Brain swelling and ischaemia in Kenyans with cerebral malaria

Pattern of Clinical and Laboratory Presentation of Cerebral Malaria among Children in Nigeria

Introduction

Cerebral malaria (CM) is the most lethal form of severe malaria with high case fatality rates. Overtime, there is an inherent risk in changing pattern of presentation of CM which, if the diagnosis is missed due to these changing factors, may portend a poor outcome. Variations in the pattern of clinic-laboratory presentations also make generalization difficult. This study was, therefore, set out to report the pattern of clinical and laboratory presentation of CM.

Methods

This was a cross-sectional study among children aged 6 months to 14 years admitted with a diagnosis of CM as defined by the World Health Organization criteria. A pretested pro forma was filled, and detailed neurological examination and laboratory (biochemical, microbiology, and hematology) investigations were done. P <5% was considered statistically significant.

Results

Sixty-four children were recruited with a mean age of 34.9 ± 24.9 months and a male-to-female ratio of 1.9:1. There were 87.5% of under-five children. Fever (96.9%) was the major presenting feature closely followed by convulsions (92.2%). Convulsions were mainly generalized (94.9%) and multiple (76.5%). Profound coma (Blantyre coma score of 0) was present in 12.5% of cases, and the leading features on examination were fever (84.4%) and pallor (75.0%). Retinal vessel whitening (48.4%) was the most common funduscopic abnormality. Metabolic acidosis (47.9%), severe anemia (14.1%), hyperglycemia (17.2%), and hypoglycemia (7.8%) were seen among the children. Few (1.6%) had hyperparasitemia and bacteremia (3.2%).

Conclusion

Early recognition of the clinical presentation and prompt management may improve the outcome of cerebral malaria.

DHA-rich fish oil plays a protective role against experimental cerebral malaria by controlling inflammatory and mechanical events from infection

Every year, thousands of children, particularly those under 5 years old, die because of cerebral malaria (CM). Following conventional treatment, approximately 25% of surviving individuals have lifelong severe neurocognitive sequelae. Therefore, improved conventional therapies or effective alternative therapies that prevent the severe infection are crucial. Omega-3 (Ω-3) polyunsaturated fatty acids (PUFAs) are known to have antioxidative and anti-inflammatory effects and protect against diverse neurological disorders, including Alzheimer's and Parkinson's diseases. However, little is known regarding the effects of Ω-3 PUFAs against parasitic infections. In this study, C57BL/6 mice received supplemental treatment of a fish oil rich in the Ω-3 PUFA, docosahexaenoic acid (DHA), which was started 15 days prior to infection with Plasmodium berghei ANKA and was maintained until the end of the study. Animals treated with the highest doses of DHA, 3.0 and 6.0 g/kg body weight, had 60 and 80% chance of survival, respectively, while all nontreated mice died by the 7th day postinfection due to CM. Furthermore, the parasite load during the critical period for CM development (5th to 11th day postinfection) was controlled in treated mice. However, after this period all animals developed high levels of parasitemia until the 20th day of infection. DHA treatment also effectively reduced blood-brain barrier (BBB) damage and brain edema and completely prevented brain hemorrhage and vascular occlusion. A strong anti-inflammatory profile was observed in the brains of DHA-treated mice, as well as, an increased number of neutrophil and reduced number of CD8+ T leukocytes in the spleen. Thus, this is the first study to demonstrate that the prophylactic use of DHA-rich fish oil exerts protective effects against experimental CM, reducing the mechanical and immunological events caused by the P. berghei ANKA infection.

Imaging features of fulminant cerebral malaria: A case report

Cerebral malaria is associated with high mortality and morbidity in patients infected with Plasmodium Falciparum. The mechanisms of cerebral malaria include sequestration of parasitized red blood cells in brain capillaries, production of cytokines, immune cell/platelet accumulation, and release of microparticles, resulting in disruption of the blood-brain barrier, which caused brain injuries. The severity of this reflects on neurological findings ranging from simple delirium to profound coma. We herein present unique magnetic resonance imaging findings of a case of fulminant cerebral malaria as computed tomography studies usually underestimate the extent of cerebral involvement in malaria.

Cerebrospinal fluid biomarkers provide evidence for kidney-brain axis involvement in cerebral malaria pathogenesis

Introduction

Cerebral malaria is one of the most severe manifestations of malaria and is a leading cause of acquired neurodisability in African children. Recent studies suggest acute kidney injury (AKI) is a risk factor for brain injury in cerebral malaria. The present study evaluates potential mechanisms of brain injury in cerebral malaria by evaluating changes in cerebrospinal fluid measures of brain injury with respect to severe malaria complications. Specifically, we attempt to delineate mechanisms of injury focusing on blood-brain-barrier integrity and acute metabolic changes that may underlie kidney-brain crosstalk in severe malaria.

Methods

We evaluated 30 cerebrospinal fluid (CSF) markers of inflammation, oxidative stress, and brain injury in 168 Ugandan children aged 18 months to 12 years hospitalized with cerebral malaria. Eligible children were infected with Plasmodium falciparum and had unexplained coma. Acute kidney injury (AKI) on admission was defined using the Kidney Disease: Improving Global Outcomes criteria. We further evaluated blood-brain-barrier integrity and malaria retinopathy, and electrolyte and metabolic complications in serum.

Results

The mean age of children was 3.8 years (SD, 1.9) and 40.5% were female. The prevalence of AKI was 46.3% and multi-organ dysfunction was common with 76.2% of children having at least one organ system affected in addition to coma. AKI and elevated blood urea nitrogen, but not other measures of disease severity (severe coma, seizures, jaundice, acidosis), were associated with increases in CSF markers of impaired blood-brain-barrier function, neuronal injury (neuron-specific enolase, tau), excitatory neurotransmission (kynurenine), as well as altered nitric oxide bioavailability and oxidative stress (p < 0.05 after adjustment for multiple testing). Further evaluation of potential mechanisms suggested that AKI may mediate or be associated with CSF changes through blood-brain-barrier disruption (p = 0.0014), ischemic injury seen by indirect ophthalmoscopy (p < 0.05), altered osmolality (p = 0.0006) and through alterations in the amino acids transported into the brain.

Conclusion

In children with cerebral malaria, there is evidence of kidney-brain injury with multiple potential pathways identified. These changes were specific to the kidney and not observed in the context of other clinical complications.

Diagnosis of cerebral malaria: Tools to reduce Plasmodium falciparum associated mortality

Cerebral malaria (CM) is a major cause of mortality in Plasmodium falciparum (Pf) infection and is associated with the sequestration of parasitised erythrocytes in the microvasculature of the host's vital organs. Prompt diagnosis and treatment are key to a positive outcome in CM. However, current diagnostic tools remain inadequate to assess the degree of brain dysfunction associated with CM before the window for effective treatment closes. Several host and parasite factor-based biomarkers have been suggested as rapid diagnostic tools with potential for early CM diagnosis, however, no specific biomarker signature has been validated. Here, we provide an updated review on promising CM biomarker candidates and evaluate their applicability as point-of-care tools in malaria-endemic areas.

Cerebral Malaria and Neuronal Implications of Plasmodium Falciparum Infection: From Mechanisms to Advanced Models

Reorganization of host red blood cells by the malaria parasite Plasmodium falciparum enables their sequestration via attachment to the microvasculature. This artificially increases the dwelling time of the infected red blood cells within inner organs such as the brain, which can lead to cerebral malaria. Cerebral malaria is the deadliest complication patients infected with P. falciparum can experience and still remains a major public health concern despite effective antimalarial therapies. Here, the current understanding of the effect of P. falciparum cytoadherence and their secreted proteins on structural features of the human blood-brain barrier and their involvement in the pathogenesis of cerebral malaria are highlighted. Advanced 2D and 3D in vitro models are further assessed to study this devastating interaction between parasite and host. A better understanding of the molecular mechanisms leading to neuronal and cognitive deficits in cerebral malaria will be pivotal in devising new strategies to treat and prevent blood-brain barrier dysfunction and subsequent neurological damage in patients with cerebral malaria.

