Capacity for antibody-dependent enhancement in mice immunized with vaccine candidates.

<p>Groups of BALB/c mice (n = 5) were immunized subcutaneously with 10 µg D2ED III or LD2ED III two times at a two-week interval. Live dengue-2 virus (1×10⁷ FFU) was injected intraperitoneally on the same schedule. Sera were collected from mice at 6 weeks after the first immunization. K562 cells were infected (MOI = 0.1) with (A) dengue-1, (B) dengue-3, (C) dengue-4, or (D) dengue-2 viruses in the presence or absence of serial 4-fold dilutions of pooled serum samples. The fold enhancement values were calculated as the percentage of infected cells in the presence of pooled serum samples divided by the percentage of infected cells in the absence of pooled serum samples. The results are expressed as the mean ± standard deviation from triplicate. Statistical significance was determined by the ANOVA Bonferroni post test at the same dilution. ^*<i>p</i><0.05 compared to D2ED III. ^#<i>p</i><0.05 compared to LD2ED III.