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Pehrson C, Heno KK, Adams Y, Resende M, Mathiesen L, Soegaard M, de Jongh WA, Theander TG, Salanti A, Nielsen MA. Comparison of functional assays used in the clinical development of a placental malaria vaccine. Vaccine 2016; 35:610-618. [PMID: 28012775 DOI: 10.1016/j.vaccine.2016.12.028] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2016] [Revised: 12/05/2016] [Accepted: 12/08/2016] [Indexed: 01/06/2023]
Abstract
BACKGROUND Malaria in pregnancy is associated with significant morbidity in pregnant women and their offspring. Plasmodium falciparum infected erythrocytes (IE) express VAR2CSA that mediates binding to chondroitin sulphate A (CSA) in the placenta. Two VAR2CSA-based vaccines for placental malaria are in clinical development. The purpose of this study was to evaluate the robustness and comparability of binding inhibition assays used in the clinical development of placental malaria vaccines. METHODS The ability of sera from animals immunised with different VAR2CSA constructs to inhibit IE binding to CSA was investigated in three in vitro assays using 96-well plates, petri dishes, capillary flow and an ex vivo placental perfusion assay. RESULTS The inter-assay variation was not uniform between assays and ranged from above ten-fold in the flow assay to two-fold in the perfusion assay. The intra-assay variation was highest in the petri dish assay. A positive correlation between IE binding avidity and the level of binding after antibody inhibition in the petri dish assay indicate that high avidity IE binding is more difficult to inhibit. The highest binding inhibition sensitivity was found in the 96-well and petri dish assays compared to the flow and perfusion assays where binding inhibition required higher antibody titers. CONCLUSIONS The inhibitory capacity of antibodies is not easily translated between assays and the high sensitivity of the 96-well and petri dish assays stresses the need for comparing serial dilutions of serum. Furthermore, IE binding avidity must be in the same range when comparing data from different days. There was an overall concordance in the capacity of antibody-mediated inhibition, when comparing the in vitro assays with the perfusion assay, which more closely represents in vivo conditions. Importantly the ID1-ID2a protein in a liposomal formulation, currently in a phase I trial, effectively induced antibodies that inhibited IE adhesion in placental tissue.
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Affiliation(s)
- Caroline Pehrson
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark.
| | - Kristine K Heno
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark.
| | - Yvonne Adams
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark.
| | - Mafalda Resende
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark.
| | - Line Mathiesen
- Section of Environmental Health, Department of Public Health, University of Copenhagen, Øster Farimagsgade 5A, 1353 Copenhagen, Denmark.
| | - Max Soegaard
- ExpreS2ion Biotechnologies, SCION-DTU Science Park, Hørsholm, Denmark.
| | - Willem A de Jongh
- ExpreS2ion Biotechnologies, SCION-DTU Science Park, Hørsholm, Denmark.
| | - Thor G Theander
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark.
| | - Ali Salanti
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark.
| | - Morten A Nielsen
- Centre for Medical Parasitology at Department of Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, Denmark; Department of Infectious Diseases, Copenhagen University Hospital (Rigshospitalet), Denmark.
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Rosa TFA, Flammersfeld A, Ngwa CJ, Kiesow M, Fischer R, Zipfel PF, Skerka C, Pradel G. The Plasmodium falciparum blood stages acquire factor H family proteins to evade destruction by human complement. Cell Microbiol 2016; 18:573-90. [PMID: 26457721 PMCID: PMC5063132 DOI: 10.1111/cmi.12535] [Citation(s) in RCA: 40] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2015] [Revised: 09/29/2015] [Accepted: 10/06/2015] [Indexed: 01/24/2023]
Abstract
The acquisition of regulatory proteins is a means of blood-borne pathogens to avoid destruction by the human complement. We recently showed that the gametes of the human malaria parasite Plasmodium falciparum bind factor H (FH) from the blood meal of the mosquito vector to assure successful sexual reproduction, which takes places in the mosquito midgut. While these findings provided a first glimpse of a complex mechanism used by Plasmodium to control the host immune attack, it is hitherto not known, how the pathogenic blood stages of the malaria parasite evade destruction by the human complement. We now show that the human complement system represents a severe threat for the replicating blood stages, particularly for the reinvading merozoites, with complement factor C3b accumulating on the surfaces of the intraerythrocytic schizonts as well as of free merozoites. C3b accumulation initiates terminal complement complex formation, in consequence resulting in blood stage lysis. To inactivate C3b, the parasites bind FH as well as related proteins FHL-1 and CFHR-1 to their surface, and FH binding is trypsin-resistant. Schizonts acquire FH via two contact sites, which involve CCP modules 5 and 20. Blockage of FH-mediated protection via anti-FH antibodies results in significantly impaired blood stage replication, pointing to the plasmodial complement evasion machinery as a promising malaria vaccine target.