Acute Malaria in Malawian Children and Adults is Characterized by Thrombocytopenia That Normalizes in Convalescence

Background

Plasmodium falciparum malaria has been linked with significant perturbations of the peripheral cell-mediated immune system during acute phase. Some of these changes include lower than normal platelet counts. Although the exact mechanisms that drive thrombocytopenia in P. falciparum malaria are not fully known, a number of hypotheses have been proposed. We conducted two sets of studies with one aimed at determining platelet counts in Malawian children, and the other in adults during acute P. falciparum malaria and a month post treatment.

Materials and Methods

We recruited a total of 113 HIV-uninfected children with acute malaria [n=54 with uncomplicated malaria (UCM), n=30 with severe malarial anemia (SMA), n=29 presenting with cerebral malaria (CM)]. We also recruited 42 HIV-uninfected healthy controls. Out of the 113 participants with malaria, 73 (65%) [n=34 (63%) UCM, n=21 (70%) SMA and n=18 (62%) CM] were successfully followed-up one month after treatment. A 5mL peripheral blood sample was collected for platelet count using HMX Haematological Analyzer analysis both at baseline (acute malaria) and at follow-up a month later. Platelet counts were also determined in blood samples of 106 HIV-uninfected adults, 47 of whom presented with UCM and 29 with severe malaria (SM) and these counts were compared to those of 30 healthy controls. Of the malaria cases, platelet counts for 44 UCM and 21 SM were determined again during follow-up a month after treatment.

Results

In both children and adults, platelet counts were significantly lower during acute disease compared to the levels in the healthy controls with the lowest levels observed in CM (children) or SM (adults). These lower than normal levels increased close to normal levels a month post treatment.

Conclusion

P. falciparum malaria in Malawian children and adults was characterized by profound thrombocytopenia which recovered during convalescence.

Neuroimmunology of Common Parasitic Infections in Africa

Parasitic infections of the central nervous system are an important cause of morbidity and mortality in Africa. The neurological, cognitive, and psychiatric sequelae of these infections result from a complex interplay between the parasites and the host inflammatory response. Here we review some of the diseases caused by selected parasitic organisms known to infect the nervous system including Plasmodium falciparum, Toxoplasma gondii, Trypanosoma brucei spp., and Taenia solium species. For each parasite, we describe the geographical distribution, prevalence, life cycle, and typical clinical symptoms of infection and pathogenesis. We pay particular attention to how the parasites infect the brain and the interaction between each organism and the host immune system. We describe how an understanding of these processes may guide optimal diagnostic and therapeutic strategies to treat these disorders. Finally, we highlight current gaps in our understanding of disease pathophysiology and call for increased interrogation of these often-neglected disorders of the nervous system.

Expression of CD11a, CD11b, CD11c, and CD18 on Neutrophils from Different Clinical Types of Malaria in Malawian Children

BACKGROUND

Malaria in individuals who have never had an infection before is usually characterized by an inflammatory response that is linked to the expression of specific activation markers on cells of the innate immune system.

METHODS

This study investigated absolute white blood cell (WBC) and neutrophil counts and expression of several adhesion markers on neutrophils from HIV-uninfected children who were suffering from cerebral malaria (n=35), severe malarial anemia (SMA, n=39), and uncomplicated malaria (n=49) and healthy aparasitemic children (n=33) in Blantyre, Malawi.

RESULTS

All clinical malaria groups had higher WBC and neutrophil counts compared to healthy controls, with the acute SMA group having significantly (p<0.0001) higher WBC counts than the controls. These elevated counts normalized during recovery. Surprisingly, in all clinical malaria groups, the surface expression of CD11b, CD11c, and CD18 on neutrophils was lower than in healthy controls, again normalizing during convalescence.

CONCLUSION

In areas where Plasmodium falciparum malaria is hyperendemic, such as where this study was conducted, neutrophils have reduced expression of adhesion molecules and activation markers during acute stages of the infection, regardless of the clinical type of malaria. This reduced expression could be due to an individual's past exposure to P. falciparum or other parasite-related factors that manifest during active malaria that still need to be investigated.

Dimethyl fumarate reduces TNF and Plasmodium falciparum induced brain endothelium activation in vitro

Background

Cerebral malaria (CM) is associated with morbidity and mortality despite the use of potent anti-malarial agents. Brain endothelial cell activation and dysfunction from oxidative and inflammatory host responses and products released by Plasmodium falciparum-infected erythrocytes (IE), are likely the major contributors to the encephalopathy, seizures, and brain swelling that are associated with CM. The development of adjunctive therapy to reduce the pathological consequences of host response pathways could improve outcomes. A potentially protective role of the nuclear factor E2-related factor 2 (NRF2) pathway, which serves as a therapeutic target in brain microvascular diseases and central nervous system (CNS) inflammatory diseases such as multiple sclerosis was tested to protect endothelial cells in an in vitro culture system subjected to tumour necrosis factor (TNF) or infected red blood cell exposure. NRF2 is a transcription factor that mediates anti-oxidant and anti-inflammatory responses.

Methods

To accurately reflect clinically relevant parasite biology a unique panel of parasite isolates derived from patients with stringently defined CM was developed. The effect of TNF and these parasite lines on primary human brain microvascular endothelial cell (HBMVEC) activation in an in vitro co-culture model was tested. HBMVEC activation was measured by cellular release of IL6 and nuclear translocation of NFκB. The transcriptional and functional effects of dimethyl fumarate (DMF), an FDA approved drug which induces the NRF2 pathway, on host and parasite induced HBMVEC activation was characterized. In addition, the effect of DMF on parasite binding to TNF stimulated HBMVEC in a semi-static binding assay was examined.

Results

Transcriptional profiling demonstrates that DMF upregulates the NRF2-Mediated Oxidative Stress Response, ErbB4 Signaling Pathway, Peroxisome Proliferator-activated Receptor (PPAR) Signaling and downregulates iNOS Signaling and the Neuroinflammation Signaling Pathway on TNF activated HBMVEC. The parasite lines derived from eight paediatric CM patients demonstrated increased binding to TNF activated HBMVEC and varied in their binding and activation of HBMVEC. Overall DMF reduced both TNF and CM derived parasite activation of HBMVEC.

Conclusions

These findings provide evidence that targeting the NRF2 pathway in TNF and parasite activated HBMVEC mediates multiple protective pathways and may represent a novel adjunctive therapy to improve infection outcomes in CM.

Intracranial Pressure and Brain Tissue Oxygen Neuromonitoring in Pediatric Cerebral Malaria

BACKGROUND

Pediatric cerebral malaria (CM) is a severe complication of Plasmodium falciparum that often leaves survivors with severe neurologic impairment. Increased intracranial pressure (ICP) as a result of cerebral edema has been identified as a major predictor of morbidity and mortality in CM. Past studies have demonstrated that survivors are more likely to have resolution of elevated ICP and that efficient management of ICP crises may lead to better outcomes. However, data on invasive brain tissue oxygen monitoring are unknown.

CASE DESCRIPTION

We report a case of a pediatric patient with cerebral malaria who developed encephalopathy and cerebral edema and describe the pathophysiology of this disease process with invasive ICP and brain tissue oxygen multimodality neuromonitoring. The utilization of both ICP and brain tissue oxygen monitoring allowed prompt diagnosis and successful treatment of severe intracranial hypertension and low brain tissue oxygenation crisis. The patient was discharged to home in good neurologic condition.

CONCLUSIONS

Multimodality neuromonitoring may be considered in pediatric patients who have cerebral edema and encephalopathy from CM.

