Severity of disease postinfection. Mice were scored in masked fashion daily after infection according to the following scale: 0, no signs; 1, slight erythema and edema; 2, prominent erythema and edema; 3, presence of lesions; and 4, hind limb paralysis. Data from three experiments were pooled. Values represent the mean scores ± standard errors of the means for 24 mice per group. ∗, P ≤ 0.039; ∗∗, P ≤ 0.017.