Adsorption of Pathogenic Prion Protein to Quartz Sand

Abstract

Management responses to prion diseases of cattle, deer, and elk create a significant need for safe and effective disposal of infected carcasses and other materials. Furthermore, soil may contribute to the horizontal transmission of sheep scrapie and cervid chronic wasting disease by serving as an environmental reservoir for the infectious agent. As an initial step toward understanding prion mobility in porous materials such as soil and landfilled waste, the influence of pH and ionic strength (I) on pathogenic prion protein (PrP Sc ) properties (viz. aggregation state and ζ-potential) and adsorption to quartz sand was investigated. The apparent average isoelectric point of PrP Sc aggregates was 4.6. PrP Sc aggregate size was largest between pH 4 and 6, and increased with increasing I at pH 7. Adsorption to quartz sand was maximal near the apparent isoelectric point of PrP Sc aggregates and decreased as pH either declined or increased. PrP Sc adsorption increased as suspension I increased, and reached an apparent plateau at I ∼ 0.1 M. While trends with pH and I in PrP Sc attachment to quartz surfaces were consistent with predictions based on Born-DLVO theory, non-DLVO forces appeared to contribute to adsorption at pH 7 and 9 (I ) 10 mM). Our findings suggest that disposal strategies that elevate pH (e.g., burial in lime or fly ash), may increase PrP Sc mobility. Similarly, PrP Sc mobility may increase as a landfill ages, due to increases in pH and decreases in I of the leachate.

Influence of landscape factors and management decisions on spatial and temporal patterns of the transmission of chronic wasting disease in white-tailed deer

“…Prions bind strongly to various types of soil and resist removal by water or various solvents (Leita et al, 2006;Saunders et al, 2008) so though possibly long-lasting, there is little subsequent migration or leaching through the soil (Jacobson et al, 2010;Maddison et al, 2010). Prions may interact with various components of soil including clay, sand and organic components (Ma et al, 2007;Maddison et al, 2010;Saunders et al, 2010). In vitro and laboratory assays have indicated that prions bound to clays may have greater infectivity (Johnson et al, 2006) while field studies by Walter et al (2011) showed an association between CWD in mule deer and a higher percentage of clay soils within the deer's home range.…”

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).…”

“…Protein attachment to negatively charged surfaces is often maximal at the isoelectric point (pI) of the protein and declines when pH.pI due to repellent electrostatic interactions (Quiquampoix et al, 2002). The apparent average pI of PrP TSE aggregates is~4.6 (Ma et al, 2007); prion protein aggregates carried no net charge around this pH value. In most models of degradation of organic molecules by MnO 2 , sorption to the oxide surface represents a critical initial step (Stone, 1987).…”

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

“…[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.…”