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Vinayak S, Alam MT, Mixson-Hayden T, McCollum AM, Sem R, Shah NK, Lim P, Muth S, Rogers WO, Fandeur T, Barnwell JW, Escalante AA, Wongsrichanalai C, Ariey F, Meshnick SR, Udhayakumar V. Origin and evolution of sulfadoxine resistant Plasmodium falciparum. PLoS Pathog 2010; 6:e1000830. [PMID: 20360965 PMCID: PMC2847944 DOI: 10.1371/journal.ppat.1000830] [Citation(s) in RCA: 94] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2009] [Accepted: 02/22/2010] [Indexed: 11/29/2022] Open
Abstract
The Thailand-Cambodia border is the epicenter for drug-resistant falciparum malaria. Previous studies have shown that chloroquine (CQ) and pyrimethamine resistance originated in this region and eventually spread to other Asian countries and Africa. However, there is a dearth in understanding the origin and evolution of dhps alleles associated with sulfadoxine resistance. The present study was designed to reveal the origin(s) of sulfadoxine resistance in Cambodia and its evolutionary relationship to African and South American dhps alleles. We sequenced 234 Cambodian Plasmodium falciparum isolates for the dhps codons S436A/F, A437G, K540E, A581G and A613S/T implicated in sulfadoxine resistance. We also genotyped 10 microsatellite loci around dhps to determine the genetic backgrounds of various alleles and compared them with the backgrounds of alleles prevalent in Africa and South America. In addition to previously known highly-resistant triple mutant dhps alleles SGEGA and AGEAA (codons 436, 437, 540, 581, 613 are sequentially indicated), a large proportion of the isolates (19.3%) contained a 540N mutation in association with 437G/581G yielding a previously unreported triple mutant allele, SGNGA. Microsatellite data strongly suggest the strength of selection was greater on triple mutant dhps alleles followed by the double and single mutants. We provide evidence for at least three independent origins for the double mutants, one each for the SGKGA, AGKAA and SGEAA alleles. Our data suggest that the triple mutant allele SGEGA and the novel allele SGNGA have common origin on the SGKGA background, whereas the AGEAA triple mutant was derived from AGKAA on multiple, albeit limited, genetic backgrounds. The SGEAA did not share haplotypes with any of the triple mutants. Comparative analysis of the microsatellite haplotypes flanking dhps alleles from Cambodia, Kenya, Cameroon and Venezuela revealed an independent origin of sulfadoxine resistant alleles in each of these regions. Widespread resistance to chloroquine (CQ) and sulfadoxine-pyrimethamine (SP), the two least expensive and widely available antimalarial drugs, has become a major global public health challenge. It is known that point mutations in Plasmodium falciparum crt, dhfr and dhps genes contribute to resistance to CQ, pyrimethamine and sulfadoxine, respectively. CQ and pyrimethamine resistance spread to Africa and Asia from a few founding mutant lineages originating from the Thailand-Cambodia border. Here, we define the origins of dhps alleles in Cambodia and their relationships to African and South American counterparts. Three different triple mutant alleles including a novel allele comprised of 437G, 540N, and 581G mutations (S436G437N540G581A613) were found in Cambodia as opposed to a single triple mutant allele in South America and two common double mutant alleles in Africa. Microsatellite data suggest strong selection operating on triple mutant alleles as compared to double and single mutants in Cambodia. We report three major independent origins for the double mutants and at least two independent origins for the highly resistant triple mutant dhps alleles in Cambodia. We also show that the resistant dhps alleles in Africa and South America have distinct origins from Cambodia. These results suggest that the evolution and spread of sulfadoxine resistance is different from CQ and pyrimethamine resistance.
