Expression of the iron hormone hepcidin distinguishes different types of anemia in African children.

Childhood anemia is a major global health problem resulting from multiple causes. Iron supplementation addresses iron deficiency anemia but is undesirable for other types of anemia and may exacerbate infections. The peptide hormone hepcidin governs iron absorption; hepcidin transcription is mediated by iron, inflammation, and erythropoietic signals. However, the behavior of hepcidin in populations where anemia is prevalent is not well established. We show that hepcidin measurements in 1313 African children from The Gambia and Tanzania (samples taken in 2001 and 2008, respectively) could be used to identify iron deficiency anemia. A retrospective secondary analysis of published data from 25 Gambian children with either postmalarial or nonmalarial anemia demonstrated that hepcidin measurements identified individuals who incorporated >20% oral iron into their erythrocytes. Modeling showed that this sensitivity of hepcidin expression at the population level could potentially enable simple groupings of individuals with anemia into iron-responsive and non-iron-responsive subtypes and hence could guide iron supplementation for those who would most benefit.

Randomised controlled trial of weekly chloroquine to re-establish normal erythron iron flux and haemoglobin recovery in postmalarial anaemia.

OBJECTIVE: To determine if low-dose weekly chloroquine (CQ) therapy improves recovery from malaria-associated anaemia. DESIGN: Proof of concept randomised clinical trial. SETTING: West Kiang District, Lower River Region, The Gambia. PARTICIPANTS: Children resident in participating communities, aged 12-72 months, with uncomplicated malaria identified using active case detection over two consecutive malaria transmission seasons. INTERVENTIONS: In 2007, eligible children were randomised to chloroquine-sulfadoxine/pyrimethamine (CQ-SP) or co-artemether (ACT) antimalarial therapy, and after parasite clearance on day 3 were subsequently re-randomised (double-blind) to weekly low-dose CQ (5 mg/kg) or placebo. In 2008, all eligible children were treated with ACT and subsequently randomised to CQ or placebo. OUTCOME MEASURES: The primary outcome was a change in haemoglobin from baseline (day 3 of antimalarial treatment) to day 90 in the CQ and placebo treatment arms. Secondary outcomes were changes in urinary neopterin as a marker of macrophage activation, markers of erythropoietic response and prevalence of submicroscopic parasitaemia. Change in haemoglobin in the placebo arm by initial antimalarial treatment was also assessed. RESULTS: In 2007, 101 children with uncomplicated malaria were randomised to antimalarial treatment with CQ-SP or ACT and 65 were subsequently randomised to weekly CQ or placebo. In 2008, all children received ACT antimalarial treatment and 31 were subsequently randomised to receive weekly CQ or placebo. Follow-up to day 90 was 96%. There was no effect of weekly CQ vs placebo on change in haemoglobin at day 90 (CQ+10.04 g/L (95% CI 6.66 to 13.42) vs placebo +7.61 g/L (95% CI 2.88 to 12.35)). There was no effect on the secondary outcomes assessed, or effect of initial antimalarial therapy on haemoglobin recovery. Higher day 90 haemoglobin correlated independently with older age, not being stunted, higher haemoglobin at day 0 and adequate iron status at day 3. CONCLUSIONS: Weekly low-dose CQ after effective antimalarial treatment is not effective in improving recovery from postmalarial anaemia. TRIAL REGISTRATION: The clinical trial registration number is NCT00473837 (ClinicalTrials.gov).

Hepcidin is the major predictor of erythrocyte iron incorporation in anemic African children.

Iron supplementation strategies in the developing world remain controversial because of fears of exacerbating prevalent infectious diseases. Understanding the conditions in which iron will be absorbed and incorporated into erythrocytes is therefore important. We studied Gambian children with either postmalarial or nonmalarial anemia, who were given oral iron supplements daily for 30 days. Supplements administered on days 1 and 15 contained the stable iron isotopes (57)Fe and (58)Fe, respectively, and erythrocyte incorporation was measured in blood samples drawn 14 days later. We investigated how the iron-regulatory hormone hepcidin and other inflammatory/iron-related indices, all measured on the day of isotope administration, correlated with erythrocyte iron incorporation. In univariate analyses, hepcidin, ferritin, C-reactive protein, and soluble transferrin receptor (sTfR) strongly predicted incorporation of (57)Fe given on day 1, while hepcidin, ferritin, and sTfR/log ferritin correlated with (58)Fe incorporation. In a final multivariate model, the most consistent predictor of erythrocyte isotope incorporation was hepcidin. We conclude that under conditions of competing signals (anemia, iron deficiency, and infection), hepcidin powerfully controls use of dietary iron. We suggest that low-cost point-of-care hepcidin assays would aid iron supplementation programs in the developing world.

