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Li J, Docile HJ, Fisher D, Pronyuk K, Zhao L. Current Status of Malaria Control and Elimination in Africa: Epidemiology, Diagnosis, Treatment, Progress and Challenges. J Epidemiol Glob Health 2024:10.1007/s44197-024-00228-2. [PMID: 38656731 DOI: 10.1007/s44197-024-00228-2] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/04/2024] [Accepted: 04/10/2024] [Indexed: 04/26/2024] Open
Abstract
The African continent carries the greatest malaria burden in the world. Falciparum malaria especially has long been the leading cause of death in Africa. Climate, economic factors, geographical location, human intervention and unstable security are factors influencing malaria transmission. Due to repeated infections and early interventions, the proportion of clinically atypical malaria or asymptomatic plasmodium carriers has increased significantly, which easily lead to misdiagnosis and missed diagnosis. African countries have made certain progress in malaria control and elimination, including rapid diagnosis of malaria, promotion of mosquito nets and insecticides, intermittent prophylactic treatment in high-risk groups, artemisinin based combination therapies, and the development of vaccines. Between 2000 and 2022, there has been a 40% decrease in malaria incidence and a 60% reduction in mortality rate in the WHO African Region. However, many challenges are emerging in the fight against malaria in Africa, such as climate change, poverty, substandard health services and coverage, increased outdoor transmission and the emergence of new vectors, and the growing threat of resistance to antimalarial drugs and insecticides. Joint prevention and treatment, identifying molecular determinants of resistance, new drug development, expanding seasonal malaria chemo-prevention intervention population, and promoting the vaccination of RTS, S/AS01 and R21/Matrix-M may help to solve the dilemma. China's experience in eliminating malaria is conducive to Africa's malaria prevention and control, and China-Africa cooperation needs to be constantly deepened and advanced. Our review aims to help the global public develop a comprehensive understanding of malaria in Africa, thereby contributing to malaria control and elimination.
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Affiliation(s)
- Jiahuan Li
- Department of Infectious Diseases, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - Haragakiza Jean Docile
- Department of Infectious Diseases, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China
| | - David Fisher
- Department of Medical Biosciences, Faculty of Natural Sciences, University of The Western Cape, Cape Town, South Africa
| | - Khrystyna Pronyuk
- Department of Infectious Diseases, O. Bogomolets National Medical University, Kyiv, Ukraine
| | - Lei Zhao
- Department of Infectious Diseases, Union Hospital, Tongji Medical College, Huazhong University of Science and Technology, Wuhan, People's Republic of China.
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Gandon S, Guillemet M, Gatchitch F, Nicot A, Renaud AC, Tremblay DM, Moineau S. Building pyramids against the evolutionary emergence of pathogens. Proc Biol Sci 2024; 291:20231529. [PMID: 38471546 DOI: 10.1098/rspb.2023.1529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/07/2023] [Accepted: 01/29/2024] [Indexed: 03/14/2024] Open
Abstract
Mutations allowing pathogens to escape host immunity promote the spread of infectious diseases in heterogeneous host populations and can lead to major epidemics. Understanding the conditions that slow down this evolution is key for the development of durable control strategies against pathogens. Here, we use theory and experiments to compare the efficacy of three strategies for the deployment of resistance: (i) a mixing strategy where the host population contains two single-resistant genotypes, (ii) a pyramiding strategy where the host carries a double-resistant genotype, (iii) a combining strategy where the host population is a mix of a single-resistant genotype and a double-resistant genotype. First, we use evolutionary epidemiology theory to clarify the interplay between demographic stochasticity and evolutionary dynamics to show that the pyramiding strategy always yields lower probability of evolutionary emergence. Second, we test experimentally these predictions with the introduction of bacteriophages into bacterial populations where we manipulated the diversity and the depth of immunity using a Clustered Regularly Interspaced Short Palindromic Repeats-CRISPR associated (CRISPR-Cas) system. These biological assays confirm that pyramiding multiple defences into the same host genotype and avoiding combination with single-defence genotypes is a robust way to reduce pathogen evolutionary emergence. The experimental validation of these theoretical recommendations has practical implications in various areas, including for the optimal deployment of resistance varieties in agriculture and for the design of durable vaccination strategies.
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Affiliation(s)
- Sylvain Gandon
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France
| | | | | | - Antoine Nicot
- CEFE, Univ Montpellier, CNRS, EPHE, IRD, Montpellier, France
| | - Ariane C Renaud
- Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, Quebec city, Canada G1V0A6
- Félix d'Hérelle Reference Center for Bacterial Viruses, Université Laval, Québec City, Canada G1V 0A6
| | - Denise M Tremblay
- Félix d'Hérelle Reference Center for Bacterial Viruses, Université Laval, Québec City, Canada G1V 0A6
| | - Sylvain Moineau
- Département de biochimie, de microbiologie et de bio-informatique, Faculté des sciences et de génie, Université Laval, Quebec city, Canada G1V0A6
- Félix d'Hérelle Reference Center for Bacterial Viruses, Université Laval, Québec City, Canada G1V 0A6
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Mandt REK, Luth MR, Tye MA, Mazitschek R, Ottilie S, Winzeler EA, Lafuente-Monasterio MJ, Gamo FJ, Wirth DF, Lukens AK. Diverse evolutionary pathways challenge the use of collateral sensitivity as a strategy to suppress resistance. eLife 2023; 12:e85023. [PMID: 37737220 PMCID: PMC10695565 DOI: 10.7554/elife.85023] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2022] [Accepted: 09/21/2023] [Indexed: 09/23/2023] Open
Abstract
Drug resistance remains a major obstacle to malaria control and eradication efforts, necessitating the development of novel therapeutic strategies to treat this disease. Drug combinations based on collateral sensitivity, wherein resistance to one drug causes increased sensitivity to the partner drug, have been proposed as an evolutionary strategy to suppress the emergence of resistance in pathogen populations. In this study, we explore collateral sensitivity between compounds targeting the Plasmodium dihydroorotate dehydrogenase (DHODH). We profiled the cross-resistance and collateral sensitivity phenotypes of several DHODH mutant lines to a diverse panel of DHODH inhibitors. We focus on one compound, TCMDC-125334, which was active against all mutant lines tested, including the DHODH C276Y line, which arose in selections with the clinical candidate DSM265. In six selections with TCMDC-125334, the most common mechanism of resistance to this compound was copy number variation of the dhodh locus, although we did identify one mutation, DHODH I263S, which conferred resistance to TCMDC-125334 but not DSM265. We found that selection of the DHODH C276Y mutant with TCMDC-125334 yielded additional genetic changes in the dhodh locus. These double mutant parasites exhibited decreased sensitivity to TCMDC-125334 and were highly resistant to DSM265. Finally, we tested whether collateral sensitivity could be exploited to suppress the emergence of resistance in the context of combination treatment by exposing wildtype parasites to both DSM265 and TCMDC-125334 simultaneously. This selected for parasites with a DHODH V532A mutation which were cross-resistant to both compounds and were as fit as the wildtype parent in vitro. The emergence of these cross-resistant, evolutionarily fit parasites highlights the mutational flexibility of the DHODH enzyme.
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Affiliation(s)
- Rebecca EK Mandt
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public HealthBostonUnited States
| | - Madeline R Luth
- Division of Host Pathogen Systems and Therapeutics, Department of Pediatrics, University of California, San DiegoSan DiegoUnited States
| | - Mark A Tye
- Center for Systems Biology, Massachusetts General HospitalBostonUnited States
- Harvard Graduate School of Arts and SciencesCambridgeUnited States
| | - Ralph Mazitschek
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public HealthBostonUnited States
- Center for Systems Biology, Massachusetts General HospitalBostonUnited States
| | - Sabine Ottilie
- Division of Host Pathogen Systems and Therapeutics, Department of Pediatrics, University of California, San DiegoSan DiegoUnited States
| | - Elizabeth A Winzeler
- Division of Host Pathogen Systems and Therapeutics, Department of Pediatrics, University of California, San DiegoSan DiegoUnited States
- Skaggs School of Pharmaceutical Sciences, University of California, San DiegoLa JollaUnited States
| | | | - Francisco Javier Gamo
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKlineMadridSpain
| | - Dyann F Wirth
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public HealthBostonUnited States
- Infectious Disease and Microbiome Program, The Broad InstituteCambridgeUnited States
| | - Amanda K Lukens
- Department of Immunology and Infectious Diseases, Harvard T.H. Chan School of Public HealthBostonUnited States
- Infectious Disease and Microbiome Program, The Broad InstituteCambridgeUnited States
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Wijnant GJ, Dumetz F, Dirkx L, Bulté D, Cuypers B, Van Bocxlaer K, Hendrickx S. Tackling Drug Resistance and Other Causes of Treatment Failure in Leishmaniasis. FRONTIERS IN TROPICAL DISEASES 2022. [DOI: 10.3389/fitd.2022.837460] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Leishmaniasis is a tropical infectious disease caused by the protozoan Leishmania parasite. The disease is transmitted by female sand flies and, depending on the infecting parasite species, causes either cutaneous (stigmatizing skin lesions), mucocutaneous (destruction of mucous membranes of nose, mouth and throat) or visceral disease (a potentially fatal infection of liver, spleen and bone marrow). Although more than 1 million new cases occur annually, chemotherapeutic options are limited and their efficacy is jeopardized by increasing treatment failure rates and growing drug resistance. To delay the emergence of resistance to existing and new drugs, elucidating the currently unknown causes of variable drug efficacy (related to parasite susceptibility, host immunity and drug pharmacokinetics) and improved use of genotypic and phenotypic tools to define, measure and monitor resistance in the field are critical. This review highlights recent progress in our understanding of drug action and resistance in Leishmania, ongoing challenges (including setbacks related to the COVID-19 pandemic) and provides an overview of possible strategies to tackle this public health challenge.
