Immune responses induced by CHIKV infection.

Neonate C57BL/6 mice (6–8 days old) were infected by intradermal injection with 10−10⁶ PFU of CHIKV. (A) Serum anti-E2 IgG was detected by ELISA in all groups at 29 dpi. (B) The neutralizing capacity of the serum from the mice in the control group and the 10⁶ PFU group was tested by the PRNT assay. (C) Serum anti-E2 IgG in the 10⁶ PFU group was assessed by ELISA at 29, 36, 42 and 50 dpi. (D, E) Splenocytes were isolated at 29 dpi or (F) 50 dpi and stimulated with CHIKV-derived capsid, E2 and E1 peptides for 4.5 h, and the frequencies of IFN-γ-producing CD8+ T cells were assessed by FACS. Ctrl, control mice inoculated with BHK-21 cell supernatant. n = 4 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.