No full-text available
To read the full-text of this research,
you can request a copy directly from the authors.
Cytokine and chemokine responses in a cerebral malaria-susceptible or -resistant strain of mice to Plasmodium berghei ANKA infection: early chemokine expression in the brain
Abstract
A comparative study was carried out on cytokine and chemokine responses in a cerebral malaria (CM)-susceptible or -resistant strain of mice (C57BL/6 or BALB/c respectively) in Plasmodium berghei ANKA infection. C57BL/6 mice died by 10 days after infection when parasitemia was approximately 15-20% with cerebral symptoms, while BALB/c mice survived until week 3 after infection. Although both strains showed T(h)1-skewed responses on day 4 after infection, significantly higher levels of IFN-gamma, tumor necrosis factor (TNF)-alpha and NO were observed during the course of the infection in BALB/c, suggesting that T(h)1 responses are involved in the resistance. Interestingly, in the brain, both strains expressed IFN-inducible protein of 10 kDa (IP-10) and monocyte chemotactic protein (MCP)-1 genes as early as at 24 h post-infection, whereas some differences were observed between both strains thereafter, i.e. enhanced expression of RANTES in C57BL/6, and of IFN-gamma and TNF-alpha in BALB/c respectively. Moreover, the expression of IP-10 and MCP-1 genes in KT-5, an astrocyte cell line, was induced in vitro upon stimulation with a crude antigen of malaria parasites. These results suggest that the direct involvement of brain parenchymal cells takes place in response to plasmodial infection, providing a new aspect to analyze possible mechanisms of CM. This is the first report on the chemokine expression in neuroglial cells in response to malaria infection.
... Expression of immunological markers is also recorded 3 days after infection of C57BL/6 mice with PbA manifested as increased expression of PD-1 (programmed cell death protein) in the cerebellum, CTLA-4 (cytotoxic T lymphocyte associated with protein 4) and LAG-3 (lymphocyte activation gene 3: protein encoded by the LAG3 gene) in the hippocampus, as well as reduced expression of CXCL-4 in the hippocampus 37 . These data indicate that the systemic inflammation already in progress at days 3 and 4 of infection 45,46 could modulate the brain function leading to cognitive behavioural changes detectable even in the absence of clinical signs of patent cerebral commitment. ...
... Microglia activation is recorded even before the overwhelming cerebral inflammation and development of the clinical signs of CM, at day 4 post-PbA infection 19,52 . The serum levels of proinflammatory cytokines also increase around 3-4 days after PbA infection in C75BL/6 mice 45,46 . The observation of early behavioural changes (12 days after malaria treatment), points to a potential reversible (and not preventable) effect of the immune stimuli (unpublished observations). ...
... Treg cells are a subset of T cells with immunomodulatory function, important for immune and neuronal homeostasis under physiological conditions, and for the control of pathological immune responses [54][55][56] They perform their function mainly via secretion of IL-10 and TGFβ, anti-inflammatory/regulatory cytokines 54-56 as documented in rodent models 45,46 . The neuroprotective activity of Treg cells, through a mechanism that may involve IL-10 secretion, has been described in murine models of Parkinson's disease, HIV-1-associated neurodegeneration, amyotrophic lateral sclerosis and stroke [57][58][59][60] . ...
The immune system plays a role in the maintenance of healthy neurocognitive function. Different patterns of immune response triggered by distinct stimuli may affect nervous functions through regulatory or deregulatory signals, depending on the properties of the exogenous immunogens. Here, we investigate the effect of immune stimulation on cognitive-behavioural parameters in healthy mice and its impact on cognitive sequelae resulting from non-severe experimental malaria. We show that immune modulation induced by a specific combination of immune stimuli that induce a type 2 immune response can enhance long-term recognition memory in healthy adult mice subjected to novel object recognition task (NORT) and reverse a lack of recognition ability in NORT and anxiety-like behaviour in a light/dark task that result from a single episode of mild Plasmodium berghei ANKA malaria. Our findings suggest a potential use of immunogens for boosting and recovering recognition memory that may be impaired by chronic and infectious diseases and by the effects of ageing.
... For instance, Plasmodium can cause the development of cerebral malaria where infected red blood cells aggregate in the vasculature of the brain. Subsequent recruitment of immune cells exasperates inflammation at this site with CCL2 dependent recruitment of monocytes followed by CXCR3 dependent T cell trafficking [116,117]. Further pathology occurs with secretion of CCL3 and CCL4, which augment lymphocyte migration to the brain and facilitate the breakdown of the blood-brain barrier [118]. ...
... Toxoplasma [15] Plasmodium [158] Leishmania [81,159] CXCL10 Encephalitis Plasmodium [116,117] Trypanosoma [121,123] [115] Pathogen Clearance CXCL10 T cell recruitment to liver Leishmania [112] ...
... Plasmodium[116] Schistosoma[132] ...
Parasites are diverse eukaryotic pathogens that can have complex life cycles. Their clearance, or control within a mammalian host requires the coordinated effort of the immune system. The cell types recruited to areas of infection can combat the disease, promote parasite replication and survival, or contribute to disease pathology. Location and timing of cell recruitment can be crucial. In this review, we explore the role chemokines play in orchestrating and balancing the immune response to achieve optimal control of parasite replication without promoting pathology.
... Adicionalmente, parece haver um seqüestro de plaquetas para o sítio da inflamação promovido pela presença do aglomerado de hemácias parasitadas, o que, como em outras doenças inflamatórias, pode contribuir para a isquemia (Sun et al, 2003;Wassmer et al, 2006 (Skimming et al., 2003;Komlósi et al., 2006;Chatterj et al., 2007). com ração e água ad libitum (Percário, 1994;Scardoel et al., 1996). ...
... Cada uma das substâncias citadas anteriormente parece exercer papel protetor nos acometimentos pulmonares em geral, em especial nas síndromes de deficiência respiratória.Quanto às complicações cerebrais, elas parecem ocupar maior espaço nas publicações da comunidade científica que se propõe a estudar esta doença. Os trabalhos referentes a esta área encontram-se distribuídos nos mais diversos campos de atuação das ciências biomédicas, tais como: imunologia(Lepenies et al, 2007; Vigário et al,2007;Nie et al, 2007; deWalick et al, 2007; John et al, 2008; Randall et al,2008), biologia celular e molecular(Ding-Zhou et al,2003;Lopansri et al, 2006;Machado et al, 2006), patologia(Sun et al, 2003; Penet et al,2005; Wassmer et al,2006;Pouvelle et al, 2007) e bioquímica oxidativa (Jung et al, 2006; van Leyen et al, 2006; Min et al, 2006; Cho et al, 2007; Penet et al, 2007; Cuddihy et al, 2008; Dhangadamajhi et al, 2009). Tal fato não representa surpresa, já que essas complicações são as principais responsáveis pelos óbitos de humanos infectados pelo Plasmodium falciparum (WHO, 2009).Coincidentemente, o edema cerebral, assim como o pulmonar, parece determinar o quadro patológico da malária severa(Lopes et al, 1987). ...
p>PhD. Thesis containing research data related to the article " INHIBITION OF NITRIC OXIDE SYNTHESIS BY DEXAMETHASONE INCREASES SURVIVAL RATE IN Plasmodium berghei- INFECTED MICE ", to be published in Malaria Journal.</p
... Infection of C57BL/6 mice with P. berghei ANKA (1 Â 10 5 infected erythrocytes/mouse) resulted in early death due to cerebral malaria-like symptoms, caused mainly by an inflammatory cytokine storm [5,25]. Although BALB/c mice were more resistant to that same level of infection than the C57BL/6 mice, they also experienced early death due to the same symptoms and cause [5,25]. ...
... Infection of C57BL/6 mice with P. berghei ANKA (1 Â 10 5 infected erythrocytes/mouse) resulted in early death due to cerebral malaria-like symptoms, caused mainly by an inflammatory cytokine storm [5,25]. Although BALB/c mice were more resistant to that same level of infection than the C57BL/6 mice, they also experienced early death due to the same symptoms and cause [5,25]. Thus, although the immune responses during P. berghei ANKA infection were not completely identical between C57BL/6 mice and BALB/c mice, we clearly demonstrated that IL-25, IL-33 and TSLP are not essential for host defense against P. berghei ANKA in both mouse lines, despite the finding that the pattern of mRNA expression for these cytokines was altered in various tissues such as the brain, liver, lung and spleen from the infected mice. ...
IL-25, IL-33 and TSLP, which are produced predominantly by epithelial cells, can induce production of Th2-type cytokines such as IL-4, IL-5 and/or IL-13 by various types of cells, suggesting their involvement in induction of Th2-type cytokine-associated immune responses. It is known that Th2-type cytokines contribute to host defense against malaria parasite infection in mice. However, the roles of IL-25, IL-33 and TSLP in malaria parasite infection remain unclear. Thus, to elucidate this, we infected wild-type, IL-25-/-, IL-33-/- and TSLP receptor (TSLPR)-/- mice with Plasmodium berghei (P. berghei) ANKA, a murine malaria strain. The expression levels of IL-25, IL-33 and TSLP mRNA were changed in the brain, liver, lung and spleen of wild-type mice after infection, suggesting that these cytokines are involved in host defense against P. berghei ANKA. However, the incidence of parasitemia and survival in the mutant mice were comparable to in the wild-type mice. These findings indicate that IL-25, IL-33 and TSLP are not critical for host defense against P. berghei ANKA.
... Consistent with its association to cerebral disease, attention has been mainly focused on brain tissue. Astrocytes have been found to upregulate CXCL10 in response to a crude parasite extract, suggesting that these cells are a source of this chemokine during infection (23). High levels of this chemokine have also been detected in the cerebrospinal fluid of children that succumbed to CM (14). ...
... Previous in vitro and in vivo studies have shown that nonhematopoietic cells including astrocytes (19,23), brain endothelial cells (20), and neurons (19) produce CXCL10 in response to P. berghei ANKA, suggesting a role for these cells in the recruitment of CXCR3 + leukocytes (21) to the brain of infected animals. Unexpectedly, the bone marrow irradiation chimera approach used in this study revealed that despite having nonhematopoietic cells capable of producing CXCL10, CXCL10 2/2 . ...
CXCL10, or IFN-γ-inducible protein 10, is a biomarker associated with increased risk for Plasmodium falciparum-mediated cerebral malaria (CM). Consistent with this, we have previously shown that CXCL10 neutralization or genetic deletion alleviates brain intravascular inflammation and protects Plasmodium berghei ANKA-infected mice from CM. In addition to organ-specific effects, the absence of CXCL10 during infection was also found to reduce parasite biomass. To identify the cellular sources of CXCL10 responsible for these processes, we irradiated and reconstituted wild-type (WT) and CXCL10(-/-) mice with bone marrow from either WT or CXCL10(-/-) mice. Similar to CXCL10(-/-) mice, chimeras unable to express CXCL10 in hematopoietic-derived cells controlled infection more efficiently than WT controls. In contrast, expression of CXCL10 in knockout mice reconstituted with WT bone marrow resulted in high parasite biomass levels, higher brain parasite and leukocyte sequestration rates, and increased susceptibility to CM. Neutrophils and inflammatory monocytes were identified as the main cellular sources of CXCL10 responsible for the induction of these processes. The improved control of parasitemia observed in the absence of CXCL10-mediated trafficking was associated with a preferential accumulation of CXCR3(+)CD4(+) T follicular helper cells in the spleen and enhanced Ab responses to infection. These results are consistent with the notion that some inflammatory responses elicited in response to malaria infection contribute to the development of high parasite densities involved in the induction of severe disease in target organs.
... Chemokines and their receptors are crucial in regulating the mobilization and deployment of immune cells in response to pathogen challenge, including in ECM. Gene expression analyses of brain samples comparing ECMsusceptible to ECM-resistant (BALB/c or CD8 knockout) mice have uncovered differential expression of CCR3, CCR4, CXCR3, CCL2 (MCP-1), CCL3 (MIP-1α), CCL5 (RANTES), CCL6-9, CCL12, CCL25, and CXCL9-123334353637383940. While these global analyses of whole brain homogenates point towards the importance of chemokines and chemokine receptors in ECM pathogenesis , they do not address the question of which receptor-ligand pairs in particular direct CD8 + T cell migration to the brain. ...