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Affiliation(s)
- Thiago F A Rosa
- Division of Cellular and Applied Infection Biology, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| | - Ansgar Flammersfeld
- Division of Cellular and Applied Infection Biology, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| | - Che J Ngwa
- Division of Cellular and Applied Infection Biology, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| | - Meike Kiesow
- Division of Cellular and Applied Infection Biology, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
| | - Rainer Fischer
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstr. 6, 52074, Aachen, Germany
| | - Peter F Zipfel
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, Beutenbergstr. 11a, 07745, Jena, Germany
| | - Christine Skerka
- Department of Infection Biology, Leibniz Institute for Natural Product Research and Infection Biology, Hans-Knöll-Institute, Beutenbergstr. 11a, 07745, Jena, Germany
| | - Gabriele Pradel
- Division of Cellular and Applied Infection Biology, RWTH Aachen University, Worringerweg 1, 52074, Aachen, Germany
- Fraunhofer Institute for Molecular Biology and Applied Ecology, Forckenbeckstr. 6, 52074, Aachen, Germany
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Nielsen MA, Salanti A. High-Throughput Testing of Antibody-Dependent Binding Inhibition of Placental Malaria Parasites. Methods Mol Biol 2015; 1325:241-53. [PMID: 26450394 DOI: 10.1007/978-1-4939-2815-6_20] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
Abstract
The particular virulence of Plasmodium falciparum manifests in diverse severe malaria syndromes as cerebral malaria, severe anemia and placental malaria. The cause of both the severity and the diversity of infection outcome, is the ability of the infected erythrocyte (IE) to bind a range of different human receptors through Plasmodium falciparum erythrocyte membrane protein 1 (PfEMP1) on the surface of the infected cell. As the var genes encoding the large PfEMP1 antigens are extensively polymorphic, vaccine development strategies are focused on targeting the functional binding epitopes. This involves identification of recombinant fragments of PfEMP1s that induce antibodies, which hinder the adhesion of the IE to a given receptor or tissue. Different assays to measure the blocking of adhesion have been described in the literature, each with different advantages. This chapter describes a high-throughput assay used in the preclinical and clinical development of a VAR2CSA based vaccine against placental malaria.
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Affiliation(s)
- Morten A Nielsen
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, CSS Building 22/23, Øster Farimagsgade 5, 2099, Copenhagen K, 1014, Denmark.
| | - Ali Salanti
- Centre for Medical Parasitology, Department of International Health, Immunology and Microbiology, Faculty of Health and Medical Sciences, University of Copenhagen, CSS Building 22/23, Øster Farimagsgade 5, 2099, Copenhagen K, 1014, Denmark.
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Roman G, Crandall IE, Szarek WA. Synthesis and Anti-PlasmodiumActivity of Benzimidazole Analogues Structurally Related to Astemizole. ChemMedChem 2013; 8:1795-804. [DOI: 10.1002/cmdc.201300172] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2013] [Indexed: 11/07/2022]
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Crandall IE, Wasilewski E, Bello AM, Mohmmed A, Malhotra P, Pai EF, Kain KC, Kotra LP. Antimalarial Activities of 6-Iodouridine and Its Prodrugs and Potential for Combination Therapy. J Med Chem 2013; 56:2348-58. [DOI: 10.1021/jm301678j] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Affiliation(s)
- Ian E. Crandall
- Department of Pharmaceutical
Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, M5S 3M2, Canada
| | - Ewa Wasilewski
- Center for Molecular Design
and Preformulations, Toronto General Research Institute, University Health Network, 5-356 TMDT/MaRS, 101 College
Street, Toronto, Ontario, M5G 1L7, Canada
| | - Angelica M. Bello
- Department of Pharmaceutical
Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, M5S 3M2, Canada
- Center for Molecular Design
