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Cumming BM, Goldring JPD. Monocyte phagocytosis of malaria β-haematin in the presence of artemisinin, amodiaquine, chloroquine, doxycycline, primaquine, pyrimethamine and quinine. Exp Parasitol 2018; 197:93-102. [PMID: 30562480 DOI: 10.1016/j.exppara.2018.12.002] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2018] [Revised: 11/07/2018] [Accepted: 12/14/2018] [Indexed: 12/14/2022]
Abstract
The intraerythrocytic malaria parasite digests haemoglobin to provide amino acids for metabolism and releases toxic haem that is sequestered into haemozoin, a non-toxic, insoluble, crystalline pigment. Following erythrocyte rupture, haemozoin is released into circulation and phagocytosed by monocytes. Phagocytosed haemozoin and antimalarial drugs have both been reported to modulate monocyte functions. This study determined the effects of therapeutic concentrations of seven antimalarial drugs; amodiaquine, artemisinin, chloroquine, doxycycline, primaquine, pyrimethamine and quinine, on the phagocytosis of β-haematin (synthetic haemozoin) by two monocytic cell lines, J774A.1 and U937, and human peripheral blood mononuclear cells. A novel spectrophotometric method based on the absorbance (O.D 400 nm) of alkali/SDS treated monocytes containing β-haematin was developed to complement counting phagocytosis with microscopy. The method has potential use for the large scale screening of monocyte phagocytic activity. Artemisinin, quinine, primaquine and pyrimethamine activated β-haematin phagocytosis by 12% or more, whereas amodiaquine, chloroquine and doxycyline inhibited β-haematin phagocytosis. In contrast, antimalarial drugs had minimal inhibitory effects on the phagocytosis of latex beads with only quinine resulting in more than 20% inhibition. Antimalarial drugs appear to alter monocyte phagocytic activity which has implications for the treatment, pathogenicity and adjunct therapies for malaria.
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Affiliation(s)
- Bridgette M Cumming
- Department of Biochemistry, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg Campus, Private Bag X01, Scottsville, 3209, South Africa
| | - J P Dean Goldring
- Department of Biochemistry, School of Life Sciences, University of KwaZulu-Natal, Pietermaritzburg Campus, Private Bag X01, Scottsville, 3209, South Africa.
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2
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Krause RGE, Goldring JPD. Phosphoethanolamine-N-methyltransferase is a potential biomarker for the diagnosis of P. knowlesi and P. falciparum malaria. PLoS One 2018; 13:e0193833. [PMID: 29505599 PMCID: PMC5837800 DOI: 10.1371/journal.pone.0193833] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/13/2017] [Accepted: 02/20/2018] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Plasmodium knowlesi is recognised as the main cause of human malaria in Southeast Asia. The disease is often misdiagnosed as P. falciparum or P. malariae infections by microscopy, and the disease is difficult to eliminate due to its presence in both humans and monkeys. P. knowlesi infections can rapidly cause severe disease and require prompt diagnosis and treatment. No protein biomarker exists for the rapid diagnostic test (RDT) detection of P. knowlesi infections. Plasmodium knowlesi infections can be diagnosed by PCR. METHODS AND PRINCIPAL FINDINGS Phosphoethanolamine-N-methyltransferase (PMT) is involved in malaria lipid biosynthesis and is not found in the human host. The P. falciparum, P. vivax and P. knowlesi PMT proteins were recombinantly expressed in BL21(DE3) Escherichia coli host cells, affinity purified and used to raise antibodies in chickens. Antibodies against each recombinant PMT protein all detected all three recombinant proteins and the native 29 kDa P. falciparum PMT protein on western blots and in ELISA. Antibodies against a PMT epitope (PLENNQYTDEGVKC) common to all three PMT orthologues detected all three proteins. Antibodies against unique peptides from each orthologue of PMT, PfCEVEHKYLHENKE, PvVYSIKEYNSLKDC, PkLYPTDEYNSLKDC detected only the parent protein in western blots and P. falciparum infected red blood cell lysates or blood lysates spiked with the respective proteins. Similar concentrations of PfPMT and the control, PfLDH, were detected in the same parasite lysate. The recombinant PfPMT protein was detected by a human anti-malaria antibody pool. CONCLUSION PMT, like the pan-specific LDH biomarker used in RDT tests, is both soluble, present at comparable concentrations in the parasite and constitutes a promising antimalarial drug target. PMT is absent from the human proteome. PMT has the potential as a biomarker for human malaria and in particular as the first P. knowlesi specific protein with diagnostic potential for the identification of a P. knowlesi infection.