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Plowe CV. Malaria chemoprevention and drug resistance: a review of the literature and policy implications. Malar J 2022; 21:104. [PMID: 35331231 PMCID: PMC8943514 DOI: 10.1186/s12936-022-04115-8] [Citation(s) in RCA: 50] [Impact Index Per Article: 25.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2022] [Accepted: 03/03/2022] [Indexed: 01/19/2023] Open
Abstract
Chemoprevention strategies reduce malaria disease and death, but the efficacy of anti-malarial drugs used for chemoprevention is perennially threatened by drug resistance. This review examines the current impact of chemoprevention on the emergence and spread of drug resistant malaria, and the impact of drug resistance on the efficacy of each of the chemoprevention strategies currently recommended by the World Health Organization, namely, intermittent preventive treatment in pregnancy (IPTp); intermittent preventive treatment in infants (IPTi); seasonal malaria chemoprevention (SMC); and mass drug administration (MDA) for the reduction of disease burden in emergency situations. While the use of drugs to prevent malaria often results in increased prevalence of genetic mutations associated with resistance, malaria chemoprevention interventions do not inevitably lead to meaningful increases in resistance, and even high rates of resistance do not necessarily impair chemoprevention efficacy. At the same time, it can reasonably be anticipated that, over time, as drugs are widely used, resistance will generally increase and efficacy will eventually be lost. Decisions about whether, where and when chemoprevention strategies should be deployed or changed will continue to need to be made on the basis of imperfect evidence, but practical considerations such as prevalence patterns of resistance markers can help guide policy recommendations.
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Day T, Kennedy DA, Read AF, McAdams D. The economics of managing evolution. PLoS Biol 2021; 19:e3001409. [PMID: 34784349 PMCID: PMC8594813 DOI: 10.1371/journal.pbio.3001409] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2021] [Accepted: 09/07/2021] [Indexed: 11/19/2022] Open
Abstract
Humans are altering biological systems at unprecedented rates, and these alterations often have longer-term evolutionary impacts. Most obvious is the spread of resistance to pesticides and antibiotics. There are a wide variety of management strategies available to slow this evolution, and there are many reasons for using them. In this paper, we focus on the economic aspects of evolution management and ask: When is it economically beneficial for an individual decision-maker to invest in evolution management? We derive a simple dimensionless inequality showing that it is cost-effective to manage evolution when the percentage increase in the effective life span of the biological resource that management generates is larger than the percentage increase in annual profit that could be obtained by not managing evolution. We show how this inequality can be used to determine optimal investment choices for single decision-makers, to determine Nash equilibrium investment choices for multiple interacting decision-makers, and to examine how these equilibrium choices respond to regulatory interventions aimed at stimulating investment in evolution management. Our results are illustrated with examples involving Bacillus thuringiensis (Bt) crops and antibiotic use in fish farming.
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Affiliation(s)
- Troy Day
- Department of Mathematics and Statistics, Queen’s University, Kingston, Canada
- * E-mail:
| | - David A. Kennedy
- Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, State College, Pennsylvania, United States of America
| | - Andrew F. Read
- Center for Infectious Disease Dynamics, Department of Biology, The Pennsylvania State University, State College, Pennsylvania, United States of America
- Department of Entomology, The Pennsylvania State University, State College, Pennsylvania, United States of America
| | - David McAdams
- Fuqua School of Business, Duke University, Durham, North Carolina, United States of America
- Department of Economics, Duke University, Durham, North Carolina, United States of America
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Hastings IM, Hardy D, Kay K, Sharma R. Incorporating genetic selection into individual-based models of malaria and other infectious diseases. Evol Appl 2020; 13:2723-2739. [PMID: 33294019 PMCID: PMC7691459 DOI: 10.1111/eva.13077] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2020] [Revised: 06/16/2020] [Accepted: 07/11/2020] [Indexed: 01/04/2023] Open
Abstract
INTRODUCTION Control strategies for human infections are often investigated using individual-based models (IBMs) to quantify their impact in terms of mortality, morbidity and impact on transmission. Genetic selection can be incorporated into the IBMs to track the spread of mutations whose origin and spread are driven by the intervention and which subsequently undermine the control strategy; typical examples are mutations which encode drug resistance or diagnosis- or vaccine-escape phenotypes. METHODS AND RESULTS We simulated the spread of malaria drug resistance using the IBM OpenMalaria to investigate how the finite sizes of IBMs require strategies to optimally incorporate genetic selection. We make four recommendations. Firstly, calculate and report the selection coefficients, s, of the advantageous allele as the key genetic parameter. Secondly, use these values of "s" to calculate the wait time until a mutation successfully establishes itself in the pathogen population. Thirdly, identify the inherent limits of the IBM to robustly estimate small selection coefficients. Fourthly, optimize computational efficacy: when "s" is small, fewer replicates of larger IBMs may be more efficient than a larger number of replicates of smaller size. DISCUSSION The OpenMalaria IBM of malaria was an exemplar and the same principles apply to IBMs of other diseases.
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Affiliation(s)
| | - Diggory Hardy
- Swiss Tropical and Public Health InstituteBaselSwitzerland
- University of BaselBaselSwitzerland
| | | | - Raman Sharma
- Liverpool School of Tropical MedicineLiverpoolUK
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South A, Lees R, Garrod G, Carson J, Malone D, Hastings I. The role of windows of selection and windows of dominance in the evolution of insecticide resistance in human disease vectors. Evol Appl 2020; 13:738-751. [PMID: 32211064 PMCID: PMC7086049 DOI: 10.1111/eva.12897] [Citation(s) in RCA: 13] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/06/2019] [Revised: 10/25/2019] [Accepted: 10/28/2019] [Indexed: 01/23/2023] Open
Abstract
Persistent insecticides sprayed onto house walls, and incorporated into insecticide-treated bednets, provide long-acting, cost-effective control of vector-borne diseases such as malaria and leishmaniasis. The high concentrations that occur immediately postdeployment may kill both resistant and susceptible insects. However, insecticide concentration, and therefore killing ability, declines in the months after deployment. As concentrations decline, resistant insects start to survive, while susceptible insects are still killed. The period of time after deployment, within which the mortality of resistant individuals is lower than that of susceptible ones, has been termed the "window of selection" in other contexts. It is recognized as driving resistance in bacteria and malaria parasites, both of which are predominantly haploid. We argue that paying more attention to these mortality differences can help understand the evolution of insecticide resistance. Because insects are diploid, resistance encoded by single genes generates heterozygotes. This gives the potential for a narrower "window of dominance," within the window of selection, where heterozygote mortality is lower than that of susceptible homozygotes. We explore the general properties of windows of selection and dominance in driving resistance. We quantify their likely effect using data from new laboratory experiments and published data from the laboratory and field. These windows can persist months or years after insecticide deployments. Differential mortalities of resistant, susceptible and heterozygous genotypes, after public health deployments, constitute a major challenge to controlling resistance. Greater attention to mortality differences by genotype would inform strategies to reduce the evolution of resistance to existing and new insecticides.
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Affiliation(s)
- Andy South
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | - Rosemary Lees
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | - Gala Garrod
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
| | | | - David Malone
- Innovative Vector Control Consortium (IVCC)LiverpoolUK
- Present address:
Bill & Melinda Gates FoundationLondonUK
| | - Ian Hastings
- Liverpool School of Tropical Medicine (LSTM)LiverpoolUK
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Burns AL, Dans MG, Balbin JM, de Koning-Ward TF, Gilson PR, Beeson JG, Boyle MJ, Wilson DW. Targeting malaria parasite invasion of red blood cells as an antimalarial strategy. FEMS Microbiol Rev 2019; 43:223-238. [PMID: 30753425 PMCID: PMC6524681 DOI: 10.1093/femsre/fuz005] [Citation(s) in RCA: 41] [Impact Index Per Article: 8.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/08/2018] [Accepted: 02/11/2019] [Indexed: 12/20/2022] Open
Abstract
Plasmodium spp. parasites that cause malaria disease remain a significant global-health burden. With the spread of parasites resistant to artemisinin combination therapies in Southeast Asia, there is a growing need to develop new antimalarials with novel targets. Invasion of the red blood cell by Plasmodium merozoites is essential for parasite survival and proliferation, thus representing an attractive target for therapeutic development. Red blood cell invasion requires a co-ordinated series of protein/protein interactions, protease cleavage events, intracellular signals, organelle release and engagement of an actin-myosin motor, which provide many potential targets for drug development. As these steps occur in the bloodstream, they are directly susceptible and exposed to drugs. A number of invasion inhibitors against a diverse range of parasite proteins involved in these different processes of invasion have been identified, with several showing potential to be optimised for improved drug-like properties. In this review, we discuss red blood cell invasion as a drug target and highlight a number of approaches for developing antimalarials with invasion inhibitory activity to use in future combination therapies.
