Vaccination with Conserved Regions of Erythrocyte-Binding Antigens Induces Neutralizing Antibodies against Multiple Strains of Plasmodium falciparum
Figure 3
EBA-175 inhibitory antibodies block merozoite invasion through receptors other than Glycophorin A.
(A) Western blot of post-invasion culture supernatants from W2mef and W2mef175-Cterm parasites probed with monoclonal antibody 9C4. This specifically recognizes EBA-175 region III-V and shows the truncated form of the protein that includes RIII-V was present in W2mef175-Cterm parasites. (B) EBA-175 requires motifs downstream of region 5 for correct trafficking within merozoites prior to invasion. Late segmented schizonts (ETS preparations) were co-stained with antiserum against EBA-140 to detect micronemes (green), along with inhibitory mAb targeting EBA-175 (red). Indirect immuofluorescence and phase contrast micrographs show correct co-localization within micronemes in wild type parasites (panels 1 &2) and mis-localization of truncated EBA-175 protein in transgenic parasites, often with aberrant, early secretion (panels 3&4). Free and invading merozoites, co-stained with the same W2mef-specific EBA-175 mAb (red) and RON4 to mark the tight junction (green), show that EBA-175 is present during merozoite invasion in both wild type and transgenic parasites. In all cases nuclei are stained with DAPI (blue) and scale bars show 2 μm. (C) W2mef and W2mef175-Cterm parasites were tested in GIA with IgG against EBA-175 RIII-V (3D7). Both parasite lines are inhibited equally efficiently by this IgG, whereas no inhibition is seen against EBA-175 KO parasites (One-cycle assay).