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

Efficacy and safety evaluation of a novel trioxaquine in the management of cerebral malaria in a mouse model

Background

The emergence of multidrug-resistant strains of Plasmodium falciparum poses a great threat of increased fatalities in cases of cerebral and other forms of severe malaria infections in which parenteral artesunate monotherapy is the current drug of choice. The study aimed to investigate in a mouse model of human cerebral malaria whether a trioxaquine chemically synthesized by covalent linking of a 4,7-dichloroquinoline pharmacophore to artesunate through a recent drug development approach termed ‘covalent bitherapy’ could improve the curative outcomes in cerebral malaria infections.

Methods

Human cerebral malaria rodent model, the C57BL/6 male mice were infected intraperitoneally (ip) with Plasmodium berghei ANKA and intravenously (iv) treated with the trioxaquine from day 8 post-infection (pi) at 12.5 and 25 mg/kg, respectively, twice a day for 3 days. Treatments with the trioxaquine precursors (artesunate and 4,7-dichloroquine), and quinine were also included as controls. In vivo safety evaluation for the trioxaquine was done according to Organization for Economic Co-operation and Development (OECD) guidelines 423, where female Swiss albino mice were orally administered with either 300 or 2000 mg/kg of the trioxaquine and monitored for signs of severity, and or mortality for 14 days post-treatment.

Results

The trioxaquine showed a potent and a rapid antiplasmodial activity with 80% parasite clearance in the first 24 h for the two dosages used. Long-term parasitaemia monitoring showed a total parasite clearance as the treated mice survived beyond 60 days post-treatment, with no recrudescence observed. Artesunate treated mice showed recrudescence 8 days post-treatment, with all mice in this group succumbing to the infection. Also, 4,7-dichloroquinoline and quinine did not show any significant parasitaemia suppression in the first 24 h post-treatment, with the animals succumbing to the infection.

Conclusion

Covalent bitherapy proves to be a viable source of urgently needed new anti-malarials for management of cerebral malaria, and this polypharmacology approach could be a potential strategy to protect artesunate from parasite resistance and in potentially improving clinical outcomes in severe forms of malaria infections.

IL-33 receptor ST2 regulates the cognitive impairments associated with experimental cerebral malaria

Cerebral malaria (CM) is associated with a high mortality rate and long-term neurocognitive impairment in survivors. The murine model of experimental cerebral malaria (ECM) induced by Plasmodium berghei ANKA (PbA)-infection reproduces several of these features. We reported recently increased levels of IL-33 protein in brain undergoing ECM and the involvement of IL-33/ST2 pathway in ECM development. Here we show that PbA-infection induced early short term and spatial memory defects, prior to blood brain barrier (BBB) disruption, in wild-type mice, while ST2-deficient mice did not develop cognitive defects. PbA-induced neuroinflammation was reduced in ST2-deficient mice with low Ifng, Tnfa, Il1b, Il6, CXCL9, CXCL10 and Cd8a expression, associated with an absence of neurogenesis defects in hippocampus. PbA-infection triggered a dramatic increase of IL-33 expression by oligodendrocytes, through ST2 pathway. In vitro, IL-33/ST2 pathway induced microglia expression of IL-1β which in turn stimulated IL-33 expression by oligodendrocytes. These results highlight the IL-33/ST2 pathway ability to orchestrate microglia and oligodendrocytes responses at an early stage of PbA-infection, with an amplification loop between IL-1β and IL-33, responsible for an exacerbated neuroinflammation context and associated neurological and cognitive defects.

The cerebral complication of malaria caused by Plasmodium falciparum infection, is associated with long-term neurological sequelae in survivors. The mechanisms involved in neurocognitive impairments during cerebral malaria development are still unknown. We reported recently the essential role of IL-33/ST2 pathway in experimental cerebral malaria (ECM) development. In this study we investigated the capacity of IL-33, highly expressed in oligodendrocytes, to promote ECM-associated neurological and cognitive damages. We found that IL-33/ST2 pathway through glial cells is involved in neurocognitive impairments, associated with exacerbated neuroinflammation, and altered neurogenesis. Interestingly, the implication of glial cells with a high level of IL-33 production in neurocognitive disorders, occurs at an early stage of ECM development, prior to blood brain barrier permeabilization. We propose the link between microglial IL-1β and oligodendrocytes IL-33 production in neurological symptoms associated with ECM.

Extensive alterations of blood metabolites in pediatric cerebral malaria

Cerebral malaria (CM) presents as an encephalopathy and is due to infection with Plasmodium falciparum. Patients are comatose, often with fever, recurrent seizures and this condition is associated with a high mortality rate. The etiology of the coma and seizures are poorly understood. Circulating small molecules and lipids have bioactive functions and alterations in their concentrations have been implicated in seizure disorders and other forms of encephalopathy. We carried out a comprehensive analysis of blood metabolites during CM to explore a biochemical basis of this encephalopathy. A paired metabolomics analysis was performed on the plasma samples of Malawian children (n = 11) during CM and at convalescence thirty days later, to identify differentially abundant molecules associated with CM. We also report plasma molecules associated with CM mortality (n = 4) compared to survival (n = 19). Plasma metabolites were identified through ultra high performance liquid chromatography/tandem mass spectrometry and gas chromatography/mass spectrometry to maximize compound detection and accuracy and then compared to a library for identification. We detected a total of 432 small molecules in the plasma and 247 metabolites were significantly differentially abundant between CM and convalescence (p < 0.05, FDR < 0.10). These represented global changes across many classes of molecules including lipids, amino acids and hemoglobin metabolites. We observed significant changes in molecules that could impact neurologic function during CM; these include increased levels of kynurenate and decreased indolepropionate, glutamate, arginine and glutamine. Moreover, 1-methylimidazoleacetate, kyurenate, arachidonic acid and dimethylarginine were associated with mortality (p < 0.05, fold change > 1.2). These results highlight the broad changes in blood chemistry during CM. We have identified metabolites that may impact central nervous system physiology and disease outcomes and can be further explored for their mechanistic roles into the pathophysiology of CM.

Does promoting resolution instead of inhibiting inflammation represent the new paradigm in treating infections?

Infections arise when the host response is overwhelmed by pathogens leading to organ dysfunction. In some instances patients progress to more severe conditions, including septic shock, that are associated with increased mortality. Current strategies in treating infections aim at either blocking inflammation using inhibitors to pro-inflammatory molecules and/or inhibiting bacterial growth using antibiotics. These approaches find their origins in studies conducted by Joseph Lister who demonstrated that applying carbolic acid to wounds promoted wound healing without suppuration, reducing both the necessity of amputation and mortality. While this approach is still applicable to certain infections, inhibition of the immune response is also associated with increased mortality, especially in septic patients. In many instances sepsis survivors succumb later to persistent, recurrent, nosocomial and secondary infections. This, together with a rise in resistance to many frontline antibiotics, has prompted a search for alternative ways to treat infections. Recent studies investigating processes engaged by the host response during self-resolving infections identified a novel group of mediators, termed as specialized pro-resolving mediators (SPM). These molecules, produced via the enzymatic conversion of essential fatty acids, actively reprogram the immune response to promote clearance of invading pathogens, and counter-regulate the production of inflammation-initiating molecules. Furthermore, recent studies also demonstrate that these mediators promote tissue repair and regeneration, essential processes in the re-establishment of barrier and prevention of re-infection. The scope of the present review is to discuss the evidence underpinning the endogenous protective roles of these novel mediators, as well as the evidence demonstrating that dysregulation in their production and actions contribute to disease pathogenesis in infections. This review will also discuss the potential of resolution pharmacology-based approaches in developing new therapeutics for combatting infections that do not interfere with the immune response.