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Affiliation(s)
- Amy L Burns
- Research Centre for Infectious Diseases, School of Biological Sciences, University of Adelaide, Adelaide, Australia 5005
| | - Madeline G Dans
- Burnet Institute, Melbourne, Victoria, Australia 3004.,Deakin University, School of Medicine, Waurn Ponds, Victoria, Australia 3216
| | - Juan M Balbin
- Research Centre for Infectious Diseases, School of Biological Sciences, University of Adelaide, Adelaide, Australia 5005
| | | | - Paul R Gilson
- Burnet Institute, Melbourne, Victoria, Australia 3004
| | - James G Beeson
- Burnet Institute, Melbourne, Victoria, Australia 3004.,Central Clinical School and Department of Microbiology, Monash University 3004.,Department of Medicine, University of Melbourne, Australia 3052
| | - Michelle J Boyle
- Burnet Institute, Melbourne, Victoria, Australia 3004.,QIMR Berghofer Medical Research Institute, Herston, Queensland, Australia 4006
| | - Danny W Wilson
- Research Centre for Infectious Diseases, School of Biological Sciences, University of Adelaide, Adelaide, Australia 5005.,Burnet Institute, Melbourne, Victoria, Australia 3004
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Gallay J, Pothin E, Mosha D, Lutahakana E, Mazuguni F, Zuakulu M, Decosterd LA, Genton B. Predictors of residual antimalarial drugs in the blood in community surveys in Tanzania. PLoS One 2018; 13:e0202745. [PMID: 30192770 PMCID: PMC6128528 DOI: 10.1371/journal.pone.0202745] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2018] [Accepted: 08/08/2018] [Indexed: 01/09/2023] Open
Abstract
Background Understanding pattern of antimalarials use at large scale helps ensuring appropriate use of treatments and preventing the spread of resistant parasites. We estimated the proportion of individuals in community surveys with residual antimalarials in their blood and identified the factors associated with the presence of the most commonly detected drugs, lumefantrine and/or desbutyl-lumefantrine (LF/DLF) or sulfadoxine-pyrimethamine (SP). Methods A cross-sectional survey was conducted in 2015 in three regions of Tanzania with different levels of malaria endemicity. Interviews were conducted and blood samples collected through household surveys for further antimalarial measurements using liquid chromatography coupled to tandem mass spectrometry. In addition, diagnosis and treatment availability was investigated through outlet surveys. Multilevel mixed effects logistic regression models were used to estimate odds ratios for having LF/DLF or SP in the blood. Results Amongst 6391 participants, 12.4% (792/6391) had LF/DLF and 8.0% (510/6391) SP in the blood. Factors associated with higher odds of detecting LF/DLF in the blood included fever in the previous two weeks (OR = 2.6, p<0.001), living in districts of higher malaria prevalence (OR = 1.5, p<0.001) and living in a ward in which all visited drug stores had artemisinin-based combination therapies in stocks (OR = 2.7, p = 0.020). Participants in older age groups were less likely to have LF/DLF in the blood (OR = 0.9, p<0.001). Factors associated with higher odds of having SP in the blood included being pregnant (OR = 4.6, p<0.001), living in Mwanza (OR = 3.9, p<0.001 compared to Mbeya), fever in the previous two weeks (OR = 1.7, p<0.001) and belonging to older age groups (OR = 1.2, p<0.001). Conclusion The most significant predictors identified were expected. History of fever in the past two weeks and young age were significant predictors of LF/DLF in the blood, which is encouraging. Antimalarial drug pressure was high and hence the use of recommended first-line drugs in combination with malaria Rapid Diagnostics Tests should be promoted to ensure appropriate treatment.
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Affiliation(s)
- Joanna Gallay
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Service and Laboratory of Clinical Pharmacology, University Hospital, Lausanne, Switzerland
- * E-mail:
| | - Emilie Pothin
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
| | | | | | | | | | | | - Blaise Genton
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
- University of Basel, Basel, Switzerland
- Division of Infectious Diseases and Department of Community Health, University Hospital, Lausanne, Switzerland
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Smith TA, Chitnis N, Penny M, Tanner M. Malaria Modeling in the Era of Eradication. Cold Spring Harb Perspect Med 2017; 7:cshperspect.a025460. [PMID: 28003280 DOI: 10.1101/cshperspect.a025460] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Mathematical models provide the essential basis of rational research and development strategies in malaria, informing the choice of which technologies to target, which deployment strategies to consider, and which populations to focus on. The Internet and remote sensing technologies also enable assembly of ever more relevant field data. Together with supercomputing technology, this has made available timely descriptions of the geography of malaria transmission and disease across the world and made it possible for policy and planning to be informed by detailed simulations of the potential impact of intervention programs. These information technology advances do not replace the basic understanding of the dynamics of malaria transmission that should be embedded in the thinking of anyone planning malaria interventions. The appropriate use of modeling may determine whether we are living in an era of hubris or indeed in an age of eradication.
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Affiliation(s)
- Thomas A Smith
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
| | - Nakul Chitnis
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
| | - Melissa Penny
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
| | - Marcel Tanner
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel CH 4002, Switzerland; and University of Basel, Basel CH 4001, Switzerland
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Palmer‐Young EC, Sadd BM, Adler LS. Evolution of resistance to single and combined floral phytochemicals by a bumble bee parasite. J Evol Biol 2017; 30:300-312. [PMID: 27783434 PMCID: PMC5324628 DOI: 10.1111/jeb.13002] [Citation(s) in RCA: 16] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/10/2016] [Revised: 10/20/2016] [Accepted: 10/21/2016] [Indexed: 01/05/2023]
Abstract
Repeated exposure to inhibitory compounds can drive the evolution of resistance, which weakens chemical defence against antagonists. Floral phytochemicals in nectar and pollen have antimicrobial properties that can ameliorate infection in pollinators, but evolved resistance among parasites could diminish the medicinal efficacy of phytochemicals. However, multicompound blends, which occur in nectar and pollen, present simultaneous chemical challenges that may slow resistance evolution. We assessed evolution of resistance by the common bumble bee gut parasite Crithidia bombi to two floral phytochemicals, singly and combined, over 6 weeks (~100 generations) of chronic exposure. Resistance of C. bombi increased under single and combined phytochemical exposure, without any associated costs of reduced growth under phytochemical-free conditions. After 6 weeks' exposure, phytochemical concentrations that initially inhibited growth by > 50%, and exceeded concentrations in floral nectar, had minimal effects on evolved parasite lines. Unexpectedly, the phytochemical combination did not impede resistance evolution compared to single compounds. These results demonstrate that repeated phytochemical exposure, which could occur in homogeneous floral landscapes or with therapeutic phytochemical treatment of managed hives, can cause rapid evolution of resistance in pollinator parasites. We discuss possible explanations for submaximal phytochemical resistance in natural populations. Evolved resistance could diminish the antiparasitic value of phytochemical ingestion, weakening an important natural defence against infection.
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Affiliation(s)
| | - B. M. Sadd
- School of Biological SciencesIllinois State UniversityNormalILUSA
| | - L. S. Adler
- Department of BiologyUniversity of Massachusetts at AmherstAmherstMAUSA
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Levick B, South A, Hastings IM. A Two-Locus Model of the Evolution of Insecticide Resistance to Inform and Optimise Public Health Insecticide Deployment Strategies. PLoS Comput Biol 2017; 13:e1005327. [PMID: 28095406 PMCID: PMC5283767 DOI: 10.1371/journal.pcbi.1005327] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2016] [Revised: 01/31/2017] [Accepted: 12/20/2016] [Indexed: 12/01/2022] Open
Abstract
We develop a flexible, two-locus model for the spread of insecticide resistance applicable to mosquito species that transmit human diseases such as malaria. The model allows differential exposure of males and females, allows them to encounter high or low concentrations of insecticide, and allows selection pressures and dominance values to differ depending on the concentration of insecticide encountered. We demonstrate its application by investigating the relative merits of sequential use of insecticides versus their deployment as a mixture to minimise the spread of resistance. We recover previously published results as subsets of this model and conduct a sensitivity analysis over an extensive parameter space to identify what circumstances favour mixtures over sequences. Both strategies lasted more than 500 mosquito generations (or about 40 years) in 24% of runs, while in those runs where resistance had spread to high levels by 500 generations, 56% favoured sequential use and 44% favoured mixtures. Mixtures are favoured when insecticide effectiveness (their ability to kill homozygous susceptible mosquitoes) is high and exposure (the proportion of mosquitoes that encounter the insecticide) is low. If insecticides do not reliably kill homozygous sensitive genotypes, it is likely that sequential deployment will be a more robust strategy. Resistance to an insecticide always spreads slower if that insecticide is used in a mixture although this may be insufficient to outperform sequential use: for example, a mixture may last 5 years while the two insecticides deployed individually may last 3 and 4 years giving an overall 'lifespan' of 7 years for sequential use. We emphasise that this paper is primarily about designing and implementing a flexible modelling strategy to investigate the spread of insecticide resistance in vector populations and demonstrate how our model can identify vector control strategies most likely to minimise the spread of insecticide resistance.
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Affiliation(s)
- Bethany Levick
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
| | - Andy South
- Independent consultant, Norwich, United Kingdom
| | - Ian M. Hastings
- Department of Parasitology, Liverpool School of Tropical Medicine, Liverpool, United Kingdom
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Hastings IM, Hodel EM, Kay K. Quantifying the pharmacology of antimalarial drug combination therapy. Sci Rep 2016; 6:32762. [PMID: 27604175 PMCID: PMC5036534 DOI: 10.1038/srep32762] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2016] [Accepted: 08/12/2016] [Indexed: 12/31/2022] Open
Abstract
Most current antimalarial drugs are combinations of an artemisinin plus a
‘partner’ drug from another class, and are known as
artemisinin-based combination therapies (ACTs). They are the frontline drugs in
treating human malaria infections. They also have a public-health role as an
essential component of recent, comprehensive scale-ups of malaria interventions and
containment efforts conceived as part of longer term malaria elimination efforts.
