Interleukin-15 Complex Treatment Protects Mice from Cerebral Malaria by Inducing Interleukin-10-Producing Natural Killer Cells.

Cerebral malaria is a deadly complication of Plasmodium infection and involves blood brain barrier (BBB) disruption following infiltration of white blood cells. During experimental cerebral malaria (ECM), mice inoculated with Plasmodium berghei ANKA-infected red blood cells develop a fatal CM-like disease caused by CD8+ T cell-mediated pathology. We found that treatment with interleukin-15 complex (IL-15C) prevented ECM, whereas IL-2C treatment had no effect. IL-15C-expanded natural killer (NK) cells were necessary and sufficient for protection against ECM. IL-15C treatment also decreased CD8+ T cell activation in the brain and prevented BBB breakdown without influencing parasite load. IL-15C induced NK cells to express IL-10, which was required for IL-15C-mediated protection against ECM. Finally, we show that ALT-803, a modified human IL-15C, mediates similar induction of IL-10 in NK cells and protection against ECM. These data identify a regulatory role for cytokine-stimulated NK cells in the prevention of a pathogenic immune response.

ZBTB7B (ThPOK) Is Required for Pathogenesis of Cerebral Malaria and Protection against Pulmonary Tuberculosis.

We used a genome-wide screen in N-ethyl-N-nitrosourea (ENU)-mutagenized mice to identify genes in which recessive loss-of-function mutations protect against pathological neuroinflammation. We identified an R367Q mutation in the ZBTB7B (ThPOK) protein in which homozygosity causes protection against experimental cerebral malaria (ECM) caused by infection with Plasmodium berghei ANKA. Zbtb7bR367Q homozygous mice show a defect in the lymphoid compartment expressed as severe reduction in the number of single-positive CD4 T cells in the thymus and in the periphery, reduced brain infiltration of proinflammatory leukocytes in P. berghei ANKA-infected mice, and reduced production of proinflammatory cytokines by primary T cells ex vivo and in vivo Dampening of proinflammatory immune responses in Zbtb7bR367Q mice is concomitant to increased susceptibility to infection with avirulent (Mycobacterium bovis BCG) and virulent (Mycobacterium tuberculosis H37Rv) mycobacteria. The R367Q mutation maps to the first DNA-binding zinc finger domain of ThPOK and causes loss of base contact by R367 in the major groove of the DNA, which is predicted to impair DNA binding. Global immunoprecipitation of ThPOK-containing chromatin complexes coupled to DNA sequencing (ChIP-seq) identified transcriptional networks and candidate genes likely to play key roles in CD4+ CD8+ T cell development and in the expression of lineage-specific functions of these cells. This study highlights ThPOK as a global regulator of immune function in which alterations may affect normal responses to infectious and inflammatory stimuli.

Interferon regulatory factor 1 is essential for pathogenic CD8+ T cell migration and retention in the brain during experimental cerebral malaria.

Host immune response has a key role in controlling the progression of malaria infection. In the well-established murine model of experimental cerebral malaria (ECM) with Plasmodium berghei ANKA infection, proinflammatory Th1 and CD8+ T cell response are essential for disease development. Interferon regulatory factor 1 (IRF1) is a transcription factor that promotes Th1 responses, and its absence was previously shown to protect from ECM death. Yet the exact mechanism of protection remains unknown. Here we demonstrated that IRF1-deficient mice (IRF1 knockout) were protected from ECM death despite displaying early neurological signs. Resistance to ECM death was a result of reduced parasite sequestration and pathogenic CD8+ T cells in the brain. Further analysis revealed that IRF1 deficiency suppress interferon-γ production and delayed CD8+ T cell proliferation. CXCR3 expression was found to be decreased in pathogenic CD8+ T cells, which limited their migration to the brain. In addition, reduced expression of adhesion molecules by brain endothelial cells hampered leucocyte retention in the brain. Taken together, these factors limited sequestration of pathogenic CD8+ T cells and consequently its ability to induce extensive damage to the blood-brain barrier.

