Cross-binding and cross-neutralizing IgG.

<p>Longitudinal plasma samples of three patients with primary DENV2 infection (A and C) and three patients with secondary DENV2 infection (B) were analyzed at the following time points after onset of fever: 1–3 days, 4–7 days and 15–25 days. Plasma samples were diluted three-fold over a range of 1∶200 to 1∶437'400 and analyzed by ELISA (A and B) and in a neutralization assay (C) for all four serotypes. A) ELISA with plasma from patients with primary infection with DENV2. B) ELISA with plasma from patients with primary infection with DENV2. Cross-binding to all four serotypes was observed after primary infection and was more pronounced after secondary infection. C) For the neutralization assay 1∶200 to 1∶437'400 diluted plasma samples were incubated with a constant amount of virus and the percentage of infected cells for each plasma dilution was determined by flow cytometry. EC50 values after curve fit are shown in the upper left of each graph. All curves fit with an R²>0.95 except for DENV4 of patient 3, where the R² is 0.78. The results of both assays are representative of at least two separate experiments for all patients and time points.