Recent reports that resistance has arisen to artemisinins has caused considerable
concern. We investigate the likely impact of artemisinin resistance by quantifying
the contribution artemisinins make to the overall therapeutic capacity of ACTs. We
achieve this using a simple, easily understood, algebraic approach and by more
sophisticated pharmacokinetic/pharmacodynamic analyses of drug action; the two
approaches gave consistent results. Surprisingly, the artemisinin component
typically makes a negligible contribution (≪0.0001%) to the therapeutic
capacity of the most widely used ACTs and only starts to make a significant
contribution to therapeutic outcome once resistance has started to evolve to the
partner drugs. The main threat to antimalarial drug effectiveness and control comes
from resistance evolving to the partner drugs. We therefore argue that public health
policies be re-focussed to maximise the likely long-term effectiveness of the
partner drugs.
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Affiliation(s)
- Ian M Hastings
- Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
| | - Eva Maria Hodel
- Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
| | - Katherine Kay
- Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
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Comparison of artesunate-mefloquine and artemether-lumefantrine fixed-dose combinations for treatment of uncomplicated Plasmodium falciparum malaria in children younger than 5 years in sub-Saharan Africa: a randomised, multicentre, phase 4 trial. THE LANCET. INFECTIOUS DISEASES 2016; 16:1123-1133. [PMID: 27430374 PMCID: PMC5030279 DOI: 10.1016/s1473-3099(16)30020-2] [Citation(s) in RCA: 32] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Subscribe] [Scholar Register] [Received: 11/05/2015] [Revised: 03/09/2016] [Accepted: 03/11/2016] [Indexed: 11/24/2022]
Abstract
BACKGROUND WHO recommends combinations of an artemisinin derivative plus an antimalarial drug of longer half-life as treatment options for uncomplicated Plasmodium falciparum infection. In Africa, artemether-lumefantrine is the most widely used artemisinin-based combination therapy, whereas artesunate-mefloquine is used infrequently because of a perceived poor tolerance to mefloquine. WHO recommends reconsideration of the use of artesunate-mefloquine in Africa. We compared the efficacy and safety of fixed-dose artesunate-mefloquine with that of artemether-lumefantrine for treatment of children younger than 5 years with uncomplicated P falciparum malaria. METHODS We did this multicentre, phase 4, open-label, non-inferiority trial in Burkina Faso, Kenya, and Tanzania. Children aged 6-59 months with uncomplicated malaria were randomly assigned (1:1), via a computer-generated randomisation list, to receive 3 days' treatment with either one or two artesunate-mefloquine tablets (25 mg artesunate and 55 mg mefloquine) once a day or one or two artemether-lumefantrine tablets (20 mg artemether and 120 mg lumefantrine) twice a day. Parasitological assessments were done independently by two microscopists who were blinded to treatment allocation. The primary outcome was the PCR-corrected rate of adequate clinical and parasitological response (ACPR) at day 63 in the per-protocol population. Non-inferiority was shown if the lower limit of the 95% CI for the difference between groups was greater than -5%. Early vomiting was monitored and neuropsychiatric status assessed regularly during follow-up. This study is registered with ISRCTN, number ISRCTN17472707, and the Pan African Clinical Trials Registry, number PACTR201202000278282. FINDINGS 945 children were enrolled and randomised, 473 to artesunate-mefloquine and 472 to artemether-lumefantrine. The per-protocol population consisted of 407 children in each group. The PCR-corrected ACPR rate at day 63 was 90·9% (370 patients) in the artesunate-mefloquine group and 89·7% (365 patients) in the artemether-lumefantrine group (treatment difference 1·23%, 95% CI -2·84% to 5·29%). At 72 h after the start of treatment, no child had detectable parasitaemia and less than 6% had fever, with a similar number in each group (21 in the artesunate-mefloquine group vs 24 in the artemether-lumefantrine group). The safety profiles of artesunate-mefloquine and artemether-lumefantrine were similar, with low rates of early vomiting (71 [15·3%] of 463 patients in the artesunate-mefloquine group vs 79 [16·8%] of 471 patients in the artemether-lumefantrine group in any of the three dosing days), few neurological adverse events (ten [2·1%] of 468 vs five [1·1%] of 465), and no detectable psychiatric adverse events. INTERPRETATION Artesunate-mefloquine is effective and safe, and an important treatment option, for children younger than 5 years with uncomplicated P falciparum malaria in Africa. FUNDING Agence Française de Développement, France; Department for International Development, UK; Dutch Ministry of Foreign Affairs, Netherlands; European and Developing Countries Clinical Trials Partnership; Fondation Arpe, Switzerland; Médecins Sans Frontières; Swiss Agency for Development and Cooperation, Switzerland.
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Woods RJ, Read AF. Clinical management of resistance evolution in a bacterial infection: A case study. EVOLUTION MEDICINE AND PUBLIC HEALTH 2015; 2015:281-8. [PMID: 26454762 PMCID: PMC4629395 DOI: 10.1093/emph/eov025] [Citation(s) in RCA: 24] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 06/09/2015] [Accepted: 09/17/2015] [Indexed: 11/24/2022]
Abstract
This chronic bacterial infection evolved extensive resistance, killing the patient. Evolutionary science is insufficiently developed to better manage such life-threatening evolution. We report the case of a patient with a chronic bacterial infection that could not be cured. Drug treatment became progressively less effective due to antibiotic resistance, and the patient died, in effect from overwhelming evolution. Even though the evolution of drug resistance was recognized as a major threat, and the fundamentals of drug resistance evolution are well understood, it was impossible to make evidence-based decisions about the evolutionary risks associated with the various treatment options. We present this case to illustrate the urgent need for translational research in the evolutionary medicine of antibiotic resistance.
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Affiliation(s)
- Robert J Woods
- Division of Infectious Diseases, Department of Internal Medicine, University of Michigan, Ann Arbor, MI 48109, USA
| | - Andrew F Read
- Department of Biology, Center for Infectious Disease Dynamics, Pennsylvania State University, University Park PA 16802, USA Department of Entomology, Center for Infectious Disease Dynamics, Pennsylvania State University, University Park PA 16802, USA
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17
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Kay K, Hastings IM. Measuring windows of selection for anti-malarial drug treatments. Malar J 2015; 14:292. [PMID: 26228915 PMCID: PMC4521485 DOI: 10.1186/s12936-015-0810-4] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 07/15/2015] [Indexed: 11/28/2022] Open
Abstract
BACKGROUND The long half-lives of malaria 'partner' drugs are a potent force selecting for drug resistance. Clinical trials can quantify this effect by estimating a window of selection (WoS), defined as the amount of time post-treatment when drug levels are sufficiently high that resistant parasites can re-establish an infection while preventing drug-sensitive parasites from establishing viable infections. METHODS The ability of clinical data to accurately estimate the true WoS was investigated using standard pharmacokinetic-pharmacodynamic models for three widely used malaria drugs: artemether-lumefantrine (AR-LF), artesunate-mefloquine (AS-MQ) and dihydroartemisinin-piperaquine (DHA-PPQ). Estimates of the clinical WoS either (1) ignored all new infections occurring after the 63-day follow-up period, as is currently done in clinical trials, or, (2) recognized that all individuals would eventually be re-infected and arbitrarily assigned them a new infection day. RESULTS The results suggest current methods of estimating the clinical WoS underestimate the true WoS by as much as 9 days for AR-LF, 33 days for AS-MQ and 7 days for DHA-PPQ. The new method of estimating clinical WoS (i.e., retaining all individuals in the analysis) was significantly better at estimating the true WoS for AR-LF and AS-MQ. CONCLUSIONS Previous studies, based on clinically observed WoS, have probably underestimated the 'true' WoS and hence the role of drugs with long half-lives in driving resistance. This has important policy implications: high levels of drug use are inevitable in mass drug administration programmes and intermittent preventative treatment programmes and the analysis herein suggests these policies will be far more potent drivers of resistance than previously thought.
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Affiliation(s)
- Katherine Kay
- Parasitology Group, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
| | - Ian M Hastings
- Parasitology Group, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, L3 5QA, UK.
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CYP2B6*6 genotype and high efavirenz plasma concentration but not nevirapine are associated with low lumefantrine plasma exposure and poor treatment response in HIV-malaria-coinfected patients. THE PHARMACOGENOMICS JOURNAL 2015; 16:88-95. [PMID: 25963334 DOI: 10.1038/tpj.2015.37] [Citation(s) in RCA: 40] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/26/2014] [Revised: 02/12/2015] [Accepted: 04/07/2015] [Indexed: 01/03/2023]
Abstract
We investigated the influence of efavirenz (EFV)- or nevirapine (NVP)-based antiretroviral therapy (ART) on lumefantrine plasma exposure in HIV-malaria-coinfected patients and implication of pharmacogenetic variations. A total of 269 HIV patients with uncomplicated falciparum malaria on NVP-based ART (NVP-arm), EFV-based ART (EFV-arm) or not receiving ART (control-arm) were enrolled and treated with artemether-lumefantrine. Day-7 lumefantrine, baseline EFV and NVP plasma concentrations, and CYP2B6*6,*18, CYP3A4*1B, CYP3A5*3,*6,*7, ABCB1 c.3435C>T and ABCB1 c.4036A>G genotypes were determined. The median day-7 lumefantrine plasma concentration was significantly lower in the EFV-arm compared with that in NVP- and control-arm. High EFV plasma concentrations and CYP2B6*6/*6 genotype significantly correlated with low lumefantrine plasma concentrations and high rate of recurrent parasitemia. No significant effect of NVP-based ART on lumefantrine exposure was observed. In conclusion, owing to long-term CYP3A induction, EFV-based ART cotreatment significantly reduces lumefantrine plasma exposure leading to poor malaria treatment response, which is more pronounced in CYP2B6 slow metabolizers.
