Innate and Acquired Resistance to Plasmodium Falciparum Malaria in Mali
Condition: Malaria
MeSH terms: Malaria; Malaria, Falciparum
Study type: Observational

Summary: 
      This study, sponsored by NIAID and the University of Bamako, Mali, will identify genetic and
      other factors that may protect against severe malaria in some children.

      Children between 6 months and 17 years of age who live in Kenieroba, Fourda or Bozokin
      villages in Mali may enroll in the study. Participants have a blood sample collected by
      finger prick with a small needle. The blood is examined for gene variants that influence the
      severity of disease in children exposed to the malaria parasite.

      Children who develop a fever or other symptoms of malaria are evaluated and treated in
      Kenieroba s health center for up to 5 years from entering the study, or until they reach 18
      years of age. The children are treated with artesunate and amodiaquine. Children with severe
      disease are treated with quinine. One tablespoon of blood is drawn from the children for
      study.

      At the end of the dry season and the wet season, a subset of 200 healthy children are asked
      to provide 1 or 2 tablespoons of blood, drawn through a needle placed in a vein in the arm.
      Additional research blood samples may be requested from children between 2 and 17 years old.
      Blood will not be taken from any child more than twice a year.

      ...
    

Detailed description: 
      Hemoglobin (Hb) and red blood cell (RBC) polymorphisms that give rise to HbS, HbC,
      alpha-thalassemia, G6PD-deficiency, and ABO blood groups occur at high frequency in Mali. To
      determine whether these Hb/RBC polymorphisms are associated with protection against mild
      malaria and malaria-associated anemia, we will conduct a cohort study in Mali. Approximately
      1300 children will be genotyped for five Hb/RBC polymorphisms and followed for 5 years to
      compare mean incidence rates for mild malaria, stratified by polymorphism. Differences
      between Hb levels during acute malaria episodes and at baseline will be calculated to
      determine if Hb/RBC polymorphisms influence the degree of malaria-associated anemia. To
      investigate whether Hb/RBC polymorphisms impair monocyte activation, we will obtain parasites
      from children with malaria, culture them in RBCs of different genotype, and compare the
      parasitized RBCs for their ability to activate monocytes in vitro. Plasma samples from
      children with malaria will also be compared for their levels of monocyte-derived cytokines. A
      variety of single nucleotide polymorphisms (SNPs) in immune response genes have recently been
      identified in African populations. To determine whether these polymorphisms are associated
      with protection against severe malaria, we will compare the prevalence of SNPs in groups of
      children with severe or mild malaria. Blood Collection Study. Components of the innate immune
      system (e.g., Toll-like receptors) expressed on antigen presenting cells (APC) provide the
      first line of defense against microbial infection and frame the nature and scale of adaptive
      immune responses. To investigate whether APC from malaria-experienced individuals respond to
      TLR ligands in vitro stimulation assays, we will obtain blood samples from 100 healthy
      children in the dry season and again in the wet season. Immunological memory is a key feature
      of adaptive immunity and involves memory T cells. Clinical trials in which malaria-nafve
      human volunteers were vaccinated with merozoite MSP-1 antigens enabled us to study the
      development of immunological memory by measuring memory T cell cytokine production and
      expression of surface activation markers. To investigate whether memory T cells from
      malaria-experienced individuals respond similarly to AMA-I/MSP-1 ligands in vitro stimulation
      assays, we will obtain blood samples from an additional 100 healthy children in the dry
      season and again in the wet season. These collections of paired samples will enable us to
      explore the possibility that TLR- and AMA-1/MSP-l-induced immune responses are boosted during
      a transmission season and increase with age (a surrogate for disease controlling immunity).
    

Time perspective: Prospective
Keywords: Innate Immunity; Malaria; Plasmodium; Hemoglobinopathy; G6PD Deficiency