and Preformulations, Toronto General Research Institute, University Health Network, 5-356 TMDT/MaRS, 101 College
Street, Toronto, Ontario, M5G 1L7, Canada
| | - Asif Mohmmed
- International Center for Genetic Engineering and Biotechnology, Aruna Asaf
Ali Marg, New Delhi 110 067, India
| | - Pawan Malhotra
- International Center for Genetic Engineering and Biotechnology, Aruna Asaf
Ali Marg, New Delhi 110 067, India
| | - Emil F. Pai
- Ontario Cancer Institute, Campbell Family Cancer Research Institute, Toronto
Medical Discoveries Tower, 101 College Street, Toronto, Ontario, M5G
1L7, Canada
- Departments
of Medical Biophysics,
Biochemistry, and Molecular Genetics, University of Toronto, 1 King’s College Circle, Toronto, Ontario, M5S 1A8, Canada
| | - Kevin C. Kain
- McLaughlin Center for Molecular Medicine
and Department of Medicine, University of Toronto, Toronto, Ontario, Canada
- McLaughlin-Rotman Center for Global Health, Toronto General and Western Hospital Foundation, Toronto Medical Discoveries Tower, 101 College Street, Toronto,
Ontario, M5G 1L7, Canada
| | - Lakshmi P. Kotra
- Department of Pharmaceutical
Sciences, Leslie Dan Faculty of Pharmacy, University of Toronto, Toronto, Ontario, M5S 3M2, Canada
- Center for Molecular Design
and Preformulations, Toronto General Research Institute, University Health Network, 5-356 TMDT/MaRS, 101 College
Street, Toronto, Ontario, M5G 1L7, Canada
- McLaughlin Center for Molecular Medicine
and Department of Medicine, University of Toronto, Toronto, Ontario, Canada
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Vlahakis JZ, Mitu S, Roman G, Patricia Rodriguez E, Crandall IE, Szarek WA. The anti-malarial activity of bivalent imidazolium salts. Bioorg Med Chem 2011; 19:6525-42. [DOI: 10.1016/j.bmc.2011.06.002] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2011] [Revised: 05/26/2011] [Accepted: 06/02/2011] [Indexed: 11/29/2022]
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Kong G, Kain KC, Crandall I, Langler RF. Novel disulfides as anticancer/antimalarial agents. ACTA ACUST UNITED AC 2010. [DOI: 10.1080/02786110310001612272] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
Affiliation(s)
- Grace Kong
- a The Toronto General Hospital and the University of Toronto, Tropical Disease Unit , Toronto, Ontario, Canada , M5S 1A8
| | - Kevin C. Kain
- a The Toronto General Hospital and the University of Toronto, Tropical Disease Unit , Toronto, Ontario, Canada , M5S 1A8
| | - Ian Crandall
- a The Toronto General Hospital and the University of Toronto, Tropical Disease Unit , Toronto, Ontario, Canada , M5S 1A8
| | - Richard F. Langler
- b Mount Allison University, Department of Chemistry , Sackville, New Brunswick, Canada , E4L 1G8
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8
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Vlahakis JZ, Lazar C, Crandall IE, Szarek WA. Anti-Plasmodium activity of imidazolium and triazolium salts. Bioorg Med Chem 2010; 18:6184-96. [PMID: 20634079 DOI: 10.1016/j.bmc.2010.05.020] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2010] [Revised: 05/05/2010] [Accepted: 05/06/2010] [Indexed: 11/16/2022]
Abstract
We have previously reported that tetrazolium salts were both potent and specific inhibitors of Plasmodium replication, and that they appear to interact with a parasite component that is both essential and conserved. The use of tetrazolium salts in vivo is limited by the potential reduction of the tetrazolium ring to form an inactive, neutral acyclic formazan. To address this issue imidazolium and triazolium salts were synthesized and evaluated as Plasmodium inhibitors. Many of the imidazolium and triazolium salts were highly potent with active concentrations in the nanomolar range in Plasmodium falciparum cultures, and specific to Plasmodium with highly favorable therapeutic ratios. The results corroborate our hypothesis that an electron-deficient core is required so that the compound may thereby interact with a negatively charged moiety on the parasite merozoite; the side groups in the compound then form favorable interactions with adjacent parasite components and thereby determine both the potency and selectivity of the compound.
