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Grau GER, Craig AG. Cerebral malaria pathogenesis: revisiting parasite and host contributions. Future Microbiol 2012; 7:291-302. [DOI: 10.2217/fmb.11.155] [Citation(s) in RCA: 66] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023] Open
Abstract
Cerebral malaria is one of a number of clinical syndromes associated with infection by human malaria parasites of the genus Plasmodium. The etiology of cerebral malaria derives from sequestration of parasitized red cells in brain microvasculature and is thought to be enhanced by the proinflammatory status of the host and virulence characteristics of the infecting parasite variant. In this article we examine the range of factors thought to influence the development of Plasmodium falciparum cerebral malaria in humans and review the evidence to support their role.
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Affiliation(s)
- Georges Emile Raymond Grau
- Vascular Immunology Unit, Department of Pathology, Sydney Medical School, The University of Sydney, Camperdown NSW 2042, Australia
- La Jolla Infectious Disease Institute, San Diego, CA 92109, USA
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Higgins SJ, Kain KC, Liles WC. Immunopathogenesis of falciparum malaria: implications for adjunctive therapy in the management of severe and cerebral malaria. Expert Rev Anti Infect Ther 2012; 9:803-19. [PMID: 21905788 DOI: 10.1586/eri.11.96] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Despite optimal antimalarial treatment and advances in malaria eradication, the mortality rate associated with severe malaria due to Plasmodium falciparum infection, including cerebral malaria (CM), remains unacceptably high. This suggests that strategies directed solely at parasite eradication may be insufficient to prevent neurological complications and death in all cases of CM. Therefore, there is an urgent need to develop innovative adjunctive therapeutic strategies to effectively reduce CM-associated mortality. CM pathogenesis is believed to be due, in part, to an aberrant host immune response to P. falciparum, resulting in deleterious consequences, including vascular activation and dysfunction. Development of effective and affordable therapeutic strategies that act to modulate the underlying host-mediated immunopathology should be explored to improve outcome. In this article, we summarize immunomodulatory therapies that have been assessed in clinical trials to date, and highlight novel and promising treatment strategies currently being investigated to address this major global health challenge.
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Affiliation(s)
- Sarah J Higgins
- Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, ON, Canada
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Inhaled nitric oxide reduces endothelial activation and parasite accumulation in the brain, and enhances survival in experimental cerebral malaria. PLoS One 2011; 6:e27714. [PMID: 22110737 PMCID: PMC3218025 DOI: 10.1371/journal.pone.0027714] [Citation(s) in RCA: 57] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2011] [Accepted: 10/22/2011] [Indexed: 01/08/2023] Open
Abstract
The host immune response contributes to the onset and progression of severe malaria syndromes, such as cerebral malaria. Adjunctive immunomodulatory strategies for severe malaria may improve clinical outcome beyond that achievable with artemisinin-based therapy alone. Here, we report that prophylaxis with inhaled nitric oxide significantly reduced systemic inflammation (lower TNF, IFNγ and MCP-1 in peripheral blood) and endothelial activation (decreased sICAM-1 and vWF, and increased angiopoeitin-1 levels in peripheral blood) in an experimental cerebral malaria model. Mice that received inhaled nitric oxide starting prior to infection had reduced parasitized erythrocyte accumulation in the brain, decreased brain expression of ICAM-1, and preserved vascular integrity compared to control mice. Inhaled nitric oxide administered in combination with artesunate, starting as late as 5.5 days post-infection, improved survival over treatment with artesunate alone (70% survival in the artesunate only vs. 100% survival in the artesunate plus iNO group, p = 0.03). These data support the clinical investigation of inhaled nitric oxide as a novel adjunctive therapy in patients with severe malaria.
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55
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Villegas-Mendez A, de Souza JB, Murungi L, Hafalla JCR, Shaw TN, Greig R, Riley EM, Couper KN. Heterogeneous and tissue-specific regulation of effector T cell responses by IFN-gamma during Plasmodium berghei ANKA infection. THE JOURNAL OF IMMUNOLOGY 2011; 187:2885-97. [PMID: 21880980 DOI: 10.4049/jimmunol.1100241] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
IFN-γ and T cells are both required for the development of experimental cerebral malaria during Plasmodium berghei ANKA infection. Surprisingly, however, the role of IFN-γ in shaping the effector CD4(+) and CD8(+) T cell response during this infection has not been examined in detail. To address this, we have compared the effector T cell responses in wild-type and IFN-γ(-/-) mice during P. berghei ANKA infection. The expansion of splenic CD4(+) and CD8(+) T cells during P. berghei ANKA infection was unaffected by the absence of IFN-γ, but the contraction phase of the T cell response was significantly attenuated. Splenic T cell activation and effector function were essentially normal in IFN-γ(-/-) mice; however, the migration to, and accumulation of, effector CD4(+) and CD8(+) T cells in the lung, liver, and brain was altered in IFN-γ(-/-) mice. Interestingly, activation and accumulation of T cells in various nonlymphoid organs was differently affected by lack of IFN-γ, suggesting that IFN-γ influences T cell effector function to varying levels in different anatomical locations. Importantly, control of splenic T cell numbers during P. berghei ANKA infection depended on active IFN-γ-dependent environmental signals--leading to T cell apoptosis--rather than upon intrinsic alterations in T cell programming. To our knowledge, this is the first study to fully investigate the role of IFN-γ in modulating T cell function during P. berghei ANKA infection and reveals that IFN-γ is required for efficient contraction of the pool of activated T cells.
