Figure 3: Effect of preimmunity to JEVAX on immunogenicity of the dengue tetravalent DNA vaccine. Groups of six mice were preimmunized by two inoculations, with a 2-week interval, with a 1/2 (closed circle) or 1/10 (open circle) human dose of JEVAX or inoculated with PBS (closed triangle). Two and six weeks after the second inoculation for preimmunization, these mice were vaccinated with 40 µg of the dengue tetravalent DNA vaccine (10 µg for each type). Pooled sera were examined for neutralizing antibody titers (upper panel) and individual sera were examined for ELISA antibody levels (lower panel) against DENV1–4 and JEV (indicated above the upper panel). For ELISA, mean ELISA values were plotted with SD (indicated by bars). Signifi cant differences in mean ELISA values from non-preimmunized mice were indicated by * (P<0.05), ** (P<0.01) and *** (P<0.001) for mice preimmunized with a 1/2 dose of JEVAX and + (P<0.05), ++ (P<0.01) and +++ (P<0.001) for mice preimmunized with a 1/10 dose of JEVAX.