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Peak CM, Thuan PD, Britton A, Nguyen TD, Wolbers M, Thanh NV, Buckee CO, Boni MF. Measuring the association between artemisinin-based case management and malaria incidence in southern Vietnam, 1991-2010. Am J Trop Med Hyg 2015; 92:811-817. [PMID: 25667053 PMCID: PMC4385779 DOI: 10.4269/ajtmh.14-0461] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 12/26/2014] [Indexed: 11/07/2022] Open
Abstract
In addition to being effective, fast-acting, and well tolerated, artemisinin-based combination therapies (ACTs) are able to kill certain transmission stages of the malaria parasite. However, the population-level impacts of ACTs on reducing malaria transmission have been difficult to assess. In this study on the history of malaria control in Vietnam, we assemble annual reporting on malaria case counts, coverage with insecticide-treated nets (ITN) and indoor residual spraying (IRS), and drug purchases by provincial malaria control programs from 1991 to 2010 in Vietnam's 20 southern provinces. We observe a significant negative association between artemisinin use and malaria incidence, with a 10% absolute increase in the purchase proportion of artemisinin-containing regimens being associated with a 29.1% (95% confidence interval: 14.8–41.0%) reduction in slide-confirmed malaria incidence, after accounting for changes in urbanization, ITN/IRS coverage, and two indicators of health system capacity. One budget-related indicator of health system capacity was found to have a smaller association with malaria incidence, and no other significant factors were found. Our findings suggest that including an artemisinin component in malaria drug regimens was strongly associated with reduced malaria incidence in southern Vietnam, whereas changes in urbanization and coverage with ITN or IRS were not.
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Affiliation(s)
| | | | | | | | | | | | | | - Maciej F. Boni
- *Address correspondence to Maciej F. Boni, Oxford University Clinical Research Unit, Hospital for Tropical Diseases, 764 Vo Van Kiet Street, District 5, Ho Chi Minh City, Vietnam. E-mail:
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Kim Y, Escalante AA, Schneider KA. A population genetic model for the initial spread of partially resistant malaria parasites under anti-malarial combination therapy and weak intrahost competition. PLoS One 2014; 9:e101601. [PMID: 25007207 PMCID: PMC4090191 DOI: 10.1371/journal.pone.0101601] [Citation(s) in RCA: 14] [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: 01/07/2014] [Accepted: 06/09/2014] [Indexed: 11/18/2022] Open
Abstract
To develop public-health policies that extend the lifespan of affordable anti-malarial drugs as effective treatment options, it is necessary to understand the evolutionary processes leading to the origin and spread of mutations conferring drug resistance in malarial parasites. We built a population-genetic model for the emergence of resistance under combination drug therapy. Reproductive cycles of parasites are specified by their absolute fitness determined by clinical parameters, thus coupling the evolutionary-genetic with population-dynamic processes. Initial mutations confer only partial drug-resistance. Therefore, mutant parasites rarely survive combination therapy and within-host competition is very weak among parasites. The model focuses on the early phase of such unsuccessful recurrent mutations. This ends in the rare event of mutants enriching in an infected individual from which the successful spread of resistance over the entire population is initiated. By computer simulations, the waiting time until the establishment of resistant parasites is analysed. Resistance spreads quickly following the first appearance of a host infected predominantly by mutant parasites. This occurs either through a rare transmission of a resistant parasite to an uninfected host or through a rare failure of drugs in removing "transient" mutant alleles. The emergence of resistance is delayed with lower mutation rate, earlier treatment, higher metabolic cost of resistance, longer duration of high drug dose, and higher drug efficacy causing a stronger reduction in the sensitive and resistant parasites' fitnesses. Overall, contrary to other studies' proposition, the current model based on absolute fitness suggests that aggressive drug treatment delays the emergence of drug resistance.
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Affiliation(s)
- Yuseob Kim
- Department of Life Science and Division of EcoScience, Ewha Womans University, Seoul, South Korea
- * E-mail:
| | - Ananias A. Escalante
- School of Life Sciences and Center for Evolutionary Medicine and Informatics at the Biodesign Institute, Arizona State University, Tempe, Arizona, United States of America
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Kaplan RM, West EM, Norat-Collazo LM, Vargas J. A combination treatment strategy using pyrantel pamoate and oxibendazole demonstrates additive effects for controlling equine cyathostomins. EQUINE VET EDUC 2014. [DOI: 10.1111/eve.12201] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Affiliation(s)
- R. M. Kaplan
- Department of Infectious Diseases; College of Veterinary Medicine; University of Georgia; Athens Georgia USA
| | - E. M. West
- Department of Infectious Diseases; College of Veterinary Medicine; University of Georgia; Athens Georgia USA
| | - L. M. Norat-Collazo
- Department of Infectious Diseases; College of Veterinary Medicine; University of Georgia; Athens Georgia USA
| | - J. Vargas
- Department of Infectious Diseases; College of Veterinary Medicine; University of Georgia; Athens Georgia USA
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Hastings IM, Hodel EM. Pharmacological considerations in the design of anti-malarial drug combination therapies - is matching half-lives enough? Malar J 2014; 13:62. [PMID: 24552440 PMCID: PMC3975950 DOI: 10.1186/1475-2875-13-62] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2013] [Accepted: 02/15/2014] [Indexed: 11/20/2022] Open
Abstract
Anti-malarial drugs are now mainly deployed as combination therapy (CT), primarily as a mechanism to prevent or slow the spread of resistance. This strategy is justified by mathematical arguments that generally assume that drug 'resistance' is a binary all-or-nothing genetic trait. Herein, a pharmacological, rather than a purely genetic, approach is used to investigate resistance and it is argued that this provides additional insight into the design principles of anti-malarial CTs. It is usually suggested that half-lives of constituent drugs in a CT be matched: it appears more important that their post-treatment anti-malarial activity profiles be matched and strategies identified that may achieve this. In particular, the considerable variation in pharmacological parameters noted in both human and parasites populations may compromise this matching and it is, therefore, essential to accurately quantify the population pharmacokinetics of the drugs in the CTs. Increasing drug dosages will likely follow a law of diminishing returns in efficacy, i.e. a certain increase in dose will not necessarily lead to the same percent increase in efficacy. This may allow individual drug dosages to be lowered without proportional decrease in efficacy, reducing any potential toxicity, and allowing the other drug(s) in the CT to compensate for this reduced dosage; this is a dangerous strategy which is discussed further. Finally, pharmacokinetic and pharmacodynamic drug interactions and the role of resistance mechanisms are discussed. This approach generated an idealized target product profile (TPP) for anti-malarial CTs. There is a restricted pipeline of anti-malarial drugs but awareness of pharmacological design principles during the development stages could optimize CT design pre-deployment. This may help prevent changes in drug dosages and/or regimen that have previously occurred post-deployment in most current anti-malarial drugs.
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Affiliation(s)
- Ian M Hastings
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
| | - Eva Maria Hodel
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK
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Nogueira FHA, Reis NFA, Chellini PR, César IDC, Pianetti GA. Development and validation of an HPLC method for the simultaneous determination of artesunate and mefloquine hydrochloride in fixed-dose combination tablets. BRAZ J PHARM SCI 2013. [DOI: 10.1590/s1984-82502013000400024] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
The present study developed and validated an HPLC method for the simultaneous determination of artesunate (AS) and mefloquine hydrochloride (MQ) in fixed-dose combination tablets, according to ICH guidelines. The chromatographic separation was carried out on an XBridge C18 (250 x 4.6 mm i.d., 5 µm particle size, Waters) analytical column. The mobile phase included a 0.05 M monobasic potassium phosphate buffer (pH adjusted to 3.0 with phosphoric acid) and acetonitrile (50 + 50, v/v). The flow rate was 1.0 mL/min, and the run time was 13 minutes. A dual-wavelength approach was employed: AS detection was performed at 210 nm and MQ was detected at 283 nm, using a diode array detector. Stability of sample solutions was evaluated for 8 hours after preparation, during which time the solutions remained stable. Youden's test was employed to evaluate robustness. The method proved to be linear (r²>0.99), precise (RSD<2.0%), accurate, selective, and robust, proving to be appropriate for routine drug quality control analysis.
