Cytokine mRNA expression and iron status in children living in a malaria endemic area

Impact of Malnutrition on Serum Levels of Pro-inflammatory Cytokines among Plasmodium falciparum Malaria Subjects in Nigeria

BACKGROUND

Understanding the impact of malnutrition on innate immune response in Plasmodium falciparum (Pf)-infected subjects is critical for malaria control.

AIMS AND OBJECTIVES

This study aims to investigate the nutritional status and innate immune response of Pf-infected subjects in Lagos, Nigeria.

MATERIALS AND METHODS

A total of 1183 patients with a history of fever or axillary temperature ≥37°C were screened microscopically for Pf at Ijede General Hospital, Lagos, Nigeria. Malnutrition was determined according to the U.S National Center for Health Statistics (NCHS) as stunting, wasting, or underweight when the Z-score is <-2 in the participants aged <20 years. Serum levels of tumor necrosis factor-alpha (TNF-α), interleukin-1β (IL-1β), and IL-12 were determined by capture ELISA while hematological parameters were measured using an automated hematology system.

RESULTS

A total of 384 volunteers were positive for Pf, of which 114 were <20 years with a median age of 10 years. Overall malaria prevalence was 20.89%. The malnutrition rate was 89.5%; 24 (21.05%) were stunted, 30 (26.32%) were underweight, and 48 (42.11%) were wasted. Pro-inflammatory cytokine responses were not affected by the type of malaria. TNF-α was higher in participants <5 years (P = 0.001) and in malnourished patients (P < 0.05).

CONCLUSION

Together, it could be deduced that nutritional status influences Plasmodium falciparum malaria outcomes and progression pattern.

Nutrition in chronic inflammatory conditions: Bypassing the mucosal block for micronutrients

Nutritional Immunity is one of the most ancient innate immune responses, during which the body can restrict nutrients availability to pathogens and restricts their uptake by the gut mucosa (mucosal block). Though this can be a beneficial strategy during infection, it also is associated with non-communicable diseases-where the pathogen is missing; leading to increased morbidity and mortality as micronutritional uptake and distribution in the body is hindered. Here, we discuss the acute immune response in respect to nutrients, the opposing nutritional demands of regulatory and inflammatory cells and particularly focus on some nutrients linked with inflammation such as iron, vitamins A, Bs, C, and other antioxidants. We propose that while the absorption of certain micronutrients is hindered during inflammation, the dietary lymph path remains available. As such, several clinical trials investigated the role of the lymphatic system during protein absorption, following a ketogenic diet and an increased intake of antioxidants, vitamins, and minerals, in reducing inflammation and ameliorating disease.

Multifunctional IgG/IgM antibodies and cellular cytotoxicity are elicited by the full-length MSP1 SumayaVac-1 malaria vaccine

Radical control of malaria likely requires a vaccine that targets both the asymptomatic liver stages and the disease-causing blood stages of the human malaria parasite Plasmodium falciparum. While substantial progress has been made towards liver stage vaccines, the development of a blood stage vaccine is lagging behind. We have recently conducted a first-in-human clinical trial to evaluate the safety and immunogenicity of the recombinant, full-length merozoite surface protein 1 (MSP1FL) formulated with GLA-SE as adjuvant. Here, we show that the vaccine, termed SumayaVac-1, elicited both a humoral and cellular immune response as well as a recall T cell memory. The induced IgG and IgM antibodies were able to stimulate various Fc-mediated effector mechanisms associated with protection against malaria, including phagocytosis, release of reactive oxygen species, production of IFN-γ as well as complement activation and fixation. The multifunctional activity of the humoral immune response remained for at least 6 months after vaccination and was comparable to that of naturally acquired anti-MSP1 antibodies from semi-immune adults from Kenya. We further present evidence of SumayaVac-1 eliciting a recallable cellular cytotoxicity by IFN-γ producing CD8+ T cells. Our study revitalizes MSP1FL as a relevant blood stage vaccine candidate and warrants further evaluation of SumayaVac-1 in a phase II efficacy trial.

