α-thalassemia impairs the cytoadherence of plasmodium falciparum-infected erythrocytes

Michael A. Krause, Seidina A.S. Diakite, Tatiana M. Lopera-Mesa, Chanaki Amaratunga, Takayuki Arie, Karim Traore, Saibou Doumbia, Drissa Konate, Jeffrey R. Keefer, Mahamadou Diakite, Rick M. Fairhurst

Research output: Contribution to journalArticlepeer-review

Abstract

Background: α-thalassemia results from decreased production of α-globin chains that make up part of hemoglobin tetramers (Hb; α2β2) and affects up to 50% of individuals in some regions of sub-Saharan Africa. Heterozygous (-α/αα) and homozygous (-α/-α) genotypes are associated with reduced risk of severe Plasmodium falciparum malaria, but the mechanism of this protection remains obscure. We hypothesized that α-thalassemia impairs the adherence of parasitized red blood cells (RBCs) to microvascular endothelial cells (MVECs) and monocytes - two interactions that are centrally involved in the pathogenesis of severe disease. Methods and Findings: We obtained P. falciparum isolates directly from Malian children with malaria and used them to infect αα/αα (normal), -α/αα and -α/-α RBCs. We also used laboratory-adapted P. falciparum clones to infect -/-α RBCs obtained from patients with HbH disease. Following a single cycle of parasite invasion and maturation to the trophozoite stage, we tested the ability of parasitized RBCs to bind MVECs and monocytes. Compared to parasitized αα/αα RBCs, we found that parasitized -α/αα, -α/-α and -/-α RBCs showed, respectively, 22%, 43% and 63% reductions in binding to MVECs and 13%, 33% and 63% reductions in binding to monocytes. α-thalassemia was associated with abnormal display of P. falciparum erythrocyte membrane protein 1 (PfEMP1), the parasite's main cytoadherence ligand and virulence factor, on the surface of parasitized RBCs. Conclusions: Parasitized α-thalassemic RBCs show PfEMP1 display abnormalities that are reminiscent of those on the surface of parasitized sickle HbS and HbC RBCs. Our data suggest a model of malaria protection in which α-thalassemia ameliorates the pro-inflammatory effects of cytoadherence. Our findings also raise the possibility that other unstable hemoglobins such as HbE and unpaired α-globin chains (in the case of β-thalassemia) protect against life-threatening malaria by a similar mechanism.

Original languageEnglish (US)
Article numbere37214
JournalPloS one
Volume7
Issue number5
DOIs
StatePublished - May 18 2012

ASJC Scopus subject areas

  • Biochemistry, Genetics and Molecular Biology(all)
  • Agricultural and Biological Sciences(all)
  • General

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