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3
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Mustaffa KMF, Storm J, Whittaker M, Szestak T, Craig AG. In vitro inhibition and reversal of Plasmodium falciparum cytoadherence to endothelium by monoclonal antibodies to ICAM-1 and CD36. Malar J 2017; 16:279. [PMID: 28679447 PMCID: PMC5499065 DOI: 10.1186/s12936-017-1930-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2017] [Accepted: 07/01/2017] [Indexed: 12/04/2022] Open
Abstract
Background Sequestration of parasitized red blood cells from the peripheral circulation during an infection with Plasmodium falciparum is caused by an interaction between the parasite protein PfEMP1 and receptors on the surface of host endothelial cells, known as cytoadherence. Several lines of evidence point to a link between the pathology of severe malaria and cytoadherence, therefore blocking adhesion receptors involved in this process could be a good target to inhibit pRBC sequestration and prevent disease. In a malaria endemic setting this is likely to be used as an adjunct therapy by reversing existing cytoadherence. Two well-characterized parasite lines plus three recently derived patient isolates were tested for their cytoadherence to purified receptors (CD36 and ICAM-1) as well as endothelial cells. Monoclonal antibodies against human CD36 and ICAM-1 were used to inhibit and reverse infected erythrocyte binding in static and flow-based adhesion assays. Results Anti-ICAM-1 and CD36 monoclonal antibodies were able to inhibit and reverse P. falciparum binding of lab and recently adapted patient isolates in vitro. However, reversal of binding was incomplete and varied in its efficiency between parasite isolates. Conclusions The results show that, as a proof of concept, disturbing existing ligand–receptor interactions is possible and could have potential therapeutic value for severe malaria. The variation seen in the degree of reversing existing binding with different parasite isolates and the incomplete nature of reversal, despite the use of high affinity inhibitors, suggest that anti-adhesion approaches as adjunct therapies for severe malaria may not be effective, and the focus may need to be on inhibitory approaches such as vaccines.
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Affiliation(s)
- Khairul M F Mustaffa
- Institute for Research in Molecular Medicine, Universiti Sains Malaysia, 16150, Kubang Kerian, Kelantan, Malaysia.,Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Janet Storm
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Megan Whittaker
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.,School of Medicine, University of Liverpool, Cedar House, Ashton Street, Liverpool, L69 3GE, UK
| | - Tadge Szestak
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK
| | - Alister G Craig
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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Choveaux DL, Krause RG, Przyborski JM, Goldring JD. Identification and initial characterisation of a Plasmodium falciparum Cox17 copper metallochaperone. Exp Parasitol 2015; 148:30-9. [DOI: 10.1016/j.exppara.2014.11.001] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2014] [Accepted: 11/06/2014] [Indexed: 12/15/2022]
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Mouatcho JC, Goldring JPD. Malaria rapid diagnostic tests: challenges and prospects. J Med Microbiol 2013; 62:1491-1505. [PMID: 24048274 DOI: 10.1099/jmm.0.052506-0] [Citation(s) in RCA: 162] [Impact Index Per Article: 14.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
In the last decade, there has been an upsurge of interest in developing malaria rapid diagnostic test (RDT) kits for the detection of Plasmodium species. Three antigens - Plasmodium falciparum histidine-rich protein 2 (PfHRP2), plasmodial aldolase and plasmodial lactate dehydrogenase (pLDH) - are currently used for RDTs. Tests targeting HRP2 contribute to more than 90% of the malaria RDTs in current use. However, the specificities, sensitivities, numbers of false positives, numbers of false negatives and temperature tolerances of these tests vary considerably, illustrating the difficulties and challenges facing current RDTs. This paper describes recent developments in malaria RDTs, reviewing RDTs detecting PfHRP2, pLDH and plasmodial aldolase. The difficulties associated with RDTs, such as genetic variability in the Pfhrp2 gene and the persistence of antigens in the bloodstream following the elimination of parasites, are discussed. The prospect of overcoming the problems associated with current RDTs with a new generation of alternative malaria antigen targets is also described.
