Current knowledge of the genetic basis of parasitemia levels and IgG levels is reviewed through key examples including the hemoglobinopathies, showing that the protective effect of HBB variants on malaria clinical phenotypes may partially be mediated through parasitemia and cytophilic IgG levels.
We replicated associations at HBB (P=.0008) and CD36 (P=.03) but also showed that the same variants are unusually differentiated in frequency between the Luo and Yoruba (who historically have been exposed to malaria) and the Masai and Kikuyu (who have not been exposed).
To test the model, we analyzed the relationships between the polymorphisms at the hemoglobin beta chain (HBB) and red cell glutathione peroxidase (GPX1) loci in 18 populations that had been subjected to endemic malaria (Cameroon and Central African Republic).
We find no evidence of the major deleterious mutations at HBB (beta-globin) and G6PD in chimpanzees that confer resistance to malaria caused by P. falciparum nor evidence of long-term balancing selection at these loci.
We examine variants in HBB that have been shown to be protective against malaria and test whether these are associated with the transmission of the parasite from the human host to the Anopheles vector.
It is hypothesized that repeat units or alleles of microsatellites TH01 and D5S818, located in close proximity to beta-globin gene and immune regulatory region in human play a role in malaria predisposition.
Indeed it is known that sickle-cell trait, beta-thalassemia trait, glucose-6-phosphate dehydrogenase (G6PD)- deficiency and iron deficiency confer some protection against a severe course of malaria.
Hemoglobin, serum ferritin (SF), serum soluble transferrin receptor (sTfR), serum C-reactive protein (CRP), serum α1-acid glycoprotein (AGP), and malaria antigens were measured at inclusion and after supplementation.
Here, our main objective was to study the changes in MSP2-specific total IgG, IgG1 and IgG3 responses during a malaria transmission season in order to assess the impact of sickle-cell, α(+)-thalassemia and G6PD variants on antibody kinetics.
Plasmodium vivax radical cure requires the use of primaquine (PQ), a drug that induces haemolysis in glucose-6-phosphate dehydrogenase deficient (G6PDd) individuals, which further hampers malaria control efforts.
Another example is the IgG receptor FcγRIIa, encoded by FCGR2A, such that H131 homozygotes displayed higher IgG2 levels and were protective against high parasitemia and onset of malaria symptoms as shown in a causal diagram.
Inducible nitric oxide synthase 2 (NOS2 -954 G>C; rs 1800482) heterozygosity was associated with lower incidence of malaria in all age groups {Adjusted incident rates ratio (aIRR) 0.59; 95% CI [0.386-0.887]; P = 0.012)}.
The lack of evidence for selection across the malaria eradication time may be explained by other factors, including somatic cell selection or misclassification of heterozygotes women as G6PD normal in the older birth cohorts.
The presence of the A- variant alongside other G6PD mutants and the patchy distribution of G6PDd indicate that larger studies specifically designed to unravel the distribution of G6PDd at small geographical scale may be needed to tailor malaria elimination efforts in Ethiopia to the local context.