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Sibley CH, Price RN. Monitoring antimalarial drug resistance: Applying lessons learned from the past in a fast-moving present. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2012; 2:126-33. [PMID: 24533274 DOI: 10.1016/j.ijpddr.2012.03.004] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/16/2011] [Revised: 03/25/2012] [Accepted: 03/28/2012] [Indexed: 11/19/2022]
Abstract
The need for robust surveillance of antimalarial drugs is more urgent than it has ever been. In the western region of Cambodia, artemisinin resistance has emerged in Plasmodium falciparum and threatens to undermine the efficacy of highly effective artemisinin combination therapies. Although some manfestations of artemisinin tolerance are unique to this class of drug, many of its properties mirror previous experience in understanding and tracking resistance to other antimalarials. In this review we outline the spectrum of approaches that were developed to understand the evolution and spread of antifolate resistance, highlighting the importance of integrating information from different methodologies towards a better understanding of the underlying biologic processes. We consider how to apply our experience in investigating and attempting to contain antifolate resistance to inform our prospective assessment of novel antimalarial resistance patterns and their subsequent spread.
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Affiliation(s)
- Carol Hopkins Sibley
- WorldWide Antimalarial Resistance Network, Box 355065, University of Washington, Seattle, WA 98195 5065, USA
| | - Ric N Price
- Global Health Division, Menzies School of Health Research and Charles Darwin University, Darwin, Northern Territory, Australia ; Center for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, United Kingdom
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102
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The aminopeptidase inhibitor CHR-2863 is an orally bioavailable inhibitor of murine malaria. Antimicrob Agents Chemother 2012; 56:3244-9. [PMID: 22450967 DOI: 10.1128/aac.06245-11] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Malaria remains a significant risk in many areas of the world, with resistance to the current antimalarial pharmacopeia an ever-increasing problem. The M1 alanine aminopeptidase (PfM1AAP) and M17 leucine aminopeptidase (PfM17LAP) are believed to play a role in the terminal stages of digestion of host hemoglobin and thereby generate a pool of free amino acids that are essential for parasite growth and development. Here, we show that an orally bioavailable aminopeptidase inhibitor, CHR-2863, is efficacious against murine malaria.
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103
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Cui L, Yan G, Sattabongkot J, Cao Y, Chen B, Chen X, Fan Q, Fang Q, Jongwutiwes S, Parker D, Sirichaisinthop J, Kyaw MP, Su XZ, Yang H, Yang Z, Wang B, Xu J, Zheng B, Zhong D, Zhou G. Malaria in the Greater Mekong Subregion: heterogeneity and complexity. Acta Trop 2012. [PMID: 21382335 DOI: 10.1016/j.actatropica.2011.02.016.malaria] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 04/24/2023]
Abstract
The Greater Mekong Subregion (GMS), comprised of six countries including Cambodia, China's Yunnan Province, Lao PDR, Myanmar (Burma), Thailand and Vietnam, is one of the most threatening foci of malaria. Since the initiation of the WHO's Mekong Malaria Program a decade ago, malaria situation in the GMS has greatly improved, reflected in the continuous decline in annual malaria incidence and deaths. However, as many nations are moving towards malaria elimination, the GMS nations still face great challenges. Malaria epidemiology in this region exhibits enormous geographical heterogeneity with Myanmar and Cambodia remaining high-burden countries. Within each country, malaria distribution is also patchy, exemplified by 'border malaria' and 'forest malaria' with high transmission occurring along international borders and in forests or forest fringes, respectively. 'Border malaria' is extremely difficult to monitor, and frequent malaria introductions by migratory human populations constitute a major threat to neighboring, malaria-eliminating countries. Therefore, coordination between neighboring countries is essential for malaria elimination from the entire region. In addition to these operational difficulties, malaria control in the GMS also encounters several technological challenges. Contemporary malaria control measures rely heavily on effective chemotherapy and insecticide control of vector mosquitoes. However, the spread of multidrug resistance and potential emergence of artemisinin resistance in Plasmodium falciparum make resistance management a high priority in the GMS. This situation is further worsened by the circulation of counterfeit and substandard artemisinin-related drugs. In most endemic areas of the GMS, P. falciparum and Plasmodium vivax coexist, and in recent malaria control history, P. vivax has demonstrated remarkable resilience to control measures. Deployment of the only registered drug (primaquine) for the radical cure of vivax malaria is severely undermined due to high prevalence of glucose-6-phosphate dehydrogenase deficiency in target human populations. In the GMS, the dramatically different ecologies, diverse vector systems, and insecticide resistance render traditional mosquito control less efficient. Here we attempt to review the changing malaria epidemiology in the GMS, analyze the vector systems and patterns of malaria transmission, and identify the major challenges the malaria control community faces on its way to malaria elimination.
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Affiliation(s)
- Liwang Cui
- Department of Entomology, The Pennsylvania State University, University Park, 16801, USA.
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104
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Cui L, Yan G, Sattabongkot J, Cao Y, Chen B, Chen X, Fan Q, Fang Q, Jongwutiwes S, Parker D, Sirichaisinthop J, Kyaw MP, Su XZ, Yang H, Yang Z, Wang B, Xu J, Zheng B, Zhong D, Zhou G. Malaria in the Greater Mekong Subregion: heterogeneity and complexity. Acta Trop 2012; 121:227-39. [PMID: 21382335 DOI: 10.1016/j.actatropica.2011.02.016] [Citation(s) in RCA: 167] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 02/18/2011] [Accepted: 02/26/2011] [Indexed: 10/18/2022]
Abstract
The Greater Mekong Subregion (GMS), comprised of six countries including Cambodia, China's Yunnan Province, Lao PDR, Myanmar (Burma), Thailand and Vietnam, is one of the most threatening foci of malaria. Since the initiation of the WHO's Mekong Malaria Program a decade ago, malaria situation in the GMS has greatly improved, reflected in the continuous decline in annual malaria incidence and deaths. However, as many nations are moving towards malaria elimination, the GMS nations still face great challenges. Malaria epidemiology in this region exhibits enormous geographical heterogeneity with Myanmar and Cambodia remaining high-burden countries. Within each country, malaria distribution is also patchy, exemplified by 'border malaria' and 'forest malaria' with high transmission occurring along international borders and in forests or forest fringes, respectively. 'Border malaria' is extremely difficult to monitor, and frequent malaria introductions by migratory human populations constitute a major threat to neighboring, malaria-eliminating countries. Therefore, coordination between neighboring countries is essential for malaria elimination from the entire region. In addition to these operational difficulties, malaria control in the GMS also encounters several technological challenges. Contemporary malaria control measures rely heavily on effective chemotherapy and insecticide control of vector mosquitoes. However, the spread of multidrug resistance and potential emergence of artemisinin resistance in Plasmodium falciparum make resistance management a high priority in the GMS. This situation is further worsened by the circulation of counterfeit and substandard artemisinin-related drugs. In most endemic areas of the GMS, P. falciparum and Plasmodium vivax coexist, and in recent malaria control history, P. vivax has demonstrated remarkable resilience to control measures. Deployment of the only registered drug (primaquine) for the radical cure of vivax malaria is severely undermined due to high prevalence of glucose-6-phosphate dehydrogenase deficiency in target human populations. In the GMS, the dramatically different ecologies, diverse vector systems, and insecticide resistance render traditional mosquito control less efficient. Here we attempt to review the changing malaria epidemiology in the GMS, analyze the vector systems and patterns of malaria transmission, and identify the major challenges the malaria control community faces on its way to malaria elimination.
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105
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Cui L, Yan G, Sattabongkot J, Chen B, Cao Y, Fan Q, Parker D, Sirichaisinthop J, Su XZ, Yang H, Yang Z, Wang B, Zhou G. Challenges and prospects for malaria elimination in the Greater Mekong Subregion. Acta Trop 2012; 121:240-5. [PMID: 21515238 DOI: 10.1016/j.actatropica.2011.04.006] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2011] [Revised: 03/29/2011] [Accepted: 04/06/2011] [Indexed: 10/18/2022]
Abstract
Despite significant improvement in the malaria situation of the Greater Mekong Subregion (GMS), malaria control for the region continues to face a multitude of challenges. The extremely patchy malaria distribution, especially along international borders, makes disease surveillance and targeted control difficult. The vector systems are also diverse with dramatic differences in habitat ecology, biting behavior, and vectorial capacity, and there is a lack of effective transmission surveillance and control tools. Finally, in an era of heavy deployment of artemisinin-based combination therapies, the region acts as an epicenter of drug resistance, with the emergence of artemisinin resistant Plasmodium falciparum posing a threat to both regional and global malaria elimination campaigns. This problem is further exacerbated by the circulation of counterfeit and substandard artemisinin drugs. Accordingly, this Southeast Asian Malaria Research Center, consisting of a consortium of US and regional research institutions, has proposed four interlinked projects to address these most urgent problems in malaria control. The aims of these projects will help to substantially improve our understanding of malaria epidemiology, vector systems and their roles in malaria transmission, as well as the mechanisms of drug resistance in parasites. Through the training of next-generation scientists in malaria research, this program will help build up and strengthen regional research infrastructure and capacities, which are essential for sustained malaria control in this region.
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Pascual A, Parola P, Benoit-Vical F, Simon F, Malvy D, Picot S, Delaunay P, Basset D, Maubon D, Faugère B, Ménard G, Bourgeois N, Oeuvray C, Didillon E, Rogier C, Pradines B. Ex vivo activity of the ACT new components pyronaridine and piperaquine in comparison with conventional ACT drugs against isolates of Plasmodium falciparum. Malar J 2012; 11:45. [PMID: 22333675 PMCID: PMC3305508 DOI: 10.1186/1475-2875-11-45] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2011] [Accepted: 02/14/2012] [Indexed: 01/29/2023] Open
Abstract
Background The aim of the present work was to assess i) ex vivo activity of pyronaridine (PND) and piperaquine (PPQ), as new components of artemisinin-based combination therapy (ACT), to define susceptibility baseline, ii) their activities compared to other partner drugs, namely monodesethylamodiaquine (MDAQ), lumefantrine (LMF), mefloquine (MQ), artesunate (AS) and dihydroartemisinin (DHA) against 181 Plasmodium falciparum isolates from African countries, India and Thailand, and iii) in vitro cross-resistance with other quinoline drugs, chloroquine (CQ) or quinine (QN). Methods The susceptibility of the 181 P. falciparum isolates to the nine anti-malarial drugs was assessed using the standard 42-hours 3H-hypoxanthine uptake inhibition method. Results The IC50 values for PND ranged from 0.55 to 80.0 nM (geometric mean = 19.9 nM) and from 11.8 to 217.3 nM for PPQ (geometric mean = 66.8 nM). A significant positive correlation was shown between responses to PPQ and PND responses (rho = 0.46) and between PPQ and MDAQ (rho = 0.30). No significant correlation was shown between PPQ IC50 and responses to other anti-malarial drugs. A significant positive correlation was shown between responses to PND and MDAQ (rho = 0.37), PND and LMF (rho = 0.28), PND and QN (rho = 0.24), PND and AS (rho = 0.19), PND and DHA (rho = 0.18) and PND and CQ (rho = 0.16). All these coefficients of correlation are too low to suggest cross-resistance between PPQ or PND and the other drugs. Conclusions In this study, the excellent anti-malarial activity of PPQ and PND was confirmed. The absence of cross-resistance with quinolines and artemisinin derivatives is consistent with the efficacy of the combinations of PPQ and DHA or PND and AS in areas where parasites are resistant to conventional anti-malarial drugs.
