Cellular iron governs the host response to malaria.

Malaria and iron deficiency are major global health problems with extensive epidemiological overlap. Iron deficiency-induced anaemia can protect the host from malaria by limiting parasite growth. On the other hand, iron deficiency can significantly disrupt immune cell function. However, the impact of host cell iron scarcity beyond anaemia remains elusive in malaria. To address this, we employed a transgenic mouse model carrying a mutation in the transferrin receptor (TfrcY20H/Y20H), which limits the ability of cells to internalise iron from plasma. At homeostasis TfrcY20H/Y20H mice appear healthy and are not anaemic. However, TfrcY20H/Y20H mice infected with Plasmodium chabaudi chabaudi AS showed significantly higher peak parasitaemia and body weight loss. We found that TfrcY20H/Y20H mice displayed a similar trajectory of malaria-induced anaemia as wild-type mice, and elevated circulating iron did not increase peak parasitaemia. Instead, P. chabaudi infected TfrcY20H/Y20H mice had an impaired innate and adaptive immune response, marked by decreased cell proliferation and cytokine production. Moreover, we demonstrated that these immune cell impairments were cell-intrinsic, as ex vivo iron supplementation fully recovered CD4+ T cell and B cell function. Despite the inhibited immune response and increased parasitaemia, TfrcY20H/Y20H mice displayed mitigated liver damage, characterised by decreased parasite sequestration in the liver and an attenuated hepatic immune response. Together, these results show that host cell iron scarcity inhibits the immune response but prevents excessive hepatic tissue damage during malaria infection. These divergent effects shed light on the role of iron in the complex balance between protection and pathology in malaria.

Increased Plasmodium chabaudi malaria mortality in mice with nutritional iron deficiency can be reduced by short-term adjunctive iron supplementation.

BACKGROUND: Iron deficiency is the most widespread nutrient deficiency and an important cause of developmental impairment in children. However, some studies have indicated that iron deficiency can also protect against malaria, which is a leading cause of childhood morbidity and mortality in large parts of the world. This has rendered interventions against iron deficiency in malaria-endemic areas controversial. METHODS: The effect of nutritional iron deficiency on the clinical outcome of Plasmodium chabaudi AS infection in A/J mice and the impact of intravenous iron supplementation with ferric carboxymaltose were studied before and after parasite infection. Plasma levels of the iron status markers hepcidin and fibroblast growth factor 23 were measured in animals surviving and succumbing to malaria, and accompanying tissue pathology in the liver and the spleen was assessed. RESULTS: Nutritional iron deficiency was associated with increased mortality from P. chabaudi malaria. This increased mortality could be partially offset by carefully timed, short-duration adjunctive iron supplementation. Moribund animals were characterized by low levels of hepcidin and high levels of fibroblast growth factor 23. All infected mice had extramedullary splenic haematopoiesis, and iron-supplemented mice had visually detectable intracellular iron stores. CONCLUSIONS: Blood transfusions are the only currently available means to correct severe anaemia in children with malaria. The potential of carefully timed, short-duration adjunctive iron supplementation as a safe alternative should be considered.

In vivo assessment of the antimalarial and spleen-protective activities of the Saudi propolis methanolic extract.

Antimalarial drug resistance is the main therapeutic challenge to the control of the disease, making the search for new compounds as alternative treatments of central importance. Propolis has a long history of medicinal use due to its antifungal, antibacterial and antiprotozoal properties. The present study therefore aimed to evaluate the antimalarial activity of the Saudi propolis methanolic extract against Plasmodium chabaudi infection in mice. To this end, albino mice were divided into five groups: the first group was the normal control; the second, third, fourth and fifth groups were infected intraperitoneally with 106 P. chabaudi-parasitized erythrocytes. The last three groups of mice were gavaged with 100 µl of propolis extract (PE) at a dose of 25, 50 and 100 mg PE/kg, respectively, once daily for 7 days. PE significantly suppressed the parasitaemia and showed significant efficacy in ameliorating anaemic conditions in P. chabaudi-infected mice in a dose-dependent manner. Histological investigation of the spleen tissue of treated and untreated mice further supports the antimalarial potential of PE. In addition, our study proved that Saudi PE reduced oxidative damage by decreasing the malondialdehyde (MDA) and increasing the catalase (CAT) activity and the glutathione (GSH) levels. Also, Saudi PE increased the level of some pro-inflammatory cytokines such as IFN-γ, TNF-α, GM-CSF and G-CSF, with the most effective dose being 100 mg PE/kg. In conclusion, PE showed antimalarial and antioxidant activities and provided protection against spleen tissue damage in P. chabaudi-infected mice.

Erythrocytic Iron Deficiency Enhances Susceptibility to Plasmodium chabaudi Infection in Mice Carrying a Missense Mutation in Transferrin Receptor 1.

The treatment of iron deficiency in areas of high malaria transmission is complicated by evidence which suggests that iron deficiency anemia protects against malaria, while iron supplementation increases malaria risk. Iron deficiency anemia results in an array of pathologies, including reduced systemic iron bioavailability and abnormal erythrocyte physiology; however, the mechanisms by which these pathologies influence malaria infection are not well defined. In the present study, the response to malaria infection was examined in a mutant mouse line, Tfrc(MRI24910), identified during an N-ethyl-N-nitrosourea (ENU) screen. This line carries a missense mutation in the gene for transferrin receptor 1 (TFR1). Heterozygous mice exhibited reduced erythrocyte volume and density, a phenotype consistent with dietary iron deficiency anemia. However, unlike the case in dietary deficiency, the erythrocyte half-life, mean corpuscular hemoglobin concentration, and intraerythrocytic ferritin content were unchanged. Systemic iron bioavailability was also unchanged, indicating that this mutation results in erythrocytic iron deficiency without significantly altering overall iron homeostasis. When infected with the rodent malaria parasite Plasmodium chabaudi adami, mice displayed increased parasitemia and succumbed to infection more quickly than their wild-type littermates. Transfusion of fluorescently labeled erythrocytes into malaria parasite-infected mice demonstrated an erythrocyte-autonomous enhanced survival of parasites within mutant erythrocytes. Together, these results indicate that TFR1 deficiency alters erythrocyte physiology in a way that is similar to dietary iron deficiency anemia, albeit to a lesser degree, and that this promotes intraerythrocytic parasite survival and an increased susceptibility to malaria in mice. These findings may have implications for the management of iron deficiency in the context of malaria.

Discovery of carbohybrid-based 2-aminopyrimidine analogues as a new class of rapid-acting antimalarial agents using image-based cytological profiling assay.

New antimalarial agents that exhibit multistage activities against drug-resistant strains of malaria parasites represent good starting points for developing next-generation antimalarial therapies. To facilitate the progression of such agents into the development phase, we developed an image-based parasitological screening method for defining drug effects on different asexual life cycle stages of Plasmodium falciparum. High-throughput screening of a newly assembled diversity-oriented synthetic library using this approach led to the identification of carbohybrid-based 2-aminopyrimidine compounds with fast-acting growth inhibitory activities against three laboratory strains of multidrug-resistant P. falciparum. Our structure-activity relationship study led to the identification of two derivatives (8aA and 11aA) as the most promising antimalarial candidates (mean EC50 of 0.130 and 0.096 µM against all three P. falciparum strains, selectivity indices >600, microsomal stabilities >80%, and mouse malaria ED50 values of 0.32 and 0.12 mg/kg/day, respectively), targeting all major blood stages of multidrug-resistant P. falciparum parasites.