Neurodevelopment: The Impact of Nutrition and Inflammation During Early to Middle Childhood in Low-Resource Settings

The early to middle childhood years are a critical period for child neurodevelopment. Nutritional deficiencies, infection, and inflammation are major contributors to impaired child neurodevelopment in these years, particularly in low-resource settings. This review identifies global research priorities relating to nutrition, infection, and inflammation in early to middle childhood neurodevelopment. The research priority areas identified include: (1) assessment of how nutrition, infection, or inflammation in the preconception, prenatal, and infancy periods (or interventions in these periods) affect function in early to middle childhood; (2) assessment of whether effects of nutritional interventions vary by poverty or inflammation; (3) determination of the feasibility of preschool- and school-based integrated nutritional interventions; (4) improved assessment of the epidemiology of infection- and inflammation-related neurodevelopmental impairment (NDI); (5) identification of mechanisms through which infection causes NDI; (6) identification of noninfectious causes of inflammation-related NDI and interventions for causes already identified (eg, environmental factors); and (7) studies on the effects of interactions between nutritional, infectious, and inflammatory factors on neurodevelopment in early to middle childhood. Areas of emerging importance that require additional study include the effects of maternal Zika virus infection, childhood environmental enteropathy, and alterations in the child's microbiome on neurodevelopment in early to middle childhood. Research in these key areas will be critical to the development of interventions to optimize the neurodevelopmental potential of children worldwide in the early to middle childhood years.

Review: the Multiple Roles of Monocytic Microparticles

Monocytic microparticles (mMP) are microparticles derived from human monocytes either under in vivo or in vitro conditions. The size of mMP is between 0.1 and 1.0 μm. Apart from the size range, mMPs are also identified based on phosphatidylserine and CD14 expression on their surface, though this is not always the case. Monocytic MP are critical players in inflammation, endothelial cell function, and blood coagulation. They exhibit dual function by either helping the progression of such conditions or limiting it, depending on certain factors. Furthermore, the numbers of mMP are elevated in some autoimmune diseases, infectious diseases, and metabolic disorders. However, it is unknown whether mMP play an active role in these diseases or are simply biomarkers. The mechanism of mMP modulation is yet to be identified. In this review, we highlight the mechanism of mMP formation and the roles that they play in inflammation, blood coagulation, and different disease settings.

Cerebral malaria: insight into pathogenesis, complications and molecular biomarkers

Cerebral malaria is a medical emergency. All patients with Plasmodium falciparum malaria with neurologic manifestations of any degree should be urgently treated as cases of cerebral malaria. Pathogenesis of cerebral malaria is due to damaged vascular endothelium by parasite sequestration, inflammatory cytokine production and vascular leakage, which result in brain hypoxia, as indicated by increased lactate and alanine concentrations. The levels of the biomarkers’ histidine-rich protein II, angiopoietin-Tie-2 system and plasma osteoprotegrin serve as diagnostic and prognostic markers. Brain imaging may show neuropathology around the caudate and putamen. Mortality is high and patients who survive sustain brain injury which manifests as long-term neurocognitive impairments.

Brain-derived Neurotrophic Factor Is Associated With Disease Severity and Clinical Outcome in Ugandan Children Admitted to Hospital With Severe Malaria

BACKGROUND

Malaria remains a leading cause of childhood death and neurologic disability in sub-Saharan Africa. Here, we test the hypothesis that malaria-induced alterations to circulating brain-derived neurotrophic factor (BDNF) are associated with poor clinical outcomes in children with severe malaria.

METHODS

We quantified BDNF (by enzyme-linked immunosorbent assay) in plasma samples collected [at presentation (day 1), day 3 and day 14], during a prospective study of Ugandan children admitted to hospital with severe malaria (n = 179).

RESULTS

BDNF concentration at presentation (day 1) was lower in children with cerebral malaria (P < 0.01), coma (P < 0.01), Lambaréné Organ Dysfunction Score >1 (P < 0.05) and respiratory distress (P < 0.01). Higher BDNF concentration at presentation was associated with shorter time to coma recovery [hazard ratio = 1.655 (1.194-2.293); P = 0.002] and a reduced odds ratio of disability [0.50 (0.27-0.94); P = 0.047] and death [0.45 (0.22-0.92); P = 0.035]. BDNF concentration was lower on day 1 and increased in children surviving severe malaria (day 14; P < 0.0001).

CONCLUSIONS

Our findings provide the new evidence linking circulating BDNF with disease severity, coma recovery and clinical outcome in children with severe malaria.

A Hospital-Based Retrospective Comparative Study of Complications, Outcomes, Clinical and Laboratory Parameters of Malaria with and without Neurological Involvement

Background & Objectives

Classically associated with Plasmodium (P.) falciparum, neurological complications in severe malaria is associated with increased morbidity and mortality. However, reports implicate the long considered benign P. vivax for causing severe malaria as well. We aimed to analyse the cerebral complications in malaria, and study if there is a species-related difference in the presentation and outcomes.

Methods

We retrospectively compared patients with malaria hospitalised from 2009–15, with (n=105) and without (n=1155) neurological involvement regarding outcomes, complications, demographic attributes, clinical features, and laboratory parameters. Subsequently, the same parameters were studied in those with cerebral malaria due to mono-infections of P. vivax or P. falciparum and their co-infection.

Results

Cerebral malaria was observed in 8.3% (58/696), 7.4% (38/513) and 17.6% (6/51) of P. vivax, P. falciparum and combined plasmodial infections respectively. Those with cerebral malaria had significantly (p<0.05) longer hospitalisation, delayed defervescence, required mechanical ventilatory support and dialysis despite comparable levels of azotemia and renal insufficiency, and adverse outcomes compared to non-cerebral malaria. Severe thrombocytopenia, respiratory distress and mechanical ventilation were significantly (p<0.05) associated with P. vivax cerebral malaria.

Conclusions

The plasmodial species are comparable in clinical and laboratory parameters and outcomes in cerebral malaria in isolation and combination (p>0.05). P. vivax is emerging as the predominant cause of cerebral malaria, and its virulence is comparable to P. falciparum.

Transcriptomic profiling of microglia reveals signatures of cell activation and immune response, during experimental cerebral malaria

Cerebral malaria is a pathology involving inflammation in the brain. There are many immune cell types activated during this process, but there is little information on the response of microglia, in this severe complication. We examined microglia by genome wide transcriptomic analysis in a model of experimental cerebral malaria (ECM), in which C57BL/6 mice are infected with Plasmodium berghei ANKA. Thousands of transcripts were differentially expressed in microglia at two different time points during infection. Proliferation of microglia was a dominant feature before the onset of ECM, and supporting this, we observed an increase in numbers of these cells in the brain. When cerebral malaria symptoms were manifest, genes involved in immune responses and chemokine production were upregulated, which were possibly driven by Type I Interferon. Consistent with this hypothesis, in vitro culture of a microglial cell line with Interferon-β, but not infected red blood cells, resulted in production of several of the chemokines shown to be upregulated in the gene expression analysis. It appears that these responses are associated with ECM, as microglia from mice infected with a mutant P. berghei parasite (ΔDPAP3), which does not cause ECM, did not show the same level of activation or proliferation.

EPCR and Malaria Severity: The Center of a Perfect Storm

Severe malaria due to Plasmodium falciparum infection causes nearly half a million deaths per year. The different symptomatology and disease manifestations among patients have hampered understanding of severe malaria pathology and complicated efforts to develop targeted disease interventions. Infected erythrocyte sequestration in the microvasculature plays a critical role in the development of severe disease, and there is increasing evidence that cytoadherent parasites interact with host factors to enhance the damage caused by the parasite. The recent discovery that parasite binding to endothelial protein C receptor (EPCR) is associated with severe disease has suggested new mechanisms of pathology and provided new avenues for severe malaria adjunctive therapy research.