... Mice lacking CXCL9 or CXCL10 were each partially protected from ECM in one study [44] , whereas another group reported nearcomplete protection in CXCL10-deficient mice, associated with retention of T cells in the spleen [46]. Targeted inhibition of CXCL10 with either monoclonal antibody or atorvastatin also improved survival in the ECM model [47, 46] Author's personal copy also upregulated during PbA infection, albeit to lesser extents than CXCL9 and CXCL10 [33, 44, 39, 40, 45] . To our knowledge , studies focusing on the role of CCR5 ligands (CCL3-5) in ECM pathogenesis have yet to be performed. ...
Cerebral malaria (CM) is one the major complications occurring during malaria infection. The mechanisms leading to this syndrome are still not completely understood. Although it is clear that parasite sequestration is the key initiation factor, the downstream pathological processes are still highly debated. The experimental cerebral malaria (ECM) model, in which susceptible mice are infected with Plasmodium berghei ANKA, has led to the identification of CD8(+) T cells as the major mediator of ECM death. In this review, we discuss the recent advances and future developments in the understanding of the role of CD8(+) T cells in CM.
... In light of these findings, we hypothesized that other cytokines and chemokines that are important in serious central nervous system (CNS) infections, such bacterial meningitis and viral encephalitis, might also be important in systemic manifestations of cerebral malaria. For this reason we investigated, in children with CM, serum levels of additional chemokines (monocyte chemoattractant protein-1 (MCP-1) [2], and interleukin-8 (IL-8) [3]), and pro-inflammatory (granulocyte-colony stimulating factor (G-CSF) [4]) and anti-inflammatory (interleukin-1 receptor antagonist (IL-1ra) [5,6]) cytokines that have been implicated in the pathogenesis of other serious CNS and systemic infections and that have been associated with malaria pathogenesis pathways in previous murine or human malaria studies [7][8][9][10]. ...
... Mouse models of CM with P. bergheii ANKA infection have suggested a role for MCP-1, an a-chemokine that attracts monocytes, in the pathogenesis of CM [8], but the role of MCP-1 in human subjects has been assessed previously only in placental malaria [7]. In the present study, we demonstrated that levels of MCP-1 are elevated in both UM and CM. ...
Animal models suggest that cytokines and chemokines play a role in cerebral malaria (CM) pathogenesis, but levels of a number of cytokines and chemokines thought to be important in the pathogenesis of other infectious diseases are not well characterized in children with CM. Serum levels of granulocyte-colony stimulating factor (G-CSF), interleukin-1 receptor antagonist (IL-1ra), interleukin-8 (IL-8) and monocyte chemoattractant protein-1 (MCP-1) were measured in 77 children with CM, 70 children with uncomplicated malaria (UM) and 63 healthy community children (CC) in Uganda. Children with CM had elevated serum levels of IL-1ra and IL-8 as compared to children with UM (median levels in pg/ml, 11,891 vs. 6510, P=0.05, and 63 vs. 41, P=0.01, respectively). Children with CM who died (n=4) had higher serum levels than survivors of IL-1ra (median levels in pg/ml, 65,757 vs. 10,355, P=0.02), G-CSF (709 vs. 117, P=0.02), and MCP-1 (1275 vs. 216, P=0.03) but not IL-8 (76 vs. 62, P=NS). Elevated IL-1ra levels are associated with increased disease severity in children with malaria, and very elevated levels of IL-1ra, G-CSF and MCP-1 are seen in children who die of CM.
... Furthermore, sequestered monocytes and macrophages are more abundant in pediatric patients with cerebral malaria than in those with noncerebral malaria or nonmalarial encephalopathy [112]. The accumulation of leukocytes in the brains of patients and mice with cerebral malaria is evidence of activation of the cytokine/chemokine cascade, which has been shown in experimental and human studies [106,113]. The expression of monocyte-secreted cytokines and chemokines, such as TNF, CXC-10, CCL2, and RANTES, varies with mouse genotype and correlates with resistance versus susceptibility to disease [113]. ...
... The accumulation of leukocytes in the brains of patients and mice with cerebral malaria is evidence of activation of the cytokine/chemokine cascade, which has been shown in experimental and human studies [106,113]. The expression of monocyte-secreted cytokines and chemokines, such as TNF, CXC-10, CCL2, and RANTES, varies with mouse genotype and correlates with resistance versus susceptibility to disease [113]. Moreover the deletion of adhesion molecules, such as amb2 or adb2, was shown to have protective effects in experimental cerebral malaria [114,115] (A. ...
The possibility of free radical reactions occurring in biological processes led to the development and employment of novel methods and techniques focused on determining their existence and importance in normal and pathological conditions. For this reason the use of nitrones for spin trapping free radicals became widespread in the 1970s and 1980s, when surprisingly the first evidence of their potent biological properties was noted. Since then widespread exploration and demonstration of the potent biological properties of phenyl-tert-butylnitrone (PBN) and its derivatives took place in preclinical models of septic shock and then in experimental stroke. The most extensive commercial effort made to capitalize on the potent properties of the PBN-nitrones was for acute ischemic stroke. This occurred during 1993-2006, when the 2,4-disulfonylphenyl PBN derivative, called NXY-059 in the stroke studies, was shown to be safe in humans and was taken all the way through clinical phase 3 trials and then was deemed to be ineffective. As summarized in this review, because of its excellent human safety profile, 2,4-disulfonylphenyl PBN, now called OKN-007 in the cancer studies, was tested as an anti-cancer agent in several preclinical glioma models and shown to be very effective. Based on these studies this compound is now scheduled to enter into early clinical trials for astrocytoma/glioblastoma multiforme this year. The potential use of OKN-007 in combination with neurotropic compounds such as the lanthionine ketamine esters is discussed for glioblastoma multiforme as well as for various other indications leading to dementia, such as aging, septic shock, and malaria infections. There is much more research and development activity ongoing for various indications with the nitrones, alone or in combination with other active compounds, as briefly noted in this review.
... The parasite strain causes death in untreated mice after 7-10 days of infection, with parasitemia reaching 10-20% [5]. Factors such as the route of infection and parasite inoculum may influence the onset of mortality in P. berghe, ANKAinfected BALB/c mice, with deaths occurring as early as day 6 after infection [34][35][36]. Mice were infected, treated, and sampled as previously described [37,38], with a few modifications. Briefly, blood was collected from P. bergheiinfected mice and used to inoculate intraperitoneally 20 mice (1 × 10 6 P. berghei-infected red blood cells per animal). ...
Background:
Emergence of Plasmodium resistance to antimalarial drugs presents a major drawback in efforts to control malaria. To address this problem, there is an urgent and continuous need for the development of new and effective antimalarial agents. Senna occidentalis (L.) link extract has exhibited in vitro antiplasmodial activity in many pharmacological studies. To our knowledge, data on its in vivo antimalarial efficacy is still very limited. A recent study demonstrated that polar extracts from the plant roots inhibit Plasmodium berghei proliferation in a mouse model. This study further describes the efficacy and safety of a methanolic root extract of the plant as an antimalarial agent by demonstrating its effect on hematological, biochemical, and histological parameters of Plasmodium berghei-infected BALB/c mice.
Methods:
Rane's test, a curative approach, was used to evaluate the antimalarial efficacy of Senna occidentalis methanolic root extract in Plasmodium berghei-infected BALB/c mice. The effect of the extract on both hematological and biochemical parameters was evaluated using automated analyzers. Kidney, liver, lung, spleen, and brain tissues were harvested from euthanized mice and examined for changes in organ architecture.
Results:
This study demonstrates that methanolic root extract of Senna occidentalis significantly inhibited Plasmodium berghei parasitemia in BALB/c mice (p < 0.01). Infected mice that were treated with the extract depicted a significantly low level of total leucocytes (p < 0.01), red blood cell distribution width (p < 0.01), and a significantly high hemoglobin concentration (p < 0.001) compared to the infected animals that were administered with the vehicle only. The infected animals that were treated with the extract exhibited a significantly low level of urea, creatinine, bilirubin, and alkaline phosphatase (p < 0.05), compared to the infected animals that were given the vehicle only. The level of sodium, potassium and chloride ions, lymphocytes, granulocytes, hematocrit (HCT), mean corpuscular volume (MCV), mean corpuscular hemoglobin (MCH), mean corpuscular hemoglobin concentration, total protein, albumin, aspartate aminotransferase (AST), alanine transaminase (ALT), alkaline phosphatase (ALP), total platelets, mean platelet volume (MPV), and platelet distribution width of the infected animals treated with the extract was not significantly different from those of the infected animals that were given the vehicle only (p > 0.05). The extract alleviated organ pathological changes in the infected mice. The extract did not induce any remarkable adverse effect on the growth, hematological, and biochemical parameters of uninfected animals (p > 0.05). In addition, administration of the extract did not alter the gross appearance and histological architecture of the organs, implying that the extract was well tolerated in mice.
Conclusions:
Senna occidentalis methanolic root extract exhibited good antimalarial activity against Plasmodium berghei and may be safe in mice.
... We further assessed the serum levels of IFN-γ, TNF, IL-10, IL-6, IL-12p70, and MCP-1 at 0 h (time of infection; as Fig. 1D), 24 h, and 5 days after injection of sporozoites into prestimulated mice. C57Bl/6 mice that developed ECM were shown to exhibit high levels of serum IFN-γ, TNF, and MCP-1 prior to the onset of neurological signs [10,11,44]. Consistent with this observation, PBS-and ODN 1826 Control-treated mice had significant increases in these cytokines on day 5 after sporozoite infection (Fig. 7). ...
Recognition of pathogen-associated molecular patterns (PAMPs) through Toll-like receptors (TLRs) plays a pivotal role in first-line pathogen defence. TLRs are likely also triggered during a Plasmodium infection in vivo by parasite-derived components. However, the contribution of innate responses to liver infection and to the subsequent clinical outcome of a blood infection is not well understood. To assess the potential effects of enhanced TLR-signalling on Plasmodium infection, we systematically examined the effect of agonist-primed immune responses to sporozoite inoculation in the P. berghei/ C57Bl/6 murine malaria model. We could identify distinct stage-specific effects on the course of infection after stimulation with two out of four TLR-ligands tested. Priming with a TLR9 agonist induced killing of pre-erythrocytic stages in the liver that depended on macrophages and the expression of iNOS. These factors have previously not been recognised as antigen-independent effector mechanisms against Plasmodium liver-stages. Priming with TLR4 and -9 agonists also translated into blood stage-specific protection against experimental cerebral malaria (ECM). These insights are relevant to the activation of TLR signalling pathways by adjuvant systems of anti-malaria vaccine strategies. The protective role of TLR4-activation against ECM might also explain some unexpected clinical effects observed with pre-erythrocytic vaccine approaches.
This article is protected by copyright. All rights reserved
... Mice infected with P. chabaudi showed a reduction in the levels of CX3CL1 in the hippocampus and alterations in social and anxietylike behaviors [106]. In addition, CCL5 is increased in the brain of patients with CM and in ECM [108,109]. During a systemic inflammation, endothelial cells secrete CCL5, causing the microglia to express the CCL5 receptor and infiltrate the NVU, in order to protect the BBB. ...
Malaria is caused by Plasmodium infection and remains a serious public health problem worldwide, despite control efforts. Malaria can progress to severe forms, affecting multiple organs, including the brain causing cerebral malaria (CM). CM is the most severe neurological complication of malaria, and cognitive and behavior deficits are commonly reported in surviving patients. The number of deaths from malaria has been reducing in recent years, and as a consequence, neurological sequelae have been more evident. Neurological damage in malaria might be related to the neuroinflammation, characterized by glia cell activation, neuronal apoptosis and changes in the blood-brain barrier (BBB) integrity. The neurovascular unit (NVU) is responsible for maintaining the homeostasis of the BBB. Endothelial and pericytes cells in the cerebral microvasculature and neural cells, as astrocytes, neurons, and microglia, compose the NVU. The NVU can be disturbed by parasite metabolic products, such as heme and hemozoin, or cytokines that can promote activation of endothelial and glial cells and lead to increased BBB permeability and subsequently neurodegeneration. In this review, we will approach the main changes that happen in the cells of the NVU due to neuroinflammation caused by malaria infection, and elucidate how the systemic pathophysiology is involved in the onset and progression of CM.
