CX3CL1 and respiratory syncytial virus bronchiolitis: No significant differences were observed in the plasma levels of CCL1, CCL7, CCL8, CCL18, CCL19, CCL22, and CX3CL1 between the RSV bronchiolitis group and the control group, or between the mild and moderate-to-severe groups (P > 0.05) (Fig. 3).