Exploring experimental cerebral malaria pathogenesis through the characterisation of host-derived plasma microparticle protein content

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection responsible for thousands of deaths in children in sub-Saharan Africa. CM pathogenesis remains incompletely understood but a number of effectors have been proposed, including plasma microparticles (MP). MP numbers are increased in CM patients’ circulation and, in the mouse model, they can be localised within inflamed vessels, suggesting their involvement in vascular damage. In the present work we define, for the first time, the protein cargo of MP during experimental cerebral malaria (ECM) with the overarching hypothesis that this characterisation could help understand CM pathogenesis. Using qualitative and quantitative high-throughput proteomics we compared MP proteins from non-infected and P. berghei ANKA-infected mice. More than 360 proteins were identified, 60 of which were differentially abundant, as determined by quantitative comparison using TMT^TM isobaric labelling. Network analyses showed that ECM MP carry proteins implicated in molecular mechanisms relevant to CM pathogenesis, including endothelial activation. Among these proteins, the strict association of carbonic anhydrase I and S100A8 with ECM was verified by western blot on MP from DBA/1 and C57BL/6 mice. These results demonstrate that MP protein cargo represents a novel ECM pathogenic trait to consider in the understanding of CM pathogenesis.

Non-invasive Monitoring of Intracranial Pressure Using Transcranial Doppler Ultrasonography: Is It Possible?

Although intracranial pressure (ICP) is essential to guide management of patients suffering from acute brain diseases, this signal is often neglected outside the neurocritical care environment. This is mainly attributed to the intrinsic risks of the available invasive techniques, which have prevented ICP monitoring in many conditions affecting the intracranial homeostasis, from mild traumatic brain injury to liver encephalopathy. In such scenario, methods for non-invasive monitoring of ICP (nICP) could improve clinical management of these conditions. A review of the literature was performed on PUBMED using the search keywords 'Transcranial Doppler non-invasive intracranial pressure.' Transcranial Doppler (TCD) is a technique primarily aimed at assessing the cerebrovascular dynamics through the cerebral blood flow velocity (FV). Its applicability for nICP assessment emerged from observation that some TCD-derived parameters change during increase of ICP, such as the shape of FV pulse waveform or pulsatility index. Methods were grouped as: based on TCD pulsatility index; aimed at non-invasive estimation of cerebral perfusion pressure and model-based methods. Published studies present with different accuracies, with prediction abilities (AUCs) for detection of ICP ≥20 mmHg ranging from 0.62 to 0.92. This discrepancy could result from inconsistent assessment measures and application in different conditions, from traumatic brain injury to hydrocephalus and stroke. Most of the reports stress a potential advantage of TCD as it provides the possibility to monitor changes of ICP in time. Overall accuracy for TCD-based methods ranges around ±12 mmHg, with a great potential of tracing dynamical changes of ICP in time, particularly those of vasogenic nature.

Malaria Parasites Distribute Subversive Messages across Enemy Lines

During its life cycle, the malaria parasite must cope with a set of diverse environments and institute strategies to alter its host's responses. A recent study remarkably demonstrates how these parasites exploit red blood cell products, loading them into 'armed' secreted vesicles sent to manipulate their host's 'endothelium battlefront', thereby promoting malaria infection.

Differences in the modulation of reactive species, lipid bodies, cyclooxygenase-2, 5-lipoxygenase and PPAR-γ in cerebral malaria-susceptible and resistant mice

Proinflammatory responses are associated with the severity of cerebral malaria. NO, H₂O₂, eicosanoid and PPAR-γ are involved in proinflammatory responses, but regulation of these factors is unclear in malaria. This work aimed to compare the expression of eicosanoid-forming-enzymes in cerebral malaria-susceptible CBA and C57BL/6 and -resistant BALB/c mice. Mice were infected with Plasmodium berghei ANKA, and the survival rates and parasitemia curves were assessed. On the sixth day post-infection, cyclooxygenase-2 and 5-lipoxygenase in brain sections were assessed by immunohistochemistry, and, NO, H₂O₂, lipid bodies, and PPAR-γ expression were assessed in peritoneal macrophages. The C57BL/6 had more severe disease with a lower survival time, higher parasitemia and lower production of plasmodicidal NO and H₂O₂ molecules than BALB/c. Enhanced COX-2 and 5-LOX expression were observed in brain tissue cells and vessels from C57BL/6 mice, and these mice expressed higher constitutive PPAR-γ levels. There was no translocation of PPAR-γ from cytoplasm to nucleus in macrophages from these mice. CBA mice had enhanced COX-2 expression in brain tissue cells and vessels and also lacked PPAR-γ cytoplasm-to-nucleus translocation. The resistant BALB/c mice presented higher survival time, lower parasitemia and higher NO and H₂O₂ production on the sixth day post-infection. These mice did not express either COX-2 or 5-LOX in brain tissue cells and vessels. Our data showed that besides the high parasite burden and lack of microbicidal molecules, an imbalance with high COX-2 and 5-LOX eicosanoid expression and a lack of regulatory PPAR-γ cytoplasm-to-nucleus translocation in macrophages were observed in mice that develop cerebral malaria.

Longitudinal Visuomotor Development in a Malaria Endemic Area: Cerebral Malaria and Beyond

Paediatric cerebral malaria is the most serious complication of Plasmodium falciparum infection. While the majority recover, long-term cognitive impairment has been highlighted as a significant and neglected problem. Persistent or serious deficits in processes such as attention or behavioural inhibition should be manifest in changes to performance on oculomotor tasks. Therefore we investigated the impact of cerebral malaria on the development of reflexive pro-saccades and antisaccades. In a longitudinal study, 47 children previously admitted with retinopathy-confirmed cerebral malaria (mean age at admission 54 months), were compared with 37 local healthy controls (mean ages at first study visit 117 and 110 months respectively). In each of three or four test sessions, over a period of up to 32 months, participants completed 100 prosaccade tasks and 100 antisaccade tasks. Eye movements were recorded using infrared reflectance oculography; prosaccade, correct antisaccade and error prosaccade latency, and antisaccade directional error rate were calculated. Hierarchical linear modelling was used to investigate the effect of age and the influence of cerebral malaria on these parameters. Data were also collected from an independent, older group (mean age 183 months) of 37 local healthy participants in a separate cross-sectional study. Longitudinal data exhibited the expected decrease in latency with age for all saccade types, and a decrease in the antisaccade directional error rate. Hierarchical linear modelling confirmed that age had a statistically significant effect on all parameters (p< = 0.001). However, there were no statistically significant differences between the cerebral malaria and control groups. Combining groups, comparison with the literature demonstrated that antisaccade directional error rate for the Malawi sample was significantly higher than expected, while latencies for all saccade types were indistinguishable from published. The high directional error rate was also confirmed in the older, healthy Malawian participants from the cross sectional study. Our observation of similar oculomotor performance in cerebral malaria and control groups at long follow-up periods suggests that cerebral malaria survivors are not at a generally increased risk of persistent cognitive deficits. Our data raise questions about the prevailing hypothesis that cerebral malaria has gross impacts on the development of processes such as attention and behavioural inhibition. More importantly, our novel finding of a clear difference in antisaccade performance between all of the Malawi participants and published data suggests that the Malawian paediatric population as a whole faces serious challenges to cognitive development beyond cerebral malaria.