Cerebral Plasmodium falciparum malaria: The role of PfEMP1 in its pathogenesis and immunity, and PfEMP1-based vaccines to prevent it

Malaria, a mosquito-borne infectious disease caused by parasites of the genus Plasmodium continues to be a major health problem worldwide. The unicellular Plasmodium-parasites have the unique capacity to infect and replicate within host erythrocytes. By expressing variant surface antigens Plasmodium falciparum has evolved to avoid protective immune responses; as a result in endemic areas anti-malaria immunity develops gradually over many years of multiple and repeated infections. We are studying the role of Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) expressed by asexual stages of P. falciparum responsible for the pathogenicity of severe malaria. The immunopathology of falciparum malaria has been linked to cyto-adhesion of infected erythrocytes to specific host receptors. A greater appreciation of the PfEMP1 molecules important for the development of protective immunity and immunopathology is a prerequisite for the rational discovery and development of a safe and protective anti-disease malaria vaccine. Here we review the role of ICAM-1 and EPCR receptor adhering falciparum-parasites in the development of severe malaria; we discuss our current research to understand the factors involved in the pathogenesis of cerebral malaria and the feasibility of developing a vaccine targeted specifically to prevent this disease.

Transcranial Doppler Ultrasonography Provides Insights into Neurovascular Changes in Children with Cerebral Malaria

OBJECTIVE

To evaluate neurovascular changes in pediatric patients with cerebral malaria.

STUDY DESIGN

African children with cerebral malaria were enrolled and underwent daily transcranial Doppler ultrasound (TCD) examinations through hospital day 8, discharge, or death. Neurologic outcomes were assessed 2 weeks after enrollment.

RESULTS

In total, 160 children with cerebral malaria and 155 comparison patients were included. In patients with cerebral malaria, TCD flow changes characterized as hyperemia were seen in 42 (26%), low flow in 46 (28%), microvascular obstruction in 35 (22%), cerebral vasospasm in 21 (13%), and isolated posterior hyperemia in 7 (4%). Most had a single neurovascular phenotype observed throughout participation. Among comparison patients, 76% had normal TCD findings (P < .001). Impaired autoregulation was present in 80% of cases (transient hyperemic response ratio 1.01 ± 0.03) but improved through day 4 (1.1 ± 0.02, P = .014). Overall mortality was 24% (n = 39). Neurologic deficits were evident in 21% of survivors. Children meeting criteria for vasospasm were most likely to survive with sequelae, and children meeting criteria for low flow were most likely to die. Autoregulation was better in children with a normal neurologic outcome (1.09, 95% CI 1.06-1.12) than in others (0.98, 95% CI 0.95-1) (P ≤ .001).

CONCLUSIONS

Several distinct changes in TCD measurements were identified in children with cerebral malaria that permitted phenotypic grouping. Groups had distinct associations with neurologic outcomes. Validation of pathogenic mechanisms associated with each phenotype may aid in developing TCD as a portable, easy-to-use tool to help guide targeted adjunctive therapy in cerebral malaria aimed at causative mechanisms of injury on an individual level.

Brain swelling is independent of peripheral plasma cytokine levels in Malawian children with cerebral malaria

Background

Cerebral malaria (CM) is often fatal, and severe brain swelling is a predictor of CM-related mortality. CM is characterized by elevated circulating pro-inflammatory cytokines TNF and IFN-γ and anti-inflammatory cytokine IL-10, however whether cytokine levels correlate with brain swelling severity is unknown. This study therefore was conducted to investigate the relationship between cytokine levels and brain swelling severity in children presenting with CM.

Methods

A total of 195 Malawian children presenting with CM were recruited and had the concentrations of plasma cytokines determined and compared to brain swelling severity, determined by MRI examination, and graded as severe, moderate, mild or none.

Results

Levels of IL-1β, IL-6, IL-8 and IL-10 did not differ between CM patients with and without severe brain swelling. Compared to children without brain swelling, IL-12 levels were higher in children with severe swelling (p < 0.01, no swelling 1 pg/mL, IQR [1] vs. severe swelling 18.7 pg/mL, IQR [1–27]), whereas TNF concentrations were higher in children with moderate brain swelling compared to children with no swelling (p < 0.01, no swelling 3 pg/mL, IQR [1–20] vs. moderate swelling 24 pg/mL, IQR [8–58]. Multivariate analysis showed that no single cytokine independently predicted brain swelling.

Conclusion

Severe brain swelling in paediatric CM was independent of tested blood pro-inflammatory and anti-inflammatory cytokines which are markers of systemic inflammation.

Electronic supplementary material

The online version of this article (10.1186/s12936-018-2590-0) contains supplementary material, which is available to authorized users.

Cerebrospinal fluid Plasmodium falciparum histidine-rich protein-2 in pediatric cerebral malaria

BACKGROUND

Cerebral malaria (CM) causes a rapidly developing coma, and remains a major contributor to morbidity and mortality in malaria-endemic regions. This study sought to determine the relationship between cerebrospinal fluid (CSF) Plasmodium falciparum histidine rich protein-2 (PfHRP-2) and clinical, laboratory and radiographic features in a cohort of children with retinopathy-positive CM.

METHODS

Patients included in the study were admitted (2009-2013) to the Pediatric Research Ward (Queen Elizabeth Central Hospital, Blantyre, Malawi) meeting World Health Organization criteria for CM with findings of malarial retinopathy. Enzyme-linked immunosorbent assay was used to determine plasma and CSF PfHRP-2 levels. Wilcoxon rank-sum tests and multivariable logistic regression analysis assessed the association of clinical and radiographic characteristics with the primary outcome of death during hospitalization.

RESULTS

In this cohort of 94 patients, median age was 44 (interquartile range 29-62) months, 53 (56.4%) patients were male, 6 (7%) were HIV-infected, and 10 (11%) died during hospitalization. Elevated concentrations of plasma lactate (p = 0.005) and CSF PfHRP-2 (p = 0.04) were significantly associated with death. On multivariable analysis, higher PfHRP-2 in the CSF was associated with death (odds ratio 9.00, 95% confidence interval 1.44-56.42) while plasma PfHRP-2 was not (odds ratio 2.05, 95% confidence interval 0.45-9.35).

CONCLUSIONS

Elevation of CSF, but not plasma PfHRP-2, is associated with death in this paediatric CM cohort. PfHRP-2 egress into the CSF may represent alteration of blood brain barrier permeability related to the sequestration of parasitized erythrocytes in the cerebral microvasculature.

Noninvasive measures of brain edema predict outcome in pediatric cerebral malaria

Background:

Increased brain volume (BV) and subsequent herniation are strongly associated with death in pediatric cerebral malaria (PCM), a leading killer of children in developing countries. Accurate noninvasive measures of BV are needed for optimal clinical trial design. Our objectives were to examine the performance of six different magnetic resonance imaging (MRI) BV quantification measures for predicting mortality in PCM and to review the advantages and disadvantages of each method.

Methods:

Receiver operator characteristics were generated from BV measures of MRIs of children admitted to an ongoing research project with PCM between 2009 and 2014. Fatal cases were matched to the next available survivor. A total of 78 MRIs of children aged 5 months to 13 years (mean 4.0 years), of which 45% were males, were included.

Results:

Areas under the curve (AUC) with 95% confidence interval on measures from the initial MRIs were: Radiologist-derived score = 0.69 (0.58–0.79; P = 0.0037); prepontine cistern anteroposterior (AP) dimension = 0.70 (0.56–0.78; P = 0.0133); SamKam ratio [Rt. parietal lobe height/(prepontine AP dimension + fourth ventricle AP dimension)] = 0.74 (0.63–0.83; P = 0.0002); and global cerebrospinal fluid (CSF) space ascertained by ClearCanvas = 0.67 (0.55–0.77; P = 0.0137). For patients with serial MRIs (n = 37), the day 2 global CSF space AUC was 0.87 (0.71–0.96; P < 0.001) and the recovery factor (CSF volume day 2/CSF volume day 1) was 0.91 (0.76–0.98; P < 0.0001). Poor prognosis is associated with radiologist score of ≥7; prepontine cistern dimension ≤3 mm; cisternal CSF volume ≤7.5 ml; SamKam ratio ≥6.5; and recovery factor ≤0.75.

Conclusion:

All noninvasive measures of BV performed well in predicting death and providing a proxy measure for brain volume. Initial MRI assessment may inform future clinical trials for subject selection, risk adjustment, or stratification. Measures of temporal change may be used to stage PCM.

