Effects of anti-tau immunotherapy on reactive microgliosis, cerebral endotheliopathy, and cognitive function in an experimental model of cerebral malaria.

Cerebral malaria (CM), a potentially fatal encephalopathy caused primarily by infection with Plasmodium falciparum, results in long-term adverse neuro-psychiatric sequelae. Neural cell injury contributes to the neurological deficits observed in CM. Abnormal regulation of tau, an axonal protein pathologically associated with the formation of neurofibrillary lesions in neurodegenerative diseases, has been linked to inflammation and cerebral microvascular compromise and has been reported in human and experimental CM (ECM). Immunotherapy with a monoclonal antibody to pathological tau (PHF-1 mAB) in experimental models of neurodegenerative diseases has been reported to mitigate cognitive decline. We investigated whether immunotherapy with PHF-1 mAB prevented cerebral endotheliopathy, neural cell injury, and neuroinflammation during ECM. Using C57BL/6 mice infected with either Plasmodium berghei ANKA (PbA), which causes ECM, Plasmodium berghei NK65 (PbN), which causes severe malaria, but not ECM, or uninfected mice (Un), we demonstrated that when compared to PbN infection or uninfected mice, PbA infection resulted in significant memory impairment at 6 days post-infection, in association with abnormal tau phosphorylation at Ser202 /Thr205 (pSer202 /Thr205 ) and Ser396-404 (pSer396-404 ) in mouse brains. ECM also resulted in significantly higher expression of inflammatory markers, in microvascular congestion, and glial cell activation. Treatment with PHF-1 mAB prevented PbA-induced cognitive impairment and was associated with significantly less vascular congestion, neuroinflammation, and neural cell activation in mice with ECM. These findings suggest that abnormal regulation of tau protein contributes to cerebral vasculopathy and is critical in the pathogenesis of neural cell injury during CM. Tau-targeted therapies may ameliorate the neural cell damage and subsequent neurocognitive impairment that occur during disease.

Cerebral malaria induced by plasmodium falciparum: clinical features, pathogenesis, diagnosis, and treatment.

Cerebral malaria (CM) caused by Plasmodium falciparum is a fatal neurological complication of malaria, resulting in coma and death, and even survivors may suffer long-term neurological sequelae. In sub-Saharan Africa, CM occurs mainly in children under five years of age. Although intravenous artesunate is considered the preferred treatment for CM, the clinical efficacy is still far from satisfactory. The neurological damage induced by CM is irreversible and lethal, and it is therefore of great significance to unravel the exact etiology of CM, which may be beneficial for the effective management of this severe disease. Here, we review the clinical characteristics, pathogenesis, diagnosis, and clinical therapy of CM, with the aim of providing insights into the development of novel tools for improved CM treatments.

Cerebral Malaria: Current Clinical and Immunological Aspects.

This review focuses on current clinical and immunological aspects of cerebral malaria induced by Plasmodium falciparum infection. Albeit many issues concerning the inflammatory responses remain unresolved and need further investigations, current knowledge of the underlying molecular mechanisms is highlighted. Furthermore, and in the light of significant limitations in preventative diagnosis and treatment of cerebral malaria, this review mainly discusses our understanding of immune mechanisms in the light of the most recent research findings. Remarkably, the newly proposed CD8+ T cell-driven pathophysiological aspects within the central nervous system are summarized, giving first rational insights into encouraging studies with immune-modulating adjunctive therapies that protect from symptomatic cerebral participation of Plasmodium falciparum infection.

Whole blood transfusion improves vascular integrity and increases survival in artemether-treated experimental cerebral malaria.

