Fig. 1.

Timing of T cell recruitment to lungs affects disease timing in RSV. 6-7 weeks old BALB/c SPF mice were intranasally infected 7.7 x 10⁶ PFU/ml RSV A2 subtype and culled on day 1, 3, 5, and 7 post infection. Body weight (A) and food consumed (B) were monitored daily. Immune cell populations were measured using flow cytometry (C) at each time course, and live viral plaques (D) and RSV L gene (E) were quantified. 6-7 weeks old BALB/c SPF mice were injected with 25µg of FTY720 or PBS only daily from day -2 to day 6. Mice were intranasally infected with 7.7 x 10⁶ PFU/ml RSV infection on day 0. Body weight (F) and food (G) were monitored daily from day -2 to day 14. At day 7, viral load was determined using RSV L gene qPCR on RNA extracted from the left lung lobe (H) and flow cytometry was used to analyze the number of CD8 T cell (I), CD4 T cells (J) and antigen-specific CD8⁺ T cells (K). At day 14, viral load was determined using RSV L gene qPCR (L) and flow cytometry was used to analyze the number of CD8 T cell (M), CD4 T cells (N) and antigen-specific CD8 T cells (O). N = 5, each dot represents an individual mouse (H-O); or mean +/-SEM –A - E, F-G). Significance calculated by ordinary one-way ANOVA and post test. *P  ≤  0.05, **P  ≤  0.01, ***P  ≤  0.001. Experiment was repeated twice.