IL-4 Treatment Mitigates Experimental Cerebral Malaria by Reducing Parasitemia, Dampening Inflammation, and Lessening the Cytotoxicity of T Cells.

Cytokine responses to malaria play important roles in both protective immunity development and pathogenesis. Although the roles of cytokines such as TNF-α, IL-12, IFN-γ, and IL-10 in immunity and pathogenesis to the blood stage malaria are largely known, the role of IL-4 remains less understood. IL-4 targets many cell types and induces multiple effects, including cell proliferation, gene expression, protection from apoptosis, and immune regulation. Accordingly, IL-4 has been exploited as a therapeutic for several inflammatory diseases. Malaria caused by Plasmodium falciparum manifests in many organ-specific fatal pathologies, including cerebral malaria (CM), driven by a high parasite load, leading to parasite sequestration in organs and consequent excessive inflammatory responses and endothelial damage. We investigated the therapeutic potential of IL-4 against fatal malaria in Plasmodium berghei ANKA-infected C57BL/6J mice, an experimental CM model. IL-4 treatment significantly reduced parasitemia, CM pathology, and mortality. The therapeutic effect of IL-4 is mediated through multiple mechanisms, including enhanced parasite clearance mediated by upregulation of phagocytic receptors and increased IgM production, and decreased brain inflammatory responses, including reduced chemokine (CXCL10) production, reduced chemokine receptor (CXCR3) and adhesion molecule (LFA-1) expression by T cells, and downregulation of cytotoxic T cell lytic potential. IL-4 treatment markedly reduced the infiltration of CD8+ T cells and brain pathology. STAT6, PI3K-Akt-NF-κB, and Src signaling mediated the cellular and molecular events that contributed to the IL-4-dependent decrease in parasitemia. Overall, our results provide mechanistic insights into how IL-4 treatment mitigates experimental CM and have implications in developing treatment strategies for organ-specific fatal malaria.

Brèves.

TITLE: Brèves. ABSTRACT: L'unité d'enseignement « Immunopathologie ¼ qui propose les brèves de ce numéro est suivie par des étudiants des sept parcours recherche du Master Biologie Santé de l'Université de Montpellier. On y étudie les bases physiopathologiques des maladies immunologiques, les cibles thérapeutiques et les mécanismes d'échappement des microorganismes et des tumeurs. Ce Master rassemble des étudiants issus du domaine des sciences et technologies et de celui de la santé. Les articles présentés ont été choisis par les étudiants selon leur domaine de prédilection.

Mesenchymal stromal cells protect against vascular damage and depression-like behavior in mice surviving cerebral malaria.

BACKGROUND: Malaria is one of the most critical global infectious diseases. Severe systemic inflammatory diseases, such as cerebral malaria, lead to the development of cognitive and behavioral alterations, such as learning disabilities and loss of memory capacity, as well as increased anxiety and depression. The consequences are profound and usually contribute to reduce the patient's quality of life. There are no therapies to treat the neurological sequelae of cerebral malaria. Mesenchymal stromal cells (MSCs) may be an alternative, since they have been used as therapy for neurodegenerative diseases and traumatic lesions of the central nervous system. So far, no study has investigated the effects of MSC therapy on the blood-brain barrier, leukocyte rolling and adherence in the brain, and depression like-behavior in experimental cerebral malaria. METHODS: Male C57BL/6 mice were infected with Plasmodium berghei ANKA (PbA, 1 × 106 PbA-parasitized red blood cells, intraperitoneally). At day 6, PbA-infected animals received chloroquine (25 mg/kg orally for seven consecutive days) as the antimalarial treatment and were then randomized to receive MSCs (1 × 105 cells in 0.05 ml of saline/mouse) or saline (0.05 ml) intravenously. Parasitemia, clinical score, and survival rate were analyzed throughout the experiments. Evans blue assay was performed at 6, 7, and 15 days post-infection (dpi). Behavioral tests were performed at 5 and 15 dpi. Intravital microscopy experiments and brain-derived neurotrophic factor (BDNF) protein expression analyses were performed at 7 dpi, whereas inflammatory mediators were measured at 15 dpi. In vitro, endothelial cells were used to evaluate the effects of conditioned media derived from MSCs (CMMSC) on cell viability by lactate dehydrogenase (LDH) release. RESULTS: PbA-infected mice presented increased parasitemia, adherent leukocytes, blood-brain barrier permeability, and reduced BDNF protein levels, as well as depression-like behavior. MSCs mitigated behavioral alterations, restored BDNF and transforming growth factor (TGF)-ß protein levels, and reduced blood-brain barrier dysfunction and leukocyte adhesion in the brain microvasculature. In a cultured endothelial cell line stimulated with heme, CMMSC reduced LDH release, suggesting a paracrine mechanism of action. CONCLUSION: A single dose of MSCs as adjuvant therapy protected against vascular damage and improved depression-like behavior in mice that survived experimental cerebral malaria.