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Affiliation(s)
- Aurélie Pascual
- Unité de Recherche en Biologie et Epidémiologie Parasitaires Unité de Recherche pour les Maladies Infectieuses et Tropicales Emergentes UMR-6236, Institut de Recherche Biomédicale des Armées, Allée du Médecin-colonel Jamot,-BP 60109, 13262 Marseille Cedex, France
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107
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Individual Plasmodium vivax msp1 variants within polyclonal P. vivax infections display different propensities for relapse. J Clin Microbiol 2012; 50:1449-51. [PMID: 22205791 DOI: 10.1128/jcm.06212-11] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Using a newly developed Plasmodium vivax merozoite surface protein 1 gene (Pvmsp1) heteroduplex tracking assay, we genotyped 107 P. vivax infections in individuals from Cambodia, 45 of whom developed recurrent parasitemia within 42 days. The majority of isolates were polyclonal, but recurrent parasitemias displayed fewer variants compared to initial parasitemias. Two Pvmsp1 gene variants occurred more frequently in the initial genotypes of those who developed recurrent parasitemia, representing the first time P. vivax variants associated with a higher risk of relapse have been described.
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108
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Jones PM, Robinson MW, Dalton JP, George AM. The Plasmodium falciparum malaria M1 alanyl aminopeptidase (PfA-M1): insights of catalytic mechanism and function from MD simulations. PLoS One 2011; 6:e28589. [PMID: 22205955 PMCID: PMC3244404 DOI: 10.1371/journal.pone.0028589] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2011] [Accepted: 11/11/2011] [Indexed: 11/29/2022] Open
Abstract
Malaria caused by several species of Plasmodium is major parasitic disease of humans, causing 1–3 million deaths worldwide annually. The widespread resistance of the human parasite to current drug therapies is of major concern making the identification of new drug targets urgent. While the parasite grows and multiplies inside the host erythrocyte it degrades the host cell hemoglobin and utilizes the released amino acids to synthesize its own proteins. The P. falciparum malarial M1 alanyl-aminopeptidase (PfA-M1) is an enzyme involved in the terminal stages of hemoglobin digestion and the generation of an amino acid pool within the parasite. The enzyme has been validated as a potential drug target since inhibitors of the enzyme block parasite growth in vitro and in vivo. In order to gain further understanding of this enzyme, molecular dynamics simulations using data from a recent crystal structure of PfA-M1 were performed. The results elucidate the pentahedral coordination of the catalytic Zn in these metallo-proteases and provide new insights into the roles of this cation and important active site residues in ligand binding and in the hydrolysis of the peptide bond. Based on the data, we propose a two-step catalytic mechanism, in which the conformation of the active site is altered between the Michaelis complex and the transition state. In addition, the simulations identify global changes in the protein in which conformational transitions in the catalytic domain are transmitted at the opening of the N-terminal 8 Å-long channel and at the opening of the 30 Å-long C-terminal internal chamber that facilitates entry of peptides to the active site and exit of released amino acids. The possible implications of these global changes with regard to enzyme function are discussed.
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Affiliation(s)
- Peter M. Jones
- School of Medical and Molecular Biosciences, Sydney, New South Wales, Australia
- i3 Institute, University of Technology Sydney, Sydney, New South Wales, Australia
| | - Mark W. Robinson
- i3 Institute, University of Technology Sydney, Sydney, New South Wales, Australia
| | - John P. Dalton
- Institute of Parasitology, McGill University, Montreal, Quebec, Canada
| | - Anthony M. George
- School of Medical and Molecular Biosciences, Sydney, New South Wales, Australia
- i3 Institute, University of Technology Sydney, Sydney, New South Wales, Australia
- * E-mail:
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109
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Abstract
Antimalarial chemotherapy is an important component of all malaria control programmes throughout the world. This is especially so in light of the fact that there are no antimalarial vaccines which are available for clinical use at present. Emergence and spread of malaria parasites which are resistant to many of the available antimalarials today is, therefore, a major cause for concern. Till date, resistance to all groups of antimalarials excluding artemisinin has been reported. In recent years, in vitro resistance to even artemisinin has been described. While resistance to antibacterial agents has come to prominence as a clinical problem in recent years, antiparasitic resistance in general and antimalarial resistance in particular has not received much attention, especially in the Indian scenario. The present review deals with commonly used antimalarial drugs and the mechanisms of resistance to them. Various methods of detecting antimalarial resistance and avoiding the same have also been dealt with. Newer parasite targets which can be used in developing newer antimalarial agents and antimalarials obtained from plants have also been mentioned.
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Affiliation(s)
- S C Parija
- Department of Microbiology, Jawaharlal Institute of Postgraduate Medical Education and Research, Pondicherry, India.
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110
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Flegg JA, Guerin PJ, White NJ, Stepniewska K. Standardizing the measurement of parasite clearance in falciparum malaria: the parasite clearance estimator. Malar J 2011; 10:339. [PMID: 22074219 PMCID: PMC3305913 DOI: 10.1186/1475-2875-10-339] [Citation(s) in RCA: 212] [Impact Index Per Article: 16.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2011] [Accepted: 11/10/2011] [Indexed: 11/10/2022] Open
Abstract
Background A significant reduction in parasite clearance rates following artesunate treatment of falciparum malaria, and increased failure rates following artemisinin combination treatments (ACT), signaled emergent artemisinin resistance in Western Cambodia. Accurate measurement of parasite clearance is therefore essential to assess the spread of artemisinin resistance in Plasmodium falciparum. The slope of the log-parasitaemia versus time relationship is considered to be the most robust measure of anti-malarial effect. However, an initial lag phase of numerical instability often precedes a steady exponential decline in the parasite count after the start of anti-malarial treatment. This lag complicates the clearance estimation, introduces observer subjectivity, and may influence the accuracy and consistency of reported results. Methods To address this problem, a new approach to modelling clearance of malaria parasites from parasitaemia-time profiles has been explored and validated. The methodology detects when a lag phase is present, selects the most appropriate model (linear, quadratic or cubic) to fit log-transformed parasite data, and calculates estimates of parasite clearance adjusted for this lag phase. Departing from previous approaches, parasite counts below the level of detection are accounted for and not excluded from the calculation. Results Data from large clinical studies with frequent parasite counts were examined. The effect of a lag phase on parasite clearance rate estimates is discussed, using individual patient data examples. As part of the World Wide Antimalarial Resistance Network's (WWARN) efforts to make innovative approaches available to the malaria community, an automated informatics tool: the parasite clearance estimator has been developed. Conclusions The parasite clearance estimator provides a consistent, reliable and accurate method to estimate the lag phase and malaria parasite clearance rate. It could be used to detect early signs of emerging resistance to artemisinin derivatives and other compounds which affect ring-stage clearance.
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Affiliation(s)
- Jennifer A Flegg
- WorldWide Anti-malarial Resistance Network (WWARN) and Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, University of Oxford, Churchill Hospital, Old Road, Oxford, OX3 7LJ, UK
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111
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LaCrue AN, Scheel M, Kennedy K, Kumar N, Kyle DE. Effects of artesunate on parasite recrudescence and dormancy in the rodent malaria model Plasmodium vinckei. PLoS One 2011; 6:e26689. [PMID: 22039533 PMCID: PMC3200358 DOI: 10.1371/journal.pone.0026689] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/26/2011] [Accepted: 10/02/2011] [Indexed: 11/25/2022] Open
Abstract
Artemisinin (ART) is the recommended first line therapy for treating uncomplicated and drug-resistant Plasmodium falciparum, the most pathogenic form of malaria. However, treatment failure following ART monotherapy is not uncommon and resistance to this rapidly acting drug has been reported in the Thai-Cambodian border. Recent in vitro studies have shown that following treatment with dihydroartemisinin (DHA), the development of ring-stage parasites is arrested for up to 20 days. These arrested (i.e. dormant) rings could be responsible for the recrudescence of infection that is observed following ART monotherapy. To develop a better understanding of the stage-specific effects of ART and determine if dormancy occurs in vivo, the ART derivative artesunate (AS) was used to treat mice infected with the synchronous rodent malaria parasites P. vinckei petteri (non-lethal) and P. v. vinckei (lethal). Results show that in both the non-lethal and lethal strains, ring-stage parasites are the least susceptible to treatment with AS and that the day of treatment has more of an impact on recrudescence than the total dose administered. Additionally, 24 hrs post-treatment with AS, dormant forms similar in morphology to those seen in vitro were observed. Finally, rate of recrudescence studies suggest that there is a positive correlation between the number of dormant parasites present and when recrudescence occurs in the vertebrate host. Collectively, these data suggest that dormancy occurs in vivo and contributes to recrudescence that is observed following AS treatment. It is possible that this may represent a novel mechanism of parasite survival following treatment with AS.
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Affiliation(s)
- Alexis N. LaCrue
- Department of Global Health, University of South Florida, Tampa, Florida, United States of America
- * E-mail: (DEK); (ANL)
| | - Misty Scheel
- Department of Global Health, University of South Florida, Tampa, Florida, United States of America
| | - Katherine Kennedy
- Department of Global Health, University of South Florida, Tampa, Florida, United States of America
| | - Nikesh Kumar
- Department of Global Health, University of South Florida, Tampa, Florida, United States of America
| | - Dennis E. Kyle
- Department of Global Health, University of South Florida, Tampa, Florida, United States of America
- * E-mail: (DEK); (ANL)
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Fall B, Diawara S, Sow K, Baret E, Diatta B, Fall KB, Mbaye PS, Fall F, Diémé Y, Rogier C, Wade B, Bercion R, Pradines B. Ex vivo susceptibility of Plasmodium falciparum isolates from Dakar, Senegal, to seven standard anti-malarial drugs. Malar J 2011; 10:310. [PMID: 22014157 PMCID: PMC3210113 DOI: 10.1186/1475-2875-10-310] [Citation(s) in RCA: 41] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2011] [Accepted: 10/20/2011] [Indexed: 11/15/2022] Open
Abstract
Background As a result of widespread chloroquine and sulphadoxine-pyrimethamine resistance, artemisinin-based combination therapy (ACT) (which includes artemether-lumefantrine and artesunate-amodiaquine) has been recommended as a first-line anti-malarial regimen in Senegal since 2006. Since then, there have been very few reports on the ex vivo susceptibility of Plasmodium falciparum to anti-malarial drugs. To examine whether parasite susceptibility has been affected by the widespread use of ACT, the ex vivo susceptibility of local isolates was assessed at the military hospital of Dakar. Methods The ex vivo susceptibility of 93 P. falciparum isolates from Dakar was successfully determined using the Plasmodium lactate dehydrogenase (pLDH) ELISA for the following drugs: chloroquine (CQ), quinine (QN), mefloquine (MQ), monodesethylamodiaquine (MDAQ), lumefantrine (LMF), dihydroartemisinin (DHA) and doxycycline (DOX). Results After transformation of the isolate IC50 in ratio of IC50 according to the susceptibility of the 3D7 reference strain (isolate IC50/3D7 IC50), the prevalence of the in vitro resistant isolates with reduced susceptibility was 50% for MQ, 22% for CQ, 12% for DOX, 6% for both QN and MDAQ and 1% for the drugs LMF and DHA. The highest significant positive correlations were shown between responses to CQ and MDAQ (r = 0.569; P < 0.0001), LMF and QN (r = 0.511; P < 0.0001), LMF and DHA (r = 0.428; P = 0.0001), LMF and MQ (r = 0.413; P = 0.0002), QN and DHA (r = 0.402; P = 0.0003) and QN and MQ (r = 0.421; P = 0.0001). Conclusions The introduction of ACT in 2002 has not induced a decrease in P. falciparum susceptibility to the drugs DHA, MDAQ and LMF, which are common ACT components. However, the prevalence of P. falciparum isolates with reduced susceptibility has increased for both MQ and DOX. Taken together, these data suggest that intensive surveillance of the P. falciparum in vitro susceptibility to anti-malarial drugs in Senegal is required.
