Epitope-specific impairment of production of antibody against merozoite surface glycoprotein 1 of Plasmodium falciparum in symptomatic patients with malaria

We analyzed the relationships between levels of antibody specific for meroz oite surface glycoprotein-l (MSP1) of Plasmodium falciparum and clinical ma nifestations in humans. We prepared recombinant MSPI proteins representing block 3 (M3), block 6 (M6), blocks 1-6 (M1/6), and block 17. When we divide d the slide-positive individuals in Guadalcanal into symptomatic and asympt omatic groups, the former group showed lower IgG levels against M6 and bloc k 17, but not against M3, than did the asymptomatic group (P < 0.01). The p ossibility of nonspecific suppression was unlikely, given that the levels o f antibody against poliomyelitis virus observed in the two groups were almo st the same. Among the IgG subclasses tested, production of cytophilic IgG( 3) seemed to be dominant. When we analyzed epitopes recognized by antibodie s against block 17, a peptide (SSSNFLGIS) was preferentially recognized by sera from asymptomatic individuals. These results suggest that clinical sym ptoms occurring during falciparum malaria seem to be associated with the de velopment of levels of antibody against particular epitopes on MSP1, which is under the control of an immunoregulatory mechanism.