EV71 infection caused physiopathological changes and mortality of the suckling mice. (A) Seven-day-old ICR suckling mice were inoculated with the EV71 mouse-adapted strain MP4 (5 × 105 PFU/mouse). The expression of EV71 VP1 in the brain tissues of control and EV71-infected suckling mice at day 2 p.i. was detected by immunohistochemical staining using anti-VP1 antibody. Control (sham) group was given DMEM medium containing 2% FBS. Arrow indicates location of EV71 VP1. (B) Seven-day-old ICR suckling mice (n = 6, each group) were intracranially inoculated with the mouse-adapted strain of EV71, MP4 (5 × 105 pfu/mouse). The body weight, clinical symptoms, and survival rate were monitored daily after inoculation. Clinical score was defined as follows: 0: Healthy, 1: Ruffled hair/Hunchback appearance/Reduced mobility, 2: Wasting, 3: Forelimb or hindlimb weakness, 4: Forelimb or hindlimb paralysis, 5: Death. Values are the means ± standard deviation of the results of three independent experiments.