Elevated cerebrospinal fluid tumour necrosis factor is associated with acute and long-term neurocognitive impairment in cerebral malaria

Subclinical Inflammation in Asymptomatic Schoolchildren With Plasmodium falciparum Parasitemia Correlates With Impaired Cognition

BACKGROUND

Subclinical inflammation and cognitive deficits have been separately associated with asymptomatic Plasmodium falciparum infections in schoolchildren. However, whether parasite-induced inflammation is associated with worse cognition has not been addressed. We conducted a cross-sectional pilot study to better assess the effect of asymptomatic P. falciparum parasitemia and inflammation on cognition in Kenyan schoolchildren.

METHODS

We enrolled 240 children aged 7-14 years residing in high malaria transmission in Western Kenya. Children performed five fluid cognition tests from a culturally adapted NIH toolbox and provided blood samples for blood smears and laboratory testing. Parasite densities and plasma concentrations of 14 cytokines were determined by quantitative PCR and multiplex immunoassay, respectively. Linear regression models were used to determine the effects of parasitemia and plasma cytokine concentrations on each of the cognitive scores as well as a composite cognitive score while controlling for age, gender, maternal education, and an interaction between age and P. falciparum infection status.

RESULTS

Plasma concentrations of TNF, IL-6, IL-8, and IL-10 negatively correlated with the composite score and at least one of the individual cognitive tests. Parasite density in parasitemic children negatively correlated with the composite score and measures of cognitive flexibility and attention. In the adjusted model, parasite density and TNF, but not P. falciparum infection status, independently predicted lower cognitive composite scores. By mediation analysis, TNF significantly mediated ~29% of the negative effect of parasitemia on cognition.

CONCLUSIONS

Among schoolchildren with PCR-confirmed asymptomatic P. falciparum infections, the negative effect of parasitemia on cognition could be mediated, in part, by subclinical inflammation. Additional studies are needed to validate our findings in settings of lower malaria transmission and address potential confounders that could affect both inflammation and cognitive performance.

Neurofilament light chain: A potential biomarker for cerebrovascular disease in children with sickle cell anaemia

Cerebrovascular injury frequently occurs in children with sickle cell anaemia (SCA). Limited access to magnetic resonance imaging and angiography (MRI-MRA) in sub-Saharan Africa impedes detection of clinically unapparent cerebrovascular injury. Blood-based brain biomarkers of cerebral infarcts have been identified in non-SCA adults. Using plasma samples from a well-characterized cross-sectional sample of Ugandan children with SCA, we explored relationships between biomarker levels and MRI-detected cerebral infarcts and transcranial Doppler (TCD) arterial velocity. Testing was performed using a 4-plex panel of brain injury biomarkers, including neurofilament light chain (NfL), a central nervous system neuron-specific protein. Mean biomarker levels from the SCA group (n = 81) were similar to those from non-SCA sibling controls (n = 54). Within the SCA group, NfL levels were significantly higher in those with MRI-detected infarcts compared to no infarcts, and higher with elevated TCD velocity versus normal velocity. Elevated NfL remained strongly associated with MRI-detected infarcts after adjusting for sex and age. All non-SCA controls and SCA participants lacking MRI-detected infarcts had low NfL levels. These data suggest potential utility of plasma-based NfL levels to identify children with SCA cerebrovascular injury. Replication and prospective studies are needed to confirm these novel findings and the clinical utility of NfL versus MRI imaging.

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

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

Cerebrospinal fluid tumor necrosis factor-alpha (TNF-α) levels in children with cerebral malaria

This prospective cross-sectional study evaluated the diagnostic and prognostic role of cerebrospinal fluid (CSF) tumor necrosis factor-alpha (TNF-α) in children with cerebral malaria (CM) and its role in the differentiation of CM from non-cerebral severe malaria. CSF TNF-α was measured using a human TNF-α enzyme-linked immunosorbent assay kit of 39 cases of CM and 19 cases of non-cerebral severe malaria. CSF TNF-α levels were significantly higher in CM (p < 0.001). Based on the receiver operating characteristics curve, a cutoff value of CSF TNF-α was 5.7 pg/ml for diagnosis of CM with sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 87.2%, 94.7%, 97.1% and 78.3% respectively. The cutoff value of CSF TNF-α was 13.7 pg/ml for predicting adverse outcomes in CM with sensitivity, specificity, PPV and NPV of 100%, 96.8%, 88.9% and 100%, respectively. However, the cutoff value of CSF TNF-α was 4.96 pg/ml for predicting adverse outcomes in non-cerebral severe malaria with a sensitivity, specificity, PPV and NPV of 100%, 94.1%, 88.9% and 100% respectively. So, CSF TNF-α is an excellent biomarker and can be used as a diagnostic and prognostic tool. More studies are needed to establish CSF TNF-α as a predictor of neurological sequelae.

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.