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Affiliation(s)
- Bécaye Fall
- 1Laboratoire d’étude de la chimiosensibilité du paludisme, Fédération deslaboratoires, Hôpital Principal de Dakar, Dakar, Sénégal
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113
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Hien TT, Hanpithakpong W, Truong NT, Dung NT, Toi PV, Farrar J, Lindegardh N, Tarning J, Ashton M. Orally formulated artemisinin in healthy fasting Vietnamese male subjects: a randomized, four-sequence, open-label, pharmacokinetic crossover study. Clin Ther 2011; 33:644-54. [PMID: 21665048 PMCID: PMC3118832 DOI: 10.1016/j.clinthera.2011.04.017] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 04/26/2011] [Indexed: 11/16/2022]
Abstract
Background Artemisinin derivatives are used in antimalarial drug combination therapy. Artemisinin and piperaquine have recently been proven to be prospective candidates for combination therapy in the treatment of uncomplicated Plasmodium falciparum malaria. Objective The goal of this study was to evaluate the relative bioavailability and to characterize the pharmacokinetic properties of a new micronized powder formulation of artemisinin against the previous standard Vietnamese formulation when administered as a single oral dose or in combination with piperaquine. Methods This was a single-center, randomized, 4-sequence, open-label, crossover study conducted in 15 healthy male Vietnamese volunteers under fasting conditions with a washout period of 3 weeks between study visits. A single oral dose of 160 or 500 mg of artemisinin was administered alone or in combination with piperaquine. Potential adverse events were monitored daily by the clinician and by using laboratory test results. Frequent blood samples were drawn for 12 hours after dose. Artemisinin was quantified in plasma using LC-MS/MS. Pharmacokinetic parameters were computed from the plasma concentration–time profiles using a noncompartmental analysis method. Results Pharmacokinetic parameters Tmax, Cmax, AUC0-∞, Vd/F, CL/F, and t1/2 (mean [SD]) for the new formulation of artemisinin were 1.83 (0.88) hours, 178 (97) ng/mL, 504 (210) h × ng/mL, 1270 (780) L, 401 (260) L/h, and 2.21 (0.29) hours, respectively. The mean percentage of the test/reference formulation ratio for the logarithmically transformed values of Cmax, AUC0–last, and AUC0–∞ were 121% (90% CI, 92.5–158), 122% (90% CI, 101–148), and 120% (90% CI, 98.0–146), respectively. Conclusions This single-dose study found that the dose-normalized Cmax, AUC0–last, and AUC0–∞ mean geometric differences between the test and reference formulations were relatively small (<40%) and will probably not have a clinical impact in the treatment of malaria infections.
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Affiliation(s)
- Tran Tinh Hien
- Hospital for Tropical Diseases, Ho Chi Minh City, Vietnam
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114
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Recrudescent Plasmodium falciparum infections in children in an endemic area following artemisinin–based combination treatments: Implications for disease control. ASIAN PACIFIC JOURNAL OF TROPICAL DISEASE 2011. [DOI: 10.1016/s2222-1808(11)60027-3] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/18/2022]
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115
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Meningeal inflammation increases artemether concentrations in cerebrospinal fluid in Papua New Guinean children treated with intramuscular artemether. Antimicrob Agents Chemother 2011; 55:5027-33. [PMID: 21859936 DOI: 10.1128/aac.00375-11] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Although the artemisinin-associated neurotoxicity identified in vitro and in animal studies has not been confirmed clinically, only one adult study has measured cerebrospinal fluid (CSF) concentrations after administration of conventional doses. Potential artemisinin neurotoxicity could be serious in children, especially those with meningitis and, consequently, a compromised blood-brain barrier. We measured CSF/plasma artemether and dihydroartemisinin (DHA) concentrations in 32 Papua New Guinean children with a mean age of 39 months with suspected or proven severe falciparum malaria who underwent a single lumbar puncture after intramuscular artemether administration. CSF artemether concentrations were 0 to 43.5 μg/liter and CSF concentration/plasma concentration ratios were 0 to 38.1%. DHA was measurable in CSF in only two children. The seven children with meningeal inflammation (CSF white cell count > 20/mm(3)) had higher CSF artemether concentration/plasma artemether concentration ratios than those without (median, 6.7% [interquartile ratio, 2.5 to 27.8%]% versus 0.0% [interquartile ratio, 0.0 to 2.5%]; P = 0.002). Meningeal inflammation was associated with a 4.6-fold increase in the CSF artemether concentration/plasma artemether concentration ratio in a population pharmacokinetic model. These data suggest that pharmacovigilance should be heightened when intramuscular artemether is given to severely ill children with evidence of meningeal inflammation.
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Abstract
SUMMARYPlasmodium falciparum has for some time been developing resistance against known anti-malarial drugs, and therefore a new drug is urgently needed. Selenium (Se), an essential trace element, in the form of inorganic Se, selenite (SeO32−), has been reported to have an anti-plasmodial effect, but its mechanism is still unclear. In the present study, we evaluated the anti-plasmodial effect of several Se compounds against P. falciparum in vitro. The anti-plasmodial effect of several Se compounds was analysed and their apoptosis-inducing activity was evaluated by morphological observation, DNA fragmentation assay and mitochondrial function analysis. SeO32−, methylseleninic acid, selenomethionine and selenocystine have anti-plasmodial effects with 50% inhibition concentration at 9, 10, 45, and 65 μm, respectively, while selenate and methylselenocysteine up to 100 μm have no effect on parasite growth. The effective Se compounds caused the parasites to become shrunken and pyknotic and significantly increased mitochondrial damage against P. falciparum compared to the untreated control. In conclusion, SeO32−, methylseleninic acid, selenomethionine and selenocystine have anti-plasmodial activities that induce apoptosis-like cell death in P. falciparum, and the anti-plasmodial effects of Se seem to be based on its chemical forms. The apoptosis-like cell-death mechanism in P. falciparum can be beneficial to respond to the growing problem of drug resistance.
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Clark RL, Brannen KC, Sanders JE, Hoberman AM. Artesunate and artelinic acid: association of embryotoxicity, reticulocytopenia, and delayed stimulation of hematopoiesis in pregnant rats. ACTA ACUST UNITED AC 2011; 92:52-68. [PMID: 21312322 DOI: 10.1002/bdrb.20282] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The artemisinin antimalarials cause embryo death and malformations in animals by killing embryonic erythroblasts. Groups of pregnant rats (N = 4) were administered 35 and 48 µmol/kg artesunate and 17.2, 28.7, 48, 96, and 191 µmol/kg artelinic acid as a single oral dose on gestational day (GD) 12. Litters were examined on GD21. The ED(50) for embryo death with artelinic acid (23.4 µmol/kg) was just slightly lower than that for decreased reticulocyte count at 24 hr postdose (33.5 µmol/kg) and both had similarly steep dose responses (maximal effects of total litter loss and ∼60% decreases in reticulocyte count at 48 µmol/kg). Results with artesunate were similar. The correlation coefficient between embryo death and decreased reticulocyte count was 0.82 (p<0.01). The close relationship between embryotoxicity and reticulocytopenia is suggestive of a common mechanism-artemisinin-induced mitochondrial damage leading to cell death. At 9 days postdose, treatment with artesunate and artelinic acid also caused increases in counts of reticulocytes, lymphocytes, basophils, and monocytes (up to 3.7 ×, 1.7 ×, 4.7 ×, and 1.7 × control, respectively). This stimulation of hematopoiesis may have been mediated by the direct oxidative conversion of artesunate or artelinic acid to the artemisininyl hydroperoxide within the bone marrow cells or by an indirect increase in reactive oxygen species. The high correlation between embryotoxicity and reticulocytopenia further supports the assertion that therapeutic dosage regimens of artemisinins that cause decreases in reticulocyte count in pregnant women during the putative critical period (approximately postconception wk 3 to 9) are at risk of also causing adverse effects on the embryo.
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Affiliation(s)
- Robert L Clark
- Artemis Pharmaceutical Research, Lansdale, PA 19446, USA.
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Genomewide scan reveals amplification of mdr1 as a common denominator of resistance to mefloquine, lumefantrine, and artemisinin in Plasmodium chabaudi malaria parasites. Antimicrob Agents Chemother 2011; 55:4858-65. [PMID: 21709099 DOI: 10.1128/aac.01748-10] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Multidrug-resistant Plasmodium falciparum malaria parasites pose a threat to effective drug control, even to artemisinin-based combination therapies (ACTs). Here we used linkage group selection and Solexa whole-genome resequencing to investigate the genetic basis of resistance to component drugs of ACTs. Using the rodent malaria parasite P. chabaudi, we analyzed the uncloned progeny of a genetic backcross between the mefloquine-, lumefantrine-, and artemisinin-resistant mutant AS-15MF and a genetically distinct sensitive clone, AJ, following drug treatment. Genomewide scans of selection showed that parasites surviving each drug treatment bore a duplication of a segment of chromosome 12 (translocated to chromosome 04) present in AS-15MF. Whole-genome resequencing identified the size of the duplicated segment and its position on chromosome 4. The duplicated fragment extends for ∼393 kbp and contains over 100 genes, including mdr1, encoding the multidrug resistance P-glycoprotein homologue 1. We therefore show that resistance to chemically distinct components of ACTs is mediated by the same genetic mutation, highlighting a possible limitation of these therapies.
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Abstract
This article reviews key facts about malaria to enhance prevention work and to promote the early diagnosis, treatment, and reporting of this complex disease.
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Affiliation(s)
- Laurie B Hartjes
- School of Nursing, University of Wisconsin-Madison, Madison, Wisconsin, USA
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Muhamad P, Chaijaroenkul W, Congpuong K, Na-Bangchang K. SYBR Green I and TaqMan quantitative real-time polymerase chain reaction methods for the determination of amplification of Plasmodium falciparum multidrug resistance-1 gene (pfmdr1). J Parasitol 2011; 97:939-42. [PMID: 21554069 DOI: 10.1645/ge-2792.1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/10/2022] Open
Abstract
The pfmdr1 gene, which encodes P-glycoprotein homolog 1, has been shown to be a reliable marker of resistance for Plasmodium falciparum related to artesunate and mefloquine combination therapy. The aims of this study are to investigate the copy number of pfmdr1 in P. falciparum isolates collected from the 4 malaria-endemic areas of Thailand (Kanchanaburi, Mae Hongson, Ranong, and Tak) along the Thailand-Myanmar (Burma) border (Thai-Myanmar border) by using SYBR Green I and the standard method TaqMan real-time polymerase chain reaction (RT-PCR) and to compare the efficiency (sensitivity and specificity) of SYBR Green I with TaqMan RT-quantitative (q)PCR methods in determining pfmdr1 gene copy number. Ninety-six blood samples were collected onto filter paper from patients with uncomplicated falciparum malaria who attended malaria clinics in the Kanchanaburi (n = 45), Mae Hongson (n = 18), Ranong (n = 11), and Tak (n = 22) provinces in Thailand. Parasite genomic DNA was extracted from dried blood spots by using QIAcube™ automated sample preparation. Pfmdr1 gene copy number was determined by TaqMan (63 samples) and SYBR Green I (96 samples) real-time PCR. Seventy-one (74.0%), 14 (14.6%), 10 (10.4%), and 1 (1%) isolates carried 1, 2, 3, and 4 pfmdr1 gene copies, respectively. Forty-three of 48 (89.6%), 6 of 11 (54.5%), and 3 of 4 (75.0%) samples, respectively, showed agreement with results of 1, 2, and 3 pfmdr1 gene copies as determined by both methods. The efficiency of SYBR Green I in identifying pfmdr1 gene copy number was found to be significantly correlated with that of TaqMan. Considering its simplicity and relatively low cost, SYBR Green I RT-qPCR is therefore a promising alternative technique for the determination of pfmdr1 copy number.