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Affiliation(s)
- Sumiti Vinayak
- Atlanta Research and Education Foundation, Atlanta, Georgia, United States of America
- Malaria Branch, Division of Parasitic Diseases, National Center for Zoonotic Vector Borne and Enteric Diseases, Coordinating Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Md Tauqeer Alam
- Malaria Branch, Division of Parasitic Diseases, National Center for Zoonotic Vector Borne and Enteric Diseases, Coordinating Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Tonya Mixson-Hayden
- Malaria Branch, Division of Parasitic Diseases, National Center for Zoonotic Vector Borne and Enteric Diseases, Coordinating Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Andrea M. McCollum
- Malaria Branch, Division of Parasitic Diseases, National Center for Zoonotic Vector Borne and Enteric Diseases, Coordinating Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Rithy Sem
- National Malaria Center, Phnom Penh, Cambodia
- US Naval Medical Research Unit No. 2, Jakarta, Indonesia
| | - Naman K. Shah
- Department of Epidemiology, UNC School of Public Health, Chapel Hill, North Carolina, United States of America
| | - Pharath Lim
- Institut Pasteur in Cambodia, Phnom Penh, Cambodia
| | - Sinuon Muth
- National Malaria Center, Phnom Penh, Cambodia
| | | | - Thierry Fandeur
- Institut Pasteur, Unité d'Immunologie Moléculaire des Parasites, Paris, France
| | - John W. Barnwell
- Malaria Branch, Division of Parasitic Diseases, National Center for Zoonotic Vector Borne and Enteric Diseases, Coordinating Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
| | - Ananias A. Escalante
- School of Life Sciences, Arizona State University, Tempe, Arizona, United States of America
| | | | | | - Steven R. Meshnick
- Department of Epidemiology, UNC School of Public Health, Chapel Hill, North Carolina, United States of America
| | - Venkatachalam Udhayakumar
- Malaria Branch, Division of Parasitic Diseases, National Center for Zoonotic Vector Borne and Enteric Diseases, Coordinating Center for Infectious Diseases, Centers for Disease Control and Prevention, Atlanta, Georgia, United States of America
- * E-mail:
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Zakeri S, Afsharpad M, Ghasemi F, Raeisi A, Safi N, Butt W, Atta H, Djadid ND. Molecular surveillance of Plasmodium vivax dhfr and dhps mutations in isolates from Afghanistan. Malar J 2010; 9:75. [PMID: 20226087 PMCID: PMC2848684 DOI: 10.1186/1475-2875-9-75] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2010] [Accepted: 03/14/2010] [Indexed: 11/21/2022] Open
Abstract
Background Analysis of dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) mutations in Plasmodium vivax wild isolates has been considered to be a valuable molecular approach for mapping resistance to sulphadoxine-pyrimethamine (SP). The present study investigates the frequency of SNPs-haplotypes in the dhfr and dhps genes in P. vivax clinical isolates circulating in two malaria endemic areas in Afghanistan. Methods P. vivax clinical isolates (n = 171) were collected in two different malaria endemic regions in north-west (Herat) and east (Nangarhar) Afghanistan in 2008. All collected isolates were analysed for SNP-haplotypes at positions 13, 33, 57, 58, 61, 117 and 173 of the pvdhfr and 383 and 553 of the pvdhps genes using PCR-RFLP methods. Results All 171 examined isolates were found to carry wild-type amino acids at positions 13, 33, 57, 61 and 173, while 58R and 117N mutations were detected among 4.1% and 12.3% of Afghan isolates, respectively. Based on the size polymorphism of pvdhfr genes at repeat region, type B was the most prevalent variant among Herat (86%) and Nangarhar (88.4%) isolates. Mixed genotype infections (type A/B and A/B/C) were detected in only 2.3% (2/86) of Herat and 1.2% (1/86) of Nangarhar isolates, respectively. The combination of pvdhfr and pvdhps haplotypes among all 171 samples demonstrated six distinct haplotypes. The two most prevalent haplotypes among all examined samples were wild-type (86%) and single mutant haplotype I13P33F57S58T61N 117I173/A383A553 (6.4%). Double (I13P33S57R58T61N117I173/A383A553) and triple mutant haplotypes (I13P33S57R 58T61N117I173/G383A553) were found in 1.7% and 1.2% of Afghan isolates, respectively. This triple mutant haplotype was only detected in isolates from Herat, but in none of the Nangarhar isolates. Conclusion The present study shows a limited polymorphism in pvdhfr from Afghan isolates and provides important basic information to establish an epidemiological map of drug-resistant vivax malaria, and updating guidelines for anti-malarial policy in Afghanistan. The continuous usage of SP as first-line anti-malarial drug in Afghanistan might increase the risk of mutations in the dhfr and dhps genes in both P. vivax and Plasmodium falciparum isolates, which may lead to a complete SP resistance in the near future in this region. Therefore, continuous surveillance of P. vivax and P. falciparum molecular markers are needed to monitor the development of resistance to SP in the region.
