Fig. 3: Sialokinin reduces circulating CD169⁺ monocytes and joint inflammation in CHIKV-infected animals.

C57BL/6 WT 4-week-old (CHIKV, n = 8; CHIKV + sialokinin, n = 10) mice were infected with 1 × 10⁶pfu of CHIKV subcutaneously at the joint footpad. Sialokinin (1 μg) was administered concurrently with CHIKV in the treatment group. a CD11b⁺ Ly6C⁺ CD169⁺ monocytes in blood of CHIKV-infected mice were monitored daily by flow cytometry. b Representative images at 6 dpi show reduced joint footpad swelling in sialokinin-treated mice. Arrows indicate the area of persistent swelling. Joint swelling was monitored over 14 dpi. c Viremia was assessed from tail vein blood (1 to 10 dpi) via qRT-PCR targeting CHIKV nsP1. Data were collated from two independent experiments and are shown as mean ± SEM, analyzed using two-tailed t-test. d At 1 dpi, tissue viral loads were quantified by qRT-PCR of CHIKV nsP1 viral copies in the contralateral left joint footpad, the right joint footpad and the spleen of CHIKV-infected mice (CHIKV, n = 7; CHIKV + sialokinin, n = 7). Statistical comparisons used unpaired two-tailed t-test or Mann–Whitney U test, depending on data distribution. e At 6 dpi, viral loads in the infected right joint footpad were measured by qRT-PCR of CHIKV nsP1 viral copies (CHIKV, n = 5; CHIKV + sialokinin, n = 5) and analyzed using unpaired two-tailed t-test. f CD4⁺ T cell cytokine profiles (IFN-γ, TNF-α, IL-4, IL-10, and IL-17A) were assessed at 6 dpi in joint footpads of CHIKV-infected (CHIKV, n = 6; CHIKV + sialokinin, n = 7) and mock (n = 6) mice after PMA/ionomycin stimulation. Data are presented as mean ± SD, and analyzed using one-way ANOVA with Tukey’s post-hoc test. g Representative images of ELISpot wells depicting the number of IFN-γ-producing cells in enriched CD4+ T cells from joint footpads at 6 dpi. Quantitative plots show the total numbers of IFN-γ-producing CD4+ T cells per infected joint footpad. Statistical comparison between the two groups was performed using unpaired two-tailed t-test.