FIG. 1.

V3533 induces mild, transient disease followed by clearance in C57BL/6 mice. (A) Female C57BL/6 mice (7 to 10 weeks old) were inoculated with 10⁶ PFU of V3533 by injection in the left rear footpad. At the indicated days postinfection (Day P.I.), serum, spleen, brain, and spinal cord samples were collected from V3533-infected mice and homogenized. The amount of infectious virus present in serum, spleen, brain, and spinal cord samples was then quantified by plaque assays of BHK-21 cells. Data are presented as the means ± standard deviations of results pooled from two independent experiments with 3 to 10 animals per time point. Dotted lines represent the limit of detection. (B) Female C57BL/6 mice (7 to 10 weeks old) were inoculated with 10³ PFU of wild-type VEEV (V3000) or 10⁶ PFU of V3533 by injection in the left rear footpad. Mock-infected mice were infected with diluent alone. Mice were weighed daily, with those losing more than 20% of their starting weight being euthanized as required by UNC IACUC regulations. *, P < 0.05 by Mann-Whitney testing.