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Parveen A, Chakraborty A, Konreddy AK, Chakravarty H, Sharon A, Trivedi V, Bal C. Skeletal hybridization and PfRIO-2 kinase modeling for synthesis of α-pyrone analogs as anti-malarial agent. Eur J Med Chem 2013; 70:607-12. [PMID: 24211636 DOI: 10.1016/j.ejmech.2013.10.028] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2013] [Revised: 09/19/2013] [Accepted: 10/11/2013] [Indexed: 10/26/2022]
Abstract
The pharmacophoric hybridization and computational design approach were applied to generate a novel series of α-pyrone analogs as plausible anti-malarial lead candidate. A putative active site in flexible loop close to wing-helix domain of PfRIO2 kinase was explored computationally to understand the molecular basis of ligand binding. All the synthesized molecules (3a-g) exhibited in vitro antimalarial activity. Oxidative stress induced by 3a-d were calculated and found to be significantly higher in case of 3b. Therefore, 3b, which shown most significant result was identified as promising lead for further SAR study to develop potent anti-malarials.
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Affiliation(s)
- Afsana Parveen
- Department of Applied Chemistry, Birla Institute of Technology, Mesra, Ranchi 835215, India
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Kay K, Hastings IM. Improving pharmacokinetic-pharmacodynamic modeling to investigate anti-infective chemotherapy with application to the current generation of antimalarial drugs. PLoS Comput Biol 2013; 9:e1003151. [PMID: 23874190 PMCID: PMC3715401 DOI: 10.1371/journal.pcbi.1003151] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/19/2012] [Accepted: 06/07/2013] [Indexed: 01/13/2023] Open
Abstract
Mechanism-based pharmacokinetic-pharmacodynamic (PK/PD) modelling is the standard computational technique for simulating drug treatment of infectious diseases with the potential to enhance our understanding of drug treatment outcomes, drug deployment strategies, and dosing regimens. Standard methodologies assume only a single drug is used, it acts only in its unconverted form, and that oral drugs are instantaneously absorbed across the gut wall to their site of action. For drugs with short half-lives, this absorption period accounts for a significant period of their time in the body. Treatment of infectious diseases often uses combination therapies, so we refined and substantially extended the PK/PD methodologies to incorporate (i) time lags and drug concentration profiles resulting from absorption across the gut wall and, if required, conversion to another active form; (ii) multiple drugs within a treatment combination; (iii) differing modes of action of drugs in the combination: additive, synergistic, antagonistic; (iv) drugs converted to an active metabolite with a similar mode of action. This methodology was applied to a case study of two first-line malaria treatments based on artemisinin combination therapies (ACTs, artemether-lumefantrine and artesunate-mefloquine) where the likelihood of increased artemisinin tolerance/resistance has led to speculation on their continued long-term effectiveness. We note previous estimates of artemisinin kill rate were underestimated by a factor of seven, both the unconverted and converted form of the artemisinins kill parasites and the extended PK/PD methodology produced results consistent with field observations. The simulations predict that a potentially rapid decline in ACT effectiveness is likely to occur as artemisinin resistance spreads, emphasising the importance of containing the spread of artemisinin resistance before it results in widespread drug failure. We found that PK/PD data is generally very poorly reported in the malaria literature, severely reducing its value for subsequent re-application, and we make specific recommendations to improve this situation.
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Affiliation(s)
- Katherine Kay
- Parasitology Department, Liverpool School of Tropical Medicine, Pembroke Place, Liverpool, United Kingdom.
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Bains RK. African variation at Cytochrome P450 genes: Evolutionary aspects and the implications for the treatment of infectious diseases. EVOLUTION MEDICINE AND PUBLIC HEALTH 2013; 2013:118-34. [PMID: 24481193 PMCID: PMC3868406 DOI: 10.1093/emph/eot010] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
The genomics revolution has provided a plethora of data from many previously uncharacterized populations. The increase in the amount of genetic data has improved our understanding of why individuals and populations differ in their susceptibility to multiple diseases. It has also enabled researchers to identify how genomic variation, including at the Cytochrome P450 (CYP450) super-family, affects the safety and efficacy of therapeutic drugs. CYP450 metabolize ∼90% of clinically administered drugs. Variability in CYP450 expression is known to affect the safety and efficacy of therapeutic drugs, including many used in the treatment and control of infectious diseases. There are inter-ethnic differences in the frequencies of clinically relevant CYP450 variants which affect CYP450 expression. Comparative studies of African populations have identified population structuring at CYP450 genes. This is associated with intra-African differences in the success of drug therapies used in the treatment of infectious diseases. Therapeutic drugs dominate control strategies for infectious diseases and are widely administered through mass drug administration campaigns. However, resistance to chemotherapy is spreading across endemic regions. The most common response has been to increase chemotherapeutic dosages, and administer combination therapies. However, there are few pharmacovigilance data examining how these changes influence adverse drug reactions. This review provides an overview of current knowledge of intra-Africa CYP450 variation, and the known associations with sub-optimal clinical outcomes in the treatment of infectious diseases. In addition, the potential for evolutionary approaches in the study of CYP450 variation is discussed to examine their potential in preventative medicine and intervention strategies within Africa.
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Affiliation(s)
- Ripudaman K Bains
- Research Department of Genetics, Evolution and Environment, Darwin Building, University College London, London WC1E 6BT, UK
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Antimalarial drug resistance: a review of the biology and strategies to delay emergence and spread. Int J Antimicrob Agents 2013; 41:311-7. [PMID: 23394809 DOI: 10.1016/j.ijantimicag.2012.12.007] [Citation(s) in RCA: 82] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Revised: 12/12/2012] [Accepted: 12/13/2012] [Indexed: 11/21/2022]
Abstract
The emergence of resistance to former first-line antimalarial drugs has been an unmitigated disaster. In recent years, artemisinin class drugs have become standard and they are considered an essential tool for helping to eradicate the disease. However, their ability to reduce morbidity and mortality and to slow transmission requires the maintenance of effectiveness. Recently, an artemisinin delayed-clearance phenotype was described. This is believed to be the precursor to resistance and threatens local elimination and global eradication plans. Understanding how resistance emerges and spreads is important for developing strategies to contain its spread. Resistance is the result of two processes: (i) drug selection of resistant parasites; and (ii) the spread of resistance. In this review, we examine the factors that lead to both drug selection and the spread of resistance. We then examine strategies for controlling the spread of resistance, pointing out the complexities and deficiencies in predicting how resistance will spread.
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Antao T, Hastings I. Policy options for deploying anti-malarial drugs in endemic countries: a population genetics approach. Malar J 2012; 11:422. [PMID: 23244624 PMCID: PMC3546853 DOI: 10.1186/1475-2875-11-422] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2012] [Accepted: 12/08/2012] [Indexed: 11/30/2022] Open
Abstract
Background Anti-malarial drugs are constantly exposed to the threat of evolving drug resistance so good stewardship of existing therapy is an essential component of public health policy. However, the widespread availability of numerous different drugs through informal providers could undermine official drug deployment policies. A policy of multiple first-line therapy (MFT) is compared with the conventional policy of sequential drug deployment, i.e., where one drug is used until resistance evolves and then replaced by the next drug in the sequence. Methods Population genetic models of drug resistance are used to make the comparison; this methodology explicitly tracks the genetics of drug resistance (including, importantly, recombination in the sexual stage, intrahost dynamics, and direction of linkage disequilibrium). Results A policy of MFT outlasts sequential application providing drug usages are low to moderate, and appears not to drive widespread multi-drug resistance. Inadequate dosing is an even more potent driver of drug resistance than the MFT/sequential policy decision. Conclusions The provision of MFT as a deliberate policy can be encouraged provided overall treatment rates are low or moderate (less than around half of malaria infections are treated) and the ad hoc provision of MFT through the private sector may be tolerated. This must be fully supported by education to ensure people take adequate doses of each of the drugs.
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Affiliation(s)
- Tiago Antao
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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Murray V, Campbell HM, Gero AM. Plasmodium falciparum: The potential of the cancer chemotherapeutic agent cisplatin and its analogues as anti-malarials. Exp Parasitol 2012; 132:440-3. [DOI: 10.1016/j.exppara.2012.09.004] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/09/2012] [Revised: 09/06/2012] [Accepted: 09/10/2012] [Indexed: 10/27/2022]
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World Association for the Advancement of Veterinary Parasitology (W.A.A.V.P.) Guideline: Anthelmintic combination products targeting nematode infections of ruminants and horses. Vet Parasitol 2012. [DOI: 10.1016/j.vetpar.2012.09.004] [Citation(s) in RCA: 61] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022]
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Hien TT, Thuy-Nhien NT, Phu NH, Boni MF, Thanh NV, Nha-Ca NT, Thai LH, Thai CQ, Toi PV, Thuan PD, Long LT, Dong LT, Merson L, Dolecek C, Stepniewska K, Ringwald P, White NJ, Farrar J, Wolbers M. In vivo susceptibility of Plasmodium falciparum to artesunate in Binh Phuoc Province, Vietnam. Malar J 2012; 11:355. [PMID: 23101492 PMCID: PMC3504531 DOI: 10.1186/1475-2875-11-355] [Citation(s) in RCA: 113] [Impact Index Per Article: 9.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2012] [Accepted: 10/20/2012] [Indexed: 11/25/2022] Open
Abstract
Background By 2009, there were worrying signs from western Cambodia that parasitological responses to artesunate-containing treatment regimens for uncomplicated Plasmodium falciparum malaria were slower than elsewhere which suggested the emergence of artemisinin resistance. Vietnam shares a long land border with Cambodia with a large number of migrants crossing it on a daily basis. Therefore, there is an urgent need to investigate whether there is any evidence of a change in the parasitological response to the artemisinin derivatives in Vietnam. Methods From August 2010 to May 2011, a randomized controlled clinical trial in uncomplicated falciparum malaria was conducted to compare two doses of artesunate (AS) (2mg/kg/day versus 4 mg/kg/day for three days) followed by dihydroartemisinin-piperaquine (DHA-PPQ) and a control arm of DHA-PPQ. The goal was characterization of the current efficacy of artesunate in southern Vietnam. The primary endpoint of this study was the parasite clearance half-life; secondary endpoints included the parasite reduction ratios at 24 and 48 hours and the parasite clearance time. Results 166 patients were recruited into the study. The median parasite clearance half-lives were 3.54 (AS 2mg/kg), 2.72 (AS 4mg/kg), and 2.98 hours (DHA-PPQ) (p=0.19). The median parasite-reduction ratio at 24 hours was 48 in the AS 2mg/kg group compared with 212 and 113 in the other two groups, respectively (p=0.02). The proportions of patients with a parasite clearance time of >72 hours for AS 2mg/kg, AS 4mg/kg and DHA-PPQ were 27%, 27%, and 22%, respectively. Early treatment failure occurred in two (4%) and late clinical failure occurred in one (2%) of the 55 patients in the AS 2mg/kg group, as compared with none in the other two study arms. The PCR-corrected adequate clinical and parasitological response (APCR) rates in the three groups were 94%, 100%, and 100% (p=0.04). Conclusions This study demonstrated faster P. falciparum parasite clearance in southern Vietnam than in western Cambodia but slower clearance in comparison with historical data from Vietnam. Further studies to determine whether this represents the emergence of artemisinin resistance in this area are needed. Currently, the therapeutic response to DHA-PPQ remains satisfactory in southern Vietnam. Trial registration NTC01165372
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Affiliation(s)
- Tran Tinh Hien
- Wellcome Trust Major Overseas Programme (MOP), Oxford University Clinical Research Unit (OUCRU), Ho Chi Minh City, Vietnam.