HIV coinfection influences the inflammatory response but not the outcome of cerebral malaria in Malawian children.

OBJECTIVES: Study of the effect of HIV on disease progression in heterogeneous severe malaria syndromes with imprecise diagnostic criteria has led to varying results. Characteristic retinopathy refines cerebral malaria (CM) diagnosis, enabling more precise exploration of the hypothesis that HIV decreases the cytokine response in CM, leading to higher parasite density and a poor outcome. METHODS: We retrospectively reviewed data on clinical progression and laboratory parameters in 877 retinopathy-positive CM cases admitted 1996-2011 (14.4% HIV-infected) to a large hospital in Malawi. Admission plasma levels of TNF, interleukin-10, and soluble intercellular adhesion molecule (sICAM-1) were measured by ELISA in 135 retinopathy-positive CM cases. RESULTS: HIV-infected CM cases had lower median plasma levels of TNF (p = 0.008), interleukin-10 (p = 0.045) and sICAM-1 (p = 0.04) than HIV-uninfected cases. Although HIV-infected children were older and more likely to have co-morbidities, HIV-status did not significantly affect parasite density (p = 0.90) or outcome (24.8% infected, vs. 18.5% uninfected; p = 0.13). CONCLUSION: In this well-characterised CM cohort, HIV-coinfection was associated with marked blunting of the inflammatory response but did not affect parasite density or outcome. These data highlight the complex influence of HIV on severe malaria and bring into question systemic inflammation as a primary driver of pathogenesis in human CM.

Tropical Neuroinfectious Diseases.

PURPOSE OF REVIEW: This article discusses the assessment of the patient presenting with neurologic symptoms who has lived in or traveled through tropical or subtropical regions and reviews selected nervous system infections prevalent in the tropics and subtropics, with discussion of the epidemiology, clinical features, recommended diagnostic testing, and management. RECENT FINDINGS: Increasing travel, emigration, and population growth all facilitate the global spread of tropical neurologic infections. Neurologists worldwide should be aware of the spectrum of neurologic manifestations as well as the most appropriate approach to diagnosis and management of these infections. SUMMARY: Although many infectious tropical diseases affecting the nervous system are preventable or treatable, the burden of disease remains high, with significant socioeconomic costs associated with managing acute manifestations and chronic, often debilitating, neurologic sequelae. Tropical infections of the nervous system are often transmitted in regions where people live in poverty and where access to adequate health care is limited. As with most infections of the nervous system, timely access to proper treatment is of utmost importance, as delays are typically associated with worse outcome.

Mesenchymal stromal cell therapy attenuated lung and kidney injury but not brain damage in experimental cerebral malaria.

INTRODUCTION: Malaria is the most relevant parasitic disease worldwide, and still accounts for 1 million deaths each year. Since current antimalarial drugs are unable to prevent death in severe cases, new therapeutic strategies have been developed. Mesenchymal stromal cells (MSC) confer host resistance against malaria; however, thus far, no study has evaluated the therapeutic effects of MSC therapy on brain and distal organ damage in experimental cerebral malaria. METHODS: Forty C57BL/6 mice were injected intraperitoneally with 5 × 10(6) Plasmodium berghei-infected erythrocytes or saline. After 24 h, mice received saline or bone marrow (BM)-derived MSC (1x10(5)) intravenously and were housed individually in metabolic cages. After 4 days, lung and kidney morphofunction; cerebrum, spleen, and liver histology; and markers associated with inflammation, fibrogenesis, and epithelial and endothelial cell damage in lung tissue were analyzed. RESULTS: In P. berghei-infected mice, BM-MSCs: 1) reduced parasitemia and mortality; 2) increased phagocytic neutrophil content in brain, even though BM-MSCs did not affect the inflammatory process; 3) decreased malaria pigment detection in spleen, liver, and kidney; 4) reduced hepatocyte derangement, with an increased number of Kupffer cells; 5) decreased kidney damage, without effecting significant changes in serum creatinine levels or urinary flow; and 6) reduced neutrophil infiltration, interstitial edema, number of myofibroblasts within interstitial tissue, and collagen deposition in lungs, resulting in decreased lung static elastance. These morphological and functional changes were not associated with changes in levels of tumor necrosis factor-α, keratinocyte-derived chemokine (KC, a mouse analog of interleukin-8), or interferon-γ, which remained increased and similar to those of P. berghei animals treated with saline. BM-MSCs increased hepatocyte growth factor but decreased VEGF in the P. berghei group. CONCLUSIONS: BM-MSC treatment increased survival and reduced parasitemia and malaria pigment accumulation in spleen, liver, kidney, and lung, but not in brain. The two main organs associated with worse prognosis in malaria, lung and kidney, sustained less histological damage after BM-MSC therapy, with a more pronounced improvement in lung function.