Young Sprague Dawley rats infected by Plasmodium berghei: A relevant experimental model to study cerebral malaria

Cerebral malaria (CM) is the most severe manifestation of human malaria yet is still poorly understood. Mouse models have been developed to address the subject. However, their relevance to mimic human pathogenesis is largely debated. Here we study an alternative cerebral malaria model with an experimental Plasmodium berghei Keyberg 173 (K173) infection in Sprague Dawley rats. As in Human, not all infected subjects showed cerebral malaria, with 45% of the rats exhibiting Experimental Cerebral Malaria (ECM) symptoms while the majority (55%) of the remaining rats developed severe anemia and hyperparasitemia (NoECM). These results allow, within the same population, a comparison of the noxious effects of the infection between ECM and severe malaria without ECM. Among the ECM rats, 77.8% died between day 5 and day 12 post-infection, while the remaining rats were spontaneously cured of neurological signs within 24-48 hours. The clinical ECM signs observed were paresis quickly evolving to limb paralysis, global paralysis associated with respiratory distress, and coma. The red blood cell (RBC) count remained normal but a drastic decrease of platelet count and an increase of white blood cell numbers were noted. ECM rats also showed a decrease of glucose and total CO2 levels and an increase of creatinine levels compared to control rats or rats with no ECM. Assessment of the blood-brain barrier revealed loss of integrity, and interestingly histopathological analysis highlighted cyto-adherence and sequestration of infected RBCs in brain vessels from ECM rats only. Overall, this ECM rat model showed numerous clinical and histopathological features similar to Human CM and appears to be a promising model to achieve further understanding the CM pathophysiology in Humans and to evaluate the activity of specific antimalarial drugs in avoiding/limiting cerebral damages from malaria.

Dynamic interactions of Plasmodium spp. with vascular endothelium

Plasmodial species are protozoan parasites that infect erythrocytes. As such, they are in close contact with microvascular endothelium for most of the life cycle in the mammalian host. The host-parasite interactions of this stage of the infection are responsible for the clinical manifestations of the disease that range from a mild febrile illness to severe and frequently fatal syndromes such as cerebral malaria and multi-organ failure. Plasmodium falciparum, the causative agent of the most severe form of malaria, is particularly predisposed to modulating endothelial function through either direct adhesion to endothelial receptor molecules, or by releasing potent host and parasite products that can stimulate endothelial activation and/or disrupt barrier function. In this review, we provide a critical analysis of the current clinical and laboratory evidence for endothelial dysfunction during severe P. falciparum malaria. Future investigations using state-of-the-art technologies such as mass cytometry and organs-on-chips to further delineate parasite-endothelial cell interactions are also discussed.

CD8+ T Cells Induce Fatal Brainstem Pathology during Cerebral Malaria via Luminal Antigen-Specific Engagement of Brain Vasculature

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection that results in thousands of deaths each year, mostly in African children. The in vivo mechanisms underlying this fatal condition are not entirely understood. Using the animal model of experimental cerebral malaria (ECM), we sought mechanistic insights into the pathogenesis of CM. Fatal disease was associated with alterations in tight junction proteins, vascular breakdown in the meninges / parenchyma, edema, and ultimately neuronal cell death in the brainstem, which is consistent with cerebral herniation as a cause of death. At the peak of ECM, we revealed using intravital two-photon microscopy that myelomonocytic cells and parasite-specific CD8⁺ T cells associated primarily with the luminal surface of CNS blood vessels. Myelomonocytic cells participated in the removal of parasitized red blood cells (pRBCs) from cerebral blood vessels, but were not required for the disease. Interestingly, the majority of disease-inducing parasite-specific CD8⁺ T cells interacted with the lumen of brain vascular endothelial cells (ECs), where they were observed surveying, dividing, and arresting in a cognate peptide-MHC I dependent manner. These activities were critically dependent on IFN-γ, which was responsible for activating cerebrovascular ECs to upregulate adhesion and antigen-presenting molecules. Importantly, parasite-specific CD8⁺ T cell interactions with cerebral vessels were impaired in chimeric mice rendered unable to present EC antigens on MHC I, and these mice were in turn resistant to fatal brainstem pathology. Moreover, anti-adhesion molecule (LFA-1 / VLA-4) therapy prevented fatal disease by rapidly displacing luminal CD8⁺ T cells from cerebrovascular ECs without affecting extravascular T cells. These in vivo data demonstrate that parasite-specific CD8⁺ T cell-induced fatal vascular breakdown and subsequent neuronal death during ECM is associated with luminal, antigen-dependent interactions with cerebrovasculature.

Cerebral malaria (CM) is a severe and potentially fatal complication of malaria in humans that results in swelling and bleeding within the brain. The mechanisms that cause this fatal disease in humans are not completely understood. We studied an animal model known as experimental cerebral malaria to learn more about the factors that drive this disease process. Using a technique referred to as intravital microscopy, we captured movies of immune cells operating in the living brain as the disease developed. At the peak of disease, we observed evidence of immune cells interacting with and aggregating along blood vessels throughout the brain. These interactions were directly associated vascular leakage. This caused the brain to swell, which gave rise to an unsustainable pressure that ultimately killed neurons responsible for heart and lung function. The fatal swelling was induced by immune cells (referred to as T cells) interacting with bits of parasite presented by blood vessels in the brain. Removal of this parasite presentation protected the mice from fatal disease. We also evaluated a straightforward therapy that involved intravenous administration of antibodies that interfered with T cell sticking to blood vessels. Our movies revealed that this therapeutic approach rapidly displaced T cells from the blood vessels in the brain and prevented fatal disease.

Lipid metabolites of the phospholipase A2 pathway and inflammatory cytokines are associated with brain volume in paediatric cerebral malaria

Background

Cerebral malaria (CM) remains a significant cause of morbidity and mortality in children in sub-Saharan Africa. CM mortality has been associated with increased brain volume, seen on neuroimaging studies.

Methods

To examine the potential role of blood metabolites and inflammatory mediators in increased brain volume in Malawian children with CM, an association study was performed between plasma metabolites, cytokine levels and phospholipase A₂ (PLA₂) activity with brain volume.

Results

The metabolomics analysis demonstrated arachidonic acid and other lysophospholipids to be positively associated with brain swelling. These lipids are products of the PLA₂ enzyme and an association of plasma PLA₂ enzymatic activity with brain swelling was confirmed. TNFα, which can upregulate PLA₂ activity, was associated with brain volume. In addition, CCL2 and IL-8 were also associated with brain volume. Some of these cytokines can alter endothelial cell tight junction proteins and increase blood brain barrier permeability.

Conclusions

Taken together, paediatric CM brain volume was associated with products of the PLA₂ pathway and inflammatory cytokines. Their role in causality is unknown. These molecules will need to undergo testing in vitro and in animal models to understand their role in processes of increased brain volume. These observations provide novel data on host physiology associated with paediatric CM brain swelling, and may both inform pathogenesis models and suggest adjunct therapies that could improve the morbidity and mortality associated with paediatric CM.

Electronic supplementary material

The online version of this article (doi:10.1186/s12936-015-1036-1) contains supplementary material, which is available to authorized users.

The immunological balance between host and parasite in malaria

Coevolution of humans and malaria parasites has generated an intricate balance between the immune system of the host and virulence factors of the parasite, equilibrating maximal parasite transmission with limited host damage. Focusing on the blood stage of the disease, we discuss how the balance between anti-parasite immunity versus immunomodulatory and evasion mechanisms of the parasite may result in parasite clearance or chronic infection without major symptoms, whereas imbalances characterized by excessive parasite growth, exaggerated immune reactions or a combination of both cause severe pathology and death, which is detrimental for both parasite and host. A thorough understanding of the immunological balance of malaria and its relation to other physiological balances in the body is of crucial importance for developing effective interventions to reduce malaria-related morbidity and to diminish fatal outcomes due to severe complications. Therefore, we discuss in this review the detailed mechanisms of anti-malarial immunity, parasite virulence factors including immune evasion mechanisms and pathogenesis. Furthermore, we propose a comprehensive classification of malaria complications according to the different types of imbalances.