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The role of combination anthelmintic formulations in the sustainable control of sheep nematodes. Vet Parasitol 2012; 186:151-8. [DOI: 10.1016/j.vetpar.2011.11.030] [Citation(s) in RCA: 73] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2011] [Revised: 11/03/2011] [Accepted: 11/07/2011] [Indexed: 11/22/2022]
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Footprints of positive selection associated with a mutation (N1575Y) in the voltage-gated sodium channel of Anopheles gambiae. Proc Natl Acad Sci U S A 2012; 109:6614-9. [PMID: 22493253 DOI: 10.1073/pnas.1201475109] [Citation(s) in RCA: 150] [Impact Index Per Article: 12.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Insecticide resistance is an ideal model to study the emergence and spread of adaptative variants. In the African malaria mosquito, Anopheles gambiae, this is complemented by a strong public health rationale. In this insect, resistance to pyrethroid and DDT insecticides is strongly associated with the mutations L1014F and L1014S within the para voltage-gated sodium channel (VGSC). Across much of West Africa, 1014F frequency approaches fixation. Here, we document the emergence of a mutation, N1575Y, within the linker between domains III-IV of the VGSC. In data extending over 40 kbp of the VGSC 1575Y occurs on only a single long-range haplotype, also bearing 1014F. The 1014F-1575Y haplotype was found in both M and S molecular forms of An. gambiae in West/Central African sample sites separated by up to 2,000 km. In Burkina Faso M form, 1575Y allele frequency rose significantly from 0.053 to 0.172 between 2008 and 2010. Extended haplotype homozygosity analysis of the wild-type 1575N allele showed rapid decay of linkage disequilibrium (LD), in sharp contrast to the extended LD exhibited by 1575Y. A haplotype with long-range LD and high/increasing frequency is a classical sign of strong positive selection acting on a recent mutant. 1575Y occurs ubiquitously on a 1014F haplotypic background, suggesting that the N1575Y mutation compensates for deleterious fitness effects of 1014F and/or confers additional resistance to insecticides. Haplotypic tests of association suggest the latter: The 1014F-1575Y haplotype confers a significant additive benefit above 1014F-1575N for survival to DDT (M form P = 0.03) and permethrin (S form P = 0.003).
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Taylor SM, Antonia A, Feng G, Mwapasa V, Chaluluka E, Molyneux M, ter Kuile FO, Rogerson SJ, Meshnick SR. Adaptive evolution and fixation of drug-resistant Plasmodium falciparum genotypes in pregnancy-associated malaria: 9-year results from the QuEERPAM study. INFECTION, GENETICS AND EVOLUTION : JOURNAL OF MOLECULAR EPIDEMIOLOGY AND EVOLUTIONARY GENETICS IN INFECTIOUS DISEASES 2012; 12:282-90. [PMID: 22119749 PMCID: PMC3293939 DOI: 10.1016/j.meegid.2011.11.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/13/2011] [Revised: 11/08/2011] [Accepted: 11/10/2011] [Indexed: 11/18/2022]
Abstract
Sulfadoxine-pyrimethamine (SP) has been widely deployed in Africa for malaria control and molecular evidence of parasite drug-resistance is prevalent. However, the temporal effects on the selection of Plasmodium falciparum are not well understood. We conducted a retrospective serial cross-sectional study between 1997 and 2006 to investigate changes in drug-resistant malaria among pregnant women delivering at a single hospital in Blantyre, Malawi. P. falciparum parasites were genotyped for parasite clone multiplicity and drug-resistance mutations, and the strength of selection upon mutant genotypes was quantified. Five mutations in the dihydrofolate reductase and dihydropteroate synthase genes began at moderate frequencies and achieved fixation by 2005; the frequency of the highly-SP-resistant "quintuple mutant" haplotype increased from 19% to 100%. The selective advantage of alleles and haplotypes were quantified with selection coefficients: Selection was positive on all mutant alleles and haplotypes associated with SP resistance, and the relative fitness of the quintuple mutant haplotype was 0.139 (95% C.I. 0.067-0.211), indicating a substantial positive selective advantage. Mutations that confer higher levels of resistance to SP did not emerge. SP-resistant haplotypes were rapidly selected for and fixed in P. falciparum populations infecting pregnant women while SP was widely deployed in Malawi. These results underscore the pressing need for new preventive measures for pregnancy-associated malaria and provide a real-world model of the selection landscape malaria parasites.
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Affiliation(s)
- Steve M Taylor
- Department of Epidemiology, Gillings School of Global Public Health, University of North Carolina, Chapel Hill, NC 27599, USA.
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Recent clinical and molecular insights into emerging artemisinin resistance in Plasmodium falciparum. Curr Opin Infect Dis 2012; 24:570-7. [PMID: 22001944 DOI: 10.1097/qco.0b013e32834cd3ed] [Citation(s) in RCA: 96] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
PURPOSE OF REVIEW Artemisinin-based combination therapies (ACTs) have been deployed globally with remarkable success for more than 10 years without having lost their malaria treatment efficacy. However, recent reports from the Thai-Cambodian border reveal evidence of emerging resistance to artemisinins. The latest published clinical and molecular findings are summarized herein. RECENT FINDINGS Clinical studies have identified delayed parasite clearance time as the most robust marker of artemisinin resistance. Resistance has only been documented from South-east Asia and has been observed in isolates that show no significant decrease in drug susceptibility in vitro. Genetic investigations have yet to uncover robust molecular markers. In-vitro studies have identified parasite quiescence or dormancy mechanisms that protect early 'ring-stage' intra-erythrocytic parasites against short-term artemisinin exposure. This might be achieved by reducing the rate of hemoglobin degradation, important for artemisinin bioactivation. SUMMARY Should ACTs fail, no suitable alternatives exist as first-line treatments of P. falciparum malaria. Intensified efforts are essential to monitor the spread of resistance, define therapeutic and operational strategies to counter its impact, and understand its molecular basis. Success in these areas is critical to ensuring that recent gains in reducing the burden of malaria are not lost.
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Huijben S, Sim DG, Nelson WA, Read AF. The fitness of drug-resistant malaria parasites in a rodent model: multiplicity of infection. J Evol Biol 2011; 24:2410-22. [PMID: 21883612 PMCID: PMC3304104 DOI: 10.1111/j.1420-9101.2011.02369.x] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
Abstract
Malaria infections normally consist of more than one clonally replicating lineage. Within-host interactions between sensitive and resistant parasites can have profound effects on the evolution of drug resistance. Here, using the Plasmodium chabaudi mouse malaria model, we ask whether the costs and benefits of resistance are affected by the number of co-infecting strains competing with a resistant clone. We found strong competitive suppression of resistant parasites in untreated infections and marked competitive release following treatment. The magnitude of competitive suppression depended on competitor identity. However, there was no overall effect of the diversity of susceptible parasites on the extent of competitive suppression or release. If these findings generalize, then transmission intensity will impact on resistance evolution because of its effect on the frequency of mixed infections, not because of its effect on the distribution of clones per host. This would greatly simplify the computational problems of adequately capturing within-host ecology in models of drug resistance evolution in malaria.
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Affiliation(s)
- S Huijben
- Department of Biology, Center for Infectious Disease Dynamics, Pennsylvania State University, University Park, PA 16802, USA.
