Figure 6

Antibodies promoting phagocytosis are associated with a reduced risk of malaria in the Chonyi cohort. Children were categorized into tertiles according to their (A) relative phagocytosis index, (B) ELISA IgG1 optical density (OD) levels against whole merozoites and (C) ELISA IgG3 OD levels against whole merozoites. Top tertile (red line), middle tertile (green line) and bottom tertile (yellow line) levels. Phagocytosis of merozoites was significantly associated with a reduced risk of malaria (log rank test P = 0.007), while IgG subclass antibodies against whole merozoites were not (log rank test P = 0.914 and P = 0.396, for IgG1 and IgG3, respectively). (D) The phagocytosis index, (E) whole merozoite IgG1 and (F) whole merozoite IgG3 antibodies were significantly associated with the sum of IgG responses against any one of MSP2, MSP3, MSP1₁₉, AMA1, EBA175 and MSP1 block 2 [6] in the Chonyi cohort. Cuzick test for trend across ordered groups, z = 2.98, P = 0.004; z = 5.56, P <0.001 and z = 6.36, P <0.001, for the RPI, IgG1 and IgG3 against merozoites respectively. AMA1, apical membrane antigen 1; EBA, erythrocyte binding antigen; MSP, merozoite surface protein; OD, optical density.