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Xu R, Lin L, Jiao Z, Liang R, Guo Y, Zhang Y, Shang X, Wang Y, Wang X, Yao L, Liu S, Deng X, Yuan J, Su XZ, Li J. Deaggregation of mutant Plasmodium yoelii de-ubiquitinase UBP1 alters MDR1 localization to confer multidrug resistance. Nat Commun 2024; 15:1774. [PMID: 38413566 PMCID: PMC10899652 DOI: 10.1038/s41467-024-46006-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2023] [Accepted: 02/09/2024] [Indexed: 02/29/2024] Open
Abstract
Mutations in a Plasmodium de-ubiquitinase UBP1 have been linked to antimalarial drug resistance. However, the UBP1-mediated drug-resistant mechanism remains unknown. Through drug selection, genetic mapping, allelic exchange, and functional characterization, here we show that simultaneous mutations of two amino acids (I1560N and P2874T) in the Plasmodium yoelii UBP1 can mediate high-level resistance to mefloquine, lumefantrine, and piperaquine. Mechanistically, the double mutations are shown to impair UBP1 cytoplasmic aggregation and de-ubiquitinating activity, leading to increased ubiquitination levels and altered protein localization, from the parasite digestive vacuole to the plasma membrane, of the P. yoelii multidrug resistance transporter 1 (MDR1). The MDR1 on the plasma membrane enhances the efflux of substrates/drugs out of the parasite cytoplasm to confer multidrug resistance, which can be reversed by inhibition of MDR1 transport. This study reveals a previously unknown drug-resistant mechanism mediated by UBP1 through altered MDR1 localization and substrate transport direction in a mouse model, providing a new malaria treatment strategy.
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Affiliation(s)
- Ruixue Xu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Lirong Lin
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Zhiwei Jiao
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Rui Liang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Yazhen Guo
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Yixin Zhang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Xiaoxu Shang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Yuezhou Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Xu Wang
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Luming Yao
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Shengfa Liu
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Xianming Deng
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China
| | - Jing Yuan
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China.
| | - Xin-Zhuan Su
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, MD, 20850, USA.
| | - Jian Li
- State Key Laboratory of Cellular Stress Biology, School of Life Sciences, Faculty of Medicine and Life Sciences, Xiamen University, Xiamen, Fujian, 361102, China.
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Kaur D, Sinha S, Sehgal R. Global scenario of Plasmodium vivax occurrence and resistance pattern. J Basic Microbiol 2022; 62:1417-1428. [PMID: 36125207 DOI: 10.1002/jobm.202200316] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/01/2022] [Revised: 08/20/2022] [Accepted: 09/04/2022] [Indexed: 11/06/2022]
Abstract
Malaria caused by Plasmodium vivax is comparatively less virulent than Plasmodium falciparum, which can also lead to severe disease and death. It shows a wide geographical distribution. Chloroquine serves as a drug of choice, with primaquine as a radical cure. However, with the appearance of resistance to chloroquine and treatment has been shifted to artemisinin combination therapy followed by primaquine as a radical cure. Sulphadoxine-pyrimethamine, mefloquine, and atovaquone-proguanil are other drugs of choice in chloroquine-resistant areas, and later resistance was soon reported for these drugs also. The emergence of drug resistance serves as a major hurdle to controlling and eliminating malaria. The discovery of robust molecular markers and regular surveillance for the presence of mutations in malaria-endemic areas would serve as a helpful tool to combat drug resistance. Here, in this review, we will discuss the endemicity of P. vivax, a historical overview of antimalarial drugs, the appearance of drug resistance and molecular markers with their global distribution along with different measures taken to reduce malaria burden due to P. vivax infection and their resistance.
