Location: Virus and Prion ResearchTitle: Use of an ELISA-based stability assay to examine host genotype, PrP**Sc stability, and incubation time relationships in U.S. livestock prion strains
Submitted to: Protein Society Symposium
Publication Type: Abstract Only
Publication Acceptance Date: 5/29/2012
Publication Date: 8/5/2012
Citation: Vrentas, C.E., Nicholson, E.M., Greenlee, J.J. 2012. Use of an ELISA stability assay to examine host genotype, PrPSc stability, and incubation time relationships in U.S. livestock prion strains. 26th Annual Symposium of The Protein Society. p. 211.
Technical Abstract: Transmissible spongiform encephalopathies (TSEs) are caused by the misfolding of the cellular prion protein (PrP**C) into a disease-associated version (PrP**Sc) that accumulates in certain tissues, leading to pathological changes in the brain and eventual death. Different strains of TSEs have been demonstrated to exist and cause different brain lesion and PrP**Sc accumulation profiles, as well as different incubation times, upon inoculation into a mouse host. Based on the "protein only" model for TSEs, the unique properties of each strain are "encoded" in PrP**Sc higher-order structure, even if the primary structure is the same in each case. One method of probing PrP**Sc structural differences is treatment with guanidinium chloride (GdmCl). When the level of PrP**Sc remaining is plotted as a function of [GdmCl], the [GdmCl]1/2, or the concentration at which half of the PrP**Sc has been denatured, is used as a measure of the stability of a strain. Previous work has demonstrated a tight correlation between the [GdmCl]1/2 of a strain and its incubation time in mice, with less stable PrP**Sc leading to shorter incubation times. Here, we employ a commercial ELISA-based assay to examine the stability of PrP**Sc from TSE-infected livestock, including scrapie-infected sheep and chronic wasting disease-infected elk. We retrospectively examine correlations between host genotype, incubation time, and PrP**Sc stability of strains in the U.S. livestock population. In sheep, we examine the impact of the host genotype at PRNP codon 136, a known scrapie susceptibility locus, on host susceptibility to different scrapie strains, including a fast-acting scrapie isolate called 136-VDEP. We observe a correlation between scrapie incubation time and PrP**Sc stability of the strains, and determine that the residue present at codon 136 does not inherently affect stability of PrP**Sc aggregates. We demonstrate the use of the stability assay as a means of tracking the presence of different scrapie strains through the process of stabilization in a livestock host. In elk, we observe correlations between the genotype at elk PRNP codon 132 (a known susceptibility locus, also important in human infection), CWD incubation time, and PrP**Sc stability. Finally, we compare the results of the stability measurements on elk PrP**Sc to structural differences probed by differences in the protease cleavage pattern of PrP**Sc and describe an effect of the method of brain tissue homogenization on these results.