1
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Challenger JD, Gonçalves BP, Bradley J, Bruxvoort K, Tiono AB, Drakeley C, Bousema T, Ghani AC, Okell LC. How delayed and non-adherent treatment contribute to onward transmission of malaria: a modelling study. BMJ Glob Health 2019; 4:e001856. [PMID: 31908862 PMCID: PMC6936434 DOI: 10.1136/bmjgh-2019-001856] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/19/2019] [Revised: 11/08/2019] [Accepted: 11/10/2019] [Indexed: 12/31/2022] Open
Abstract
Introduction Artemether-lumefantrine (AL) is the most widely-recommended treatment for uncomplicated Plasmodium falciparum malaria. Its efficacy has been extensively assessed in clinical trials. In routine healthcare settings, however, its effectiveness can be diminished by delayed access to treatment and poor adherence. As well as affecting clinical outcomes, these factors can lead to increased transmission, which is the focus of this study. Methods We extend a within-host model of P. falciparum to include gametocytes, the parasite forms responsible for onward transmission. The model includes a pharmacokinetic–pharmacodynamic model of AL, calibrated against both immature and mature gametocytes using individual-level patient data, to estimate the impact that delayed access and imperfect adherence to treatment can have on onward transmission of the parasite to mosquitoes. Results Using survey data from seven African countries to determine the time taken to acquire antimalarials following fever increased our estimates of mean total infectivity of a malaria episode by up to 1.5-fold, compared with patients treated after 24 hours. Realistic adherence behaviour, based on data from a monitored cohort in Tanzania, increased the contribution to transmission by 2.2 to 2.4-fold, compared with a perfectly-adherent cohort. This was driven largely by increased rates of treatment failure leading to chronic infection, rather than prolonged gametocytaemia in patients who have slower, but still successful, clearance of parasites after imperfect adherence to treatment. Our model estimated that the mean infectivity of untreated infections was 29–51 times higher than that of treated infections (assuming perfect drug adherence), underlining the importance of improving treatment coverage. Conclusion Using mathematical modelling, we quantify how delayed treatment and non-adherent treatment can increase transmission compared with prompt effective treatment. We also highlight that transmission from the large proportion of infections which never receive treatment is substantially higher than those treated.
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Affiliation(s)
- Joseph D Challenger
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Bronner P Gonçalves
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - John Bradley
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
| | - Katia Bruxvoort
- Department of Research and Evaluation, Kaiser Permanente Southern California, Pasadena, California, USA.,Department of Global Health and Development, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Alfred B Tiono
- Public Health Department, Centre National de Recherche et de Formation sur le Paludisme (CNRFP), Ouagadougou, Burkina Faso
| | - Chris Drakeley
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom
| | - Teun Bousema
- Department of Immunology and Infection, London School of Hygiene and Tropical Medicine, London, United Kingdom.,Radboud Institute of Health Sciences, Radboud University Medical Center, Nijmegen, Netherlands
| | - Azra C Ghani
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
| | - Lucy C Okell
- MRC Centre for Global Infectious Disease Analysis, Department of Infectious Disease Epidemiology, Imperial College London, London, United Kingdom
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2
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Dhingra SK, Gabryszewski SJ, Small-Saunders JL, Yeo T, Henrich PP, Mok S, Fidock DA. Global Spread of Mutant PfCRT and Its Pleiotropic Impact on Plasmodium falciparum Multidrug Resistance and Fitness. mBio 2019; 10:e02731-18. [PMID: 31040246 PMCID: PMC6495381 DOI: 10.1128/mbio.02731-18] [Citation(s) in RCA: 31] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2018] [Accepted: 03/25/2019] [Indexed: 12/12/2022] Open
Abstract
The global spread of Plasmodium falciparum chloroquine resistance transporter (PfCRT) variant haplotypes earlier caused the widespread loss of chloroquine (CQ) efficacy. In Asia, novel PfCRT mutations that emerged on the Dd2 allelic background have recently been implicated in high-level resistance to piperaquine, and N326S and I356T have been associated with genetic backgrounds in which resistance emerged to artemisinin derivatives. By analyzing large-scale genome sequencing data, we report that the predominant Asian CQ-resistant Dd2 haplotype is undetectable in Africa. Instead, the GB4 and previously unexplored Cam783 haplotypes predominate, along with wild-type, drug-sensitive PfCRT that has reemerged as the major haplotype. To interrogate how these alleles impact drug susceptibility, we generated pfcrt-modified isogenic parasite lines spanning the mutational interval between GB4 and Dd2, which includes Cam783 and involves amino acid substitutions at residues 326 and 356. Relative to Dd2, the GB4 and Cam783 alleles were observed to mediate lower degrees of resistance to CQ and the first-line drug amodiaquine, while resulting in higher growth rates. These findings suggest that differences in growth rates, a surrogate of parasite fitness, influence selection in the context of African infections that are frequently characterized by high transmission rates, mixed infections, increased immunity, and less recourse to treatment. We also observe that the Asian Dd2 allele affords partial protection against piperaquine yet does not directly impact artemisinin efficacy. Our results can help inform the regional recommendations of antimalarials, whose activity is influenced by and, in certain cases, enhanced against select PfCRT variant haplotypes.IMPORTANCE Our study defines the allelic distribution of pfcrt, an important mediator of multidrug resistance in Plasmodium falciparum, in Africa and Asia. We leveraged whole-genome sequence analysis and gene editing to demonstrate how current drug combinations can select different allelic variants of this gene and shape region-specific parasite population structures. We document the ability of PfCRT mutations to modulate parasite susceptibility to current antimalarials in dissimilar, pfcrt allele-specific ways. This study underscores the importance of actively monitoring pfcrt genotypes to identify emerging patterns of multidrug resistance and help guide region-specific treatment options.
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Affiliation(s)
- Satish K Dhingra
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York, USA
| | - Stanislaw J Gabryszewski
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York, USA
| | - Jennifer L Small-Saunders
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York, USA
- Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, New York, USA
| | - Tomas Yeo
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York, USA
| | - Philipp P Henrich
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York, USA
| | - Sachel Mok
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York, USA
| | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Irving Medical Center, New York, New York, USA
- Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, New York, USA
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3
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Nishtala SN, Arora A, Reyes J, Akabas MH. Accessibility of substituted cysteines in TM2 and TM10 transmembrane segments in the Plasmodium falciparum equilibrative nucleoside transporter PfENT1. J Biol Chem 2019; 294:1924-1935. [PMID: 30541922 DOI: 10.1074/jbc.ra118.006547] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2018] [Revised: 11/30/2018] [Indexed: 11/06/2022] Open
Abstract
Infection with Plasmodium species parasites causes malaria. Plasmodium parasites are purine auxotrophic. They import purines via an equilibrative nucleoside transporter (ENT). In P. falciparum, the most virulent species, the equilibrative nucleoside transporter 1 (PfENT1) represents the primary purine uptake pathway. This transporter is a potential target for the development of antimalarial drugs. In the absence of a high-resolution structure for either PfENT1 or a homologous ENT, we used the substituted cysteine accessibility method (SCAM) to investigate the membrane-spanning domain structure of PfENT1 to identify potential inhibitor-binding sites. We previously used SCAM to identify water-accessible residues that line the permeation pathway in transmembrane segment 11 (TM11). TM2 and TM10 lie adjacent to TM11 in an ab initio model of a homologous Leishmania donovani nucleoside transporter. To identify TM2 and TM10 residues in PfENT1 that are at least transiently on the water-accessible transporter surface, we assayed the reactivity of single cysteine-substitution mutants with three methanethiosulfonate (MTS) derivatives. Cysteines substituted for 12 of 14 TM2 segment residues reacted with MTS-ethyl-ammonium-biotin (MTSEA-biotin). At eight positions, MTSEA-biotin inhibited transport, and at four positions substrate transport was potentiated. On an α helical wheel projection of TM2, the four positions where potentiation occurred were located in a cluster on one side of the helix. In contrast, although MTSEA-biotin inhibited 9 of 10 TM10 cysteine-substituted mutants, the reactive residues did not form a pattern consistent with either an α helix or β sheet. These results may help identify the binding site(s) of PfENT1 inhibitors.
