FIGURE 4.
No prion infectivity is present as detected by animal bioassay. A, lysates from infected cells were intracerebrally inoculated into Tga20 mice, which were then monitored for signs of disease and culled at terminal stages of prion infection. Infected MoRK13 inoculated mice died after an average of 126 days (S.E. of 6 days). No other mice showed signs of prion disease, although one wild-type (wt) RK13 inoculated mouse died of an intercurrent illness at 266 days. B, histology of brain slices from MoPrP-RK13 inoculated mice displays prion pathology of spongiosis, astrocytosis, and plaque deposition. Mice inoculated with wild-type, G130L, G130P, and A119P lysate did not show any signs of pathology, although limited spongiform change and plaque deposition were observed in G125A-inoculated mice. α-GFAP, antibodies directed toward glial fibrillary acidic protein. C, brain homogenates from inoculated mice were treated with 100 μg/ml proteinase K. PrPSc was observed in MoPrP-inoculated mice but not in the brains of mice inoculated with GRR mutant cell lines.