Elevated plasma interleukin-8 as a risk factor for mortality in children presenting with cerebral malaria

BACKGROUND

Cerebral malaria (CM) is a neuropathology which remains one of the deadliest forms of malaria among African children. The kinetics of the pathophysiological mechanisms leading to neuroinflammation and the death or survival of patients during CM are still poorly understood. The increasing production of cytokines, chemokines and other actors of the inflammatory and oxidative response by various local actors in response to neuroinflammation plays a major role during CM, participating in both the amplification of the neuroinflammation phenomenon and its resolution. In this study, we aimed to identify risk factors for CM death among specific variables of inflammatory and oxidative responses to improve our understanding of CM pathogenesis.

METHODS

Children presenting with CM (n = 70) due to P. falciparum infection were included in southern Benin and divided according to the clinical outcome into 50 children who survived and 20 who died. Clinical examination was complemented by fundoscopic examination and extensive blood biochemical analysis associated with molecular diagnosis by multiplex PCR targeting 14 pathogens in the patients' cerebrospinal fluid to rule out coinfections. Luminex technology and enzyme immunoassay kits were used to measure 17 plasma and 7 urinary biomarker levels, respectively. Data were analysed by univariate analysis using the nonparametric Mann‒Whitney U test and Pearson's Chi2 test. Adjusted and multivariate analyses were conducted separately for plasma and urinary biomarkers to identify CM mortality risk factors.

RESULTS

Univariate analysis revealed higher plasma levels of tumour necrosis factor (TNF), interleukin-1beta (IL-1β), IL-10, IL-8, C-X-C motif chemokine ligand 9 (CXCL9), granzyme B, and angiopoietin-2 and lower urinary levels of prostanglandine E2 metabolite (PGEM) in children who died compared to those who survived CM (Mann-Whitney U-test, P-values between 0.03 and < 0.0001). The multivariate logistic analysis highlighted elevated plasma levels of IL-8 as the main risk factor for death during CM (adjusted odd ratio = 14.2, P-value = 0.002). Values obtained during follow-up at D3 and D30 revealed immune factors associated with disease resolution, including plasma CXCL5, C-C motif chemokine ligand 17 (CCL17), CCL22, and urinary 15-F2t-isoprostane.

CONCLUSIONS

The main risk factor of death during CM was thus elevated plasma levels of IL-8 at inclusion. Follow-up of patients until D30 revealed marker profiles of disease aggravation and resolution for markers implicated in neutrophil activation, endothelium activation and damage, inflammatory and oxidative response. These results provide important insight into our understanding of CM pathogenesis and clinical outcome and may have important therapeutic implications.

Malaria infection and the risk of epilepsy: a meta-analysis

Epilepsy, a chronic disease of the central nervous system, is highly prevalent in malaria-endemic regions. Therefore, several studies have evaluated the associations between malaria infection and epilepsy development. A meta-analysis of observational studies published from inception to 10 May 2022 has been conducted to synthesize and pool the existing data on this topic. The relevant publications were systematically searched in PubMed/Medline, Scopus, Embase and Web of Science database collections. A random-effects meta-analysis model (REM) was utilized to generate the pooled odds ratio (OR) at 95% confidence intervals (CIs). The between-studies heterogeneity was assessed with I2, as well as several subgroups, meta-regression and sensitivity analysis were performed to identify the source of heterogeneity. Overall, 17 eligible studies containing 6285 cases and 13 909 healthy controls were included. The REM showed a significant positive association between malaria infection and epilepsy development (OR 2.36; 95% CI 1.44–3.88). In subgroup analyses, significant positive associations were observed in studies that: epilepsy was the outcome in the follow-up of patients with cerebral malaria (OR 7.10; 95% CI 3.50–14.38); used blood smear to diagnose malaria (OR 4.80; 95% CI 2.36–9.77); included only children (OR 3.92; 95% CI 1.81–8.50); published before 2010 (OR 6.39; 95% CI 4.25–9.62). Our findings indicated that patients with malaria, especially those with cerebral malaria, are at a high risk of epilepsy development; however, further well-designed and controlled studies are needed to verify the strength of the association.

Dynamics and immunomodulation of cognitive deficits and behavioral changes in non-severe experimental malaria

Data recently reported by our group indicate that stimulation with a pool of immunogens capable of eliciting type 2 immune responses can restore the cognitive and behavioral dysfunctions recorded after a single episode of non-severe rodent malaria caused by Plasmodium berghei ANKA. Here we explored the hypothesis that isolated immunization with one of the type 2 immune response-inducing immunogens, the human diphtheria-tetanus (dT) vaccine, may revert damages associated with malaria. To investigate this possibility, we studied the dynamics of cognitive deficits and anxiety-like phenotype following non-severe experimental malaria and evaluated the effects of immunization with both dT and of a pool of type 2 immune stimuli in reversing these impairments. Locomotor activity and long-term memory deficits were assessed through the open field test (OFT) and novel object recognition task (NORT), while the anxiety-like phenotype was assessed by OFT and light/dark task (LDT). Our results indicate that poor performance in cognitive-behavioral tests can be detected as early as the 12^th day after the end of antimalarial treatment with chloroquine and may persist for up to 155 days post infection. The single immunization strategy with the human dT vaccine showed promise in reversal of long-term memory deficits in NORT, and anxiety-like behavior in OFT and LDT.

