Figure 3.

Role of anti–chikungunya virus (CHIKV) immunoglobulin G3 (IgG3) in in vitro neutralizing activity against CHIKV from plasma samples of early and late IgG3 responders. A, Pooled plasma samples collected at median 10 d post–illness onset (PIO) (early IgG3, n = 16; late IgG3, n = 14) were added to plates precoated with purified Chikungunya virion for depletion of anti-CHIKV antibodies. Depleted samples were subjected to anti-CHIKV IgG3 antibody detection with virion-based enzyme-linked immunosorbent assay (ELISA). B, Depleted samples were subjected to in vitro neutralizing activity detection with a seroneutralization assay. C, IgG3 antibodies from pooled plasma samples collected at a median of 10 d PIO (early IgG3, n = 16; late IgG3, n = 14) were depleted as described in the “Methods” section and measured for anti-CHIKV IgG3 antibodies with virion-based ELISA. D, Depleted samples were subjected to in vitro neutralizing detection in a seroneutralization assay. All samples assayed were performed at 1:500 dilution (n = 3). Plasma from healthy donors was used as negative controls. Data are presented as mean ± SD. Data are representative of 3 independent experiments. Statistical significance was measured using Mann–Whitney U test. *P < .05. **P < .01.