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Affiliation(s)
- Poonuch Muhamad
- Thailand Center of Excellence on Discovery and Development, Thammasat University (Rangsit Campus), Paholyothin Road, Klong Luang District, Pathumtanee, Thailand
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Moneriz C, Marín-García P, García-Granados A, Bautista JM, Diez A, Puyet A. Parasitostatic effect of maslinic acid. I. Growth arrest of Plasmodium falciparum intraerythrocytic stages. Malar J 2011; 10:82. [PMID: 21477369 PMCID: PMC3087696 DOI: 10.1186/1475-2875-10-82] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/01/2011] [Accepted: 04/10/2011] [Indexed: 12/30/2022] Open
Abstract
Background Natural products have played an important role as leads for the development of new drugs against malaria. Recent studies have shown that maslinic acid (MA), a natural triterpene obtained from olive pomace, which displays multiple biological and antimicrobial activities, also exerts inhibitory effects on the development of some Apicomplexan, including Eimeria, Toxoplasma and Neospora. To ascertain if MA displays anti-malarial activity, the main objective of this study was to asses the effect of MA on Plasmodium falciparum-infected erythrocytes in vitro. Methods Synchronized P. falciparum-infected erythrocyte cultures were incubated under different conditions with MA, and compared to chloroquine and atovaquone treated cultures. The effects on parasite growth were determined by monitoring the parasitaemia and the accumulation of the different infective stages visualized in thin blood smears. Results MA inhibits the growth of P. falciparum Dd2 and 3D7 strains in infected erythrocytes in, dose-dependent manner, leading to the accumulation of immature forms at IC50 concentrations, while higher doses produced non-viable parasite cells. MA-treated infected-erythrocyte cultures were compared to those treated with chloroquine or atovaquone, showing significant differences in the pattern of accumulation of parasitic stages. Transient MA treatment at different parasite stages showed that the compound targeted intra-erythrocytic processes from early-ring to schizont stage. These results indicate that MA has a parasitostatic effect, which does not inactivate permanently P. falciparum, as the removal of the compound allowed the infection to continue Conclusions MA displays anti-malarial activity at multiple intraerythrocytic stages of the parasite and, depending on the dose and incubation time, behaves as a plasmodial parasitostatic compound. This novel parasitostatic effect appears to be unrelated to previous mechanisms proposed for current anti-malarial drugs, and may be relevant to uncover new prospective plasmodial targets and opens novel possibilities of therapies associated to host immune response.
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Affiliation(s)
- Carlos Moneriz
- Departamento de Bioquímica y Biología Molecular IV, Universidad Complutense de Madrid, Facultad de Veterinaria, E28040 Madrid, Spain
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In vivo and in vitro antimalarial properties of azithromycin-chloroquine combinations that include the resistance reversal agent amlodipine. Antimicrob Agents Chemother 2011; 55:3115-24. [PMID: 21464242 DOI: 10.1128/aac.01566-10] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Evidence of emerging Plasmodium falciparum resistance to artemisinin-based combination therapies, documented in western Cambodia, underscores the continuing need to identify new antimalarial combinations. Given recent reports of the resurgence of chloroquine-sensitive P. falciparum parasites in Malawi, after the enforced and prolonged withdrawal of this drug, and indications of a possible synergistic interaction with the macrolide azithromycin, we sought to further characterize chloroquine-azithromycin combinations for their in vitro and in vivo antimalarial properties. In vitro 96-h susceptibility testing of chloroquine-azithromycin combinations showed mostly additive interactions against freshly cultured P. falciparum field isolates obtained from Mali. Some evidence of synergy, however, was apparent at the fractional 90% inhibitory concentration level. Additional in vitro testing highlighted the resistance reversal properties of amlodipine for both chloroquine and quinine. In vivo experiments, using the Peters 4-day suppressive test in a P. yoelii mouse model, revealed up to 99.9% suppression of parasitemia following treatment with chloroquine-azithromycin plus the R enantiomer of amlodipine. This enantiomer was chosen because it does not manifest the cardiac toxicities observed with the racemic mixture. Pharmacokinetic/pharmacodynamic analyses in this rodent model and subsequent extrapolation to a 65-kg adult led to the estimation that 1.8 g daily of R-amlodipine would be required to achieve similar efficacy in humans, for whom this is likely an unsafe dose. While these data discount amlodipine as an additional partner for chloroquine-based combination therapy, our studies continue to support azithromycin as a safe and effective addition to antimalarial combination therapies.
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Fukuda MM, Klein TA, Kochel T, Quandelacy TM, Smith BL, Villinski J, Bethell D, Tyner S, Se Y, Lon C, Saunders D, Johnson J, Wagar E, Walsh D, Kasper M, Sanchez JL, Witt CJ, Cheng Q, Waters N, Shrestha SK, Pavlin JA, Lescano AG, Graf PCF, Richardson JH, Durand S, Rogers WO, Blazes DL, Russell KL. Malaria and other vector-borne infection surveillance in the U.S. Department of Defense Armed Forces Health Surveillance Center-Global Emerging Infections Surveillance program: review of 2009 accomplishments. BMC Public Health 2011; 11 Suppl 2:S9. [PMID: 21388569 PMCID: PMC3092419 DOI: 10.1186/1471-2458-11-s2-s9] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/02/2022] Open
Abstract
Vector-borne infections (VBI) are defined as infectious diseases transmitted by the bite or mechanical transfer of arthropod vectors. They constitute a significant proportion of the global infectious disease burden. United States (U.S.) Department of Defense (DoD) personnel are especially vulnerable to VBIs due to occupational contact with arthropod vectors, immunological naiveté to previously unencountered pathogens, and limited diagnostic and treatment options available in the austere and unstable environments sometimes associated with military operations. In addition to the risk uniquely encountered by military populations, other factors have driven the worldwide emergence of VBIs. Unprecedented levels of global travel, tourism and trade, and blurred lines of demarcation between zoonotic VBI reservoirs and human populations increase vector exposure. Urban growth in previously undeveloped regions and perturbations in global weather patterns also contribute to the rise of VBIs. The Armed Forces Health Surveillance Center-Global Emerging Infections Surveillance and Response System (AFHSC-GEIS) and its partners at DoD overseas laboratories form a network to better characterize the nature, emergence and growth of VBIs globally. In 2009 the network tested 19,730 specimens from 25 sites for Plasmodium species and malaria drug resistance phenotypes and nearly another 10,000 samples to determine the etiologies of non-Plasmodium species VBIs from regions spanning from Oceania to Africa, South America, and northeast, south and Southeast Asia. This review describes recent VBI-related epidemiological studies conducted by AFHSC-GEIS partner laboratories within the OCONUS DoD laboratory network emphasizing their impact on human populations.
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Affiliation(s)
- Mark M Fukuda
- Armed Forces Health Surveillance Center, 2900 Linden Lane, Silver Spring, MD 20910, USA
| | - Terry A Klein
- Force Health Protection and Preventive Medicine, 65th Medical Brigade, Unit 15281, APO AP 96205-5281 USA (Republic of Korea
| | - Tadeusz Kochel
- US Naval Medical Research Center Detachment (NMRCD), Centro Medico Naval “CMST,” Av. Venezuela CDRA 36, Callao 2, Lima, Peru
| | - Talia M Quandelacy
- Armed Forces Health Surveillance Center, 2900 Linden Lane, Silver Spring, MD 20910, USA
| | | | - Jeff Villinski
- US Army Medical Research Unit Kenya, United States Embassy, ATTN: MRU, United Nations Avenue, Post Office Box 606, Village Market, 00621 Nairobi, Kenya
| | - Delia Bethell
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - Stuart Tyner
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - Youry Se
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - Chanthap Lon
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - David Saunders
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - Jacob Johnson
- US Army Medical Research Unit Kenya, United States Embassy, ATTN: MRU, United Nations Avenue, Post Office Box 606, Village Market, 00621 Nairobi, Kenya
| | - Eric Wagar
- US Naval Medical Research Unit Number 3, Extension of Ramses Street, Adjacent to Abbassia Fever Hospital, Postal Code 11517, Cairo, Egypt
| | - Douglas Walsh
- US Naval Medical Research Unit Number 3, Extension of Ramses Street, Adjacent to Abbassia Fever Hospital, Postal Code 11517, Cairo, Egypt
| | - Matthew Kasper
- US Navy Medical Research Unit-2, U.S. Embassy Unit 8166 Box P, APO AP 96546, Phnom Penh, Cambodia
| | - Jose L Sanchez
- Armed Forces Health Surveillance Center, 2900 Linden Lane, Silver Spring, MD 20910, USA
| | - Clara J Witt
- Armed Forces Health Surveillance Center, 2900 Linden Lane, Silver Spring, MD 20910, USA
| | - Qin Cheng
- Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks, Enoggera, QLD 4051 Australia
| | - Norman Waters
- Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks, Enoggera, QLD 4051 Australia
| | - Sanjaya K Shrestha
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - Julie A Pavlin
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - Andres G Lescano
- US Naval Medical Research Center Detachment (NMRCD), Centro Medico Naval “CMST,” Av. Venezuela CDRA 36, Callao 2, Lima, Peru
| | - Paul CF Graf
- US Naval Medical Research Center Detachment (NMRCD), Centro Medico Naval “CMST,” Av. Venezuela CDRA 36, Callao 2, Lima, Peru
| | - Jason H Richardson
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
| | - Salomon Durand
- US Naval Medical Research Center Detachment (NMRCD), Centro Medico Naval “CMST,” Av. Venezuela CDRA 36, Callao 2, Lima, Peru
| | - William O Rogers
- US Navy Medical Research Unit-2, U.S. Embassy Unit 8166 Box P, APO AP 96546, Phnom Penh, Cambodia
| | - David L Blazes
- Armed Forces Health Surveillance Center, 2900 Linden Lane, Silver Spring, MD 20910, USA
| | - Kevin L Russell
- Armed Forces Health Surveillance Center, 2900 Linden Lane, Silver Spring, MD 20910, USA
| | - the AFHSC-GEIS Malaria and Vector Borne Infections Writing Group
- Armed Forces Health Surveillance Center, 2900 Linden Lane, Silver Spring, MD 20910, USA
- US Army Medical Component Armed Forces Research Institute of the Medical Sciences, APO AP 96546, Bangkok, Thailand
- US Army Medical Research Unit Kenya, United States Embassy, ATTN: MRU, United Nations Avenue, Post Office Box 606, Village Market, 00621 Nairobi, Kenya
- US Naval Medical Research Unit Number 3, Extension of Ramses Street, Adjacent to Abbassia Fever Hospital, Postal Code 11517, Cairo, Egypt
- US Navy Medical Research Unit-2, U.S. Embassy Unit 8166 Box P, APO AP 96546, Phnom Penh, Cambodia
- Australian Army Malaria Institute, Weary Dunlop Drive, Gallipoli Barracks, Enoggera, QLD 4051 Australia
- Naval Medical Research Center, 503 Robert Grant Ave. Silver Spring, MD 20910, USA
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Chaijaroenkul W, Ward SA, Mungthin M, Johnson D, Owen A, Bray PG, Na-Bangchang K. Sequence and gene expression of chloroquine resistance transporter (pfcrt) in the association of in vitro drugs resistance of Plasmodium falciparum. Malar J 2011; 10:42. [PMID: 21320353 PMCID: PMC3055224 DOI: 10.1186/1475-2875-10-42] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2010] [Accepted: 02/15/2011] [Indexed: 11/10/2022] Open
Abstract
Background Plasmodium falciparum chloroquine resistance (CQR) transporter protein (PfCRT) is known to be the important key of CQR. Recent studies have definitively demonstrated a link between mutations in the gene pfcrt and resistance to chloroquine in P. falciparum. Although these mutations are predictive of chloroquine resistance, they are not quantitatively predictive of the degree of resistance. Methods In this study, a total of 95 recently adapted P. falciparum isolates from Thailand were included in the analysis. Parasites were characterized for their drug susceptibility phenotypes and genotypes with respect to pfcrt. From the original 95 isolates, 20 were selected for complete pfcrt sequence analysis. Results Almost all of the parasites characterized carried the previously reported mutations K76T, A220S, Q271E, N326S, I356T and R371I. On complete sequencing, isolates were identified with novel mutations at K76A and E198K. There was a suggestion that parasites carrying E198K were less resistant than those that did not. In addition, pfcrt and pfmdr1 gene expression were investigated by real-time PCR. No relationship between the expression level of either of these genes and response to drug was observed. Conclusion Data from the present study suggest that other genes must contribute to the degree of resistance once the resistance phenotype is established through mutations in pfcrt.