Haptoglobin and sickle cell polymorphisms and risk of active trachoma in Gambian children.

BACKGROUND: Susceptibility and resistance to trachoma, the leading infectious cause of blindness, have been associated with a range of host genetic factors. In vitro studies of the causative organism, Chlamydia trachomatis, demonstrate that iron availability regulates its growth, suggesting that host genes involved in regulating iron status and/or availability may modulate the risk of trachoma. The objective was to investigate whether haptoglobin (Hp) haplotypes constructed from the functional polymorphism (Hp1/Hp2) plus the functional promoter SNPs -61A-C (rs5471) and -101C-G (rs5470), or sickle cell trait (HbAS, rs334) were associated with risk of active trachoma when stratified by age and sex, in rural Gambian children. METHODOLOGY AND PRINCIPAL FINDINGS: In two cross sectional surveys of children aged 6-78 months (n = 836), the prevalence of the clinical signs of active trachoma was 21.4%. Within boys, haplotype E (-101G, -61A, Hp1), containing the variant allele of the -101C-G promoter SNP, was associated with a two-fold increased risk of active trachoma (OR = 2.0 [1.17-3.44]). Within girls, an opposite association was non-significant (OR = 0.58 [0.32-1.04]; P = 0.07) and the interaction by sex was statistically significant (P = 0.001). There was no association between trachoma and HbAS. CONCLUSIONS: These data indicate that genetic variation in Hp may affect susceptibility to active trachoma differentially by sex in The Gambia.

Iron delocalisation in the pathogenesis of malarial anaemia.

There is consensus that the pathophysiology of malaria-associated anaemia is multifactorial, but the precise mechanisms behind many of the haematological changes during malaria remain unclear. In this review, we attempt to build a composite picture of the pathophysiology of malarial anaemia using evidence from experimental, human and animal studies. We propose that cytokine- and hepcidin-mediated iron delocalisation, a principal mechanism in the anaemia of inflammation, plays an important role in the aetiology of malarial anaemia, and can explain some of the clinical and laboratory findings. These mechanisms interact with other aetiological determinants, such as dietary iron and micronutrient supply, helminth load, other infections and genetic variation, in determining the severity and associated features of anaemia. We suggest that iron delocalisation as a mechanism for malarial anaemia could be exploited for the development of alternative therapeutic strategies for post-malaria anaemia.

Iron incorporation and post-malaria anaemia.

BACKGROUND: Iron supplementation is employed to treat post-malarial anaemia in environments where iron deficiency is common. Malaria induces an intense inflammatory reaction that stalls reticulo-endothelial macrophagal iron recycling from haemolysed red blood cells and inhibits oral iron absorption, but the magnitude and duration of these effects are unclear. METHODOLOGY/PRINCIPAL FINDINGS: We examined the red blood cell incorporation of oral administered stable isotopes of iron and compared incorporation between age matched 18 to 36 months old children with either anaemia post-malaria (n = 37) or presumed iron deficiency anaemia alone (n = 36). All children were supplemented for 30 days with 2 mg/kg elemental iron as liquid iron sulphate and administered (57)Fe and (58)Fe on days 1 and 15 of supplementation respectively. (57)Fe and(58)Fe incorporation were significantly reduced (8% vs. 28%: p<0.001 and 14% vs. 26%: p = 0.045) in the malaria vs. non-malaria groups. There was a significantly greater haemoglobin response in the malaria group at both day 15 (p = 0.001) and 30 (p<0.000) with a regression analysis estimated greater change in haemoglobin of 7.2 g/l (s.e. 2.0) and 10.1 g/l (s.e. 2.5) respectively. CONCLUSION/SIGNIFICANCE: Post-malaria anaemia is associated with a better haemoglobin recovery despite a significant depressant effect on oral iron incorporation which may indicate that early erythropoetic iron need is met by iron recycling rather than oral iron. Supplemental iron administration is of questionable utility within 2 weeks of clinical malaria in children with mild or moderate anaemia.

Haptoglobin genotype, anaemia and malaria in Gambian children.