Chronic cerebral aspects of long COVID, post-stroke syndromes and similar states share their pathogenesis and perispinal etanercept treatment logic

The chronic neurological aspects of traumatic brain injury, post‐stroke syndromes, long COVID‐19, persistent Lyme disease, and influenza encephalopathy having close pathophysiological parallels that warrant being investigated in an integrated manner. A mechanism, common to all, for this persistence of the range of symptoms common to these conditions is described. While TNF maintains cerebral homeostasis, its excessive production through either pathogen‐associated molecular patterns or damage‐associated molecular patterns activity associates with the persistence of the symptoms common across both infectious and non‐infectious conditions. The case is made that this shared chronicity arises from a positive feedback loop causing the persistence of the activation of microglia by the TNF that these cells generate. Lowering this excess TNF is the logical way to reducing this persistent, TNF‐maintained, microglial activation. While too large to negotiate the blood‐brain barrier effectively, the specific anti‐TNF biological, etanercept, shows promise when administered by the perispinal route, which allows it to bypass this obstruction.

Infections in the Developing Brain: The Role of the Neuro-Immune Axis

Central nervous system (CNS) infections occur more commonly in young children than in adults and pose unique challenges in the developing brain. This review builds on the distinct vulnerabilities in children's peripheral immune system (outlined in part 1 of this review series) and focuses on how the developing brain responds once a CNS infection occurs. Although the protective blood-brain barrier (BBB) matures early, pathogens enter the CNS and initiate a localized innate immune response with release of cytokines and chemokines to recruit peripheral immune cells that contribute to the inflammatory cascade. This immune response is initiated by the resident brain cells, microglia and astrocytes, which are not only integral to fighting the infection but also have important roles during normal brain development. Additionally, cytokines and other immune mediators such as matrix metalloproteinases from neurons, glia, and endothelial cells not only play a role in BBB permeability and peripheral cell recruitment, but also in brain maturation. Consequently, these immune modulators and the activation of microglia and astrocytes during infection adversely impact normal neurodevelopment. Perturbations to normal brain development manifest as neurodevelopmental and neurocognitive impairments common among children who survive CNS infections and are often permanent. In part 2 of the review series, we broadly summarize the unique challenges CNS infections create in a developing brain and explore the interaction of regulators of neurodevelopment and CNS immune response as part of the neuro-immune axis.

Association of Plasma Tau With Mortality and Long-term Neurocognitive Impairment in Survivors of Pediatric Cerebral Malaria and Severe Malarial Anemia

IMPORTANCE

Cerebral malaria (CM) and severe malarial anemia (SMA) are associated with persistent neurocognitive impairment (NCI) among children in Africa. Identifying blood biomarkers of acute brain injury that are associated with future NCI could allow early interventions to prevent or reduce NCI in survivors of severe malaria.

OBJECTIVE

To investigate whether acutely elevated tau levels are associated with future NCI in children after CM or SMA.

DESIGN, SETTING, AND PARTICIPANTS

This prospective cohort study was conducted at Mulago National Referral Hospital in Kampala, Uganda, from March 2008 to October 2015. Children aged 1.5 to 12 years with CM (n = 182) or SMA (n = 162) as well as community children (CC; n = 123) were enrolled in the study. Data analysis was conducted from January 2020 to May 2021.

EXPOSURE

CM or SMA.

MAIN OUTCOMES AND MEASURES

Enrollment plasma tau levels were measured using single-molecule array detection technology. Overall cognition (primary) and attention and memory (secondary) z scores were measured at 1 week and 6, 12, and 24 months after discharge using tools validated in Ugandan children younger than 5 years or 5 years and older.

RESULTS

A total of 467 children were enrolled. In the CM group, 75 (41%) were girls, and the mean (SD) age was 4.02 (1.92) years. In the SMA group, 59 (36%) were girls, and the mean (SD) age was 3.45 (1.60) years. In the CC group, 65 (53%) were girls, and the mean (SD) age was 3.94 (1.92) years. Elevated plasma tau levels (>95th percentile in CC group; >6.43 pg/mL) were observed in 100 children (55%) with CM and 69 children (43%) with SMA (P < .001). In children with CM who were younger than 5 years, elevated plasma tau levels were associated with increased mortality (odds ratio [OR], 3.06; 95% CI, 1.01-9.26; P = .048). In children with CM who were younger than 5 years at both CM episode and follow-up neurocognitive testing, plasma tau levels (log10 transformed) were associated with worse overall cognition scores over 24-month follow-up (β = -0.80; 95% CI, -1.32 to -0.27; P = .003). In children with CM who were younger than 5 years at CM episode and 5 years or older at follow-up neurocognitive testing, plasma tau was associated with worse scores in attention (β = -1.08; 95% CI, -1.79 to -0.38; P = .003) and working memory (β = -1.39; 95% CI, -2.18 to -0.60; P = .001).