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Affiliation(s)
| | - Avish Arora
- From the Departments of Physiology and Biophysics
| | - Jorge Reyes
- From the Departments of Physiology and Biophysics
| | - Myles H Akabas
- From the Departments of Physiology and Biophysics, .,Neuroscience, and.,Medicine, Albert Einstein College of Medicine, Bronx, New York 10461
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4
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Santatiwongchai J, Gleeson D, Gleeson MP. Theoretical Evaluation of the Reaction Mechanism of Serine Hydroxymethyltransferase. J Phys Chem B 2019; 123:407-418. [PMID: 30522268 DOI: 10.1021/acs.jpcb.8b10196] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/22/2022]
Abstract
Serine hydroxymethyltransferase (SHMT) is a pyridoxal phosphate (PLP)-dependent enzyme that catalyzes the reversible conversion of serine and tetrahydrofolate (THF) to glycine and 5,10-methylene THF. SHMT is a folate pathway enzyme and is therefore of considerable medical interest due to its role as an important intervention point for antimalarial, anticancer, and antibacterial treatments. Despite considerable experimental effort, the precise reaction mechanism of SHMT remains unclear. In this study, we explore the mechanism of SHMT to determine the roles of active site residues and the nature and the sequence of chemical steps. Molecular dynamics (MD) methods were employed to generate a suitable starting structure which then underwent analysis using hybrid quantum mechanical/molecular mechanical (QM/MM) simulations. The QM region consisted of 12 key residues, two substrates, and explicit solvent. Our results show that the catalytic reaction proceeds according to a retro-aldol synthetic process with His129 acting as the general base in the reaction. The rate-determining step involves the cleavage of the PLP-serine aldimine Cα-Cβ bond and the formation of formaldehyde in line with experimental evidence. The pyridyl ring of the PLP-serine aldimine substrate exists in deprotonated form, being stabilized directly by Asp208 via a strong H-bond, as well as through interactions with Arg371, Lys237, and His211, and with the surrounding protein which was electrostatically embedded. This knowledge has the potential to impact the design and development of new inhibitors.
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Affiliation(s)
- Jirapat Santatiwongchai
- Department of Chemistry, Faculty of Science , Kasetsart University , Bangkok 10900 , Thailand
| | - Duangkamol Gleeson
- Department of Chemistry, Faculty of Science , King Mongkut's Institute of Technology Ladkrabang , Bangkok 10520 , Thailand
| | - M Paul Gleeson
- Department of Chemistry, Faculty of Science , Kasetsart University , Bangkok 10900 , Thailand.,Department of Biomedical Engineering, Faculty of Engineering , King Mongkut's Institute of Technology Ladkrabang , Bangkok 10520 , Thailand
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A Variant PfCRT Isoform Can Contribute to Plasmodium falciparum Resistance to the First-Line Partner Drug Piperaquine. mBio 2017; 8:mBio.00303-17. [PMID: 28487425 PMCID: PMC5424201 DOI: 10.1128/mbio.00303-17] [Citation(s) in RCA: 76] [Impact Index Per Article: 10.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
Current efforts to reduce the global burden of malaria are threatened by the rapid spread throughout Asia of Plasmodium falciparum resistance to artemisinin-based combination therapies, which includes increasing rates of clinical failure with dihydroartemisinin plus piperaquine (PPQ) in Cambodia. Using zinc finger nuclease-based gene editing, we report that addition of the C101F mutation to the chloroquine (CQ) resistance-conferring PfCRT Dd2 isoform common to Asia can confer PPQ resistance to cultured parasites. Resistance was demonstrated as significantly higher PPQ concentrations causing 90% inhibition of parasite growth (IC90) or 50% parasite killing (50% lethal dose [LD50]). This mutation also reversed Dd2-mediated CQ resistance, sensitized parasites to amodiaquine, quinine, and artemisinin, and conferred amantadine and blasticidin resistance. Using heme fractionation assays, we demonstrate that PPQ causes a buildup of reactive free heme and inhibits the formation of chemically inert hemozoin crystals. Our data evoke inhibition of heme detoxification in the parasite’s acidic digestive vacuole as the primary mode of both the bis-aminoquinoline PPQ and the related 4-aminoquinoline CQ. Both drugs also inhibit hemoglobin proteolysis at elevated concentrations, suggesting an additional mode of action. Isogenic lines differing in their pfmdr1 copy number showed equivalent PPQ susceptibilities. We propose that mutations in PfCRT could contribute to a multifactorial basis of PPQ resistance in field isolates. The global agenda to eliminate malaria depends on the continued success of artemisinin-based combination therapies (ACTs), which target the asexual blood stages of the intracellular parasite Plasmodium. Partial resistance to artemisinin, however, is now established in Southeast Asia, exposing the partner drugs to increased selective pressure. Plasmodium falciparum resistance to the first-line partner piperaquine (PPQ) is now spreading rapidly in Cambodia, resulting in clinical treatment failures. Here, we report that a variant form of the Plasmodium falciparum chloroquine resistance transporter, harboring a C101F mutation edited into the chloroquine (CQ)-resistant Dd2 isoform prevalent in Asia, can confer PPQ resistance in cultured parasites. This was accompanied by a loss of CQ resistance. Biochemical assays showed that PPQ, like CQ, inhibits the detoxification of reactive heme that is formed by parasite-mediated catabolism of host hemoglobin. We propose that novel PfCRT variants emerging in the field could contribute to a multigenic basis of PPQ resistance.