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Affiliation(s)
- Sedigheh Zakeri
- Malaria and Vector Research Group, Biotechnology Research Center, Institut Pasteur of Iran, Pasteur Avenue, PO BOX 1316943551, Tehran, Iran.
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Dlamini SV, Beshir K, Sutherland CJ. Markers of anti-malarial drug resistance in Plasmodium falciparum isolates from Swaziland: identification of pfmdr1-86F in natural parasite isolates. Malar J 2010; 9:68. [PMID: 20199676 PMCID: PMC2845184 DOI: 10.1186/1475-2875-9-68] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2009] [Accepted: 03/03/2010] [Indexed: 11/10/2022] Open
Abstract
Background The development of Plasmodium falciparum resistance to chloroquine (CQ) has limited its use in many malaria endemic areas of the world. However, despite recent drug policy changes to adopt the more effective artemisinin-based combination (ACT) in Africa and in the Southern African region, in 2007 Swaziland still relied on CQ as first-line anti-malarial drug. Methods Parasite DNA was amplified from P. falciparum isolates from Swaziland collected in 1999 (thick smear blood slides) and 2007 (filter paper blood spots). Markers of CQ and sulphadoxine-pyrimethamine (SP) resistance were identified by probe-based qPCR and DNA sequencing. Results Retrospective microscopy, confirmed by PCR amplification, found that only six of 252 patients treated for uncomplicated malaria in 2007 carried detectable P. falciparum. The pfcrt haplotype 72C/73V/74I/75E/76T occurred at a prevalence of 70% (n = 64) in 1999 and 83% (n = 6) in 2007. Prevalence of the pfmdr1-86N allele was 24% in 1999 and 67% in 2007. A novel substitution of phenylalanine for asparagine at codon 86 of pfmdr1 (N86F) occurred in two of 51 isolates successfully amplified from 1999. The pfmdr1-1246Y allele was common in 1999, with a prevalence of 49%, but was absent among isolates collected in 2007. The 86N/184F/1246D pfmdr1 haplotype, associated with enhanced parasite survival in patients treated with artemether-lumefantrine, comprised 8% of 1999 isolates, and 67% among 2007 isolates. The pfdhfr triple-mutant 16C/51I/59R/108N/164I haplotype associated with pyrimethamine resistance was common in both 1999 (82%, n = 34) and 2007 (50%, n = 6), as was the wild-type 431I/436S/437A/540K/581A/613A haplotype of pfdhps (100% and 93% respectively in 1999 and 2007). The quintuple-mutant haplotype pfdhfr/pfdhps-CIRNI/ISGEAA, associated with high-level resistance to SP, was rare (9%) among 1999 isolates and absent among 2007 isolates. Conclusions The prevalence of pfcrt and pfmdr1 alleles reported in this study is consistent with a parasite population under sustained CQ drug pressure. The low prevalence of dhps-437G and dhps-540E mutations (ISGEAA) and the rarity of quintuple-mutant haplotype pfdhfr/pfdhps-CIRNI/ISGEAA suggest that SP retains some efficacy in Swaziland. Anti-malarial policy changes in neighbouring countries may have had an impact on the prevalence of molecular markers of anti-malarial resistance in Swaziland, and it is hoped that this new information will add to understanding of the regional anti-malarial resistance map.
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Affiliation(s)
- Sabelo V Dlamini
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel St, London WC1E 7HT, UK
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Mixson-Hayden T, Jain V, McCollum AM, Poe A, Nagpal AC, Dash AP, Stiles JK, Udhayakumar V, Singh N. Evidence of selective sweeps in genes conferring resistance to chloroquine and pyrimethamine in Plasmodium falciparum isolates in India. Antimicrob Agents Chemother 2010; 54:997-1006. [PMID: 20038626 PMCID: PMC2826016 DOI: 10.1128/aac.00846-09] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/23/2009] [Revised: 07/17/2009] [Accepted: 12/15/2009] [Indexed: 11/20/2022] Open
Abstract
Treatment of Plasmodium falciparum is complicated by the emergence and spread of parasite resistance to many of the first-line drugs used to treat malaria. Antimalarial drug resistance has been associated with specific point mutations in several genes, suggesting that these single nucleotide polymorphisms can be useful in tracking the emergence of drug resistance. In India, P. falciparum infection can manifest itself as asymptomatic, mild, or severe malaria, with or without cerebral involvement. We tested whether chloroquine- and antifolate drug-resistant genotypes would be more commonly associated with cases of cerebral malaria than with cases of mild malaria in the province of Jabalpur, India, by genotyping the dhps, dhfr, pfmdr-1, and pfcrt genes using pyrosequencing, direct sequencing, and real-time PCR. Further, we used microsatellites surrounding the genes to determine the origins and spread of the drug-resistant genotypes in this area. Resistance to chloroquine was essentially fixed, with 95% of the isolates harboring the pfcrt K76T mutation. Resistant genotypes of dhfr, dhps, and pfmdr-1 were found in 94%, 17%, and 77% of the isolates, respectively. Drug-resistant genotypes were equally likely to be associated with cerebral malaria as with mild malaria. We found evidence of a selective sweep in pfcrt and, to a lesser degree, in dhfr, indicating high levels of resistance to chloroquine and evolving resistance to pyrimethamine. Microsatellites surrounding pfcrt indicate that the resistant genotypes (SVMNT) were most similar to those found in Papua New Guinea.