CONCLUSIONS AND RELEVANCE

In this study, plasma tau, a marker of injury to neuronal axons, was elevated in children with CM or SMA and was associated with mortality and persistent NCI in children with CM younger than 5 years.

How diseases caused by parasites allowed a wider understanding of disease in general: my encounters with parasitology in Australia and elsewhere over the last 50 years

This is an account of how it can prove possible to carve a reasonable scientific career by following what brought most scientific thrill rather than pursue a safe, institution-directed, path. The fascination began when I noticed, quite unexpectedly, that the normal mouse immune response causes Babesia microti to die, en masse, inside circulating red cells. It eventuated that prior Bacillus Calmette Guerin infection caused the same outcome, even before the protozoal infection became patent. It also rendered mice quite immune, long term. I acquired an obsession about this telling us how little we know. Surrounded by basic immunologists, parasitologists and virologists in London, I had been given, in the days that funding was ample, the opportunity to follow any promising lead with a free hand. Through Bacillus Calmette Guerin, this meant stumbling through a set of phenomena that were in their infancies, and could be explained only through nebulous novel soluble mediators such as TNF, described the following year as causing the in vivo necrosis of tumours in mice. Beginning with malarial disease pathogenesis, I followed TNF wherever it led, into innate immunity, acute and chronic infections, neurophysiology and neurodegenerative diseases, in all of which states awareness of the role of this cytokine is still growing fast. Many of these steps can be illustrated and expanded upon in parasitic diseases. Covering the importance of TNF in the pathogenesis of neurodegenerative disease has proved to be highly illuminating, scientifically and otherwise. But the insights it has given me into understanding the temptations to which patent-owners can succumb when faced with opportunities to put money before people is not for the faint hearted. Clearly, parasitologists inhabit a much more common-good yet science-orientated, civilised, world.

Plasma angiopoietin-2 is associated with age-related deficits in cognitive sub-scales in Ugandan children following severe malaria

Background

Elevated angiopoietin-2 (Angpt-2) concentrations are associated with worse overall neurocognitive function in severe malaria survivors, but the specific domains affected have not been elucidated.

Methods

Ugandan children with severe malaria underwent neurocognitive evaluation a week after hospital discharge and at 6, 12 and 24 months follow-up. The relationship between Angpt-2 concentrations and age-adjusted, cognitive sub-scale z-scores over time were evaluated using linear mixed effects models, adjusting for disease severity (coma, acute kidney injury, number of seizures in hospital) and sociodemographic factors (age, gender, height-for-age z-score, socio-economic status, enrichment in the home environment, parental education, and any preschool education of the child). The Mullen Scales of Early Learning was used in children < 5 years and the Kaufman Assessment Battery for Children 2nd edition was used in children ≥ 5 years of age. Angpt-2 levels were measured on admission plasma samples by enzyme-linked immunosorbent assay. Adjustment for multiple comparisons was conducted using the Benjamini–Hochberg Procedure of False Discovery Rate.

Results

Increased admission Angpt-2 concentration was associated with worse outcomes in all domains (fine and gross motor, visual reception, receptive and expressive language) in children < 5 years of age at the time of severe malaria episode, and worse simultaneous processing and learning in children < 5 years of age at the time of severe malaria who were tested when ≥ 5 years of age. No association was seen between Angpt-2 levels and cognitive outcomes in children ≥ 5 years at the time of severe malaria episode, but numbers of children and testing time points were lower for children ≥ 5 years at the time of severe malaria episode.

Conclusion

Elevated Angpt-2 concentration in children with severe malaria is associated with worse outcomes in multiple neurocognitive domains. The relationship between Angpt-2 and worse cognition is evident in children < 5 years of age at the time of severe malaria presentation and in selected domains in older years.

Elevated Cerebrospinal Fluid Tau Protein Concentrations on Admission Are Associated With Long-term Neurologic and Cognitive Impairment in Ugandan Children With Cerebral Malaria

BACKGROUND

Elevated concentrations of cerebrospinal fluid (CSF) tau, a marker of axonal injury, have been associated with coma in severe malaria (cerebral malaria [CM]). However, it is unknown whether axonal injury is related to long-term neurologic deficits and cognitive impairment in children with CM.

METHODS

Admission CSF tau concentrations were measured in 145 Ugandan children with CM and compared to clinical and laboratory factors and acute and chronic neurologic and cognitive outcomes.

