Figure 2

Inhibition of secondary processing of MSP-1 by antibodies specific for epitopes throughout the MSP-1 molecule. Secondary processing of MSP-1 in preparations of isolated merozoites was monitored by western blot using mAb X509 to detect the appearance of MSP-1₃₃ in merozoite supernatants. (A) Shown is processing of MSP-1₄₂ after incubation with medium alone (control), the serine protease inhibitor PMSF (a very effective inhibitor of PfSUB2), pre-immune antibody (PI), malaria unrelated control antibody (C), or with rabbit antibodies specific for various MSP-1 fragments. (B) Shown is the dependency of MSP-1 secondary processing on antibody concentration. Merozoites were incubated in the presence of pre-immune antibody (PI), malaria unrelated control antibody (C), PMSF, or varying amounts of αMSP-1₈₃, αMSP-1₄₂ or αMSP-1_42ΔEGF antibodies ranging in concentration from 1% to 10% (v/v) antibody solution. The two sets of panels show western blot results of two different loadings of supernatant samples on SDS-PAGE. The additional bands that appear on all the blots with increasing concentrations of test IgG are due to low-level non-specific recognition of IgG heavy and light chains on the blots by the secondary antibodies used. Loading controls (using mAb 4G2 to detect shedding of the AMA-1 ectodomain) confirmed equal loading in all lanes (data not shown).