Nutritional Provision of Iron Complexes by the Major Allergen Alt a 1 to Human Immune Cells Decreases Its Presentation

Alternaria alternata is a common fungus strongly related with severe allergic asthma, with 80% of affected individuals being sensitized solely to its major allergen Alt a 1. Here, we assessed the function of Alt a 1 as an innate defense protein binding to micronutrients, such as iron-quercetin complexes (FeQ2), and its impact on antigen presentation in vitro. Binding of Alt a 1 to FeQ2 was determined in docking calculations. Recombinant Alt a 1 was generated, and binding ability, as well as secondary and quaternary structure, assessed by UV-VIS, CD, and DLS spectroscopy. Proteolytic functions were determined by casein and gelatine zymography. Uptake of empty apo- or ligand-filled holoAlt a 1 were assessed in human monocytic THP1 cells under the presence of dynamin and clathrin-inhibitors, activation of the Arylhydrocarbon receptor (AhR) using the human reporter cellline AZ-AHR. Human PBMCs were stimulated and assessed for phenotypic changes in monocytes by flow cytometry. Alt a 1 bound strongly to FeQ2 as a tetramer with calculated Kd values reaching pico-molar levels and surpassing affinities to quercetin alone by a factor of 5000 for the tetramer. apoAlt a 1 but not holoAlta 1 showed low enzymatic activity against casein as a hexamer and gelatin as a trimer. Uptake of apo- and holo-Alt a 1 occurred partly clathrin-dependent, with apoAlt a 1 decreasing labile iron in THP1 cells and holoAlt a 1 facilitating quercetin-dependent AhR activation. In human PBMCs uptake of holoAlt a 1 but not apoAlt a 1 significantly decreased the surface expression of the costimulatory CD86, but also of HLADR, thereby reducing effective antigen presentation. We show here for the first time that the presence of nutritional iron complexes, such as FeQ2, significantly alters the function of Alt a 1 and dampens the human immune response, thereby supporting the notion that Alt a 1 only becomes immunogenic under nutritional deprivation.

Lack of iron, zinc, and vitamins as a contributor to the etiology of atopic diseases

Micronutritional deficiencies are common in atopic children suffering from atopic dermatitis, food allergy, rhinitis, and asthma. A lack of iron, in particular, may impact immune activation with prolonged deficiencies of iron, zinc, vitamin A, and vitamin D associated with a Th2 signature, maturation of macrophages and dendritic cells (DCs), and the generation of IgE antibodies. In contrast, the sufficiency of these micronutrients establishes immune resilience, promotion of regulatory cells, and tolerance induction. As micronutritional deficiencies mimic an infection, the body's innate response is to limit access to these nutrients and also impede their dietary uptake. Here, we summarize our current understanding of the physiological function of iron, zinc, and vitamins A and D in relation to immune cells and the clinical consequences of deficiencies in these important nutrients, especially in the perinatal period. Improved dietary uptake of iron is achieved by vitamin C, vitamin A, and whey compounds, whereas zinc bioavailability improves through citrates and proteins. The addition of oil is essential for the dietary uptake of beta-carotene and vitamin D. As for vitamin D, the major source comes via sun exposure and only a small amount is consumed via diet, which should be factored into clinical nutritional studies. We summarize the prevalence of micronutritional deficiencies of iron, zinc, and vitamins in the pediatric population as well as nutritional intervention studies on atopic diseases with whole food, food components, and micronutrients. Dietary uptake via the lymphatic route seems promising and is associated with a lower atopy risk and symptom amelioration. This review provides useful information for clinical studies and concludes/emphasizes that a healthy, varied diet containing dairy products, fish, nuts, fruits, and vegetables as well as supplementing foods or supplementation with micronutrients as needed is essential to combat the atopic march.