Plasmodium vivax Malaria Presenting with Multifocal Hemorrhagic Brain Infarcts in a School-going Child.

Cerebral malaria is a well-known complication of Plasmodium falciparum malaria. Over recent years, however, Plasmodium vivax also has been reported to cause cerebral malaria with or without co-infection with P. falciparum Here, we report a boy aged 10 years presenting with acute febrile encephalopathy with raised intracranial pressure to the emergency, who was later diagnosed to have P. vivax malaria. His neurological status improved gradually during 6 weeks of pediatric intensive care unit stay. We report this case to highlight the unusual radiologic findings in the patient, such as multifocal hemorrhagic infarcts in the brainstem, bilateral thalami, frontal cortex and basal ganglia, which have not been reported with P. vivax malaria.

Toxoplasma gondii upregulates interleukin-12 to prevent Plasmodium berghei-induced experimental cerebral malaria.

A chronic infection with the parasite Toxoplasma gondii has previously been shown to protect mice against subsequent viral, bacterial, or protozoal infections. Here we have shown that a chronic T. gondii infection can prevent Plasmodium berghei ANKA-induced experimental cerebral malaria (ECM) in C57BL/6 mice. Treatment with soluble T. gondii antigens (STAg) reduced parasite sequestration and T cell infiltration in the brains of P. berghei-infected mice. Administration of STAg also preserved blood-brain barrier function, reduced ECM symptoms, and significantly decreased mortality. STAg treatment 24 h post-P. berghei infection led to a rapid increase in serum levels of interleukin 12 (IL-12) and gamma interferon (IFN-γ). By 5 days after P. berghei infection, STAg-treated mice had reduced IFN-γ levels compared to those of mock-treated mice, suggesting that reductions in IFN-γ at the time of ECM onset protected against lethality. Using IL-10- and IL-12ßR-deficient mice, we found that STAg-induced protection from ECM is IL-10 independent but IL-12 dependent. Treatment of P. berghei-infected mice with recombinant IL-12 significantly decreased parasitemia and mortality. These data suggest that IL-12, either induced by STAg or injected as a recombinant protein, mediates protection from ECM-associated pathology potentially through early induction of IFN-γ and reduction in parasitemia. These results highlight the importance of early IL-12 induction in protection against ECM.

The CTLA-4 and PD-1/PD-L1 inhibitory pathways independently regulate host resistance to Plasmodium-induced acute immune pathology.

The balance between pro-inflammatory and regulatory immune responses in determining optimal T cell activation is vital for the successful resolution of microbial infections. This balance is maintained in part by the negative regulators of T cell activation, CTLA-4 and PD-1/PD-L, which dampen effector responses during chronic infections. However, their role in acute infections, such as malaria, remains less clear. In this study, we determined the contribution of CTLA-4 and PD-1/PD-L to the regulation of T cell responses during Plasmodium berghei ANKA (PbA)-induced experimental cerebral malaria (ECM) in susceptible (C57BL/6) and resistant (BALB/c) mice. We found that the expression of CTLA-4 and PD-1 on T cells correlates with the extent of pro-inflammatory responses induced during PbA infection, being higher in C57BL/6 than in BALB/c mice. Thus, ECM develops despite high levels of expression of these inhibitory receptors. However, antibody-mediated blockade of either the CTLA-4 or PD-1/PD-L1, but not the PD-1/PD-L2, pathways during PbA-infection in ECM-resistant BALB/c mice resulted in higher levels of T cell activation, enhanced IFN-γ production, increased intravascular arrest of both parasitised erythrocytes and CD8(+) T cells to the brain, and augmented incidence of ECM. Thus, in ECM-resistant BALB/c mice, CTLA-4 and PD-1/PD-L1 represent essential, independent and non-redundant pathways for maintaining T cell homeostasis during a virulent malaria infection. Moreover, neutralisation of IFN-γ or depletion of CD8(+) T cells during PbA infection was shown to reverse the pathologic effects of regulatory pathway blockade, highlighting that the aetiology of ECM in the BALB/c mice is similar to that in C57BL/6 mice. In summary, our results underscore the differential and complex regulation that governs immune responses to malaria parasites.