Pathogenesis of cerebral malaria: new diagnostic tools, biomarkers, and therapeutic approaches

Cerebral malaria is a severe neuropathological complication of Plasmodium falciparum infection. It results in high mortality and post-recovery neuro-cognitive disorders in children, even after appropriate treatment with effective anti-parasitic drugs. While the complete landscape of the pathogenesis of cerebral malaria still remains to be elucidated, numerous innovative approaches have been developed in recent years in order to improve the early detection of this neurological syndrome and, subsequently, the clinical care of affected patients. In this review, we briefly summarize the current understanding of cerebral malaria pathogenesis, compile the array of new biomarkers and tools available for diagnosis and research, and describe the emerging therapeutic approaches to tackle this pathology effectively.

Investigating the Pathogenesis of Severe Malaria: A Multidisciplinary and Cross-Geographical Approach

More than a century after the discovery of Plasmodium spp. parasites, the pathogenesis of severe malaria is still not well understood. The majority of malaria cases are caused by Plasmodium falciparum and Plasmodium vivax, which differ in virulence, red blood cell tropism, cytoadhesion of infected erythrocytes, and dormant liver hypnozoite stages. Cerebral malaria coma is one of the most severe manifestations of P. falciparum infection. Insights into its complex pathophysiology are emerging through a combination of autopsy, neuroimaging, parasite binding, and endothelial characterizations. Nevertheless, important questions remain regarding why some patients develop life-threatening conditions while the majority of P. falciparum-infected individuals do not, and why clinical presentations differ between children and adults. For P. vivax, there is renewed recognition of severe malaria, but an understanding of the factors influencing disease severity is limited and remains an important research topic. Shedding light on the underlying disease mechanisms will be necessary to implement effective diagnostic tools for identifying and classifying severe malaria syndromes and developing new therapeutic approaches for severe disease. This review highlights progress and outstanding questions in severe malaria pathophysiology and summarizes key areas of pathogenesis research within the International Centers of Excellence for Malaria Research program.

Brain swelling and death in children with cerebral malaria

BACKGROUND

Case fatality rates among African children with cerebral malaria remain in the range of 15 to 25%. The key pathogenetic processes and causes of death are unknown, but a combination of clinical observations and pathological findings suggests that increased brain volume leading to raised intracranial pressure may play a role. Magnetic resonance imaging (MRI) became available in Malawi in 2009, and we used it to investigate the role of brain swelling in the pathogenesis of fatal cerebral malaria in African children.

METHODS

We enrolled children who met a stringent definition of cerebral malaria (one that included the presence of retinopathy), characterized them in detail clinically, and obtained MRI scans on admission and daily thereafter while coma persisted.

RESULTS

Of 348 children admitted with cerebral malaria (as defined by the World Health Organization), 168 met the inclusion criteria, underwent all investigations, and were included in the analysis. A total of 25 children (15%) died, 21 of whom (84%) had evidence of severe brain swelling on MRI at admission. In contrast, evidence of severe brain swelling was seen on MRI in 39 of 143 survivors (27%). Serial MRI scans showed evidence of decreasing brain volume in the survivors who had had brain swelling initially.

CONCLUSIONS

Increased brain volume was seen in children who died from cerebral malaria but was uncommon in those who did not die from the disease, a finding that suggests that raised intracranial pressure may contribute to a fatal outcome. The natural history indicates that increased intracranial pressure is transient in survivors. (Funded by the National Institutes of Health and Wellcome Trust U.K.).

The pathogenesis of pediatric cerebral malaria: eye exams, autopsies, and neuroimaging

Several advances in our understanding of pediatric cerebral malaria (CM) have been made over the past 25 years. Accurate clinical diagnosis is enhanced by the identification of a characteristic retinopathy, visible by direct or indirect ophthalmoscopy, the retinal changes (retinal whitening, vessel color changes, white-centered hemorrhages) being consistently associated with intracerebral sequestration of parasites in autopsy studies. Autopsies have yielded information at tissue levels in fatal CM, but new insights into critical pathogenetic processes have emerged from neuroimaging studies, which, unlike autopsy-based studies, permit serial observations over time and allow comparisons between fatal cases and survivors. Brain swelling has emerged as the major risk factor for death, and, among survivors, brain volume diminishes spontaneously over 24-48 hours. Studies of life-threatening and fatal malaria are suggesting new approaches to identifying and caring for those at highest risk; potential adjuvants should be evaluated and implemented where they are most needed.

Magnetic resonance imaging during life: the key to unlock cerebral malaria pathogenesis?

Understanding the mechanisms underlying the pathophysiology of cerebral malaria in patients with Plasmodium falciparum infection is necessary to implement new curative interventions. While autopsy-based studies shed some light on several pathological events that are believed to be crucial in the development of this neurologic syndrome, their investigative potential is limited and has not allowed the identification of causes of death in patients who succumb to it. This can only be achieved by comparing features between patients who die from cerebral malaria and those who survive. In this review, several alternative approaches recently developed to facilitate the comparison of specific parameters between fatal, non-fatal cerebral malaria and uncomplicated malaria patients are described, as well as their limitations. The emergence of neuroimaging as a revolutionary tool in identifying critical structural and functional modifications of the brain during cerebral malaria is discussed and highly promising areas of clinical research using magnetic resonance imaging are highlighted.

Lactate transport and receptor actions in cerebral malaria

Cerebral malaria (CM), caused by Plasmodium falciparum infection, is a prevalent neurological disorder in the tropics. Most of the patients are children, typically with intractable seizures and high mortality. Current treatment is unsatisfactory. Understanding the pathogenesis of CM is required in order to identify therapeutic targets. Here, we argue that cerebral energy metabolic defects are probable etiological factors in CM pathogenesis, because malaria parasites consume large amounts of glucose metabolized mostly to lactate. Monocarboxylate transporters (MCTs) mediate facilitated transfer, which serves to equalize lactate concentrations across cell membranes in the direction of the concentration gradient. The equalizing action of MCTs is the basis for lactate’s role as a volume transmitter of metabolic signals in the brain. Lactate binds to the lactate receptor GPR81, recently discovered on brain cells and cerebral blood vessels, causing inhibition of adenylyl cyclase. High levels of lactate delivered by the parasite at the vascular endothelium may damage the blood–brain barrier, disrupt lactate homeostasis in the brain, and imply MCTs and the lactate receptor as novel therapeutic targets in CM.

Magnetic resonance imaging of the brain in adults with severe falciparum malaria

Background

Magnetic resonance imaging (MRI) allows detailed study of structural and functional changes in the brain in patients with cerebral malaria.

Methods

In a prospective observational study in adult Bangladeshi patients with severe falciparum malaria, MRI findings in the brain were correlated with clinical and laboratory parameters, retinal photography and optic nerve sheath diameter (ONSD) ultrasound (a marker of intracranial pressure).

Results

Of 43 enrolled patients, 31 (72%) had coma and 12 (28%) died. MRI abnormalities were present in 79% overall with mostly mild changes in a wide range of anatomical sites. There were no differences in MRI findings between patients with cerebral and non-cerebral or fatal and non-fatal disease. Subtle diffuse cerebral swelling was common (n = 22/43), but mostly without vasogenic oedema or raised intracranial pressure (ONSD). Also seen were focal extracellular oedema (n = 11/43), cytotoxic oedema (n = 8/23) and mildly raised brain lactate on magnetic resonance spectroscopy (n = 5/14). Abnormalities were much less prominent than previously described in Malawian children. Retinal whitening was present in 36/43 (84%) patients and was more common and severe in patients with coma.

Conclusion

Cerebral swelling is mild and not specific to coma or death in adult severe falciparum malaria. This differs markedly from African children. Retinal whitening, reflecting heterogeneous obstruction of the central nervous system microcirculation by sequestered parasites resulting in small patches of ischemia, is associated with coma and this process is likely important in the pathogenesis.

