Figure 3. CHIKV DNA vaccination induces strong immunity in mice.

BALB/c mice were immunized three times, each 2 weeks apart, with 25 µg pVax1 vector or pMCE321-Env and sacrificed 1 week after the 3^rd immunization. (A) Splenocytes from immunized animals were harvested and cultured overnight in the presence of peptide pool matrix spanning the Envelope protein (pool-1 & pool-2) and the IFN-γ response to each pool was measured by ELISpot as described in the Materials and Methods. Values represent the mean and standard deviation of triplicate wells and are representative of three independent experiments. (B) Systemic anti-Env IgG levels after DNA immunization. Each group of inbred BALB/c mice (n = 4) was immunized with indicated vaccines. Mice were bled 1 week after each immunization, and then sera were diluted to 1/100 for reaction with CHIKV-Env. OD was measured at 450 nm. Values and bars represent mean (n = 4) and the SEM. (C and D) Quantification of CHIKV specific neutralizing and HI titer in sera from DNA immunized mice (pVax1/pCHIKV-E1/pCHIKV-E2 and pMCE321) to CHIKV. The nAb titers are plotted as the highest dilution of serum that resulted in at least 50% inhibition of CPE. The highest dilution of the serum that inhibited hemagglutination was recorded as the HI titer. Similar results were observed in three independent experiments with at least n = 4 per group for each experiment.