Pathological features observed in both human and experimental cerebral malaria (ECM) are endothelial dysfunction and changes in blood components. Blood transfusion has been routinely used in patients with severe malarial anemia and can also benefit comatose and acidotic malaria patients. In the present study Plasmodium berghei-infected mice were transfused intraperitoneally with 200 µL of whole blood along with 20 mg/kg of artemether. ECM mice showed severe thrombocytopenia and decreases in hematocrit. Artemether treatment markedly aggravated anemia within 24 h. Whole blood administration significantly prevented further drop in hematocrit and partially restored the platelet count. Increased levels of plasma angiopoietin-2 (Ang-2) remained high 24 h after artemether treatment but returned to normal levels 24 h after blood transfusion, indicating reversal to quiescence. Ang-1 was depleted in ECM mice and levels were not restored by any treatment. Blood transfusion prevented the aggravation of the breakdown of blood brain barrier after artemether treatment and decreased spleen congestion without affecting splenic lymphocyte populations. Critically, blood transfusion resulted in markedly improved survival of mice with ECM (75.9% compared to 50.9% receiving artemether only). These findings indicate that whole blood transfusion can be an effective adjuvant therapy for cerebral malaria.

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.

Outcomes measures in children after acute central nervous system infections and malaria.

PURPOSE OF REVIEW: Acute central nervous system (CNS) infections in children result in significant mortality and neurologic morbidity worldwide. This article summarizes the recent pediatric literature published on outcomes measures used after acute infectious meningitis, encephalitis, and cerebral malaria, and highlights ongoing research efforts to standardize outcomes measurements. Search terms were geared toward functional, cognitive, behavioral, and other outcome assessments. RECENT FINDINGS: Recent data suggest that, depending on microbiological cause, there are differences in currently used outcome measures following acute CNS infections. Outcomes assessments include a variety of formal psychological tests (structured interviews and neuropsychological tests of cognitive and motor functioning) and dichotomized or ordinal scales. Standardization of outcome measures, however, is lacking. Global efforts to standardize outcomes that encompass both the child and family are ongoing. SUMMARY: Centers worldwide can track and measure a variety of cognitive, behavioral, and functional outcomes after acute CNS infections. Standardized documentation and coding of clinically important outcomes is needed. Further research to evaluate effective practices using acute adjunctive and rehabilitation therapies will be aided by outcome measure standardization.

NK Cell IL-10 Production Requires IL-15 and IL-10 Driven STAT3 Activation.

Natural killer (NK) cells can produce IFNγ or IL-10 to regulate inflammation and immune responses but the factors driving NK cell IL-10 secretion are poorly-defined. Here, we identified NK cell-intrinsic STAT3 activation as vital for IL-10 production during both systemic Listeria monocytogenes (Lm) infection and following IL-15 cytokine/receptor complex (IL15C) treatment for experimental cerebral malaria (ECM). In both contexts, conditional Stat3 deficiency in NK cells abrogated production of IL-10. Initial NK cell STAT3 phosphorylation was driven by IL-15. During Lm infection, this required capture or presentation of IL-15 by NK cell IL-15Rα. Persistent STAT3 activation was required to drive measurable IL-10 secretion and required NK cell expression of IL-10Rα. Survival-promoting effects of IL-15C treatment in ECM were dependent on NK cell Stat3 while NK cell-intrinsic deficiency for Stat3, Il15ra, or Il10ra abrogated NK cell IL-10 production and increased resistance against Lm. NK cell Stat3 deficiency did not impact production of IFNγ, indicating the STAT3 activation initiated by IL-15 and amplified by IL-10 selectively drives the production of anti-inflammatory IL-10 by responding NK cells.

Activated protein C in neuroprotection and malaria.