Binding to Iron Quercetin Complexes Increases the Antioxidant Capacity of the Major Birch Pollen Allergen Bet v 1 and Reduces Its Allergenicity

Bet v 1 is the major allergen in birch pollen to which up to 95% of patients sensitized to birch respond. As a member of the pathogenesis-related PR 10 family, its natural function is implicated in plant defense, with a member of the PR10 family being reported to be upregulated under iron deficiency. As such, we assessed the function of Bet v 1 to sequester iron and its immunomodulatory properties on human immune cells. Binding of Bet v 1 to iron quercetin complexes FeQ2 was determined in docking calculations and by spectroscopy. Serum IgE-binding to Bet v 1 with (holoBet v1) and without ligands (apoBet v 1) were assessed by ELISA, blocking experiments and Western Blot. Crosslinking-capacity of apo/holoBet v 1 were assessed on human mast cells and Arylhydrocarbon receptor (AhR) activation with the human reporter cellline AZ-AHR. Human PBMCs were stimulated and assessed for labile iron and phenotypic changes by flow cytometry. Bet v 1 bound to FeQ2 strongly with calculated Kd values of 1 nm surpassing affinities to quercetin alone nearly by a factor of 1000. Binding to FeQ2 masked IgE epitopes and decreased IgE binding up to 80% and impaired degranulation of sensitized human mast cells. Bet v 1 facilitated the shuttling of quercetin, which activated the anti-inflammatory AhR pathway and increased the labile iron pool of human monocytic cells. The increase of labile iron was associated with an anti-inflammatory phenotype in CD14+monocytes and downregulation of HLADR. To summarize, we reveal for the first time that FeQ2 binding reduces the allergenicity of Bet v 1 due to ligand masking, but also actively contributes anti-inflammatory stimuli to human monocytes, thereby fostering tolerance. Nourishing immune cells with complex iron may thus represent a promising antigen-independent immunotherapeutic approach to improve efficacy in allergen immunotherapy.

Iron-Deficiency in Atopic Diseases: Innate Immune Priming by Allergens and Siderophores

Although iron is one of the most abundant elements on earth, about a third of the world's population are affected by iron deficiency. Main drivers of iron deficiency are beside the chronic lack of dietary iron, a hampered uptake machinery as a result of immune activation. Macrophages are the principal cells distributing iron in the human body with their iron restriction skewing these cells to a more pro-inflammatory state. Consequently, iron deficiency has a pronounced impact on immune cells, favoring Th2-cell survival, immunoglobulin class switching and primes mast cells for degranulation. Iron deficiency during pregnancy increases the risk of atopic diseases in children, while both children and adults with allergy are more likely to have anemia. In contrast, an improved iron status seems to protect against allergy development. Here, the most important interconnections between iron metabolism and allergies, the effect of iron deprivation on distinct immune cell types, as well as the pathophysiology in atopic diseases are summarized. Although the main focus will be humans, we also compare them with innate defense and iron sequestration strategies of microbes, given, particularly, attention to catechol-siderophores. Similarly, the defense and nutritional strategies in plants with their inducible systemic acquired resistance by salicylic acid, which further leads to synthesis of flavonoids as well as pathogenesis-related proteins, will be elaborated as both are very important for understanding the etiology of allergic diseases. Many allergens, such as lipocalins and the pathogenesis-related proteins, are able to bind iron and either deprive or supply iron to immune cells. Thus, a locally induced iron deficiency will result in immune activation and allergic sensitization. However, the same proteins such as the whey protein beta-lactoglobulin can also transport this precious micronutrient to the host immune cells (holoBLG) and hinder their activation, promoting tolerance and protecting against allergy. Since 2019, several clinical trials have also been conducted in allergic subjects using holoBLG as a food for special medical purposes, leading to a reduction in the allergic symptom burden. Supplementation with nutrient-carrying lipocalin proteins can circumvent the mucosal block and nourish selectively immune cells, therefore representing a new dietary and causative approach to compensate for functional iron deficiency in allergy sufferers.

Haemoglobin concentrations in pregnancy and respiratory and allergic outcomes in childhood: Birth cohort study

Background

Limited epidemiological evidence suggests that low maternal iron status and anaemia in pregnancy may increase the risk of childhood respiratory and allergic outcomes.

Objectives

To investigate the relation between maternal haemoglobin concentrations in pregnancy and childhood respiratory and allergic outcomes.

Methods

In the Avon Longitudinal Study of Parents and Children (ALSPAC), we examined associations of maternal haemoglobin concentrations (g/dL) in pregnancy with hayfever, eczema, wheezing, doctor‐diagnosed asthma, allergic sensitisation and total IgE at 7 years, and with lung function at 8‐9 years in the offspring, after controlling for potential confounders (N = 3234‐5335).

