Strain-specified characteristics of mouse synthetic prions

Synthetic prions were produced in our laboratory by using recombinant mouse prion protein (MoPrP) composed of residues 89-230. The first mouse synthetic prion strain (MoSP1) was inoculated into transgenic (Tg) 9949 mice expressing N-terminally truncated MoPrP(Delta23-88) and WT FVB mice expressing full-length MoPrP. On first and second passage in Tg9949 mice, MoSP1 prions caused disease in 516 +/- 27 and 258 +/- 25 days, respectively; numerous, large vacuoles were found in the brainstem and gray matter of the cerebellum. MoSP1 prions passaged in Tg9949 mice were inoculated into FVB mice; on first and second passage, the FVB mice exhibited incubation times of 154 +/- 4 and 130 +/- 3 days, respectively. In FVB mice, vacuolation was less intense but more widely distributed, with numerous lesions in the hippocampus and cerebellar white matter. This constellation of widespread neuropathologic changes was similar to that found in FVB mice inoculated with Rocky Mountain Laboratory (RML) prions, a strain derived from a sheep with scrapie. Conformational stability studies showed that the half-maximal GdnHCl (Gdn(1/2)) concentration for denaturation of MoSP1 prions passaged in Tg9949 mice was approximate to4.2 M; passage in FVB mice reduced the Gdn(1/2) value to approximate to1.7 M. RML prions passaged in either Tg9949 or FVB mice exhibited Gdn(1/2) values of approximate to1.8 M. The incubation times, neuropathological lesion profiles, and Gdn(1/2) values indicate that MoSP1 prions differ from RML and many other prion strains derived from sheep with scrapie and cattle with bovine spongiform encephalopathy.