Innate and Acquired Resistance to Plasmodium Falciparum Malaria in Mali

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).

• INCLUSION CRITERIA:

(Cohort Study)

• Resident of Kenieroba, Fourda, or Bozokin villages, and no plans to relocate away from the study village for the next 5 years.
• Willingness to participate in the study as evidenced by informed consent of parents or guardians of children, and willingness to bring children to study clinic if they develop fever or other symptoms of malaria.
• Age 6 months to 17 years.

(Blood Collection Study)

• Children enrolled in the cohort study.
• Willingness to participate in the study as evidenced by informed consent of parents or guardians of children.
• Age 2 years to 14 years.
• Hemoglobin level greater than or equal to 8.5g/dL.

(Parasite Clearance Study)

• Children enrolled in the cohort study.
• Willingness to participate in the study as evidenced by informed consent of parents or guardians of children.
• Age 1 year to 17 years (inclusive).
• P. falciparum density greater than or equal to 10,000/microL.
• Present with their first episode of uncomplicated malaria of the 2010 transmission season or any episode during the 2012 transmission season.
• Resident of Kenieroba

(Adult blood Collection Study)

• Willingness to participate in the study as evidenced by informed consent.
• Age 18 years to 65 years.
• Hemoglobin level greater than or equal to 8.5 g/dL

Exclusion criteria

(Cohort Study)

• Any condition that in the opinion of the investigator would render the subject unable to comply with the protocol (e.g., psychiatric disease).
• Any health condition that in the opinion of the investigator would confound data analysis or pose unnecessary exposure risks to study personnel (e.g., individuals who are known to be HIV-infected or to have AIDS) or to the child (e.g., severe malnutrition).

(Blood Collection Study)

• Any condition that in the opinion of the investigator would render the subject unable to comply with the protocol (e.g., psychiatric disease).
• Any health condition that in the opinion of the investigator would confound data analysis or pose unnecessary exposure risks to study personnel (e.g., individuals who are known to be HIV-infected or to have AIDS) or to the child (e.g., severe malnutrition).

(Parasite Clearance Study)

• Any condition that in the opinion of the investigator would render the subject unable to comply with the protocol (e.g., psychiatric diesase).
• Any health condition that in the opinion of the investigator would confound data analysis or pose unnecessary exposure risks to study personnel (e.g., individuals who are known to be HIV-infected or to have AIDS) or to the child (e.g., severe malnutrition).
• Pregnancy at the time of malaria episode.

(Adult Blood Collection Study)

• Any condition that in the opinion of the investigator would render the subject unable to comply with the protocol (e.g., psychiatric disease)
• Any health condition that in the opinion of the investigator would confound data analysis or pose unnecessary exposure risks to study personnel (e.g., individuals who are known to be HIV-infected or to have AIDS.