Results

Maternal haemoglobin was not associated with offspring hayfever, eczema, wheezing or asthma. However, the first haemoglobin measurement in pregnancy (<18 weeks' gestation) and the last measurement (>28 weeks' gestation) were negatively associated with allergic sensitisation (adjusted odds ratio [95% CI] per g/dL 0.91 [0.83 to 0.99] and 0.90 [0.83 to 0.98], respectively). The last haemoglobin measurement was also negatively associated with total IgE (adjusted geometric mean ratio 0.94 [0.88 to 0.99]). Anaemia (haemoglobin <11 g/dL) in late pregnancy was negatively associated with forced vital capacity (difference in standard deviation score −0.07 [−0.13 to −0.01]).

Conclusions and Clinical Relevance

Lower maternal haemoglobin in pregnancy may be a risk factor for allergic sensitisation, elevated IgE and lower FVC in childhood, which may reflect effects of lower prenatal iron status. However, maternal haemoglobin was not associated with risk of childhood asthma or other allergic disorders.

Asthma as a disruption in iron homeostasis

Over several decades, asthma has evolved from being recognized as a single disease to include a diverse group of phenotypes with dissimilar natural histories, pathophysiologies, responses to treatment, and distinctive molecular pathways. With the application of Occam's razor to asthma, it is proposed that there is one cause underlying the numerous phenotypes of this disease and that the responsible molecular pathway is a deficiency of iron in the lung tissues. This deficiency can be either absolute (e.g. asthma in the neonate and during both pregnancy and menstruation) or functional (e.g. asthma associated with infections, smoking, and obesity). Comparable associations between asthma co-morbidity (e.g. eczema, urticaria, restless leg syndrome, and pulmonary hypertension) with iron deficiency support such a shared mechanistic pathway. Therapies directed at asthma demonstrate a capacity to impact iron homeostasis, further strengthening the relationship. Finally, pathophysiologic events producing asthma, including inflammation, increases in Th2 cells, and muscle contraction, can correlate with iron availability. Recognition of a potential association between asthma and an absolute and/or functional iron deficiency suggests specific therapeutic interventions including inhaled iron.

Splenic architecture disruption and parasite-induced splenocyte activation and anergy in Plasmodium falciparum-infected Saimiri sciureus monkeys

Background

The understanding of the mechanisms of immunity in malaria is crucial for the rational development of interventions such as vaccines. During blood stage infection, the spleen is considered to play critical roles in both immunity and immunopathology of Plasmodium falciparum infections.

Methods

Saimiri sciureus monkeys were inoculated with blood stages of P. falciparum (FUP strain) and spleens removed during acute disease (days 7 and 13 of infection) and during convalescence (15 days after start of chloroquine treatment). Cytokine (IFNγ, TNFα, IL2, IL6, IL10, and IL12) responses of splenocytes stimulated with P. falciparum-parasitized red blood cells were assessed by real-time PCR using specific Saimiri primers, and histological changes were evaluated using haematoxylin-eosin and Giemsa-stained slides.

Results

Early during infection (day 7, 1-2% parasitaemia), spleens showed disruption of germinal centre architecture with heavy B-cell activation (centroblasts), and splenocytes showed increased expression of IFNγ, IL6 and IL12 upon in vitro stimuli by P. falciparum-parasitized red blood cells (pRBC). Conversely, 15 days after treatment of blood stage infection with chloroquine, splenocytes showed spontaneous in vitro expression of TNFα, IL2, IL6, IL10, and IL12, but not IFNγ, and stimulation with P. falciparum pRBC blocked the expression of all these cytokines. During the acute phase of infection, splenic disarray with disorganized germinal centres was observed. During convalescence, spleens of the chloroquine-treated animals showed white pulp hyperplasia with extensive lymphocyte activation and persistency of heavily haemozoin-laden macrophages throughout the red pulp.

Conclusions

Inability to eliminate haemozoin is likely involved in the persistent lymphocyte activation and in the anergic responses of Saimiri splenocytes to P. falciparum pRBC, with important negative impact in immune responses and implications for the design of malaria vaccine.

