Figure 2: Effect of preimmunity to DENV2 on immunogenicity of the dengue tetravalent DNA vaccine. Groups of four mice were preimmunized with 5.0 107 (closed circle) or 5.0 106 (open circle) PFU of DENV2 antigen or inoculated with PBS (closed triangle). Four and eight weeks later, these mice were vaccinated with 40 g of the dengue tetravalent DNA vaccine (10 g for each type). Pooled sera were examined for neutralizing antibody titers (upper panel) and ELISA antibody levels (lower panel) against DENV14 (indicated above the upper panel).