HUMORAL RESPONSE TO PLASMODIUM-FALCIPARUM RING-INFECTED ERYTHROCYTE SURFACE-ANTIGEN IN A HIGHLY ENDEMIC AREA OF PAPUA-NEW-GUINEA

The prevalence and concentration of antibodies to ring-infected erythr ocyte surface antigen (RESA) were measured in blood samples collected during a cross-sectional survey conducted in Papua New Guinea. Antibod ies were measured by enzyme-linked immunosorbent assay to the recombin ant RESA protein in 1,398 subjects and to RESA 8 and RESA 11 synthetic peptides in a subsample of 200 adults. Overall, the seropositivity ra te to recombinant RESA was 66% and the geometric mean antibody concent ration was 28 mu g/ml. There was a slow increase in antibody prevalenc e and concentration with age that continued to occur even after 40 yea rs of age. In children less than 10 years of age, there was a signific ant positive correlation between both RESA antibody prevalence and con centration and concurrent infection with Plasmodium falciparum. The op posite was true in adults more than 20 years of age, with those having a high antibody concentration to RESA being less Likely to be parasit emic at the time of the survey. This observation was consistent with t he finding of a weak but significant negative correlation between log antibody concentration and log P. falciparum density, which was mainly found in adults. No consistent correlation was found between humoral immune response to RESA and morbidity indicators.