Uptake of parasite-derived vesicles by astrocytes and microglial phagocytosis of infected erythrocytes may drive neuroinflammation in cerebral malaria

Astrocytes and microglia are activated during cerebral malaria (CM) and contribute to the production and release of several mediators during neuroinflammatory processes. Whether these changes are the consequence of a direct crosstalk between glial cells and the malarial parasite and how these cells participate in the pathogenesis of CM is not yet clear. We therefore examined the interaction of astrocytes and microglia with Plasmodium berghei ANKA-infected red blood cells using primary cell cultures derived from newborn C57BL/6 mice. We observed a dynamic transfer of vesicles from the parasite to astrocytes within minutes of contact, and the phagocytosis of infected red blood cells by microglia. Differential gene expression studies using the Affymetrix GeneChip^® microarray, and quantitative PCR analyses showed the increase in expression of the set of genes belonging to the immune response network in parasite activated astrocytes and microglia. Interestingly, expression of these genes was also significantly upregulated in brains of mice dying from CM compared with uninfected mice or infected mice that did not develop the neuropathology. Accumulation of parasite-derived vesicles within astrocytes, and the phagocytosis of infected red blood cells by microglia induced a subsequent increase in interferon gamma inducible protein 10 (IP10) in both the brain and plasma of infected mice at the onset of CM, confirming a role for this molecule in CM pathogenesis. Altogether, these observations point to a possible role for glial cells in the neuropathological processes leading to CM. GLIA 2016 GLIA 2017;65:75-92.

Absence of apolipoprotein E protects mice from cerebral malaria

Cerebral malaria claims the life of millions of people each year, particularly those of children, and is a major global public health problem. Thus, the identification of novel malaria biomarkers that could be utilized as diagnostic or therapeutic targets is becoming increasingly important. Using a proteomic approach, we previously identified unique biomarkers in the sera of malaria-infected individuals, including apolipoprotein E (ApoE). ApoE is the dominant apolipoprotein in the brain and has been implicated in several neurological disorders; therefore, we were interested in the potential role of ApoE in cerebral malaria. Here we report the first demonstration that cerebral malaria is markedly attenuated in ApoE^−/− mice. The protection provided by the absence of ApoE was associated with decreased sequestration of parasites and T cells within the brain, and was determined to be independent from the involvement of ApoE receptors and from the altered lipid metabolism associated with the knock-out mice. Importantly, we demonstrated that treatment of mice with the ApoE antagonist heparin octasaccharide significantly decreased the incidence of cerebral malaria. Overall, our study indicates that the reduction of ApoE could be utilized in the development of therapeutic treatments aimed at mitigating the neuropathology of cerebral malaria.

Establishment of a murine model of cerebral malaria in KunMing mice infected with Plasmodium berghei ANKA

Malaria remains one of the most devastating diseases. Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection resulting in high mortality and morbidity worldwide. Analysis of precise mechanisms of CM in humans is difficult for ethical reasons and animal models of CM have been employed to study malaria pathogenesis. Here, we describe a new experimental cerebral malaria (ECM) model with Plasmodium berghei ANKA infection in KunMing (KM) mice. KM mice developed ECM after blood-stage or sporozoites infection, and the development of ECM in KM mice has a dose-dependent relationship with sporozoites inoculums. Histopathological findings revealed important features associated with ECM, including accumulation of mononuclear cells and red blood cells in brain microvascular, and brain parenchymal haemorrhages. Blood-brain barrier (BBB) examination showed that BBB disruption was present in infected KM mice when displaying clinical signs of CM. In vivo bioluminescent imaging experiment indicated that parasitized red blood cells accumulated in most vital organs including heart, lung, spleen, kidney, liver and brain. The levels of inflammatory cytokines interferon-gamma, tumour necrosis factor-alpha, interleukin (IL)-17, IL-12, IL-6 and IL-10 were all remarkably increased in KM mice infected with P. berghei ANKA. This study indicates that P. berghei ANKA infection in KM mice can be used as ECM model to extend further research on genetic, pharmacological and vaccine studies of CM.

Antiplasmodial, anti-complement and anti-inflammatory in vitro effects of Biophytum umbraculum Welw. traditionally used against cerebral malaria in Mali

ETHNOPHARMACOLOGICAL RELEVANCE

Biophytum umbraculum Welw. (Oxalidaceae) is a highly valued African medicinal plant used for treatment of cerebral malaria, a critical complication of falciparum malaria.

AIM OF THE STUDY

To provide additional information about traditional use of B. umbraculum and to test plant extracts and isolated compounds for in vitro activities related to cerebral malaria.

MATERIALS AND METHODS

The traditional practitioners were questioned about indication, mode of processing/application, dosage and local name of B. umbraculum. Organic extracts and some main constituents of the plant were investigated for anti-malaria, anti-complement activity and inhibition of NO secretion in a RAW 264.7 cell line.

RESULTS

Treatment of cerebral malaria was the main use of B. umbraculum (fidelity level 56%). The ethyl acetate extract showed anti-complement activity (ICH50 5.7±1.6μg/ml), inhibition of macrophage activation (IC50 16.4±1.3μg/ml) and in vitro antiplasmodial activity (IC50 K1 5.6±0.13μg/ml, IC50 NF54 6.7±0.03μg/ml). The main constituents (flavone C-glycosides) did not contribute to the activity of the extract.

CONCLUSION

Inhibition of complement activation and anti-inflammatory activity of B. umbraculum observed in this study might be possible targets for adjunctive therapy in cerebral malaria together with its antiplasmodial activity. However, clinical trials are necessary to evaluate the activity due to the complex pathogenesis of cerebral malaria.

Misdiagnosis of cerebral malaria initially as acute psychotic disorder and later as human rabies: a case report

BACKGROUND

Cerebral malaria is arguably one of the most common non-traumatic encephalopathies in the developing world. Unless the diagnosis of cerebral malaria is made promptly, the consequence could be disastrous. Even though the diagnosis of cerebral malaria can be made relatively easily in majority of cases atypical presentation can often lead to misdiagnosis or delayed diagnosis. We report a case of an uncommon presentation of Plasmodium falciparum infection in a 17-year-old school girl with altered sensorium, seizures and phobic spasms.

CASE PRESENTATION

A previously healthy 17-year-old school girl was admitted to our hospital with acute condition characterised by comatose state, recurrent seizures and phobic spasms. She initially presented to a local hospital with agitation and over talkativeness and was diagnosed as having an acute psychotic state. Few days later she became drowsy and developed recurrent seizures and marked phobic spasms which prompted the treating physician to diagnose human rabies. However, further investigations carried out in our unit (including rapid antigenic test for P. falciparum and peripheral blood smear) were positive for P. falciparum. She was treated as for cerebral malaria with intravenous quinine and discharge from hospital with no residual neurological deficit.

CONCLUSION

Atypical presentation of cerebral malaria can often lead to misdiagnosis. This patient presented with encephalopathic illness with phobic spasms was initially misdiagnosed as human rabies. Therefore, the physicians in malarial endemic areas should be vigilant of similar presentations and should consider cerebral malaria as a possibility.

