Figure 6. Immunogenicity of CHIKV DNA vaccine in nonhuman primates.

(A) IFN-γ ELISpot assay results presented are from individual macaques 2 weeks after the fifth immunization against pMCE321 administered vaccine. PBMCs harvested from animals immunized with pMCE321 were used in the IFN-γ assay. We also tested PBMCs that were depleted of CD8⁺ T cells by magnetic bead separation before in vitro stimulation. The PBMCs were incubated in the presence of the following stimulators and controls: R10 medium (negative control), Con A (5 µg/ml positive control), and 10 µg/ml CHIKV peptide mix. Data are presented as the SI (experimental counts/spontaneous counts), where the spontaneous count wells are from the R10-negative control wells as described in Materials and Methods. Values represent the mean of triplicate cultures and are representative of three independent experiments. (B) nAb titers from sera of DNA vaccinated monkeys are shown. The pMCE321 DNA vaccine construct induced nAb responses ranging from 80-1,280 titers and mimicked those induced in convalescent patient sera.