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Affiliation(s)
- Tonya Mixson-Hayden
- Malaria Branch, Division of Parasitic Diseases, Centers for Disease Control and Prevention, 4770 Buford Highway, MS F-12, Chamblee, GA 30341, USA.
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155
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Hill DA, Desai SA. Malaria parasite mutants with altered erythrocyte permeability: a new drug resistance mechanism and important molecular tool. Future Microbiol 2010; 5:81-97. [PMID: 20020831 DOI: 10.2217/fmb.09.109] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
Erythrocytes infected with plasmodia, including those that cause human malaria, have increased permeability to a diverse collection of organic and inorganic solutes. While these increases have been known for decades, their mechanistic basis was unclear until electrophysiological studies revealed flux through one or more ion channels on the infected erythrocyte membrane. Current debates have centered on the number of distinct ion channels, which channels mediate the transport of each solute and whether the channels represent parasite-encoded proteins or human channels activated after infection. This article reviews the identification of the plasmodial surface anion channel and other proposed channels with an emphasis on two distinct channel mutants generated through in vitro selection. These mutants implicate parasite genetic elements in the parasite-induced permeability, reveal an important new antimalarial drug resistance mechanism and provide tools for molecular studies. We also critically examine the technical issues relevant to the detection of ion channels by electrophysiological methods; these technical considerations have general applicability for interpreting studies of various ion channels proposed for the infected erythrocyte membrane.
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Affiliation(s)
- David A Hill
- Department of Pathobiology, University of Pennsylvania, Philadelphia, PA, USA.
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156
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Hevener KE, Yun MK, Qi J, Kerr ID, Babaoglu K, Hurdle JG, Balakrishna K, White SW, Lee RE. Structural studies of pterin-based inhibitors of dihydropteroate synthase. J Med Chem 2010; 53:166-77. [PMID: 19899766 DOI: 10.1021/jm900861d] [Citation(s) in RCA: 60] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Dihydropteroate synthase (DHPS) is a key enzyme in bacterial folate synthesis and the target of the sulfonamide class of antibacterials. Resistance and toxicities associated with sulfonamides have led to a decrease in their clinical use. Compounds that bind to the pterin binding site of DHPS, as opposed to the p-amino benzoic acid (pABA) binding site targeted by the sulfonamide agents, are anticipated to bypass sulfonamide resistance. To identify such inhibitors and map the pterin binding pocket, we have performed virtual screening, synthetic, and structural studies using Bacillus anthracis DHPS. Several compounds with inhibitory activity have been identified, and crystal structures have been determined that show how the compounds engage the pterin site. The structural studies identify the key binding elements and have been used to generate a structure-activity based pharmacophore map that will facilitate the development of the next generation of DHPS inhibitors which specifically target the pterin site.
