Conformational stability and molecular profiles after passage to an ovinized mouse model support emergence of x124 strain after passage of No. 13–7 strain through white-tailed deer.

A) Unfolding curves of were generated from the brains of Tg338 (ovine VRQ PRNP) that were inoculated with x124 scrapie from sheep, WTD scrapie after passage through sheep (sheep #2, sheep #6), and the original 13–7 scrapie inoculum. Curves generated from PrP^Sc from the brains of mice inoculated with x124 or WTD scrapie passaged through sheep were similar with a [GdnHCl]_1/2 near 1.8 M, whereas the original scrapie inoculum was significantly more stable with a [GdnHCl]_1/2 of 3.1 M. B) Western blots of these isolates in Tg338 mice demonstrate a slightly higher apparent molecular mass of the x124 and WTD scrapie isolates than that of the original No. 13–7 inoculum (mAb SHA31). When these tissues are probed with the N-terminal antibody 12B2, binding is present in brain homogenates from mice inoculated with x124 or WTD scrapie passaged through sheep, but not with the No. 13–7 isolate. WTDsc, WTD scrapie agent. Labels in magenta, orange and black indicate brains were used for both western and dot blot assays. [GdnHCl]_1/2, half-maximal denaturation concentration of PrP^Sc. Fapp: fraction of apparent PrP^Sc. ****, p< 0.0001, ns, not statistically significant. Error bars, mean ±SD of data from three mice per group, each mouse brain was analyzed in triplicate.