Potential cerebral malaria therapy: intramuscular arteether and vitamin D co-administration

Cerebral malaria (CM) shows lethality rate of 15–25% despite effective antimalarial chemotherapy. The effective adjunct treatment to counteract the CM pathogenesis is urgently required. In murine CM model, most interventions studied till date are administered before the onset of CM symptoms, which belittle its translational value to human. We studied intramuscular arteether–vitamin D (ART–VD) combination treatment for CM outcome improvement after the onset of neurological symptoms. The intramuscular dose of 50 µg kg−1 VD for 3 days combined with a loading dose of 25 mg kg−1α/β arteether followed by 12·5 mg kg−1 dose for two consecutive days led to significant improvement in survival (73% in combination group vs 29 and 0% in arteether and VD monotherapy, respectively) and clinical recovery. The treatment in all the groups partially restored the blood–brain barrier integrity and reduced the level of serum proinflammatory cytokines tumour necrosis factor-α and interferon-γ. The brain transcripts of inflammatory chemokines viz. CXCL10, CXCL9, CCL4 and CCL5 and T cell migration in the brain microvasculature were significantly diminished in all the treatment groups. ART–VD treatment significantly reduced intercellular cell adhesion molecule-1 expression. Taken together, our findings show that coordinated actions of ART–VD improve the outcome of experimental CM.

Rosette-Disrupting Effect of an Anti-Plasmodial Compound for the Potential Treatment of Plasmodium falciparum Malaria Complications

The spread of artemisinin-resistant parasites could lead to higher incidence of patients with malaria complications. However, there are no current treatments that directly dislodge sequestered parasites from the microvasculature. We show that four common antiplasmodial drugs do not disperse rosettes (erythrocyte clusters formed by malaria parasites) and therefore develop a cell-based high-throughput assay to identify potential rosette-disrupting compounds. A pilot screen of 2693 compounds identified Malaria Box compound MMV006764 as a potential candidate. Although it reduced rosetting by a modest 20%, MMV006764 was validated to be similarly effective against both blood group O and A rosettes of three laboratory parasite lines. Coupled with its antiplasmodial activity and drug-likeness, MMV006764 represents the first small-molecule compound that disrupts rosetting and could potentially be used in a resource-limited setting to treat patients deteriorating rapidly from malaria complications. Such dual-action drugs that simultaneously restore microcirculation and reduce parasite load could significantly reduce malaria morbidity and mortality.

Fighting the Monster: Applying the Host Damage Framework to Human Central Nervous System Infections

The host damage-response framework states that microbial pathogenesis is a product of microbial virulence factors and collateral damage from host immune responses. Immune-mediated host damage is particularly important within the size-restricted central nervous system (CNS), where immune responses may exacerbate cerebral edema and neurological damage, leading to coma and death. In this review, we compare human host and therapeutic responses in representative nonviral generalized CNS infections that induce archetypal host damage responses: cryptococcal menigoencephalitis and tuberculous meningitis in HIV-infected and non-HIV-infected patients, pneumococcal meningitis, and cerebral malaria. Consideration of the underlying patterns of host responses provides critical insights into host damage and may suggest tailored adjunctive therapeutics to improve disease outcome.

The blood-brain barrier

In autoimmune neurologic disorders, the blood-brain barrier (BBB) plays a central role in immunopathogenesis, since this vascular interface is an entry path for cells and effector molecules of the peripheral immune system to reach the target organ, the central nervous system (CNS). The BBB's unique anatomic structure and the tightly regulated interplay of its cellular and acellular components allow for maintenance of brain homeostasis, regulation of influx and efflux, and protection from harm; these ensure an optimal environment for the neuronal network to function properly. In both health and disease, the BBB acts as mediator between the periphery and the CNS. For example, immune cell trafficking through the cerebral vasculature is essential to clear microbes or cell debris from neural tissues, while poorly regulated cellular transmigration can underlie or worsen CNS pathology. In this chapter, we focus on the specialized multicellular structure and function of the BBB/neurovascular unit and discuss how BBB breakdown can precede or be a consequence of neuroinflammation. We introduce the blood-cerebrospinal fluid barrier and include a brief aside about evolutionary aspects of barrier formation and refinements. Lastly, since restoration of barrier function is considered key to ameliorate neurologic disease, we speculate about new therapeutic avenues to repair a damaged BBB.

Validation of a New Minimally Invasive Intracranial Pressure Monitoring Method by Direct Comparison with an Invasive Technique

In this chapter we present in vivo experiments with a new minimally invasive method of monitoring intracranial pressure (ICP). Strain gauge deformation sensors are externally glued onto the exposed skull. The signal from these sensors is amplified, filtered, and sent to a computer with appropriate software for analysis and data storage. Saline infusions into the spinal channel of rats were performed to produce ICP changes, and minimally invasive ICP and direct Codman intraparenchymal ICP were simultaneously acquired in six animals. The similarity between the invasive and minimally invasive methods in response to ICP increase was assessed using Pearson's correlation coefficient. It demonstrated good agreement between the two measures < r > = 0.8 ± 0.2, with a range of 0.31-0.99.

Indocyanine Green Liposomes for Diagnosis and Therapeutic Monitoring of Cerebral Malaria

Cerebral malaria (CM) is a major cause of death of Plasmodium falciparum infection. Misdiagnosis of CM often leads to treatment delay and mortality. Conventional brain imaging technologies are rarely applicable in endemic areas. Here we address the unmet need for a simple, non-invasive imaging methodology for early diagnosis of CM. This study presents the diagnostic and therapeutic monitoring using liposomes containing the FDA-approved fluorescent dye indocyanine green (ICG) in a CM murine model. Increased emission intensity of liposomal ICG was demonstrated in comparison with free ICG. The Liposomal ICG's emission was greater in the brains of the infected mice compared to naïve mice and drug treated mice (where CM was prevented). Histological analyses suggest that the accumulation of liposomal ICG in the cerebral vasculature is due to extensive uptake mediated by activated phagocytes. Overall, liposomal ICG offers a valuable diagnostic tool and a biomarker for effectiveness of CM treatment, as well as other diseases that involve inflammation and blood vessel occlusion.

Distribution and Potential Indicators of Hospitalized Cases of Neurocysticercosis and Epilepsy in Ecuador from 1996 to 2008

Background

Epilepsy is one of the most common signs of Neurocysticercosis (NCC). In this study, spatial and temporal variations in the incidence of hospitalized cases (IHC) of epilepsy and NCC in Ecuadorian municipalities were analyzed. Additionally, potential socio-economic and landscape indicators were evaluated in order to understand in part the macro-epidemiology of the Taenia solium taeniasis/cysticercosis complex.

Methodology

Data on the number of hospitalized epilepsy and NCC cases by municipality of residence were obtained from morbidity-hospital systems in Ecuador. SatScan software was used to determine whether variations in the IHC of epilepsy and NCC in space and time. In addition, several socio-economic and landscape variables at municipality level were used to study factors intervening in the macro-epidemiology of these diseases. Negative Binomial regression models through stepwise selection and Bayesian Model Averaging (BMA) were used to explain the variations in the IHC of epilepsy and NCC.

Principal findings

Different clusters were identified through space and time. Traditional endemic zones for NCC and epilepsy, recognized in other studies were confirmed in our study. However, for both disorders more recent clusters were identified. Among municipalities, an increasing tendency for IHC of epilepsy, and a decreasing tendency for the IHC of NCC were observed over time. In contrast, within municipalities a positive linear relationship between both disorders was found. An increase in the implementation of systems for eliminating excrements would help to reduce the IHC of epilepsy by 1.00% (IC_95%; 0.2%–1.8%) and by 5.12% (IC_95%; 3.63%-6.59%) for the IHC of NCC. The presence of pig production was related to IHC of NCC.

Conclusion/Significance

Both disorders were related to the lack of an efficient system for eliminating excrements. Given the appearance of recent epilepsy clusters, these locations should be studied in depth to discriminate epilepsies due to NCC from epilepsies due to other causes. Field studies are needed to evaluate the true prevalence of cysticercosis in humans and pigs in different zones of the country in order to better implement and manage prevention and/or control campaigns.