Implications of malaria on iron deficiency control strategies

The populations in greatest need of iron supplementation are also those at greatest risk of malaria: pregnant women and young children. Iron supplementation has been shown to increase malaria risk in these groups in numerous studies, although this effect is likely diminished by factors such as host immunity, host iron status, and effective malaria surveillance and control. Conversely, the risk of anemia is increased by malaria infections and preventive measures against malaria decrease anemia prevalence in susceptible populations without iron supplementation. Studies have shown that subjects with malaria experience diminished absorption of orally administered iron, so that as a consequence, iron supplementation may have generally reduced efficacy in malarious populations. A possible mechanistic link between malaria, poor absorption of iron, and anemia is provided by recent research on hepcidin, the human iron control hormone. Our improved understanding of iron metabolism may contribute to the control of malaria and the treatment of anemia. Malaria surveillance and control are necessary components of programs to control iron deficiency and may enhance the efficacy of iron supplementation.

Iron deficiency, but not underfeeding reduces the secretion of interferon-gamma by mitogen-activated murine spleen cells

Interferon-gamma (IFN-γ), a cytokine primarily secreted by T and natural killer cells regulates cell-mediated and innate immunity. Iron deficiency, a public health problem in children impairs immune function. To determine whether reduced IFN-γ contributes to impaired immunity, we measured IFN-γ in supernatants of activated (2.5 μg/ml concanavalin A, 50 ng/ml anti-CD3 antibody) spleen cells from control (C), iron-deficient (ID), pair-fed (PF), and iron-replete mice for 3 (R3) and 14 days (R14) (11-12/group). Except for iron content, the low iron (5 ppm) and control (50 ppm) diets had identical composition. Mean indices of iron status after 51 days of feeding were as follows: C=PF≈R14>R3>ID (p<0.01). Iron deficiency, but not pairfeeding reduced IFN-γ concentration in mitogen-treated cells by 30-43% (p<0.05); iron repletion improved it. Reduced IFN-γ was not simply due to differences in IL-12 (IFN-γ inducer), percentage of CD3+ T cells, or impaired cell proliferation because these indices were not always decreased. It was likely due to a defect in T cell activation that leads to IFN-γ gene expression. IFN-γ positively correlated with indicators of iron status, body, and thymus weights (r=0.238-0.472; p<0.05). Reduced IFN-γ secretion during iron deficiency may affect response to infections.

Effect of nutrient deficiencies on in vitro Th1 and Th2 cytokine response of peripheral blood mononuclear cells to Plasmodium falciparum infection

Background

An appropriate balance between pro-inflammatory and anti-inflammatory cytokines that mediate innate and adaptive immune responses is required for effective protection against human malaria and to avoid immunopathology. In malaria endemic countries, this immunological balance may be influenced by micronutrient deficiencies.

Methods

Peripheral blood mononuclear cells from Tanzanian preschool children were stimulated in vitro with Plasmodium falciparum-parasitized red blood cells to determine T-cell responses to malaria under different conditions of nutrient deficiencies and malaria status.

Results

The data obtained indicate that zinc deficiency is associated with an increase in TNF response by 37%; 95% CI: 14% to 118% and IFN-γ response by 74%; 95% CI: 24% to 297%. Magnesium deficiency, on the other hand, was associated with an increase in production of IL-13 by 80%; 95% CI: 31% to 371% and a reduction in IFN-γ production. These results reflect a shift in cytokine profile to a more type I cytokine profile and cell-cell mediated responses in zinc deficiency and a type II response in magnesium deficiency. The data also reveal a non-specific decrease in cytokine production in children due to iron deficiency anaemia that is largely associated with malaria infection status.

Conclusions

The pathological sequels of malaria potentially depend more on the balance between type I and type II cytokine responses than on absolute suppression of these cytokines and this balance may be influenced by a combination of micronutrient deficiencies and malaria status.

