FIG 2.

Neutralizing antibodies cannot elicit ADCC but can elicit ADE in vitro. We examined the ability of neutralizing antibodies to elicit Fc-mediated effector functions either on the surface of infected cells or against the virion itself. (A) Vero cells were infected with MR766 ZIKV and used as targets for measuring Fc-FcγR effector functions with a genetically modified Jurkat cell line expressing human FcγRIIIa with an inducible luciferase reporter gene. Fold induction was measured in relative light units, and results were compared to infected cells with no antibody added. Error bars represent standard error of the means (SEM). (B) To examine whether enhancement of flavivirus infection in vitro is observed, monoclonal antibodies were incubated with ZIKV and added to FcγR-bearing K562 cells. All monoclonal antibodies were tested at a starting concentration of 3.3 μg per ml and serially diluted 4-fold. Both assays were run in duplicate, and fold induction was measured as the percentage of infected cells as determined by flow cytometry divided by the percentage of infected cells with no antibody added (virus alone). (C) Representative flow cytometry plots for antibody AD5 and control IgG are shown.