Abstract

Background. As malaria control is intensified, pregnant women may be less exposed to malaria, thus affecting the acquisition of protective antibody.Methods. Plasma samples were collected from Malawian and Papua New Guinean (PNG) pregnant women enrolled over seven year periods, during which malaria prevalence fell by over two thirds. Immunoglobulin G (IgG) levels to schizont extract, merozoite antigens and VAR2CSA-DBL5epsilon were measured by ELISA. Levels of IgG to variant surface antigens of infected erythrocytes (IEs) and merozoites, and levels of opsonising IgG to IEs, were measured by flow cytometry.Results. In both settings, levels of antibodies in pregnant women to recombinant antigens and to intact IEs but not opsonising antibodies decreased over time. After controlling for coverage with insecticide-treated nets (ITNs) these differences disappeared in the Malawian cohort, whereas in the PNG cohort time period was independently associated with decrease in several antibody responses measured by ELISA.Conclusion. The impact of falling parasite prevalence on anti-P. falciparum serological indicators in pregnant women varies by setting. Increased ITN coverage may affect development of antibodies to recombinant antigens, but levels of opsonising IgG remained stable over time. Opsonising IgG against placental-binding IEs may persist, thus offering longer-lasting protection against malaria during pregnancy.

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