FIG 1.

Pretreatment with IL-2 Ab Cx reduces joint swelling in CHIKV-infected mice. WT mice (n = 5 per group) were i.p. injected with PBS, IL-2 only, JES6-1 only, or IL-2 Ab Cx daily for 3 days. Blood samples were obtained from tail veins and analyzed with flow cytometry. (A) Representative scatter plots (left) and bar chart of the Foxp3⁺ CD25⁺ peripheral Treg population in mice. Numbers indicate the frequency of Foxp3⁺ CD25⁺ Tregs in total peripheral CD4⁺ cells. Following PBS, IL-2 only, JES6-1 only, or IL-2 Ab Cx treatment, the mice were infected s.c. with 10⁶ PFU CHIKV-SGP011. Noninfected (NI) mice were included as negative control. (B) Representative images showing joint footpad swelling at 6 dpi in CHIKV-infected mice. Red arrows indicate areas of swelling. (C) Joint swelling was measured daily from 1 to 15 dpi. (D) Viremia was determined from blood collected from tail vein from 1 to 14 dpi. (E) Viral load of the infected joint footpad was measured at 6 dpi. All data are means and standard deviations (SD) and are representative of three independent experiments. Statistical analysis was done across all CHIKV-infected groups using one-way ANOVA, followed by Dunnett's posttest comparing each group to the PBS-CHIKV group. (F) Histological analysis of CHIKV-infected footpad samples from 6 dpi pretreated with either PBS or IL-2 Ab Cx and stained with H&E. *, edema; arrows, infiltrates; B, bone; M, muscle; T, tendon. The bar chart shows the average cellular infiltrate per area. Data are means and SD. Statistical analysis was carried out using the Mann-Whitney two-tailed test. **, P = 0.0017 (2 dpi joint swelling) or 0.0059 (4 dpi joint swelling); ***, P < 0.0001 (3, 5, 7, 8, 9, 10, 11, 12, 14, and 15 dpi joint swelling and IL-2 Ab Cx Treg expansion) or 0.0004 (6 dpi joint swelling).