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Affiliation(s)
- Wanna Chaijaroenkul
- Faculty of Allied Health Sciences, Thammasat University, Rangsit, Patumthani 12120, Thailand
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Mahajan SS, Deu E, Lauterwasser EMW, Leyva MJ, Ellman JA, Bogyo M, Renslo AR. A fragmenting hybrid approach for targeted delivery of multiple therapeutic agents to the malaria parasite. ChemMedChem 2011; 6:415-9. [PMID: 21360816 PMCID: PMC3265971 DOI: 10.1002/cmdc.201100002] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/12/2010] [Indexed: 11/16/2022]
Affiliation(s)
- Sumit S Mahajan
- Department of Pharmaceutical Chemistry, Small Molecule Discovery Center, University of California, San Francisco, Mission Bay Campus, 1700 4th Street, San Francisco, CA 94158, USA
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Deu E, Leyva MJ, Albrow VE, Rice MJ, Ellman JA, Bogyo M. Functional studies of Plasmodium falciparum dipeptidyl aminopeptidase I using small molecule inhibitors and active site probes. ACTA ACUST UNITED AC 2011; 17:808-19. [PMID: 20797610 DOI: 10.1016/j.chembiol.2010.06.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/06/2010] [Revised: 06/20/2010] [Accepted: 06/25/2010] [Indexed: 11/26/2022]
Abstract
The widespread resistance of malaria parasites to all affordable drugs has made the identification of new targets urgent. Dipeptidyl aminopeptidases (DPAPs) represent potentially valuable new targets that are involved in hemoglobin degradation (DPAP1) and parasite egress (DPAP3). Here we use activity-based probes to demonstrate that specific inhibition of DPAP1 by a small molecule results in the formation of an immature trophozoite that leads to parasite death. Using computational methods, we designed stable, nonpeptidic covalent inhibitors that kill Plasmodium falciparum at low nanomolar concentrations. These compounds show signs of slowing parasite growth in a murine model of malaria, which suggests that DPAP1 might be a viable antimalarial target. Interestingly, we found that resynthesis and activation of DPAP1 after inhibition is rapid, suggesting that effective drugs would need to sustain DPAP1 inhibition for a period of 2-3 hr.
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Affiliation(s)
- Edgar Deu
- Department of Pathology, Stanford School of Medicine, 300 Pasteur Drive, Stanford, CA 94305, USA
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Pascual A, Basco LK, Baret E, Amalvict R, Travers D, Rogier C, Pradines B. Use of the atmospheric generators for capnophilic bacteria Genbag-CO2 for the evaluation of in vitro Plasmodium falciparum susceptibility to standard anti-malarial drugs. Malar J 2011; 10:8. [PMID: 21235757 PMCID: PMC3031278 DOI: 10.1186/1475-2875-10-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/12/2010] [Accepted: 01/14/2011] [Indexed: 01/08/2023] Open
Abstract
Background The aim of this study was to evaluate the cultivation system in which the proper atmospheric conditions for growing Plasmodium falciparum parasites were maintained in a sealed bag. The Genbag® system associated with the atmospheric generators for capnophilic bacteria Genbag CO2® was used for in vitro susceptibility test of nine standard anti-malarial drugs and compared to standard incubator conditions. Methods The susceptibility of 36 pre-identified parasite strains from a wide panel of countries was assessed for nine standard anti-malarial drugs (chloroquine, quinine, mefloquine, monodesethylamodiaquine, lumefantrine, dihydroartemisinin, atovaquone and pyrimethamine) by the standard 42-hour 3H-hypoxanthine uptake inhibition method using the Genbag CO2® system and compared to controlled incubator conditions (5% CO2 and 10% O2). Results The counts per minute values in the control wells in incubator atmospheric conditions (5% CO2 and 10% O2) were significantly higher than those of Genbag® conditions (2738 cpm vs 2282 cpm, p < 0.0001). The geometric mean IC50 estimated under the incubator atmospheric conditions was significantly lower for atovaquone (1.2 vs 2.1 nM, p = 0.0011) and higher for the quinolines: chloroquine (127 vs 94 nM, p < 0.0001), quinine (580 vs 439 nM, p < 0.0001), monodesethylamodiaquine (41.4 vs 31.8 nM, p < 0.0001), mefloquine (57.5 vs 49.7 nM, p = 0.0011) and lumefantrine (23.8 vs 21.2 nM, p = 0.0044). There was no significant difference of IC50 between the 2 conditions for dihydroartemisinin, doxycycline and pyrimethamine. To reduce this difference in term of anti-malarial susceptibility, a specific cut-off was estimated for each drug under Genbag® conditions by regression. The cut-off was estimated at 77 nM for chloroquine (vs 100 nM in 10% O2), 611 nM for quinine (vs 800 nM), 30 nM for mefloquine (vs 30 nM), 61 nM for monodesethylamodiaquine (vs 80 nM) and 1729 nM for pyrimethamine (vs 2000 nM). Conclusions The atmospheric generators for capnophilic bacteria Genbag CO2® is an appropriate technology that can be transferred to the field for epidemiological surveys of drug-resistant malaria. The present data suggest the importance of the gas mixture on in vitro microtest results for anti-malarial drugs and the importance of determining the microtest conditions before comparing and analysing the data from different laboratories and concluding on malaria resistance.
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Affiliation(s)
- Aurélie Pascual
- Unité de Recherche en Biologie et Epidémiologie Parasitaires, Institut de Recherche Biomédicale des Armées--antenne de Marseille, Marseille, France
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Toure OA, Kouame MG, Didier YJ, Berenger AAA, Djerea K, Genevieve GO, Penali LK. Artesunate/mefloquine paediatric formulation vs. artemether/lumefantrine for the treatment of uncomplicated Plasmodium falciparum in Anonkoua kouté, Côte d'Ivoire. Trop Med Int Health 2011; 16:290-7. [PMID: 21214690 DOI: 10.1111/j.1365-3156.2010.02701.x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVES To test the hypothesis that Artesunate-mefloquine paediatric (AS+MEF) is as effective as Artemether-lumefantrine (AL) in treating acute uncomplicated malaria in children. METHODS In an open label, randomized controlled clinical trial, children aged 6-59 months were randomized to receive AS+MEF or AL. Both drug regimens were given for 3 days, and follow-up was for 28 days. The primary endpoint was the 28-day cure rate and was defined as proportion of patients with PCR-corrected cure rate after 28 days of follow-up. RESULTS One hundred and fifty-six patients with confirmed uncomplicated P. falciparum malaria were randomly assigned to receive AS+MEF (n = 77) or AL (n = 79). PCR-corrected day 28 cure rates for per protocol (PP) populations were 99% for AS+MEF and 97% (P = 1) for AL. For the intention to treat (ITT) population, cure rates were 96% for AS+MEF and 92% (P = 0.49) for AL. Both regimens were well tolerated. CONCLUSION AS+MEF is as effective as AL, and both combinations were efficacious and safe.
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Pradines B, Briolant S, Henry M, Oeuvray C, Baret E, Amalvict R, Didillon E, Rogier C. Absence of association between pyronaridine in vitro responses and polymorphisms in genes involved in quinoline resistance in Plasmodium falciparum. Malar J 2010; 9:339. [PMID: 21108786 PMCID: PMC3224917 DOI: 10.1186/1475-2875-9-339] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/09/2010] [Accepted: 11/25/2010] [Indexed: 11/15/2022] Open
Abstract
Background The aim of the present work was to assess the in vitro cross-resistance of pyronaridine with other quinoline drugs, artesunate and several other commonly used anti-malarials and to evaluate whether decreased susceptibility to pyronaridine could be associated with genetic polymorphisms in genes involved in reduced quinoline susceptibility, such as pfcrt, pfmdr1, pfmrp and pfnhe. Methods The in vitro chemosusceptibility profiles of 23 strains of Plasmodium falciparum were analysed by the standard 42-hour 3H-hypoxanthine uptake inhibition method for pyronaridine, artesunate, chloroquine, monodesethylamodiaquine, quinine, mefloquine, lumefantrine, atovaquone, pyrimethamine and doxycycline. Genotypes were assessed for pfcrt, pfmdr1, pfnhe-1 and pfmrp genes. Results The IC50 values for pyronaridine ranged from 15 to 49 nM (geometric mean = 23.1 nM). A significant positive correlation was found between responses to pyronaridine and responses to artesunate (r2 = 0.20; P = 0.0317) but too low to suggest cross-resistance. No significant correlation was found between pyronaridine IC50 and responses to other anti-malarials. Significant associations were not found between pyronaridine IC50 and polymorphisms in pfcrt, pfmdr1, pfmrp or pfnhe-1. Conclusion There was an absence of cross-resistance between pyronaridine and quinolines, and the IC50 values for pyronaridine were found to be unrelated to mutations in the transport protein genes pfcrt, pfmdr1, pfmrp or pfnhe-1, known to be involved in quinoline resistance. These results confirm the interest and the efficacy of the use of a combination of pyronaridine and artesunate in areas in which parasites are resistant to quinolines.
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Affiliation(s)
- Bruno Pradines
- Unité de Recherche en Biologie et Epidémiologie Parasitaires, UMR 6236, Institut de Recherche Biomédicale des Armées - antenne de Marseille, Marseille, France.
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Antao T, Hastings IM. Environmental, pharmacological and genetic influences on the spread of drug-resistant malaria. Proc Biol Sci 2010; 278:1705-12. [PMID: 21084349 DOI: 10.1098/rspb.2010.1907] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
Plasmodium falciparum malaria is subject to artificial selection from antimalarial drugs that select for drug-resistant parasites. We describe and apply a flexible new approach to investigate how epistasis, inbreeding, selection heterogeneity and multiple simultaneous drug deployments interact to influence the spread of drug-resistant malaria. This framework recognizes that different human 'environments' within which treatment may occur (such as semi- and non-immune humans taking full or partial drug courses) influence the genetic interactions between parasite loci involved in resistance. Our model provides an explanation for how the rate of spread varies according to different malaria transmission intensities, why resistance might stabilize at intermediate frequencies and also identifies several factors that influence the decline of resistance after a drug is removed. Results suggest that studies based on clinical outcomes might overestimate the spread of resistant parasites, especially in high-transmission areas. We show that when transmission decreases, prevalence might decrease without a corresponding change in frequency of resistance and that this relationship is heavily influenced by the extent of linkage disequilibrium between loci. This has important consequences on the interpretation of data from areas where control is being successful and suggests that reducing transmission might have less impact on the spread of resistance than previously expected.
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Affiliation(s)
- Tiago Antao
- Liverpool School of Tropical Medicine, Liverpool L3 5QA, UK.
