disease (CWD) seem to include environmental spread in their epidemiology, yet the fate of TSE agents in the environment is poorly understood. There are concerns that, for example, buried carcasses may remain a potential reservoir of infectivity for many years. Experimental determination of the environmental fate requires methods for assessing binding/elution of TSE infectivity, or its surrogate marker PrP(Sc), to and from materials with which it might interact. We report a method using Sarkosyl for the extraction of murine PrP(Sc), and its application to soils containing recombinant ovine PrP (recPrP). Elution properties suggest that PrP binds strongly to one or more soil components. Elution from a clay soil also required proteinase K digestion, suggesting that in the clay soil binding occurs via the N-terminal of PrP to a component that is absent from the sandy soils tested.

Pathogenic prion protein is degraded by a manganese oxide mineral found in soils

“…Prions can persist in soils for years (Seidel et al, 2007;Brown & Gajdusek, 1991) and binding of PrP TSE by soil particles may maintain prions near the soil surface, thereby increasing animal exposure (Johnson et al, 2006;Cooke et al, 2007;Ma et al, 2007). Soil particle-associated agents are infectious orally (Seidel et al, 2007;Johnson et al, 2007).…”

Potential role of soil properties in the spread of CWD in western Canada

“…Different minerals bind prions with different binding capacity, quartz < kaolinite < Mte-Ca < Mte-Na, 31 and mineral particle size specific surface area also change binding capacity. Cooke et al 27 have shown that soils with similar textures can exhibit remarkably different protein recoveries, and explained this discrepancy by a difference in mineralogy and/or soil pH. Our studies with infectious prions have shown that soils with different mineralogical composition can vary in prion binding capacities (Fig.…”

“…Different cations affect height of the interlayer space and proteins associated with the interlayer areas of expandable clays (e.g., smectites) potentially decreasing their bioavailability. 49 Cooke et al 27 found lower recovery of recPrP in the presence of soil cations, a finding related to the strong interactions between clay particles and exchangeable cations. Soil solution composition may, in addition to pH, change the binding capacity of prions to whole soils.…”

“…[14][15][16]19,[26][27][28] Prions have a strong affinity for clay minerals commonly found in soil; PrP Sc binds clay minerals (montmorillonite, Mte) avidly in comparison with quartz sand, an interaction that considerably enhances prion infectivity.…”

Prions in the environment

“…The N-domain has been shown to affect PrP aggregation, 92 and evidence suggests the N-domain might play a role in sorption to soils. 68,70,73,74,76 Therefore, both full-length and truncated prions should be used to study environmental fate.…”