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6
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Antimicrobial Activity of Three Lamiaceae Essential Oils Against Common Oral Pathogens. BALKAN JOURNAL OF DENTAL MEDICINE 2016. [DOI: 10.1515/bjdm-2016-0026] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
Summary
Chemical composition, antimicrobial and cytotoxic activities of commercial essential oils’ samples from the aerial plant parts of H. officinalis, R. officinalis and S. officinalis were investigated. Analyses by GC-FID and GC-MS confirmed 52 oil components. The major constituent of the H. officinalis oil was cis-pinocamphone (34.4%), followed by transpinocamphone (23.3%), and β-pinene (11.3%). Analysis of R. officinalis oil revealed 1.8-cineol as a major constituent (43.8%), as well as transpinocamphone (12.5%), α-pinene (11.5%) and β-pinene (8.2%). The most dominant constituent of S. officinalis oil was cis-thujone (32.7%), in addition to camphor (17.2%), 1.8-cineol (10.1%), α-pinene (8.6%), transthujone (7.7%) and camphene (7.3%). The essential oil antimicrobial activity assay was performed by the use of microdilution method against oral Candida spp. and bacteria, the major causative agents of a number of human oral disorders; all of them were susceptible to tested concentrations of H. officinalis, R. officinalis and S. officinalis essential oils, although the oil of S. officinalis exhibited the lowest antimicrobial potential. The results obtained in this study encourage use of investigated essential oils from Lamiaceae family in development of safe natural agents for prevention and/ or alternative therapy of human oral diseases. However, a special care during development of an effective natural preparation is required.
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7
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Sonopo MS, Pillay A, Chibale K, Marjanovic-Painter B, Donini C, Zeevaart JR. Carbon-14 radiolabeling and tissue distribution evaluation of MMV390048. J Labelled Comp Radiopharm 2016; 59:680-688. [DOI: 10.1002/jlcr.3445] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2016] [Revised: 08/23/2016] [Accepted: 08/23/2016] [Indexed: 11/11/2022]
Affiliation(s)
| | | | - Kelly Chibale
- Drug Discovery and Development Centre (H3D) and South African Medical Research Council Drug Discovery and Development Research Unit, Department of Chemistry; University of Cape Town; Rondebosch South Africa
| | | | | | - Jan R. Zeevaart
- DST/NWU, Preclinical Drug Development Platform; North-West University; Potchefstroom South Africa
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8
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Mechanism of artemisinin resistance for malaria PfATP6 L263 mutations and discovering potential antimalarials: An integrated computational approach. Sci Rep 2016; 6:30106. [PMID: 27471101 PMCID: PMC4965867 DOI: 10.1038/srep30106] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2016] [Accepted: 06/27/2016] [Indexed: 11/08/2022] Open
Abstract
Artemisinin resistance in Plasmodium falciparum threatens global efforts in the elimination or eradication of malaria. Several studies have associated mutations in the PfATP6 gene in conjunction with artemisinin resistance, but the underlying molecular mechanism of the resistance remains unexplored. Associated mutations act as a biomarker to measure the artemisinin efficacy. In the proposed work, we have analyzed the binding affinity and efficacy between PfATP6 and artemisinin in the presence of L263D, L263E and L263K mutations. Furthermore, we performed virtual screening to identify potential compounds to inhibit the PfATP6 mutant proteins. In this study, we observed that artemisinin binding affinity with PfATP6 gets affected by L263D, L263E and L263K mutations. This in silico elucidation of artemisinin resistance enhanced the identification of novel compounds (CID: 10595058 and 10625452) which showed good binding affinity and efficacy with L263D, L263E and L263K mutant proteins in molecular docking and molecular dynamics simulations studies. Owing to the high propensity of the parasite to drug resistance the need for new antimalarial drugs will persist until the malarial parasites are eventually eradicated. The two compounds identified in this study can be tested in in vitro and in vivo experiments as possible candidates for the designing of new potential antimalarial drugs.
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9
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Lee AH, Fidock DA. Evidence of a Mild Mutator Phenotype in Cambodian Plasmodium falciparum Malaria Parasites. PLoS One 2016; 11:e0154166. [PMID: 27100094 PMCID: PMC4839739 DOI: 10.1371/journal.pone.0154166] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/13/2016] [Accepted: 04/09/2016] [Indexed: 12/22/2022] Open
Abstract
Malaria control efforts have been continuously stymied by drug-resistant strains of Plasmodium falciparum, which typically originate in Southeast Asia prior to spreading into high-transmission settings in Africa. One earlier proposed explanation for Southeast Asia being a hotbed of resistance has been the hypermutability or "Accelerated Resistance to Multiple Drugs" (ARMD) phenotype, whereby multidrug-resistant Southeast Asian parasites were reported to exhibit 1,000-fold higher rates of resistance to unrelated antimalarial agents when compared to drug-sensitive parasites. However, three recent studies do not recapitulate this hypermutability phenotype. Intriguingly, genome sequencing of recently derived multidrug-resistant Cambodian isolates has identified a high proportion of DNA repair gene mutations in multidrug-resistant parasites, suggesting their potential role in shaping local parasite evolution. By adapting fluctuation assays for use in P. falciparum, we have examined the in vitro mutation rates of five recent Cambodian isolates and three reference laboratory strains. For these studies we also generated a knockout parasite line lacking the DNA repair factor Exonuclease I. In these assays, parasites were typed for their ability to acquire resistance to KAE609, currently in advanced clinical trials, yielding 13 novel mutations in the Na+/H+-ATPase PfATP4, the primary resistance determinant. We observed no evidence of hypermutability. Instead, we found evidence of a mild mutator (up to a 3.4-fold increase in mutation rate) phenotype in two artemisinin-resistant Cambodian isolates, which carry DNA repair gene mutations. We observed that one such mutation in the Mismatch Repair protein Mlh1 contributes to the mild mutator phenotype when modeled in yeast (scmlh1-P157S). Compared to basal rates of mutation, a mild mutator phenotype may provide a greater overall benefit for parasites in Southeast Asia in terms of generating drug resistance without incurring detrimental fitness costs.
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Affiliation(s)
- Andrew H. Lee
- Department of Microbiology and Immunology, Columbia University, New York, New York, United States of America
| | - David A. Fidock
- Department of Microbiology and Immunology, Columbia University, New York, New York, United States of America
- Division of Infectious Diseases, Department of Medicine, Columbia University, New York, New York, United States of America
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10
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Arora A, Deniskin R, Sosa Y, Nishtala SN, Henrich PP, Kumar TRS, Fidock DA, Akabas MH. Substrate and Inhibitor Specificity of the Plasmodium berghei Equilibrative Nucleoside Transporter Type 1. Mol Pharmacol 2016; 89:678-85. [PMID: 27048953 DOI: 10.1124/mol.115.101386] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2015] [Accepted: 04/04/2016] [Indexed: 12/22/2022] Open
Abstract
Malaria is a critical public health issue in the tropical world, causing extensive morbidity and mortality. Infection by unicellular, obligate intracellular Plasmodium parasites causes malaria. The emergence of resistance to current antimalarial drugs necessitates the development of novel therapeutics. A potential novel drug target is the purine import transporter. Because Plasmodium parasites are purine auxotrophic, they must import purines from their host to fulfill metabolic requirements. They import purines via equilibrative nucleoside transporter 1 (ENT1) homologs. Recently, we used a yeast-based high-throughput screen to identify inhibitors of the P. falciparum ENT1 (PfENT1) that kill P. falciparum parasites in culture. P. berghei infection of mice is an animal model for human malaria. Because P. berghei ENT1 (PbENT1) shares only 60% amino acid sequence identity with PfENT1, we sought to characterize PbENT1 and its sensitivity to our PfENT1 inhibitors. We expressed PbENT1 in purine auxotrophic yeast and used radiolabeled substrate uptake to characterize its function. We showed that PbENT1 transports both purines and pyrimidines. It preferred nucleosides compared with nucleobases. Inosine (IC50 = 3.7 µM) and guanosine (IC50 = 21.3 µM) had the highest affinities. Our recently discovered PfENT1 inhibitors were equally effective against both PbENT1- and PfENT1-mediated purine uptake. The PfENT1 inhibitors are at least 10-fold more potent against PfENT1 than human hENT1. They kill P. berghei parasites in 24-hour ex vivo culture. Thus, the P. berghei murine malaria model may be useful to evaluate the efficacy of PfENT1 inhibitors in vivo and their therapeutic potential for treatment of malaria.
