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

Abstract 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

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

Abstract 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

Correction: Kinetics of antibody responses to PfRH5-complex antigens in Ghanaian children with Plasmodium falciparum malaria.

[This corrects the article DOI: 10.1371/journal.pone.0198371.]

Kinetics of antibody responses to PfRH5-complex antigens in Ghanaian children with Plasmodium falciparum malaria.

Plasmodium falciparum PfRH5 protein binds Ripr, CyRPA and Pf113 to form a complex that is essential for merozoite invasion of erythrocytes. The inter-genomic conservation of the PfRH5 complex proteins makes them attractive blood stage vaccine candidates. However, little is known about how antibodies to PfRH5, CyRPA and Pf113 are acquired and maintained in naturally exposed populations, and the role of PfRH5 complex proteins in naturally acquired immunity. To provide such data, we studied 206 Ghanaian children between the ages of 1-12 years, who were symptomatic, asymptomatic or aparasitemic and healthy. Plasma levels of antigen-specific IgG and IgG subclasses were measured by ELISA at several time points during acute disease and convalescence. On the day of admission with acute P. falciparum malaria, the prevalence of antibodies to PfRH5-complex proteins was low compared to other merozoite antigens (EBA175, GLURP-R0 and GLURP-R2). At convalescence, the levels of RH5-complex-specific IgG were reduced, with the decay of PfRH5-specific IgG being slower than the decay of IgG specific for CyRPA and Pf113. No correlation between IgG levels and protection against P. falciparum malaria was observed for any of the PfRH5 complex proteins. From this we conclude that specific IgG was induced against proteins from the PfRH5-complex during acute P. falciparum malaria, but the prevalence was low and the IgG levels decayed rapidly after treatment. These data indicate that the levels of IgG specific for PfRH5-complex proteins in natural infections in Ghanaian children were markers of recent exposure only

Acquisition and decay of IgM and IgG responses to merozoite antigens after <i>Plasmodium falciparum</i> malaria in Ghanaian children

Developing a vaccine against Plasmodium falciparum malaria has been challenging, primarily due to high levels of antigen polymorphism and a complex parasite lifecycle. Immunization with the P. falciparum merozoite antigens PfMSRP5, PfSERA9, PfRAMA, PfCyRPA and PfRH5 has been shown to give rise to growth inhibitory and synergistic antisera. Therefore, these five merozoite proteins are considered to be promising candidates for a second-generation multivalent malaria vaccine. Nevertheless, little is known about IgG and IgM responses to these antigens in populations that are naturally exposed to P. falciparum. In this study, serum samples from clinically immune adults and malaria exposed children from Ghana were studied to compare levels of IgG and IgM specific for PfMSRP5, PfSERA9, PfRAMA, PfCyRPA and PfRH5. All five antigens were found to be specifically recognized by both IgM and IgG in serum from clinically immune adults and from children with malaria. Longitudinal analysis of the latter group showed an early, transient IgM response that was followed by IgG, which peaked 14 days after the initial diagnosis. IgG levels and parasitemia did not correlate, whereas parasitemia was weakly positively correlated with IgM levels. These findings show that IgG and IgM specific for merozoite antigens PfMSRP5, PfSERA9, PfRAMA, PfCyRPA and PfRH5 are high in children during P. falciparum malaria, but that the IgM induction and decline occurs earlier in infection than that of IgG

Merozoite-specific IgG in acutely ill <i>P</i>. <i>falciparum</i> malaria patients.

<p>A: Prevalences (proportions of donors with specific IgG levels above the negative cut-off) and their 95% confidence intervals (error bars) of merozoite-specific IgG in plasma of individual children with acute P. falciparum malaria. B: Levels of merozoite antigen-specific IgG in plasma, expressed as fold arbitrary units (AU) of the negative cut-off AU value for each antigen (indicated by the shaded area). Medians (center lines), central 50% (boxes), central 80% (bars), and outliers (dots) are indicated. C: Proportion of IgG-positive donors with detectable IgG subclass response to PfRH5 (left), CyRPA (center), and Pf113 (right). Proportions and corresponding 95% confidence intervals of IgG1 (white), IgG2 (black), IgG3 (gray), and IgG4 (dark gray) are shown. The presented data is from one experiment.</p

Clinical characteristics of study participants.

<p>Clinical characteristics of study participants.</p

Kinetics of merozoite-specific IgG levels following episodes of <i>P</i>. <i>falciparum</i> malaria.

<p>Plasma levels of IgG specific for PfRH5 (A, D), CyRPA (B, E), and Pf113 (C, F) in children with P. falciparum malaria (Day 0), and in the same children two weeks (Day 14) and six weeks (Day 42) later. Temporal changes in levels of IgG in individual children (A-C) and in the cohort mean IgG level (D-F). Data from individual children are connected by lines (A-C). Cohort running means (heavy lines) and their 95% confidence intervals (thin lines), calculated as described previously [<a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0198371#pone.0198371.ref034" target="_blank">34</a>], as well as calculated catabolic decay from Day 14 (dashed lines) are shown (D-F). Negative cut-offs (shaded areas) are shown (all panels). The presented data is from one experiment.</p