RESULTS

Elevated CSF tau concentrations were associated with younger age, increased disease severity (lower glucose and hemoglobin concentrations, malaria retinopathy, acute kidney injury, and prolonged coma duration, all P < .05), and an increased CSF:plasma albumin ratio, a marker of blood-brain barrier breakdown (P < .001). Admission CSF tau concentrations were associated with the presence of neurologic deficits at hospital discharge, and at 6, 12, and 24 months postdischarge (all P ≤ .02). After adjustment for potential confounding factors, elevated log10-transformed CSF tau concentrations correlated with worse cognitive outcome z scores over 2-year follow-up for associative memory (β coefficient, -0.31 [95% confidence interval [CI], -.53 to -.10]) in children <5 years of age, and for overall cognition (-0.69 [95% CI, -1.19 to -.21]), attention (-0.78 [95% CI, -1.34 to -.23]), and working memory (-1.0 [95% CI, -1.68 to -.31]) in children ≥5 years of age (all P < .006).

CONCLUSIONS

Acute axonal injury in children with CM is associated with long-term neurologic deficits and cognitive impairment. CSF tau concentrations at the time of the CM episode may identify children at high risk of long-term neurocognitive impairment.

Predictors of outcome in childhood Plasmodium falciparum malaria

Plasmodium falciparum malaria is classified as either uncomplicated or severe, determining clinical management and providing a framework for understanding pathogenesis. Severe malaria in children is defined by the presence of one or more features associated with adverse outcome, but there is wide variation in the predictive value of these features. Here we review the evidence for the usefulness of these features, alone and in combination, to predict death and other adverse outcomes, and we consider the role that molecular biomarkers may play in augmenting this prediction. We also examine whether a more personalized approach to predicting outcome for specific presenting syndromes of severe malaria, particularly cerebral malaria, has the potential to be more accurate. We note a general need for better external validation in studies of outcome predictors and for the demonstration that predictors can be used to guide clinical management in a way that improves survival and long-term health.

Clinical presentation and immunological features of Post-Malaria Neurologic Syndrome: a case report and review of literature

Background

Malaria still represents a major health threat, in terms of both morbidity and mortality. Complications of malaria present a diversified clinical spectrum, with neurological involvement leading to the most serious related-conditions. The authors recently encountered a case of a 60-year old Italian man presenting with confusion, language disturbances and Parkinson-like syndrome 3 weeks after complete remission from severe Plasmodium falciparum cerebral malaria. Chemical and microbiological analysis revealed aseptic meningitis, diffuse encephalitis and abnormal immune-activation. Re-infection and recrudescence of infection were excluded. Further analysis excluded paraneoplastic and autoimmune causes of encephalitis. A diagnosis of Post-Malaria Neurological Syndrome (PMNS) was finally formulated and successfully treated with high dose of steroids.

Methods

A systematic research of current literature related to PMNS was performed.

Results

151 cases of PMNS were included, the majority of which occurred after severe P. falciparum infections. Four main clinical pattern were identified: 37% of the cases presented as “classical” PMNS, 36% presented as delayed cerebellar ataxia (DCA), 18% resembled acute inflammatory demyelinating polyneuropathy (AIDP), and 8% presented as acute disseminated encephalomyelitis (ADEM)-like form. Differentiation between different forms was not always simple, as clinical and radiological findings frequently overlap. Overall, in almost all of the tested cases, cerebrospinal fluid was found pathological; EEG revealed nonspecific encephalopathy in 30% of classical PMNS and 67% ADEM; imaging tests were found abnormal in 92% of ADEM-like forms. Pathogenesis remains unclear. An autoimmune mechanism is the most corroborated pathogenic hypothesis. Overall, the majority of PMNS cases revert without specific treatment. In most severe forms, high dose steroids, intravenous immunoglobulins, and plasmapheresis have been shown to improve symptoms.

Conclusions

PMNS is a disabling complication of malaria. The overall incidence is not known, due to frequent misdiagnosis and under-reporting. Pathogenesis is not also fully understood, but rapid response to immune-modulating treatment along with similarities to auto-immune neurological disease, strongly support a dysregulated immunological genesis of this condition. The lack of randomized controlled studies regarding therapeutic approaches is a major unmet need in this setting. A systematic collection of all the PMNS cases would be desirable, in order to increase awareness of this rare condition and to prospectively investigate the most appropriate management.

Oxidative and nitrosative stresses in cerebral malaria: can we target them to avoid a bad prognosis?

There is currently a global effort to reduce malaria morbidity and mortality. However, malaria still results in the deaths of thousands of people every year. Malaria is caused by Plasmodium spp., parasites transmitted through the bite of an infected female Anopheles mosquito. Treatment timing plays a decisive role in reducing mortality and sequelae associated with the severe forms of the disease such as cerebral malaria (CM). The available antimalarial therapy is considered effective but parasite resistance to these drugs has been observed in some countries. Antimalarial drugs act by increasing parasite lysis, especially through targeting oxidative stress pathways. Here we discuss the roles of reactive oxygen species and reactive nitrogen intermediates in CM as a result of host-parasite interactions. We also present evidence of the potential contribution of oxidative and nitrosative stress-based antimalarial drugs to disease treatment and control.

