Fig. 4: Sialokinin treatment reduces joint footpad inflammation in CHIKV-infected mice.

a C57BL/6 WT 4-week-old mice were infected with 1 × 10⁶ pfu of CHIKV subcutaneously at the joint footpad. Mice were treated with 1 mg/kg of sialokinin or PBS (control) via intraperitoneal injection from days 2 to 7 post-infection (dpi). Created in BioRender. Ng, L. (2025) https://BioRender.com/fj6toz3. b Circulating CD11b⁺Ly6G⁺ neutrophils and CD11b⁺ Ly6C⁺CD169⁺ monocytes were quantified by flow cytometry. Data are presented as mean ± SD (n = 5 per group). Statistical comparisons used unpaired two-tailed t-test. c Joint swelling was monitored to 14 dpi. Viremia was assessed from tail vein blood (1 to 10 dpi) via qRT-PCR targeting CHIKV nsP1. Data are presented as mean ± SD (n = 5 per group). *p < 0.05, **p < 0.01, ***p < 0.001 by unpaired two-tailed t-test. Tissue viral loads were measured at 6 dpi in the right joint footpad (CHIKV, n = 5; CHIKV + sialokinin, n = 5). Statistical comparisons were performed using unpaired two-tailed t-test. d Immune cell subsets in the joint footpad were analyzed at 6 dpi (PBS, n = 7; sialokinin, n = 7; mock, n = 5). Data were analyzed by one-way ANOVA with Tukey’s post-hoc test. e CD4⁺ T cell cytokine profiles (IFN-γ, TNF-α, IL-4, IL-10, and IL-17A) were assessed at 6 dpi in the joint footpads of CHIKV-infected (PBS, n = 7; sialokinin, n = 7) and mock (n = 5) mice after PMA/ionomycin stimulation. Data are presented as mean ± SD and analyzed using one-way ANOVA with Tukey’s post-hoc test. CD4+ T cells isolated from right joint footpads at 6 dpi (n = 5 per group) were stimulated with CHIKV for ELISpot assay. Representative images and quantitative plots show reduced CHIKV-specific IFN-γ-producing CD4+ T cells in the joint footpads of treated mice at 6 dpi. Statistical comparison used unpaired two-tailed t-test. f Cell lysates from the joints of CHIKV-infected (PBS, n = 7; sialokinin, n = 7) and mock (n = 5) mice at 6 dpi were analyzed using a 36-plex microbead-based immunoassay. Immune mediators are grouped based on function. Heatmap colors indicate relative concentration (blue = low, red = high).