... NO is a component of the innate immune system, and is involved in both the pathogenesis and control of several types of viral, bacterial and parasitic infections (Bogdan, 2001). Furthermore, NO is able to modulate the immune response via the regulation of apoptosis and the upregulation of cytokine mRNA expression (Hanum et al., 2003). The regulation of NO production in tuberculosis appears to be very complex, due to the ability of various mycobacterial cell wall components to stimulate the release of NO (Underhill, 1999). ...
The immune system is a dynamic network of cells and cytokines are the major mediators of immune responses which combat pathogens. Based on the cytokine production, effector T cells differentiate into subsets known as Th1, Th2, Th17 or Treg (T regulatory). This system serves as a barrier to intracellular pathogens, bacterial infections and stimulates the production of reactive oxygen species (ROS), reactive nitrogen intermediates (RNI) and nitric oxide (NO), which diffuses across membranes and engulfs intracellular pathogens. Oxidative stress occurs when ROS, reactive nitrogen species (RNS) production and antioxidant defences become imbalanced. Oxidative stress generated by infected cells produces a substantial amount of free radicals which enables killing of intracellular pathogens. Intracellular pathogens are exposed to endogenous ROS as part of normal aerobic respiration, also aexogenous ROS and RNS are generated by the host immune system in response to infection. Nanoparticles which are designed for drug delivery are capable of trapping the desired drug in the particles which protects the drug from enzymatic degradation in a biological system. The small (subcellular) size of nanoparticles enables higher intracellular uptake of the drug which results in the reduction of the concentration of free drugs reducing their toxic effect. Research on the modulation of immune response and oxidative stress using nanoparticles used to encapsulate drugs has yet to be explored fully. In this review we illustrate the immune activation and generation of oxidative stress properties which are mediated by nanoparticle encapsulated drug delivery systems which can make the therapy more effective in case of diseases caused by intracellular pathogens.
... High levels of CXCL10 have been detected in the cerebrospinal fluid of children that succumbed to CM (Armah et al., 2007). In mice, CXCL10 expression has been observed in brain endothelial cells (Campanella et al., 2008;Miu et al., 2008;Sorensen et al., 2018), neurons (Campanella et al., 2008), astrocytes (Hanum et al., 2003;Miu et al., 2008) and microglia (Ioannidis et al., 2016). In addition, neutrophils and monocytes that are recruited to the brain during rodent malaria infection (Ioannidis et al., 2016;Sorensen et al., 2018) have been found to be sources of CXCL10 that control the recruitment of CXCR3 + leucocytes involved in the development of CM, suggesting an important role for leucocyte derived CXCL10 in the induction of severe malaria disease symptoms. ...
The CXCR3 chemokine CXCL10 or IFN- γ inducible protein 10 (IP-10) has been identified as an important biomarker of cerebral malaria (CM) mortality in children. Studies in mouse malaria infection models have shown that CXCL10 blockade alleviates brain intravascular inflammation and protects infected mice from CM. Despite the key role that CXCL10 plays in the development of CM, the leucocytic sources of CXCL10 in response to human malaria are not known. Here we investigated CXCL10 responses to Plasmodium falciparum in peripheral blood mononuclear cells (PBMCs). We found that PBMCs from malaria-unexposed donors produce CXCL10 in response to P. falciparum and that this response is IFN- γ -dependent. Moreover, CD14 ⁺ monocytes were identified as the main leucocytic sources of CXCL10 in peripheral blood, suggesting an important role for innate immune responses in the activation of this pathway involved in the development of symptomatic malaria.
... Since the parasites were present in the brain, and KCC1 is expressed ubiquitously 21 , we postulated that the Kcc1 M935K mutation might cause alterations to some of these immune cell populations in the brain resulting in a stimulation of the immune response and impairment of parasite growth or increase clearance of the parasites. Therefore, the relative amounts of CD4+ and CD8+ T cells were measured by flow cytometry in the brain, blood, spleen, and thymus, both in uninfected mice, and before the mice succumbed to ECM, where the inflammatory response is expected to be highest 22,23 . Consistent with the hypothesis that KCC1 M935K/M935K mice are resistant to ECM, differences in CD4+ and CD8+ T cells were observed in the brain (Fig. 4A,B), but not in the blood, spleen, or thymus (Fig. 4C,D and S4). ...
Plasmodium falciparum malaria causes half a million deaths per year, with up to 9% of this mortality caused by cerebral malaria (CM). One of the major processes contributing to the development of CM is an excess of host inflammatory cytokines. Recently K+ signaling has emerged as an important mediator of the inflammatory response to infection; we therefore investigated whether mice carrying an ENU induced activation of the electroneutral K+ channel KCC1 had an altered response to Plasmodium berghei. Here we show that Kcc1M935K/M935K mice are protected from the development of experimental cerebral malaria, and that this protection is associated with an increased CD4+ and TNFa response. This is the first description of a K+ channel affecting the development of experimental cerebral malaria.
... On day 4 after i.p. inoculation of infected red blood cells, parasitaemia measured in BALB/c and C57BL/6 mice amounted 9.9% and 13.1% (preliminary, comparative experiment) and 6.5% and 7.5% (control groups of the neem study). However, from day 6 to 9, C57BL/6 mice showed a rapid increase in parasitaemia and signs of clinical illness, whereas BALB/c mice displayed a slower parasite proliferation and signs of disease only by day 12. Very similar patterns of parasite proliferation have been observed in the two mouse strains in other studies conducted with P. berghei [21,22] and with Plasmodium yoelii [23]. Exploring cytokine response in the course of P. berghei infection, the relatively slower parasite proliferation in BALB/c mice during the second week of infection has been associated to markedly higher levels of the Th2 cytokines, namely IL4 from day 5 of infection and IL10 from day 7 onwards, indicating the onset of a Th2-orchestrated humoral response in this mouse strain [22]. ...
Background
Medicinal plant research may contribute to develop new pharmacological control tools for vector borne diseases, such as malaria.
Methods
The effects of methanol extracts (ME) obtained from seed kernel of ripe and unripe Azadirachta indica fruits were studied on erythrocytic proliferation of the rodent malaria parasite Plasmodium berghei strain ANKA and on mice pro-inflammatory response, as evaluated by measuring the matrix-metalloproteinase-9 (MMP-9) and tumour necrosis factor (TNF) plasma levels, in two mouse strains (C57BL/6 and BALB/c) which are considered as prototypical of Th1 and Th2 immune response, respectively.
Results
ME obtained from seed kernel of unripe Azadirachta indica fruits decreased by about 30% the proportion of erythrocytes infected with the malaria parasite in C57BL/6 mice in the 4 days suppressive test. In this treatment group, MMP-9 and TNF levels were notably higher than those measured in the same mouse strain treated with the anti-malarial drug artesunate, Azadirachta indica kernel extracts from ripe fruits or solvent. In BALB/c mice, treatment with kernel extracts did not influence parasitaemia. MMP-9 and TNF levels measured in this mouse strain were notably lower than those recorded in C57BL/6 mice and did not vary among treatment groups.
Conclusions
The effects of the ME on the parasite-host interactions appeared to be mouse strain-dependent, but also related to the ripening stage of the neem fruits, as only the unripe fruit seed kernel extracts displayed appreciable bioactivity.
Electronic supplementary material
The online version of this article (10.1186/s12936-019-2671-8) contains supplementary material, which is available to authorized users.
... Reports indicate the role of cell death proteases [28,31], cytotoxic proteases [35] and cytokines [19] in ECM pathogenesis. Elevated levels of cell death proteases are associated with the cytoskeletal proteins, fodrin [26], spectrin [47] and NF (L) breakdown [14]. ...
Cerebral malaria is a complex, acute, neurological disease characterised by a sudden onset of cerebral symptoms. This disease is manifested as initial arousable stage that is followed by an unarousable coma and eventually death. Parasite burden and CD8+ T cell count in the brain determines the disease outcome. Cytotoxic CD8+ T cell-derived Granzyme-b is required for the development of experimental cerebral malaria (ECM), but the mechanism of pathogenesis is not known. Here, we show that CD8+ T cells infiltrate in to the brain during ECM releasing Granzyme-b that is cytotoxic to neuronal cells. Granzyme-b kills neuronal cells through direct cytotoxicity and also by activating neuronal caspase-3 and calpain1 via cytoskeletal breakdown. Our results showed the increased expression of cell adhesion molecules and chemokine receptors in the brain and their associated infiltration of T cells during ECM.
... This reason could support the loss of one animal in the 12.5-mg/kg trioxaquine treatment group even after parasitaemia monitoring had shown complete clearance. These results are in agreement with other previously related studies using the same experimental animals, which noted manifestation of neurological symptoms of CM between days 6 and 9 pi [18,19,27] and death in untreated animals by day 10 pi [28]. Recrudescence was also reported in artesunate-treated animals even at higher doses of 32 and 64 mg/kg, with all the treated animals succumbing to the infection and quinine being effective only at higher doses >120 mg/kg, which were not well tolerated by the experimental animals [29]. ...
Background
The emergence of multidrug-resistant strains of Plasmodium falciparum poses a great threat of increased fatalities in cases of cerebral and other forms of severe malaria infections in which parenteral artesunate monotherapy is the current drug of choice. The study aimed to investigate in a mouse model of human cerebral malaria whether a trioxaquine chemically synthesized by covalent linking of a 4,7-dichloroquinoline pharmacophore to artesunate through a recent drug development approach termed ‘covalent bitherapy’ could improve the curative outcomes in cerebral malaria infections.
Methods
Human cerebral malaria rodent model, the C57BL/6 male mice were infected intraperitoneally (ip) with Plasmodium berghei ANKA and intravenously (iv) treated with the trioxaquine from day 8 post-infection (pi) at 12.5 and 25 mg/kg, respectively, twice a day for 3 days. Treatments with the trioxaquine precursors (artesunate and 4,7-dichloroquine), and quinine were also included as controls. In vivo safety evaluation for the trioxaquine was done according to Organization for Economic Co-operation and Development (OECD) guidelines 423, where female Swiss albino mice were orally administered with either 300 or 2000 mg/kg of the trioxaquine and monitored for signs of severity, and or mortality for 14 days post-treatment.
Results
The trioxaquine showed a potent and a rapid antiplasmodial activity with 80% parasite clearance in the first 24 h for the two dosages used. Long-term parasitaemia monitoring showed a total parasite clearance as the treated mice survived beyond 60 days post-treatment, with no recrudescence observed. Artesunate treated mice showed recrudescence 8 days post-treatment, with all mice in this group succumbing to the infection. Also, 4,7-dichloroquinoline and quinine did not show any significant parasitaemia suppression in the first 24 h post-treatment, with the animals succumbing to the infection.
Conclusion
Covalent bitherapy proves to be a viable source of urgently needed new anti-malarials for management of cerebral malaria, and this polypharmacology approach could be a potential strategy to protect artesunate from parasite resistance and in potentially improving clinical outcomes in severe forms of malaria infections.
... Additionally, the C57BL/6 mice also produced lower levels of the plasmodicidal nitric oxide molecule after Plasmodium infection. In contrast, the cerebral malaria-resistant BALB/c mice produced significantly higher levels of NO after Plasmodium berghei infection than did the C57BL/6 mice; these opposing effects of infection on NO production in P. berghei-infected C57BL/6 and BALB/c mice were previously observed by Hanun et al. (2003) in spleen cells. The lower production of molecules involved in anti-parasite defense might explain the high parasitemia observed in the infected-C57BL/6 mice and might also contribute to the severity of the cerebral disease observed in this model. ...