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Exposing malaria in-host diversity and estimating population diversity by capture-recapture using massively parallel pyrosequencing. Proc Natl Acad Sci U S A 2010; 107:20138-43. [PMID: 21041629 DOI: 10.1073/pnas.1007068107] [Citation(s) in RCA: 98] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Malaria infections commonly contain multiple genetically distinct variants. Mathematical and animal models suggest that interactions among these variants have a profound impact on the emergence of drug resistance. However, methods currently used for quantifying parasite diversity in individual infections are insensitive to low-abundance variants and are not quantitative for variant population sizes. To more completely describe the in-host complexity and ecology of malaria infections, we used massively parallel pyrosequencing to characterize malaria parasite diversity in the infections of a group of patients. By individually sequencing single strands of DNA in a complex mixture, this technique can quantify uncommon variants in mixed infections. The in-host diversity revealed by this method far exceeded that described by currently recommended genotyping methods, with as many as sixfold more variants per infection. In addition, in paired pre- and posttreatment samples, we show a complex milieu of parasites, including variants likely up-selected and down-selected by drug therapy. As with all surveys of diversity, sampling limitations prevent full discovery and differences in sampling effort can confound comparisons among samples, hosts, and populations. Here, we used ecological approaches of species accumulation curves and capture-recapture to estimate the number of variants we failed to detect in the population, and show that these methods enable comparisons of diversity before and after treatment, as well as between malaria populations. The combination of ecological statistics and massively parallel pyrosequencing provides a powerful tool for studying the evolution of drug resistance and the in-host ecology of malaria infections.
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Baird JK, Surjadjaja C. Consideration of ethics in primaquine therapy against malaria transmission. Trends Parasitol 2010; 27:11-6. [PMID: 20846906 DOI: 10.1016/j.pt.2010.08.005] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/15/2010] [Revised: 08/23/2010] [Accepted: 08/23/2010] [Indexed: 10/19/2022]
Abstract
Millions of people receive primaquine against sexual plasmodia responsible for malaria transmission. These gametocytes cause no symptoms and do not threaten the host, but they infect mosquitoes and threaten the community. Primaquine causes hemolysis in the small minority of patients with glucose-6-phosphate dehydrogenase deficiency (G6PDd). Clinical studies in the 1950s demonstrated gametocytocidal primaquine to be safe without G6PDd screening. However, the evaluated G6PDd variant, African A-, represents mild sensitivity to primaquine. The view of primaquine as a safe gametocytocide thus rests largely upon observations from a G6PDd variant that is unlikely to challenge safety. The early clinical work does not seem to afford an adequate assessment of safety in G6PDd patients. Potential risk of harm without clinical benefit to the patient raises ethical questions that should be examined.
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Affiliation(s)
- J Kevin Baird
- Eijkman-Oxford Clinical Research Unit, Jakarta, Indonesia.
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Hunt P, Martinelli A, Modrzynska K, Borges S, Creasey A, Rodrigues L, Beraldi D, Loewe L, Fawcett R, Kumar S, Thomson M, Trivedi U, Otto TD, Pain A, Blaxter M, Cravo P. Experimental evolution, genetic analysis and genome re-sequencing reveal the mutation conferring artemisinin resistance in an isogenic lineage of malaria parasites. BMC Genomics 2010; 11:499. [PMID: 20846421 PMCID: PMC2996995 DOI: 10.1186/1471-2164-11-499] [Citation(s) in RCA: 64] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2010] [Accepted: 09/16/2010] [Indexed: 11/10/2022] Open
Abstract
Background Classical and quantitative linkage analyses of genetic crosses have traditionally been used to map genes of interest, such as those conferring chloroquine or quinine resistance in malaria parasites. Next-generation sequencing technologies now present the possibility of determining genome-wide genetic variation at single base-pair resolution. Here, we combine in vivo experimental evolution, a rapid genetic strategy and whole genome re-sequencing to identify the precise genetic basis of artemisinin resistance in a lineage of the rodent malaria parasite, Plasmodium chabaudi. Such genetic markers will further the investigation of resistance and its control in natural infections of the human malaria, P. falciparum. Results A lineage of isogenic in vivo drug-selected mutant P. chabaudi parasites was investigated. By measuring the artemisinin responses of these clones, the appearance of an in vivo artemisinin resistance phenotype within the lineage was defined. The underlying genetic locus was mapped to a region of chromosome 2 by Linkage Group Selection in two different genetic crosses. Whole-genome deep coverage short-read re-sequencing (Illumina® Solexa) defined the point mutations, insertions, deletions and copy-number variations arising in the lineage. Eight point mutations arise within the mutant lineage, only one of which appears on chromosome 2. This missense mutation arises contemporaneously with artemisinin resistance and maps to a gene encoding a de-ubiquitinating enzyme. Conclusions This integrated approach facilitates the rapid identification of mutations conferring selectable phenotypes, without prior knowledge of biological and molecular mechanisms. For malaria, this model can identify candidate genes before resistant parasites are commonly observed in natural human malaria populations.
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Affiliation(s)
- Paul Hunt
- Institute for Immunology and Infection Research, School of Biological Sciences, University of Edinburgh, Edinburgh, UK.
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Rodrigues LA, Henriques G, Borges ST, Hunt P, Sanchez CP, Martinelli A, Cravo P. Experimental evolution of resistance to artemisinin combination therapy results in amplification of the mdr1 gene in a rodent malaria parasite. PLoS One 2010; 5:e11593. [PMID: 20657645 PMCID: PMC2904698 DOI: 10.1371/journal.pone.0011593] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2010] [Accepted: 06/18/2010] [Indexed: 11/18/2022] Open
Abstract
Background Lacking suitable alternatives, the control of malaria increasingly depends upon Artemisinin Combination Treatments (ACT): resistance to these drugs would therefore be disastrous. For ACTs, the biology of resistance to the individual components has been investigated, but experimentally induced resistance to component drugs in combination has not been generated. Methodology/Principal Findings We have used the rodent malaria parasite Plasmodium chabaudi to select in vivo resistance to the artesunate (ATN) + mefloquine (MF) version of ACT, through prolonged exposure of parasites to both drugs over many generations. The selection procedure was carried out over twenty-seven consecutive sub-inoculations under increasing ATN + MF doses, after which a genetically stable resistant parasite, AS-ATNMF1, was cloned. AS-ATNMF1 showed increased resistance to ATN + MF treatment and to artesunate or mefloquine administered separately. Investigation of candidate genes revealed an mdr1 duplication in the resistant parasites and increased levels of mdr1 transcripts and protein. There were no point mutations in the atpase6 or ubp1genes. Conclusion Resistance to ACTs may evolve even when the two drugs within the combination are taken simultaneously and amplification of the mdr1 gene may contribute to this phenotype. However, we propose that other gene(s), as yet unidentified, are likely to be involved.
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Affiliation(s)
- Louise A. Rodrigues
- UEI Biologia Molecular, UEI Malária, Centro de Malária e Outras Doenças Tropicais/IHMT/UNL, Lisbon, Portugal
| | - Gisela Henriques
- UEI Biologia Molecular, UEI Malária, Centro de Malária e Outras Doenças Tropicais/IHMT/UNL, Lisbon, Portugal
| | - Sofia T. Borges
- UEI Biologia Molecular, UEI Malária, Centro de Malária e Outras Doenças Tropicais/IHMT/UNL, Lisbon, Portugal
| | - Paul Hunt
- Centre for Immunity, Infection and Evolution, School of Biological Science, The University of Edinburgh, Edinburgh, United Kingdom
| | - Cecília P. Sanchez
- Abteilung Parasitologie, Hygiene Institut, Universitätsklinikum Heidelberg, Heidelberg, Germany
| | - Axel Martinelli
- UEI Biologia Molecular, UEI Malária, Centro de Malária e Outras Doenças Tropicais/IHMT/UNL, Lisbon, Portugal
| | - Pedro Cravo
- UEI Biologia Molecular, UEI Malária, Centro de Malária e Outras Doenças Tropicais/IHMT/UNL, Lisbon, Portugal
- * E-mail:
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Absence of association between piperaquine in vitro responses and polymorphisms in the pfcrt, pfmdr1, pfmrp, and pfnhe genes in Plasmodium falciparum. Antimicrob Agents Chemother 2010; 54:3537-44. [PMID: 20547801 DOI: 10.1128/aac.00183-10] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/03/2023] Open
Abstract
We have analyzed the profiles of 23 of Plasmodium falciparum strains for their in vitro chemosusceptibilities to piperaquine (PPQ), dihydroartemisinin (DHA), chloroquine, monodesethylamodiaquine, quinine, mefloquine, lumefantrine, atovaquone, pyrimethamine, and doxycycline (DOX) in association with polymorphisms in genes involved in quinoline resistance (Plasmodium falciparum crt [pfcrt], pfmdr1, pfmrp, and pfnhe). The 50% inhibitory concentrations (IC(50)s) for PPQ ranged from 29 to 98 nM (geometric mean = 57.8 nM, 95% confidence interval [CI] = 51 to 65) and from 0.4 to 5.8 nM for DHA (geometric mean = 1.8 nM, 95% CI = 1.4 to 2.3). We found a significant positive correlation between the responses to PPQ and DHA (r(2) = 0.17; P = 0.0495) and between the responses to PPQ and DOX (r(2) = 0.41; P = 0.001). We did not find a significant association between the PPQ IC(50) (0.0525 < P < 0.9247) or the DHA IC(50) (0.0138 < P < 0.9018) and polymorphisms in the pfcrt, pfmdr1, pfmrp, and pfnhe-1 genes. There was an absence of cross-resistance with quinolines, and the IC(50)s for PPQ and DHA were found to be unrelated to mutations in the pfcrt, pfmdr1, pfmrp, and pfnhe-1 transport protein genes, which are involved in quinoline antimalarial drug resistance. These results confirm the interest in and the efficacy of the combination of PPQ and DHA for areas in which parasites are resistant to chloroquine or other quinolines.
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Douglas NM, Anstey NM, Angus BJ, Nosten F, Price RN. Artemisinin combination therapy for vivax malaria. THE LANCET. INFECTIOUS DISEASES 2010; 10:405-16. [PMID: 20510281 PMCID: PMC3350863 DOI: 10.1016/s1473-3099(10)70079-7] [Citation(s) in RCA: 170] [Impact Index Per Article: 12.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/04/2023]
Abstract
Early parasitological diagnosis and treatment with artemisinin-based combination therapies (ACTs) are key components of worldwide malaria elimination programmes. In general, use of ACTs has been limited to patients with falciparum malaria whereas blood-stage infections with Plasmodium vivax are mostly still treated with chloroquine. We review the evidence for the relative benefits and disadvantages of the existing separate treatment approach versus a unified ACT-based strategy for treating Plasmodium falciparum and P vivax infections in regions where both species are endemic (co-endemic). The separate treatment scenario is justifiable if P vivax remains sensitive to chloroquine and diagnostic tests reliably distinguish P vivax from P falciparum. However, with the high number of misdiagnoses in routine practice and the rise and spread of chloroquine-resistant P vivax, there might be a compelling rationale for a unified ACT-based strategy for vivax and falciparum malaria in all co-endemic regions. Analyses of the cost-effectiveness of ACTs for both Plasmodium species are needed to assess the role of these drugs in the control and elimination of vivax malaria.
