Malaria causes long-term effects on markers of iron status in children: a critical assessment of existing clinical and epidemiological tools.

BACKGROUND: Most epidemiological studies on the interplay between iron deficiency and malaria risk classify individuals as iron-deficient or iron-replete based on inflammation-dependent iron markers and adjustment for inflammation by using C-reactive protein (CRP) or α-1-acid glycoprotein (AGP). The validity of this approach and the usefulness of fibroblast growth factor 23 (FGF23) as a proposed inflammation-independent iron marker were tested. METHODS: Conventional iron markers and FGF23 were measured in children with acute falciparum malaria and after 1, 2, 4, and 6 weeks. Children, who were transfused or received iron supplementation in the follow-up period, were excluded, and iron stores were considered to be stable throughout. Ferritin levels 6 weeks after admission were used as a reference for admission iron status and compared with iron markers at different time points. RESULTS: There were long-term perturbations in iron markers during convalescence from acute malaria. None of the tested iron parameters, including FGF23, were independent of inflammation. CRP and AGP normalized faster than ferritin after malaria episodes. CONCLUSION: Malaria may bias epidemiological studies based on inflammation-dependent iron markers. Better markers of iron status during and after inflammation are needed in order to test strategies for iron supplementation in populations at risk of malaria.

Paleopathology and Paleomicrobiology of Malaria.

Malaria is a disease caused by parasites of the genus Plasmodium, transmitted through the bites of female anopheles flies. Plasmodium falciparum causes severe malaria with undulating high fever (malaria tropica). Literary evidence of malarial infection dates back to the early Greek period, when Hippocrates described the typical undulating fever highly suggestive of plasmodial infection. Recent immunological and molecular analyses describe the unambiguous identification of malarial infections in several ancient Egyptian mummies and a few isolated cases in Roman and Renaissance Europe. Although the numbers of cases are low, there is evidence that the overall infection rates may have been relatively high and that this infectious disease may have had a significant impact on historical populations.

A high-throughput assay for the identification of drugs against late-stage Plasmodium falciparum gametocytes.

Recent success in the global reduction campaign against malaria has resulted in the possibility that it may be feasible to drastically reduce or even eradicate malaria even without the introduction of a vaccine. However, while there has been significant effort to design the next generation of antimalarial drugs, one area that is underrepresented in the current antimalarial pharmacopeia is that of transmission blocking drugs directed at late-stage gametocytes. Here we describe the development of a robust and simple assay that is amenable to a high throughput format for the discovery of new antigametocyte drugs.

Assessment of urinary concentrations of hepcidin provides novel insight into disturbances in iron homeostasis during malarial infection.

Disturbances in iron homeostasis are frequently observed in individuals with malaria. To study the effect of malaria and its treatment on iron homeostasis and to provide a mechanistic explanation for observed alterations in iron distribution, we studied the course of the iron regulatory hormone hepcidin in anemic Tanzanian children with febrile Plasmodium falciparum malaria. Before initiation of antimalarial treatment, urinary concentrations of hepcidin were strongly elevated and were associated with iron maldistribution, as was suggested by the presence of hypoferremia and high serum concentrations of ferritin. Antimalarial treatment resulted in a rapid decrease in urinary concentrations of hepcidin and reversal of the hypoferremia. Exploration of regulatory pathways of hepcidin production by analysis of iron, erythropoietic, and inflammatory indices suggested that reduced erythropoietic activity and inflammation stimulated hepcidin production. We conclude that high concentrations of hepcidin explain the observed disturbances in host iron homeostasis associated with malaria and may contribute to malarial anemia and an impaired erythropoietic response to iron supplementation.

N-acetylcysteine as adjunctive treatment in severe malaria: a randomized, double-blinded placebo-controlled clinical trial.