Proinflammatory responses are associated with the severity of cerebral malaria. NO, H2O2, eicosanoid and PPAR-γ are involved in proinflammatory responses, but regulation of these factors is unclear in malaria. This work aimed to compare the expression of eicosanoid-forming-enzymes in cerebral malaria-susceptible CBA and C57BL/6 and −resistant BALB/c mice. Mice were infected with Plasmodium berghei ANKA, and the survival rates and parasitemia curves were assessed. On the sixth day post-infection, cyclooxygenase-2 and 5-lipoxygenase in brain sections were assessed by immunohistochemistry, and, NO, H2O2, lipid bodies, and PPAR-γ expression were assessed in peritoneal macrophages. The C57BL/6 had more severe disease with a lower survival time, higher parasitemia and lower production of plasmodicidal NO and H2O2 molecules than BALB/c. Enhanced COX-2 and 5-LOX expression were observed in brain tissue cells and vessels from C57BL/6 mice, and these mice expressed higher constitutive PPAR-γ levels. There was no translocation of PPAR-γ from cytoplasm to nucleus in macrophages from these mice. CBA mice had enhanced COX-2 expression in brain tissue cells and vessels and also lacked PPAR-γ cytoplasm-to-nucleus translocation. The resistant BALB/c mice presented higher survival time, lower parasitemia and higher NO and H2O2 production on the sixth day post-infection. These mice did not express either COX-2 or 5-LOX in brain tissue cells and vessels. Our data showed that besides the high parasite burden and lack of microbicidal molecules, an imbalance with high COX-2 and 5-LOX eicosanoid expression and a lack of regulatory PPAR-γ cytoplasm-to-nucleus translocation in macrophages were observed in mice that develop cerebral malaria.
... Stimulation by PbA-iRBCs also induced the production of TNF-a by astrocytes and microglia, suggesting an additional contribution of these glial cells in the pathophysiology of ECM. In fact and as shown for macrophage-like cells, iRBCs-derived microvesicles may be involved in triggering TNF-a production by glial cells Mantel et al., 2013).Glial cells were already shown to produce TNF-a and IP10 during infection, but triggering factors have not been described previously (Hanum, Hayano, and Kojima, 2003;Medana, Hunt, and Chaudhri, 1997). ...
Astrocytes and microglia are activated during cerebral malaria (CM) and contribute to the production and release of several mediators during neuroinflammatory processes. Whether these changes are the consequence of a direct crosstalk between glial cells and the malarial parasite and how these cells participate in the pathogenesis of CM is not yet clear. We therefore examined the interaction of astrocytes and microglia with Plasmodium berghei ANKA-infected red blood cells using primary cell cultures derived from newborn C57BL/6 mice. We observed a dynamic transfer of vesicles from the parasite to astrocytes within minutes of contact, and the phagocytosis of infected red blood cells by microglia. Differential gene expression studies using the Affymetrix GeneChip® microarray, and quantitative PCR analyses showed the increase in expression of the set of genes belonging to the immune response network in parasite activated astrocytes and microglia. Interestingly, expression of these genes was also significantly upregulated in brains of mice dying from CM compared with uninfected mice or infected mice that did not develop the neuropathology. Accumulation of parasite-derived vesicles within astrocytes, and the phagocytosis of infected red blood cells by microglia induced a subsequent increase in interferon gamma inducible protein 10 (IP10) in both the brain and plasma of infected mice at the onset of CM, confirming a role for this molecule in CM pathogenesis. Altogether, these observations point to a possible role for glial cells in the neuropathological processes leading to CM. GLIA 2016
... Previous research and other studies in this area have revealed a significant pro-oxidant state in parasite infection and its association with severe anemia and cerebral cases [8,11]. On the other hand, cytokines are reported to play a significant role in the evolution of severe malaria infection [14,15]. The production and up-regulation of cytokines in response to plasmodium infection are responsible for the development of complications such as cerebral malaria. ...
Reactive oxygen species (ROS) are reported to be involved in human Cerebral Malaria (CM). To assess the
extent of oxidative stress, we have investigated the biomarker of lipid peroxidation, Malondialdehyde (MDA) and its co
relation with levels of pro-inflammatory cytokines with malaria severity. The present study was designed to measure
Thiobarbituric acid reactive substances (TBARS) for the MDA assay to delineate the oxidative stress in various organs
(brain, liver and spleen) of Plasmodium berghei ANKA infected Swiss albino mice. Further mRNA levels of Tumor
Necrosis Factor-α (TNF-α), Interleukin -1β (IL-1β) and Interleukin-6 (IL-6) were measured by qRT-PCR in the organs of
mice according to severity of malaria. Result of this study showed that the MDA levels were significantly higher (P <
0.05) in the brain, liver and spleen of infected mice compared with the non-infected control group respectively. A study
observed highly up regulation of TNF-α between the day 5 and 9 with peak production being detected on the 9th day, and
subsequently decreased between the 11th and 13th day. In the brain, spleen and liver IL-1β and IL-6 mRNA were
significantly up-regulated (P<0.0001) and persisted throughout the course of infection. It might be concluded from the
findings of the present study that the oxidative stress response induced by the plasmodium species may trigger the
inflammatory cytokine responses in malaria severity and thereby contributes to the pathogenesis of the disease; however
the interplay between the oxidative response and inflammatory activity in disease virulence needs further study.
Keywords: Experimental Severe Malaria, P.berghei ANKA, Lipid Peroxidation, Malondialdehyde (MDA), Proinflammatory cytokine, TNF-α, IL-1β, IL-6
... Based on the efficacy of HCE against P. falciparum in vitro, the effect of this compound on the survival and parasitaemia using an in vivo murine model of malaria was evaluated. The employed model was suitable for the analysis since that BALB/c mice infected with P. berghei ANKA have resistance to the development of severe malaria (cerebral) and frequently die later due to anemia and high parasitaemia (Moumaris et al. 1995;Hanum et al. 2003). It is important to emphasize that, in the current study, the treatment was initiated only after all the animals had detectable parasitaemia, on day 7 post-infection (Fig. 4), which allowed the evaluation of the therapeutic activity of HCE against malaria. ...
In an effort to identify novel therapeutic alternatives for the treatment of malaria, the present study evaluated the antimalarial effect of the crude hydroalcoholic extract (HCE) from the leaves of Chenopodium ambrosioides L. For this purpose, the molecular affinity between the total proteins from erythrocytes infected with Plasmodium falciparum and HCE or chloroquine was evaluated by surface plasmon resonance (SPR). Subsequently, the plasmodicidal potential of HCE was assessed in a P. falciparum culture. Using BALB/c mice infected with Plasmodium berghei intraperitoneally (ip.), we evaluated the effects of ip. treatment, for three consecutive days (day 7, 8, and 9 after infection), with chloroquine (45 mg/kg) or HCE (5 mg/kg), considering the survival index and the parasitaemia. The groups were compared to an untreated control group that receives only PBS at the same periods. The results indicated that HCE could bind to the total proteins of infected erythrocytes and could inhibit the parasite growth in vitro (IC50 = 25.4 g/mL). The in vivo therapeutic treatment with HCE increased the survival and decreased the parasitaemia in the infected animals. Therefore, the HCE treatment exhibited a significant antiplasmodial effect and may be considered as a potential candidate for the development of new antimalarial drugs.
... These findings are consistent with previous studies conducted in Ghana [5] and India [41] and in the ECM model [11] and confirms the observation linking elevated CXCL10 in CM patients with poor prognosis [5,41]. It has been suggested that the release of malaria antigens after schizont rupture activates TNF-α which may activate production of CXCL10 in brain capillaries and astrocytes [18,37]. High levels of CXCL10 may cause vascular injury resulting in breakdown in the BBB which may lead to accumulation of leukocytes that induce local hyper-inflammation [41]. ...
Plasmodium falciparum in a subset of patients can lead to a diffuse encephalopathy known as cerebral malaria (CM). Despite treatment, mortality caused by CM can be as high as 30% while 10% of survivors of the disease may experience short- and long-term neurological complications. The pathogenesis of CM involves alterations in cytokine and chemokine expression, local inflammation, vascular injury and repair processes. These diverse factors have limited the rate of discovery of prognostic predictors of fatal CM. Identification of reliable early predictors of CM severity will enable clinicians to adjust this risk with appropriate management of CM. Recent studies revealed that elevated levels of CXCL10 expression in cerebrospinal fluid and peripheral blood plasma independently predicted severe and fatal CM. CXCR3, a promiscuous receptor of CXCL10, plays an important role in pathogenesis of mouse model of CM. In this study the role of corresponding CXCR3 ligands (CXCL11, CXCL10, CXCL9 & CXCL4) in fatal or severe CM was evaluated by comparing their levels in 16 healthy control (HC), 26 mild malaria (MM), 26 cerebral malaria survivors (CMS) and 12 non-survivors (CMNS) using enzyme linked immunosorbent assay (ELISA). Levels of CXCL4 and CXCL10 were significantly elevated in CMNS patients ( p < 0.05) when compared with HC, MM and CMS. Elevated plasma levels of CXCL10 and CXCL4 were tightly associated with CM mortality. Receiver Operating Characteristic (ROC) curve analysis revealed that CXCL4 and CXCL10 can discriminate CMNS from MM ( p < 0.0001) and CMS ( p < 0.0001) with an area under the curve (AUC) = 1. These results suggest that CXCL4 and CXCL10 play a prominent role in pathogenesis of CM associated death and may be used as functional or surrogate biomarkers for predicting CM severity.
... MCP-1/CCL2 and macrophage inflammatory protein-1α (MIP-1α/CCL3)] and CXCchemokines [e.g. PF4/CXCL4, monokine induced by gammainterferon (MIG/CXCL9), IP-10/CXCL10 and interferon-inducible T-cell alpha chemoattractant (I-TAC/CXCL11)] recruit more leukocytes to the brain, including activated CD4 + and CD8 + T cells (Hanum, Hayano and Kojima 2003;Campanella et al. 2008;Miu et al. 2008;Van den Steen et al. 2008). The importance of IFNγ in murine CM is further illustrated by the fact that depletion or deficiency of IFN-γ or the IFN-γ receptor (IFN-γ R) protects mice from CM (Grau et al. 1989;Yanez et al. 1996;Sanni et al. 1998, Amani et al. 2000Hansen et al. 2004;Parekh et al. 2006;Van den Steen et al. 2008) and IFN-γ R expression is only upregulated in brains of mice with CM (Rae et al. 2004). ...
Coevolution of humans and malaria parasites has generated an intricate balance between the immune system of the host and virulence factors of the parasite, equilibrating maximal parasite transmission with limited host damage. Focusing on the blood stage of the disease, we discuss how the balance between anti-parasite immunity versus immunomodulatory and evasion mechanisms of the parasite may result in parasite clearance or chronic infection without major symptoms, whereas imbalances characterized by excessive parasite growth, exaggerated immune reactions or a combination of both cause severe pathology and death, which is detrimental for both parasite and host. A thorough understanding of the immunological balance of malaria and its relation to other physiological balances in the body is of crucial importance for developing effective interventions to reduce malaria-related morbidity and to diminish fatal outcomes due to severe complications. Therefore, we discuss in this review the detailed mechanisms of anti-malarial immunity, parasite virulence factors including immune evasion mechanisms and pathogenesis. Furthermore, we propose a comprehensive classification of malaria complications according to the different types of imbalances.
... (RANTES) expression, the latter of which is specifically associated with ECM [193]. ...
Cerebral malaria is caused by a complicated series of immune reactions in the host, marked by inflammatory immune responses, margination of leukocytes and parasitized erythrocytes in cerebral vessels leading to breakdown of the blood-brain-barrier. Studies of the immune responses that lead to human cerebral malaria are limited since patients typically present once symptoms have commenced. Along with ethical considerations, this has led to the
immunopathogenesis of cerebral malaria being studied in the rodent model. Such studies have generally overlooked the very early stage of infection, during which the malaria parasite invades the liver, despite some evidence that early immune responses and intrahepatic attenuated
infections, such as caused by the RTS, S vaccine, play a role in preventing cerebral pathology.
This thesis describes the development of a model that attenuates infection at a very early stage prior to the onset of blood infection by the subtherapeutic administration of isopentaquine, an 8-aminoquinoline. Such chemical attenuation of the parasite at the very early, clinically silent liver stage suppresses parasite development, delays the time until parasites establish blood-stage infection and provokes an altered host immune response, altering immunopathogenesis and protecting from cerebral disease. This early response is a pro-inflammatory, cell-mediated one with increased T-cell activation in liver and spleen, elevated numbers of effector T cells, cytokine-secreting T cells and proliferating, multifunctional T cells producing pro-inflammatory cytokines. The response destabilizes the usual series of events that leads to cerebral pathology,
by downregulating inflammatory responses and T-cell activation at late infection. Dendritic cell numbers, T-cell activation and infiltration of CD8+ T cells to the brain are decreased in later infection, mediated by the anti-inflammatory cytokine IL-10.