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Affiliation(s)
- Kirk E Hevener
- Department of Pharmaceutical Sciences, University of Tennessee Health Science Center, 847 Monroe Avenue, Room 327 Johnson Building, Memphis, Tennessee 38163, USA
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Probing the roles of non-homologous insertions in the N-terminal domain of Plasmodium falciparum hydroxymethylpterin pyrophosphokinase–dihydropteroate synthase. Mol Biochem Parasitol 2009; 168:135-42. [DOI: 10.1016/j.molbiopara.2009.07.005] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/06/2009] [Revised: 06/29/2009] [Accepted: 07/09/2009] [Indexed: 11/19/2022]
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158
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Hyde JE. Mapping the origins and spread of antifolate-resistant malaria parasites. Future Microbiol 2009; 4:953-8. [PMID: 19824787 DOI: 10.2217/fmb.09.66] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Evaluation of: Pearce RJ, Pota H, Evehe MSB et al.: Multiple origins and regional dispersal of resistant dhps in African Plasmodium falciparum malaria. PLoS Med. 6(4), e1000055 (2009). Widespread resistance to current antimalarial drugs is a major factor in the extremely high levels of mortality and disabling illness that still prevail in many developing countries. It is important to understand how frequently resistant malaria parasite strains arise and their patterns of propagation and dispersal across borders and continents. By studying the DNA sequences of both the gene encoding the drug target and its flanking regions, it is possible to collect and map such data, providing a considerable asset in devising and evaluating future strategies of drug use and deployment. In this article, Pearce et al. analyze a large number of parasite samples collected over a decade from countries across Africa, allowing them to present for the first time a detailed picture of the origins and relatively recent spread of resistance to sulfa-drugs, key components of antifolate drug combinations that have been used extensively as part of the antimalarial armory.
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Affiliation(s)
- John E Hyde
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, Manchester M1 7ND, UK.
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159
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Characteristics of genetic hitchhiking around dihydrofolate reductase gene associated with pyrimethamine resistance in Plasmodium falciparum isolates from India. Antimicrob Agents Chemother 2009; 53:5173-80. [PMID: 19786603 DOI: 10.1128/aac.00045-09] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Sulfadoxine-pyrimethamine (SP) resistance in Plasmodium falciparum has been widespread across continents, causing the major hurdle of controlling malaria. Resistance is encoded mainly by point mutations in P. falciparum dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) target genes. To study the origin and evolution of pyrimethamine resistance on the Indian subcontinent, microsatellite markers flanking the pfdhfr gene were mapped. Here we describe the characteristics of genetic hitchhiking around the pfdhfr gene among 190 P. falciparum isolates. These isolates were collected from five different geographical regions of India (Uttar Pradesh, Madhya Pradesh, Assam, Orissa, and Andaman and Nicobar Islands) where malarial transmission rates and levels of drug resistance vary across regions. Among the isolates, we observed a significant reduction in genetic variation in the +/-20-kb vicinity of the mutant pfdhfr alleles due to hitchhiking. This reduction in genetic diversity was more prominent around quadruple pfdhfr alleles (heterozygosity [H(e)] = 0.23) than around double (H(e) = 0.365) and single (H(e) = 0.465) mutant alleles. Asymmetry in the selective sweep flanking the pfdhfr alleles was observed with regional isolates, emphasizing the drug usage with the parasite population. All the pfdhfr alleles share a single microsatellite haplotype and seem to have originated from a single progenitor similar to that of Southeast Asian (Thailand) pfdhfr mutants. Results of the present study also indicate that the emergence of drug-resistant alleles is a recent phenomenon in India compared to Southeast Asian countries.
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160
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Zhang GQ, Guan YY, Zheng B, Wu S, Tang LH. Molecular assessment ofPlasmodium falciparumresistance to antimalarial drugs in China. Trop Med Int Health 2009; 14:1266-71. [DOI: 10.1111/j.1365-3156.2009.02342.x] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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161
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Mita T, Tanabe K, Kita K. Spread and evolution of Plasmodium falciparum drug resistance. Parasitol Int 2009; 58:201-9. [PMID: 19393762 DOI: 10.1016/j.parint.2009.04.004] [Citation(s) in RCA: 177] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2009] [Revised: 03/25/2009] [Accepted: 04/16/2009] [Indexed: 11/19/2022]
Abstract
Worldwide spread of Plasmodium falciparum drug resistance to conventional antimalarials, chloroquine and sulfadoxine/pyrimethamine, has been imposing a serious public health problem in many endemic regions. Recent discovery of drug resistance-associated genes, pfcrt, pfmdr1, dhfr, and dhps, and applications of microsatellite markers flanking the genes have revealed the evolution of parasite resistance to these antimalarials and the geographical spread of drug resistance. Here, we review our recent knowledge of the evolution and spread of parasite resistance to chloroquine and sulfadoxine/pyrimethamine. In both antimalarials, resistance appears to be largely explained by the invasion of limited resistant lineages to many endemic regions. However, multiple, indigenous evolutionary origins of resistant lineages have also been demonstrated. Further molecular evolutionary and population genetic approaches will greatly facilitate our understanding of the evolution and spread of parasite drug resistance, and will contribute to developing strategies for better control of malaria.