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Affiliation(s)
- Davinder Kaur
- Department of Medical Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Shweta Sinha
- Department of Medical Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Rakesh Sehgal
- Department of Medical Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
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Mechanistic basis for multidrug resistance and collateral drug sensitivity conferred to the malaria parasite by polymorphisms in PfMDR1 and PfCRT. PLoS Biol 2022; 20:e3001616. [PMID: 35507548 PMCID: PMC9067703 DOI: 10.1371/journal.pbio.3001616] [Citation(s) in RCA: 12] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/23/2021] [Accepted: 03/31/2022] [Indexed: 01/16/2023] Open
Abstract
Polymorphisms in the Plasmodium falciparum multidrug resistance protein 1 (pfmdr1) gene and the Plasmodium falciparum chloroquine resistance transporter (pfcrt) gene alter the malaria parasite’s susceptibility to most of the current antimalarial drugs. However, the precise mechanisms by which PfMDR1 contributes to multidrug resistance have not yet been fully elucidated, nor is it understood why polymorphisms in pfmdr1 and pfcrt that cause chloroquine resistance simultaneously increase the parasite’s susceptibility to lumefantrine and mefloquine—a phenomenon known as collateral drug sensitivity. Here, we present a robust expression system for PfMDR1 in Xenopus oocytes that enables direct and high-resolution biochemical characterizations of the protein. We show that wild-type PfMDR1 transports diverse pharmacons, including lumefantrine, mefloquine, dihydroartemisinin, piperaquine, amodiaquine, methylene blue, and chloroquine (but not the antiviral drug amantadine). Field-derived mutant isoforms of PfMDR1 differ from the wild-type protein, and each other, in their capacities to transport these drugs, indicating that PfMDR1-induced changes in the distribution of drugs between the parasite’s digestive vacuole (DV) and the cytosol are a key driver of both antimalarial resistance and the variability between multidrug resistance phenotypes. Of note, the PfMDR1 isoforms prevalent in chloroquine-resistant isolates exhibit reduced capacities for chloroquine, lumefantrine, and mefloquine transport. We observe the opposite relationship between chloroquine resistance-conferring mutations in PfCRT and drug transport activity. Using our established assays for characterizing PfCRT in the Xenopus oocyte system and in live parasite assays, we demonstrate that these PfCRT isoforms transport all 3 drugs, whereas wild-type PfCRT does not. We present a mechanistic model for collateral drug sensitivity in which mutant isoforms of PfMDR1 and PfCRT cause chloroquine, lumefantrine, and mefloquine to remain in the cytosol instead of sequestering within the DV. This change in drug distribution increases the access of lumefantrine and mefloquine to their primary targets (thought to be located outside of the DV), while simultaneously decreasing chloroquine’s access to its target within the DV. The mechanistic insights presented here provide a basis for developing approaches that extend the useful life span of antimalarials by exploiting the opposing selection forces they exert upon PfCRT and PfMDR1.
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PfMDR1 Transport Rates Assessed in Intact Isolated Plasmodium falciparum Digestive Vacuoles Reflect Functional Drug Resistance Relationship with pfmdr1 Mutations. Pharmaceuticals (Basel) 2022; 15:ph15020202. [PMID: 35215316 PMCID: PMC8875337 DOI: 10.3390/ph15020202] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2022] [Revised: 01/28/2022] [Accepted: 02/01/2022] [Indexed: 02/07/2023] Open
Abstract
Drug resistance often emerges from mutations in solute transporters. Single amino acid exchanges may alter functionality of transporters with ‘de novo’ ability to transport drugs away from their site of action. The PfMDR1 transporter (or P-glycoprotein 1) is located in the membrane of the digestive vacuole (DV), functions as an ATP-dependent pump, and transports substrates into the DV. In this study, four strains of Plasmodium falciparum, carrying various pfmdr1 gene mutations, were analysed for their transport characteristics of Fluo-4 in isolated DVs of parasites. To obtain quantitative estimates for PfMDR1 DV surface expression, PfMDR1 protein amounts on each strain’s DV membrane were evaluated by quantitative ELISA. Fluo-4, acting as a substrate for PfMDR1, was applied in DV uptake assays (‘reverse Ca2+ imaging’). Viable DVs were isolated from trophozoite stages with preserved PfMDR1 activity. This newly developed assay enabled us to measure the number of Fluo-4 molecules actively transported into isolated DVs per PfMDR1 molecule. The drug-resistant strain Dd2 presented the highest transport rates, followed by K1 and the drug-sensitive strain 3D7, compatible with their copy numbers. With this assay, an evaluation of the probability of resistance formation for newly developed drugs can be implemented in early stages of drug development.
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Erhunse N, Sahal D. Protecting future antimalarials from the trap of resistance: Lessons from artemisinin-based combination therapy (ACT) failures. J Pharm Anal 2021; 11:541-554. [PMID: 34765267 PMCID: PMC8572664 DOI: 10.1016/j.jpha.2020.07.005] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2020] [Revised: 07/19/2020] [Accepted: 07/19/2020] [Indexed: 11/01/2022] Open
Abstract
Having faced increased clinical treatment failures with dihydroartemisinin-piperaquine (DHA-PPQ), Cambodia swapped the first line artemisinin-based combination therapy (ACT) from DHA-PPQ to artesunate-mefloquine given that parasites resistant to piperaquine are susceptible to mefloquine. However, triple mutants have now emerged, suggesting that drug rotations may not be adequate to keep resistance at bay. There is, therefore, an urgent need for alternative treatment strategies to tackle resistance and prevent its spread. A proper understanding of all contributors to artemisinin resistance may help us identify novel strategies to keep artemisinins effective until new drugs become available for their replacement. This review highlights the role of the key players in artemisinin resistance, the current strategies to deal with it and suggests ways of protecting future antimalarial drugs from bowing to resistance as their predecessors did.