OBJECTIVE: Markers of oxidative stress are reported to be increased in severe malaria. It has been suggested that the antioxidant N-acetylcysteine (NAC) may be beneficial in treatment. We studied the efficacy and safety of parenteral NAC as an adjunct to artesunate treatment of severe falciparum malaria. DESIGN: A randomized, double-blind, placebo-controlled trial on the use of high-dose intravenous NAC as adjunctive treatment to artesunate. SETTING: A provincial hospital in Western Thailand and a tertiary referral hospital in Chittagong, Bangladesh. PATIENTS: One hundred eight adult patients with severe falciparum malaria. INTERVENTIONS: Patients were randomized to receive NAC or placebo as an adjunctive treatment to intravenous artesunate. MEASUREMENTS AND MAIN RESULTS: A total of 56 patients were treated with NAC and 52 received placebo. NAC had no significant effect on mortality, lactate clearance times (p = 0.74), or coma recovery times (p = 0.46). Parasite clearance time was increased from 30 hours (range, 6-144 hours) to 36 hours (range, 6-120 hours) (p = 0.03), but this could be explained by differences in admission parasitemia. Urinary F2-isoprostane metabolites, measured as a marker of oxidative stress, were increased in severe malaria compared with patients with uncomplicated malaria and healthy volunteers. Admission red cell rigidity correlated with mortality, but did not improve with NAC. CONCLUSION: Systemic oxidative stress is increased in severe malaria. Treatment with NAC had no effect on outcome in patients with severe falciparum malaria in this setting.

Pharmacokinetics of L-arginine in adults with moderately severe malaria.

Severe malaria is associated with decreased nitric oxide (NO) production and low plasma concentrations of L-arginine, the substrate for NO synthase. Supplementation with L-arginine has the potential to improve NO bioavailability and outcomes. We developed a pharmacokinetic model for L-arginine in moderately severe malaria to explore the concentration-time profile and identify important covariates. In doses of 3, 6, or 12 g,L-arginine was infused over 30 min to 30 adults with moderately severe malaria, and plasma concentrations were measured at 8 to 11 time points. Patients who had not received L-arginine were also assessed and included in the model. The data were analyzed using a population approach with NONMEM software. A two-compartment linear model with first-order elimination best described the data, with a clearance of 44 liters/h (coefficient of variation [CV] = 52%) and a volume of distribution of 24 liters (CV = 19%). The natural time course of L-arginine recovery was described empirically by a second-order polynomial with a time to half recovery of 26 h. The half-life of exogenous L-arginine was reduced in patients with malaria compared with that for healthy adults. Weight and ethnicity were significant covariates for clearance. MATLAB simulations of dosing schedules for use in future studies predicted that 12 g given over 6, 8, or 12 h will provide concentrations above the K(m) of endothelial cell CAT-1 transporters in 90%, 75%, and 60% of patients, respectively.

Plasma zinc concentrations are depressed during the acute phase response in children with falciparum malaria.

Plasma concentrations of some micronutrients are altered in the setting of acute infectious or inflammatory stress. Previous studies have provided conflicting evidence concerning the extent and direction of changes in plasma zinc concentrations during the acute phase response. We carried out an observational cohort study in 689 children enrolled in a randomized trial of zinc supplementation during acute falciparum malaria in order to evaluate the relation between plasma zinc concentration and the acute phase response. Plasma zinc was measured by atomic absorption spectrophotometry. On admission, 70% of all subjects had low plasma zinc (<9.2 micromol/L). Multivariate analysis of predictors of admission plasma zinc showed that admission C-reactive protein (CRP), parasite density, and study site were the most important predictors. Predictors of changes in plasma zinc from admission to 72 h included baseline CRP, change in CRP, treatment group, study site, and baseline zinc concentration. In children with acute malaria infection, baseline plasma zinc concentrations were very low and were inversely correlated with CRP (r = -0.24, P < 0.0001) and the degree of parasitemia (r = -0.19, P < 0.0001). Even when CRP and time were taken into account, zinc supplementation increased plasma zinc concentration from admission to 72 h. When available, plasma zinc concentrations should be interpreted with concurrent measures of the acute phase response such as CRP. In children whose age, diet, and/or nutritional status place them at risk of zinc deficiency, those with low plasma zinc levels should be supplemented with oral zinc and followed for clinical and/or biochemical response.