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Affiliation(s)
- Joel C Mouatcho
- Department of Biochemistry, School of Life Science, University of Kwazulu-Natal, Pietermaritzburg, Private Bag X01 Scottsville 3209, South Africa
| | - J P Dean Goldring
- Department of Biochemistry, School of Life Science, University of Kwazulu-Natal, Pietermaritzburg, Private Bag X01 Scottsville 3209, South Africa
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6
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Cumming BM, Watson GMF, Goldring JPD. Plasmodium falciparum: effect of antimalarial drugs, malaria pigment (β-haematin) and Plasmodium falciparum lysate on monocyte GTP-cyclohydrolase 1 gene expression. Exp Parasitol 2011; 129:312-7. [PMID: 21854775 DOI: 10.1016/j.exppara.2011.08.001] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2010] [Revised: 08/01/2011] [Accepted: 08/03/2011] [Indexed: 10/17/2022]
Abstract
In interferon-γ activated human macrophages, GTP-cyclohydrolase 1 catalyses the conversion of guanosine triphosphate to 7,8-dihydroneopterin triphosphate, which is dephosphorylated and oxidized to form neopterin. Elevated levels of neopterin have been detected in the urine and serum of malaria-infected patients. In this study, U937 cells were treated with interferon-γ and one of the following antimalarial drugs: amodiaquine, artemisinin, chloroquine, doxycycline, primaquine, pyrimethamine or quinine. The effects of treating the U937 cells with malaria pigment (β-haematin), latex beads, or Plasmodium falciparum-infected-red blood cell lysates were also investigated. U937 GTP-cyclohydrolase 1 mRNA expression was monitored using reverse-transcriptase-quantitative PCR. Artemisinin, primaquine, and quinine down-regulated GTP-cyclohydrolase 1 gene expression 1.26-, 1.29-, and 1.63-fold, respectively. The remaining drugs had insignificant effects. β-haematin up-regulated GTP-cyclohydrolase 1 mRNA expression 1.18-fold, whereas P. falciparum-infected red blood cell lysate down-regulated expression 1.56-fold. These results show the differing immunomodulatory actions of antimalarial drugs and malaria pigment taking place in monocytes.
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Affiliation(s)
- Bridgette M Cumming
- Department of Biochemistry, School of Biochemistry, Genetics and Microbiology, University of KwaZulu-Natal, Pietermaritzburg Campus, Private Bag X01, Scottsville 3209, South Africa
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7
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Kivity S, Katz U, Daniel N, Nussinovitch U, Papageorgiou N, Shoenfeld Y. Evidence for the use of intravenous immunoglobulins--a review of the literature. Clin Rev Allergy Immunol 2010; 38:201-69. [PMID: 19590986 PMCID: PMC7101816 DOI: 10.1007/s12016-009-8155-9] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
Intravenous immunoglobulins (IVIg) were first introduced in the middle of the twentieth century for the treatment of primary immunodeficiencies. In 1981, Paul Imbach noticed an improvement of immune-mediated thrombocytopenia, in patients receiving IVIg for immunodeficiencies. This opened a new era for the treatment of autoimmune conditions with IVIg. Since then, IVIg has become an important treatment option in a wide spectrum of diseases, including autoimmune and acute inflammatory conditions, most of them off-label (not included in the US Food and Drug Administration recommendation). A panel of immunologists and internists with experience in IVIg therapy reviewed the medical literature for published data concerning treatment with IVIg. The quality of evidence was assessed, and a summary of the available relevant literature in each disease was given. To our knowledge, this is the first all-inclusive comprehensive review, developed to assist the clinician when considering the use of IVIg in autoimmune diseases, immune deficiencies, and other conditions.
