Submitted to: Prion
Publication Type: Abstract Only
Publication Acceptance Date: 3/31/2015
Publication Date: 5/25/2015
Citation: Vrentas, C., Smith, J., Greenlee, J., Nicholson, E. 2015. Relationship of PrPSc molecular properties with incubation time in a natural prion disease host: a characterization of 3 isolates of US sheep scrapie. Prion 2015. p. S92.
Technical Abstract: Determination of aspects of tertiary and quaternary structure of PrPSc associated with differences in disease presentation in the host is a key area of interest in the prion field. Previously, we determined that a U.S. scrapie isolate (136-VDEP) with a short incubation time upon passage in sheep also exhibited low PrPSc stability in guanidine hydrochloride (GdnHCl), as compared to two isolates with longer incubation times and higher GdnHCl stability (136-A and 13-7). Here, we utilize this natural host system for a more in-depth examination of PrPSc biochemical properties. First, we recapitulated the incubation time findings from sheep in ovinized (VV136) transgenic mice via intracranial inoculation of 136-VDEP and 136-A. In contrast to published results in rodent strains, lower GdnHCl stability of 13-VDEP from sheep brain did not correlate with decreased stability of aggregates in the presence of SDS and heat. While the aggregate stability assay involves proteinase K (PK) treatment, the lack of correlation cannot be explained by a separate PK-sensitive population of PrPSc, since all three isolates exhibit similar PK sensitivity profiles, without a large fraction of PK-sensitive material. However, a time course of GdnHCl treatment suggests the presence of two distinct populations of PrPSc in the brain homogenates. Since oligomeric aggregates have been associated with higher infectivity, we examined PrPSc size distributions by sucrose gradient fractionation, but did not observe differences between isolates. We suggest that in this system, phenotypical differences may be due to tertiary structural, as opposed to quaternary structural, differences.