SEROREACTIVITY WITH THE PLASMODIUM-FALCIPARUM BLOOD-STAGE ANTIGEN-PF332 IN ADULTS AND CHILDREN FROM MALARIA-ENDEMIC REGIONS

It has earlier been reported that the human monoclonal antibody (MoAb 33G2) and polyclonal antibodies reactive with Pf332 may interfere in v itro with the erythrocytic cycle of Plasmodium falciparum at two poten tial target sites for protective antibodies, indicating that the antig en may constitute an important target for immune responses during mala ria infections. MoAb 33G2 shows its highest reactivity with repeated s equences in the antigen Pf332 and also cross-reacts with determinants in Pf155/RESA. This study was conducted in order to assess the prevale nce of seroreactivity against Pf332 in individuals residing in areas o f different malaria endemicity, and in children with different degrees of disease severity. We now report that individuals resident in malar ia-endemic regions show a high prevalence of seroreactivity to antigen Pf332 repeat sequences. The mean antibody concentrations were signifi cantly higher in donors from Liberia, Madagascar and Gambia compared w ith Thai and Colombian donors, probably reflecting the higher degree o f exposure in the African regions. Although the levels of such antibod ies in individual sera correlated well with the levels of antibodies t o one Pf155/RESA repeat peptide, only a minor part of the peptide-reac tive antibodies were cross-reactive between the two antigens. In Gambi an children, the mean concentrations of antibodies reactive with Pf332 or Pf155/RESA peptides were significantly higher in children with sev ere than with mild malaria. Further longitudinal studies are needed to evaluate the capacity of Pf332 to induce potentially protective or ha rmful antibody responses.