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Wurtz N, Briolant S, Gil M, Parquet V, Henry M, Baret E, Amalvict R, Almeras L, Rogier C, Pradines B. Synergy of mefloquine activity with atorvastatin, but not chloroquine and monodesethylamodiaquine, and association with the pfmdr1 gene. J Antimicrob Chemother 2010; 65:1387-94. [PMID: 20501488 DOI: 10.1093/jac/dkq173] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
Abstract
OBJECTIVES The aim of the study was to assess the in vitro potentiating effects of atorvastatin, a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, in combination with mefloquine, chloroquine or monodesethylamodiaquine against Plasmodium falciparum and to evaluate whether the effects of atorvastatin could be associated with mutations or gene copy number in multidrug resistance (MDR)-like protein genes. METHODS The susceptibilities of 21 parasite strains to combinations of atorvastatin with mefloquine, chloroquine or monodesethylamodiaquine were assessed using the in vitro isotopic microtest. Genotypes and gene copy number were assessed for pfmdr1, pfmdr2 and pfmrp genes. RESULTS Atorvastatin demonstrated synergistic effects in combination with mefloquine. The mefloquine IC(50) (50% inhibitory concentration) was reduced by 7%, 24% and 37% in the presence of atorvastatin at concentrations of 0.1, 0.5 and 1.0 microM, respectively. The synergistic effect of atorvastatin on the response to mefloquine was significantly associated with pfmdr1 copy number. The concentration of atorvastatin that could reduce the IC(50) of mefloquine by 50% was 2.4 +/- 1.3 microM for the 12 strains that contained one copy of pfmdr1 and 5.8 +/- 2.1 microM for the 9 strains that contained two copies or more. The synergistic effect of atorvastatin in combination with mefloquine was found to be significantly unrelated to mutations in pfmdr1, pfmdr2 or pfmrp genes. CONCLUSIONS The synergy of the effect of mefloquine at concentrations relevant to its achievable plasma concentrations in patients taking 80 mg of atorvastatin daily suggests that atorvastatin will be a good candidate in combination with mefloquine for malaria treatment.
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Affiliation(s)
- Nathalie Wurtz
- Unité de Recherche en Physiologie et Pharmacocinétique Parasitaires - UMR-MD3 Relations Hôte-Parasites - Pharmacologie et Thérapeutique, Institut de Recherche Biomédicale des Armées, antenne de Marseille, Marseille, France
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Parquet V, Henry M, Wurtz N, Dormoi J, Briolant S, Gil M, Baret E, Amalvict R, Rogier C, Pradines B. Atorvastatin as a potential anti-malarial drug: in vitro synergy in combinational therapy with quinine against Plasmodium falciparum. Malar J 2010; 9:139. [PMID: 20497586 PMCID: PMC2882376 DOI: 10.1186/1475-2875-9-139] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2010] [Accepted: 05/25/2010] [Indexed: 12/24/2022] Open
Abstract
Background Quinine (QN) remains the first line anti-malarial drug for the treatment of complicated malaria in Europe and Africa. The emergence of QN resistance has been documented. QN resistance is not yet a significant problem, but there is an urgent need to discover partners for use in combination with QN. The aim of the study was to assess the in vitro potentiating effects of atorvastatin (AVA), a 3-hydroxy-3-methylglutaryl coenzyme A (HMG-CoA) reductase inhibitor, in combination with QN against Plasmodium falciparum and to evaluate whether the effects of AVA could be associated with gene copy number or mutations in genes involved in QN resistance, such as pfcrt, pfmdr1, pfmrp and pfnhe. Methods The susceptibilities to combination of AVA with QN were assessed against 21 parasite strains using the in vitro isotopic microtest. Genotypes and gene copy number were assessed for pfcrt, pfmdr1, pfmdr2, pfmrp genes. In addition, the number of DNNND, DDNHNDNHNN repeats in pfnhe-1 ms4760 and the ms4760 profile were determined for each strains of P. falciparum. Results AVA demonstrated synergistic effects in combination with QN against 21 P. falciparum strains. The QN IC50 was reduced by 5% (0% to 15%; 95%CI: 1%-8%), 10% (3% to 23%; 95%CI: 7%-14%) and 22% (14% to 40%; 95%CI: 19%-25%) in presence of AVA at concentrations of 0.1, 0.5 and 1.0 μM, respectively. These reductions were all significant (p < 0.009). The reduction in the QN IC50 in presence of AVA was not significantly correlated with the QN IC50 (r = 0.22, P = 0.3288) or the AVA IC50 (r = 0.03, P = 0.8946). The synergistic effect of AVA in combination with QN was not significantly associated with polymorphisms in the pfcrt, pfmdr1, pfmrp, and pfnhe-1 genes that could be involved in QN resistance. The synergistic effect of AVA on QN responses was not significantly associated with pfmdr1 copy number (P = 0.0428). Conclusion The synergistic effect of AVA in combination with QN was found to be unrelated to mutations occurring in transport protein genes involved in QN drug resistance. The different mechanisms of drug uptake and/or mode of action for AVA compared to the other anti-malarial drugs, as well as the AVA-mediated synergy of the anti-malarial effect of QN, suggests that AVA will be a good candidate for combinatorial malaria treatment. All of these observations support calls for both an in vivo evaluation with pharmacokinetic component and clinical trials of AVA as an anti-malarial therapy.
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Affiliation(s)
- Véronique Parquet
- Unité de Recherche en Biologie et Epidémiologie Parasitaires - Unité de Recherche pour les Maladies Infectieuses et Tropicales Emergentes - UMR 6236, Institut de Médecine Tropicale du Service de Santé des Armées, Marseille, France
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Vinayak S, Alam MT, Sem R, Shah NK, Susanti AI, Lim P, Muth S, Maguire JD, Rogers WO, Fandeur T, Barnwell JW, Escalante AA, Wongsrichanalai C, Ariey F, Meshnick SR, Udhayakumar V. Multiple genetic backgrounds of the amplified Plasmodium falciparum multidrug resistance (pfmdr1) gene and selective sweep of 184F mutation in Cambodia. J Infect Dis 2010; 201:1551-60. [PMID: 20367478 DOI: 10.1086/651949] [Citation(s) in RCA: 48] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022] Open
Abstract
BACKGROUND The emergence of artesunate-mefloquine (AS+MQ)-resistant Plasmodium falciparum in the Thailand-Cambodia region is a major concern for malaria control. Studies indicate that copy number increase and key alleles in the pfmdr1 gene are associated with AS+MQ resistance. In the present study, we investigated evidence for a selective sweep around pfmdr1 because of the spread of adaptive mutation and/or multiple copies of this gene in the P. falciparum population in Cambodia. METHODS We characterized 13 microsatellite loci flanking (+/-99 kb) pfmdr1 in 93 single-clone P. falciparum infections, of which 31 had multiple copies and 62 had a single copy of the pfmdr1 gene. RESULTS Genetic analysis revealed no difference in the mean (+/- standard deviation) expected heterozygosity (H(e)) at loci around single (0.75+/-0.03) and multiple (0.76+/-0.04) copies of pfmdr1. Evidence of genetic hitchhiking with the selective sweep of certain haplotypes was seen around mutant (184F) pfmdr1 allele, irrespective of the copy number. There was an overall reduction of 28% in mean H(e) (+/-SD) around mutant allele (0.56+/-0.05), compared with wild-type allele (0.84+/-0.02). Significant linkage disequilibrium was also observed between the loci flanking mutant pfmdr1 allele. CONCLUSION The 184F mutant allele is under selection, whereas amplification of pfmdr1 gene in this population occurs on multiple genetic backgrounds.
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Affiliation(s)
- Sumiti Vinayak
- Atlanta Research and Education Foundation, Atlanta, Georgia, USA
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Ndiaye D, Patel V, Demas A, LeRoux M, Ndir O, Mboup S, Clardy J, Lakshmanan V, Daily JP, Wirth DF. A non-radioactive DAPI-based high-throughput in vitro assay to assess Plasmodium falciparum responsiveness to antimalarials--increased sensitivity of P. falciparum to chloroquine in Senegal. Am J Trop Med Hyg 2010; 82:228-30. [PMID: 20133997 DOI: 10.4269/ajtmh.2010.09-0470] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The spread of Plasmodium falciparum drug resistance is outpacing new antimalarial development and compromising effective malaria treatment. Combination therapy is widely implemented to prolong the effectiveness of currently approved antimalarials. To maximize utility of available drugs, periodic monitoring of drug efficacy and gathering of accurate information regarding parasite-sensitivity changes are essential. We describe a high-throughput, non-radioactive, field-based assay to evaluate in vitro antimalarial drug sensitivity of P. falciparum isolates from 40 Senegalese patients. Compared with earlier years, we found a significant decrease in chloroquine in vitro and in genotypic resistances (> 50% and > 65%, respectively, in previous studies) with only 23% of isolates showing resistance. This is possibly caused by a withdrawal of chloroquine from Senegal in 2002. We also found a range of artemisinin responses. Prevalence of drug resistance is dynamic and varies by region. Therefore, the implementation of non-radioactive, robust, high-throughput antimalarial sensitivity assays is critical for defining region-specific prophylaxis and treatment guidelines.
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Affiliation(s)
- Daouda Ndiaye
- Faculty of Medicine and Pharmacy, Cheikh Anta Diop University, Dakar, Senegal.
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Lucantoni L, Yerbanga RS, Lupidi G, Pasqualini L, Esposito F, Habluetzel A. Transmission blocking activity of a standardized neem (Azadirachta indica) seed extract on the rodent malaria parasite Plasmodium berghei in its vector Anopheles stephensi. Malar J 2010; 9:66. [PMID: 20196858 PMCID: PMC2846955 DOI: 10.1186/1475-2875-9-66] [Citation(s) in RCA: 43] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2009] [Accepted: 03/02/2010] [Indexed: 11/10/2022] Open
Abstract
Background The wide use of gametocytocidal artemisinin-based combination therapy (ACT) lead to a reduction of Plasmodium falciparum transmission in several African endemic settings. An increased impact on malaria burden may be achieved through the development of improved transmission-blocking formulations, including molecules complementing the gametocytocidal effects of artemisinin derivatives and/or acting on Plasmodium stages developing in the vector. Azadirachtin, a limonoid (tetranortriterpenoid) abundant in neem (Azadirachta indica, Meliaceae) seeds, is a promising candidate, inhibiting Plasmodium exflagellation in vitro at low concentrations. This work aimed at assessing the transmission-blocking potential of NeemAzal®, an azadirachtin-enriched extract of neem seeds, using the rodent malaria in vivo model Plasmodium berghei/Anopheles stephensi. Methods Anopheles stephensi females were offered a blood-meal on P. berghei infected, gametocytaemic BALB/c mice, treated intraperitoneally with NeemAzal, one hour before feeding. The transmission-blocking activity of the product was evaluated by assessing oocyst prevalence, oocyst density and capacity to infect healthy mice. To characterize the anti-plasmodial effects of NeemAzal® on early midgut stages, i.e. zygotes and ookinetes, Giemsa-stained mosquito midgut smears were examined. Results NeemAzal® completely blocked P. berghei development in the vector, at an azadirachtin dose of 50 mg/kg mouse body weight. The totally 138 examined, treated mosquitoes (three experimental replications) did not reveal any oocyst and none of the healthy mice exposed to their bites developed parasitaemia. The examination of midgut content smears revealed a reduced number of zygotes and post-zygotic forms and the absence of mature ookinetes in treated mosquitoes. Post-zygotic forms showed several morphological alterations, compatible with the hypothesis of an azadirachtin interference with the functionality of the microtubule organizing centres and with the assembly of cytoskeletal microtubules, which are both fundamental processes in Plasmodium gametogenesis and ookinete formation. Conclusions This work demonstrated in vivo transmission blocking activity of an azadirachtin-enriched neem seed extract at an azadirachtin dose compatible with 'druggability' requisites. These results and evidence of anti-plasmodial activity of neem products accumulated over the last years encourage to convey neem compounds into the drug discovery & development pipeline and to evaluate their potential for the design of novel or improved transmission-blocking remedies.
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Affiliation(s)
- Leonardo Lucantoni
- Scuola di Scienze del Farmaco e dei Prodotti della Salute, Università di Camerino, Camerino (MC), Italy.