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Affiliation(s)
- Shaye Kivity
- Center for Autoimmune Diseases, Sheba Medical Center, Tel Hashomer, Israel
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8
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Sherman IW. References. ADVANCES IN PARASITOLOGY 2008. [DOI: 10.1016/s0065-308x(08)00430-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
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9
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Goldring JPD. Evaluation of immunotherapy to reverse sequestration in the treatment of severe Plasmodium falciparum malaria. Immunol Cell Biol 2005; 82:447-52. [PMID: 15283856 DOI: 10.1111/j.0818-9641.2004.01265.x] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sequestration and the attachment of Plasmodium falciparum malaria-infected RBC to venous endothelial cells involves parasite-encoded ligands interacting with up to nine host receptors. Antisequestration immunotherapy as an adjunct to quinine did not alter the dynamics of parasite clearance or prove beneficial for the patient. Estimated concentrations of antibody likely to reverse adherence in patients were based on the concentrations of parasite ligands, host receptors and patient equivalents derived from in vitro observations. Calculations presented here indicate that concentrations in excess of a fivefold increase in antibody concentrations used in the immunotherapy trial and equivalent to doubling normal peripheral blood antibody concentrations are anticipated for the successful reversal of sequestration to occur. It is suggested that immunotherapy aimed at either parasite ligands or host receptors to reverse sequestration in the treatment of severe malaria infections is unlikely to be successful given the complexity and number of receptors and ligands and the calculated concentrations of antibodies required.
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MESH Headings
- Animals
- Antibodies/pharmacology
- Antibodies/therapeutic use
- Antibodies, Monoclonal/pharmacology
- Antibodies, Monoclonal/therapeutic use
- Antibodies, Protozoan/blood
- Antibodies, Protozoan/therapeutic use
- Antimalarials/therapeutic use
- Endothelium, Vascular/metabolism
- Erythrocytes/parasitology
- Humans
- Ligands
- Malaria, Falciparum/diagnosis
- Malaria, Falciparum/immunology
- Malaria, Falciparum/therapy
- Models, Theoretical
- Receptors, Immunologic/metabolism
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Affiliation(s)
- J P Dean Goldring
- Biochemistry, School of Molecular and Cellular Biosciences, University of KwaZulu-Natal (PMB), Scottsville, South Africa.
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10
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Lou J, Lucas R, Grau GE. Pathogenesis of cerebral malaria: recent experimental data and possible applications for humans. Clin Microbiol Rev 2001; 14:810-20, table of contents. [PMID: 11585786 PMCID: PMC89004 DOI: 10.1128/cmr.14.4.810-820.2001] [Citation(s) in RCA: 165] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/01/2023] Open
Abstract
Malaria still is a major public health problem, partly because the pathogenesis of its major complication, cerebral malaria, remains incompletely understood. Experimental models represent useful tools to better understand the mechanisms of this syndrome. Here, data generated by several models are reviewed both in vivo and in vitro; we propose that some pathogenic mechanisms, drawn from data obtained from experiments in a mouse model, may be instrumental in humans. In particular, tumor necrosis factor (TNF) receptor 2 is involved in this syndrome, implying that the transmembrane form of TNF may be more important than the soluble form of the cytokine. It has also been shown that in addition to differences in immune responsiveness between genetically resistant and susceptible mice, there are marked differences at the level of the target cell of the lesion, namely, the brain endothelial cell. In murine cerebral malaria, a paradoxical role of platelets has been proposed. Indeed, platelets appear to be pathogenic rather than protective in inflammatory conditions because they can potentiate the deleterious effects of TNF. More recently, it has been shown that interactions among platelets, leukocytes, and endothelial cells have phenotypic and functional consequences for the endothelial cells. A better understanding of these complex interactions leading to vascular injury will help improve the outcome of cerebral malaria.
