Understanding host-parasite relationship: the immune central nervous system microenvironment and its effect on brain infections

The anti-amoebic potential of carboxamide derivatives containing sulfonyl or sulfamoyl moieties against brain-eating Naegleria fowleri

Naegleria fowleri is a free-living thermophilic flagellate amoeba that causes a rare but life-threatening infection called primary amoebic meningoencephalitis (PAM), with a very high fatality rate. Herein, the anti-amoebic potential of carboxamide derivatives possessing sulfonyl or sulfamoyl moiety was assessed against pathogenic N. fowleri using amoebicidal, cytotoxicity and cytopathogenicity assays. The results from amoebicidal experiments showed that derivatives dramatically reduced N. fowleri viability. Selected derivatives demonstrated IC50 values at lower concentrations; 1j showed IC50 at 24.65 μM, while 1k inhibited 50% amoebae growth at 23.31 μM. Compounds with significant amoebicidal effects demonstrated limited cytotoxicity against human cerebral microvascular endothelial cells. Finally, some derivatives mitigated N. fowleri-instigated host cell death. Ultimately, this study demonstrated that 1j and 1k exhibited potent anti-amoebic activity and ought to be looked at in future studies for the development of therapeutic anti-amoebic pharmaceuticals. Further investigation is required to determine the clinical relevance of our findings.

Central nervous system commitment in Chagas disease

The involvement of the central nervous system (CNS) during human acute and chronic Chagas disease (CD) has been largely reported. Meningoencephalitis is a frequent finding during the acute infection, while during chronic phase the CNS involvement is often accompanied by behavioral and cognitive impairments. In the same vein, several studies have shown that rodents infected with Trypanosoma cruzi (T. cruzi) display behavior abnormalities, accompanied by brain inflammation, in situ production of pro-inflammatory cytokines and parasitism in diverse cerebral areas, with involvement of microglia, macrophages, astrocytes, and neurons. However, the mechanisms used by the parasite to reach the brain remain now largely unknown. Herein we discuss the evidence unravelling the CNS involvement and complexity of neuroimmune interactions that take place in acute and chronic CD. Also, we provide some clues to hypothesize brain infections routes in human and experimental acute CD following oral infection by T. cruzi, an infection route that became a major CD related public health issue in Brazil.

Neurotrophic Factors in Experimental Cerebral Acanthamoebiasis

To date, no studies have addressed the role of neurotrophins (NTs) in Acanthamoeba spp. infections in the brain. Thus, to clarify the role of NTs in the cerebral cortex and hippocampus during experimental acanthamoebiasis in relation to the host immune status, the purpose of this study was to determine whether Acanthamoeba spp. may affect the concentration of brain-derived neurotrophic factor (BDNF), nerve growth factor (NGF), neurotrophin-3 (NT-3), and neurotrophin-4 (NT-4) in brain structures. Our results suggest that at the beginning of infection in immunocompetent hosts, BDNF and NT-3 may reflect an endogenous attempt at neuroprotection against Acanthamoeba spp. infection. We also observed a pro-inflammatory effect of NGF during acanthamoebiasis in immunosuppressed hosts. This may provide important information for understanding the development of cerebral acanthamoebiasis related to the immunological status of the host. However, the pathogenesis of brain acanthamoebiasis is still poorly understood and documented and, therefore, requires further research.

A restored humoral environment ameliorates acute brain injury after Angiostrongylus cantonensis infection

Circulating factors in the circulatory system support important functions of living tissues and the body. Parabiosis is a condition in which two living animals are connected using surgical methods and share a single circulatory system. Angiostrongylus cantonensis is the major cause of infectious eosinophilic meningitis, which causes severe damage to the central nervous system (CNS) and immune system. However, the mechanism of immunopathology remains largely unknown. We hypothesize that a restored humoral environment can help relieve damage to the CNS and immune system. In the present study, we found that administration of normal serum significantly reduced mortality, alleviated thymic atrophy and reduced inflammation in the brains of mice infected with A. cantonensis. We further generated parabiotic pairs between two healthy mice, one of which was then orally infected with A. cantonensis. The results showed that compared with singleton mice, mice connected with a healthy parabiotic partner were protected against CNS and immune system damage, as revealed by significantly reduced inflammation in the brain, alleviated thymic atrophy, and decreased expression of proinflammatory cytokines. These findings revealed that a healthy systemic environment can relieve damage to the CNS and immune system in infected mice, suggesting novel therapeutic approaches for diseases involving severe brain and immune system damage.

