Figure 3. depletion of GM-CSF reduces the severity of CHIKV infection.

(A,B) Wild-type mice were infected with 1 × 10⁶ PFU of CHIKV in the right footpad and subsequently treated with anti-GM-CSF antibodies at 4 dpi. Joint-footpad swelling (A) and viral RNA load (B) were monitored over 14 days. Data were from biological replicates obtained from two independent experiments. All data are presented as mean ± SD. Data comparisons were performed with non-parametric Mann–Whitney U test (two-tailed). For footpad swelling: 5 dpi, **P = 0.0064; 6 dpi, **P = 0.0011; 7 dpi, **P = 0.0068; 8 dpi, *P = 0.0372. (C,D) Immunophenotyping of joint-footpad from anti-GM-CSF treated mice was performed at 6 days post-infection to determine the numbers of infiltrating CD4⁺ T cells and CD11b⁺Ly6C⁺ monocytes (C). Percentage differentiation of CD11b⁺Ly6C⁺ monocytes into CD64⁺MHCII⁺ macrophages in non-treated or GM-CSF-depleted CHIKV-infected animals is shown (D). Data were from biological replicates obtained from two independent experiments. All data are presented as mean ± SD. Data comparisons were performed with non-parametric Mann–Whitney U test (two-tailed). CD4⁺ T cells, *P = 0.037; CD11b⁺Ly6C⁺, *P = 0.0161. (E–I) In a separate set of experiment, CHIKV infection was performed and treated with anti-GM-CSF antibodies at 4 dpi. At 6 dpi, numbers of TNFα- (E), IFNγ- (F), Granzyme A- (G), Granzyme B- (H), and GM-CSF- (I) producing CD4⁺CD44⁺ T cells were in the joint-footpad were quantified following stimulation with ionomycin and phorbol myristate acetate (PMA). Data were from biological replicates obtained from two independent experiments. All data are presented as mean ± SD. Data comparisons between the groups were performed with non-parametric Mann–Whitney U test (two-tailed). TNFα-producing, *P = 0.0175; IFNγ-producing, *P = 0.0138, Granzyme A-producing, *P = 0.0176, Granzyme B-producing, *P = 0.0175, GMCSF-producing, *P = 0.0138. Source data are available online for this figure.