Cerebral malaria in children: using the retina to study the brain

Cerebral malaria is a dangerous complication of Plasmodium falciparum infection, which takes a devastating toll on children in sub-Saharan Africa. Although autopsy studies have improved understanding of cerebral malaria pathology in fatal cases, information about in vivo neurovascular pathogenesis is scarce because brain tissue is inaccessible in life. Surrogate markers may provide insight into pathogenesis and thereby facilitate clinical studies with the ultimate aim of improving the treatment and prognosis of cerebral malaria. The retina is an attractive source of potential surrogate markers for paediatric cerebral malaria because, in this condition, the retina seems to sustain microvascular damage similar to that of the brain. In paediatric cerebral malaria a combination of retinal signs correlates, in fatal cases, with the severity of brain pathology, and has diagnostic and prognostic significance. Unlike the brain, the retina is accessible to high-resolution, non-invasive imaging. We aimed to determine the extent to which paediatric malarial retinopathy reflects cerebrovascular damage by reviewing the literature to compare retinal and cerebral manifestations of retinopathy-positive paediatric cerebral malaria. We then compared retina and brain in terms of anatomical and physiological features that could help to account for similarities and differences in vascular pathology. These comparisons address the question of whether it is biologically plausible to draw conclusions about unseen cerebral vascular pathogenesis from the visible retinal vasculature in retinopathy-positive paediatric cerebral malaria. Our work addresses an important cause of death and neurodisability in sub-Saharan Africa. We critically appraise evidence for associations between retina and brain neurovasculature in health and disease, and in the process we develop new hypotheses about why these vascular beds are susceptible to sequestration of parasitized erythrocytes.

Host matrix metalloproteinases in cerebral malaria: new kids on the block against blood-brain barrier integrity?

Cerebral malaria (CM) is a life-threatening complication of falciparum malaria, associated with high mortality rates, as well as neurological impairment in surviving patients. Despite disease severity, the etiology of CM remains elusive. Interestingly, although the Plasmodium parasite is sequestered in cerebral microvessels, it does not enter the brain parenchyma: so how does Plasmodium induce neuronal dysfunction? Several independent research groups have suggested a mechanism in which increased blood–brain barrier (BBB) permeability might allow toxic molecules from the parasite or the host to enter the brain. However, the reported severity of BBB damage in CM is variable depending on the model system, ranging from mild impairment to full BBB breakdown. Moreover, the factors responsible for increased BBB permeability are still unknown. Here we review the prevailing theories on CM pathophysiology and discuss new evidence from animal and human CM models implicating BBB damage. Finally, we will review the newly-described role of matrix metalloproteinases (MMPs) and BBB integrity. MMPs comprise a family of proteolytic enzymes involved in modulating inflammatory response, disrupting tight junctions, and degrading sub-endothelial basal lamina. As such, MMPs represent potential innovative drug targets for CM.

Pediatric cerebral malaria: a scourge of Africa

Cerebral malaria, defined as an otherwise unexplained coma in a patient with Plasmodium falciparum parasitemia, affects up to 1 million people per year, the vast majority of them being children living in sub-Saharan Africa. Despite optimal treatment, this condition kills 15% of those affected and leaves 30% of survivors with neurologic sequelae. The clinical diagnosis is hampered by its poor specificity, but the presence or absence of a malarial retinopathy in cerebral malaria has proven to be important in the differentiation of underlying coma etiology. Both antimalarials and intense supportive care are necessary for optimal treatment. As of yet, clinical trials of adjunctive therapies have not improved the high rates of mortality and morbidity. Survivors are at high risk of neurologic sequelae including epilepsy, neurodisabilities and cognitive–behavioral problems. The neuroanatomic and functional bases of these sequelae are being elucidated. Although adjunctive therapy trials continue, the best hope for African children may lie in disease prevention. Strategies include bednets, chemoprophylaxis and vaccine development.

Protective role of brain water channel AQP4 in murine cerebral malaria

Tragically common among children in sub-Saharan Africa, cerebral malaria is characterized by rapid progression to coma and death. In this study, we used a model of cerebral malaria appearing in C57BL/6 WT mice after infection with the rodent malaria parasite Plasmodium berghei ANKA. Expression and cellular localization of the brain water channel aquaporin-4 (AQP4) was investigated during the neurological syndrome. Semiquantitative real-time PCR comparing uninfected and infected mice showed a reduction of brain AQP4 transcript in cerebral malaria, and immunoblots revealed reduction of brain AQP4 protein. Reduction of brain AQP4 protein was confirmed in cerebral malaria by quantitative immunogold EM; however, polarized distribution of AQP4 at the perivascular and subpial astrocyte membranes was not altered. To further examine the role of AQP4 in cerebral malaria, WT mice and littermates genetically deficient in AQP4 were infected with P. berghei. Upon development of cerebral malaria, WT and AQP4-null mice exhibited similar increases in width of perivascular astroglial end-feet in brain. Nevertheless, the AQP4-null mice exhibited more severe signs of cerebral malaria with greater brain edema, although disruption of the blood-brain barrier was similar in both groups. In longitudinal studies, cerebral malaria appeared nearly 1 d earlier in the AQP4-null mice, and reduced survival was noted when chloroquine rescue was attempted. We conclude that the water channel AQP4 confers partial protection against cerebral malaria.

Acute brain MRI findings in 120 Malawian children with cerebral malaria: new insights into an ancient disease

BACKGROUND AND PURPOSE

There have been few neuroimaging studies of pediatric CM, a common often fatal tropical condition. We undertook a prospective study of pediatric CM to better characterize the MRI features of this syndrome, comparing findings in children meeting a stringent definition of CM with those in a control group who were infected with malaria but who were likely to have a nonmalarial cause of coma.

MATERIALS AND METHODS

Consecutive children admitted with traditionally defined CM (parasitemia, coma, and no other coma etiology evident) were eligible for this study. The presence or absence of malaria retinopathy was determined. MRI findings in children with ret+ CM (patients) were compared with those with ret- CM (controls). Two radiologists blinded to retinopathy status jointly developed a scoring procedure for image interpretation and provided independent reviews. MRI findings were compared between patients with and without retinopathy, to assess the specificity of changes for patients with very strictly defined CM.

RESULTS

Of 152 children with clinically defined CM, 120 were ret+, and 32 were ret-. Abnormalities much more common in the patients with ret+ CM were markedly increased brain volume; abnormal T2 signal intensity; and DWI abnormalities in the cortical, deep gray, and white matter structures. Focal abnormalities rarely respected arterial vascular distributions. Most of the findings in the more clinically heterogeneous ret- group were normal, and none of the abnormalities noted were more prevalent in controls.

CONCLUSIONS

Distinctive MRI findings present in patients meeting a stringent definition of CM may offer insights into disease pathogenesis and treatment.

The Impact of HIV Coinfection on Cerebral Malaria Pathogenesis

HIV infection is widespread throughout the world and is especially prevalent in sub-Saharan Africa and Asia. Similarly, Plasmodium falciparum, the most common cause of severe malaria, affects large areas of sub-Saharan Africa, the Indian subcontinent, and Southeast Asia. Although initial studies suggested that HIV and malaria had independent impact upon patient outcomes, recent studies have indicated a more significant interaction. Clinical studies have shown that people infected with HIV have more frequent and severe episodes of malaria, and parameters of HIV disease progression worsen in individuals during acute malaria episodes. However, the effect of HIV on development of cerebral malaria, a manifestation of P. falciparum infection that is frequently fatal, has not been characterized. We review clinical and basic science studies pertaining to HIV and malaria coinfection and cerebral malaria in particular in order to highlight the likely role HIV plays in exacerbating cerebral malaria pathogenesis.

Cerebral malaria: mysteries at the blood-brain barrier

Cerebral malaria is the most severe pathology caused by the malaria parasite, Plasmodium falciparum. The pathogenic mechanisms leading to cerebral malaria are still poorly defined as studies have been hampered by limited accessibility to human tissues. Nevertheless, histopathology of post-mortem human tissues and mouse models of cerebral malaria have indicated involvement of the blood-brain barrier in cerebral malaria. In contrast to viruses and bacteria, malaria parasites do not infiltrate and infect the brain parenchyma. Instead, rupture of the blood-brain barrier occurs and may lead to hemorrhages resulting in neurological alterations. Here, we review the most recent findings from human studies and mouse models on the interactions of malaria parasites and the blood-brain barrier, shedding light on the pathogenesis of cerebral malaria, which may provide directions for possible interventions.