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Affiliation(s)
- Avish Arora
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
| | - Roman Deniskin
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
| | - Yvett Sosa
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
| | - Sita Nirupama Nishtala
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
| | - Philipp P Henrich
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
| | - T R Santha Kumar
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
| | - David A Fidock
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
| | - Myles H Akabas
- Departments of Physiology and Biophysics (A.A., R.D., Y.S., S.N.N., M.H.A.) and Neuroscience and Medicine (M.H.A.), Albert Einstein College of Medicine, Bronx, New York; and Departments Microbiology and Immunology (P.P.H., T.R.S.K., D.A.F.) and Medicine (D.A.F.), Columbia University Medical Center, New York, New York
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11
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Should we abandon quinine plus antibiotic for treating uncomplicated falciparum malaria? A systematic review and meta-analysis of randomized controlled trials. Parasitol Res 2015; 115:903-12. [DOI: 10.1007/s00436-015-4842-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2015] [Accepted: 11/19/2015] [Indexed: 10/22/2022]
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12
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Gutteridge CE, Major JW, Nin DA, Curtis SM, Bhattacharjee AK, Gerena L, Nichols DA. In vitro efficacy of 2,N-bisarylated 2-ethoxyacetamides against Plasmodium falciparum. Bioorg Med Chem Lett 2015; 26:1048-1051. [PMID: 26750257 DOI: 10.1016/j.bmcl.2015.12.032] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2015] [Revised: 12/03/2015] [Accepted: 12/10/2015] [Indexed: 11/24/2022]
Abstract
Investigation of a series of 2,N-bisarylated 2-ethoxyacetamides resulted in the identification of four inhibitors 5, 20, 24, 29 with single-digit micromolar in vitro efficacy against two drug-resistant Plasmodium falciparum strains. These compounds are analogs of structurally-related 1,3-bisaryl-2-propen-1-ones (chalcones), the latter showing efficacy in vitro but not in a malaria-infected mouse. The 2,N-bisarylated 2-ethoxyacetamides (e.g., 2, 5, 20) were shown to possess significantly greater stability in the presence of metabolizing enzymes than the corresponding 1,3-bisaryl-2-propen-1-ones (e.g., 1, 3, 18).
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Affiliation(s)
- Clare E Gutteridge
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA.
| | - Joshua W Major
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Daniel A Nin
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Sean M Curtis
- Department of Chemistry, United States Naval Academy, Annapolis, MD 21402, USA
| | - Apurba K Bhattacharjee
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - Lucia Gerena
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
| | - Daniel A Nichols
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD 20910, USA
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13
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Griesbeck AG, Kleczka M, de Kiff A, Vollmer M, Eske A, Sillner S. Singlet oxygen and natural substrates: functional polyunsaturated models for the photooxidative degradation of carotenoids. PURE APPL CHEM 2015. [DOI: 10.1515/pac-2015-0209] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022]
Abstract
AbstractThe primary chemical reactions of singlet molecular oxygen with polyunsaturated carotenoids are the focus of this research report. Model compounds that exhibit electronic properties and substituent pattern similar to natural carotenes, xanthophylls or apocarotenoids, respectively, were investigated with regard to photooxygenation reactivity. For dienes and trienes as substrates, high tandem reactivity was observed and hydroperoxy-endoperoxides were isolated as the secondary products of singlet oxygen reaction. The electronic gem-effect on the regioselectivity of the ene reaction is conserved also in vinylogous positions and thus appears to originate from a radical-stabilizing effect. In an attempt to combine different peroxide groups derived from natural products as a tool for new pharmaceutically active products, a dyade synthesis of an artemisinine-safranol with subsequent singlet oxygen addition was realized.
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Affiliation(s)
- Axel G. Griesbeck
- 1Department of Chemistry, University of Cologne, Greinstr. 4, 50939 Cologne, Germany
| | - Margarethe Kleczka
- 1Department of Chemistry, University of Cologne, Greinstr. 4, 50939 Cologne, Germany
| | - Alan de Kiff
- 1Department of Chemistry, University of Cologne, Greinstr. 4, 50939 Cologne, Germany
| | - Moritz Vollmer
- 1Department of Chemistry, University of Cologne, Greinstr. 4, 50939 Cologne, Germany
| | - Angelika Eske
- 1Department of Chemistry, University of Cologne, Greinstr. 4, 50939 Cologne, Germany
| | - Sarah Sillner
- 1Department of Chemistry, University of Cologne, Greinstr. 4, 50939 Cologne, Germany
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Garg A, Lukk T, Kumar V, Choi JY, Augagneur Y, Voelker DR, Nair S, Ben Mamoun C. Structure, function and inhibition of the phosphoethanolamine methyltransferases of the human malaria parasites Plasmodium vivax and Plasmodium knowlesi. Sci Rep 2015; 5:9064. [PMID: 25761669 PMCID: PMC4357015 DOI: 10.1038/srep09064] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/27/2014] [Accepted: 02/03/2015] [Indexed: 11/09/2022] Open
Abstract
Phosphoethanolamine methyltransferases (PMTs) catalyze the three-step methylation of phosphoethanolamine to form phosphocholine, a critical step in the synthesis of phosphatidylcholine in a select number of eukaryotes including human malaria parasites, nematodes and plants. Genetic studies in the malaria parasite Plasmodium falciparum have shown that the methyltransferase PfPMT plays a critical function in parasite development and differentiation. The presence of PMT orthologs in other malaria parasites that infect humans and their absence in mammals make them ideal targets for the development of selective antimalarials with broad specificity against different Plasmodium species. Here we describe the X-ray structures and biochemical properties of PMT orthologs from Plasmodium vivax and Plasmodium knowlesi and show that both enzymes are inhibited by amodiaquine and NSC158011, two drugs with potent antimalarial activity. Metabolic studies in a yeast mutant that relies on PkPMT or PvPMT for survival demonstrated that these compounds inhibit phosphatidylcholine biosynthesis from ethanolamine. Our structural and functional data provide insights into the mechanism of catalysis and inhibition of PMT enzymes and set the stage for a better design of more specific and selective antimalarial drugs.