Changes in brain metabolites in experimental cerebral malaria infection with plasmodium berghei ANKA: a literature review.

In this paper, we have collected the findings of available literature focusing on brain metabolites by spectroscopy in the murine model of cerebral malaria disease. The literature search for experimental cerebral malaria (ECM) and spectroscopy using National Institute of Health's PubMed database provided us with 9 peer-reviewed publications. These publications have used mice infected with Plasmodium Berghei (PbA) Antwerpen-Kasapa (ANKA) strain to mimic the human infection with Plasmodium falciparum. Brain ischaemia, as depicted by increased lactate and alanine concentrations, as well as decreased aspartate and adenosine triphosphate levels, play a key role in ECM. Lowering the lactate levels by using dichloroacetate has been shown to improve survival. Significant cellular injury has also been documented through decreased N-acetylaspartate and glycerophosphocholine levels. The advantage of using spectroscopic technique provide important functional information which helps determine the aetiology, pathogenesis, progression, and monitoring of treatment as well as predicting prognosis in the clinical setting of cerebral malaria.

A novel carbon monoxide-releasing molecule fully protects mice from severe malaria.

Severe forms of malaria infection, such as cerebral malaria (CM) and acute lung injury (ALI), are mainly caused by the apicomplexan parasite Plasmodium falciparum. Primary therapy with quinine or artemisinin derivatives is generally effective in controlling P. falciparum parasitemia, but mortality from CM and other forms of severe malaria remains unacceptably high. Herein, we report the design and synthesis of a novel carbon monoxide-releasing molecule (CO-RM; ALF492) that fully protects mice against experimental CM (ECM) and ALI. ALF492 enables controlled CO delivery in vivo without affecting oxygen transport by hemoglobin, the major limitation in CO inhalation therapy. The protective effect is CO dependent and induces the expression of heme oxygenase-1, which contributes to the observed protection. Importantly, when used in combination with the antimalarial drug artesunate, ALF492 is an effective adjunctive and adjuvant treatment for ECM, conferring protection after the onset of severe disease. This study paves the way for the potential use of CO-RMs, such as ALF492, as adjunctive/adjuvant treatment in severe forms of malaria infection.

Cerebral malaria and epilepsy.

Malaria, one of the most common parasitic diseases worldwide, is responsible for more than one million deaths among African children every year. Its neurological form, known as cerebral malaria (CM) is a potential cause of epilepsy in malaria-endemic regions of the world, primarily made up for the most part by the sub-Saharan Africa. Herein, we review recent African studies that examine the association between CM and epilepsy. Three studies suggest a modestly strong association between CM and epilepsy. Furthermore, there appears little doubt that this association is causal. Speculative considerations that may explain this causal association are discussed in this review. Additional research is however required in order to determine the clinical and electrographic behavior, the underlying structural and molecular basis, and course and outcome of this condition.

Evaluation of alternative diagnostic techniques for diagnosis of cerebral malaria in a tertiary referral hospital in Bangladesh.

Five alternative techniques for diagnosis of malaria were evaluated in 124 clinically diagnosed cerebral malaria cases admitted in a tertiary hospital in Bangladesh. Clinical diagnosis of cerebral malaria was done by WHO criteria. The tests were conventional routine malaria microscopy; prolonged microscopy; dipstick antigen capture assay (Para Sight TM-F test); pigments in peripheral leucocytes and routine microscopy repeated at 12 hours interval. First four tests were done at 0 hours of hospital admission and repeat routine microscopy was added at 12 hours interval. Diagnostic capability of the test was 64%, 65%, 69%, 27% and 63% respectively. None of the tests except pigments in peripheral leucocytes was superior at initial evaluation. Only the dipstick test added 5% more diagnostic possibility compared with routine microscopy as standard. Stratification of diagnostic capability in different ways improved diagnosis 15% and 11% in smear negative cases by dipstick and prolonged microscopy respectively. It was increased by 50% (5/10 patients) with dipstick test in the smear negative patients with history of anti-malarials prior to hospital admission.

