FIG 9.

Single-dose immunization with ΔC-CHIKV protects IFNAR^−/− mice from CHIKV infection. (A) Experimental design. Three groups of 6-week-old IFNAR^−/− mice (n = 6 per group) were immunized subcutaneously in the ventral/lateral side of the hind foot once with 10⁴ PFU of ΔC-CHIKV or 2% FBS–DMEM (culture medium control) or left untreated (mock). On day 30 postimmunization, mice were challenged with 10³ PFU of WT CHIKV s.c. in feet. (B) Neutralizing antibody titers present in mouse sera on the indicated days postimmunization. (C) Animal survival postchallenge. (D) Footpad swelling (n = 6 feet per group) postchallenge. (E) Weight loss after challenge. (F) Viremia postchallenge. Viremia from day 1 to day 5 postchallenge was measured by qRT-PCR. In panels B to F, data represent means ± SD for groups of mice, and the horizontal dotted line represents the limit of detection. Student’s t tests were used to determine differences between two groups, and a Kruskal-Wallis test followed by Dunn’s test was used for multiple comparisons. Two and four asterisks indicate statistical differences between the indicated groups with P values of <0.01 and <0.0001, respectively.