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Affiliation(s)
- Toshihiro Mita
- Department of International Affairs and Tropical Medicine, Tokyo Women's Medical University, School of Medicine, 9-1 Kawada-cho, Shinjuku-ku, Tokyo 162-8666, Japan.
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Multiple origins and regional dispersal of resistant dhps in African Plasmodium falciparum malaria. PLoS Med 2009; 6:e1000055. [PMID: 19365539 PMCID: PMC2661256 DOI: 10.1371/journal.pmed.1000055] [Citation(s) in RCA: 143] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 05/30/2008] [Accepted: 02/13/2009] [Indexed: 11/19/2022] Open
Abstract
BACKGROUND Although the molecular basis of resistance to a number of common antimalarial drugs is well known, a geographic description of the emergence and dispersal of resistance mutations across Africa has not been attempted. To that end we have characterised the evolutionary origins of antifolate resistance mutations in the dihydropteroate synthase (dhps) gene and mapped their contemporary distribution. METHODS AND FINDINGS We used microsatellite polymorphism flanking the dhps gene to determine which resistance alleles shared common ancestry and found five major lineages each of which had a unique geographical distribution. The extent to which allelic lineages were shared among 20 African Plasmodium falciparum populations revealed five major geographical groupings. Resistance lineages were common to all sites within these regions. The most marked differentiation was between east and west African P. falciparum, in which resistance alleles were not only of different ancestry but also carried different resistance mutations. CONCLUSIONS Resistant dhps has emerged independently in multiple sites in Africa during the past 10-20 years. Our data show the molecular basis of resistance differs between east and west Africa, which is likely to translate into differing antifolate sensitivity. We have also demonstrated that the dispersal patterns of resistance lineages give unique insights into recent parasite migration patterns.
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163
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de Almeida A, Arez AP, Cravo PVL, do Rosário VE. Analysis of genetic mutations associated with anti-malarial drug resistance in Plasmodium falciparum from the Democratic Republic of East Timor. Malar J 2009; 8:59. [PMID: 19358729 PMCID: PMC2672086 DOI: 10.1186/1475-2875-8-59] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2008] [Accepted: 04/09/2009] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND In response to chloroquine (CQ) resistance, the policy for the first-line treatment of uncomplicated malaria in the Democratic Republic of East Timor (DRET) was changed in early 2000. The combination of sulphadoxine-pyrimethamine (SP) was then introduced for the treatment of uncomplicated falciparum malaria. METHODS Blood samples were collected in two different periods (2003-2004 and 2004-2005) from individuals attending hospitals or clinics in six districts of the DRET and checked for Plasmodium falciparum infection. 112 PCR-positive samples were inspected for genetic polymorphisms in the pfcrt, pfmdr1, pfdhfr and pfdhps genes. Different alleles were interrogated for potential associations that could be indicative of non-random linkage. RESULTS Overall prevalence of mutations associated with resistance to CQ and SP was extremely high. The mutant form of Pfcrt (76T) was found to be fixed even after five years of alleged CQ removal. There was a significant increase in the prevalence of the pfdhps 437G mutation (X2 = 31.1; p = 0.001) from the first to second survey periods. A non-random association was observed between pfdhfr51/pfdhps437 (p = 0.001) and pfdhfr 59/pfdhps 437 (p = 0.013) alleles. CONCLUSION Persistence of CQ-resistant mutants even after supposed drug withdrawal suggests one or all of the following: local P. falciparum may still be inadvertently exposed to the drug, that mutant parasites are being "imported" into the country, and/or reduced genetic diversity and low parasite transmission help maintain mutant haplotypes. The association between pfdhfr51/pfdhps437 and pfdhfr 59/pfdhps 437 alleles indicates that these are undergoing concomitant positive selection in the DRET.
