Inflammatory Cytokines Resolve Chikungunya Disease www.plosntds.org CXCL10, CXCL9 and IgG levels are possible biomarkers of CHIKV disease severity IL-1b, IL-6 and RANTES were found to be associated with symptom severity of the Singapore 2007 CHIKV outbreak [22] . After determining the cytokine profiles of our Italian 2007 CHIKV patients during their disease resolution, we next sought to determine the association between symptom severity and cytokine levels. Patients were determined to be non-symptomatic (N), to have mild symptoms (M) or to have severe symptoms (S) depending on their responses to a questionnaire. The cytokine levels were then grouped by symptom level and a Mann-Whitney U test was used to determine significance among the severity groups for each cytokine. CXCL10 and CXCL9 were found to be significantly increased in the patients with mild and severe symptoms at 6 months following initial infection compared to the patients reporting no symptoms ( Figure 6A) . A 2 fold difference was seen between the medians of the non-symptomatic and severe patients for CXCL10 and a 5 fold difference for CXCL9. No statistical difference was seen for any of the 13 cytokines profiled for the 12-month follow-up. CXCL10 and CXCL9 at 12 months are shown for comparison ( Figure 6B ). Moreover, we analyzed the IgG levels at the 6-month follow-up in patients with no symptoms, mild symptoms, and severe symptoms. The results showed IgG levels were statistically increased with Figure 1 . Acute phase CHIKV disease was associated with high levels of IL-6, CXCL9, CCL2, CXCL10. Cytokine Bead Array analysis of CHIKV patient serum samples showed high levels of IL-6, CXCL9, CCL2 and CXCL-10 are associated with acute disease phase and decreased with patient convalescence. Six-month and one-year cytokine levels were analysed for statistical significance using the Wilcoxon test for Significance by comparing with acute levels. All samples were also analyzed for significance against healthy controls by the Mann-Whitney U test. The cross symbol indicates a p-value less than 0.05 for 6-and 12-month groups compared to acute values and star symbol indicates a p-value less than 0.05 for acute, 6-and 12-month groups compared to control values. The dotted line indicates the median of healthy control cytokine levels. Acute (A), 6-month follow-up (6), and 12-month follow-up (12 Figure 6C ). Taken together, these results suggested CXCL10, CXCL9 and IgG to be possible markers of CHIKV severity during early phases of disease resolution.