Fig. 4: CSP-specific antibodies induced opsonic phagocytosis by neutrophils.

A The level of opsonic phagocytosis by neutrophils of beads coated with different regions of CSP. Beads coated with full-length CSP (FL), the CT region, the NT region and the NANP repeat region (repeats) were opsonized with antibodies from a pool of Kenyan adult donors. Unopsonized beads were used as a negative control for assay background. Data show mean and standard error from six experiments (P = 0.051 and P = 0.187 for comparisons between NT and NANP or CT domains, respectively; one-way ANOVA). The level of phagocytosis activity was expressed relative to the IgG reactivity to each region (see Supplementary Fig. 8A). B Antibodies from the Kenyan adult pool were tested for their ability to promote the binding of FcγRIIa and FcγRIII binding activity with each region of CSP. The level of FcγR binding was standardised according to the level of total IgG binding to each CSP construct (FcR-binding efficiency; see Supplementary Fig. 8A). Data show mean and standard error based on three experiments. FcγRIIa and FcγRIII binding to the NT region was significantly higher compared to the NANP-repeat region or CT region (P < 0.001, two-way ANOVA). C Opsonic phagocytosis of P. falciparum sporozoites by neutrophils mediated by rabbit polyclonal antibody to CSP, compared to no-antibody (no Ab) control (P < 0.001, unpaired t test). Data show mean and standard errors from four experiments. D Opsonic phagocytosis of P. falciparum sporozoites by neutrophils mediated by mouse monoclonal antibody (2H8) against CSP at different concentration, compared to mouse monoclonal antibody (3D11) against P. berghei CSP as a control (P = 0.0025, one-way ANOVA). Data shown are mean and standard errors from four experiments. E Rabbit IgG to the NT region was more efficient in promoting phagocytosis of PfCSP-P. berghei sporozoites by neutrophil compared to rabbit IgG to the CT region (P = 0.0079, unpaired t test). Data shown are mean and standard error based on two experiments. Phagocytosis activity was standardised relative to the level of IgG to CSP of each rabbit antibody. F Rabbit antibodies generated against the NT region were tested for reactivity against an array of overlapping peptides (15 aa with 12 aa overlap) including the NT region, NANP/NVDP repeat and the junctional region. Data show IgG reactivity to different peptides; the reactive peptides include a 21-aa region corresponding to CSP residues 76–96 (P = 0.036 for differences in peptide reactivity, Kruskal–Wallis test, two experiments). Error bars represent the range from two experimental repeats. Peptide sequences are provided in Supplementary Fig. 8B.