These data indicate that liver-stage-directed early immune responses can moderate the overall downstream host immune response and modulate severe malaria outcome. Strikingly, CD8+ T cells isolated from the spleen as early as day 2 post infection are responsible for protection. Protection can be transferred to naïve animals by adoptive transfer of lymphocytes from the spleen at very early infection, but not when CD8+ T cells are depleted.
The reliance of this phenotype on CD8+ T cells and the transferability of protection are of particular interest, especially since these cells are isolated so early on in infection. Neither attenuated infections or early T cell responses have been studied in relation to cerebral pathology before and this is the first evidence that they can influence the course of the downstream systemic immune response and alter cerebral pathology. This draws parallels with the RTS, S vaccine, which is designed to elicit strong CD8+ T cell responses against the parasite in the liver,
and produces similar protection exclusively against severe malaria, including cerebral malaria.
This work has larger implications in dissecting the complex sequence of inter-related events that form the immunological basis of human cerebral (malaria) pathology and uncovers a relationship in both localization and timing of anti-parasitic T-cell responses involved in the
immunopathogenesis of cerebral malaria, presenting an insight into the potential role of the preerythrocytic response in tempering downstream cerebral immunopathogenesis. These data support the notion that Th1 cellular responses represent a kill or cure response to Plasmodium that must be tightly controlled in both a spatially and temporally specific manner.
... Visto que a resposta inflamatória desencadeada pelo quadro de MC não apresenta-se ativada no tecido retiniano, procuramos caracterizar se possíveis alterações neuroquímicas poderiam ser desencadeadas neste tecido de forma independente da cascata inflamatória. (Hanum et al., 2003;Patel et al., 2008;Randall et al., 2008). (Pow, 2001a;Kolb et al., 2001). ...
... [3][4][5][6] Reduced cerebral blood flow from sequestered infected erythrocytes in post capillary venules has been proposed as the root cause of its pathogenesis, 4-6 but the exact subsequent mechanism of injury remains unknown. [6][7][8][9][10][11] Since limited research has been done on human cerebral malaria (HCM), with most of the studies based upon postmortem examinations, 12 there has been interest in mice models of the disease, both for investigating the pathophysiology, as well as for the development and monitoring of new treatments. An ideal mice model for understanding this complex menace in humans has yet not been possible. ...
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.
... Brain histology and mRNA measurements of cytokine and chemokine related genes suggested that nSSL-BMS alleviates the immunopathological process that induces ECM [6]. While cytokines and chemokines may reach the brain through the damaged blood brain barrier that accompanies ECM [16], local production of cytokines and chemokines in CM has been emphasized as the important triggering element [17][18][19][20]. The examined samples were taken after thorough blood perfusion, indicating that the results most likely reflect the activity of molecules that either were produced in the brain or were produced elsewhere but were bound to local receptors. ...
Cerebral malaria (CM) is a severe complication of and a leading cause of death due to
Plasmodium falciparum
infection. CM is likely the result of interrelated events, including mechanical obstruction due to parasite sequestration in the microvasculature, and upregulation of Th1 immune responses. In parallel, blood-brain-barrier (BBB) breakdown and damage or death of microglia, astrocytes, and neurons occurs. We found that a novel formulation of a liposome-encapsulated glucocorticosteroid,
β
-methasone hemisuccinate (nSSL-BMS), prevents experimental cerebral malaria (ECM) in a murine model and creates a survival time-window, enabling administration of an antiplasmodial drug before severe anemia develops. nSSL-BMS treatment leads to lower levels of cerebral inflammation, expressed by altered levels of corresponding cytokines and chemokines. The results indicate the role of integrated immune responses in ECM induction and show that the new steroidal nanodrug nSSL-BMS reverses the balance between the Th1 and Th2 responses in malaria-infected mice so that the proinflammatory processes leading to ECM are prevented. Overall, because of the immunopathological nature of CM, combined immunomodulator/antiplasmodial treatment should be considered for prevention/treatment of human CM and long-term cognitive damage.
... Our findings reveal that the patterns of inflammatory, cellular and behavioral changes that arise with mild malaria are distinct in nature and magnitude from those observed with cerebral malaria. Although proinflammatory cytokine expression increases in the brain during mild malaria, the degree and type of inflammatory response differs, with the changes thought to be indicative of benign hypermetabolism rather than cytopathic effects (Rae et al., 2004;Hanum, 2003). Further, differences also include the absence of any histopathological and volumetric changes in the brain, in particular within the hippocampus in the mild malaria model. ...
Cerebral malaria is associated with cerebrovascular damage and neurological sequelae. However, the neurological consequences of uncomplicated malaria, the most prevalent form of the disease, remain uninvestigated. Here, using a mild malaria model, we show that a single Plasmodium chabaudi adami infection in adult mice induces neuroinflammation, neurogenic, and behavioral changes in the absence of a blood-brain barrier breach. Using cytokine arrays we show that the infection induces differential serum and brain cytokine profiles, both at peak parasitemia and 15 days post-parasite clearance. At the peak of infection, along with the serum, the brain also exhibited a definitive pro-inflammatory cytokine profile, and gene expression analysis revealed that pro-inflammatory cytokines were also produced locally in the hippocampus, an adult neurogenic niche. Hippocampal microglia numbers were enhanced, and we noted a shift to an activated profile at this time point, accompanied by a striking redistribution of the microglia to the subgranular zone adjacent to hippocampal neuronal progenitors. In the hippocampus, a distinct decline in progenitor turnover and survival was observed at peak parasitemia, accompanied by a shift from neuronal to glial fate specification. Studies in transgenic Nestin-GFP reporter mice demonstrated a decline in the Nestin-GFP(+)/GFAP(+) quiescent neural stem cell pool at peak parasitemia. Although these cellular changes reverted to normal 15 days post-parasite clearance, specific brain cytokines continued to exhibit dysregulation. Behavioral analysis revealed selective deficits in social and anxiety-like behaviors, with no change observed in locomotor, cognitive, and depression-like behaviors, with a return to baseline at recovery. Collectively, these findings indicate that even a single episode of mild malaria results in alterations of the brain cytokine profile, causes specific behavioral dysfunction, is accompanied by hippocampal microglial activation and redistribution, and a definitive, but transient, suppression of adult hippocampal neurogenesis.
... Syarifah et al. [66] studying mice susceptible and resistant to cerebral malaria infected with Plasmodium berghei, observed that the expression of cytokines (except for IL-4 and RANTES) as well as the expression of NO tested on mice spleen cells was enhanced in cells of resistant animals when compared to cells of susceptible animals. It is important to emphasize the high production of TNF-α in resistant mice, suggesting that activation of macrophages is significantly higher in these animals. ...
Several studies have evaluated the oxidant and antioxidant status of thalassemia patients but most focused mainly on the severe and intermediate states of the disease. Moreover, the oxidative status has not been evaluated for the different beta-thalassemia mutations.
To evaluate lipid peroxidation and Trolox equivalent antioxidant capacity in relation to serum iron and ferritin in beta thalassemia resulting from two different mutations (CD39 and IVS-I-110) compared to individuals without beta-thalassemia.
One hundred and thirty subjects were studied, including 49 who were heterozygous for beta-thalassemia and 81 controls. Blood samples were subjected to screening tests for hemoglobin. Allele-specific polymerase chain reaction was used to confirm mutations for beta-thalassemia, an analysis of thiobarbituric acid reactive species was used to determine lipid peroxidation, and Trolox equivalent antioxidant capacity evaluations were performed. The heterozygous beta-thalassemia group was also evaluated for serum iron and ferritin status.
Thiobarbituric acid reactive species (486.24 ± 119.64 ng/mL) and Trolox equivalent antioxidant capacity values (2.23 ± 0.11 mM/L) were higher in beta-thalassemia heterozygotes compared to controls (260.86 ± 92.40 ng/mL and 2.12 ± 0.10 mM/L, respectively; p-value < 0.01). Increased thiobarbituric acid reactive species values were observed in subjects with the CD39 mutation compared with those with the IVS-I-110 mutation (529.94 ± 115.60 ng/mL and 453.39 ± 121.10 ng/mL, respectively; p-value = 0.04). However, average Trolox equivalent antioxidant capacity values were similar for both mutations (2.20 ± 0.08 mM/L and 2.23 ± 0.12 mM/L, respectively; p-value = 0.39). There was no influence of serum iron and ferritin levels on thiobarbituric acid reactive species and Trolox equivalent antioxidant capacity values.
This study shows an increase of oxidative stress and antioxidant capacity in beta-thalassemia heterozygotes, mainly in carriers of the CD39 mutation.
... CCL5, CCR1, CCR3 and CCR5 mRNA expression was also detected in brains of Swiss Webster mice and appeared to contribute to the inflammatory response that results in cellular degradation in the cerebellum during Plasmodium yoelii (17XL) infection (Sarfo et al. 2005). Further chemokine gene expression studies in brains of ECMsusceptible mice confirmed that CXCL10, CXCL9 and CCL5 and to lesser extent CCL2, CCL7, CCL3, CCL4 and CXCL2 are upregulated during infection with P. berghei ANKA (Hanum et al. 2003;Campanella et al. 2008;Miu et al. 2008; Van den Steen et al. 2008). Interestingly, the expression of CCL2, CCL5, CCL4, CXCL9 and CXCL10 is induced by either IFN-γ or TNF, which is consistent with the important role of these pro-inflammatory cytokines in ECM pathogenesis. ...
SUMMARY Plasmodium falciparum malaria is responsible for over 250 million clinical cases every year worldwide. Severe malaria cases might present with a range of disease syndromes including acute respiratory distress, metabolic acidosis, hypoglycaemia, renal failure, anaemia, pulmonary oedema, cerebral malaria (CM) and placental malaria (PM) in pregnant women. Two main determinants of severe malaria have been identified: sequestration of parasitized red blood cells and strong pro-inflammatory responses. Increasing evidence from human studies and malaria infection animal models revealed the presence of host leucocytes at the site of parasite sequestration in brain blood vessels as well as placental tissue in complicated malaria cases. These observations suggested that apart from secreting cytokines, leucocytes might also contribute to disease by migrating to the site of parasite sequestration thereby exacerbating organ-specific inflammation. This evidence attracted substantial interest in identifying trafficking pathways by which inflammatory leucocytes are recruited to target organs during severe malaria syndromes. Chemo-attractant cytokines or chemokines are the key regulators of leucocyte trafficking and their potential contribution to disease has recently received considerable attention. This review summarizes the main findings to date, investigating the role of chemokines in severe malaria and the implication of these responses for the induction of pathogenesis and immunity to infection.
... This implies that in addition to its moderate inhibitory effect on heme metabolism in the food vacuole, other targets may exist within the parasite through which EA elicits parasiticidal activity, which may include inhibition of parasitic LDH. Inflammation in malaria infection is an immunological response attributable to inducible pro-inflammatory cytokines, chemokines, leukocytes, and macrophages [26] . Although these mediators play a role in protective immunity against malaria, an exacerbated response has been correlated with severity in disease pathogenesis including cerebral malaria, cytoadherence, and tissue cell damage [27] . ...
Background:
Entada africana (EA) is a medicinal plant used in West Africa for the treatment of malaria fever, but its efficacy against malaria is yet to be scientifically validated. Our study explores the antimalarial potential of the ethanol leaf extract of EA.
Methods:
The antiplasmodial activity of EA against chloroquine-sensitive (HB3) and chloroquine-resistant (FcM29) Plasmodium falciparum was determined as well as its peripheral antinociceptive and anti-inflammatory properties. The effect of the extract on human monocytic (THP-1) cells was recorded as a measure of cytotoxicity, whereas the inhibitory effect on heme detoxification was evaluated as a possible mechanism of antiplasmodial activity.