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Affiliation(s)
- J Lou
- Department of Surgery, CH-1211 Geneva 14, Switzerland
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11
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Dondorp AM, Kager PA, Vreeken J, White NJ. Abnormal blood flow and red blood cell deformability in severe malaria. PARASITOLOGY TODAY (PERSONAL ED.) 2000; 16:228-32. [PMID: 10827427 DOI: 10.1016/s0169-4758(00)01666-5] [Citation(s) in RCA: 130] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Obstruction of the microcirculation plays a central role in the pathophysiology of severe malaria. Here, Arjen Dondorp and colleagues describe the various contributors to impaired microcirculatory flow in falciparum malaria: sequestration, rosetting and recent findings regarding impaired red blood cell deformability. The correlation with clinical findings and possible therapeutic consequences are discussed.
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Affiliation(s)
- A M Dondorp
- Department of Internal Medicine, Tropical Medicine and AIDS, Academic Medical Centre, Meibergdreef 9, 1105 AZ Amsterdam, The Netherlands.
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12
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Goldring JD, Padayachee T, Ismail I. Plasmodium falciparum malaria: rosettes are disrupted by quinine, artemisinin, mefloquine, primaquine, pyrimethamine, chloroquine and proguanil. Mem Inst Oswaldo Cruz 1999; 94:667-74. [PMID: 10464415 DOI: 10.1590/s0074-02761999000500021] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
An assay was developed measuring the disruption of rosettes between Plasmodium falciparuminfected (trophozoites) and uninfected erythrocytes by the antimalarial drugs quinine, artemisinin mefloquine, primaquine, pyrimethamine, chloroquine and proguanil. At 4 hr incubation rosettes were disrupted by all the drugs in a dose dependent manner. Artemisinin and quinine were the most effective anti-malarials at disrupting rosettes at their therapeutic concentrations with South African RSA 14, 15, 17 and The Gambian FCR-3 P. falciparum strains. The least effective drugs were proguanil and chloroquine. A combination of artemisinin and mefloquine was more effective than each drug alone. The combinations of pyrimethamine or primaquine, with quinine disrupted more rosettes than quinine alone. Quinine may be an effective drug in the treatment of severe malaria because the drug efficiently reduces the number of rosettes.
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Affiliation(s)
- J D Goldring
- School of Molecular and Cellular Biosciences, University of Natal, South Africa.
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13
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Goldring JP, Nemaorani S. Antimalarial drugs modulate the expression of monocyte receptors. INTERNATIONAL JOURNAL OF IMMUNOPHARMACOLOGY 1999; 21:599-607. [PMID: 10501629 DOI: 10.1016/s0192-0561(99)00039-9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
Abstract
The cytoadherence of four Plasmodium falciparum malaria isolates (FCR-3, RSA-14, 15 and 17) to monocytes was used as a measure of the expression of monocyte receptors after the monocytes had been exposed to seven antimalarial drugs. Quinine, chloroquine, primaquine, pyrimethamine, artemesinin, mefloquine and proguanil all down-regulated the expression of monocyte receptors by 40% or greater at the therapeutic concentrations of each drug. Each malaria isolate had a unique adherence profile for drug induced changes in monocytes. Each drug appeared to alter the expression of more than one monocyte receptor. The most effective drugs were quinine, pyrimethamine and palludrin and the least effective were artemether and mefloquine. The results suggest a previously undetected immunomodulatory action of antimalarial drugs.
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Affiliation(s)
- J P Goldring
- Department of Biochemistry, School of Molecular and Cellular Biosciences, University of Natal (Pietermaritzburg), Scottsville, South Africa.