Coma in fatal adult human malaria is not caused by cerebral oedema

BACKGROUND

The role of brain oedema in the pathophysiology of cerebral malaria is controversial. Coma associated with severe Plasmodium falciparum malaria is multifactorial, but associated with histological evidence of parasitized erythrocyte sequestration and resultant microvascular congestion in cerebral vessels. To determine whether these changes cause breakdown of the blood-brain barrier and resultant perivascular or parenchymal cerebral oedema, histology, immunohistochemistry and image analysis were used to define the prevalence of histological patterns of oedema and the expression of specific molecular pathways involved in water balance in the brain in adults with fatal falciparum malaria.

METHODS

The brains of 20 adult Vietnamese patients who died of severe malaria were examined for evidence of disrupted vascular integrity. Immunohistochemistry and image analysis was performed on brainstem sections for activation of the vascular endothelial growth factor (VEGF) receptor 2 and expression of the aquaporin 4 (AQP4) water channel protein. Fibrinogen immunostaining was assessed as evidence of blood-brain barrier leakage and perivascular oedema formation. Correlations were performed with clinical, biochemical and neuropathological parameters of severe malaria infection.

RESULTS

The presence of oedema, plasma protein leakage and evidence of VEGF signalling were heterogeneous in fatal falciparum malaria and did not correlate with pre-mortem coma. Differences in vascular integrity were observed between brain regions with the greatest prevalence of disruption in the brainstem, compared to the cortex or midbrain. There was a statistically non-significant trend towards higher AQP4 staining in the brainstem of cases that presented with coma (P = .02).

CONCLUSIONS

Histological evidence of cerebral oedema or immunohistochemical evidence of localised loss of vascular integrity did not correlate with the occurrence of pre-mortem coma in adults with fatal falciparum malaria. Enhanced expression of AQP4 water channels in the brainstem may, therefore, reflect a mix of both neuropathological or attempted neuroprotective responses to oedema formation.

Nitric oxide for the adjunctive treatment of severe malaria: hypothesis and rationale

We hypothesize that supplemental inhaled nitric oxide (iNO) will improve outcomes in children with severe malaria receiving standard antimalarial therapy. The rationale for the hypothesized efficacy of iNO rests on: (1) biological plausibility, based on known actions of NO in modulating endothelial activation; (2) pre-clinical efficacy data from animal models of experimental cerebral malaria; and (3) a human trial of the NO precursor l-arginine, which improved endothelial function in adults with severe malaria. iNO is an attractive new candidate for the adjunctive treatment of severe malaria, given its proven therapeutic efficacy in animal studies, track record of safety in clinical practice and numerous clinical trials, inexpensive manufacturing costs, and ease of administration in settings with limited healthcare infrastructure. We plan to test this hypothesis in a randomized controlled trial (ClinicalTrials.gov Identifier: NCT01255215).

The neuropathology of fatal cerebral malaria in malawian children

We examined the brains of 50 Malawian children who satisfied the clinical definition of cerebral malaria (CM) during life; 37 children had sequestration of infected red blood cells (iRBCs) and no other cause of death, and 13 had a nonmalarial cause of death with no cerebral sequestration. For comparison, 18 patients with coma and no parasitemia were included. We subdivided the 37 CM cases into two groups based on the cerebral microvasculature pathology: iRBC sequestration only (CM1) or sequestration with intravascular and perivascular pathology (CM2). We characterized and quantified the axonal and myelin damage, blood-brain barrier (BBB) disruption, and cellular immune responses and correlated these changes with iRBC sequestration and microvascular pathology. Axonal and myelin damage was associated with ring hemorrhages and vascular thrombosis in the cerebral and cerebellar white matter and brainstem of the CM2 cases. Diffuse axonal and myelin damage were present in CM1 and CM2 cases in areas of prominent iRBC sequestration. Disruption of the BBB was associated with ring hemorrhages and vascular thrombosis in CM2 cases and with sequestration in both CM1 and CM2 groups. Monocytes with phagocytosed hemozoin accumulated within microvessels containing iRBCs in CM2 cases but were not present in the adjacent neuropil. These findings are consistent with a link between iRBC sequestration and intravascular and perivascular pathology in fatal pediatric CM, resulting in myelin damage, axonal injury, and breakdown of the BBB.

In the eye of experimental cerebral malaria

Cerebral malaria is the most severe complication of Plasmodium falciparum infection, accounting for 1 million deaths per year. We characterized the murine disease using in vivo magnetic resonance imaging (MRI) at 4.7 T, proving that ischemic edema is responsible for fatality. The aim of the present study was to identify early markers of experimental cerebral malaria using very high field conventional MRI (11.75 T). CBA/J mice infected with Plasmodium berghei ANKA were observed at an early stage of the disease, before the onset of detectable brain swelling and at the most acute stage of cerebral malaria. Herein, we report the first detection of damage to the optic and trigeminal nerves on T(2)-weighted MRI. The trigeminal nerves appeared hypointense, with significantly reduced diameter and cross-sectional area. The optic nerves were hypointense and often not visible. In addition, the internerve distance between the optic nerves was significantly and progressively reduced between the early and severest stages. Cranial nerve injury was the earliest anatomic hallmark of the disease, visible before brain edema became detectable. Thus, cranial nerve damage may manifest in neurologic signs, which may assist in the early recognition of cerebral malaria.

Mannitol and other osmotic diuretics as adjuncts for treating cerebral malaria

BACKGROUND

Cerebral oedema occurs with cerebral malaria, and some clinicians think osmotic diuretics, such as mannitol or urea, may improve outcomes.

OBJECTIVES

To compare mannitol or urea to placebo or no diuretic for treating children or adults with cerebral malaria.

SEARCH STRATEGY

We searched the Cochrane Infectious Diseases Group Specialized Register (Issue 4, 2010), CENTRAL (The Cochrane Library Issue 12, 2010), MEDLINE (1966 to November 2010), EMBASE (1974 to November 2010), LILACS (1982 to November 2010), and the reference lists of articles. We contacted relevant organizations and researchers.

SELECTION CRITERIA

Randomized or quasi-randomized controlled trials comparing mannitol or urea to placebo or no treatment in children and adults with cerebral malaria. Primary outcomes were death, life-threatenining sequelae and major neurological sequelae at six months.

DATA COLLECTION AND ANALYSIS

Two authors applied the inclusion criteria, assessed risk of bias, and extracted data independently.

MAIN RESULTS

One trial met the inclusion criteria, comparing mannitol 20% to saline placebo in 156 Ugandan children. Allocation was concealed. No difference in mortality, time to regain consciousness, or neurological sequelae were detected.

AUTHORS' CONCLUSIONS

There are insufficient data to know what the effects of osmotic diuretics are in children with cerebral malaria. Larger, multicentre trials are needed.

Ultrasound findings in Plasmodium falciparum malaria: a pilot study

OBJECTIVE

To investigate whether hand-carried ultrasound technology may be valuable in the assessment of children with acute malaria. Every year, approximately 800,000 children under the age of 5 yrs die of complications of Plasmodium falciparum malaria infection. The advent of hand-carried ultrasound technology has made diagnostic ultrasonography possible in underresourced settings.

DESIGN

We performed a pilot observational study collecting clinical data and performing ultrasound examinations on children diagnosed with P. falciparum malaria infection. The targeted ultrasound examination included measurement of optic nerve sheath diameter, color transcranial Doppler insonation of the cerebral vasculature, cardiac ultrasound, and abdominal ultrasound.

SETTING

Pediatric acute care unit of Mulago Hospital in Kampala, Uganda.

PATIENTS

Thirty-three hospitalized children between the ages of 6 months and 12 yrs with documented acute P. falciparum infection.

INTERVENTION

Targeted bedside ultrasound examination.

