Age-related prevalence of antibody response against three different, defined Plasmodium falciparum antigens in children from the Haut-Ogooué province in Gabon.

The kinetics of the humoral response to defined Plasmodium falciparum antigens was studied in 543 children, 1 month to 15 years old, living in an area endemic for malaria. The antigens used for enzyme-linked immunosorbent assay were (i) the synthetic peptide (NANP)40 representing the immunodominant repeated region of the circumsporozoite protein, and (ii) the fusion peptide 31.1, representing the N-terminal portion of the 83 kDa polypeptide expressed at the surface of merozoites which is a processed product of the 190-200 kDa glycoprotein. In addition, glutaraldehyde-fixed infected red blood cells (RBC) were used to detect ring-infected erythrocyte surface antigen (RESA) and unfixed infected RBC to detect intra-erythrocytic asexual form (IEF) antigens by immunofluorescence. In the 1 to 2 months age group, 50%, 26% and 21% of the children had antibodies for IEF, (NANP)40 and 31.1 respectively, but none had anti-RESA antibodies. The proportions of positive subjects decreased until 3 to 6 months and then increased progressively for the 4 antigens, approaching, but not reaching, adult values by the age of 15 years. Antibodies against specific antigens were acquired concomitantly. Children born from (NANP)40-positive mothers showed enhanced anti-(NANP)40 IgG responses.