OBJECTIVE: To retest our previous finding that the haptoglobin (Hp) 22 genotype is associated with seasonal anaemia, and to investigate the role of malaria in this effect. METHODS: Haemoglobin (Hb) and peripheral parasitaemia were assessed at pre- and post-malarial season cross-sectional surveys in rural Gambian children aged 10-72 months. Between the surveys, active longitudinal surveillance was conducted to detect febrile episodes. RESULTS: Unlike previously, no overall reduction in Hb was observed (Hb = 106.1 vs. 107.2 g/l, P = 0.13, n = 545). However, multi-variable linear regression revealed differences in Hb over the season by Hp and Hb-sickle (HbS) genotype (-2.20 g/l per copy of the Hp2 allele, P = 0.043; HbAS vs. HbAA + 3.13 g/l, P = 0.11, n = 536). There was no effect of malarial episodes during follow-up; this suggests that when effective treatment is given, Hb levels recover. The A61-C Hp promoter SNP, associated with the Hp2 allele, had no effect. CONCLUSION: The effect of the Hp2 allele appears to be independent of effects on malaria incidence but may affect Hb levels through increased oxidant stress and red cell turnover. This may be supported by our previous observations that the effect of Hp22 was independent of markers of iron status and zinc protoporphyrin measured at the cross-sectional surveys and therefore also of iron availability for erythropoiesis.

Effectiveness of an early supplementation scheme of high-dose vitamin A versus standard WHO protocol in Gambian mothers and infants: a randomised controlled trial.

BACKGROUND: Most developing countries have adopted a standard WHO dosing schedule for vitamin A supplementation. However, in 2002 the International Vitamin A Consultative Group (IVACG) Annecy Accord recommended a new high-dose regimen for mothers and infants. Our aim was to test whether the new high-dose regimen of vitamin A supplementation would increase maternal and infant plasma vitamin A, reduce infant Helicobacter pylori infection and nasopharyngeal pneumococcal carriage, and improve infant gut epithelial integrity. METHODS: In an area of moderate vitamin A deficiency in rural Gambia, 220 mother-infant pairs were enrolled in a randomised double-blind trial between September, 2001, and October, 2004, that compared the IVACG high dose with the WHO dose. The primary endpoints were levels of maternal and infant plasma vitamin A, H pylori infection, pneumococcal carriage, and gut epithelial integrity. The trial is registered as ISRCTN 98554309. FINDINGS: 197 infants completed follow-up to 12 months (99 high dose and 98 WHO dose). There were no adverse events at dosing. No differences were found in the primary outcomes for high-dose versus WHO schedule: maternal vitamin A concentration at 2 months +0.02 micromol/L (95% CI -0.10 to 0.15); infant vitamin A at 5 months +0.01 micromol/L (-0.06 to 0.08); H pylori infection at 12 months -0.3% (-14.7 to 14.2); maternal pneumococcal carriage at 12 months -2.0% (-13.7 to 9.7); infant pneumococcal carriage at 12 months -4.1% (-15.8 to 7.6); infant gut mucosal damage at 12 months 5.2% (-8.7 to 19.2). There were more clinic attendances by the high-dose group in the first 6 months of life (p=0.018). INTERPRETATION: Our results do not lend support to the proposal to increase the existing WHO standard dosing schedule for vitamin A in areas of moderate vitamin A deficiency. Caution is urged for future studies because trials have shown possible adverse effects of higher doses of vitamin A, and potential negative interactions with the expanded programme on immunisation (EPI) vaccines.

Host-pathogen interactions: the role of iron.

Iron is essential for both host and pathogen, and complex systems of acquisition and utilization have evolved in competition. Our increasing knowledge of the basic mechanisms of homeostasis and their adaptation during deficiency, overload, and infection indicate that iron is a key regulator of host pathogen interactions. This review concentrated on the clinical and public health aspects of the interaction between the iron acquisition mechanisms of select pathogens of public health importance with host iron homeostasis. Knowledge of these interactions is essential in assessing likely morbidity responses to supplementation.

Evaluation of 13C-urea breath test and fecal antigen immunoassay to detect Helicobacter pylori infection in Gambian infants.

Helicobacter pylori colonization was measured by [13C]-urea breath test in 198 Gambian infants and by fecal enzyme-linked immunosorbent assay in 52 of the 198 at ages 2, 5, and 12 months. By 12 months there was good concordance between tests; 33 of 44 (75%) test results were positive by enzyme-linked immunosorbent assay, and 29 of 44 (66%) test results were positive by urea breath test. H. pylori colonization is common among Gambian infants, and noninvasive tests can provide a reliable means of diagnosis.