Characterization of a unique aspartate-rich protein of the SET/TAF-family in the human malaria parasite, Plasmodium falciparum, which inhibits protein phosphatase 2A.

A search for physiological inhibitors of protein phosphatases led to the identification of a Plasmodium falciparum (Pf) cDNA that had the potential to code for an aspartate-rich protein and hence named ARP. The PfARP was virtually identical to its Plasmodium berghei counterpart in gene structure and protein sequence. The PfARP coding sequence contained two introns, and the predicted protein contained 269 amino acid residues. Its primary structure showed significant similarity to eukaryotic proteins of the SET and TAF-family that included two inhibitors of mammalian serine/threonine protein phosphatase 2A (PP2A), namely I1(PP2A) and I2(PP2A). Like the SET and TAF proteins, it had an extremely acidic tail. The cDNA was confirmed by recombinant expression in bacteria. Native parasitic ARP was purified and was found to be highly thermostable. PfARP specifically inhibited the parasitic PP2A at nanomolar concentrations, with no effect on PP1, PP2B, PP5, or PPJ. Expression of PfARP in HeLa cells led to elevated phosphorylation of c-Jun, and activation of transcription factors AP1 and NF-kappa B. These functional properties are also characteristic of the SET/TAF-family proteins. The ARP mRNA and protein were detectable in all the erythrocytic asexual stages of the parasite, and the protein was located mainly in the parasitic cytoplasm. Thus, PfARP is a unique cytoplasmic member of the SET/TAF-family and a candidate physiological regulator of the Plasmodium PP2A.

Therapy of uncomplicated falciparum malaria: a randomized trial comparing artesunate plus sulfadoxine-pyrimethamine versus sulfadoxine-pyrimethamine alone in Irian Jaya, Indonesia.

Combining artesunate with existing antimalarial drugs may improve cure rates, delay emergence of resistance, and reduce transmission. We performed a randomized comparative trial to quantify the effect of adding artesunate to sulfadoxine-pyrimethamine in the treatment of uncomplicated falciparum malaria in Indonesia. Using a modified 1997 World Health Organization protocol for assessment of therapeutic efficacy of antimalarial drugs, 105 patients (stratified by age/ethnic group) were randomized: 53 received artesunate orally, 4 mg/kg of body weight, a single daily dose for three days, plus sulfadoxine-pyrimethamine orally (1.25 mg of pyrimethamine/kg of body weight), a single dose on day 0, and 52 patients received sulfadoxine-pyrimethamine alone. Six from the combination group were withdrawn from analysis, as were six of the sulfadoxine-pyrimethamine group. Treatment failure rates on day 14 were 0% in the artesunate plus sulfadoxine-pyrimethamine group and 8.7% in the sulfadoxine-pyrimethamine group (P = 0.12). Treatment failure rates on day 28 were 4.4% and 15.2%, respectively (P = 0.16). Relative risk of treatment failure at 28 days was 0.3 (95% confidence interval [CI] = 0.1-1.3). Mean fever clearance time (1.3 versus 1.7 days) and mean parasite clearance time (1.4 versus 2.0 days) were both faster in the artesunate plus sulfadoxine-pyrimethamine group than in the sulfadoxine-pyrimethamine group (P = 0.08 and P < 0.0001, respectively). Only 20 (39.2%) of 51 patients treated with artesunate plus sulfadoxine-pyrimethamine were still parasitemic on day 1 compared with 45 (86.5%) of 52 patients treated with sulfadoxine-pyrimethamine alone (P = 0.000001, relative risk [RR] = 0.4, 95% CI = 0.3-0.6). Gametocyte carriage was lower following artesunate plus sulfadoxine-pyrimethamine than following sulfadoxine-pyrimethamine (RR = 0.5, 95% CI = 0.2-1.0 on day 7 and RR = 0.5, 95% CI = 0.2-1.1 on day 14). Mild diarrhea, rash, and itching resolved without treatment. Combined artesunate plus sulfadoxine-pyrimethamine resulted in more rapid fever and parasiteclearance, was well tolerated, reduced risk of treatment failure, and lowered gametocyte carriage.