T. solium neurocysticercosis is considered the most important parasitic disease of the central nervous system in humans; it is estimated to be responsible for at least one third of acquired epilepsies in developing countries. In Ecuador, the relationship between acquired epilepsy and neurocysticercosis remains unclear due to different factors such as, the lack of specialized health care personnel, appropriate diagnostic techniques and the fact that acquired epilepsy is characteristic of many other infectious and non-infectious diseases in the endemic zones of the country. In this study, spatio-temporal information and potential socio-economic indicators were studied for the number of hospitalized neurocysticercosis and epileptic cases in the country in order to locate and characterize important clusters in space and time. This study identified traditional endemic clusters in the highlands for both conditions as well as new clusters appearing in recent years in other zones not considered endemic. Also the incidence of hospitalized cases of epilepsy and neurocysticercosis were significantly higher in urban zones, probably due to a better access to health facilities. The presence of systems for excrement disposal was significantly associated with a reduction in the incident cases for both epilepsy and neurocysticercosis. More studies are needed to evaluate the true prevalence of neurocysticercosis associated epilepsy in humans and cysticercosis in pigs around the country in order to better implement and manage control campaigns.

Increased synapsin I expression in cerebral malaria

Synapsin I is a neuronal phosphoprotein contained in the synaptic vesicles of mammalian central and peripheral nervous systems. It regulates both neurotransmitter release and synaptic formation. Variations in synapsin I expression in the brain have been reported to cause brain malfunction. In severe malaria, neurological complications, such as convulsion, delirium and coma, suggest abnormalities in the release of neurotransmitters. This study evaluated synapsin I expression in cerebral malaria (CM). An immunohistochemical method was used to study the semi-quantitative and qualitative expression of synapsin I in the brain of CM patients (10 cases) who died with Plasmodium falciparum, compared with non-cerebral malaria (NCM) (4 cases), and control brain tissues (5). Synapsin I was expressed in the gray matter of the cerebral cortex and the molecular layer of the cerebellum, as a diffusely dense precipitate pattern in the neuropil, with no immunoreactivity in the neurons, neuronal dendrites, glial cells, endothelial cells, and Purkinje cells. The findings were similarly demonstrated in CM, NCM, and control brain tissues. However, in the granular layer of the cerebellum, a significant increase in synapsin I expression was observed in the granule cells, and the glomerular synaptic complex, from the CM group, compared with the NCM, and control brain tissues (all P < 0.05). Parasitemia showed a positive correlation with synapsin I expression in the granule cells (on admission: Spearman's ρ = 0.600, P = 0.023) (before death: Spearman's ρ = 0.678, P = 0.008), and glomerular synaptic complex (before death: Spearman's ρ = 0.571, P = 0.033). It was hypothesized that CM causes pre-synaptic excitation and eventually activation of synapsin I, leading to increased neurotransmitter release. Synapsin I inhibitor should be investigated further as a target for a therapeutic intervention to alleviate neurological symptoms in severe malaria.

Recruited monocytes modulate malaria-induced lung injury through CD36-mediated clearance of sequestered infected erythrocytes

Pulmonary complications occur in a significant percentage of adults and children during the course of severe malaria. The cellular and molecular innate immune mechanisms that limit the extent of pulmonary inflammation and preserve lung function during severe Plasmodium infections remain unclear. In particular, the contributions to pulmonary complications by parasitized erythrocyte sequestration and subsequent clearance from the lung microvasculature by immune cells have not been clearly defined. We used the Plasmodium berghei ANKA-C57BL/6 mouse model of severe malaria to investigate the mechanisms governing the nature and extent of malaria-associated lung injury. We have demonstrated that sequestration of infected erythrocytes on postcapillary endothelial surfaces results in acute lung injury and the rapid recruitment of CCR2(+)CD11b(+)Ly6C(hi) monocytes from the circulation. These recruited cells remain in the lungs as monocyte-derived macrophages and are instrumental in the phagocytic clearance of adherent Plasmodium berghei-infected erythrocytes. In contrast, alveolar macrophages do not play a significant role in the clearance of malaria-infected cells. Furthermore, the results obtained from Ccr2(-/-), Cd36(-/-), and CD36 bone marrow chimeric mice showed that sequestration in the absence of CD36-mediated phagocytic clearance by monocytes leads to exaggerated lung pathologic features. In summary, our data indicate that the intensity of malaria-induced lung pathologic features is proportional to the steady-state levels of Plasmodium-infected erythrocytes adhering to the pulmonary vasculature. Moreover, the present work has defined a major role of recruited monocytes in clearing infected erythrocytes from the pulmonary interstitium, thus minimizing lung damage.

Plant Hormone Salicylic Acid Produced by a Malaria Parasite Controls Host Immunity and Cerebral Malaria Outcome

The apicomplexan parasite Toxoplasma gondii produces the plant hormone abscisic acid, but it is unclear if phytohormones are produced by the malaria parasite Plasmodium spp., the most important parasite of this phylum. Here, we report detection of salicylic acid, an immune-related phytohormone of land plants, in P. berghei ANKA and T. gondii cell lysates. However, addition of salicylic acid to P. falciparum and T. gondii culture had no effect. We transfected P. falciparum 3D7 with the nahG gene, which encodes a salicylic acid-degrading enzyme isolated from plant-infecting Pseudomonas sp., and established a salicylic acid-deficient mutant. The mutant had a significantly decreased concentration of parasite-synthesized prostaglandin E₂, which potentially modulates host immunity as an adaptive evolution of Plasmodium spp. To investigate the function of salicylic acid and prostaglandin E₂ on host immunity, we established P. berghei ANKA mutants expressing nahG. C57BL/6 mice infected with nahG transfectants developed enhanced cerebral malaria, as assessed by Evans blue leakage and brain histological observation. The nahG-transfectant also significantly increased the mortality rate of mice. Prostaglandin E₂ reduced the brain symptoms by induction of T helper-2 cytokines. As expected, T helper-1 cytokines including interferon-γ and interleukin-2 were significantly elevated by infection with the nahG transfectant. Thus, salicylic acid of Plasmodium spp. may be a new pathogenic factor of this threatening parasite and may modulate immune function via parasite-produced prostaglandin E₂.

Vascular endothelial growth factor (VEGF) and lovastatin suppress the inflammatory response to Plasmodium berghei infection and protect against experimental cerebral malaria

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection, which is associated with high mortality and long-term cognitive impairment even when effective anti-parasitic treatment is administered. (1 , 2) Supportive therapy is needed to improve both morbidity and mortality associated with this condition. In an accompanying paper, we have demonstrated that in the Plasmodium berghei ANKA (PbA) rodent model, CM can be effectively prevented by a treatment combining sub-lethal doses of lipopolysaccharide S (LPS) and vascular endothelial growth factor (VEGF). Since LPS is not suitable for human therapy, we investigated whether lovastatin would represent a suitable substitute. This compound, widely used to lower cholesterol levels in plasma, shares with LPS the ability to elicit an anti-inflammatory response by activating the Nrf-2 gene, and when given to P. berghei-infected mice prevents to some extent the onset of CM. We show here that lovastatin- and VEGF-treated mice did not develop CM and showed few signs, if any, of endothelial damage and systemic inflammation. The combination treatment was much more effective than lovastatin and VEGF alone. Immunohistochemistry and gene expression analysis indicated that VEGF and LPS together overturned the two pathogenic mechanisms responsible for the development of CM: endothelial damage and disregulated activation of the inflammatory response. These findings provide the rationale for investigating the therapeutic potential of these compounds in human CM as well as in other inflammatory pathologies that respond poorly to steroid and non-steroid anti-inflammatory therapy.