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Affiliation(s)
- Ana Villegas-Mendez
- Department of Immunology and Infection, Faculty of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, London WC1E 7HT, United Kingdom
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Zimmerman GA, Castro-Faria-Neto H. Persistent cognitive impairment after cerebral malaria: models, mechanisms and adjunctive therapies. Expert Rev Anti Infect Ther 2011; 8:1209-12. [PMID: 21073283 DOI: 10.1586/eri.10.117] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
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57
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Finney CA, Hawkes CA, Kain DC, Dhabangi A, Musoke C, Cserti-Gazdewich C, Oravecz T, Liles WC, Kain KC. S1P is associated with protection in human and experimental cerebral malaria. Mol Med 2011; 17:717-25. [PMID: 21556483 DOI: 10.2119/molmed.2010.00214] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2010] [Accepted: 05/04/2011] [Indexed: 11/06/2022] Open
Abstract
Cerebral malaria (CM) is associated with excessive inflammatory responses and endothelial activation. Sphingosine 1-phosphate (S1P) is a signaling sphingolipid implicated in regulating vascular integrity, inflammation and T-cell migration. We hypothesized that altered S1P signaling during malaria contributes to endothelial activation and inflammation, and show that plasma S1P levels were decreased in Ugandan children with CM compared with children with uncomplicated malaria. Using the Plasmodium berghei ANKA (PbA) model of experimental CM (ECM), we demonstrate that humanized S1P lyase (hS1PL)(-/-) mice with reduced S1P lyase activity (resulting in increased bio-available S1P) had improved survival compared with wild-type littermates. Prophylactic and therapeutic treatment of infected mice with compounds that modulate the S1P pathway and are in human trials for other conditions (FTY720 or LX2931) significantly improved survival in ECM. FTY720 treatment improved vascular integrity as indicated by reduced levels of soluble intercellular adhesion molecule (sICAM), increased angiopoietin 1 (Ang1) (regulator of endothelial quiescence) levels, and decreased Evans blue dye leakage into brain parenchyma. Furthermore, treatment with FTY720 decreased IFNγ levels in plasma as well as CD4(+) and CD8(+) T-cell infiltration into the brain. Finally, when administered during infection in combination with artesunate, FTY720 treatment resulted in increased survival to ECM. These findings implicate dysregulation of the S1P pathway in the pathogenesis of human and murine CM and suggest a novel therapeutic strategy to improve clinical outcome in severe malaria.
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Affiliation(s)
- Constance Am Finney
- SA Rotman Laboratories, McLaughlin-Rotman Centre for Global Health, University Health Network and University of Toronto, Canada Faculty of Medicine, University of Toronto, Canada
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Clemmer L, Martins YC, Zanini GM, Frangos JA, Carvalho LJM. Artemether and artesunate show the highest efficacies in rescuing mice with late-stage cerebral malaria and rapidly decrease leukocyte accumulation in the brain. Antimicrob Agents Chemother 2011; 55:1383-90. [PMID: 21220531 PMCID: PMC3067152 DOI: 10.1128/aac.01277-10] [Citation(s) in RCA: 51] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/18/2010] [Revised: 11/19/2010] [Accepted: 01/02/2011] [Indexed: 11/20/2022] Open
Abstract
The murine model of cerebral malaria (ECM) caused by Plasmodium berghei ANKA (PbA) infection in susceptible mice has been extensively used for studies of pathogenesis and identification of potential targets for human CM therapeutics. However, the model has been seldom explored to evaluate adjunctive therapies for this malaria complication. A first step toward this goal is to define a treatment protocol with an effective antimalarial drug able to rescue mice presenting late-stage ECM. We evaluated the efficacy of artemisinin, artemether, artesunate, and quinine given intraperitoneally once a day, and combinations with mefloquine, in suppressing PbA infection in mice with moderate parasitemia. Artemether, artesunate, and quinine were then evaluated for efficacy in rescuing PbA-infected mice with ECM, strictly defined by using objective criteria based on the presentation of clinical signs of neurological involvement, degree of hypothermia, and performance in a set of six motor behavior tests. Artemether at 25 mg/kg presented the fastest parasite killing ability in 24 h and fully avoided recrudescence in a 5-day treatment protocol. Artemether and artesunate were equally effective in rescuing mice with late-stage ECM (46 and 43% survival, respectively), whereas quinine had a poor performance (12.5% survival). Artemether caused a marked decrease in brain leukocyte accumulation 24 h after the first dose. In conclusion, artemether and artesunate are effective in rescuing mice with late-stage ECM and decrease brain inflammation. In addition, the described protocols for more strict clinical evaluation and for rescue treatment provide a framework for studies of CM adjunctive therapies using this mouse model.