Adjunctive management of malaria.

PURPOSE OF REVIEW: Artesunate treatment reduces mortality in severe malaria when compared with quinine. Nevertheless, severe malaria is associated with mortality rates between 1.4 and 9.5% after hospitalization. This review puts into context the recent developments in understanding the pathophysiology of malaria and how these may be reflected in renewed attempts at improving adjunct therapies. Identifying new adjunct approaches has been particularly difficult for severe malaria because most interventions have either caused harm or failed to confer benefit. RECENT FINDINGS: Imaging and postmortem findings in children with severe and cerebral malaria have given impetus to study new interventions that could be added to antimalarial treatment. Some pilot studies have (re)tested different approaches to improve complications of cerebral malaria such as the use of N-acetyl cysteine or mannitol. Fluids administration, blood transfusions and red cell exchanges in severe malaria are controversial and important areas that are also reviewed with new evidence. Other interventions such as measures to increase nitric oxide, manage acute renal failure or optimize artesunate dosing are discussed. SUMMARY: Outcomes with adjunct therapies for severe malaria have been poor, but as insights into pathophysiological processes are deepened it may be possible eventually to reduce mortality further.

Management of seizures in children with falciparum malaria.

Falciparum malaria is the most common cause of convulsions in children admitted to hospital in malaria endemic areas. Detection of convulsions requires close monitoring and one should be on the look out for signs of subtle convulsions. About a third of acute seizures in children with cerebral malaria, do not manifest as convulsions, but as changes in eye deviation, salivation and/or eye deviation. It is important to terminate convulsions lasting more than 5 min, since prolonged convulsions are associated with neurological deficits in survivors of children with severe malaria. Initial management should include putting the child into the left lateral position, checking the blood glucose and administering oxygen if hypoxic. The benzodiazepines, particularly diazepam, are used as the initial anticonvulsants. Phenobarbital and phenytoin are used as second-line treatments. Prompt and effective management of falciparum malaria associated convulsions may contribute to a better outcome in children with severe malaria.

Erythrocytapheresis for Plasmodium falciparum infection complicated by cerebral malaria and hyperparasitemia.

In malaria due to Plasmodium falciparum, life-threatening complications are in part related to the degree of parasitemia. Whole blood exchange and red blood cell exchange (RCE) have been used for the rapid removal of parasites from the circulation of patients with a high parasite load complicated by cerebral, pulmonary, and renal dysfunction. We have treated three 5-45-year-old patients with hyperparasitemia and end-organ dysfunction with red cell exchange by automated apheresis as an adjunct to specific anti-malarial chemotherapy. Parasitemia dropped more than 80% in all three patients immediately after the exchange, and all patients had an uneventful and full recovery. In combination with effective anti-malarial chemotherapy, apheresis RCE is a safe and rapid approach to treat complicated malaria due to P. falciparum.

[The new poor expatriates in the third world]. / Les nouveaux quart-mondains du tiers-monde.

This report describes four cases involving French expatriates who developed serious health problems while living destitute in Senegal. A 37-year-old man presented with embolism-like symptoms in relation with lung involvement due to spreading of untreated staphylococcal skin infection. A 64-year-old man was admitted for high output cardiac failure secondary to severe anemia caused by malnutrition. A 50-year-old man presented recurrent fever with loss of consciousness after successful treatment of neuromalaria and finally attributed to delirium tremens. A 25-year-old man was hospitalized with presumed meningoencephalitis that had been ongoing for two weeks. All four patients had been in Senegal for several months and had cut all ties to mainland France. Being jobless and homeless, they had been unable to obtain proper nutrition or medications. With minimal entry requirements and low-cost air travel, Senegal has been come a common sight-seeing destination and has developed a small but apparently growing population of destitute travelers. Alienation from the home community and resulting seclusion enhance clinical consequences and delay intervention by foreign service officials.

Treatment with recombinant human tumour necrosis factor-alpha reduces parasitaemia and prevents Plasmodium berghei K173-induced experimental cerebral malaria in mice.

