FTY720 treatment increases clinical disease severity, mortality and affects viral clearance from the CNS. (A) S1P1 eGFP knock-in mice C57BL/6 were infected i.c. with JHMV (150 PFU) and treated daily beginning at day 5 p.i. (shaded area) with either FTY720 (1, 3 and 10 mg/kg, n = 10 per group) or vehicle control by i.p. injection. Infected mice showed increased clinical disease severity at all FTY720 concentrations used with 10 mg/ml (*P < 0.05) having the greatest effect compared to vehicle-treated control mice. Data are presented as average ± standard error of the mean (SEM) and represent a minimum of two independent experiments with a minimum of five mice/group. (B) FTY720 treatment (beginning at day 5 p.i., shaded area) results in a dose-dependent increase in mortality compared to vehicle-treated mice. Data are representative of two independent experiments with a minimum of five mice/experimental group. Viral titers within the brain (C) and spinal cord (D) in JHMV-infected mice treated with either FTY720 (3 mg/kg) or vehicle (beginning at day 5 p.i.) were determined at days 7, 14 and 21 p.i. Data points represent individual mice and bars indicate averages. CNS viral titers represent two independent experiments. *P <0.05.