title: Multiplicity of Plasmodium falciparum infection following intermittent preventive treatment in infants.
abstract: BACKGROUND
  Intermittent preventive treatment in infants with sulphadoxine-pyrimethamine (IPTi-SP) reduces malaria morbidity by 20% to 33%. Potentially, however, this intervention may compromise the acquisition of immunity, including the tolerance towards multiple infections with Plasmodium falciparum.
  
  
  METHODS
  Plasmodium falciparum isolates were obtained from children participating in two Ghanaian IPTi-SP trials (Tamale, Afigya Sekyere) at 15 months of age, i.e., six months after they had received the second dose of IPTi-SP or placebo. By typing the polymorphic merozoite surface protein 1 (msp1) and msp2 genes, multiplicity of infection (MOI) was assessed in 389 isolates. A total of additional 133 samples were collected in Tamale at 3, 6, 9, and 12 months of age. Comparisons of MOI between groups were done by non-parametric statistical tests.
  
  
  RESULTS
  The number of distinguishable P. falciparum clones (MOI) ranged between one and six. Mean MOI in Tamale was stable at 2.13 - 2.17 during the first year of life, and increased to 2.57 at age 15 months (P = 0.01). At no age did MOI differ between the IPTi-SP and placebo groups (each, P ≥ 0.5). At 15 months of age, i.e., six months after the second dose, MOI was very similar for children who had received IPTi or placebo (means, 2.25 vs. 2.33; P = 0.55) as was the proportion of polyclonal infections (69.6% vs. 69.7%; P = 0.99). Adjusting for study site, current and prior malaria, parasite density, and season did not change this finding.
  
  
  CONCLUSIONS
  IPTi-SP appears to have no impact on the multiplicity of infection during infancy and thereafter. This suggests that tolerance of multiple infections, a component of protective immunity in highly endemic areas, is not affected by this intervention.
authors.affiliation: Institute of Tropical Medicine and International Health, Charité - University Medicine, Berlin, Germany.
authors.forename: Ulrike
authors.initials: U
authors.lastname: Buchholz
authors.forename: Robin
authors.initials: R
authors.lastname: Kobbe
authors.forename: Ina
authors.initials: I
authors.lastname: Danquah
authors.forename: Philipp
authors.initials: P
authors.lastname: Zanger
authors.forename: Klaus
authors.initials: K
authors.lastname: Reither
authors.forename: Harry H
authors.initials: HH
authors.lastname: Abruquah
authors.forename: Martin P
authors.initials: MP
authors.lastname: Grobusch
authors.forename: Peter
authors.initials: P
authors.lastname: Ziniel
authors.forename: Jürgen
authors.initials: J
authors.lastname: May
authors.forename: Frank P
authors.initials: FP
authors.lastname: Mockenhaupt
mesh_terms: D000953:Antigens, Protozoan / Q000235:genetics; D000962:Antimalarials / Q000008:administration & dosage*; D018890:Chemoprevention / Q000379:methods*; D004338:Drug Combinations; D005260:Female; D005869:Ghana; D006801:Humans; D007223:Infant; D008288:Malaria / Q000469:parasitology* / Q000517:prevention & control*; D008297:Male; D020066:Merozoite Surface Protein 1 / Q000235:genetics; D010919:Placebos / Q000008:administration & dosage; D010963:Plasmodium falciparum / Q000145:classification* / Q000235:genetics / Q000302:isolation & purification*; D015800:Protozoan Proteins / Q000235:genetics; D011739:Pyrimethamine / Q000008:administration & dosage; D013413:Sulfadoxine / Q000008:administration & dosage; D016896:Treatment Outcome
chemical_list: D000953:Antigens, Protozoan; D000962:Antimalarials; D004338:Drug Combinations; D020066:Merozoite Surface Protein 1; D010919:Placebos; D015800:Protozoan Proteins; C065974:merozoite surface protein 2, Plasmodium; C001205:fanasil, pyrimethamine drug combination; D013413:Sulfadoxine; D011739:Pyrimethamine
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