Fig 7. Effect of antibody isotype on antibody dependent enhancement (ADE) of infection of U937 monocytes.

(A) DENV2 16681 reporter virus particles were pre-incubated with serial dilutions of IgG1 (filled circles), monomeric IgA1 (open circles), or polymeric IgA1 (open squares) forms of F25.S02 (blue), EDE1-C10 (orange), or SIgN-3C (green) prior to infection of U937 cells, which express Fc receptors for both IgG and IgA. IgG1 and IgA1 antibodies were tested individually in the assay. (B) Competitive ADE assays in U937 monocytes. F25.S02 (top row, blue), EDE1-C10 (middle row, orange) or SIgN-3C (bottom row, green) IgG1 was mixed with either autologous IgA1 (left panel, solid lines) or an IgA1 isotype control (right panel, dashed lines) at the indicated ratios by mass before serial dilution and pre-incubation with concentrated DENV2 16681 reporter virus particles. The assay was performed in two independent experiments, each in duplicate wells. The data points and the error bars represent the means and the range of the duplicates, respectively, from one representative experiment. (C) Area under the curve analysis for experiments represented in (B). For both biological replicates the area of the curve for each infection condition was calculated and normalized to infection in the 100% IgG1 condition. The data points and error bars represent the mean and the range of two independent experiments, respectively.