Sickle cell trait is associated with controlled levels of haem and mild proinflammatory response during acute malaria infection

Abstract

The controlled induction of haemoxygenase-1 (HO-1), an enzyme that catabolizes haem, has been shown to reduce haem, preventing pathologies associated with haem toxicity. The hemoglobin genotype HbAS confers reduced susceptibility to severe complications of malaria by a mechanism that is not well understood. Using a longitudinal approach, we investigated the effect of baseline concentrations of HO-1 on the accumulation of haem during acute Plasmodium falciparum malaria in HbAS and HbAA genotypes. Plasma concentrations of haem, HO-1 and cytokines were quantified in venous blood obtained from children (9 months–5 years of age) during malaria infection, and at convalescence (baseline levels). Parasitaemia was determined during malaria infection. In patients with the HbAA genotype, there was a significant elevation in the plasma concentration of haem (P50.002), and a consequent increased induction of HO-1 (P<0.001) during falciparum malaria compared with levels at convalescence. Contrary to HbAA, plasma concentration of haem did not change in the HbAS genotypical group (P50 110), and the induction of HO-1 was reduced during malaria compared with levels at convalescence (P50 006). Higher plasma levels of haem were observed in HbAS compared with HbAA at convalescence (P50 010), but this difference did not affect the levels of HO-1 within each genotype (P50 450). Relatively milder proinflammatory responses were observed in HbAS children during malaria infection compared to HbAA children. Our findings suggest that a mechanism of reduced susceptibility to severe malaria pathologies by the HbAS genotype may involve the control of haem, leading to controlled levels of HO-1 and milder proinflammatory responses during acute malaria.