PURPOSE OF REVIEW: Activated protein C (APC) is a homeostatic coagulation protease with anticoagulant and cytoprotective activities. Focusing on APC's effects in the brain, this review discusses three different scenarios that illustrate how APC functions are intimately affecting the physiology and pathophysiology of the brain. RECENT FINDINGS: Cytoprotective APC therapy holds promise for the treatment of ischemic stroke, and a recently completed trial suggested that cytoprotective-selective 3K3A-APC reduced bleeding in ischemic stroke patients. In contrast, APC's anticoagulant activity contributes to brain bleeding as shown by the disproportional upregulation of APC generation in cerebral cavernous malformations lesions in mice. However, too little APC generation also contributes to maladies of the brain, such as in case of cerebral malaria where the binding of infected erythrocytes to the endothelial protein C receptor (EPCR) may interfere with the EPCR-dependent functions of the protein C pathway. Furthermore, discoveries of new activities of APC such as the inhibition of the NLRP3-mediated inflammasome and of new applications of APC therapy such as in Alzheimer's disease and graft-versus-host disease continue to advance our knowledge of this important proteolytic regulatory system. SUMMARY: APC's many activities or lack thereof are intimately involved in multiple neuropathologies, providing abundant opportunities for translational research.

Blood-Brain Barrier in Cerebral Malaria: Pathogenesis and Therapeutic Intervention.

Cerebral malaria is a life-threatening complication of malaria caused by the parasite Plasmodium falciparum. The growing problem of drug resistance and the dearth of new antiparasitic drugs are a serious threat to the antimalaria treatment regimes. Studies on humans and the murine model have implicated the disruption of the blood-brain barrier (BBB) in the lethal course of the disease. Therefore, efforts to alleviate the BBB dysfunction could serve as an adjunct therapy. Here, we review the mechanisms associated with the disruption of the BBB. In addition, we discuss the current, still limited, knowledge on the contribution of different cell types, microparticles, and the kynurenine pathway in the regulation of BBB dysfunction, and how these molecules could be used as potential new therapeutic targets.

Red blood cell exchange in treatment of severe cerebral P. falciparum malaria: A case report.

INTRODUCTION: Red blood cells exchange transfusion has been demonstrated to be helpful in treatment of sever P. falciparum malaria. However, no large scale randomized controlled trials have been completed to date and the CDC does not recommend RBC exchange transfusions as standard of care. We present a case of severe cerebral malaria in a patient with extremely high parasitemia and severe altered mental status who improved rapidly with automated RBC exchange. REPORT: Seventy-two year old female presented with 1 day history of weakness, altered mental status, malaise, and cyclic sweats after returning from a trip to Sierra Leone. Thick and Thin Smears demonstrated P. falciparum rings present and Quantitative malaria screen demonstrated 53.33% parasitemia. Patient was started on quinidine and doxycycline but continued to deteriorate. Automated RBC exchange transfusion was performed within 24 hours of admission and resulted in rapid improvement in symptomology. Repeat thick and thin smears revealed undetectable parasite load. CONCLUSION: Automated RBC exchange may improve outcomes in severe P. falciparum malaria when presenting parasite loads are very high.

Case Report: A Case of Severe Cerebral Malaria Managed with Therapeutic Hypothermia and Other Modalities for Brain Edema.

Malarial infections are uncommon in the United States and almost all reported cases stem from recent travelers coming from endemic countries. Cerebral malaria (CM) is a severe form of the disease usually affecting children and individuals with limited immunity. Despite proper management, mortality from CM can reach up to 25%, especially when it is associated with brain edema. Inefficient management of the edema may result in brain herniation and death. Uniform guidelines for management of CM-associated brain edema are lacking. In this report, we present a case of CM with associated severe brain edema that was successfully managed using a unique combination of therapeutic hypothermia, hypertonic saline, mannitol, and hyperventilation along with the antimalarial drugs quinidine and doxycycline. Our use of hypothermia was based on its proven benefit for improving neurological outcomes in post-cardiac arrest patients and previous in vitro research, suggesting its potential inhibitory role on malaria growth.

A Case of Cerebral Malaria Managed by Erythrocyte Exchange.

Plasmodium falciparum may cause serious and sometimes even fatal cerebral malaria. Cerebral malaria is a disease characterized by alterations in consciousness and epileptic attacks; therefore, it requires a rapid evaluation and quick intervention. It may progress to a fatal outcome despite administering targeted therapeutic interventions. There are studies indicating that erythrocyte exchange (erythrocytapheresis) can be a treatment modality for managing severe malaria patients. In this case report, the successful management of a cerebral malaria patient by the combination of antimalarial drug therapy and erythrocyte exchange is presented.