Mechanisms of the host immune response and helminth-induced pathology during Trichobilharzia regenti (Schistosomatidae) neuroinvasion in mice

Helminth neuroinfections represent serious medical conditions, but the diversity of the host-parasite interplay within the nervous tissue often remains poorly understood, partially due to the lack of laboratory models. Here, we investigated the neuroinvasion of the mouse spinal cord by Trichobilharzia regenti (Schistosomatidae). Active migration of T. regenti schistosomula through the mouse spinal cord induced motor deficits in hindlimbs but did not affect the general locomotion or working memory. Histological examination of the infected spinal cord revealed eosinophilic meningomyelitis with eosinophil-rich infiltrates entrapping the schistosomula. Flow cytometry and transcriptomic analysis of the spinal cord confirmed massive activation of the host immune response. Of note, we recorded striking upregulation of the major histocompatibility complex II pathway and M2-associated markers, such as arginase or chitinase-like 3. Arginase also dominated the proteins found in the microdissected tissue from the close vicinity of the migrating schistosomula, which unselectively fed on the host nervous tissue. Next, we evaluated the pathological sequelae of T. regenti neuroinvasion. While no demyelination or blood-brain barrier alterations were noticed, our transcriptomic data revealed a remarkable disruption of neurophysiological functions not yet recorded in helminth neuroinfections. We also detected DNA fragmentation at the host-schistosomulum interface, but schistosomula antigens did not affect the viability of neurons and glial cells in vitro. Collectively, altered locomotion, significant disruption of neurophysiological functions, and strong M2 polarization were the most prominent features of T. regenti neuroinvasion, making it a promising candidate for further neuroinfection research. Indeed, understanding the diversity of pathogen-related neuroinflammatory processes is a prerequisite for developing better protective measures, treatment strategies, and diagnostic tools.

Mass spectrometry based metabolomics for small molecule metabolites mining and confirmation as potential biomarkers for schistosomiasis - case of the Okavango Delta communities in Botswana

INTRODUCTION

Metabolomics for identifying schistosomiasis biomarkers in noninvasive samples at various infection stages is being actively explored. The literature on the traditional detection of schistosomiasis in human specimens is well documented. However, state-of-the-art technologies based on mass spectrometry have simplified the use of biomarkers for diagnostics. This review examines methods currently in use for the metabolomics of small molecules using separation science and mass spectrometry.

AREA COVERED

This article highlights the evolution of traditional diagnostic methods for schistosomiasis based on inter alia microscopy, immunology, and polymerase chain reaction. An exhaustive literature search of metabolite mining, focusing on separation science and mass spectrometry, is presented. A comparative analysis of mass spectrometry methods was undertaken, including a projection for the future.

EXPERT COMMENTARY

Mass spectrometry metabolomics for schistosomiasis will lead to biomarker discovery for noninvasive human samples. These biomarkers, together with those from other neglected tropical diseases, such as malaria and sleeping sickness, could be incorporated as arrays on a single biosensor chip and inserted into smartphones, in order to improve surveillance, monitoring, and management.

Primary Amoebic Meningoencephalitis by Naegleria fowleri: Pathogenesis and Treatments

Naegleria fowleri is a free-living amoeba (FLA) that is commonly known as the "brain-eating amoeba." This parasite can invade the central nervous system (CNS), causing an acute and fulminating infection known as primary amoebic meningoencephalitis (PAM). Even though PAM is characterized by low morbidity, it has shown a mortality rate of 98%, usually causing death in less than two weeks after the initial exposure. This review summarizes the most recent information about N. fowleri, its pathogenic molecular mechanisms, and the neuropathological processes implicated. Additionally, this review includes the main therapeutic strategies described in case reports and preclinical studies, including the possible use of immunomodulatory agents to decrease neurological damage.

Regulatory T Cells as an Escape Mechanism to the Immune Response in Taenia crassiceps Infection

