Neurological and behavioral manifestations of cerebral malaria: An update

Neurotransmitters and molecular chaperones interactions in cerebral malaria: Is there a missing link?

Plasmodium falciparum is responsible for the most severe and deadliest human malaria infection. The most serious complication of this infection is cerebral malaria. Among the proposed hypotheses that seek to explain the manifestation of the neurological syndrome in cerebral malaria is the vascular occlusion/sequestration/mechanic hypothesis, the cytokine storm or inflammatory theory, or a combination of both. Unfortunately, despite the increasing volume of scientific information on cerebral malaria, our understanding of its pathophysiologic mechanism(s) is still very limited. In a bid to maintain its survival and development, P. falciparum exports a large number of proteins into the cytosol of the infected host red blood cell. Prominent among these are the P. falciparum erythrocytes membrane protein 1 (PfEMP1), P. falciparum histidine-rich protein II (PfHRP2), and P. falciparum heat shock proteins 70-x (PfHsp70-x). Functional activities and interaction of these proteins with one another and with recruited host resident proteins are critical factors in the pathology of malaria in general and cerebral malaria in particular. Furthermore, several neurological impairments, including cognitive, behavioral, and motor dysfunctions, are known to be associated with cerebral malaria. Also, the available evidence has implicated glutamate and glutamatergic pathways, coupled with a resultant alteration in serotonin, dopamine, norepinephrine, and histamine production. While seeking to improve our understanding of the pathophysiology of cerebral malaria, this article seeks to explore the possible links between host/parasite chaperones, and neurotransmitters, in relation to other molecular players in the pathology of cerebral malaria, to explore such links in antimalarial drug discovery.

Associations of childhood exposure to malaria with cognition and behavior outcomes: a systematic review protocol

BACKGROUND

Malaria is one of the major contributing risk factors for poor development of children living in low- and middle-income countries (LMICs). However, little is known about the specific domains of cognition and behavior that are impacted by malaria, the extent of these deficits, and the different types of the malaria spectrum that are associated with these deficits. The objective of this systematic review is to determine the association of the different types of malaria infection on cognition and behavioral outcomes among children living in LMICs.

METHODS AND ANALYSIS

We will systematically search online bibliographic databases including MEDLINE (via PubMed), CINAHL (via EBSCO), PsycINFO (via EBSCO), Embase, and The Cochrane Central Register of Controlled Trials (CENTRAL) as well as Google Scholar and bibliographies of pertinent articles. We will include studies with a comparison group (e.g., clinical trials, cohort, observational, cross-sectional case-control, and controlled before and after or interrupted-time-series studies) involving children under 18 years of age living in LMICs, as determined by the World Bank criteria, with either an active malaria infection or history of malaria. Included articles must also measure cognitive and/or behavior outcomes determined by standardized psychological assessments (questionnaire-based scales and or neurocognitive assessments). Studies will be excluded if they are not in English, lack a control group, take place in a high-income country, or if a standardized instrument was not used. Two reviewers will independently review all articles to determine if they meet eligibility criteria. Any conflicts will be resolved after discussion with a third reviewer. When a list of included articles is finalized, two reviewers will extract data to populate and then cross check within an electronic table. Risk of bias and the strength of evidence and recommendations will be assessed independently using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) criteria, and a final score will be given upon consensus. For sufficiently homogeneous data on measured outcomes in multiple studies, we will investigate the possibility of pooling data to perform a meta-analysis.

DISCUSSION

This systematic review will evaluate the evidence of the association of malaria on the cognitive and behavioral outcomes. Findings from this planned review will generate insight on the domains affected by the different forms of malaria infection and may inform subsequent malaria interventions and future research in pediatric care.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO CRD42020154777.

Heterogeneous Network Model to Identify Potential Associations Between Plasmodium vivax and Human Proteins

Integration of multiple sources and data levels provides a great insight into the complex associations between human and malaria systems. In this study, a meta-analysis framework was developed based on a heterogeneous network model for integrating human-malaria protein similarities, a human protein interaction network, and a Plasmodium vivax protein interaction network. An iterative network propagation was performed on the heterogeneous network until we obtained stabilized weights. The association scores were calculated for qualifying a novel potential human-malaria protein association. This method provided a better performance compared to random experiments. After that, the stabilized network was clustered into association modules. The potential association candidates were then thoroughly analyzed by statistical enrichment analysis with protein complexes and known drug targets. The most promising target proteins were the succinate dehydrogenase protein complex in the human citrate (TCA) cycle pathway and the nicotinic acetylcholine receptor in the human central nervous system. Promising associations and potential drug targets were also provided for further studies and designs in therapeutic approaches for malaria at a systematic level. In conclusion, this method is efficient to identify new human-malaria protein associations and can be generalized to infer other types of association studies to further advance biomedical science.

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.