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143
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Decreased in vitro susceptibility of Plasmodium falciparum isolates to artesunate, mefloquine, chloroquine, and quinine in Cambodia from 2001 to 2007. Antimicrob Agents Chemother 2010; 54:2135-42. [PMID: 20194689 DOI: 10.1128/aac.01304-09] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
This study describes the results of in vitro antimalarial susceptibility assays and molecular polymorphisms of Plasmodium falciparum isolates from Cambodia. The samples were collected from patients enrolled in therapeutic efficacy studies (TES) conducted by the Cambodian National Malaria Control Program for the routine efficacy monitoring of artemisinin-based combination therapy (ACT) (artesunate-mefloquine and artemether-lumefantrine combinations). The isolates (n = 2,041) were obtained from nine sentinel sites during the years 2001 to 2007. Among these, 1,588 were examined for their in vitro susceptibilities to four antimalarials (artesunate, mefloquine, chloroquine, and quinine), and 851 isolates were genotyped for single nucleotide polymorphisms (SNPs). The geometric means of the 50% inhibitory concentrations (GMIC(50)s) of the four drugs tested were significantly higher for isolates from western Cambodia than for those from eastern Cambodia. GMIC(50)s for isolates from participants who failed artesunate-mefloquine therapy were significantly higher than those for patients who were cured (P, <0.001). In vitro correlation of artesunate with the other drugs was observed. The distributions of the SNPs differed between eastern and western Cambodia, suggesting different genetic backgrounds of the parasite populations in these two parts of the country. The GMIC(50)s of the four drugs tested increased significantly in eastern Cambodia during 2006 to 2007. These results are worrisome, because they may signal deterioration of the efficacy of artesunate-mefloquine beyond the Cambodian-Thai border.
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144
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Gardiner DL, Skinner-Adams TS, Brown CL, Andrews KT, Stack CM, McCarthy JS, Dalton JP, Trenholme KR. Plasmodium falciparum: new molecular targets with potential for antimalarial drug development. Expert Rev Anti Infect Ther 2010; 7:1087-98. [PMID: 19883329 DOI: 10.1586/eri.09.93] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Malaria remains one of the world's most devastating infectious diseases. Drug resistance to all classes of antimalarial agents has now been observed, highlighting the need for new agents that act against novel parasite targets. The complete sequencing of the Plasmodium falciparum genome has allowed the identification of new molecular targets within the parasite that may be amenable to chemotherapeutic intervention. In this review, we investigate four possible targets for the future development of new classes of antimalarial agents. These targets include histone deacetylase, the aspartic proteases or plasmepsins, aminopeptidases and the purine salvage enzyme hypoxanthine-xanthine-guanine phosphoribosyltransferase.
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Affiliation(s)
- Donald L Gardiner
- Malaria Biology Laboratory, Queensland Institute of Medical Research, 300 Herston Road, Herston, QLD 4006, Australia.
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145
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Jambou R, Martinelli A, Pinto J, Gribaldo S, Legrand E, Niang M, Kim N, Pharath L, Volnay B, Ekala MT, Bouchier C, Fandeur T, Berzosa P, Benito A, Ferreira ID, Ferreira C, Vieira PP, Alecrim MDG, Mercereau-Puijalon O, Cravo P. Geographic structuring of the Plasmodium falciparum sarco(endo)plasmic reticulum Ca2+ ATPase (PfSERCA) gene diversity. PLoS One 2010; 5:e9424. [PMID: 20195531 PMCID: PMC2828472 DOI: 10.1371/journal.pone.0009424] [Citation(s) in RCA: 35] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2009] [Accepted: 01/22/2010] [Indexed: 01/09/2023] Open
Abstract
Artemisinin, a thapsigargin-like sesquiterpene has been shown to inhibit the Plasmodium falciparum sarco/endoplasmic reticulum calcium-ATPase PfSERCA. To collect baseline pfserca sequence information before field deployment of Artemisinin-based Combination therapies that may select mutant parasites, we conducted a sequence analysis of 100 isolates from multiple sites in Africa, Asia and South America. Coding sequence diversity was large, with 29 mutated codons, including 32 SNPs (average of one SNP/115 bp), of which 19 were novel mutations. Most SNP detected in this study were clustered within a region in the cytosolic head of the protein. The PfSERCA functional domains were very well conserved, with non synonymous mutations located outside the functional domains, except for the S769N mutation associated in French Guiana with elevated IC50 for artemether. The S769N mutation is located close to the hinge of the headpiece, which in other species modulates calcium affinity and in consequence efficacy of inhibitors, possibly linking calcium homeostasis to drug resistance. Genetic diversity was highest in Senegal, Brazil and French Guiana, and few mutations were identified in Asia. Population genetic analysis was conducted for a partial fragment of the gene encompassing nucleotide coordinates 87-2862 (unambiguous sequence available for 96 isolates). This supported a geographic clustering, with a separation between Old and New World samples and one dominant ancestral haplotype. Genetic drift alone cannot explain the observed polymorphism, suggesting that other evolutionary mechanisms are operating. One possible contributor could be the frequency of haemoglobinopathies that are associated with calcium dysregulation in the erythrocyte.
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Affiliation(s)
- Ronan Jambou
- Institut Pasteur de Dakar, BP 220, Dakar, Senegal.
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146
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Chaijaroenkul W, Wisedpanichkij R, Na-Bangchang K. Monitoring of in vitro susceptibilities and molecular markers of resistance of Plasmodium falciparum isolates from Thai-Myanmar border to chloroquine, quinine, mefloquine and artesunate. Acta Trop 2010; 113:190-4. [PMID: 19879850 DOI: 10.1016/j.actatropica.2009.10.016] [Citation(s) in RCA: 37] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2009] [Revised: 10/22/2009] [Accepted: 10/22/2009] [Indexed: 11/15/2022]
Abstract
Malaria is one of the major causes of morbidity and mortality worldwide. The major factor which has aggravated the situation is the emergence of multidrug resistant Plasmodium falciparum malaria. To successfully deal with the problem, thorough understanding of the molecular bases for reduced parasite sensitivity to existing antimalarial drugs is of considerable importance. The objective of this work was to broaden the insight into the molecular mechanisms of resistance of P. falciparum to quinoline-containing antimalarials and artemisinin derivatives. Polymorphisms of the candidate genes pfmdr1 and pfcrt were investigated in relation to the susceptibility (in vitro sensitivity) of P. falciparum isolates to chloroquine (CQ), mefloquine (MQ), quinine (QN) and the artemisinin derivative - artesunate (AS). A total of 26 P. falciparum isolates were successful cultured. In vitro sensitivity results indicate the increase in susceptibility of P. falciparum strains in Thailand to CQ, while the susceptibility to MQ and QN was markedly declined. The pattern of cross-resistance was observed between MQ vs QN vs AS. Only one point mutation in the pfmdr1 gene, i.e., N86Y was observed with low prevalence of 7.7% (2/26). In contrast, the mutations at positions 76T, 220S, 271E, 326S, 356T and 371I in the pfcrt gene were identified in almost all isolates (25 isolates, 96.2%). The association between polymorphisms of the pfmdr1 and susceptibility of the parasite to MQ and QN was observed (increased susceptibilities to MQ and QN in isolates with mutations). Moreover, the correlation between pfmdr1 gene amplification and susceptibility of the parasite to MQ, QN and AS was observed (decreased susceptibilities to MQ, QN and AS in isolates with increased pfmdr1 copy number).
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Affiliation(s)
- Wanna Chaijaroenkul
- Graduate Program in Biomedical Sciences, Faculty of Allied Health Sciences, Thammasat University, Rangsit, Patumthani 12121, Thailand
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147
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Sueker JJ, Chretien JP, Gaydos JC, Russell KL. Global Infectious Disease Surveillance at DoD Overseas Laboratories, 1999-2007. Am J Trop Med Hyg 2010; 82:23-7. [PMID: 20064990 DOI: 10.4269/ajtmh.2010.09-0139] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
The United States Department of Defense Global Emerging Infections Surveillance and Response System (DoD-GEIS) conducted a review in 2008 of projects funded by DoD-GEIS at five partner overseas laboratories from 1999 through 2007. During this period, the annual overseas programming budget grew from US$1.038 million to US$21 million. The review describes the distribution of project priorities and geographic locations over the years, the types of outcomes the projects generated, and the frequency with which they involved collaboration with other public health agencies and organizations, including CDC and WHO. Areas for further program strengthening are identified.
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Affiliation(s)
- J Jeremy Sueker
- Armed Forces Health Surveillance Center, Silver Spring, Maryland 20910, USA.
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148
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Juliano JJ, Gadalla N, Sutherland CJ, Meshnick SR. The perils of PCR: can we accurately 'correct' antimalarial trials? Trends Parasitol 2010; 26:119-24. [PMID: 20083436 DOI: 10.1016/j.pt.2009.12.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/11/2009] [Revised: 11/17/2009] [Accepted: 12/22/2009] [Indexed: 01/17/2023]
Abstract
During follow-up in antimalarial drug trials, treated subjects can be newly infected. PCR correction is used to distinguish this re-infection from drug failure (recrudescence) and to adjust final drug efficacy estimates. The epidemiological, biological and technical limitations of PCR correction and how this can lead to misclassification in drug trial outcomes are underappreciated. This article considers these limitations and proposes a framework for reporting, interpreting and improving PCR correction of antimalarial trials.
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Affiliation(s)
- Jonathan J Juliano
- Division of Infectious Diseases, Department of Medicine, University of North Carolina School of Medicine, Chapel Hill, NC 27599, USA
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149
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In vitro sensitivities of Plasmodium falciparum to different antimalarial drugs in Uganda. Antimicrob Agents Chemother 2010; 54:1200-6. [PMID: 20065051 DOI: 10.1128/aac.01412-09] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/22/2023] Open
Abstract
The control of malaria is challenged by resistance of Plasmodium falciparum to multiple drugs. New combination regimens are now advocated for the treatment of uncomplicated falciparum malaria, but the extent of resistance to newer agents is incompletely understood. We measured the in vitro sensitivity of P. falciparum parasites cultured from children enrolled in a drug efficacy trial in Kampala, Uganda, from 2006 to 2008. Sensitivities were measured by comparing levels of histidine-rich protein-2 in parasites incubated with different concentrations of drugs with those in untreated controls. The cultured parasites exhibited a wide range of sensitivities to chloroquine (CQ); monodesethylamodiaquine (MDAQ), the major active metabolite of amodiaquine; and quinine (QN). Mean 50% inhibitory concentration (IC(50)) results were above standard cutoffs for resistance for CQ and MDAQ. Parasites were generally sensitive to dihydroartemisinin (DHA), lumefantrine (LM), and piperaquine (PQ). For CQ, MDAQ, and QN but not the other drugs, activities against individual strains were highly correlated. We also assessed known resistance-mediating polymorphisms in two putative transporters, pfcrt and pfmdr1. When parasites that were least and most sensitive to each drug were compared, the pfmdr1 86Y mutation was significantly more common in parasites that were most resistant to CQ and MDAQ, and the pfmdr1 D1246Y mutation was significantly more common in parasites that were most resistant to MDAQ and QN. In summary, we demonstrated in parasites from Kampala a range of sensitivities to older drugs; correlation of sensitivities to CQ, MDAQ, and QN; and good activity against nearly all strains for DHA, LM, and PQ.
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150
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ABC - antibiotics-based combinations for the treatment of severe malaria? Trends Parasitol 2009; 25:540-4. [DOI: 10.1016/j.pt.2009.09.001] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/20/2009] [Revised: 07/28/2009] [Accepted: 09/07/2009] [Indexed: 11/20/2022]
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