Iron metabolism and malaria

Recent evidence from a large, randomized, controlled trial has suggested that the universal administration of iron to children in malaria-endemic areas is associated with an increase in adverse health outcomes. The purpose of this paper is to summarize the available ecologic and intervention trials related to iron and malaria in children, and to set these against current knowledge of the biology of host-pathogen interactions involving iron metabolism. We conclude that, although not fully consistent, the balance of evidence confirms that administration of iron (usually in combination with folic acid) increases the incidence of malaria when given without prophylaxis and in the absence of universal access to treatment. The mechanisms by which additional iron can benefit the parasite are far from clear. There is evidence to suggest that the apparent detrimental effect of iron supplementation may vary according to levels of antecedent iron status, the presence of hemoglobinopathies and glucose-6-phosphate dehydrogenase (G6PD) deficiency, and other host genetic variants, such as variants in haptoglobin. The effects of malaria on host iron metabolism are also reviewed and reveal that the key cause of malaria-induced anemia is a maldistribution of iron and suppression of erythropoiesis rather than an exacerbation of gross iron deficiency. We tentatively conclude that, if it is to be recommended, universal iron supplementation in malarious areas should only be considered in conjunction with some form of prophylaxis (e.g., intermittent preventive therapy [IPT]) or in the context of good health services with ready access to facilities for malaria diagnosis and treatment. An alternative approach would be to screen for anemia and target supplementation only to anemic children. With regard to treatment, there is good evidence that iron supplementation should be withheld until the treatment schedule is complete, both because iron may inhibit treatment and because the absorption of oral iron is blocked by the inflammatory response.

Mechanism of iron toxicity

The subtle balance between proinflammatory and antiinflammatory cytokines plays an important role in determining the severity of the inflammatory reaction and in the anomalous iron handling associated with infection. Conversely, iron deficiency per se appears to limit the severity of the inflammatory response. All of these considerations are at present highly speculative and in need of further experimental and epidemiologic support. If confirmed, the beneficial biological effects of iron depletion may have a defensive role in inflammation and may be perturbed by the nonselective administration of iron to iron-replete patients who would not benefit from such treatment in the first place. In view of the importance of non-transferrin-bound plasma iron (NTBI) in iron toxicity and its rapid cellular uptake, it may play an important role in the harmful effects of iron in infection, and this is illustrated by the infectious complications of parenteral iron therapy in tropical countries.

Critical review of strategies to prevent and control iron deficiency in children

Iron deficiency is prevalent in infants and young children in developing countries and is associated with adverse developmental outcomes. The routine provision of additional iron by food fortification or the use of iron supplements is generally recommended. The wisdom of this approach in regions where the transmission of Plasmodium falciparum malaria is perennial and intense is now being questioned, because a large trial in Pemba, Tanzania, demonstrated an increased risk of serious morbidity among children under the age of 3 years who were given routine daily iron and folic acid supplements. However, the results of a concurrent substudy suggest that the untoward effects occurred in children who were not iron deficient, and that iron deficiency itself is associated with an increased risk of severe morbidity that can be reduced by iron and folic acid supplementation. There is an urgent need for additional research to confirm these observations, to establish the role, if any, of the concurrent folic acid supplementation, to evaluate the risk of alternative methods for delivering iron that, on theoretical grounds, could be safer, and to establish the programmatic feasibility of targeting iron fortificants or supplements to iron-deficient children. It is evident that a single strategy for ensuring adequate iron nutrition in young children in different parts of the world is no longer likely to be satisfactory. Moreover, integration with other health-related strategies, particularly malaria control programs, will be essential.

Elevated levels of interferon-gamma, interleukin-10, and interleukin-6 during active disease in Indian kala azar

We have evaluated levels of 6 cytokines in sera of 35 patients of kala azar (KA), 29 post kala azar dermal leishmaniasis (PKDL), and 18 healthy controls using cytometric bead array technology. Results indicated significantly high levels of interferon gamma (IFN-gamma), interleukin (IL)-10, and IL-6 during active KA, while tumor necrosis factor alpha (TNF-alpha), IL-2, and IL-4 were minimal. Serum level of cytokines in PKDL was comparable to the controls while TNF-alpha was significantly elevated compared to KA or control. At post-treatment stage, KA patients showed a significant decrement in the levels of IFN-gamma, IL-10, and IL-6; however, IL-6 remained significantly elevated above control levels. Further, comparison of cytokine levels in children and adults revealed elevated level of IL-10 in pediatric cases. SAG unresponsive cases showed significantly elevated levels of IFN-gamma in comparison with the responsive cases. The results depict that type1 response is not depressed during active KA and suggest the possibility that unresponsiveness to type1 stimuli may prevail.