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Affiliation(s)
- Aprajita Garg
- Department of Internal Medicine, Yale University School of Medicine, New Haven CT, 06520 USA
| | - Tiit Lukk
- 1] Department of Biochemistry, University of Illinois at Urbana-Champaign [2] Cornell High Energy Synchrotron Source, Cornell University
| | - Vidya Kumar
- Department of Internal Medicine, Yale University School of Medicine, New Haven CT, 06520 USA
| | - Jae-Yeon Choi
- Basic Science Section, Department of Medicine, National Jewish Health, Denver, Colorado 80206
| | - Yoann Augagneur
- Department of Internal Medicine, Yale University School of Medicine, New Haven CT, 06520 USA
| | - Dennis R Voelker
- Basic Science Section, Department of Medicine, National Jewish Health, Denver, Colorado 80206
| | - Satish Nair
- Department of Biochemistry, University of Illinois at Urbana-Champaign
| | - Choukri Ben Mamoun
- Department of Internal Medicine, Yale University School of Medicine, New Haven CT, 06520 USA
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Kwiatkowski D. Malaria genomics: tracking a diverse and evolving parasite population. Int Health 2015; 7:82-4. [PMID: 25733556 PMCID: PMC4379983 DOI: 10.1093/inthealth/ihv007] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2015] [Revised: 01/21/2015] [Accepted: 01/21/2015] [Indexed: 11/14/2022] Open
Abstract
Malaria parasites are continually evolving to evade the immune system and human attempts to control the disease. To eliminate malaria from regions where it is deeply entrenched we need ways of monitoring what is going on in the parasite population, detecting problematic changes as soon as they arise, and executing a prompt and effective response based on a deep understanding of this natural evolutionary process. Powerful new tools to address this problem are emerging from the fast-growing field of genomic epidemiology, driven by new sequencing technologies and computational methods that allow parasite genome variation to be studied in much greater detail and in many more samples than was previously considered possible. These new tools will provide a deep understanding of what is going on in the parasite population, generating actionable knowledge for strategic planning of control interventions, for monitoring their effects and steering them for greatest impact, and for raising the alert if things start to go wrong.
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Affiliation(s)
- Dominic Kwiatkowski
- Wellcome Trust Sanger Institute, Hinxton, Cambridge, CB10 1SA and Oxford University, Henry Wellcome Building for Molecular Physiology, Old Road Campus, Headington, Oxford, OX3 7BN, UK
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Xia ZG, Wang RB, Wang DQ, Feng J, Zheng Q, Deng CS, Abdulla S, Guan YY, Ding W, Yao JW, Qian YJ, Bosman A, Newman RD, Ernest T, O’leary M, Xiao N. China-Africa cooperation initiatives in malaria control and elimination. ADVANCES IN PARASITOLOGY 2015; 86:319-37. [PMID: 25476890 PMCID: PMC7149756 DOI: 10.1016/b978-0-12-800869-0.00012-3] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Malaria has affected human health globally with a significant burden of disease, and also has impeded social and economic development in the areas where it is present. In Africa, many countries have faced serious challenges in controlling malaria, in part due to major limitations in public health systems and primary health care infrastructure. Although China is a developing country, a set of control strategies and measures in different local settings have been implemented successfully by the National Malaria Control Programme over the last 60 years, with a low cost of investment. It is expected that Chinese experience may benefit malaria control in Africa. This review will address the importance and possibility of China–Africa collaboration in control of malaria in targeted African countries, as well as how to proceed toward the goal of elimination where this is technically feasible.
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Affiliation(s)
- Zhi-Gui Xia
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Ru-Bo Wang
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Duo-Quan Wang
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Jun Feng
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Qi Zheng
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Chang-Sheng Deng
- Guangzhou University of Traditional Chinese Medicine, Guangdong, People’s Republic of China
| | | | - Ya-Yi Guan
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Wei Ding
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Jia-Wen Yao
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Ying-Jun Qian
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
| | - Andrea Bosman
- Global Malaria Programme, World Health Organization, Geneva, Switzerland
| | | | - Tambo Ernest
- Centre for Sustainable Malaria Control, Faculty of Natural and Environmental Science; Center for Sustainable Malaria Control, Biochemistry Department, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa
| | - Michael O’leary
- World Health Organization, China Representative Office, Beijing, People’s Republic of China
| | - Ning Xiao
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention; Key Laboratory of Parasite and Vector Biology, MOH; WHO Collaborating Centre for Malaria, Schistosomiasis and Filariasis; Shanghai, People’s Republic of China
- Corresponding author: E-mail:
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Sahi S, Rai S, Chaudhary M, Nain V. Modeling of human M1 aminopeptidases for in silico screening of potential Plasmodium falciparum alanine aminopeptidase (PfA-M1) specific inhibitors. Bioinformation 2014; 10:518-25. [PMID: 25258488 PMCID: PMC4166772 DOI: 10.6026/97320630010518] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/18/2014] [Accepted: 06/27/2014] [Indexed: 11/23/2022] Open
Abstract
Plasmodium falciparum alanine M1-aminopeptidase (PfA-M1) is a validated target for anti-malarial drug development. Presence of significant similarity between PfA-M1 and human M1-aminopeptidases, particularly within regions of enzyme active site leads to problem of non-specificity and off-target binding for known aminopeptidase inhibitors. Molecular docking based in silico screening approach for off-target binding has high potential but requires 3D-structure of all human M1-aminopeptidaes. Therefore, in the present study 3D structural models of seven human M1-aminopeptidases were developed. The robustness of docking parameters and quality of predicted human M1-aminopeptidases structural models was evaluated by stereochemical analysis and docking of their respective known inhibitors. The docking scores were in agreement with the inhibitory concentrations elucidated in enzyme assays of respective inhibitor enzyme combinations (r2≈0.70). Further docking analysis of fifteen potential PfA-M1 inhibitors (virtual screening identified) showed that three compounds had less docking affinity for human M1-aminopeptidases as compared to PfA-M1. These three identified potential lead compounds can be validated with enzyme assays and used as a scaffold for designing of new compounds with increased specificity towards PfA-M1.
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Affiliation(s)
- Shakti Sahi
- School of Biotechnology, Gautam Buddha University, Greater Noida, 201312, India
| | - Sneha Rai
- School of Biotechnology, Gautam Buddha University, Greater Noida, 201312, India
| | - Meenakshi Chaudhary
- School of Biotechnology, Gautam Buddha University, Greater Noida, 201312, India
| | - Vikrant Nain
- School of Biotechnology, Gautam Buddha University, Greater Noida, 201312, India
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18
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Diversity and population structure of Plasmodium falciparum in Thailand based on the spatial and temporal haplotype patterns of the C-terminal 19-kDa domain of merozoite surface protein-1. Malar J 2014; 13:54. [PMID: 24521474 PMCID: PMC3931489 DOI: 10.1186/1475-2875-13-54] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2013] [Accepted: 01/27/2014] [Indexed: 11/21/2022] Open
Abstract
Background The 19-kDa C-terminal region of the merozoite surface protein-1 of the human malaria parasite Plasmodium falciparum (PfMSP-119) constitutes the major component on the surface of merozoites and is considered as one of the leading candidates for asexual blood stage vaccines. Because the protein exhibits a level of sequence variation that may compromise the effectiveness of a vaccine, the global sequence diversity of PfMSP-119 has been subjected to extensive research, especially in malaria endemic areas. In Thailand, PfMSP-119 sequences have been derived from a single parasite population in Tak province, located along the Thailand-Myanmar border, since 1995. However, the extent of sequence variation and the spatiotemporal patterns of the MSP-119 haplotypes along the Thai borders with Laos and Cambodia are unknown. Methods Sixty-three isolates of P. falciparum from five geographically isolated populations along the Thai borders with Myanmar, Laos and Cambodia in three transmission seasons between 2002 and 2008 were collected and culture-adapted. The msp-1 gene block 17 was sequenced and analysed for the allelic diversity, frequency and distribution patterns of PfMSP-119 haplotypes in individual populations. The PfMSP-119 haplotype patterns were then compared between parasite populations to infer the population structure and genetic differentiation of the malaria parasite. Results Five conserved polymorphic positions, which accounted for five distinct haplotypes, of PfMSP-119 were identified. Differences in the prevalence of PfMSP-119 haplotypes were detected in different geographical regions, with the highest levels of genetic diversity being found in the Kanchanaburi and Ranong provinces along the Thailand-Myanmar border and Trat province located at the Thailand-Cambodia border. Despite this variability, the distribution patterns of individual PfMSP-119 haplotypes seemed to be very similar across the country and over the three malarial transmission seasons, suggesting that gene flow may operate between parasite populations circulating in Thailand and the three neighboring countries. Conclusion The major MSP-119 haplotypes of P. falciparum populations in all endemic populations during three transmission seasons in Thailand were identified, providing basic information on the common haplotypes of MSP-119 that is of use for malaria vaccine development and inferring the population structure of P. falciparum populations in Thailand.