The present study shows that treatment with recombinant human tumour necrosis factor-alpha (rhTNF-alpha) can suppress parasitaemia and prevents development of experimental cerebral malaria (ECM) in Plasmodium berghei K173-infected mice. Mice received rhTNF-alpha treatment either by subcutaneous injection of free or liposome-encapsulated rhTNF-alpha or sustained intraperitoneal administration of rhTNF-alpha given via mini-osmotic pumps. Low-dose treatment with a subcutaneous bolus injection of rhTNF-alpha protected against ECM when treatment was started on day 5 or 6 after infection. The same protective efficacy was obtained either by subcutaneous injection of liposome-encapsulated rhTNF-alpha or by sustained release from osmotic pumps, but in the latter case a 10-fold lower daily dose of rhTNF-alpha was sufficient. Treatment with rhTNF-alpha substantially suppressed parasitaemia in ECM-protected mice, but not in mice developing ECM. Thus, the rhTNF-alpha mediated suppression of parasitaemia is directly or indirectly involved in protection against ECM. Sustained delivery of rhTNF-alpha through osmotic pumps, but not by subcutaneous injection of liposome-encapsulated rhTNF-alpha, resulted in increased concentrations of soluble mouse TNF receptor R75 (sTNFR75) in plasma at day 9 after infection when non-treated mice die of ECM. Thus, protection against ECM is not directly correlated with the sTNFR75 concentrations at day 9 after infection.

Interleukin-10 modulates susceptibility in experimental cerebral malaria.

In this study, we examined the effects of interleukin-10 (IL-10) on the outcome of experimental cerebral malaria (CM), a lethal neurological syndrome that occurs in susceptible strains of mice after infection with Plasmodium berghei ANKA (PbA). Constitutive IL-10 mRNA levels were significantly higher in the spleen and brain of resistant animals. In vivo neutralization of endogenous IL-10 in CM-resistant mice induced the neurological syndrome in 35.7% of these mice, as opposed to 7.7% in controls. IL-10 inhibited PbA antigen-specific interferon-gamma (IFN-gamma) production in vitro but not tumour necrosis factor (TNF) serum levels in vivo. Susceptible mice, on the other hand, were significantly protected against CM when injected with recombinant IL-10. Overall, our findings suggest that IL-10 plays a protective role against experimental cerebral malaria.

The malarial fever response--pathogenesis, polymorphism and prospects for intervention.

It is estimated that over 200 million people each year suffer debilitating attacks of malarial fever, and roughly 2 million of these episodes are fatal. The fever is caused by tumour necrosis factor (TNF) and other pyrogenic cytokines that are released by the host immune system response to products of schizont rupture. TNF has anti-parasitic properties but excessive TNF production is thought to play an important role in the pathogenesis of cerebral malaria. This review summarizes recent attempts to achieve molecular characterization of the parasite components that stimulate the host TNF response, and to define the host and parasite factors that affect the level of TNF production. Of particular interest are host polymorphisms that may regulate TNF gene expression, and naturally acquired antibodies that prevent the parasite from inducing TNF, both of which correlate with the clinical severity of infection. Our understanding of these processes, which are potentially of considerable therapeutic relevance, remains very limited at both the molecular and the epidemiological level.

Neurobiology of cerebral malaria and African sleeping sickness.

This review is aimed at emphasizing the need for basic neuroscience research on two tropical diseases, malaria and sleeping sickness (African trypanosomiasis), that still represent major health problems and in which severe involvement of the nervous system is frequently the direct cause of death. The life cycles of the two parasites, the protozoan Plasmodium and Trypanosoma brucei, which are the causative agents of malaria and sleeping sickness, respectively, are briefly reviewed. The historical contribution to the pathogenesis and therapy of malaria by a renowned pioneer in neuroscience, Camillo Golgi, is pointed out. The different strategies for survival in the host by the intracellular Plasmodium and the extracellular African trypanosomes are summarized; such strategies include sites favorable for hiding or replication of the parasites in the host, antigenic variation, and interactions with the cytokine network of the host. In particular, tumor necrosis factor-alpha and interferon-gamma may play a role in these infections. The parasites may paradoxically interact with cytokines to their benefit. However, cytokine receptors are expressed on neuronal subsets sensitive to cytokine action, and stimulation of these subsets may cause neuronal dysfunctions during the infections. Finally, the clinical symptoms of cerebral malaria and African trypanosomiasis and research aiming at deciphering their pathogenetic mechanisms that could affect the nervous system at a molecular level are described. The need for neuroscientists in this endeavor is emphasized.

