FIG 8.

IgG-depleted immune plasma does not mediate ADE of infection. IgG-depleted ZIKV-immune or control plasma and purified IgG fractions were prepared from day 148 (d148) pos ZIKV-immune (Hu0015) or control (Hu0002) plasma, as described in Materials and Methods. The same volumes were used for IgG-depleted plasma samples, and an amount which contained a level of IgG equivalent to that in the original plasma was used for purified IgG. (A) ZIKV-specific IgG levels in the IgG-depleted plasma samples and purified IgG fractions were measured on a ZIKV-coated plate by ELISA. See Fig. S6 for ZIKV-specific IgG and IgM levels in the HU0015 longitudinal plasma samples. (B and C) ADE assays (B) and neutralization assays (C) were performed as described for Fig. 1A. In panels A to C, averages ± SD of results from three independent experiments are shown. (D to F) Experiments were performed similarly to those described for Fig. 2 except that 2 μl of control plasma, 2 μl of day 148 pos ZIKV immune plasma, equivalent volumes of IgG-depleted plasma samples, or equivalent amounts of purified IgG were used (n = 8 to 11 per group). Data are presented as means ± SEM. Significant differences between groups for body weight and clinical score were analyzed by two-way ANOVA using Tukey’s multiple-comparison test, and survival data were analyzed by log rank (Mantel-Cox) test. *, P < 0.05; **, P < 0.01; ***, P < 0.001.