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14
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Abstract
Sequestration of parasitized red blood cells in the cerebral vasculature is the predisposing event to the development of cerebral malaria during infection with Plasmodium falciparum. The adhesive interaction between these cells and receptors on the endothelial cell (cytoadhesion) occurs in the dynamic environment of the microcirculation, but most studies have neglected this factor and have concentrated on measuring adhesion in static (no flow) assays. Such studies ignore the markedly different rheological properties of parasitized red blood cells that become apparent when adhesion is examined under dynamic, flow conditions that resemble those of the circulation in vivo. Here, Brian Cooke and Ross Coppel review a number of novel aspects of cytoadhesion that have been identified using flow-based assays, and discuss their relevance to the pathophysiology, investigation and clinical management of falciparum malaria.
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Affiliation(s)
- B M Cooke
- Department of Microbiology, Monash University, Clayton, Victoria, Australia.
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15
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Allred DR. Immune Evasion by Babesia bovis and Plasmodium falciparum: Cliff-dwellers of the Parasite World. ACTA ACUST UNITED AC 1995; 11:100-5. [PMID: 15275361 DOI: 10.1016/0169-4758(95)80166-9] [Citation(s) in RCA: 41] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022]
Abstract
Erythrocyte-dwelling parasites, such as Babesia bovis and Plasmodium falciparum, are not accessible to the host immune system during most of their asexual reproductive cycle because they are intracellular. While intracellular, the host immune response must be directed toward the surface of the infected erythrocyte. Immune individuals mount protective antibody and cell-mediated responses which eliminate most of the parasites, yet some survive to establish chronic infections. In this review, David Allred discusses some of the mechanisms used by these parasites to evade individual immune mechanisms targeting the infected erythrocyte to survive in the hostile environment of an effective immune response.
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Affiliation(s)
- D R Allred
- Department of Infectious Diseases, College of Veterinary Medicine, University of Florida, Gainesville 32611-0880, USA.
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16
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Abstract
Erythrocytes infected with mature stages of Plasmodium falciparum malaria adhere to vascular endothelial cells in postcapillary venules of several organs. In some patients, infected cells also form rosettes with uninfected erythrocytes. The special pathology of acute cerebral malaria appears to result from excessive adherence of infected cells in cerebral vessels coupled with occlusion of cerebral blood flow in microvessels by infected cell rosettes. Several endothelial cell proteins have been identified as potential receptors for infected erythrocyte adherence to vascular endothelium, including thrombospondin, CD36, intercellular adhesion molecule-1 (ICAM-1), vascular adhesion molecule-1 (VCAM-1), and endothelial leukocyte adhesion molecule-1 (ELAM-1). The receptor on infected erythrocytes that mediates adhesion to endothelial cells has been identified as a very large malarial protein on infected cells called PfEMP1. PfEMP1 has been shown to bind to CD36 and thrombospondin in vitro. Antibody-mediated blockade or reversal of infected erythrocyte adherence to vascular endothelium is postulated not only to decrease the pathology of blood-stage malaria, but also to lead to infected cell destruction and clearance, especially in the spleen. PfEMP1 is therefore a prime candidate malarial protein for inclusion in a multicomponent asexual malaria vaccine.
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Affiliation(s)
- B L Pasloske
- Affymax Research Institute, Palo Alto, California 94304
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17
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Hommel M. Amplification of cytoadherence in cerebral malaria: towards a more rational explanation of disease pathophysiology. ANNALS OF TROPICAL MEDICINE AND PARASITOLOGY 1993; 87:627-35. [PMID: 8122926 DOI: 10.1080/00034983.1993.11812821] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Cerebral malaria in man and in mice is the consequence of a cascade of events, involving the production of toxins by the parasite and cytokines by the host, and eventually leading to the amplification of the expression of the receptors for cytoadherence on brain capillary endothelial cells. Variations in the intrinsic characteristics of parasite isolates or the genetic make-up of the host and the degree of antimalarial immunity can modulate this sequence of events. A working hypothesis is proposed in which two features of the parasite, the ability to cytoadhere and to produce toxins, are clearly dissociated and where the amplification of cytoadherence receptors is considered crucial. This hypothesis, illustrated by new data from human malaria and rodent models, suggests that cerebral malaria may occur when these features occur together during an infection, while not necessarily within the same parasite clone.