MEASUREMENTS AND MAIN RESULTS

Increased optic nerve sheath diameter was observed in one third of all patients with malaria and in 100% of the patients diagnosed with cerebral malaria. Although higher-than-normal cerebral blood flow velocities were demonstrated in three (25%) of 12 patients with severe anemia, most patients demonstrated a normal cerebral blood flow velocity, suggesting a blunted response to anemia. We did not find evidence of pulmonary hypertension by cardiac ultrasound, and cardiac function did not seem depressed, even among patients with severe anemia and lactic acidosis. Finally, spleen size as determined by palpation significantly overestimated the true incidence of splenomegaly as measured by ultrasound (48% and 24%, respectively).

CONCLUSIONS

A targeted ultrasound examination focusing on optic nerve sheath diameter, color transcranial Doppler, cardiac ultrasound, and spleen size may prove useful for patient classification, risk stratification, research studies, and treatment monitoring in pediatric malaria. More studies should be done.

Contribution of allergic inflammatory response to the pathogenesis of malaria disease

Plasmodium falciparum, the aetiological agent of human lethal malaria, is responsible for over 2 million deaths per year and malaria episodes may vary considerably in their severity and clinical manifestations. Dysregulated balance of the inflammatory response and a defect in the anti-Plasmodium parasite immune response represent the hallmarks of malaria disease. Among the many possible mechanisms, it is now widely recognized that the production of pro-inflammatory mediators and cytokines and upregulation of endothelial cell adhesion molecules play important roles in malaria pathogenesis. We and others provided evidence that some components of allergic inflammatory response to malaria parasites or elicited by by-products of parasite infection may contribute to malaria pathogenesis. This review provides some clue regarding these mechanisms where mast cells and histamine, an inflammatory mediator generated following IgE-independent or IgE-mediated immune response, were found to play a major role in parasite transmission and malaria pathogenesis, respectively. This article is part of a Special Issue entitled: Mast cells in inflammation.

Cerebral malaria: mechanisms of brain injury and strategies for improved neurocognitive outcome

Cerebral malaria is the most severe neurological complication of infection with Plasmodium falciparum. With >575,000 cases annually, children in sub-Saharan Africa are the most affected. Surviving patients have an increased risk of neurological and cognitive deficits, behavioral difficulties, and epilepsy making cerebral malaria a leading cause of childhood neurodisability in the region. The pathogenesis of neurocognitive sequelae is poorly understood: coma develops through multiple mechanisms and there may be several mechanisms of brain injury. It is unclear how an intravascular parasite causes such brain injury. Understanding these mechanisms is important to develop appropriate neuroprotective interventions. This article examines possible mechanisms of brain injury in cerebral malaria, relating this to the pathogenesis of the disease, and explores prospects for improved neurocognitive outcome.

Atypical brain response to novelty in rural African children with a history of severe falciparum malaria

Plasmodium falciparum is the most common parasitic infection of the central nervous system causing neuro-cognitive deficits in 5-26% of paediatric cases. The burden cannot be reliably estimated because of lack of sensitive, culture-fair and robust assessments in rural settings. Auditory and visual brain event related potentials (ERPs) are used to compare novelty processing in children exposed to severe malaria with community controls. Fifty children previously admitted and discharged from Kilifi District Hospital with severe falciparum malaria were selected and compared with 77 unexposed age matched children. The results showed that up to 14% of children exposed to severe malaria had significantly different responses to novelty compared to unexposed children. Children exposed to severe malaria had smaller P3a amplitudes to novelty in both auditory [F (3, 119)=4.545, p=0.005] and visual [F (3, 119)=6.708, p<0.001] paradigms compared to unexposed children. In the auditory domain the differences in processing of novelty were not related to early component processing. The percentage of children with severe malaria showing impaired performance using ERPs is within the range previously reported using neuropsychological tests. The overall pattern suggests that severe malaria affects prefrontal and temporal cortices normally activated by stimulus novelty.

Neuroimaging findings in children with retinopathy-confirmed cerebral malaria

PURPOSE

To describe brain CT findings in retinopathy-confirmed, paediatric cerebral malaria.

MATERIALS AND METHODS

In this outcomes study of paediatric cerebral malaria, a subset of children with protracted coma during initial presentation was scanned acutely. Survivors experiencing adverse neurological outcomes also underwent a head CT. All children had ophthalmological examination to confirm the presence of the retinopathy specific for cerebral malaria. Independent interpretation of CT images was provided by two neuroradiologists.

RESULTS

Acute brain CT findings in three children included diffuse oedema with obstructive hydrocephalus (2), acute cerebral infarctions in multiple large vessel distributions with secondary oedema and herniation (1), and oedema of thalamic grey matter (1). One child who was reportedly normal prior to admission had parenchymal atrophy suggestive of pre-existing CNS injury. Among 56 survivors (9-84 months old), 15 had adverse neurologic outcomes-11/15 had a follow-up head CT, 3/15 died and 1/15 refused CT. Follow-up head CTs obtained 7-18 months after the acute infection revealed focal and multifocal lobar atrophy correlating to regions affected by focal seizures during the acute infection (5/11). Other findings were communicating hydrocephalus (2/11), vermian atrophy (1/11) and normal studies (3/11).

CONCLUSIONS

The identification of pre-existing imaging abnormalities in acute cerebral malaria suggests that population-based studies are required to establish the rate and nature of incidental imaging abnormalities in Malawi. Children with focal seizures during acute cerebral malaria developed focal cortical atrophy in these regions at follow-up. Longitudinal studies are needed to further elucidate mechanisms of CNS injury and death in this common fatal disease.

Murine cerebral malaria is associated with a vasospasm-like microcirculatory dysfunction, and survival upon rescue treatment is markedly increased by nimodipine

Brain hemodynamics in cerebral malaria (CM) is poorly understood, with apparently conflicting data showing microcirculatory hypoperfusion and normal or even increased blood flow in large arteries. Using intravital microscopy to assess the pial microvasculature through a closed cranial window in the murine model of CM by Plasmodium berghei ANKA, we show that murine CM is associated with marked decreases (mean: 60%) of pial arteriolar blood flow attributable to vasoconstriction and decreased blood velocity. Leukocyte sequestration further decreased perfusion by narrowing luminal diameters in the affected vessels and blocking capillaries. Remarkably, vascular collapse at various degrees was observed in 44% of mice with CM, which also presented more severe vasoconstriction. Coadministration of artemether and nimodipine, a calcium channel blocker used to treat postsubarachnoid hemorrhage vasospasm, to mice presenting CM markedly increased survival compared with artemether plus vehicle only. Administration of nimodipine induced vasodilation and increased pial blood flow. We conclude that vasoconstriction and vascular collapse play a role in murine CM pathogenesis and nimodipine holds potential as adjunctive therapy for CM.

MRI findings of cerebral malaria. A report of two cases

Cerebral malaria is a protozoal disease affecting the brain caused by Plasmodium falciparum. The hallmark of cerebral malaria is progressive decline in the sensorium leading to coma and in some cases death. MR findings reported in cerebral malaria are diffuse cerebral swelling / edema, bilateral nearly symmetrical T2 hyperintense lesions in basal ganglia and similar lesions in thalamus, pons and cerebellum. The imaging findings of cerebral malaria depend on the duration of the illness and time of MR examination. We describe two patients of cerebral malaria having mixed Plasmodium falciparum and Plasmodium vivex infestation showing bilateral basal ganglia infarcts with cerebral swelling in one patient and bilateral basal ganglia and cerebellar lesions in the other.

Diagnosis and management of the neurological complications of falciparum malaria

Malaria is a major public health problem in the developing world owing to its high rates of morbidity and mortality. Of all the malarial parasites that infect humans, Plasmodium falciparum is most commonly associated with neurological complications, which manifest as agitation, psychosis, seizures, impaired consciousness and coma (cerebral malaria). Cerebral malaria is the most severe neurological complication; the condition is associated with mortality of 15-20%, and a substantial proportion of individuals with this condition develop neurocognitive sequelae. In this Review, we describe the various neurological complications encountered in malaria, discuss the underlying pathogenesis, and outline current management strategies for these complications. Furthermore, we discuss the role of adjunctive therapies in improving outcome.