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Affiliation(s)
- Afonso de Almeida
- Universidade Nacional de Timor Leste, Avenida Cidade de Lisboa, Díli, Timor Leste
- Centro de Malária e Outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal
| | - Ana Paula Arez
- Centro de Malária e Outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal
| | - Pedro VL Cravo
- Unidade de Biologia Molecular, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal
| | - Virgílio E do Rosário
- Centro de Malária e Outras Doenças Tropicais, Instituto de Higiene e Medicina Tropical, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisboa, Portugal
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164
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Garg S, Saxena V, Kanchan S, Sharma P, Mahajan S, Kochar D, Das A. Novel point mutations in sulfadoxine resistance genes of Plasmodium falciparum from India. Acta Trop 2009; 110:75-9. [PMID: 19283899 DOI: 10.1016/j.actatropica.2009.01.009] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/21/2022]
Abstract
Point mutations in the dhfr and dhps genes of Plasmodium falciparum are associated with pyrimethamine and sulfadoxine resistance respectively. In this study we have analyzed these genes from Bikaner (situated in North-West region of India), where both uncomplicated and severe manifestations of P. falciparum malaria are seen. A majority of isolates showed double mutant allele for DHFR. In contrast, the only reported mutation present in DHPS was A437G in few isolates. In addition, three novel non-synonymous mutations were observed in the PfDHPS from this region viz., S587F, N666K and C668W. The mutations at the 666 and 668 codon seem to form a bend in the big loop region of the DHPS enzyme and may affect the binding of the drug to the enzyme. Molecular docking of sulfadoxine to this mutated structure indicates reduction in its binding affinity to this enzyme.
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165
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Hayton K, Su XZ. Drug resistance and genetic mapping in Plasmodium falciparum. Curr Genet 2008; 54:223-39. [PMID: 18802698 DOI: 10.1007/s00294-008-0214-x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2008] [Revised: 08/27/2008] [Accepted: 08/28/2008] [Indexed: 11/30/2022]
Abstract
Drug resistance in malaria parasites is a serious public health burden, and resistance to most of the antimalarial drugs currently in use has been reported. A better understanding of the molecular mechanisms of drug resistance is urgently needed to slow or circumvent the spread of resistance, to allow local treatments to be deployed more effectively to prolong the life span of the current drugs, and to develop new drugs. Although mutations in genes determining resistance to drugs such as chloroquine and the antifolates have been identified, we still do not have a full understanding of the resistance mechanisms, and genes that contribute to resistance to many other drugs remain to be discovered. Genetic mapping is a powerful tool for the identification of mutations conferring drug resistance in malaria parasites because most drug-resistant phenotypes were selected within the past 60 years. High-throughput methods for genotyping large numbers of single nucleotide polymorphisms (SNPs) and microsatellites (MSs) are now available or are being developed, and genome-wide association studies for malaria traits will soon become a reality. Here we discuss strategies and issues related to mapping genes contributing to drug resistance in the human malaria parasite Plasmodium falciparum.
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Affiliation(s)
- Karen Hayton
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, 9000 Rockville Pike, Bethesda, MD 20892, USA.
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Grimberg BT, Erickson JJ, Sramkoski RM, Jacobberger JW, Zimmerman PA. Monitoring Plasmodium falciparum growth and development by UV flow cytometry using an optimized Hoechst-thiazole orange staining strategy. Cytometry A 2008; 73:546-54. [PMID: 18302186 DOI: 10.1002/cyto.a.20541] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
The complex life cycle of Plasmodium falciparum (Pf) makes it difficult to limit infections and reduce the risk of severe malaria. Improved understanding of Pf blood-stage growth and development would provide new opportunities to evaluate and interfere with successful completion of the parasite's life cycle. Cultured blood stage Pf was incubated with Hoechst 33342 (HO) and thiazole orange (TO) to stain DNA and total nucleic acids, respectively. Correlated HO and TO fluorescence emissions were then measured by flow cytometry. Complex bivariate data patterns were analyzed by manual cluster gating to quantify parasite life cycle stages. The permutations of viable staining with both reagents were tested for optimal detection of parasitized RBC (pRBC). Pf cultures were exposed to HO and TO simultaneously to achieve optimal staining of pRBC and consistent quantification of early and late stages of the replicative cycle (rings through schizonts). Staining of Pf nucleic acids allows for analysis of parasite development in the absence of fixatives, lysis, or radioactivity to enable examination of erythrocytes from parasite invasion through schizont rupture using sensitive and rapid assay procedures. Investigation of the mechanisms by which anti-malarial drugs and antibodies act against different Pf lifecycle stages will be aided by this cytometric strategy.
