Mutations in nsP2 of wCHIKV strongly affect the development of viremia in mice. (A) Two-to-three-week old C57BL/6 mice (n = 6/group) were infected in the left footpad with 5x103 PFU of wCHIKV nsP2 mutants and parental wCHIKV. Blood samples were taken on days 1, 2 and 3 PI, and the levels of viremia were assessed by plaque assay on BHK-21 cells. The dashed line indicates the limit of detection (LOD). Results are presented as means with standard deviations and significant differences, determined by one-way ANOVA, followed by Tukey’s multiple comparisons test. They are indicated by asterisks as follows: ****, P<0.0001. wCHIKV is compared to other groups. (B) Weight change post infection with indicated viruses. Results are presented as means with standard deviations.