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Affiliation(s)
- Nekpen Erhunse
- Malaria Drug Discovery Research Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India
- Department of Biochemistry, Faculty of Life Sciences, University of Benin, Benin City, Edo-State, Nigeria
| | - Dinkar Sahal
- Malaria Drug Discovery Research Group, International Centre for Genetic Engineering and Biotechnology, New Delhi, 110067, India
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Buyon LE, Elsworth B, Duraisingh MT. The molecular basis of antimalarial drug resistance in Plasmodium vivax. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2021; 16:23-37. [PMID: 33957488 PMCID: PMC8113647 DOI: 10.1016/j.ijpddr.2021.04.002] [Citation(s) in RCA: 31] [Impact Index Per Article: 10.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 12/30/2020] [Revised: 03/31/2021] [Accepted: 04/08/2021] [Indexed: 01/07/2023]
Abstract
Plasmodium vivax is the most geographically widespread cause of human malaria and is responsible for the majority of cases outside of the African continent. While great progress has been made towards eliminating human malaria, drug resistant parasite strains pose a threat towards continued progress. Resistance has arisen to multiple antimalarials in P. vivax, including to chloroquine, which is currently the first line therapy for P. vivax in most regions. Despite its importance, an understanding of the molecular mechanisms of drug resistance in this species remains elusive, in large part due to the complex biology of P. vivax and the lack of in vitro culture. In this review, we will cover the extent and challenges of measuring clinical and in vitro drug resistance in P. vivax. We will consider the roles of candidate drug resistance genes. We will highlight the development of molecular approaches for studying P. vivax biology that provide the opportunity to validate the role of putative drug resistance mutations as well as identify novel mechanisms of drug resistance in this understudied parasite. Validated molecular determinants and markers of drug resistance are essential for the rapid and cost-effective monitoring of drug resistance in P. vivax, and will be useful for optimizing drug regimens and for informing drug policy in control and elimination settings. Drug resistance is emerging in Plasmodium vivax, an important cause of malaria. The complex biology of P. vivax and the limited range of research tools make it difficult to identify drug resistance. The molecular mechanisms of drug resistance in P. vivax remain elusive. This review highlights the extent of drug resistance, the putative mechanisms of resistance and new technologies for the study of P. vivax drug resistance.
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Affiliation(s)
- Lucas E Buyon
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, 02115, MA, USA
| | - Brendan Elsworth
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, 02115, MA, USA
| | - Manoj T Duraisingh
- Department of Immunology and Infectious Diseases, Harvard T. H. Chan School of Public Health, Boston, 02115, MA, USA.
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Expansion of a Specific Plasmodium falciparum PfMDR1 Haplotype in Southeast Asia with Increased Substrate Transport. mBio 2020; 11:mBio.02093-20. [PMID: 33262257 PMCID: PMC7733942 DOI: 10.1128/mbio.02093-20] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Global efforts to eliminate malaria depend on the continued success of artemisinin-based combination therapies (ACTs) that target Plasmodium asexual blood-stage parasites. Resistance to ACTs, however, has emerged, creating the need to define the underlying mechanisms. Mutations in the P. falciparum multidrug resistance protein 1 (PfMDR1) transporter constitute an important determinant of resistance. Applying gene editing tools combined with an analysis of a public database containing thousands of parasite genomes, we show geographic selection and expansion of a pfmdr1 gene amplification encoding the N86/184F haplotype in Southeast Asia. Parasites expressing this PfMDR1 variant possess a higher transport capacity that modulates their responses to antimalarials. These data could help tailor and optimize antimalarial drug usage in different regions where malaria is endemic by taking into account the regional prevalence of pfmdr1 polymorphisms. Artemisinin-based combination therapies (ACTs) have been vital in reducing malaria mortality rates since the 2000s. Their efficacy, however, is threatened by the emergence and spread of artemisinin resistance in Southeast Asia. The Plasmodium falciparum multidrug resistance protein 1 (PfMDR1) transporter plays a central role in parasite resistance to ACT partner drugs through gene copy number variations (CNV) and/or single nucleotide polymorphisms (SNPs). Using genomic epidemiology, we show that multiple pfmdr1 copies encoding the N86 and 184F haplotype are prevalent across Southeast Asia. Applying genome editing tools on the Southeast Asian Dd2 strain and using a surrogate assay to measure transporter activity in infected red blood cells, we demonstrate that parasites harboring multicopy N86/184F PfMDR1 have a higher Fluo-4 transport capacity compared with those expressing the wild-type N86/Y184 haplotype. Multicopy N86/184F PfMDR1 is also associated with decreased parasite susceptibility to lumefantrine. These findings provide evidence of the geographic selection and expansion of specific multicopy PfMDR1 haplotypes associated with multidrug resistance in Southeast Asia.
