ANTIBODIES TO RING-INFECTED ERYTHROCYTE SURFACE-ANTIGEN (PF155/RESA) PROTECT AGAINST PLASMODIUM-FALCIPARUM PARASITEMIA IN HIGHLY EXPOSED MULTIGRAVIDAS WOMEN IN MALAWI

To determine whether antibodies to defined B-cell epitopes of Plasmodium falciparum antigens were related to protection against parasitemic attacks in highly exposed pregnant women, two samples of 235 with no initial P. falciparum parasitemia (NP) and 89 multigravidas who presented initial P. falciparum parasitemia (IF) were enrolled in an antimalarial prophylaxis trial in the Mangochi District in Malawi. Sera were collected under effective prophylaxis and tested for antibody measurement using FAST-ELISA. Mean antibody titers to synthetic peptides reproducing the 3 major B-cell epitopes of the ring-infected erythrocyte surface antigen (Pf155/RESA), as (EENV)(4), (EENVEHDA)(4) and (DDEHVEEPTVA)(3), were higher in the NP than in the IP multigravidas, and this remained consistent within the season of malaria transmission (all p<0.05). All antibodies to Pf155/RESA were positively intercorrelated within each group. Mean antibody titers to peptide (PNAN)(5) reproducing the major B-cell epitope of the circumsporozoite protein (CS protein) were similar between NP and LP multigravidas in both dry and rainy season. Antibodies to Pf155/RESA epitopes may contribute to immune protection against blood-stage parasite multiplication in these highly malaria-exposed pregnant women.