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Pidot SJ, Coyne S, Kloss F, Hertweck C. Antibiotics from neglected bacterial sources. Int J Med Microbiol 2014; 304:14-22. [DOI: 10.1016/j.ijmm.2013.08.011] [Citation(s) in RCA: 93] [Impact Index Per Article: 9.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
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20
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Choi YH, Yu AM. ABC transporters in multidrug resistance and pharmacokinetics, and strategies for drug development. Curr Pharm Des 2014; 20:793-807. [PMID: 23688078 PMCID: PMC6341993 DOI: 10.2174/138161282005140214165212] [Citation(s) in RCA: 382] [Impact Index Per Article: 38.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2013] [Accepted: 05/09/2013] [Indexed: 12/18/2022]
Abstract
Multidrug resistance (MDR) is a serious problem that hampers the success of cancer pharmacotherapy. A common mechanism is the overexpression of ATP-binding cassette (ABC) efflux transporters in cancer cells such as P-glycoprotein (P-gp/ABCB1), multidrug resistance-associated protein 1 (MRP1/ABCC1) and breast cancer resistance protein (BCRP/ABCG2) that limit the exposure to anticancer drugs. One way to overcome MDR is to develop ABC efflux transporter inhibitors to sensitize cancer cells to chemotherapeutic drugs. The complete clinical trials thus far have showen that those tested chemosensitizers only add limited or no benefits to cancer patients. Some MDR modulators are merely toxic, and others induce unwanted drug-drug interactions. Actually, many ABC transporters are also expressed abundantly in the gastrointestinal tract, liver, kidney, brain and other normal tissues, and they largely determine drug absorption, distribution and excretion, and affect the overall pharmacokinetic properties of drugs in humans. In addition, ABC transporters such as P-gp, MRP1 and BCRP co-expressed in tumors show a broad and overlapped specificity for substrates and MDR modulators. Thus reliable preclinical assays and models are required for the assessment of transporter-mediated flux and potential effects on pharmacokinetics in drug development. In this review, we provide an overview of the role of ABC efflux transporters in MDR and pharmacokinetics. Preclinical assays for the assessment of drug transport and development of MDR modulators are also discussed.
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Affiliation(s)
| | - Ai-Ming Yu
- Biochemistry & Molecular Medicine, UC Davis Medical Center, 2700 Stockton Blvd., Suite 2132, Sacramento, CA 95817, USA.
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21
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Nzila A, Okombo J, Molloy AM. Impact of folate supplementation on the efficacy of sulfadoxine/pyrimethamine in preventing malaria in pregnancy: the potential of 5-methyl-tetrahydrofolate. J Antimicrob Chemother 2013; 69:323-30. [PMID: 24126794 DOI: 10.1093/jac/dkt394] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
Malaria remains the leading cause of mortality and morbidity in children under the age of 5 years and pregnant women. To counterbalance the malaria burden in pregnancy, an intermittent preventive treatment strategy has been developed. This is based on the use of the antifolate sulfadoxine/pyrimethamine, taken at specified intervals during pregnancy, and reports show that this approach reduces the malaria burden in pregnancy. Pregnancy is also associated with the risk of neural tube defects (NTDs), especially in women with low folate status, and folic acid supplementation is recommended in pregnancy to lower the risk of NTDs. Thus, in malaria-endemic areas, pregnant women have to take both antifolate medication to prevent malaria and folic acid to lower the risk of NTDs. However, the concomitant use of folate and antifolate is associated with a decrease in antifolate efficacy, exposing pregnant women to malaria. Thus, there is genuine concern that this strategy may not be appropriate. We have reviewed work carried out on malaria folate metabolism and antifolate efficacy in the context of folate supplementation. This review shows that: (i) the folate supplementation effect on antifolate efficacy is dose-dependent, and folic acid doses required to protect pregnant women from NTDs will not decrease antifolate activity; and (ii) 5-methyl-tetrahydrofolate, the predominant form of folate in the blood circulation, could be administered (even at high dose) concomitantly with antifolate without affecting antifolate efficacy. Thus, strategies exist to protect pregnant women from malaria while maintaining adequate folate levels in the body to reduce the occurrence of NTDs.
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Affiliation(s)
- Alexis Nzila
- Department of Biology, King Fahd University of Petroleum and Minerals, PO Box 468, Dhahran, 31261, Saudi Arabia
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Burrows JN, van Huijsduijnen RH, Möhrle JJ, Oeuvray C, Wells TNC. Designing the next generation of medicines for malaria control and eradication. Malar J 2013; 12:187. [PMID: 23742293 PMCID: PMC3685552 DOI: 10.1186/1475-2875-12-187] [Citation(s) in RCA: 207] [Impact Index Per Article: 18.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2013] [Accepted: 05/29/2013] [Indexed: 11/10/2022] Open
Abstract
In the fight against malaria new medicines are an essential weapon. For the parts of the world where the current gold standard artemisinin combination therapies are active, significant improvements can still be made: for example combination medicines which allow for single dose regimens, cheaper, safer and more effective medicines, or improved stability under field conditions. For those parts of the world where the existing combinations show less than optimal activity, the priority is to have activity against emerging resistant strains, and other criteria take a secondary role. For new medicines to be optimal in malaria control they must also be able to reduce transmission and prevent relapse of dormant forms: additional constraints on a combination medicine. In the absence of a highly effective vaccine, new medicines are also needed to protect patient populations. In this paper, an outline definition of the ideal and minimally acceptable characteristics of the types of clinical candidate molecule which are needed (target candidate profiles) is suggested. In addition, the optimal and minimally acceptable characteristics of combination medicines are outlined (target product profiles). MMV presents now a suggested framework for combining the new candidates to produce the new medicines. Sustained investment over the next decade in discovery and development of new molecules is essential to enable the long-term delivery of the medicines needed to combat malaria.