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Adamu A, Jada MS, Haruna HMS, Yakubu BO, Ibrahim MA, Balogun EO, Sakura T, Inaoka DK, Kita K, Hirayama K, Culleton R, Shuaibu MN. Plasmodium falciparum multidrug resistance gene-1 polymorphisms in Northern Nigeria: implications for the continued use of artemether-lumefantrine in the region. Malar J 2020; 19:439. [PMID: 33256739 PMCID: PMC7708160 DOI: 10.1186/s12936-020-03506-z] [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: 07/22/2020] [Accepted: 11/18/2020] [Indexed: 02/07/2023] Open
Abstract
Background The analysis of single nucleotide polymorphism (SNPs) in drug-resistance associated genes is a commonly used strategy for the surveillance of anti-malarial drug resistance in populations of parasites. The present study was designed and performed to provide genetic epidemiological data of the prevalence of N86Y-Y184F-D1246Y SNPs in Plasmodium falciparum multidrug resistance 1 (pfmdr1) in the malaria hotspot of Northern Nigeria. Methods Plasmodium falciparum-positive blood samples on Whatman-3MM filter papers were collected from 750 symptomatic patients from four states (Kano, Kaduna, Yobe and Adamawa) in Northern Nigeria, and genotyped via BigDye (v3.1) terminator cycle sequencing for the presence of three SNPs in pfmdr1. SNPs in pfmdr1 were used to construct NYD, NYY, NFY, NFD, YYY, YYD, YFD and YFY haplotypes, and all data were analysed using Pearson Chi square and Fisher’s exact (FE) tests. Results The prevalence of the pfmdr1 86Y allele was highest in Kaduna (12.50%, 2 = 10.50, P = 0.02), whilst the 184F allele was highest in Kano (73.10%, 2 = 13.20, P = 0.00), and the pfmdr1 1246Y allele was highest in Yobe (5.26%, 2 = 9.20, P = 0.03). The NFD haplotype had the highest prevalence of 69.81% in Kano (2 = 36.10, P = 0.00), followed by NYD with a prevalence of 49.00% in Adamawa, then YFD with prevalence of 11.46% in Kaduna. The YYY haplotype was not observed in any of the studied states. Conclusion The present study suggests that strains of P. falciparum with reduced sensitivity to the lumefantrine component of AL exist in Northern Nigeria and predominate in the North-West region.
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Affiliation(s)
- Auwal Adamu
- Department of Biochemistry, Ahmadu Bello University, Zaria, Nigeria
| | - Mahmoud Suleiman Jada
- Department of Biochemistry, Modibbo Adama University of Technology Yola, Yola, Nigeria
| | | | | | | | | | - Takaya Sakura
- Institute of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
| | - Daniel Ken Inaoka
- Institute of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
| | - Kiyoshi Kita
- Institute of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, Japan
| | - Kenji Hirayama
- Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
| | - Richard Culleton
- Department of Molecular Parasitology, Proteo-Science Center, Ehime University, Ehime, Japan
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Dossou-Yovo LR, Ntoumi F, Koukouikila-Koussounda F, Vouvoungui JC, Adedoja A, Nderu D, Velavan TP, Lenga A. Molecular surveillance of the Pfmdr1 N86Y allele among Congolese pregnant women with asymptomatic malaria. Malar J 2020; 19:178. [PMID: 32384930 PMCID: PMC7206803 DOI: 10.1186/s12936-020-03246-0] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2019] [Accepted: 04/26/2020] [Indexed: 12/24/2022] Open
Abstract
Background Malaria in pregnancy is associated with considerable morbidity and mortality. Regular surveillance of artemisinin-based combination therapy tolerance, or molecular makers of resistance, is vital for effective malaria treatment, control and eradication programmes. Plasmodium falciparum multiple drug resistance-1 gene (Pfmdr1) N86Y mutation is associated with reduced susceptibility to lumefantrine. This study assessed the prevalence of Pfmdr1 N86Y in Brazzaville, Republic of Congo. Methods A total 1001 of P. falciparum-infected blood samples obtained from asymptomatic malaria pregnant women having a normal child delivery at the Madibou Integrated Health Centre were analysed. Pfmdr1 N86Y genotyping was conducted using PCR-restriction fragment length polymorphism. Results The wild type Pfmdr1 N86 allele was predominant (> 68%) in this study, whereas a few isolates carrying the either the mutant allele (Pfmdr1 86Y) alone or both alleles (mixed genotype). The dominance of the wildtype allele (pfmdr1 N86) indicates the plausible decline P. falciparum susceptibility to lumefantrine. Conclusion This study gives an update on the prevalence of Pfmdr1 N86Y alleles in Brazzaville, Republic of Congo. It also raises concern on the imminent emergence of resistance against artemether–lumefantrine in this setting. This study underscores the importance to regular artemether–lumefantrine efficacy monitoring to inform the malaria control programme of the Republic of Congo.
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Affiliation(s)
- Louis Regis Dossou-Yovo
- Ecole Normale Supérieure, Marien Ngouabi University, Brazzaville, Republic of Congo.,Congolese Foundation for Medical Research, Brazzaville, Republic of Congo
| | - Francine Ntoumi
- Congolese Foundation for Medical Research, Brazzaville, Republic of Congo. .,Faculty of Science and Technology, Marien Ngouabi University, Brazzaville, Republic of Congo. .,Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany.
