Pathogenicity of LA51IT WNV in a mouse model.
Six-week-old female C57BL/6JJmsSlc mice were inoculated with 100 pfu of WT or LA51IT WNV intraperitoneally (a and b) or intracranially (c–e). (a) The Kaplan–Meier survival curves of the mice inoculated with WT or LA51IT WNV. *p < 0.05. (b) The brain, spleen, and serum were collected at 3, 5, or 7 days post infection (dpi) (n = 3), and the viral titers were measured. (c) Cerebral cortical and hippocampal hematoxylin and eosin-stained sections, or sections immunostained for WNV antigen or ubiquitin, from mice inoculated with WNV WT (n = 4) or LA51IT (n = 4). White arrowheads indicate degenerated neuronal cells. Black arrowheads indicate ubiquitin-positive cells. Scale bar: 20 μm. Scale bar: 20 μm. (d) Number of degenerated cells in the CA2 and CA3 hippocampal neuronal layers was counted. Data represent the means ± standard error of four independent experiments. Statistical significance was assessed using a two-tailed Student’s t-test. *p < 0.05. (e) Ubiquitin accumulation in the brain. Sections of cerebral cortex or hippocampus of the mice inoculated with WNV WT or LA51IT were stained with antibodies against ubiquitin (red) and WNV antigen (green). Nuclei were stained with DAPI. White arrowheads indicate ubiquitin-positive cells. Scale bar: 5 μm. The number of ubiquitin-positive cells per E protein-positive cells was calculated. Data represent the means ± standard error of four independent experiments. Statistical significance was assessed using a two-tailed Student’s t-test. **p < 0.01.