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Affiliation(s)
- M Hommel
- School of Tropical Medicine, Liverpool, U.K
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18
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Cooke BM, Morris-Jones S, Greenwood BM, Nash GB. Adhesion of parasitized red blood cells to cultured endothelial cells: a flow-based study of isolates from Gambian children with falciparum malaria. Parasitology 1993; 107 ( Pt 4):359-68. [PMID: 8278217 DOI: 10.1017/s0031182000067706] [Citation(s) in RCA: 18] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023]
Abstract
Adhesion of parasitized red blood cells to vascular endothelium is thought to play an important role in the development of the ischaemic complications associated with severe falciparum malaria. Using a novel, flow-based assay, we have investigated the adhesion of parasitized red blood cells to formalin-fixed human umbilical vein endothelial cells (HUVEC), for isolates obtained from 32 Gambian subjects with mild or severe falciparum malaria. Red cells infected with wild strains of Plasmodium falciparum were able to adhere to HUVEC under physiologically relevant flow conditions, but the level of adhesion was highly variable, ranging from 1 to 688 adherent cells per mm2 of HUVEC. Within isolates, some adherent parasitized cells remained stationary, whilst other formed less stable interactions and rolled slowly over the cell surface. There was no significant difference in adhesion of parasitized cells between isolates obtained from mild or severe cases of malaria, although a subset of isolates did show very high levels of adhesion. The results suggest that there is not a simple relationship between the adhesion of parasitized cells to cultured endothelial cells (presumably via the receptor ICAM-1) and the clinical severity of the disease, although variation in microvascular adhesion in vivo may still be a determinant of ischaemic complications.
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Affiliation(s)
- B M Cooke
- Department of Haematology, Medical School, University of Birmingham, UK
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19
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Taylor TE, Molyneux ME, Wirima JJ, Borgstein A, Goldring JD, Hommel M. Intravenous immunoglobulin in the treatment of paediatric cerebral malaria. Clin Exp Immunol 1992; 90:357-62. [PMID: 1458672 PMCID: PMC1554573 DOI: 10.1111/j.1365-2249.1992.tb05851.x] [Citation(s) in RCA: 61] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022] Open
Abstract
Hyperimmune globulin can inhibit and reverse the cytoadherence between Plasmodium falciparum-infected erythrocytes and melanoma cells in vitro. Cytoadherence is believed to mediate disease in cerebral malaria. Therefore we studied the efficacy of i.v. immunoglobulin, purified from the plasma of local semi-immune blood donors, as an adjunct to standard treatment for cerebral malaria in Malawian children. The immunoglobulin preparation (IFAT antimalarial antibody titre 1:5120) recognized erythrocyte-associated antigens of each of 22 Malawian P. falciparum isolates studied, and reversed binding of Malawian isolates to melanoma cells. Immunoglobulin did not reverse binding to human monocytes or to cells of the human histiocytic lymphoma cell line U937. Thirty-one children with P. falciparum parasitaemia and unrousable coma were enrolled. All were treated with i.v. quinine dihydrochloride; in addition patients were randomized to receive either immunoglobulin (400 mg/kg by i.v. infusion over 3 h) or placebo (albumen and sucrose by similar infusion) in a double blind trial with sequential analysis. Of 16 patients receiving immunoglobulin, five (31%) died and five survivors had neurological sequelae. Of 15 patients receiving placebo, one (7%) died and two had sequelae. Parasite clearance, fever clearance and coma resolution times in survivors were similar in the two groups. Although the difference in outcome between the two groups was not significant, the trial was stopped because immunoglobulin was demonstrated not to be superior to placebo.
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Affiliation(s)
- T E Taylor
- Department of Paediatrics, Queen Elizabeth Central Hospital, Blantyre, Malawi
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