title: Decreasing malaria prevalence and its potential consequences for immunity in pregnant women.
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 7-year periods, during which malaria prevalence fell by over two thirds. Immunoglobulin G (IgG) levels to schizont extract, merozoite antigens, and VAR2CSA-DBL5ε were measured by enzyme-linked immunosorbent assay (ELISA). Levels of IgG to variant surface antigens of infected erythrocytes (IEs) and merozoites and levels of opsonizing 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 of opsonizing antibodies decreased over time. After adjustment for coverage with insecticide-treated bed nets (ITNs), these differences disappeared in the Malawian cohort, whereas in the PNG cohort, time was independently associated with a decrease in several antibody responses measured by ELISA.
  
  
  CONCLUSIONS
  The impact of falling parasite prevalence on anti-Plasmodium falciparum serological indicators in pregnant women varies by setting. Increased ITN coverage may affect development of antibodies to recombinant antigens, but levels of opsonizing IgG remained stable over time. Opsonizing IgG against placental-binding IEs may persist, thus offering longer-lasting protection against malaria during pregnancy.
authors.affiliation: Department of Medicine Doherty Institute.
authors.forename: Andrew
authors.initials: A
authors.lastname: Teo
authors.affiliation: Department of Medicine Victorian Infectious Diseases Service Doherty Institute.
authors.forename: Wina
authors.initials: W
authors.lastname: Hasang
authors.affiliation: Department of Medicine Victorian Infectious Diseases Service Doherty Institute.
authors.forename: Louise M
authors.initials: LM
authors.lastname: Randall
authors.affiliation: Burnet Institute, Melbourne, Australia.
authors.forename: Gaoqian
authors.initials: G
authors.lastname: Feng
authors.affiliation: Nossal Institute for Global Health, University of Melbourne.
authors.forename: Lauren
authors.initials: L
authors.lastname: Bell
authors.affiliation: Department of Medicine Doherty Institute.
authors.forename: Holger
authors.initials: H
authors.lastname: Unger
authors.affiliation: Burnet Institute, Melbourne, Australia.
authors.forename: Christine
authors.initials: C
authors.lastname: Langer
authors.affiliation: Burnet Institute, Melbourne, Australia.
authors.forename: James G
authors.initials: JG
authors.lastname: Beeson
authors.affiliation: Papua New Guinea Institute of Medical Research, Goroka.
authors.forename: Peter M
authors.initials: PM
authors.lastname: Siba
authors.affiliation: Walter and Eliza Hall Institute of Medical Research, Parkville Barcelona Center for International Health Research, Spain.
authors.forename: Ivo
authors.initials: I
authors.lastname: Mueller
authors.affiliation: Malawi-Liverpool-Wellcome Trust Clinical Research Programme College of Medicine, Blantyre Liverpool School of Tropical Medicine, United Kingdom.
authors.forename: Malcolm E
authors.initials: ME
authors.lastname: Molyneux
authors.affiliation: Nossal Institute for Global Health, University of Melbourne.
authors.forename: Graham V
authors.initials: GV
authors.lastname: Brown
authors.affiliation: Department of Medicine Victorian Infectious Diseases Service Doherty Institute.
authors.forename: Stephen J
authors.initials: SJ
authors.lastname: Rogerson
mesh_terms: D000328:Adult; D000913:Antibodies, Protozoan / Q000097:blood / Q000276:immunology; D000953:Antigens, Protozoan / Q000097:blood / Q000276:immunology; D004797:Enzyme-Linked Immunosorbent Assay; D005260:Female; D005434:Flow Cytometry; D006801:Humans; D007113:Immunity, Innate / Q000276:immunology; D007074:Immunoglobulin G / Q000097:blood / Q000276:immunology; D016778:Malaria, Falciparum / Q000453:epidemiology / Q000276:immunology*; D008295:Malawi / Q000453:epidemiology; D010219:Papua New Guinea / Q000453:epidemiology; D010963:Plasmodium falciparum / Q000276:immunology*; D011247:Pregnancy / Q000276:immunology; D015597:Pregnancy Complications, Parasitic / Q000276:immunology*; D015995:Prevalence; D055815:Young Adult
chemical_list: D000913:Antibodies, Protozoan; D000953:Antigens, Protozoan; D007074:Immunoglobulin G
keywords: Malawi; Papua New Guinea; Plasmodium falciparum; acquisition; antibody; longer-lasting; pregnancy