Zoonotic and vector-borne parasites and epilepsy in low-income and middle-income countries

Zoonotic and vector-borne parasites are important preventable risk factors for epilepsy. Three parasitic infections - cerebral malaria, Taenia solium cysticercosis and onchocerciasis - have an established association with epilepsy. Parasitoses are widely prevalent in low-income and middle-income countries, which are home to 80% of the people with epilepsy in the world. Once a parasitic infection has taken hold in the brain, therapeutic measures do not seem to influence the development of epilepsy in the long term. Consequently, strategies to control, eliminate and eradicate parasites represent the most feasible way to reduce the epilepsy burden at present. The elucidation of immune mechanisms underpinning the parasitic infections, some of which are parasite-specific, opens up new therapeutic possibilities. In this Review, we explore the pathophysiological basis of the link between parasitic infections and epilepsy, and we consider preventive and therapeutic approaches to reduce the burden of epilepsy attributable to parasitic disorders. We conclude that a concerted approach involving medical, veterinary, parasitological and ecological experts, backed by robust political support and sustainable funding, is the key to reducing this burden.

Host-Based Prognostic Biomarkers to Improve Risk Stratification and Outcome of Febrile Children in Low- and Middle-Income Countries

Fever is one of the leading causes for pediatric medical consultation and the most common symptom at clinical presentation in low- and middle-income countries (LMICs). Most febrile episodes are due to self-limited infections, but a small proportion of children will develop life-threatening infections. The early recognition of children who have or are progressing to a critical illness among all febrile cases is challenging, and there are currently no objective and quantitative tools to do so. This results in increased morbidity and mortality among children with impending life-threatening infections, whilst contributing to the unnecessary prescription of antibiotics, overwhelming health care facilities, and harm to patients receiving avoidable antimicrobial treatment. Specific fever origin is difficult to ascertain and co-infections in LMICs are common. However, many severe infections share common pathways of host injury irrespective of etiology, including immune and endothelial activation that contribute to the pathobiology of sepsis (i.e., pathogen "agnostic" mechanisms of disease). Importantly, mediators of these pathways are independent markers of disease severity and outcome. We propose that measuring circulating levels of these factors can provide quantitative and objective evidence to: enable early recognition of severe infection; guide patient triage and management; enhance post-discharge risk stratification and follow up; and mitigate potential gender bias in clinical decisions. Here, we review the clinical and biological evidence supporting the clinical utility of host immune and endothelial activation biomarkers as components of novel rapid triage tests, and discuss the challenges and needs for developing and implementing such tools.

Human Microglia Respond to Malaria-Induced Extracellular Vesicles

Microglia are the chief immune cells of the brain and have been reported to be activated in severe malaria. Their activation may drive towards neuroinflammation in cerebral malaria. Malaria-infected red blood cell derived-extracellular vesicles (MiREVs) are produced during the blood stage of malaria infection. They mediate intercellular communication and immune regulation, among other functions. During cerebral malaria, the breakdown of the blood–brain barrier can promote the migration of substances such as MiREVs from the periphery into the brain, targeting cells such as microglia. Microglia and extracellular vesicle interactions in different pathological conditions have been reported to induce neuroinflammation. Unlike in astrocytes, microglia–extracellular vesicle interaction has not yet been described in malaria infection. Therefore, in this study, we aimed to investigate the uptake of MiREVs by human microglia cells and their cytokine response. Human blood monocyte-derived microglia (MoMi) were generated from buffy coats of anonymous healthy donors using Ficoll-Paque density gradient centrifugation. The MiREVs were isolated from the Plasmodium falciparum cultures. They were purified by ultracentrifugation and labeled with PKH67 green fluorescent dye. The internalization of MiREVs by MoMi was observed after 4 h of co-incubation on coverslips placed in a 24-well plate at 37 °C using confocal microscopy. Cytokine-gene expression was investigated using rt-qPCR, following the stimulation of the MoMi cells with supernatants from the parasite cultures at 2, 4, and 24 h, respectively. MiREVs were internalized by the microglia and accumulated in the perinuclear region. MiREVs-treated cells increased gene expression of the inflammatory cytokine TNFα and reduced gene expression of the immune suppressive IL-10. Overall, the results indicate that MiREVs may act on microglia, which would contribute to enhanced inflammation in cerebral malaria.

Evaluating Immunopathogenic Biomarkers During Severe Malaria Illness as Modifiers of the Neuropsychologic Benefits of Computer Cognitive Games Rehabilitation in Ugandan Children

BACKGROUND

We explored 3 immunopathogenic biomarkers collected during acute malaria illness as potential moderators of gains from a computerized cognitive rehabilitation training (CCRT) intervention.