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Affiliation(s)
- Jeremy N Burrows
- Medicines for Malaria Venture-MMV, PO Box 1826, Route de Pré-Bois 20, Geneva 151215, Switzerland
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Guler JL, Freeman DL, Ahyong V, Patrapuvich R, White J, Gujjar R, Phillips MA, DeRisi J, Rathod PK. Asexual populations of the human malaria parasite, Plasmodium falciparum, use a two-step genomic strategy to acquire accurate, beneficial DNA amplifications. PLoS Pathog 2013; 9:e1003375. [PMID: 23717205 PMCID: PMC3662640 DOI: 10.1371/journal.ppat.1003375] [Citation(s) in RCA: 56] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 04/05/2013] [Indexed: 11/18/2022] Open
Abstract
Malaria drug resistance contributes to up to a million annual deaths. Judicious deployment of new antimalarials and vaccines could benefit from an understanding of early molecular events that promote the evolution of parasites. Continuous in vitro challenge of Plasmodium falciparum parasites with a novel dihydroorotate dehydrogenase (DHODH) inhibitor reproducibly selected for resistant parasites. Genome-wide analysis of independently-derived resistant clones revealed a two-step strategy to evolutionary success. Some haploid blood-stage parasites first survive antimalarial pressure through fortuitous DNA duplications that always included the DHODH gene. Independently-selected parasites had different sized amplification units but they were always flanked by distant A/T tracks. Higher level amplification and resistance was attained using a second, more efficient and more accurate, mechanism for head-to-tail expansion of the founder unit. This second homology-based process could faithfully tune DNA copy numbers in either direction, always retaining the unique DNA amplification sequence from the original A/T-mediated duplication for that parasite line. Pseudo-polyploidy at relevant genomic loci sets the stage for gaining additional mutations at the locus of interest. Overall, we reveal a population-based genomic strategy for mutagenesis that operates in human stages of P. falciparum to efficiently yield resistance-causing genetic changes at the correct locus in a successful parasite. Importantly, these founding events arise with precision; no other new amplifications are seen in the resistant haploid blood stage parasite. This minimizes the need for meiotic genetic cleansing that can only occur in sexual stage development of the parasite in mosquitoes. Malaria parasites kill up to a million people around the world every year. Emergence of resistance to drugs remains a key obstacle against elimination of malaria. In the laboratory, parasites can efficiently acquire resistance to experimental antimalarials by changing DNA at the target locus. This happens efficiently even for an antimalarial that the parasite has never encountered in a clinical setting. In this study, we formally demonstrate how parasites achieve this feat: first, individual parasites in a population of millions randomly amplify large regions of DNA between short sequence repeats of adenines (A) or thymines (T) that are peppered throughout the malaria parasite genome. The rare lucky parasite that amplifies DNA coding for the target of the antimalarial, along with dozens of its neighboring genes, gains an evolutionary advantage and survives. In a second step, to withstand increasing drug pressure and to achieve higher levels of resistance, each parasite line makes additional copies of this region. This second expansion does not rely on the random A/T-based DNA rearrangements but, instead, a more precise amplification mechanism that retains the unique signature of co-amplified genes created earlier in each parasite. Generation of multiple copies of the target genes in the parasite genome may be the beginning of other beneficial changes for the parasite, including the future acquisition of mutations.
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Affiliation(s)
- Jennifer L. Guler
- Departments of Chemistry and Global Health, University of Washington, Seattle, Washington, United States of America
| | - Daniel L. Freeman
- Departments of Chemistry and Global Health, University of Washington, Seattle, Washington, United States of America
| | - Vida Ahyong
- Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, United States of America
| | - Rapatbhorn Patrapuvich
- Departments of Chemistry and Global Health, University of Washington, Seattle, Washington, United States of America
| | - John White
- Departments of Chemistry and Global Health, University of Washington, Seattle, Washington, United States of America
| | - Ramesh Gujjar
- Departments of Chemistry and Global Health, University of Washington, Seattle, Washington, United States of America
| | - Margaret A. Phillips
- Department of Pharmacology, University of Texas Southwestern Medical Center at Dallas, Dallas, Texas, United States of America
| | - Joseph DeRisi
- Howard Hughes Medical Institute, University of California San Francisco, San Francisco, California, United States of America
| | - Pradipsinh K. Rathod
- Departments of Chemistry and Global Health, University of Washington, Seattle, Washington, United States of America
- * E-mail:
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MDR1-associated resistance to artesunate+mefloquine does not impair blood-stage parasite fitness in a rodent malaria model. INFECTION GENETICS AND EVOLUTION 2013; 14:340-6. [PMID: 23318648 DOI: 10.1016/j.meegid.2012.12.011] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/03/2012] [Revised: 12/05/2012] [Accepted: 12/07/2012] [Indexed: 11/20/2022]
Abstract
If drug-resistant malaria mutants are less fit than sensitive forms, they will wane over time when active drug pressure is removed and the overall sensitivity to the drug may be restored. However, most studies addressing this issue have been largely retrospective. Here, we undertook a predictive study, using mutant rodent malaria parasites resistant to the Artemisinin combination treatment (ACT) version of artesunate+mefloquine (ATN+MF) to gain insights about their ability to compete with ATN+MF-sensitive forms in untreated hosts. Previously, Plasmodium chabaudi parasites resistant to ATN+MF were selected in vivo through prolonged passaging in mice under increasing doses of the two drugs, and shown to harbour duplication of the mdr1 gene. Here, the resistant parasite, AS-ATNMF1, was mixed with its progenitor AS-ATN in different proportions and each mixture was injected into mice that were left untreated. Absolute percentage parasitaemias and the proportion of each parasite were then monitored by microscopy and proportional sequencing, respectively, every two days for a period of 14days. AS-ATNMF1 outperformed its progenitor AS-ATN over the whole sampling period regardless of the relative starting proportion of each parasite clone. In order to assess if consecutive sub-inoculations could have been responsible for the apparent fitness gain of the resistant parasite, its growth was compared to that of AS-ATN27P, a parasite which was passaged the same number of times as AS-ATNMF1, but left untreated. Although small fluctuations in the proportion of each parasite were observed through time, the relative abundance of each on the last day of sampling (Day 14) was virtually identical to that of the starting inoculum. We conclude that there is no fitness cost associated with MDR1-associated ATN+MF resistance in vivo. These observations offer the first insights about the within-host dynamics between ACT-resistant and -sensitive parasites in absence of drug pressure.
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The promiscuous binding of pharmaceutical drugs and their transporter-mediated uptake into cells: what we (need to) know and how we can do so. Drug Discov Today 2012. [PMID: 23207804 DOI: 10.1016/j.drudis.2012.11.008] [Citation(s) in RCA: 117] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/27/2022]
Abstract
A recent paper in this journal sought to counter evidence for the role of transport proteins in effecting drug uptake into cells, and questions that transporters can recognize drug molecules in addition to their endogenous substrates. However, there is abundant evidence that both drugs and proteins are highly promiscuous. Most proteins bind to many drugs and most drugs bind to multiple proteins (on average more than six), including transporters (mutations in these can determine resistance); most drugs are known to recognise at least one transporter. In this response, we alert readers to the relevant evidence that exists or is required. This needs to be acquired in cells that contain the relevant proteins, and we highlight an experimental system for simultaneous genome-wide assessment of carrier-mediated uptake in a eukaryotic cell (yeast).