| | - Felix Koukouikila-Koussounda
- Congolese Foundation for Medical Research, Brazzaville, Republic of Congo.,Faculty of Science and Technology, Marien Ngouabi University, Brazzaville, Republic of Congo
| | | | - Ayodele Adedoja
- Congolese Foundation for Medical Research, Brazzaville, Republic of Congo
| | - David Nderu
- School of Health Sciences, Kirinyaga University, Kerugoya, Kenya.,Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
| | - Thirumalaisamy P Velavan
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany.,Vietnamese-German Center for Medical Research (VG-CARE), Hanoi, Vietnam.,Faculty of Medicine, Duy Tan University, Da Nang, Vietnam
| | - Arsène Lenga
- Faculty of Science and Technology, Marien Ngouabi University, Brazzaville, Republic of Congo
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Valenzuela G, Castro LE, Valencia-Zamora J, Vera-Arias CA, Rohrbach P, Sáenz FE. Genotypes and phenotypes of resistance in Ecuadorian Plasmodium falciparum. Malar J 2019; 18:415. [PMID: 31822269 PMCID: PMC6905098 DOI: 10.1186/s12936-019-3044-z] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2019] [Accepted: 11/28/2019] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Malaria continues to be endemic in the coast and Amazon regions of Ecuador. Clarifying current Plasmodium falciparum resistance in the country will support malaria elimination efforts. In this study, Ecuadorian P. falciparum parasites were analysed to determine their drug resistance genotypes and phenotypes. METHODS Molecular analyses were performed to search for mutations in known resistance markers (Pfcrt, Pfdhfr, Pfdhps, Pfmdr1, k13). Pfmdr1 copy number was determined by qPCR. PFMDR1 transporter activity was characterized in live parasites using live cell imaging in combination with the Fluo-4 transport assay. Chloroquine, quinine, lumefantrine, mefloquine, dihydroartemisinin, and artemether sensitivities were measured by in vitro assays. RESULTS The majority of samples from this study presented the CVMNT genotype for Pfcrt (72-26), NEDF SDFD mutations in Pfmdr1 and wild type genotypes for Pfdhfr, Pfdhps and k13. The Ecuadorian P. falciparum strain ESM-2013 showed in vitro resistance to chloroquine, but sensitivity to quinine, lumefantrine, mefloquine, dihydroartemisinin and artemether. In addition, transport of the fluorochrome Fluo-4 from the cytosol into the digestive vacuole (DV) of the ESM-2013 strain was minimally detected in the DV. All analysed samples revealed one copy of Pfmdr1. CONCLUSION This study indicates that Ecuadorian parasites presented the genotype and phenotype for chloroquine resistance and were found to be sensitive to SP, artemether-lumefantrine, quinine, mefloquine, and dihydroartemisinin. The results suggest that the current malaria treatment employed in the country remains effective. This study clarifies the status of anti-malarial resistance in Ecuador and informs the P. falciparum elimination campaigns in the country.
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Affiliation(s)
- Gabriela Valenzuela
- Centro de Investigación para la Salud en América Latina, Facultad de Ciencias Exactas y Naturales, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre 1076, Apartado, 17-01-2184, Quito, Ecuador
| | | | | | - Claudia A Vera-Arias
- Centro de Investigación para la Salud en América Latina, Facultad de Ciencias Exactas y Naturales, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre 1076, Apartado, 17-01-2184, Quito, Ecuador
| | - Petra Rohrbach
- Institute of Parasitology, McGill University, Montreal, Canada
| | - Fabián E Sáenz
- Centro de Investigación para la Salud en América Latina, Facultad de Ciencias Exactas y Naturales, Pontificia Universidad Católica del Ecuador, Av. 12 de Octubre 1076, Apartado, 17-01-2184, Quito, Ecuador.
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Reiling SJ, Rohrbach P. Uptake of a fluorescently tagged chloroquine analogue is reduced in CQ-resistant compared to CQ-sensitive Plasmodium falciparum parasites. Malar J 2019; 18:342. [PMID: 31590674 PMCID: PMC6781371 DOI: 10.1186/s12936-019-2980-y] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2019] [Accepted: 09/28/2019] [Indexed: 11/11/2022] Open
Abstract
Background Chloroquine (CQ) was the drug of choice for decades in the treatment of falciparum malaria until resistance emerged. CQ is suggested to accumulate in the parasite’s digestive vacuole (DV), where it unfolds its anti-malarial properties. Discrepancies of CQ accumulation in CQ-sensitive (CQS) and CQ-resistant (CQR) strains are thought to play a significant role in drug susceptibility. Analysis of CQ transport and intracellular localization using a fluorescently tagged CQ analogue could provide much needed information to distinguish susceptible from resistant parasite strains. The fluorescently tagged CQ analogue LynxTag-CQ™GREEN (CQGREEN) is commercially available and was assessed for its suitability. Methods IC50 values were determined for both CQ and CQGREEN in two CQS and two CQR Plasmodium falciparum strains. Buffer solutions with varying pH were used to determine pH-dependent localization of CQGREEN in infected red blood cells. Before CQS or CQR parasites were exposed to different pH buffers, they were pre-loaded with varying concentrations of CQGREEN for up to 7 h. Intracellular accumulation was analysed using live cell confocal microscopy. CQGREEN uptake rates were determined for the cytosol and DV in the presence and absence of verapamil. Results In CQS strains, twofold higher IC50 values were determined for the CQGREEN analogue compared to CQ. No significant differences in IC50 values were observed in CQR strains. Addition of verapamil reversed drug resistance of CQR strains to both CQ and CQGREEN. Live cell imaging revealed that CQGREEN fluorescence was mainly seen in the cytosol of most parasites, independent of the concentration used. Incubation periods of up to 7 h did not influence intracellular localization of CQGREEN. Nevertheless, CQGREEN uptake rates in CQR strains were reduced by 50% compared to CQS strains. Conclusion Although fluorescence of CQGREEN was mainly seen in the cytosol of parasites, IC50 assays showed comparable efficacy of CQGREEN and CQ in parasite killing of CQS and CQR strains. Reduced uptake rates of CQGREEN in CQR strains compared to CQS strains indicate parasite-specific responses to CQGREEN exposure. The data contains valuable information when CQGREEN is used as an analogue for CQ.