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Affiliation(s)
- L. Clemmer
- La Jolla Bioengineering Institute, 3535 General Atomics Court, Suite 210, San Diego, California 92121, IPEC, Fiocruz, Rio de Janeiro, Brazil
| | - Y. C. Martins
- La Jolla Bioengineering Institute, 3535 General Atomics Court, Suite 210, San Diego, California 92121, IPEC, Fiocruz, Rio de Janeiro, Brazil
| | - G. M. Zanini
- La Jolla Bioengineering Institute, 3535 General Atomics Court, Suite 210, San Diego, California 92121, IPEC, Fiocruz, Rio de Janeiro, Brazil
| | - J. A. Frangos
- La Jolla Bioengineering Institute, 3535 General Atomics Court, Suite 210, San Diego, California 92121, IPEC, Fiocruz, Rio de Janeiro, Brazil
| | - L. J. M. Carvalho
- La Jolla Bioengineering Institute, 3535 General Atomics Court, Suite 210, San Diego, California 92121, IPEC, Fiocruz, Rio de Janeiro, Brazil
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Mimche PN, Taramelli D, Vivas L. The plant-based immunomodulator curcumin as a potential candidate for the development of an adjunctive therapy for cerebral malaria. Malar J 2011; 10 Suppl 1:S10. [PMID: 21411011 PMCID: PMC3059458 DOI: 10.1186/1475-2875-10-s1-s10] [Citation(s) in RCA: 45] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The clinical manifestations of cerebral malaria (CM) are well correlated with underlying major pathophysiological events occurring during an acute malaria infection, the most important of which, is the adherence of parasitized erythrocytes to endothelial cells ultimately leading to sequestration and obstruction of brain capillaries. The consequent reduction in blood flow, leads to cerebral hypoxia, localized inflammation and release of neurotoxic molecules and inflammatory cytokines by the endothelium. The pharmacological regulation of these immunopathological processes by immunomodulatory molecules may potentially benefit the management of this severe complication. Adjunctive therapy of CM patients with an appropriate immunomodulatory compound possessing even moderate anti-malarial activity with the capacity to down regulate excess production of proinflammatory cytokines and expression of adhesion molecules, could potentially reverse cytoadherence, improve survival and prevent neurological sequelae. Current major drug discovery programmes are mainly focused on novel parasite targets and mechanisms of action. However, the discovery of compounds targeting the host remains a largely unexplored but attractive area of drug discovery research for the treatment of CM. This review discusses the properties of the plant immune-modifier curcumin and its potential as an adjunctive therapy for the management of this complication.
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Affiliation(s)
- Patrice N Mimche
- Faculty of Infectious and Tropical Diseases, Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK.
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Langhorne J, Buffet P, Galinski M, Good M, Harty J, Leroy D, Mota MM, Pasini E, Renia L, Riley E, Stins M, Duffy P. The relevance of non-human primate and rodent malaria models for humans. Malar J 2011; 10:23. [PMID: 21288352 PMCID: PMC3041720 DOI: 10.1186/1475-2875-10-23] [Citation(s) in RCA: 99] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2010] [Accepted: 02/02/2011] [Indexed: 11/10/2022] Open
Abstract
At the 2010 Keystone Symposium on "Malaria: new approaches to understanding Host-Parasite interactions", an extra scientific session to discuss animal models in malaria research was convened at the request of participants. This was prompted by the concern of investigators that skepticism in the malaria community about the use and relevance of animal models, particularly rodent models of severe malaria, has impacted on funding decisions and publication of research using animal models. Several speakers took the opportunity to demonstrate the similarities between findings in rodent models and human severe disease, as well as points of difference. The variety of malaria presentations in the different experimental models parallels the wide diversity of human malaria disease and, therefore, might be viewed as a strength. Many of the key features of human malaria can be replicated in a variety of nonhuman primate models, which are very under-utilized. The importance of animal models in the discovery of new anti-malarial drugs was emphasized. The major conclusions of the session were that experimental and human studies should be more closely linked so that they inform each other, and that there should be wider access to relevant clinical material.
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Affiliation(s)
- Jean Langhorne
- Division of Parasitology, MRC National Institute for Medical Research, The Ridgeway, London NW7 1AA, UK.
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Longley R, Smith C, Fortin A, Berghout J, McMorran B, Burgio G, Foote S, Gros P. Host resistance to malaria: using mouse models to explore the host response. Mamm Genome 2010; 22:32-42. [DOI: 10.1007/s00335-010-9302-6] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2010] [Accepted: 11/03/2010] [Indexed: 11/24/2022]
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62
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Taylor-Robinson AW. Validity of Modelling Cerebral Malaria in Mice: Argument and Counter Argument. ACTA ACUST UNITED AC 2010. [DOI: 10.4303/jnp/n100601] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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