Results:
At a concentration of 100 μg/mL, EA was noncytotoxic and displayed moderate antiplasmodial activity against HB3 and FcM29 (IC50=26.36 and 28.86 μg/mL, respectively). It also exhibited concentration-dependent inhibition of synthetic heme (IC50=16 mg/mL). The extract (200 mg/kg body weight) showed significant (p<0.05) inhibition of paw inflammation, and significantly (p<0.01, 0.05) reduced the number of abdominal writhes induced by acetic acid (58.62%-65.51%), which was higher compared to that of diclofenac (50%, p<0.05).
Conclusions:
These findings suggest that peripheral antinociceptive effects and parasiticidal activity of EA contribute to its antimalarial properties and it can be further explored as effective therapy against malaria infection.
... To confirm that our findings were robust, we repeated survival studies in 8 additional independent experiments (totaling n 79 to 90 mice per group), and in each experiment, significantly improved survival was observed in C5aR / mice compared to C5L2 / and WT mice (log rank test for the combined results, P 0.0001) (data not shown).7, 9, 37, 38). Mice susceptible to P. berghei ANKA develop a marked systemic proinflammatory response during infection (7, 37, 39). ...
The host immune response plays an important role in the onset and progression of cerebral malaria (CM). The complement system
is an essential component of the innate immune response to malaria, and its activation generates the anaphylatoxin C5a. To
test the hypothesis that C5a signaling contributes to the pathogenesis of CM, we investigated a causal role for the C5a receptors
C5aR and C5L2 in a mouse model of experimental CM (ECM) induced by Plasmodium berghei ANKA infection, and using a case-control design, we examined levels of C5a in plasma samples from Ugandan children presenting
with CM or uncomplicated malaria (UM). In the ECM model, C5aR−/− mice displayed significantly improved survival compared to their wild-type (WT) counterparts (P = 0.004), whereas C5L2−/− mice showed no difference in survival from WT mice. Improved survival in C5aR−/− mice was associated with reduced levels of the proinflammatory cytokines tumor necrosis factor (TNF) and gamma interferon
(IFN-γ) and the chemokine, monocyte chemoattractant protein 1 (MCP-1) (CCL2). Furthermore, endothelial integrity was enhanced,
as demonstrated by increased levels of angiopoietin-1, decreased levels of angiopoietin-2 and soluble ICAM-1, and decreased
Evans blue extravasation into brain parenchyma. In the case-control study, the median levels of C5a at presentation were significantly
higher in children with CM versus those in children with UM (43.7 versus 22.4 ng/ml; P < 0.001). These findings demonstrate that C5a is dysregulated in human CM and contributes to the pathogenesis of ECM via
C5aR-dependent inflammation and endothelial dysfunction.
... MCP-1 has been shown to play an important role in several neuroinflammatory diseases (57). However, in a study of 481 Thai patients with malaria, MCP-1 gene polymorphisms were not associated with CM (58) and in the murine model of ECM, MCP-1 expression in the brain did not differ between susceptible versus resistant strains of mice (59). Although MCP-1 is well recognized for its ability to attract monocytes, it is also essential for Th2 polarization; MCP-1-deficient mice are unable to mount Th2 responses (60). ...
The pathogenesis of experimental cerebral malaria (ECM) is an immunologic process, mediated in part by Th1 CD4(+) T cells. However, the role of the Th1 CD4(+) T cell differentiation program on the ability to control parasitemia and susceptibility to ECM disease during blood stage malaria has never been assessed directly. Using the Plasmodium berghei ANKA murine model of ECM and mice deficient for the transcription factor T-bet (the master regulator of Th1 cells) on the susceptible C57BL/6 background, we demonstrate that although T-bet plays a role in the regulation of parasite burden, it also promotes the pathogenesis of ECM. T-bet-deficient (Tbx21(-/-)) mice had higher parasitemia than wild type controls did during the ECM phase of disease (17.7 ± 3.1% versus 10.9 ± 1.5%). In addition, although 100% (10/10) of wild type mice developed ECM by day 9 after infection, only 30% (3/10) of Tbx21(-/-) mice succumbed to disease during the cerebral phase of infection. Resistance to ECM in Tbx21(-/-) mice was associated with diminished numbers of IFN-γ-producing CD4(+) T cells in the spleen and a lower accumulation of CD4(+) and CD8(+) T cells in the brain. An augmented Th2 immune response characterized by enhanced production of activated GATA-3(+) CD4(+) T cells and elevated levels of the eotaxin, MCP-1, and G-CSF cytokines was observed in the absence of T-bet. Our results suggest that in virulent malarias, immune modulation or therapy resulting in an early shift toward a Th2 response may help to ameliorate the most severe consequences of malaria immunopathogenesis and the prospect of host survival.
... In the present model of CM, the immune response was considered to be a sepsis-like response, prompting consideration of the biomarkers that could be detected in the blood. Moreover, the present analysis was conducted on serum and not on plasma or brain tissue [53,54]. Further experimentation should be carried out to confirm our hypothesis, such as examination of the biomarkers detected in the brain. ...
The medical care of malaria is a clinical emergency because it may develop into severe malaria, which has a high risk of complications and death. One of the major complications of Plasmodium falciparum infections is cerebral malaria (CM), which is responsible for at least 175,000 deaths worldwide each year and has long-term neurological sequelae. Moreover, treatment for CM is only partially effective. Statins are now known to have anti-inflammatory action, to attenuate sepsis and to have neuroprotective effects. In vitro, atorvastatin (AVA) has an anti-malarial activity and has improved the activity of quinine (QN), mefloquine (MQ), and dihydroartemisinin (DHA).Objectives: This study had two objectives. First, the ability of AVA to enhance DHA efficacy by improving the survival rate for CM and also decreasing signs of CM was evaluated in a murine model of experimental cerebral malaria (ECM), which was designed in C57BL6/N mice. Second, the inflammatory biomarkers were assessed at D6 and D10 in mice treated by DHA and in untreated mice in which clinical signs of CM appear rapidly and death occurs before D12. Both experiments were designed with seven days of treatment with 40 mg/kg AVA combined with five days of 3 mg/kg DHA administered intraperitoneally.
AVA in combination with DHA in a therapeutic scheme leads to a significant delay in mouse death, and it has an effect on the onset of CM symptoms and on the level of parasitaemia. Evaluation of the biomarkers highlights the significant difference between treated and control mice for five cytokines and chemokines (Eotaxin-CCL11, IL-13, LIX-CXCL5, MIP1b-CCL4 and MIP2) that are known to have a role in chemotaxis.
The combination of DHA and AVA seems to be effective as a therapeutic scheme for improving mouse survival but less effective for cytokine modulation, which is associated with protection against CM. These results call for clinical trials of AVA as an adjuvant with anti-malarial therapy, especially with artemisinin-based combination therapy, in CM treatment or prevention.
... Recently, IL- 10 producing regulatory CD19(+) B cells has been intensively studied in abrogating immune-pathologies171819 and modulatory IL-10 has been beneficial for prevention of auto-immune diseases20212223. In mouse model, it is known that C57BL/6 mice are susceptible to ECM induced by virulent Plasmodium berghei ANKA (PbA) [14,24] and usually die from typical neurological symptoms between days 6–10 after infection25262728. Approximately, 95% to 100% of those mice exhibited the symptoms of ECM such as coma, convulsion, paralysis and hemiplegia, and died within 14 days of infection293031 . ...
In African endemic area, adults are less vulnerable to cerebral malaria than children probably because of acquired partial immunity or semi-immune status. Here, we developed an experimental cerebral malaria (ECM) model for semi-immune mice. C57BL/6 (B6) mice underwent one, two and three cycles of infection and radical treatment (1-cure, 2-cure and 3-cure, respectively) before being finally challenged with 104
Plasmodium berghei ANKA without treatment. Our results showed that 100% of naïve (0-cure), 67% of 1-cure, 37% of 2-cure and none of 3-cure mice succumbed to ECM within 10 days post challenge infection. In the protected 3-cure mice, significantly higher levels of plasma IL-10 and lower levels of IFN-γ than the others on day 7 post challenge infection were observed. Major increased lymphocyte subset of IL-10 positive cells in 3-cure mice was CD5(−)CD19(+) B cells. Passive transfer of splenic CD19(+) cells from 3-cure mice protected naïve mice from ECM. Additionally, aged 3-cure mice were also protected from ECM 12 and 20 months after the last challenge infection. In conclusion, mice became completely resistant to ECM after three exposures to malaria. CD19(+) B cells are determinants in protective mechanism of semi-immune mice against ECM possibly via modulatory IL-10 for pathogenic IFN-γ production.
... Similarly, increased levels of iNOS in human monocytes are not associated with the worsening of malaria in patients infected with P. falciparum [65]. Syarifah et al. [66] studying mice susceptible and resistant to cerebral malaria infected with Plasmodium berghei, observed that the expression of cytokines (except for IL-4 and RANTES) as well as the expression of NO tested on mice spleen cells was enhanced in cells of resistant animals when compared to cells of susceptible animals. It is important to emphasize the high production of TNF-α in resistant mice, suggesting that activation of macrophages is significantly higher in these animals. ...
Malaria is a significant public health problem in more than 100 countries and causes an estimated 200 million new infections every year. Despite the significant effort to eradicate this dangerous disease, lack of complete knowledge of its physiopathology compromises the success in this enterprise. In this paper we review oxidative stress mechanisms involved in the disease and discuss the potential benefits of antioxidant supplementation as an adjuvant antimalarial strategy.
The Cytokine-inducible Src homology 2 domain-containing (CISH) protein is a negative feedback regulator induced by cytokines that play key roles in immunity and erythropoiesis. Single nucleotide polymorphisms (SNPs) in the human CISH gene have been associated with increased susceptibility to severe malaria disease. To directly assess how CISH might influence outcomes in the BALB/c model of malaria anemia, CISH knockout (Cish−/−) mice on this background were infected with Plasmodium berghei and their hematopoietic responses, cytokine production and ability to succumb to severe malaria disease evaluated. Despite basal erythrocytic disruption, upon P. berghei infection, the Cish −/− mice were better able to maintain peripheral blood cell counts, hemoglobin levels and a steady-state pattern of erythroid differentiation compared to wild-type (Cish+/+) mice. Ablation of CISH, however, did not influence the outcome of acute malaria infections in either the BALB/c model or the alternative C57BL/6 model of experimental cerebral malaria, with the kinetics of infection, parasite load, weight loss and cytokine responses being similar between Cish+/+ and Cish−/− mice, and both genotypes succumbed to experimental cerebral malaria within a comparable timeframe.
Newly emerging data suggest that several neutrophil defense mechanisms may play a role in both aggravating and protecting against malaria. These exciting findings suggest that the balance of these cells in the host body may have an impact on the pathogenesis of malaria. To fully understand the role of neutrophils in severe forms of malaria, such as cerebral malaria (CM), it is critical to gain a comprehensive understanding of their behavior and functions. This study investigated the dynamics of neutrophil and T cell responses in C57BL/6 and BALB/c mice infected with Plasmodium berghei ANKA, murine models of experimental cerebral malaria (ECM) and non-cerebral experimental malaria, respectively. The results demonstrated an increase in neutrophil percentage and neutrophil-T cell ratios in the spleen and blood before the development of clinical signs of ECM, which is a phenomenon not observed in the non-susceptible model of cerebral malaria. Furthermore, despite the development of distinct forms of malaria in the two strains of infected animals, parasitemia levels showed equivalent increases throughout the infection period evaluated. These findings suggest that the neutrophil percentage and neutrophil-T cell ratios may be valuable predictive tools for assessing the dynamics and composition of immune responses involved in the determinism of ECM development, thus contributing to the advancing of our understanding of its pathogenesis.