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Affiliation(s)
- Jason Z Vlahakis
- Department of Chemistry, Queen's University, Kingston, Ontario, Canada
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9
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Chapman EE, Langler RF, Crandall I. Phloroglucinol sulfonic acid esters as antimalarial/anticancer agents. J Sulphur Chem 2008. [DOI: 10.1080/17415990802346010] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Affiliation(s)
- Erin E. Chapman
- a Department of Chemistry , Mount Allison University , Sackville, New Brunswick, Canada
| | - Richard F. Langler
- a Department of Chemistry , Mount Allison University , Sackville, New Brunswick, Canada
| | - Ian Crandall
- b McLaughlin-Rotman Centre, MaRS Centre, University Health Network and the University of Toronto , Toronto, Ontario, Canada
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10
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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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Crandall IE, Szarek WA, Vlahakis JZ, Xu Y, Vohra R, Sui J, Kisilevsky R. Sulfated cyclodextrins inhibit the entry of Plasmodium into red blood cells. Implications for malarial therapy. Biochem Pharmacol 2006; 73:632-42. [PMID: 17166484 DOI: 10.1016/j.bcp.2006.10.030] [Citation(s) in RCA: 24] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/08/2006] [Revised: 10/27/2006] [Accepted: 10/30/2006] [Indexed: 11/19/2022]
Abstract
The effect of sulfated cyclodextrins on Plasmodium falciparum cultures was determined. alpha-, beta-, and gamma-Cyclodextrins having equal degrees of sulfation inhibited parasite viability to a similar degree, a result suggesting that the ring size of the cyclodextrin is not a critical factor for inhibitory activity. beta-Cyclodextrins containing fewer than two sulfate groups had no inhibitory activity, however, compounds containing 7-17 sulfates were found to be active in the microM range. Examination of treated cultures indicated that intracellular forms of the parasite were unaffected; however, increased numbers of extracellular merozoites were present. Active compounds produced enhanced erythrocyte staining with cationic dyes that could be reduced by stilbene disulfonates, a result suggesting that sulfated cyclodextrins inhibit parasite growth by interacting with the anion transport protein, AE1. Compounds that were found to be active in P. falciparum cultures were also found to inhibit P. berghei merozoite entry and could reduce the parasitemia of P. berghei infection in a mouse model, results suggesting that these compounds inhibit a common step in the merozoite invasion process of at least two Plasmodium species.
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Affiliation(s)
- Ian E Crandall
- Toronto Medical Laboratories and Tropical Disease Unit, Division of Infectious Diseases, Department of Laboratory Medicine and Pathobiology, University of Toronto, Toronto, Ontario, Canada.
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Vlahakis JZ, Kinobe RT, Nakatsu K, Szarek WA, Crandall IE. Anti-Plasmodium activity of imidazole-dioxolane compounds. Bioorg Med Chem Lett 2006; 16:2396-406. [PMID: 16495054 DOI: 10.1016/j.bmcl.2006.01.122] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2005] [Revised: 01/26/2006] [Accepted: 01/27/2006] [Indexed: 11/19/2022]
Abstract
A series of imidazole-dioxolane compounds, which we hypothesize should bind to heme and thus interfere with heme catabolism in the parasite, were assayed for inhibitory activity in Plasmodium falciparum cultures and the results were compared to those obtained with Chinese hamster ovary (CHO) cells. The majority of the compounds displayed a similar ratio of inhibitory activity in the two culture systems; however, a number of the compounds tested showed promising anti-Plasmodium activity. The mechanism of action of these compounds remains unclear, however their inability to act synergistically with chloroquine suggests that, if they are inhibiting heme detoxification, they do so in a manner that does not complement the action of chloroquine.
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Affiliation(s)
- Jason Z Vlahakis
- Department of Chemistry, Queen's University, Kingston, Ont., Canada K7L 3N6
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Darko CA, Angov E, Collins WE, Bergmann-Leitner ES, Girouard AS, Hitt SL, McBride JS, Diggs CL, Holder AA, Long CA, Barnwell JW, Lyon JA. The clinical-grade 42-kilodalton fragment of merozoite surface protein 1 of Plasmodium falciparum strain FVO expressed in Escherichia coli protects Aotus nancymai against challenge with homologous erythrocytic-stage parasites. Infect Immun 2005; 73:287-97. [PMID: 15618165 PMCID: PMC538964 DOI: 10.1128/iai.73.1.287-297.2005] [Citation(s) in RCA: 73] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
A 42-kDa fragment from the C terminus of major merozoite surface protein 1 (MSP1) is among the leading malaria vaccine candidates that target infection by asexual erythrocytic-stage malaria parasites. The MSP1(42) gene fragment from the Vietnam-Oak Knoll (FVO) strain of Plasmodium falciparum was expressed as a soluble protein in Escherichia coli and purified according to good manufacturing practices. This clinical-grade recombinant protein retained some important elements of correct structure, as it was reactive with several functional, conformation-dependent monoclonal antibodies raised against P. falciparum malaria parasites, it induced antibodies (Abs) that were reactive to parasites in immunofluorescent Ab tests, and it induced strong growth and invasion inhibitory antisera in New Zealand White rabbits. The antigen quality was further evaluated by vaccinating Aotus nancymai monkeys and challenging them with homologous P. falciparum FVO erythrocytic-stage malaria parasites. The trial included two control groups, one vaccinated with the sexual-stage-specific antigen of Plasmodium vivax, Pvs25, as a negative control, and the other vaccinated with baculovirus-expressed MSP1(42) (FVO) as a positive control. Enzyme-linked immunosorbent assay (ELISA) Ab titers induced by E. coli MSP1(42) were significantly higher than those induced by the baculovirus-expressed antigen. None of the six monkeys that were vaccinated with the E. coli MSP1(42) antigen required treatment for uncontrolled parasitemia, but two required treatment for anemia. Protective immunity in these monkeys correlated with the ELISA Ab titer against the p19 fragment and the epidermal growth factor (EGF)-like domain 2 fragment of MSP1(42), but not the MSP1(42) protein itself or the EGF-like domain 1 fragment. Soluble MSP1(42) (FVO) expressed in E. coli offers excellent promise as a component of a vaccine against erythrocytic-stage falciparum malaria.