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Affiliation(s)
- Sarah J Reiling
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Montreal, QC, H9X-3V9, Canada
| | - Petra Rohrbach
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue, Montreal, QC, H9X-3V9, Canada.
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12
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Mason DJ, Eastman RT, Lewis RPI, Stott IP, Guha R, Bender A. Using Machine Learning to Predict Synergistic Antimalarial Compound Combinations With Novel Structures. Front Pharmacol 2018; 9:1096. [PMID: 30333748 PMCID: PMC6176478 DOI: 10.3389/fphar.2018.01096] [Citation(s) in RCA: 21] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/02/2018] [Accepted: 09/07/2018] [Indexed: 01/28/2023] Open
Abstract
The parasite Plasmodium falciparum is the most lethal species of Plasmodium to cause serious malaria infection in humans, and with resistance developing rapidly novel treatment modalities are currently being sought, one of which being combinations of existing compounds. The discovery of combinations of antimalarial drugs that act synergistically with one another is hence of great importance; however an exhaustive experimental screen of large drug space in a pairwise manner is not an option. In this study we apply our machine learning approach, Combination Synergy Estimation (CoSynE), which can predict novel synergistic drug interactions using only prior experimental combination screening data and knowledge of compound molecular structures, to a dataset of 1,540 antimalarial drug combinations in which 22.2% were synergistic. Cross validation of our model showed that synergistic CoSynE predictions are enriched 2.74 × compared to random selection when both compounds in a predicted combination are known from other combinations among the training data, 2.36 × when only one compound is known from the training data, and 1.5 × for entirely novel combinations. We prospectively validated our model by making predictions for 185 combinations of 23 entirely novel compounds. CoSynE predicted 20 combinations to be synergistic, which was experimentally validated for nine of them (45%), corresponding to an enrichment of 1.70 × compared to random selection from this prospective data set. Such enrichment corresponds to a 41% reduction in experimental effort. Interestingly, we found that pairwise screening of the compounds CoSynE individually predicted to be synergistic would result in an enrichment of 1.36 × compared to random selection, indicating that synergy among compound combinations is not a random event. The nine novel and correctly predicted synergistic compound combinations mainly (where sufficient bioactivity information is available) consist of efflux or transporter inhibitors (such as hydroxyzine), combined with compounds exhibiting antimalarial activity alone (such as sorafenib, apicidin, or dihydroergotamine). However, not all compound synergies could be rationalized easily in this way. Overall, this study highlights the potential for predictive modeling to expedite the discovery of novel drug combinations in fight against antimalarial resistance, while the underlying approach is also generally applicable.
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Affiliation(s)
- Daniel J Mason
- Department of Chemistry, Centre for Molecular Informatics, University of Cambridge, Cambridge, United Kingdom.,Healx Ltd., Cambridge, United Kingdom
| | - Richard T Eastman
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD, United States
| | - Richard P I Lewis
- Department of Chemistry, Centre for Molecular Informatics, University of Cambridge, Cambridge, United Kingdom
| | - Ian P Stott
- Unilever Research and Development, Wirral, United Kingdom
| | - Rajarshi Guha
- Division of Preclinical Innovation, National Center for Advancing Translational Sciences, National Institutes of Health, Rockville, MD, United States
| | - Andreas Bender
- Department of Chemistry, Centre for Molecular Informatics, University of Cambridge, Cambridge, United Kingdom
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13
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Reiling SJ, Krohne G, Friedrich O, Geary TG, Rohrbach P. Chloroquine exposure triggers distinct cellular responses in sensitive versus resistant Plasmodium falciparum parasites. Sci Rep 2018; 8:11137. [PMID: 30042399 PMCID: PMC6057915 DOI: 10.1038/s41598-018-29422-6] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/17/2018] [Accepted: 07/06/2018] [Indexed: 11/25/2022] Open
Abstract
Chloroquine (CQ) treatment failure in Plasmodium falciparum parasites has been documented for decades, but the pharmacological explanation of this phenotype is not fully understood. Current concepts attribute CQ resistance to reduced accumulation of the drug at a given external CQ concentration ([CQ]ex) in resistant compared to sensitive parasites. The implication of this explanation is that the mechanisms of CQ-induced toxicity in resistant and sensitive strains are similar once lethal internal concentrations have been reached. To test this hypothesis, we investigated the mechanism of CQ-induced toxicity in CQ-sensitive (CQS) versus CQ-resistant (CQR) parasites by analyzing the time-course of cellular responses in these strains after exposure to varying [CQ]ex as determined in 72 h toxicity assays. Parasite killing was delayed in CQR parasites for up to 10 h compared to CQS parasites when exposed to equipotent [CQ]ex. In striking contrast, brief exposure (1 h) to lethal [CQ]ex in CQS but not CQR parasites caused the appearance of hitherto undescribed hemozoin (Hz)-containing compartments in the parasite cytosol. Hz-containing compartments were very rarely observed in CQR parasites even after CQ exposures sufficient to cause irreversible cell death. These findings challenge current concepts that CQ killing of malaria parasites is solely concentration-dependent, and instead suggest that CQS and CQR strains fundamentally differ in the consequences of CQ exposure.
