Figure 4.

Association of immunoglobulin G3 (IgG3) antibody responses with disease progression. A, Viral load in early and late IgG3 responders during the acute phase of disease (median, 4 d post–illness onset [PIO]). Data are presented as mean ± standard error of the mean. Statistical significance was measured using Mann–Whitney U test. ***P < .001. Abbreviation: PFU, plaque-forming units. B, Disease severity in early and late IgG3 responders during the acute phase of disease. Severity was previously defined. Histogram shows the percentage of patients with mild (n = 14) or acute severe clinical phenotypes (n = 16). Statistical significance was measured using 2-sided Fisher exact test between the number of patients with severe phenotype in 2 responder groups. ***P < .0001. C, Interleukin 6 levels in early and late IgG3 responders were determined using a multiplex-bead based assay. Horizontal dotted lines represent median values of healthy controls. Statistical significance was measured using Mann–Whitney U test. **P < .01. D, Viral clearance from a median of 4 d to a median of 10 d PIO in early and late IgG3 responders. E, Persistent arthralgia in early and late IgG3 responders during the chronic phase of disease (2–3 mo PIO). Histogram shows the percentage of patients with full recovery or persistent arthralgia. Statistical significance was measured using 2-sided Fisher exact test between the patients who have fully recovered and patients with persistent arthralgia in the 2 responder groups. *P = .04.