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Affiliation(s)
- Christian A Darko
- Department of Immunology, Walter Reed Army Institute of Research, 503 Robert Grant Ave., Silver Spring, MD 20910, USA
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Ciach M, Zong K, Kain KC, Crandall I. Reversal of mefloquine and quinine resistance in Plasmodium falciparum with NP30. Antimicrob Agents Chemother 2003; 47:2393-6. [PMID: 12878495 PMCID: PMC166084 DOI: 10.1128/aac.47.8.2393-2396.2003] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Quinoline resistance in malaria is frequently compared with P-glycoprotein-mediated multidrug resistance (mdr) in mammalian cells. We have previously reported that nonylphenolethoxylates, such as NP30, are potential Plasmodium falciparum P-glycoprotein substrates and drug efflux inhibitors. We used in vitro assays to compare the ability of verapamil and NP30 to sensitize two parasite isolates to four quinolines: chloroquine (CQ), mefloquine (MF), quinine (QN), and quinidine (QD). NP30 was able to sensitize (reversal, >80%) P. falciparum to MF, QN, QD, and, to a lesser extent, CQ. The presence of 2 micro M verapamil had no effect on mefloquine resistance; however, the presence of verapamil modulated the activities of QN and QD in a manner parallel to that observed for CQ. Genetic analysis of putative quinoline resistance genes did not suggest an association between known point mutations in pfcrt and pfmdr1 and NP30 sensitization activity. We conclude that the sensitization action of NP30 is distinct both phenotypically and genotypically from that of verapamil.
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Affiliation(s)
- Michelle Ciach
- Tropical Disease Unit, Toronto General Hospital, Toronto, Ontario, Canada
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Kisilevsky R, Crandall I, Szarek WA, Bhat S, Tan C, Boudreau L, Kain KC. Short-chain aliphatic polysulfonates inhibit the entry of Plasmodium into red blood cells. Antimicrob Agents Chemother 2002; 46:2619-26. [PMID: 12121942 PMCID: PMC127384 DOI: 10.1128/aac.46.8.2619-2626.2002] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Several steps in the pathogenesis of a Plasmodium falciparum infection depend on interactions of parasite surface proteins with negatively charged sugars on the surface of host cells such as sialate residues or glycosaminoglycans. For these reasons, our previous studies examining agents that interfere with heparan sulfate-protein binding during amyloidogenesis suggested that short-chain aliphatic polysulfonates may prove useful as antimalarial agents. A series of related polysulfonates were synthesized and assessed both in tissue culture with the asexual stages of P. falciparum in human red blood cells and in vivo by use of Plasmodium berghei infections in mice. Poly(vinylsulfonate sodium salt) (molecular weight range, 1,500 to 3,000) proved effective in interfering with P. falciparum merozoite entry into human red blood cells and significantly delaying the increase in the level of P. berghei parasitemia in mice. The concept that anionic molecules that mimic large polysaccharide structures may have antimalarial properties has been suggested and examined previously. Our results suggest that related anionic agents [poly(vinylsulfonate sodium salt)-like molecules] orders of magnitude smaller than those previously considered may prove useful in abrogating merozoite entry into erythrocytes and may potentially block sporozoite entry into liver cells. Structure-activity studies conducted to enhance these properties may provide compounds with scope for significant further analysis and development.
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Affiliation(s)
- Robert Kisilevsky
- Department of Pathology, Queen's University, Kingston, Ontario, Canada K7L 3N6.
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