FIG. 4.
Replication in the nervous systems of 129 and IFN-α/βR−/− mice. Mice as described in the legend for Fig. 2 were sacrificed on day 6 postinfection. Brain, brainstem, and spinal cord tissues of 129 (A) and IFN-α/βR−/− (B) mice were disrupted by bead beating. Viral titers were determined by standard plaque assay. The dashed line indicates the limit of detection. *, P = 0.032 to 0.012; **, P < 0.0001 for 333d41 compared with 333d41R as determined by t test. n = 9 to 11 for 129 samples; n = 5 for IFN-α/βR−/− samples due to deaths of mice. For ΔTK−, n = 5.