The HFE genotype and a formulated diet controlling for iron status attenuate experimental cerebral malaria in mice

Plasmodium falciparum infects approximately 500million individuals each year. A small but significant number of infections lead to complications such as cerebral malaria. Cerebral malaria is associated with myelin damage and neurological deficits in survivors, and iron status is thought to impact the outcome of infection. We evaluated whether a mouse model of experimental cerebral malaria with Plasmodium berghei ANKA strain was altered by dietary iron deficiency or genetic iron overload (H67D HFE). We found that H67D mice had increased survival over H67H (wild type) mice. Moreover, a specifically designed formulation diet increased survival regardless of whether the diet was iron deficient or iron adequate. To determine potential mechanisms underlying demyelination in experimental cerebral malaria, we measured Semaphorin4A (Sema4A) protein levels in the brain because we found it is cytotoxic to oligodendrocytes. Sema4A was increased in wild type mice that developed experimental cerebral malaria while consuming standard rodent chow, consistent with a decrease in myelin basic protein, an indicator of myelin integrity. The brains of iron deficient and H67D mice had lower levels of Sema4A. Myelin basic protein was decreased in brains of mice fed the iron deficient diet as has been previously reported. We also examined erythropoietin, which is under consideration for treatment of cerebral malaria, and IL-6, which is known to increase during infection. We found that plasma erythropoietin was elevated and IL-6 was low in H67D mice and in the mice fed the formulation diets. These data reveal a paradigm-shifting concept that maintaining iron status may not increase the mortality associated with malaria and provide a dietary strategy for further examination. Moreover, the data provide clues for exploring the mechanism to limit the co-morbidity associated with experimental cerebral malaria that appears to include decreased Sema4A in brain as well as elevated erythropoietin and lower IL-6 in plasma.

Simultaneously targeting inflammatory response and parasite sequestration in brain to treat Experimental Cerebral Malaria

Malaria afflicts around 200 million people annually, with a mortality number close to 600,000. The mortality rate in Human Cerebral Malaria (HCM) is unacceptably high (15–20%), despite the availability of artemisinin-based therapy. An effective adjunct therapy is urgently needed. Experimental Cerebral Malaria (ECM) in mice manifests many of the neurological features of HCM. Migration of T cells and parasite-infected RBCs (pRBCs) into the brain are both necessary to precipitate the disease. We have been able to simultaneously target both these parameters of ECM. Curcumin alone was able to reverse all the parameters investigated in this study that govern inflammatory responses, CD8⁺ T cell and pRBC sequestration into the brain and blood brain barrier (BBB) breakdown. But the animals eventually died of anemia due to parasite build-up in blood. However, arteether-curcumin (AC) combination therapy even after the onset of symptoms provided complete cure. AC treatment is a promising therapeutic option for HCM.

Potential role of Plasmodium falciparum-derived ammonia in the pathogenesis of cerebral malaria

Cerebral malaria (CM) is the most severe complication associated with Plasmodium falciparum infection. The exact pathogenic mechanisms leading to the development of CM remains poorly understood while the mortality rates remain high. Several potential mechanisms including mechanical obstruction of brain microvasculature, inflammation, oxidative stress, cerebral energy defects, and hemostatic dysfunction have been suggested to play a role in CM pathogenesis. However, these proposed mechanisms, even when considered together, do not fully explain the pathogenesis and clinicopathological features of human CM. This necessitates consideration of alternative pathogenic mechanisms. P. falciparum generates substantial amounts of ammonia as a catabolic by-product, but lacks detoxification mechanisms. Whether this parasite-derived ammonia plays a pathogenic role in CM is presently unknown, despite its potential to cause localized brain ammonia elevation and subsequent neurotoxic effects. This article therefore, explores and proposes a potential role of parasite-derived ammonia in the pathogenesis and neuropathology of CM. A consideration of parasite-derived ammonia as a factor in CM pathogenesis provides plausible explanations of the various features observed in CM patients including how a largely intravascular parasite can cause neuronal dysfunction. It also provides a framework for rational development and testing of novel drugs targeting the parasite's ammonia handling.

Extracellular hemoglobin: the case of a friend turned foe

Hemoglobin (Hb) is a highly conserved molecule present in all life forms and functionally tied to the complexity of aerobic organisms on earth in utilizing oxygen from the atmosphere and delivering to cells and tissues. This primary function sustains the energy requirements of cells and maintains cellular homeostasis. Decades of intensive research has presented a paradigm shift that shows how the molecule also functions to facilitate smooth oxygen delivery through the cardiovascular system for cellular bioenergetic homeostasis and signaling for cell function and defense. These roles are particularly highlighted in the binding of Hb to gaseous molecules carbon dioxide (CO₂), nitric oxide (NO) and carbon monoxide (CO), while also serving indirectly or directly as sources of these signaling molecules. The functional activities impacted by Hb outside of bioenergetics homeostasis, include fertilization, signaling functions, modulation of inflammatory responses for defense and cell viability. These activities are efficiently executed while Hb is sequestered safely within the confines of the red blood cell (rbc). Outside of rbc confines, Hb disaggregates and becomes a danger molecule to cell survival. In these perpectives, Hb function is broadly dichotomous, either a friend in its natural environment providing and facilitating the means for cell function or foe when dislocated from its habitat under stress or pathological condition disrupting cell function. The review presents insights into how this dichotomy in function manifests.

Impaired systemic tetrahydrobiopterin bioavailability and increased oxidized biopterins in pediatric falciparum malaria: association with disease severity

Decreased bioavailability of nitric oxide (NO) is a major contributor to the pathophysiology of severe falciparum malaria. Tetrahydrobiopterin (BH4) is an enzyme cofactor required for NO synthesis from L-arginine. We hypothesized that systemic levels of BH₄ would be decreased in children with cerebral malaria, contributing to low NO bioavailability. In an observational study in Tanzania, we measured urine levels of biopterin in its various redox states (fully reduced [BH₄] and the oxidized metabolites, dihydrobiopterin [BH₂] and biopterin [B₀]) in children with uncomplicated malaria (UM, n = 55), cerebral malaria (CM, n = 45), non-malaria central nervous system conditions (NMC, n = 48), and in 111 healthy controls (HC). Median urine BH4 concentration in CM (1.10 [IQR:0.55-2.18] μmol/mmol creatinine) was significantly lower compared to each of the other three groups - UM (2.10 [IQR:1.32-3.14];p<0.001), NMC (1.52 [IQR:1.01-2.71];p = 0.002), and HC (1.60 [IQR:1.15-2.23];p = 0.005). Oxidized biopterins were increased, and the BH4:BH2 ratio markedly decreased in CM. In a multivariate logistic regression model, each Log10-unit decrease in urine BH4 was independently associated with a 3.85-fold (95% CI:1.89-7.61) increase in odds of CM (p<0.001). Low systemic BH4 levels and increased oxidized biopterins contribute to the low NO bioavailability observed in CM. Adjunctive therapy to regenerate BH4 may have a role in improving NO bioavailability and microvascular perfusion in severe falciparum malaria.

