Viral replication in mice infected with different viral doses.

Neonate C57BL/6 mice (6–8 days old) were infected by intradermal injection with 10−10⁶ PFU of CHIKV. (A) Schematic diagram of the experimental design and the course of disease. Expression of viral positive strand RNA in the (B) ipsilateral and (D) contralateral feet was detected at 2, 6, and 29 dpi in all groups or (C, E) at 50 dpi in the high dose group. All the samples were assessed by qRT–PCR using nsP1-specific primers and probes. Ctrl, control mice inoculated with BHK-21 cell supernatant. n = 4–5 mice per group. All data are presented as the mean ± SD. *: p< 0.05; **: p< 0.01; ***: p< 0.001; statistical relevance was determined by one-way ANOVA (B, D) or unpaired t test (C, E).