Neuroleptic malignant syndrome masked by cerebral malaria.

A 38-year-old man with an underlying psychiatric illness presented with altered sensorium and abnormal behaviour. He was febrile at 38°C and weak looking; otherwise no other abnormalities were detected. A blood film conducted for malarial parasite (BFMP) revealed Plasmodium falciparum; hence a diagnosis of cerebral malaria was made. He was treated with antimalarial drugs for 2 days prior to being transferred out to the ward following clinical improvement. He subsequently developed episodes of stupor and refusal of feeding. Following an evaluation by the psychiatrist, a diagnosis of catatonic schizophrenia was made and he was started on oral sulpiride and benhexol. Unfortunately, he developed high-grade fever at 40°C with muscle rigidity and fasciculation. The diagnosis of neuroleptic malignant syndrome (NMS) was clinched and the antipsychotics were discontinued. However he succumbed to NMS several days later due to multiorgan failure.

Cerebral malaria owing to Plasmodium vivax: case report.

Cerebral malaria is a diffuse encephalopathy associated with seizures and status epilepticus which can occur in up to one-third of children with severe malaria, particularly that caused by Plasmodium falciparum. We report a unique case of P. vivax infection complicated by status epilepticus. A 4-year-old boy was admitted to the emergency outpatient clinic with intractable seizures for the previous hour. During resuscitation, two episodes of left-focal tonic convulsions occurred and he received phenytoin. Because of a history of P. vivax infection in the family 3 months previously, a blood slide for malaria was undertaken. Thin blood smears demonstrated P. vivax. He was treated with chloroquine and primaquine. An initial EEG was normal but after 3 months of follow-up a second EEG showed generalised epileptic activity. Rarely, cerebral malaria is a presenting complication or occurs during the course of P. vivax infection. In endemic areas such as Turkey, the possibility of cerebral malaria should be considered.

Evidence that interferon-gamma plays a protective role during cerebral malaria.

BACKGROUND: The pathogenic mechanisms of cerebral malaria (CM) are unclear but are thought to involve cytokine-mediated inflammation enhanced by parasite sequestration in the brain microcirculation. The role that interferon (IFN)-gamma could play that would enhance inflammation but also reduce parasitemia is unclear. METHODS: Plasma IFN-gamma concentrations were measured by enzyme-linked immunosorbent assay in 96 children with CM and 40 children with uncomplicated malaria (UM) who had been recruited from Gabriel Toure Hospital (Bamako, Mali). We investigated the relationship between IFN- gamma concentrations and disease by nonparametric analysis. Polymorphisms in IFNG were characterized by restriction enzyme analysis or size-determination electrophoresis. Associations between polymorphisms and CM were evaluated by the family-based association test on 240 families. RESULTS: During episodes of malaria, IFN-gamma concentrations were lower in children with CM than in children with UM (P = .007). IFNG-183T (P = .009) and IFNG-183G/T (P = .013) were found to be less frequent than expected in children with CM. A trend toward association was also observed between IFNG(CA)14/(CA)14 (P = .073) and CM. The IFNG-183G/T and IFNG(CA)14/(CA)14 genotypes were more frequent in children with UM than in children with CM (odds ratio, 0.30 and 0.34, respectively). CONCLUSIONS: The low plasma IFN- gamma concentrations in children with CM and the associations between a reduced risk of CM and (1) the IFNG-183T allele (which increases gene transcription) and (2) the IFNG-183G/T genotype are consistent with the concept that IFN-gamma protects against CM.