A randomized, double-blind, parallel-group, comparative safety, and efficacy trial of oral co-artemether versus oral chloroquine in the treatment of acute uncomplicated Plasmodium falciparum malaria in adults in India.

In India, treatment of acute, uncomplicated Plasmodium falciparum malaria is becoming increasingly difficult due to resistance to chloroquine, thus there is a need for new antimalarial drugs. CGP 56697 (co-artemether), a new drug, is a combination of artemether and lumefantrine in a single oral formulation (one tablet = 20 mg of artemether plus 120 mg of lumefantrine). In a double-blind study, 179 patients with acute uncomplicated P. falciparum malaria were randomly assigned to receive either CGP (n = 89) given as a short course of 4 x 4 tablets over a 48-hr period or chloroquine (n = 90) given as four tablets (one tablet = 150 mg of chloroquine base) initially, followed by two tablets each at 6-8, 24, and 48 hr. Due to a death in the chloroquine group and a decrease in the chloroquine cure rate to < 50% (based on the blinded overall cure rate at that time), recruitment was terminated prematurely. CGP 56697 showed a superior 28-day cure rate (95.4% versus 19.7%; P < 0.001), time to parasite clearance (median = 36 versus 60 hr; P < 0.001), and resolution of fever (median = 18 versus 27 hr; P = 0.0456). This drug provides a safe, effective, and rapid therapy for the treatment of acute uncomplicated P. falciparum malaria.

Plasma levels of the interleukin-6 cytokine family in persons with severe Plasmodium falciparum malaria.

Plasma levels of interleukin (IL)-6, soluble IL-6 receptor, soluble gp130, leukemia inhibitory factor (LIF), and ciliary neutrophic factor (CNTF) were analyzed in 32 patients with severe malaria. Ten had renal failure, 8 had cerebral malaria, and 14 had other causes of severity. Before treatment, the IL-6 and soluble IL-6 receptor plasma levels were significantly higher in persons with cerebral malaria or renal failure than in other groups (P<.01 for both). After initiation of therapy, IL-6 levels dropped within 24 h, but soluble IL-6 receptor levels increased. CNTF levels were significantly reduced in persons with cerebral malaria or renal failure but normalized within 24 h. Plasma concentrations of gp130 and LIF did not differ between the malaria groups or normal controls. Excessive levels of IL-6 could be controlled by a subsequent shedding of the soluble IL-6 receptor, and low-level CNTF expression could contribute to or even result from cerebral malaria or renal failure.

Genetic and dietary adaptation to malaria in human populations.

Plasmodial invasion places a severe oxidant stress on parasitized erythrocytes which can result in red cell damage and removal within the reticuloendothelial system or lysis, thus interrupting the parasitic cycle. The basis of a number of genetic adaptations to malaria--including the hemoglobin variants, the thalassemias, and glucose-6-phosphate dehydrogenase deficiency--is an increased sensitivity of the variant erythrocytes to the oxidant stress of plasmodial parasitization. It is suggested that dietary adaptations of traditional cusines in human populations living in areas where malaria is endemic augment this oxidant stress. It appears that there are three components of this adaptive dietary pattern in most tropical populations: the consumption of 'oxidant fuels', moderate to high iron intake, and limitation of dietary antioxidant intake or storage. It is argued that this dietary pattern maximizes iron-mediated free radical production in parasitized erythrocytes and thus provides a form of diet-mediated antimalarial prophylaxis. African pastoral populations that are heavy consumers of milk appear to manifest a different adaptive pattern involving low intakes of para-aminobenzoic acid, vitamin E, and iron. Periodic food restriction may also contribute to this antimalarial effect.