FIG. 3.
VSV in the brain following intranasal administration. Of the five mice receiving 5 × 107 PFU of VSV/FAST intranasally, two failed to develop hind-limb paralysis but continued to display clinical signs (piloerection, hunched posture, etc.). These mice were euthanized on day 21 postinfection, and the brains were subjected to histological and immunohistological analysis. Sections were either stained with hematoxylin and eosin or stained with a pan-VSV polyclonal antibody. Both VSV/FAST-infected mice had large zones of damaged and inflamed tissue. Mouse 2 displayed two zones of clear damage (red circles), one of which showed a few VSV-antigen positive cells (left panel). Mouse 3 displayed one zone of clear damage that showed occasional VSV-antigen positive cells (right panel, arrows). The VSV/GFP-infected mice were also examined, and a representative section is shown, demonstrating that this obvious damage is only caused by the VSV/FAST virus. VSV antigen was undetectable in this mouse (data not shown).