Figure 3.

Binding-inhibitory responses of Papua New Guinea (PNG) children and the relationship with immunoglobulin G (IgG) to erythrocyte-binding antigen 175 (EBA-175) region II (RII). Plasma samples from a cohort of PNG children were used to determine the relationship between EBA-175 binding inhibition and total IgG response to EBA-175 RII as determined by enzyme-linked immunosorbent assay (ELISA). The continuous values for IgG responses were used to divide the cohort into 3 equal categories reflecting low, medium, and high EBA-175 region II IgG responders (x axis). The relationship between these antibody levels and absolute binding inhibition was assessed using the (A) native binding inhibition assay (BIA) and (B) recombinant BIA. Greater degrees of binding inhibition were indicated by low mean fluorescent intensity (MFI) and low optical density (OD), respectively. Differences across all tertiles were first tested using a Kruskal–Wallis test (P = .0001), and further differences between groups (low, intermediate, or high) were tested using a Wilcoxon rank sum test (P < .0001 for all tests). Bar graphs indicate the median binding activity, and bars indicate the interquartile range.