Cerebral malaria (CM), the deadliest complication of Plasmodium infection, is a complex and unpredictable disease. However, our understanding of the host and parasite factors that cause CM is limited. Using a mouse model of CM, experimental CM (ECM), we performed a three-way comparison between ECM-susceptible C57BL/6 mice infected with ECM-causing Plasmodium ANKA parasites [ANKA(C57BL/6)], ECM-resistant BALB/c mice infected with Plasmodium ANKA [ANKA(BALB/c)], and C57BL/6 mice infected with Plasmodium NK65 that does not cause ECM [NK65(C57BL/6)]. All ANKA(C57BL/6) mice developed CM. In contrast, in ANKA(BALB/c) and NK65(C57BL/6), infections do not result in CM and proceed similarly in terms of parasite growth, disease course, and host immune response. However, parasite gene expression in ANKA(BALB/c) was remarkably different than that in ANKA(C57BL/6) but similar to the gene expression in NK65(C57BL/6). Thus, Plasmodium ANKA has an ECM-specific gene expression profile that is activated only in susceptible hosts, providing evidence that the host has a critical influence on the outcome of infection.
IMPORTANCE Hundreds of thousands of lives are lost each year due to the brain damage caused by malaria disease. The overwhelming majority of these deaths occur in young children living in sub-Saharan Africa. Thus far, there are no vaccines against this deadly disease, and we still do not know why fatal brain damage occurs in some children while others have milder, self-limiting disease progression. Our research provides an important clue to this problem. Here, we showed that the genetic background of the host has an important role in determining the course and the outcome of the disease. Our research also identified parasite molecules that can potentially be targeted in vaccination and therapy approaches.
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 12th 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.
Reticulon and the REEP family of proteins stabilize the high curvature of endoplasmic reticulum tubules. The REEP5 homolog in Plasmodium, Plasmodium berghei YOP1 (PbYOP1), plays an important role in the erythrocytic cycle of the P. berghei ANKA and the pathogenesis of experimental cerebral malaria (ECM), but the mechanisms are largely unknown. Here, we show that protection from ECM in Pbyop1Δ-infected mice is associated with reduced intracerebral Th1 accumulation, decreased expression of pro-inflammatory cytokines and chemokines, and attenuated pathologies in the brainstem, though the total number of CD4⁺ and CD8⁺ T cells sequestered in the brain are not reduced. Expression of adhesive molecules on brain endothelial cells, including ICAM-1, VCAM-1, and CD36, are decreased, particularly in the brainstem, where fatal pathology is always induced during ECM. Subsequently, CD8⁺ T cell-mediated cell apoptosis in the brain is compromised. These findings suggest that Pbyop1Δ parasites can be a useful tool for mechanistic investigation of cerebral malaria pathogenesis.
Plasmodium falciparum malaria causes half a million deaths per year, with up to 9% of this mortality caused by cerebral malaria (CM). One of the major processes contributing to the development of CM is an excess of host inflammatory cytokines. Recently K+ signaling has emerged as an important mediator of the inflammatory response to infection; we therefore investigated whether mice carrying an ENU induced activation of the electroneutral K+ channel KCC1 had an altered response to Plasmodium berghei . Here we show that Kcc1 M935K/M935K mice are protected from the development of experimental cerebral malaria, and that this protection is associated with an increased CD4+ T cells and TNF-α response. This is the first description of a K+ channel affecting the development of experimental cerebral malaria.
Oxidative stress is a major contributor of disease aetiology, progression and outcomes. Host systems and parasite infectivity play critical roles in the generation and manipulation of oxidative stress in malaria. Host systems involve the immunological and inflammatory responses that generate free radical species as host signalling processes as well as parasite combating and destructive entities. Parasites trigger molecules with inherent free radical generation in the host. Without the ability to synthesize amino acids, the parasite depends on the breakdown of haemoglobin to salvage the same within the food vacuole. This creates a highly oxidative stress environment from the Fenton reaction through the central ferrous moiety. Elimination of host oxidative stress process, from haemoglobin degradation product haeme, has critically evolved to protect parasites from the hostile intracellular compartment where it is an obligatory inhabitant. Parasites produce antioxidant species from both enzymatic and non-enzymatic molecules which cushions the parasites proteins from oxidation. The parasite also converts haeme, through biocrystallization, to haemozoin, a seemingly biologically inert molecule. In the presence of parasite DNA, haemozoin induces oxidative and inflammatory mediators (cytokines, chemokines, inducible nitric oxide synthase, nitric oxide, oxygen free radical, nitrogen free radicals, peroxynitrite etc.) with a high propensity toward oxidative stress able to override host antioxidant defence systems. Other parasite proponents, e.g. glycosylphosphotidylinositol, are instrumental in negatively modulating host oxidative stress. Without intervention, the disease machineries of oxidative stress go into a vicious cycle of self-propagation mode that leads to host debilitation, cachexia and death. Current drugs are mainly antiparasitic and relieve the “disease” aspect of malaria sparingly. Phytotherapeutics and phytochemicals (asiatic acid, maslinic acid, oleanolic acid), which display anti-oxidant and pro-oxidant properties, have shown both “antiparasite” and “anti-disease” effects promising efficacy in combating malaria. These pleiotropic properties are displayed in different environments with potential to buffer malarial disease syndrome.
In the oral cavity, reactive oxygen and nitrogen species are continuously generated by bacterial metabolism and host-mediated cellular factors. These reactive species facilitate a critical function that regulates the outcomes of both oral and systemic diseases, such as dental caries, periodontitis, and the maintenance of blood pressure. As a result, the protective effects of ROS and RNS are being explored for future therapeutic applications.
Malaria is a devastating infectious disease affecting mostly tropical and sub-tropical regions. Owning to the emergence of resistance to the existing chemotherapy, the development of anti-malarial drugs as novel chemotherapeutics remains unavoidable. Malaria parasite, Plasmodium, experiences oxidative stress throughout its life cycle upon infection, and underlying redox metabolism is quite complex. Alterations in the redox homeostasis occur during host-pathogen interactions. Parasite is highly vulnerable to such alterations in redox homeostasis. To circumvent this, the parasites engage in an efficient redox system having protective roles towards the turbulence faced by the parasite. Targeting the redox system of malaria parasite is tempting in developing novel antimalarial drugs. On the other hand, oxidative stress, generated during anti-malarial drug metabolism, acts as a source of inhibition against progression of this outrageous parasite. This review aims to provide updated knowledge on redox networks of parasite and structural insights of redox system enzymes, underpinning the balance between antioxidant and pro-oxidant candidates throughout the host-parasite interactions. Furthermore, it also highlights the importance of reactive oxygen species generation during anti-malarial drug metabolism. This review summarises on the vulnerabilities of the malaria parasite due to oxidative stress and the potential cues towards development of the novel antimalarial drugs.
Cerebral malaria (CM), defined as the presence of P. falciparum asexual stages on peripheral blood smear in a person with coma and no other cause for encephalopathy, is estimated to affect more than 800,000 people a year and has a 15–20 % mortality rate. CM predominantly affects children RANTES; release of free heme during hemolysis; endothelial activation leading to blood–brain barrier breakdown; CNS nitric oxide production; and genetic polymorphisms (e.g., sickle cell trait) that alter these responses or protect in other ways from severe disease. Murine models of cerebral malaria have provided new insights into the disease, but the difference in the parasite species and the host response has limited translation of findings from murine models into human CM studies. Nonhuman primate models are closer to human disease, but are limited by cost and ethical concerns. Therapies currently being studied for adjunctive therapy in CM include arginine (a donor of nitric oxide), inhaled nitric oxide, and recombinant erythropoietin. The potential benefits and harm of each therapy require close study, as many areas of CM pathogenesis remain unclear. Further studies are required, particularly in human disease, to better understand pathogenesis so that effective adjunctive therapy for this illness can be developed.
CD8+ T cells play a pathogenic role in the development of murine experimental cerebral malaria (ECM) induced by Plasmodium berghei ANKA (PbA) infection in C57BL/6 mice. Only a limited number of CD8+ epitopes have been described. Here, we report the identification of a new epitope from the bergheilysin protein recognized
by PbA-specific CD8+ T cells. Induction and functionality of these specific CD8+ T cells were investigated in parallel with previously reported epitopes, using new tools such as tetramers and reporter cell
lines that were developed for this study. We demonstrate that CD8+ T cells of diverse specificities induced during PbA infection share many characteristics. They express cytolytic markers
(gamma interferon [IFN-γ], granzyme B) and chemokine receptors (CXCR3, CCR5) and damage the blood-brain barrier in vivo. Our earlier finding that brain microvessels in mice infected with PbA, but not with non-ECM-causing strains, cross-presented
a shared epitope was generalizable to these additional epitopes. Suppressing the induction of specific CD8+ T cells through tolerization with a high-dose peptide injection was unable to confer protection against ECM, suggesting that
CD8+ T cells of other specificities participate in this process. The tools that we developed can be used to further investigate
the heterogeneity of CD8+ T cell responses that are involved in ECM.
The Malaria Immunology Database (MalarImDB, www.malarimdb.org) is a novel literature-based database of host mediators in blood-stage malaria. We designed this open-access online tool because intensive malaria research has resulted in a dazzling complexity of host mediators with pathogenic or protective functions. MalarImDB allows comparisons between expression levels in humans, expression levels in murine models, and functional data from experimental treatments in mice. The database is equipped with multiple search engines to retrieve information from many published studies. The search output is visualized schematically in tables, thereby revealing similarities and disparities. Thus, the primary aim of this database is to present a clear overview of the currently available data about malaria and to simplify literature searches.
Cerebral malaria (CM) is the major lethal complication of Plasmodium falciparum infection. It is characterized by persistent coma along with symmetrical motor signs. Several clinical, histopathological, and laboratory studies have suggested that cytoadherence of parasitized erythrocytes, neural injury by malarial toxin, and excessive inflammatory cytokine production are possible pathogenic mechanisms. Although the detailed pathophysiology of CM remains unsolved, it is thought that the binding of parasitized erythrocytes to the cerebral endothelia of microvessels, leading to their occlusion and the consequent angiogenic dysregulation play a key role in the disease pathogenesis. Recent evidences showed that vascular endothelial growth factor (VEGF) and its receptor-related molecules are over-expressed in the brain tissues of CM patients, as well as increased levels of VEGF are detectable in biologic samples from malaria patients. Whether the modulation of VEGF is causative agent of CM mortality or a specific phenotype of patients with susceptibility to fatal CM needs further evaluation. Currently, there is no biological test available to confirm the diagnosis of CM and its complications. It is hoped that development of biomarkers to identify patients and potential risk for adverse outcomes would greatly enhance better intervention and clinical management to improve the outcomes. We review and discuss here what it is currently known in regard to the role of VEGF in CM as well as VEGF as a potential biomarker.
In vitro experiments suggested that gamma interferon, CD8+ T cells, and anticircumsporozoite antibodies inhibited the exoerythrocytic stages of malaria parasites. To assess the role played in vivo by these factors, we conducted a prospective study in Madagascar. Forty individuals with a negative blood smear were followed for 8 weeks to detect the appearance of parasites in blood. Nineteen subjects remained negative for malaria, whereas 21 individuals became positive during follow-up. Among these, seven presented with blood parasites within the first 2 weeks and were excluded, as they probably were infected by sporozoites at enrollment. When measured at enrollment, antibodies to the synthetic peptide (NANP)5, lymphocyte proliferation with (NANP)5, and various lymphocytes subsets were similar among individuals that later presented with a Plasmodium falciparum blood infection or were not infected. Conversely, the level of gamma interferon in serum was higher in individuals that did not present with a P. falciparum infection during follow-up. These data suggest that gamma interferon may inhibit the malaria exoerythrocytic stages of development under in vivo conditions, as it does in vitro.
As liver can be an important target organ in malaria, we performed an ultrastructural study of hepatic alterations in the final stage of Plasmodium berghei infection in mice. Significant hepatocyte abnormalities were found. An elevated number of cells showed mitochondria with a high electron-dense matrix and multiple changes in shape and size, alterations in the structure of Golgi complex, swelling and disorganisation of both rough and smooth-surfaced endoplasmic reticulum, differently shaped peroxisome nucleoids, and disappearance of glycogen granules. In other areas the hepatocytes were significantly altered with diminished microvilli and exhibited myelin-like figures, autophagic vacuoles, abundant lipid droplets, and swollen mitochondria in their cytoplasm. Necrotic and atrophied hepatocytes with scarce microvilli in the Disse space and biliary canaliculi could be seen. Parasitised red blood cells and parasite debris were found inside degenerated hepatocytes. Alterations were also noticed in microvasculature, including thickened endothelial cells with swollen mitochondria, lysosomes and autophagic vacuoles in their cytoplasm. Our results demonstrate that hepatocyte damage is an important finding associated with the advanced stages of P. berghei malarial infection, which may lead to liver dysfunction in this disease.
