Immunohistochemistry and neuropathology of G131V-injected tg66 mice at 531 days post injection. In cerebral cortex: Linear axonal staining of PrPSc (arrow) was detected by antibody 3F4 (a). Vacuoles (arrow) shown by H&E staining (b) and microglia seen with anti-Iba1 staining (c) were also detected. In the Oriens layer of hippocampus of the same mouse shown in panels a, b, c, punctate 3F4 staining of PrPSc was detected in a pattern possibly indicating association with axonal cross-sections in this region (arrow) (d). As a negative control, in the same region of a mouse injected with Q227X brain homogenate no PrPSc deposits were observed at 529 dpi (e). The scale bar shown in panel a is 50 μm and applies to panels a-e