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Affiliation(s)
- Sarah J Reiling
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue (Montréal), Québec, Canada
| | - Georg Krohne
- Theodor Boveri Institute, Biocenter, University of Würzburg, Würzburg, Germany
| | - Oliver Friedrich
- Institute of Medical Biotechnology, Friedrich-Alexander University of Erlangen-Nürnberg, Erlangen, Germany
| | - Timothy G Geary
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue (Montréal), Québec, Canada
| | - Petra Rohrbach
- Institute of Parasitology, McGill University, Ste. Anne de Bellevue (Montréal), Québec, Canada.
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14
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Vanaerschot M, Lucantoni L, Li T, Combrinck JM, Ruecker A, Kumar TRS, Rubiano K, Ferreira PE, Siciliano G, Gulati S, Henrich PP, Ng CL, Murithi JM, Corey VC, Duffy S, Lieberman OJ, Veiga MI, Sinden RE, Alano P, Delves MJ, Lee Sim K, Winzeler EA, Egan TJ, Hoffman SL, Avery VM, Fidock DA. Hexahydroquinolines are antimalarial candidates with potent blood-stage and transmission-blocking activity. Nat Microbiol 2017. [PMID: 28808258 DOI: 10.1038/s41564-017-0007–4] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
Antimalarial compounds with dual therapeutic and transmission-blocking activity are desired as high-value partners for combination therapies. Here, we report the identification and characterization of hexahydroquinolines (HHQs) that show low nanomolar potency against both pathogenic and transmissible intra-erythrocytic forms of the malaria parasite Plasmodium falciparum. This activity translates into potent transmission-blocking potential, as shown by in vitro male gamete formation assays and reduced oocyst infection and prevalence in Anopheles mosquitoes. In vivo studies illustrated the ability of lead HHQs to suppress Plasmodium berghei blood-stage parasite proliferation. Resistance selection studies, confirmed by CRISPR-Cas9-based gene editing, identified the digestive vacuole membrane-spanning transporter PfMDR1 (P. falciparum multidrug resistance gene-1) as a determinant of parasite resistance to HHQs. Haemoglobin and haem fractionation assays suggest a mode of action that results in reduced haemozoin levels and might involve inhibition of host haemoglobin uptake into intra-erythrocytic parasites. Furthermore, parasites resistant to HHQs displayed increased susceptibility to several first-line antimalarial drugs, including lumefantrine, confirming that HHQs have a different mode of action to other antimalarials drugs for which PfMDR1 is known to confer resistance. This work evokes therapeutic strategies that combine opposing selective pressures on this parasite transporter as an approach to countering the emergence and transmission of multidrug-resistant P. falciparum malaria.
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Affiliation(s)
- Manu Vanaerschot
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Leonardo Lucantoni
- Discovery Biology, Griffith Institute for Drug Discovery, Griffith University, Nathan, 4111, Queensland, Australia
| | - Tao Li
- Sanaria Inc., Rockville, MD, 20852, USA
| | - Jill M Combrinck
- Division of Pharmacology, Department of Medicine, University of Cape Town, Cape Town, 7925, South Africa
| | - Andrea Ruecker
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK.,Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10400, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7FZ, UK
| | - T R Santha Kumar
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Kelly Rubiano
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Pedro E Ferreira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, 4710-057, Braga, Portugal
| | - Giulia Siciliano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Sonia Gulati
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Philipp P Henrich
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Caroline L Ng
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - James M Murithi
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Victoria C Corey
- University of California, San Diego, School of Medicine, La Jolla, CA, 92093, USA
| | - Sandra Duffy
- Discovery Biology, Griffith Institute for Drug Discovery, Griffith University, Nathan, 4111, Queensland, Australia
| | - Ori J Lieberman
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - M Isabel Veiga
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, 4710-057, Braga, Portugal
| | - Robert E Sinden
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Michael J Delves
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | | | - Elizabeth A Winzeler
- University of California, San Diego, School of Medicine, La Jolla, CA, 92093, USA
| | - Timothy J Egan
- Department of Chemistry, University of Cape Town, Cape Town, 7700, South Africa
| | | | - Vicky M Avery
- Discovery Biology, Griffith Institute for Drug Discovery, Griffith University, Nathan, 4111, Queensland, Australia
| | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA. .,Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, NY, 10032, USA.