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Rosental B, Hadad U, Sinay R, Braiman A, Porgador A, Pollack Y. Dual fluorescent labelling of the human malaria parasite Plasmodium falciparum for the analysis of the ABC type transporter pfmdr2. Malar J 2012; 11:371. [PMID: 23137170 PMCID: PMC3546028 DOI: 10.1186/1475-2875-11-371] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/02/2012] [Accepted: 11/02/2012] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The study of the Plasmodium falciparum heavy metal transporter gene pfmdr2 employed radioactive labelled heavy metal. As the use of radioactive isotopes shrank considerably during the last few years, resulting in the cessation of the production of some isotopes, amongst them Cadmium109 which was used for that purpose, a different approach had to be developed. Herein, a dual fluorescent labelling of heavy metals accumulation in the P. falciparum parasite is proposed as an alternative to the use of radioactive labelled heavy metals. METHODS Plasmodium falciparum Cd resistant and sensitive strains at the trophozoite stage were used in this study. The cells were cultured at different CdCl2 concentrations and for different time periods followed by staining of the infected red blood cells with Fluo-3/AM for Cd detection and Hoechst 33342 for parasite DNA labelling. The fluorescent analysis was done by flow cytometry and confocal microscopy. RESULTS The results show that the sensitive strain has a higher Fluo-3/AM fluorescence in a Cd concentration and time dependent manner, whereas in the resistant strain Fluo-3/AM fluorescence levels were negligible and increased only at high concentrations of Cd and at long incubation periods, but to a much lesser extent than the sensitive strain. No Cd uptake is observed in uninfected red blood cells populations originating from cultures infected with either sensitive or resistant strain. In addition, confocal microscopy overlay of Fluo-3/AM and Hoechst staining shows that the Cd metal accumulates in the parasite itself. CONCLUSIONS The dual fluorescent labelling is a valid method for detecting heavy metal accumulation in P. falciparum. Furthermore, in contrast to the use of radioactive labelled heavy metal, the fluorescent labelling enables us to differentiate between the different populations existing in a P. falciparum infected red blood cells cultures and thus actually study a phenomenon at the level of a single cell.
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Affiliation(s)
- Benyamin Rosental
- The Shraga Segal Department of Microbiology and Immunology, Faculty of Health Sciences, Ben-Gurion University of the Negev, P,O, Box 653, Beer-Sheva, 84105, Israel
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Cytostatic versus cytocidal activities of chloroquine analogues and inhibition of hemozoin crystal growth. Antimicrob Agents Chemother 2012; 57:356-64. [PMID: 23114783 DOI: 10.1128/aac.01709-12] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023] Open
Abstract
We report an improved, nonhazardous, high-throughput assay for in vitro quantification of antimalarial drug inhibition of β-hematin (hemozoin) crystallization performed under conditions that are more physiological relative to previous assays. The assay uses the differential detergent solubility of crystalline and noncrystalline forms of heme and is optimized via the use of lipid catalyst. Using this assay, we quantify the effect of pH on the crystal growth-inhibitory activities of current quinoline antimalarials, evaluate the catalytic efficiencies of different lipids, and test for a possible correlation between hemozoin inhibition by drugs versus their antiplasmodial activity. Consistent with several previous reports, we found a good correlation between hemozoin inhibition potency versus cytostatic antiplasmodial potency (50% inhibitory concentration) for a series of chloroquine (CQ) analogues. However, we found no correlation between hemozoin inhibition potency and cytocidal antiplasmodial potency (50% lethal dose) for the same drugs, suggesting that cellular targets for these two layers of 4-aminoquinoline drug activity differ. This important concept is also explored further for QN and its stereoisomers in the accompanying paper (A. P. Gorka, K. S. Sherlach, A. C. de Dios, and P. D. Roepe, Antimicrob. Agents Chemother. 57:365-374, 2013).
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PfCRT and its role in antimalarial drug resistance. Trends Parasitol 2012; 28:504-14. [PMID: 23020971 DOI: 10.1016/j.pt.2012.08.002] [Citation(s) in RCA: 183] [Impact Index Per Article: 15.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2012] [Revised: 08/09/2012] [Accepted: 08/13/2012] [Indexed: 12/15/2022]
Abstract
Plasmodium falciparum resistance to chloroquine, the former gold standard antimalarial drug, is mediated primarily by mutant forms of the chloroquine resistance transporter (PfCRT). These mutations impart upon PfCRT the ability to efflux chloroquine from the intracellular digestive vacuole, the site of drug action. Recent studies reveal that PfCRT variants can also affect parasite fitness, protect immature gametocytes against chloroquine action, and alter P. falciparum susceptibility to current first-line therapies. These results highlight the need to be vigilant in screening for the appearance of novel pfcrt alleles that could contribute to new multi-drug resistance phenotypes.
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Ludin P, Woodcroft B, Ralph SA, Mäser P. In silico prediction of antimalarial drug target candidates. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2012; 2:191-9. [PMID: 24533280 DOI: 10.1016/j.ijpddr.2012.07.002] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/19/2012] [Revised: 06/28/2012] [Accepted: 07/03/2012] [Indexed: 10/28/2022]
Abstract
The need for new antimalarials is persistent due to the emergence of drug resistant parasites. Here we aim to identify new drug targets in Plasmodium falciparum by phylogenomics among the Plasmodium spp. and comparative genomics to Homo sapiens. The proposed target discovery pipeline is largely independent of experimental data and based on the assumption that P. falciparum proteins are likely to be essential if (i) there are no similar proteins in the same proteome and (ii) they are highly conserved across the malaria parasites of mammals. This hypothesis was tested using sequenced Saccharomycetaceae species as a touchstone. Consecutive filters narrowed down the potential target space of P. falciparum to proteins that are likely to be essential, matchless in the human proteome, expressed in the blood stages of the parasite, and amenable to small molecule inhibition. The final set of 40 candidate drug targets was significantly enriched in essential proteins and comprised proven targets (e.g. dihydropteroate synthetase or enzymes of the non-mevalonate pathway), targets currently under investigation (e.g. calcium-dependent protein kinases), and new candidates of potential interest such as phosphomannose isomerase, phosphoenolpyruvate carboxylase, signaling components, and transporters. The targets were prioritized based on druggability indices and on the availability of in vitro assays. Potential inhibitors were inferred from similarity to known targets of other disease systems. The identified candidates from P. falciparum provide insight into biochemical peculiarities and vulnerable points of the malaria parasite and might serve as starting points for rational drug discovery.
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Affiliation(s)
- Philipp Ludin
- Swiss Tropical and Public Health Institute, 4002 Basel, Switzerland ; University of Basel, 4000 Basel, Switzerland
| | - Ben Woodcroft
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria 3010, Australia
| | - Stuart A Ralph
- Department of Biochemistry and Molecular Biology, Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Victoria 3010, Australia
| | - Pascal Mäser
- Swiss Tropical and Public Health Institute, 4002 Basel, Switzerland ; University of Basel, 4000 Basel, Switzerland
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