Cerebrospinal fluid and plasma ß-endorphin levels in children with cerebral malaria.

OBJECTIVES: Cerebral malaria (CM) is the most lethal form of malaria, yet its pathogenesis is not fully understood. Cytoadherence, sequestration, alterations in cytokine expression, inflammation, and microvascular obstruction are all hypothesized to be important in the aetio-pathogenesis of coma which characterizes cerebral malaria and the death which sometimes result. Beta (ß)-endorphin has been postulated to be involved in the pathogenetic processes of inflammation and cytokine expression, although the exact role is unknown. The aim of this study was to determine the levels of ß-endorphin in cerebrospinal fluid (CSF) and plasma of children with CM and compare the levels of ß-endorphin in the plasma of children with CM with that of apparently healthy age- and sex-matched controls at Ile-Ife, Nigeria. MATERIALS AND METHODS: Additional to the standard investigation for CM, CSF and venous blood samples were obtained from the subjects for the determination of ß-endorphin levels. RESULTS: Forty children with CM were studied along with forty age- and sex-matched controls. The mean CSF ß-endorphin (± SD) level for the children with CM was 1.8 ± 0.9 pmol/L. The mean plasma ß-endorphin levels at admission (3.1 ± 2.0 pmol/L) and discharge (4.1 ± 3.3 pmol/L) were higher in children with CM than in the control subjects (2.7 ± 0.7 pmol/L). However, only the mean plasma ß-endorphin levels at discharge was significantly higher than that of controls (p = .012). CONCLUSION: Children with CM had higher mean plasma ß-endorphin levels compared to the controls and there was increased production of ß-endorphins in children with CM during the course of the illness.

Clinical Comparison of Retinopathy-Positive and Retinopathy-Negative Cerebral Malaria.

AbstractCerebral malaria (CM) is a severe and often lethal complication of falciparum malaria. A classic malaria retinopathy is seen in some (retinopathy-positive [RP]) children but not others (retinopathy-negative [RN]), and is associated with increased parasite sequestration. It is unclear whether RN CM is a severe nonmalarial illness with incidental parasitemia or a less severe form of the same malarial illness as RP CM. Understanding the clinical differences between RP and RN CM may help shed light on the pathophysiology of malarial retinopathy. We compared clinical history, physical examination, laboratory findings, and outcomes of RP (N = 167) and RN (N = 87) children admitted to Mulago Hospital, Kampala, Uganda. Compared with RN children, RP children presented with a longer history of illness, as well as physical examination and laboratory findings indicative of more severe disease and organ damage. The hospital course of RP children was complicated by longer coma duration and a greater transfusion burden than RN children. Mortality did not differ significantly between RP and RN children (14.4% versus 8.0%, P = 0.14). Further, severity of retinal hemorrhage correlated with the majority of variables that differed between RP and RN children. The data suggest that RP and RN CM may reflect the spectrum of illness in CM, and that RN CM could be an earlier, less severe form of disease.

A report of cerebral malaria treated with automated red blood cell exchange.