Murine cysticercosis by Taenia crassiceps is a model for human neurocysticercosis. Genetic and/or immune differences may underlie the higher susceptibility to infection in BALB/cAnN with respect to C57BL/6 mice. T regulatory cells (Tregs) could mediate the escape of T. crassiceps from the host immunity. This study is aimed to investigate the role of Tregs in T. crassiceps establishment in susceptible and non-susceptible mouse strains. Treg and effector cells were quantified in lymphoid organs before infection and 5, 30, 90, and 130 days post-infection. The proliferative response post-infection was characterized in vitro. The expression of regulatory and inflammatory molecules was assessed on days 5 and 30 post-infection. Depletion assays were performed to assess Treg functionality. Significantly higher Treg percentages were observed in BALB/cAnN mice, while increased percentages of activated CD127+ cells were found in C57BL/6 mice. The proliferative response was suppressed in susceptible mice, and Treg proliferation occurred only in susceptible mice. Treg-mediated suppression mechanisms may include IL-10 and TGFβ secretion, granzyme- and perforin-mediated cytolysis, metabolic disruption, and cell-to-cell contact. Tregs are functional in BALB/cAnN mice. Therefore Tregs could be allowing parasite establishment and survival in susceptible mice but could play a homeostatic role in non-susceptible strains.

An Unusual Case of Mixed Respiratory Capillariosis in a Dog

Nematodes belonging to the genus Capillaria infect a range of domestic and wild animals. Capillaria aerophila and Capillaria boehmi cause respiratory parasitoses in dogs and wild carnivores, e.g., foxes and mustelids, although they are often overlooked in canine clinical practice. The present report describes an unusual case of a severe and mixed infection by C. aerophila and C. boehmi in a privately housed dog that showed acute and life-threatening respiratory and neurological signs. Clinic-pathologic and epizootiological implications are described and discussed.

Toxoplasmosis of the central nervous system: Manifestations vary with immune responses

Toxoplasmosis is an opportunistic infection caused by Toxoplasma gondii (TG), which affects one third of the global human population and commonly involves the central nervous system (CNS)/brain despite the so-called CNS immune privilege. Symptomatic clinical disease of TG infection is much more commonly associated with immunodeficiency; clinicopathological manifestations of CNS toxoplasmosis are linked to individual immune responses including the CNS infiltration of T-cells that are thought to prevent the disease. In patients with autoimmune diseases, immune status is complicated mainly byimmunosuppressant and/or immunomodulatory treatment but typically accompanied by infiltration of T-cells that supposedly fight against toxoplasmosis. In this article, we review characteristics of CNS toxoplasmosis comparatively in immunocompromised patients, immunocompetent patients, and patients with coexisting autoimmune diseases, as well as CNS immune responses to toxoplasmosis with a representative case to demonstrate brain lesions at different stages. In addition to general understanding of CNS toxoplasmosis, our review reveals that clinical manifestations of CNS toxoplasmosis are commonly nonspecific, and incidental pathological findings of TG infection are relatively common in immunocompetent patients and patients with autoimmune diseases (compared to immunocompromised patients); CNS immune responses such as T-cell infiltrates vary in acute and chronic lesions of brain toxoplasmosis.

A study for precision diagnosing and treatment strategies in difficult-to-treat AIDS cases and HIV-infected patients with highly fatal or highly disabling opportunistic infections: Study protocol for antiretroviral therapy timing in AIDS patients with toxoplasma encephalitis

BACKGROUND

Toxoplasma encephalitis (TE) is one of the main opportunistic infections in acquired immunodeficiency syndrome (AIDS) patients, and represents a social burden due to its high prevalence and morbidity. Concomitant antiretroviral therapy (ART), together with effective anti- toxoplasma combination therapy, is an effective strategy to treat AIDS-associated TE (AIDS/TE) patients. However, the timing for the initiation of ART after diagnosis of TE remains controversial. We therefore designed the present study to determine the optimal timing for ART initiation in AIDS/TE patients.

METHODS/DESIGN

This trial is a 17-center, randomized, prospective clinical study with 2 parallel arms. A total of 200 participants will be randomized at a 1:1 ratio into the 2 arms: the early ART initiation (≤14 days after TE diagnosis) arm and the deferred ART (>14 days after TE diagnosis) arm. The primary outcome will be the difference of mortality between the 2 arms at 48 weeks. The secondary outcomes will be the differences between the 2 arms in the changes of CD4+ counts from baseline to week 48, the rate of virologic suppression (HIV ribonucleic acid <50 copies/mL) from baseline to week 48, the incidence of TE-associated immune reconstitution inflammatory syndrome during the study period, and the incidence of adverse effects during the study period.

DISCUSSION

This present trial aims to evaluate the optimal timing for ART initiation in AIDS/TE patients, and will provide strong evidence for AIDS/TE treatment should it be successful.

TRIAL REGISTRATION

This trial was registered as one of the 12 trials under the name of a general project at the chictr.gov (http://www.chictr.org.cn/showproj.aspx?proj=35362) on February 1, 2019, and the registration number of the general project is ChiCTR1900021195.