Interferons and chemokines play a critical role in regulating the host response to viral infection. Measles virus, a member of the Paramyxoviridae family, induces RANTES expression by astrocytes. We have examined the mechanism of this induction in U373 cells derived from a human astrocytoma. RANTES was induced in a dose- and time-dependent manner by measles virus infection. Inhibition of receptor binding by the anti-CD46 antibody TRA-2.10 and of virus-membrane fusion by the tripeptide X-Phe-Phe-Gly reduced RANTES expression. Formalin-inactivated virus, which can bind but not fuse, and extensively UV-irradiated virus, which can bind and fuse, were both ineffective. Therefore, virus binding to the cellular receptor CD46 and subsequent membrane fusion were necessary, but not sufficient, to induce RANTES. UV irradiation of virus for less than 10 min proportionally inhibited viral transcription and RANTES expression. RANTES induction was decreased in infected cells treated with ribavirin, which inhibits measles virus transcription. However, RANTES mRNA was superinduced by measles virus in the presence of cycloheximide. These data suggest that partial transcription of the viral genome is sufficient and necessary for RANTES induction, whereas viral protein synthesis and replication are not required. This hypothesis was supported by the fact that RANTES was induced through transient expression of the measles virus nucleocapsid gene but not by measles genes encoding P or L proteins or by leader RNA in A549 cells. Thus, transcription of specific portions of measles virus RNA, such as the nucleocapsid gene, appears able to generate the specific signaling required to induce RANTES gene expression.
Heat-stable soluble products of rodent malarial parasites induce activated peritoneal macrophages to secrete tumour necrosis factor (TNF) in vitro. Since heat-stable parasite antigens are known to be present in the circulation of patients with malaria and it has been suggested that much of the pathology of malaria is due to TNF, we investigated the ability of such antigens to induce the production of TNF in vivo and to be toxic to mice. Injection of antigens obtained from Plasmodium yoelii or from P. berghei into mice which had previously received the macrophage-activating agent Propionibacterium acnes induced the release of TNF into the serum in amounts equivalent to the maximum release induced by bacterial lipopolysaccharide (LPS). Specific antiserum blocked the ability to the boiled soluble antigens, but not of LPS, to induce release of TNF. Similarly, vaccination specifically inhibited the release of TNF into the serum in response to subsequent stimulation with the antigens, but not with LPS. Mice made hypersensitive to the lethal action of TNF by pretreatment with D-galactosamine were killed in a dose-related fashion by administration of antigen preparations; addition of specific antiserum or prior vaccination with the antigens protected such mice, but not those given LPS, from death. We conclude that, in malaria, soluble antigens derived from the parasites may act like a toxin by stimulating the production of TNF, an important mediator of endotoxic shock, and that immunization with such antigens may diminish TNF secretion and consequently many of the clinical manifestations of the disease.
Mouse peritoneal macrophages incubated with erythrocytes infected with non-lethal or lethal variants of Plasmodium yoelii or with P. berghei, in the presence of polymyxin B to exclude the effects of any contaminating endotoxin, secreted a cytotoxic factor into the supernatant that was shown to be tumour necrosis factor (TNF). No differences were observed in the ability of the three types of parasite to induce TNF production, which was maximal in the range of 0.2-5 infected erythrocytes per macrophages. TNF production was equivalent to that induced by lipopolysaccharide (LPS) and was enhanced by pretreatment of the macrophages with interferon-gamma (IFN-gamma) or with indomethacin. Culture media containing parasite products also induced macrophages to secrete TNF. The activity withstood boiling and was inhibited by malaria-specific antisera. Since heat-stable antigens are present in the circulation of patients with malaria, they may induced the secretion of TNF, a mediator of endotoxic shock, which could contribute to the pathology of the disease.
Histological changes during the course of P. berghei infection were investigated in A/J, BALB/c, OF1, CBA and C57B1 mice. The findings were studied in relation to serological aspects (Contreras et al., 1980). High mortality and acute deaths occurred in A/J, BALB/c and OF1 mice and marked cerebral lesions were found in these strains from day 15, including congestion of meningeal and cerebral veins and capillaries, blocking of these vessels by heavily parasitized RBC, cerebral oedema and haemorrhages. Such lesions were minimal in CBA and C57B1 mice, and absent in mice examined 21 and 24 days after infection. Small deposits of IgG and traces of C3 were detected by immunofluorescence in the choroid plexus of most mice from day 9. Renal lesions included congestion, plugging of veins and capillaries, low-grade mononuclear infiltration and mesangial thickening; these changes were most marked in CBA, C57B1 and A/J mice. Glomerular deposits of IgM were present in all strains in the first week of infection. IgG and C3 were detected in the second week, but only traces were found in CBA mice. The livers showed congestion, accumulation of pigment in swollen Kupffer cells and mononuclear portal infiltration; these were most pronounced in A/J mice. In the spleen, there was a great increase in the reticuloendothelial cell population, white pulp proliferation, congestion and accumulation of pigment and plasma cell reaction; the pattern of white pulp expansion varied in the different strains. The results suggest that cerebral lesions play a significant role in the aetiology of acute deaths in this malaria model.
In this study we demonstrate that glycosylphosphatidylinositol (GPI) of malaria parasite origin directly increases cell adhesion molecule expression in purified HUVECs in a dose- and time-dependent manner, resulting in a marked increase in parasite and leukocyte cytoadherence to these target cells. The structurally related glycolipids dipalmitoyl-phosphatidylinositol and iM4 glycoinositolphospholipid of Leishmania mexicana had no such activity. Malarial GPI exerts this effect by activation of an endogenous GPI-based signal transduction pathway in endothelial cells. GPI induces rapid onset tyrosine phosphorylation of multiple intracellular substrates within 1 min of addition to cells in a dose-dependent manner. This activity can be blocked by the protein tyrosine kinase-specific antagonist herbimycin A, genistein, and tyrphostin. These tyrosine kinase antagonists also inhibit GPI-mediated up-regulation of adhesin expression and parasite cytoadherence. GPI-induced up-regulation of adhesin expression and parasite cytoadherence can also be blocked by the NFκB/c-rel antagonist pyrrolidine-dithiocarbamate, suggesting the involvement of this family of transcription factors in GPI-induced adhesin expression. The direct activation of endothelial cells by GPI does not require the participation of TNF or IL-1. However, GPI is also responsible for the indirect pathway of increased adhesin expression mediated by TNF and IL-1 output from monocytes/macrophages. Total parasite extracts also up-regulate adhesin expression and parasite cytoadherence in HUVECs, and this activity is blocked by a neutralizing mAb to malarial GPI, suggesting that GPI is the dominant agent of parasite origin responsible for this activity. Thus, a parasite-derived GPI toxin activates vascular endothelial cells by tyrosine kinase-mediated signal transduction, leading to NFκB/c-rel activation and downstream expression of adhesins, events that may play a central role in the etiology of cerebral malaria.
Little is known about the participation of β chemokines in inflammatory processes within the central nervous system. The release
of three of these peptides (macrophage inflammatory protein [MIP]-1α, MIP-1β, and monocyte chemoattractant protein-I) from
human fetal microglial cell and astrocyte cultures was assessed following stimulation by lipopolysaccharide, interleukin-1β,
and tumor necrosis factor-a. Although striking differences were found between these two types of glial cells in their responsiveness
to lipopolysaccharide and cytokines, both microglia and astrocytes produced all three β chemokines. Only microglial cells,
however, demonstrated an increased migratory response to the β chemokines. The results of this in vitro study suggest that
β chemokines may play an important role in the trafficking of mononuclear phagocytes within the brain.
There is growing evidence that T helper cell subsets (TH1 and TH2) can be differentially recruited to promote different types of inflammatory reactions. Murine TH1 but not TH2 cells are recruited through P- and E-selectin into inflamed tissues, where they induce delayed-type hypersensitivity reactions. The human eotaxin-receptor CCR3, originally described on eosinophils and basophils, was also found to be expressed by TH2 cells. An antibody to CCR3 was used to isolate T cells from peripheral blood that give rise to TH2-polarized cell lines and to identify TH2 cells derived from naïve T cells in vitro. Eotaxin stimulated increases in intracellular calcium and chemotaxis of CCR3(+) T cells. The attraction of TH2 cells by eotaxin could represent a key mechanism in allergic reactions, because it promotes the allergen-driven production of interleukin-4 and interleukin-5 necessary to activate basophils and eosinophils.
The ability of deproteinated malaria exoantigens from Plasmodium falciparum (Pf-MT) and P. berghei ANKA (PbA-MT) to activate murine haematopoietic cells was analysed in vitro. Malaria toxins (MT) of both plasmodium species induced cell proliferation and the production of IFN-gamma in overnight and long-term (5 days) spleen and bone marrow cultures and a reduction of the number of TNF-alpha spot forming cells (SFC). When added to cells of malaria-experienced animals, MT decreased the number of IL-4 SPC and increased the number of IL-5 SPC. However, the same proliferative and IFN-gamma induction properties as in naive cells were observed. Simultaneous addition of IL-2 and PbA-MT to spleen cells inhibited the proliferation but increased the IFN-gamma production usually induced by IL-2. Flow cytometric analysis revealed that the addition of MT triggered an expansion of CD3+ and GR1+ cell populations. Our results suggest that malaria toxins of different species can induce an immediate and strong proliferation and a TH1-type cytokine release by murine cells, independently of previous in vivo priming.
Murine cerebral malaria (CM) induced by Plasmodium berghei ANKA kills susceptible mice within 24 to 48 h of onset of symptoms and is characterized by the production of inflammatory cytokines in the brain. C57BL/6J mice are sensitive to lethal CM, while A/J mice are resistant. These strains of mice were immunized with an adjuvant vaccine of killed whole-blood-stage parasites. The immunization protected C57BL/6 mice from lethal CM following virulent challenge. The same immunization increased the incidence of lethal CM in A/J mice challenged similarly. Histopathologic examination of the brains of mice from these studies revealed two distinct types of lesions. Type I CM is acute in onset; usually lethal; and characterized by widespread microglial activation, endothelial cell damage, and microvascular disruption in the brain. Type II CM is characterized by intense, but focal, mononuclear cell inflammation without endothelial cell damage or microvascular destruction. Animals with type II lesions were clinically normal and protected from type I lesions. Available clinical, epidemiological, and biochemical evidence suggests that type I and type II lesions might exist in human CM as well.
A possible protective role of IL-18 in host defense against blood-stage murine malarial infection was studied in BALB/c mice using a nonlethal strain, Plasmodium yoelii 265, and a lethal strain, Plasmodium berghei ANKA. Infection induced an increase in mRNA expression of IL-18, IL-12p40, IFN-gamma, and TNF-alpha in the case of P. yoelii 265 and an increase of IL-18, IL-12p40, and IFN-gamma in the case of P. berghei ANKA. The timing of mRNA expression of IL-18 in both cases was consistent with a role in the induction of IFN-gamma protein expression. Histological examination of spleen and liver tissues from infected controls treated with PBS showed poor cellular inflammatory reaction, massive necrosis, a large number of infected parasitized RBCs, and severe deposition of hemozoin pigment. In contrast, IL-18-treated infected mice showed massive infiltration of inflammatory cells consisting of mononuclear cells and Kupffer cells, decreased necrosis, and decreased deposition of the pigment hemozoin. Treatment with rIL-18 increased serum IFN-gamma levels in mice infected with both parasites, delayed onset of parasitemia, conferred a protective effect, and thus increased survival rate of infected mice. Administration of neutralizing anti-IL-18 Ab exacerbated infection, impaired host resistance and shortened the mean survival of mice infected with P. berghei ANKA. Furthermore, IL-18 knockout mice were more susceptible to P. berghei ANKA than were wild-type C57BL/6 mice. These data suggest that IL-18 plays a protective role in host defense by enhancing IFN-gamma production during blood-stage infection by murine malaria.