Oral lipid-based nanoformulation of tafenoquine enhanced bioavailability and blood stage antimalarial efficacy and led to a reduction in human red blood cell loss in mice

Tafenoquine (TQ), a new synthetic analog of primaquine, has relatively poor bioavailability and associated toxicity in glucose-6-phosphate dehydrogenase (G6PD)-deficient individuals. A microemulsion formulation of TQ (MTQ) with sizes <20 nm improved the solubility of TQ and enhanced the oral bioavailability from 55% to 99% in healthy mice (area under the curve 0 to infinity: 11,368±1,232 and 23,842±872 min·μmol/L) for reference TQ and MTQ, respectively. Average parasitemia in Plasmodium berghei-infected mice was four- to tenfold lower in the MTQ-treated group. In vitro antiplasmodial activities against chloroquine-sensitive and chloroquine-resistant strains of Plasmodium falciparum indicated no change in half maximal inhibitory concentration, suggesting that the microemulsion did not affect the inherent activity of TQ. In a humanized mouse model of G6PD deficiency, we observed reduction in toxicity of TQ as delivered by MTQ at low but efficacious concentrations of TQ. We hereby report an enhancement in the solubility, bioavailibility, and efficacy of TQ against blood stages of Plasmodium parasites without a corresponding increase in toxicity.

IRGM3 contributes to immunopathology and is required for differentiation of antigen-specific effector CD8+ T cells in experimental cerebral malaria

Gamma interferon (IFN-γ) drives antiparasite responses and immunopathology during infection with Plasmodium species. Immunity-related GTPases (IRGs) are a class of IFN-γ-dependent proteins that are essential for cell autonomous immunity to numerous intracellular pathogens. However, it is currently unknown whether IRGs modulate responses during malaria. We have used the Plasmodium berghei ANKA (PbA) model in which mice develop experimental cerebral malaria (ECM) to study the roles of IRGM1 and IRGM3 in immunopathology. Induction of mRNA for Irgm1 and Irgm3 was found in the brains and spleens of infected mice at times of peak IFN-γ production. Irgm3-/- but not Irgm1-/- mice were completely protected from the development of ECM, and this protection was associated with the decreased induction of inflammatory cytokines, as well as decreased recruitment and activation of CD8+ T cells within the brain. Although antigen-specific proliferation of transferred CD8+ T cells was not diminished compared to that of wild-type recipients following PbA infection, T cells transferred into Irgm3-/- recipients showed a striking impairment of effector differentiation. Decreased induction of several inflammatory cytokines and chemokines (interleukin-6, CCL2, CCL3, and CCL4), as well as enhanced mRNA expression of type-I IFNs, was found in the spleens of Irgm3-/- mice at day 4 postinfection. Together, these data suggest that protection from ECM pathology in Irgm3-/- mice occurs due to impaired generation of CD8+ effector function. This defect is nonintrinsic to CD8+ T cells. Instead, diminished T cell responses most likely result from defective initiation of inflammatory responses in myeloid cells.

Cerebral malaria as a risk factor for the development of epilepsy and other long-term neurological conditions: a meta-analysis

Cerebral malaria (CM) is the most common and severe acute neurological manifestation of Plasmodium falciparum malaria. Children living in malaria-endemic areas of sub-Saharan Africa are at the highest risk of developing CM, and the long-term effect of CM on neurological function is uncertain. We conducted a meta-analysis to quantitatively assess the association between CM and development of long-term neurological impairment. We performed a systematic search through PubMed (including MEDLINE; 1946 to December 2014) and EMBASE (1974 to January 2015) to identify relevant articles. Eligible studies assessed the association between CM and neurological sequelae and were included if they met the criteria allowing a complete extraction of data. Eight studies were included in the final analysis, and in total, 2005 individuals were analysed (cases: n=842, controls: n=1163), most of whom were children. CM was associated with an increased risk of epilepsy (OR 4.68, 95% CI: 2.52-8.70), an increased risk of intelligence quotient (IQ) impairment (OR 4.72, 95% CI: 0.78-28.49), an increased risk of neurodisabilities (OR 16.16, 95% CI: 1.34-195.45), and an increased risk of behavioural disorder (OR 8.47, 95% CI: 2.75-26.04). Our findings suggest that children who survive CM are at increased risk of long-term neurological adverse outcome, including epilepsy. This may present a major public health problem in terms of education and development in malaria-endemic areas. Measures to avoid neurological morbidity are warranted.

Neurocognitive domains affected by cerebral malaria and severe malarial anemia in children

This study assessed the effects of cerebral malaria (CM) and severe malarial anemia (SMA) on individual neurocognitive domains. Eighty children with CM, 86 with SMA, and 61 community children (CC) were assessed for gross motor skills, fine motor skills, visual reception, receptive language, and expressive language a week after discharge (CM or SMA) or at enrolment (CC), and 6 and 12 months later. At 12-months follow-up, children with CM had significantly lower scores than CC for all outcomes. Children with SMA had significantly lower scores than CC for visual reception, receptive language, and expressive language, and scores that were lower but did not reach significance for gross and fine motor skills. Children with CM had significantly lower scores than children with SMA for fine motor skills. Children with SMA and CM have long-term impairment in multiple neurocognitive domains. Fine motor skills may be affected more profoundly in CM than SMA.

Olfactory plays a key role in spatiotemporal pathogenesis of cerebral malaria

Cerebral malaria is a complication of Plasmodium falciparum infection characterized by sudden coma, death, or neurodisability. Studies using a mouse model of experimental cerebral malaria (ECM) have indicated that blood-brain barrier disruption and CD8 T cell recruitment contribute to disease, but the spatiotemporal mechanisms are poorly understood. We show by ultra-high-field MRI and multiphoton microscopy that the olfactory bulb is physically and functionally damaged (loss of smell) by Plasmodium parasites during ECM. The trabecular small capillaries comprising the olfactory bulb show parasite accumulation and cell occlusion followed by microbleeding, events associated with high fever and cytokine storm. Specifically, the olfactory upregulates chemokine CCL21, and loss or functional blockade of its receptors CCR7 and CXCR3 results in decreased CD8 T cell activation and recruitment, respectively, as well as prolonged survival. Thus, early detection of olfaction loss and blockade of pathological cell recruitment may offer potential therapeutic strategies for ECM.

Perioperative considerations of the patient with malaria

Purpose

Malaria is a life-threatening infectious disease caused by the Plasmodium parasite. Increased global travel has resulted in an escalation in the number of imported cases seen in developed countries. Patients with malaria may present for surgery in both endemic and non-endemic countries. This article reviews the perioperative considerations when managing patients with malaria.

Source

A literature review of anesthesia, perioperative care, and malaria-related articles was performed using the MEDLINE^®, EMBASE™, and Web of Science databases to identify relevant articles published in English during 1945-2014. Of the 303 articles matching the search criteria, 265 were excluded based on title and abstract. Eleven of the remaining 38 articles were relevant to anesthesia/perioperative care, and 27 articles were identified as having direct relevance to critical care medicine.

Principal findings

The majority of imported malaria cases are caused by the falciparum species, which is associated with the greatest degree of morbidity and mortality. Various organ systems may be impacted as a consequence of changes in the structure and function of parasitized erythrocytes. Preoperative assessment should focus on establishing the species of malaria, the severity of disease, assessing the degree of end-organ impairment, and initiating treatment of malaria prior to surgery. Intravenous artesunate is the treatment of choice for severe falciparum malaria. Quinine is a second-line agent but has a narrow therapeutic index and particularly hazardous side effects. Intraoperatively, attention should focus on fluid management, dynamics of cerebral blood flow, and avoidance of hypoglycemia. Postoperative care of severe cases should ideally take place in a critical care unit as there may be ongoing requirements for multi-organ support, including renal replacement therapy, ventilation, and/or inotropic support. The safety of neuraxial anesthesia has not been well studied in the setting of malaria.

Conclusions

Malaria remains one of the most devastating infectious diseases worldwide. Multiple organ systems can be impacted as a consequence of changes in structure and function of parasitized erythrocytes. Safe perioperative management requires a sound knowledge of all these potential system effects.