Impact of Seasonal Malaria Chemoprevention on Immunity Against Malaria Among Children in Northern Benin
Condition: Plasmodium Malariae Infection; SMC; Immune System Disease
MeSH terms: Malaria; Immune System Diseases
Study type: Observational [Patient Registry]

Summary: 
      This study aims to evaluate the effects of SMC (Seasonal malaria chemoprevention) with
      Sulfadoxine-Pyrimethamine (SP) and Amodiaquine (AQ) on the evolution of anti-malarial
      immunity of children and their susceptibility to malarial infection.

      This is a cross-sectional study on children aged 6 to 59 months with/without SMC in two
      villages in northern Benin. Sociodemographic and clinical data as well as repeated blood
      samples will be collected from 440 children (before, during and after treatment). Samples
      will be analyzed using a Luminex assay to investigate antibody responses to MSP (merozoite
      surface protein) , Glurp (Glutamate-Rich Protein) and a panel of PfEMP1. qPCR (quantitative
      polymerase chain reaction) will be used to detect the prevalence of malaria at this period
      and parasites infecting children will be characterize during the follow up.
    

Detailed description: 
      Study location and population The study was conducted in parallel in two different sites, the
      health districts of Cobly and Tchaourou (two villages) located in northern Benin. These two
      districts have been chosen based on the Ministry of Health's programming for the
      implementation of SMC. The two sites were very similar in terms of malaria transmission
      characteristics and epidemiology, with the difference that SMC was implemented in Cobly but
      not in Tchaourou. Participants will be informed on the importance of SMC. A written informed
      consent was collected from parent or guardian of each child. Participation was entirely
      voluntary.

      Study Design and procedures This is a case control study focuses on the follow-up over 12
      months of children aged 6 to 59 months in northern Benin. The study was conducted in
      collaboration with National Malaria Control Program (NMCP). Demographic data generated by the
      NMCP had allow us for a random selection of children from random households. In both
      intervention and control sites, equal numbers of children were included. The study team
      visited each selected household to inform members. A monthly visit has been set up for
      monitoring. Children of consenting parents or guardians were recruited and parents/guardians
      were taken through a questionnaire administered by the researcher or an assistant
      (clinician). 1 ml of peripheral venous blood was collected into collection tubes and
      transferred to the Center for Expertise and Enhancing Research in Epidemiology and Public
      Health (CEEREPH) at the University of Parakou where a blood smear was prepared from each
      sample. Fifty microliters of blood have been transferred to Whatman 3MM filter paper and
      stored at room temperature for DNA extraction. The remaining whole blood have been
      centrifuged. The plasma and red blood cells were aliquoted. Samples was collected at 4 times
      during the 12 months follow-up period. The first samples were collected at the beginning of
      SMC implimentation (before children receive the first SMC dose), the second blood sample were
      collected at the day of the third dose of SMC, the third, at three month after the last dose
      of SMC and the fourth, six months after the last dose of SMC).

      Malaria prevalence Thick and thin blood smears whave been prepared from all samples at all
      four times. Thick smears will be fixed in methanol. All slides were air dried and stained
      using Giemsa stain 3% for 45-60 min. Once dry, the stained thick and thin blood films were
      examined microscopically using a routine procedure. Parasite densities was recorded as the
      number of parasites/μl of blood assuming an average leukocyte count of 8,000/μl of blood.
      Dried blood spots were air dried and stored individually in small Ziploc bags with a
      desiccant. Plasmodium spp detection was performed using a real time polymerase chain reaction
      (qPCR).

      Anti-PfEMP1 antibody response Plasmodium falciparum-encoded variant surface antigens (VSA)
      are expressed on the surface of infected erythrocytes (IE) and mediate binding to a range of
      endothelial cell receptors. The best characterized VSA are the var gene-encoded P. falciparum
      erythrocyte membrane protein 1 (PfEMP1) family in two exon units. Exon I codes for the
      extracellular and variable part of the protein as well as a transmembrane region and Exon II
      encodes the intracellular and relatively conserved acidic terminal segment (ATS). The most
      variable part of the protein contains a N-terminal segment followed by segments composed of
      three domain types; Duffy binding-like domains (DBL-domains): Cysteine-rich inter-domain
      regions (CIDRs) and C2. In this study, a panel of plasma antibody was quantified using
      microsphere bead-coupled proteins comprising 28 P. falciparum-derived antigens and tetanus
      toxoid, using the Luminex platform. The panel includes VAR2CSA (the VSA associated to
      placental malaria) and 25 HIS-tagged CIDR proteins representing all three main groups of
      PfEMP1, merozoite surface protein 1 (MSP1) and apical membrane antigen 1 (AMA1).
    

Intervention name(s): saisonal malaria chimoprevention
Intervention type(s): Drug
Intervention description(s): Investigate the impact of saisonal malaria chimoprevention on children anti PfEMP1 construction and maintenance and their succeptibility to malaria infection
Observational model: Case-Control
Time perspective: Other
Sampling method: Probability Sample
Study population: 
        Children who meet the inclusion and exclusion criteria, living in the communes of Cobly and
        Tchaourou located in northern Benin, whether or not they have received Saisonal malaria
        chimotreatment, will be recruited.
      
Keywords: Seasonal malaria chemoprevention; Malaria; Children; Anti PfEMP1