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15
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Vanaerschot M, Lucantoni L, Li T, Combrinck JM, Ruecker A, Kumar TRS, Rubiano K, Ferreira PE, Siciliano G, Gulati S, Henrich PP, Ng CL, Murithi JM, Corey VC, Duffy S, Lieberman OJ, Veiga MI, Sinden RE, Alano P, Delves MJ, Lee Sim K, Winzeler EA, Egan TJ, Hoffman SL, Avery VM, Fidock DA. Hexahydroquinolines are antimalarial candidates with potent blood-stage and transmission-blocking activity. Nat Microbiol 2017; 2:1403-1414. [PMID: 28808258 DOI: 10.1038/s41564-017-0007-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/18/2016] [Accepted: 07/11/2017] [Indexed: 12/21/2022]
Abstract
Antimalarial compounds with dual therapeutic and transmission-blocking activity are desired as high-value partners for combination therapies. Here, we report the identification and characterization of hexahydroquinolines (HHQs) that show low nanomolar potency against both pathogenic and transmissible intra-erythrocytic forms of the malaria parasite Plasmodium falciparum. This activity translates into potent transmission-blocking potential, as shown by in vitro male gamete formation assays and reduced oocyst infection and prevalence in Anopheles mosquitoes. In vivo studies illustrated the ability of lead HHQs to suppress Plasmodium berghei blood-stage parasite proliferation. Resistance selection studies, confirmed by CRISPR-Cas9-based gene editing, identified the digestive vacuole membrane-spanning transporter PfMDR1 (P. falciparum multidrug resistance gene-1) as a determinant of parasite resistance to HHQs. Haemoglobin and haem fractionation assays suggest a mode of action that results in reduced haemozoin levels and might involve inhibition of host haemoglobin uptake into intra-erythrocytic parasites. Furthermore, parasites resistant to HHQs displayed increased susceptibility to several first-line antimalarial drugs, including lumefantrine, confirming that HHQs have a different mode of action to other antimalarials drugs for which PfMDR1 is known to confer resistance. This work evokes therapeutic strategies that combine opposing selective pressures on this parasite transporter as an approach to countering the emergence and transmission of multidrug-resistant P. falciparum malaria.
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Affiliation(s)
- Manu Vanaerschot
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Leonardo Lucantoni
- Discovery Biology, Griffith Institute for Drug Discovery, Griffith University, Nathan, 4111, Queensland, Australia
| | - Tao Li
- Sanaria Inc., Rockville, MD, 20852, USA
| | - Jill M Combrinck
- Division of Pharmacology, Department of Medicine, University of Cape Town, Cape Town, 7925, South Africa
| | - Andrea Ruecker
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK.,Mahidol-Oxford Tropical Medicine Research Unit, Faculty of Tropical Medicine, Mahidol University, Bangkok, 10400, Thailand.,Centre for Tropical Medicine and Global Health, Nuffield Department of Medicine, University of Oxford, Oxford, OX3 7FZ, UK
| | - T R Santha Kumar
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Kelly Rubiano
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Pedro E Ferreira
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, 4710-057, Braga, Portugal
| | - Giulia Siciliano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Sonia Gulati
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Philipp P Henrich
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Caroline L Ng
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - James M Murithi
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - Victoria C Corey
- University of California, San Diego, School of Medicine, La Jolla, CA, 92093, USA
| | - Sandra Duffy
- Discovery Biology, Griffith Institute for Drug Discovery, Griffith University, Nathan, 4111, Queensland, Australia
| | - Ori J Lieberman
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA
| | - M Isabel Veiga
- Life and Health Sciences Research Institute (ICVS), School of Medicine, University of Minho, 4710-057, Braga, Portugal
| | - Robert E Sinden
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, 00161, Rome, Italy
| | - Michael J Delves
- Department of Life Sciences, Imperial College, London, SW7 2AZ, UK
| | | | - Elizabeth A Winzeler
- University of California, San Diego, School of Medicine, La Jolla, CA, 92093, USA
| | - Timothy J Egan
- Department of Chemistry, University of Cape Town, Cape Town, 7700, South Africa
| | | | - Vicky M Avery
- Discovery Biology, Griffith Institute for Drug Discovery, Griffith University, Nathan, 4111, Queensland, Australia
| | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, 10032, USA. .,Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, NY, 10032, USA.
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16
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Change in molecular weight due to important pfatp6 and pfmdr1 polymorphisms and susceptibility to antimalarial drug: Possible role of epigenetic phenomenon. Asian Pac J Trop Biomed 2017. [DOI: 10.1016/j.apjtb.2016.12.006] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
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17
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Parallel inhibition of amino acid efflux and growth of erythrocytic Plasmodium falciparum by mefloquine and non-piperidine analogs: Implication for the mechanism of antimalarial action. Bioorg Med Chem Lett 2016; 26:4846-4850. [DOI: 10.1016/j.bmcl.2016.08.005] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/28/2016] [Revised: 08/01/2016] [Accepted: 08/02/2016] [Indexed: 11/18/2022]
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