The effect of a monoclonal antibody to tumor necrosis factor on survival from childhood cerebral malaria.

Tumor necrosis factor (TNF) is thought to play a key role in the pathogenesis of cerebral malaria. A double-blind, placebo-controlled trial of an anti-TNF monoclonal antibody (B-C7) comprised 610 Gambian children with cerebral malaria, with mortality and residual neurologic sequelae as primary study end points. Sixty (19.9%) of 302 children who received B-C7 died compared with 64 (20.8%) of 308 children who received placebo (adjusted odds ratio [OR], 0.90; 95% confidence interval [CI], 0.57-1.42). Residual neurologic sequelae were detected in 15 (6.8%) of 221 survivors from the B-C7 group and in 5 (2.2%) of 225 survivors of the placebo group (adjusted OR, 3.35; 95% CI, 1.08-10.4). The monoclonal antibody used in this study did not improve survival in cerebral malaria and was associated with a significant increase in neurologic sequelae. A possible explanation of the latter observation is that the antibody acts to retain TNF within the circulation and thereby prolongs its effects on vascular endothelium.

Isolated pontine lesion in algid cerebral malaria: clinical features, management, and magnetic resonance imaging findings.

Malaria, the most important of all tropical diseases, causes approximately one million deaths per year. In Plasmodium falciparum malaria, the organs most affected are the brain, kidneys, lungs, and liver. Cerebral involvement is the most important lethal complication with a mortality rate of up to 50%. We report a patient with malignant, tertian falciparum malaria with an initial parasitemia rate of 60% and severe cerebral, hepatorenal, and pulmonary involvement. In addition to the severe diffuse encephalopathy, an initial neurologic examination showed signs of a pontine lesion that was confirmed by cerebral magnetic resonance imaging. We therefore conclude that cerebral malaria may be responsible for focal neurologic lesions that can be demonstrated by this procedure.

Intravenous immunoglobulin in the treatment of paediatric cerebral malaria.

Hyperimmune globulin can inhibit and reverse the cytoadherence between Plasmodium falciparum-infected erythrocytes and melanoma cells in vitro. Cytoadherence is believed to mediate disease in cerebral malaria. Therefore we studied the efficacy of i.v. immunoglobulin, purified from the plasma of local semi-immune blood donors, as an adjunct to standard treatment for cerebral malaria in Malawian children. The immunoglobulin preparation (IFAT antimalarial antibody titre 1:5120) recognized erythrocyte-associated antigens of each of 22 Malawian P. falciparum isolates studied, and reversed binding of Malawian isolates to melanoma cells. Immunoglobulin did not reverse binding to human monocytes or to cells of the human histiocytic lymphoma cell line U937. Thirty-one children with P. falciparum parasitaemia and unrousable coma were enrolled. All were treated with i.v. quinine dihydrochloride; in addition patients were randomized to receive either immunoglobulin (400 mg/kg by i.v. infusion over 3 h) or placebo (albumen and sucrose by similar infusion) in a double blind trial with sequential analysis. Of 16 patients receiving immunoglobulin, five (31%) died and five survivors had neurological sequelae. Of 15 patients receiving placebo, one (7%) died and two had sequelae. Parasite clearance, fever clearance and coma resolution times in survivors were similar in the two groups. Although the difference in outcome between the two groups was not significant, the trial was stopped because immunoglobulin was demonstrated not to be superior to placebo.

[Tumor necrosis factor during the course of neuromalaria: new therapeutic perspectives]. / Tumor necrosis factor au cours du neuropaludisme: nouvelles perspectives thérapeutiques.

Malaria remains one of the major public health problem in tropical and subtropical world. Malaria pathogeny depends partly on parasite multiplication and partly on some elements of the immunological response. It has recently become evident that one of these elements, Tumor Necrosis Factor (TNF), is directly implicated in the pathogenesis of cerebral malaria. TNF increase cytoadherence of infected erythrocytes to the brain microvascular endothelium. In a study involving african children with cerebral malaria high levels of TNF were positively correlated with a fatal outcome. We have previously demonstrated that in vitro Plasmodium falciparum products can directly stimulate the production of TNF from human macrophages. The aim of this work was to identify this soluble parasitic substance. Our results demonstrated that this substance could be a repetitive amino-acid sequence of the Ring-infected Erythrocyte Surface Antigen (RESA). The immunization against this kind of well-known peptides may be used as anti-disease vaccine. The elimination of mortality would be an essential target instead of parasitic clearance.