BACKGROUND: Adjunctive automated whole blood or red blood cell exchange (RBCEx) can rapidly decrease malarial hyperparasitemia. Several case reports and series suggest improvement in clinical symptomatology; however, recent Centers of Disease Control and Prevention (CDC) recommendations concluded that RBCEx has no efficacy as an adjunctive therapy. We present a case of mental status changes secondary to cerebral malaria treated with automated RBCEx resulting in rapid and dramatic neurologic improvement. CASE REPORT: An 84-year-old Somali woman presented with a 3-day history of altered mental status, spiking fevers, chills, bilateral leg pain and weakness, and intermittent diarrhea. Her travel history included a recent trip to Kenya for 1 month without antimalarial chemoprophylaxis. During the hospital stay, her health declined, and she became obtunded. Physical examination revealed fever, tachypnea, hypertension, hypoxia, and no response to verbal or physical stimuli. Her hemoglobin decreased from 12.6 to 6.5 g/dL with 12% intraerythrocytic parasitemia by thin smear. Intraerythrocytic trophozoites and banana-shaped gametocytes were present consistent with Plasmodium falciparum. An emergent 1.5-volume RBC mass automated RBCEx and quinidine infusion decreased her parasitemia to 2%. The patient's mental status improved throughout the procedure, and after the 2½-hour procedure, the patient was alert, oriented, and speaking coherently. The patient continued to receive quinidine and artesunate 1 day later from CDC. CONCLUSION: Automated RBCEx transfusion reduced the parasite burden and restored neurologic functioning in a patient with cerebral malaria while awaiting definitive treatment with artesunate.

Long-term Behavioral Problems in Children With Severe Malaria.

BACKGROUND: Severe malaria in children is associated with long-term neurocognitive impairment, but it is unclear whether it is associated with long-term behavioral problems. METHODS: Children <5 years old with cerebral malaria (CM) or severe malarial anemia (SMA) treated at Mulago Hospital, Kampala, Uganda were assessed for behavioral outcomes at 0, 6, 12, and 24 months using the Child Behavior Checklist. Sample sizes at 0, 12, and 24 months were 122, 100, and 80 in the CM group, 130, 98, and 81 in the SMA group, and 149, 123, and 90 in healthy community control (CC) children, respectively. Age adjusted z-scores for behavioral outcomes were computed using scores for the CC group. Study groups were compared using regression models adjusted for age, nutritional status, preschool education, and socioeconomic status. RESULTS: At 12 months, children with SMA had higher z-scores than CC children for internalizing (mean difference, 0.49; SE, 0.14; P = .001), externalizing (mean difference, 0.49; SE, 0.15; P = .001), and total problems (mean difference, 0.51; SE, 0.15; P < .001). Children with CM had higher adjusted z-scores than CC children for externalizing problems (mean difference, 0.39; SE, 0.15; P = .009) but not internalizing or total problems. At 24 months, children with CM or SMA both had increased internalizing and externalizing behavioral problems compared with CC children (P ≤ .05 for all). CONCLUSIONS: CM and SMA are associated with long-term internalizing and externalizing behavioral problems in children. They may contribute substantially to mental health morbidity in children <5 years old in malaria endemic areas.

Safety of lumbar puncture in comatose children with clinical features of cerebral malaria.

OBJECTIVE: We assessed the independent association of lumbar puncture (LP) and death in Malawian children admitted to the hospital with the clinical features of cerebral malaria (CM). METHODS: This was a retrospective cohort study in Malawian children with clinical features of CM. Allocation to LP was nonrandom and was associated with severity of illness. Propensity score-based analyses were used to adjust for this bias and assess the independent association between LP and mortality. RESULTS: Data were available for 1,075 children: 866 (80.6%) underwent LP and 209 (19.4%) did not. Unadjusted mortality rates were lower in children who underwent LP (15.3% vs 26.7% in the no-LP group) but differences in covariates between the 2 groups suggested bias in LP allocation. After propensity score matching, all covariates were balanced. Propensity score-based analyses showed no change in mortality rate associated with LP: by inverse probability weighting, the average risk reduction was 2.0% at 12 hours (95% confidence interval -1.5% to 5.5%, p = 0.27) and 1.7% during hospital admission (95% confidence interval -4.5% to 7.9%, p = 0.60). Undergoing LP did not change the risk of mortality in subanalyses of children with severe brain swelling on MRI or in those with papilledema. CONCLUSION: In comatose children with suspected CM who were clinically stable, we found no evidence that LP increases mortality, even in children with objective signs of raised intracranial pressure.