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Synthesis of artemiside and its effects in combination with conventional drugs against severe murine malaria. Antimicrob Agents Chemother 2011; 56:163-73. [PMID: 22006004 DOI: 10.1128/aac.05006-11] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023] Open
Abstract
This research describes the use of novel antimalarial combinations of the new artemisinin derivative artemiside, a 10-alkylamino artemisinin. It is a stable, highly crystalline compound that is economically prepared from dihydroartemisinin in a one-step process. Artemiside activity was more pronounced than that of any antimalarial drug in use, both in Plasmodium falciparum culture and in vivo in a murine malaria model depicting cerebral malaria (CM). In vitro high-throughput testing of artemiside combinations revealed a large number of conventional antimalarial drugs with which it was additive. Following monotherapy in mice, individual drugs reduced parasitemias to nondetectable levels. However, after a period of latency, parasites again were seen and eventually all mice became terminally ill. Treatment with individual drugs did not prevent CM in mice with recrudescent malaria, except for piperaquine at high concentrations. Even when CM was prevented, the mice developed later of severe anemia. In contrast, most of the mice treated with drug combinations survived. A combination of artemiside and mefloquine or piperaquine may confer an optimal result because of the longer half life of both conventional drugs. The use of artemiside combinations revealed a significant safety margin of the effective artemiside doses. Likewise, a combination of 1.3 mg/kg of body weight artemiside and 10 mg/kg piperaquine administered for 3 days from the seventh day postinfection was completely curative. It appears possible to increase drug concentrations in the combination therapy without reaching toxic levels. Using the drug combinations as little as 1 day before the expected death of control animals, we could prevent further parasite development and death due to CM or anemic malaria. Earlier treatment may prevent cognitive dysfunctions which might occur after recovery from CM.
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Bae B, Cobb RE, DeSieno MA, Zhao H, Nair SK. New N-acetyltransferase fold in the structure and mechanism of the phosphonate biosynthetic enzyme FrbF. J Biol Chem 2011; 286:36132-36141. [PMID: 21865168 DOI: 10.1074/jbc.m111.263533] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022] Open
Abstract
The enzyme FrbF from Streptomyces rubellomurinus has attracted significant attention due to its role in the biosynthesis of the antimalarial phosphonate FR-900098. The enzyme catalyzes acetyl transfer onto the hydroxamate of the FR-900098 precursors cytidine 5'-monophosphate-3-aminopropylphosphonate and cytidine 5'-monophosphate-N-hydroxy-3-aminopropylphosphonate. Despite the established function as a bona fide N-acetyltransferase, FrbF shows no sequence similarity to any member of the GCN5-like N-acetyltransferase (GNAT) superfamily. Here, we present the 2.0 Å resolution crystal structure of FrbF in complex with acetyl-CoA, which demonstrates a unique architecture that is distinct from those of canonical GNAT-like acetyltransferases. We also utilized the co-crystal structure to guide structure-function studies that identified the roles of putative active site residues in the acetyltransferase mechanism. The combined biochemical and structural analyses of FrbF provide insights into this previously uncharacterized family of N-acetyltransferases and also provide a molecular framework toward the production of novel N-acyl derivatives of FR-900098.
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Affiliation(s)
- Brian Bae
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Ryan E Cobb
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Matthew A DeSieno
- Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801
| | - Huimin Zhao
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Chemical and Biomolecular Engineering, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
| | - Satish K Nair
- Department of Biochemistry, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801; Department of Institute for Genomic Biology, University of Illinois at Urbana-Champaign, Urbana, Illinois 61801.
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The evolution of drug resistance and the curious orthodoxy of aggressive chemotherapy. Proc Natl Acad Sci U S A 2011; 108 Suppl 2:10871-7. [PMID: 21690376 DOI: 10.1073/pnas.1100299108] [Citation(s) in RCA: 183] [Impact Index Per Article: 14.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
The evolution of drug-resistant pathogens is a major challenge for 21st century medicine. Drug use practices vigorously advocated as resistance management tools by professional bodies, public health agencies, and medical schools represent some of humankind's largest attempts to manage evolution. It is our contention that these practices have poor theoretical and empirical justification for a broad spectrum of diseases. For instance, rapid elimination of pathogens can reduce the probability that de novo resistance mutations occur. This idea often motivates the medical orthodoxy that patients should complete drug courses even when they no longer feel sick. Yet "radical pathogen cure" maximizes the evolutionary advantage of any resistant pathogens that are present. It could promote the very evolution it is intended to retard. The guiding principle should be to impose no more selection than is absolutely necessary. We illustrate these arguments in the context of malaria; they likely apply to a wide range of infections as well as cancer and public health insecticides. Intuition is unreliable even in simple evolutionary contexts; in a social milieu where in-host competition can radically alter the fitness costs and benefits of resistance, expert opinion will be insufficient. An evidence-based approach to resistance management is required.
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Murray V, Campbell HM, Gero AM. Plasmodium falciparum: DNA sequence specificity of cisplatin and cisplatin analogues. Exp Parasitol 2011; 128:396-400. [PMID: 21616072 DOI: 10.1016/j.exppara.2011.05.002] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/28/2011] [Revised: 04/29/2011] [Accepted: 05/09/2011] [Indexed: 11/27/2022]
Abstract
In this paper, we provided evidence that cisplatin is able to form adducts with cellular DNA in Plasmodium falciparum. The DNA sequence specificity of cisplatin adduct formation was determined in trophozoite-enriched P. falciparum cells and this paper represents the first occasion that the sequence specificity of cisplatin DNA damage has been observed in malaria cells. Utilising a sub-telomeric, 692 bp repeat sequence in the P. falciparum genome, we were able to investigate the DNA adducts formed by cisplatin and five analogues. A run of eight consecutive guanines was the most prominent site of DNA damage in the malarial cells. This study suggests that the mechanism of P. falciparum cell death caused by cisplatin involves damage to DNA and hence inhibition of DNA replication and cell division.
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Affiliation(s)
- Vincent Murray
- School of Biotechnology and Biomolecular Sciences, University of New South Wales, Sydney, NSW 2052, Australia.
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Grimberg BT, Mehlotra RK. Expanding the Antimalarial Drug Arsenal-Now, But How? Pharmaceuticals (Basel) 2011; 4:681-712. [PMID: 21625331 PMCID: PMC3102560 DOI: 10.3390/ph4050681] [Citation(s) in RCA: 44] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/16/2011] [Revised: 04/09/2011] [Accepted: 04/19/2011] [Indexed: 01/24/2023] Open
Abstract
The number of available and effective antimalarial drugs is quickly dwindling. This is mainly because a number of drug resistance-associated mutations in malaria parasite genes, such as crt, mdr1, dhfr/dhps, and others, have led to widespread resistance to all known classes of antimalarial compounds. Unfortunately, malaria parasites have started to exhibit some level of resistance in Southeast Asia even to the most recently introduced class of drugs, artemisinins. While there is much need, the antimalarial drug development pipeline remains woefully thin, with little chemical diversity, and there is currently no alternative to the precious artemisinins. It is difficult to predict where the next generation of antimalarial drugs will come from; however, there are six major approaches: (i) re-optimizing the use of existing antimalarials by either replacement/rotation or combination approach; (ii) repurposing drugs that are currently used to treat other infections or diseases; (iii) chemically modifying existing antimalarial compounds; (iv) exploring natural sources; (v) large-scale screening of diverse chemical libraries; and (vi) through parasite genome-based ("targeted") discoveries. When any newly discovered effective antimalarial treatment is used by the populus, we must maintain constant vigilance for both parasite-specific and human-related factors that are likely to hamper its success. This article is neither comprehensive nor conclusive. Our purpose is to provide an overview of antimalarial drug resistance, associated parasite genetic factors (1. Introduction; 2. Emergence of artemisinin resistance in P. falciparum), and the antimalarial drug development pipeline (3. Overview of the global pipeline of antimalarial drugs), and highlight some examples of the aforementioned approaches to future antimalarial treatment. These approaches can be categorized into "short term" (4. Feasible options for now) and "long term" (5. Next generation of antimalarial treatment-Approaches and candidates). However, these two categories are interrelated, and the approaches in both should be implemented in parallel with focus on developing a successful, long-lasting antimalarial chemotherapy.
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Affiliation(s)
- Brian T. Grimberg
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; E-Mails: (B.T.G.); (R.K.M.); Tel.: +1-216-368-6328 or +1-216-368-6172, Fax: +1-216-368-4825
| | - Rajeev K. Mehlotra
- Center for Global Health and Diseases, School of Medicine, Case Western Reserve University, Cleveland, OH 44106, USA; E-Mails: (B.T.G.); (R.K.M.); Tel.: +1-216-368-6328 or +1-216-368-6172, Fax: +1-216-368-4825
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Meslin B, Zalila H, Fasel N, Picot S, Bienvenu AL. Are protozoan metacaspases potential parasite killers? Parasit Vectors 2011; 4:26. [PMID: 21356053 PMCID: PMC3058108 DOI: 10.1186/1756-3305-4-26] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/28/2010] [Accepted: 02/28/2011] [Indexed: 11/10/2022] Open
Abstract
Mechanisms concerning life or death decisions in protozoan parasites are still imperfectly understood. Comparison with higher eukaryotes has led to the hypothesis that caspase-like enzymes could be involved in death pathways. This hypothesis was reinforced by the description of caspase-related sequences in the genome of several parasites, including Plasmodium, Trypanosoma and Leishmania. Although several teams are working to decipher the exact role of metacaspases in protozoan parasites, partial, conflicting or negative results have been obtained with respect to the relationship between protozoan metacaspases and cell death. The aim of this paper is to review current knowledge of protozoan parasite metacaspases within a drug targeting perspective.
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Affiliation(s)
- Benoît Meslin
- Malaria Research Unit, University Lyon 1, 8 Avenue Rockefeller, 69373 Lyon cedex 08, France
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