(C) WT C57BL/6 mice were vaccinated subcutaneously with 1E6 PFU of WT-CHIKV or CHIKV nsP-mutants (RH, RHEV and EV) at the metatarsal region of the footpad. Challenge with 1E6 PFU of WT-CHIKV was performed via the same route at 90 dpv. 