METHOD

Von Willebrand Factor (vWF), tumor necrosis factor (TNF) and Regulated on Activation, Normal T Expressed and Secreted (RANTES) were assayed from plasma and cerebral spinal fluid (CSF) of children during acute severe malaria anemia or cerebral malaria. Two years after acute malaria illness, 150 surviving children and 150 nonmalaria community controls (CCs) from their households 6-12 years old entered a 3-arm randomized controlled trial of titrating and nontitrating CCRT against no CCRT. Tests of cognition [Kaufman Assessment Battery for Children (KABC)], Tests of Variables of Attention and Achenbach Child Behavior Checklist (CBCL) were administered before and after 24 CCRT sessions over a 3-month period, and at 1-year follow-up. Differences in outcomes by trial arms and biomarker levels were evaluated using linear mixed effects models.

RESULTS

Severe malaria survivors with lower levels of vWF, lower CSF levels of TNF and higher levels of plasma and CSF RANTES had better KABC cognitive performance after both titrating and nontitrating CCRT compared with no CCRT. For the CBCL, high plasma RANTES was associated with no benefit from either the titrating and nontitrating CCRT, whereas high TNF plasma was predictive of the benefit for both interventions. These biomarker moderating effects were not evident for CC children.

CONCLUSIONS

Severe malaria immunopathogenic biomarkers may be related to poorer long-term brain/behavior function as evidenced by diminished benefit from a computerized cognitive rehabilitation intervention.

What causes severe malaria and its complications in children? Lessons learned over the past 15 years

Over the past 15 years, malaria mortality has reduced by approximately 50%. However, malaria still causes more than 400,000 deaths annually, most of which occur in African children under 5 years of age. Significant advances in understanding the pathogenesis of the disease provide a basis for future work to prevent severe malaria and its complications. Herein, we provide an overview of advances in our understanding of severe malaria in African children over the past 15 years, highlighting key complications and identifying priorities to further reduce malaria-associated mortality.

Parameters of stochastic models for electroencephalogram data as biomarkers for child's neurodevelopment after cerebral malaria

The objective of this study was to test statistical features from the electroencephalogram (EEG) recordings as predictors of neurodevelopment and cognition of Ugandan children after coma due to cerebral malaria. The increments of the frequency bands of EEG time series were modeled as Student processes; the parameters of these Student processes were estimated and used along with clinical and demographic data in a machine-learning algorithm for the prediction of children's neurodevelopmental and cognitive scores 6 months after cerebral malaria illness. The key innovation of this work is in the identification of stochastic EEG features that can serve as language-independent markers of the impact of cerebral malaria on the developing brain. The results can enhance prognostic determination of which children are in most need of rehabilitative interventions, which is especially important in resource-constrained settings such as sub-Saharan Africa.

MRI of Iron Oxide Nanoparticles and Myeloperoxidase Activity Links Inflammation to Brain Edema in Experimental Cerebral Malaria

Purpose To investigate the association of inflammation and brain edema in a cerebral malaria (CM) mouse model with a combination of bis-5-hydroxy-tryptamide-diethylenetriaminepentaacetate gadolinium, referred to as MPO-Gd, and cross-linked iron oxide nanoparticle (CLIO-NP) imaging. Materials and Methods Female wild-type (n = 23) and myeloperoxidase (MPO) knock-out (n = 5) mice were infected with the Plasmodium berghei ANKA strain from May 2016 to July 2018. Seven healthy mice served as control animals. At a Rapid Murine Coma and Behavioral Scale (RMCBS) score of less than 15, mice underwent MRI at 9.4 T and received gadodiamide, MPO-Gd, or CLIO-NPs. T1-weighted MRI was used to assess MPO activity, and T2*-weighted MRI was used to track CLIO-NPs. Immunofluorescent staining and flow cytometric analyses characterized CLIO-NPs, MPO, endothelial cells, and leukocytes. An unpaired, two-tailed Student t test was used to compare groups; Spearman correlation analysis was used to determine the relationship of imaging parameters to clinical severity. Results MPO-Gd enhancement occurred in inflammatory CM hotspots (olfactory bulb > rostral migratory stream > brainstem > cortex, P < .05 for all regions compared with control mice; mean olfactory bulb signal intensity ratio: 1.40 ± 0.07 vs 0.96 ± 0.01, P < .01). The enhancement was reduced in MPO knockout mice (mean signal intensity ratio at 60 minutes: 1.13 ± 0.04 vs 1.40 ± 0.07 in CM, P < .05). Blood-brain barrier compromise was suggested by parenchymal gadolinium enhancement, leukocyte recruitment, and endothelial activation. CLIO-NPs accumulated mainly intravascularly and at the vascular endothelium. CLIO-NPs were also found in the choroid plexus, indicating inflammation of the ventricular system. Blood-cerebrospinal fluid barrier breakdown showed correlation with brain swelling (r²: 0.55, P < .01) and RMCBS score (r²: 0.75, P < .001). Conclusion Iron oxide nanoparticle imaging showed strong inflammatory involvement of the microvasculature in a murine model of cerebral malaria. Furthermore, bis-5-hydroxy-tryptamide-diethylenetriaminepentaacetate gadolinium imaging depicted parenchymal and intraventricular inflammation. This combined molecular imaging approach links vascular inflammation to breakdown of the blood-brain barrier and blood-cerebrospinal fluid barrier that correlate with global brain edema and disease severity. © RSNA, 2018 Online supplemental material is available for this article. See also the editorial by Kiessling in this issue.

