Figure 4

Simultaneous induction of antibodies that recognize and neutralize DEN virus serotypes 2 and 4. (A) IFA of DEN virus-infected cells using murine antisera. BHK cells were either mock infected (panels a, e, i and m) or infected separately with DEN-1 (panels b, c, d), DEN-2 (panels f, g, h), DEN-3 (panels j, k, l) and DEN-4 (panels n, o, p) viruses. One day after infection, cells were fixed and probed separately with different antisera as the source of primary antibodies. The antisera were obtained from mice, immunized with purified recombinant proteins [rEDIII-1 (panels a, b), rEDIII-2 (panels e, f), rEDIII-3 (panels i, j), and rEDIII-4 (panels m, n)] and rAd/plasmid [rAd-C/pVAX1 (panels c, g, k, o) or rAd-Bg/pVAX-EDIII-4/2 (panels d, h, l, p)]. The resultant virus/antibody complexes were visualized using anti-mouse IgG-FITC conjugate. (B) LLCMK2 monolayers were separately infected with each of the four DEN viruses (DEN-1: filled circles; DEN-2: filled squares; DEN-3: open circles; & DEN-4: open squares) that had been pre-incubated with serial two-fold dilutions of pooled immune serum drawn from the rAd-Bg primed/plasmid pVAX-EDIII-4/2 boosted animals. The resultant plaque counts, expressed as percent inhibition of virus infectivity (with reference to the number of plaques generated in the absence of antiserum, which was taken to represent 100% infectivity) are plotted as a function of antiserum dilution. Each data point shown represents the mean of four replicate assays (the error bars represent SD).