FIG 7.

Immunogenicity and neutralizing activity of tetravalent DNA or VLP vaccines. Six-week-old female BALB/c mice (n = 4) were immunized with 80 μg (20 μg of each serotype) of tetravalent DNA or tetravalent DENV VLPs three times at 3-week intervals. DNAs were administered by intramuscular injection and electroporation, and VLPs were administered by regular intramuscular injection with alum. Sera were collected 2 weeks after the last immunization. DNA_wild type, DENV1-4 prM-E-encoding plasmids; DNA_F108A, DENV1-4 VLP-encoding plasmids; DENV VLP, purified DENV1-4 VLPs. (A) Serum anti-flavivirus IgG titers were determined by ELISA. Mean log₁₀ ELISA titers (with SD) are shown. *, P < 0.05 (one-way analysis of variance [ANOVA] followed by Tukey's multiple-comparison test). (B) Serum neutralization titers against DENV1 to -4. Each symbol represents the FRNT₅₀ titer from an individual mouse, and the geometric mean titers are represented by horizontal bars. ***, P < 0.001; **, P < 0.01; *, P < 0.05; ns, not significant (one-way ANOVA followed by Tukey's multiple-comparison test).