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.

Pathophysiology, clinical presentation, and treatment of coma and acute kidney injury complicating falciparum malaria

PURPOSE OF REVIEW

Cerebral impairment and acute kidney injury (AKI) are independent predictors of mortality in both adults and children with severe falciparum malaria. In this review, we present recent advances in understanding the pathophysiology, clinical features, and management of these complications of severe malaria, and discuss future areas of research.

RECENT FINDINGS

Cerebral malaria and AKI are serious and well recognized complications of severe malaria. Common pathophysiological pathways include impaired microcirculation, due to sequestration of parasitized erythrocytes, systemic inflammatory responses, and endothelial activation. Recent MRI studies show significant brain swelling in both adults and children with evidence of posterior reversible encephalopathy syndrome-like syndrome although targeted interventions including mannitol and dexamethasone are not beneficial. Recent work shows association of cell-free hemoglobin oxidation stress involved in the pathophysiology of AKI in both adults and children. Paracetamol protected renal function likely by inhibiting cell-free-mediated oxidative stress. It is unclear if heme-mediated endothelial activation or oxidative stress is involved in cerebral malaria.

SUMMARY

The direct causes of cerebral and kidney dysfunction remain incompletely understood. Optimal treatment involves prompt diagnosis and effective antimalarial treatment with artesunate. Renal replacement therapy reduces mortality in AKI but delayed diagnosis is an issue.

Synthetic oleanane triterpenoids enhance blood brain barrier integrity and improve survival in experimental cerebral malaria

Background

Cerebral malaria (CM) is a severe complication of Plasmodium falciparum infection associated with high mortality and neurocognitive impairment in survivors. New anti-malarials and host-based adjunctive therapy may improve clinical outcome in CM. Synthetic oleanane triterpenoid (SO) compounds have shown efficacy in the treatment of diseases where inflammation and oxidative stress contribute to pathogenesis.

Methods

A derivative of the SO 2-cyano-3,12-dioxooleana-1,9-dien-28-oic acid (CDDO), CDDO-ethyl amide (CDDO-EA) was investigated for the treatment of severe malaria in a pre-clinical model. CDDO-EA was evaluated in vivo as a monotherapy as well as adjunctive therapy with parenteral artesunate in the Plasmodium berghei strain ANKA experimental cerebral malaria (ECM) model.

Results

CDDO-EA alone improved outcome in ECM and, given as adjunctive therapy in combination with artesunate, it significantly improved outcome over artesunate alone (p = 0.009). Improved survival was associated with reduced inflammation, enhanced endothelial stability and blood–brain barrier integrity. Survival was improved even when administered late in the disease course after the onset of neurological symptoms.

Conclusions

These results indicate that SO are a new class of immunomodulatory drugs and support further studies investigating this class of agents as potential adjunctive therapy for severe malaria.

Cytokines and Chemokines in Cerebral Malaria Pathogenesis

Cerebral malaria is among the major causes of malaria-associated mortality and effective adjunctive therapeutic strategies are currently lacking. Central pathophysiological processes involved in the development of cerebral malaria include an imbalance of pro- and anti-inflammatory responses to Plasmodium infection, endothelial cell activation, and loss of blood-brain barrier integrity. However, the sequence of events, which initiates these pathophysiological processes as well as the contribution of their complex interplay to the development of cerebral malaria remain incompletely understood. Several cytokines and chemokines have repeatedly been associated with cerebral malaria severity. Increased levels of these inflammatory mediators could account for the sequestration of leukocytes in the cerebral microvasculature present during cerebral malaria, thereby contributing to an amplification of local inflammation and promoting cerebral malaria pathogenesis. Herein, we highlight the current knowledge on the contribution of cytokines and chemokines to the pathogenesis of cerebral malaria with particular emphasis on their roles in endothelial activation and leukocyte recruitment, as well as their implication in the progression to blood-brain barrier permeability and neuroinflammation, in both human cerebral malaria and in the murine experimental cerebral malaria model. A better molecular understanding of these processes could provide the basis for evidence-based development of adjunct therapies and the definition of diagnostic markers of disease progression.