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Affiliation(s)
- Brian T Grimberg
- Center for Global Health and Disease, School of Medicine, Case Western Reserve University, Cleveland, Ohio 44106-7286, USA
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167
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Mayor A, Serra‐Casas E, Sanz S, Aponte J, Macete E, Mandomando I, Puyol L, Berzosa P, Dobaño C, Aide P, Sacarlal J, Benito A, Alonso P, Menéndez C. Molecular Markers of Resistance to Sulfadoxine‐Pyrimethamine during Intermittent Preventive Treatment for Malaria in Mozambican Infants. J Infect Dis 2008; 197:1737-42. [DOI: 10.1086/588144] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
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168
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Mkulama MAP, Chishimba S, Sikalima J, Rouse P, Thuma PE, Mharakurwa S. Escalating Plasmodium falciparum antifolate drug resistance mutations in Macha, rural Zambia. Malar J 2008; 7:87. [PMID: 18495008 PMCID: PMC2412897 DOI: 10.1186/1475-2875-7-87] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/05/2008] [Accepted: 05/21/2008] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND In Zambia the first-line treatment for uncomplicated malaria is artemisinin combination therapy (ACT), with artemether-lumefantrine currently being used. However, the antifolate regimen, sulphadoxine-pyrimethamine (SP), remains the treatment of choice in children weighing less than 5 kg and also in expectant mothers. SP is also the choice drug for intermittent preventive therapy in pregnancy and serves as stand-by treatment during ACT stock outs. The current study assessed the status of Plasmodium falciparum point mutations associated with antifolate drug resistance in the area around Macha. METHODS A representative sample of 2,780 residents from the vicinity of Macha was screened for malaria by microscopy. At the same time, blood was collected onto filter paper and dried for subsequent P. falciparum DNA analysis. From 188 (6.8%) individuals that were thick film-positive, a simple random sub-set of 95 P. falciparum infections were genotyped for DHFR and DHPS antifolate resistance mutations, using nested PCR and allele-specific restriction enzyme digestion. RESULTS Plasmodium falciparum field samples exhibited a high prevalence of antifolate resistance mutations, including the DHFR triple (Asn-108 + Arg-59 + Ile-51) mutant (41.3%) and DHPS double (Gly-437 + Glu-540) mutant (16%). The quintuple (DHFR triple + DHPS double) mutant was found in 4 (6.5%) of the samples. Levels of mutated parasites showed a dramatic escalation, relative to previous surveys since 1988. However, neither of the Val-16 and Thr-108 mutations, which jointly confer resistance to cycloguanil, was detectable among the human infections. The Leu-164 mutation, associated with high grade resistance to both pyrimethamine and cycloguanil, as a multiple mutant with Asn-108, Arg-59 and (or) Ile-51, was also absent. CONCLUSION This study points to escalating levels of P. falciparum antifolate resistance in the vicinity of Macha. Continued monitoring is recommended to ensure timely policy revisions before widespread resistance exacts a serious public health toll.
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Affiliation(s)
| | | | - Jay Sikalima
- The Malaria Institute at Macha, Namwala Road, Choma, Zambia
| | - Petrica Rouse
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
| | - Philip E Thuma
- The Malaria Institute at Macha, Namwala Road, Choma, Zambia
| | - Sungano Mharakurwa
- The Malaria Institute at Macha, Namwala Road, Choma, Zambia
- Johns Hopkins Bloomberg School of Public Health, Baltimore, Maryland, USA
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169
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Dihydropteroate synthase from Streptococcus pneumoniae: structure, ligand recognition and mechanism of sulfonamide resistance. Biochem J 2008; 412:379-88. [DOI: 10.1042/bj20071598] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
Abstract
DHPS (dihydropteroate synthase) catalyses an essential step in the biosynthesis of folic acid and is the target for the sulfonamide group of antimicrobial drugs. In the present paper we report two crystal structures of DHPS from the respiratory pathogen Streptococcus pneumoniae: the apoenzyme at 1.8 Å (1 Å=0.1 nm) resolution and a complex with DHPP (6-hydroxymethyl-7,8-dihydropterin monophosphate) at 2.4 Å resolution. The enzyme forms a α/β barrel structure, with a highly conserved binding pocket for recognition of the pterin substrate, DHPPP (6-hydroxymethyl-7,8-dihydropterin pyrophosphate). There is a fixed order of substrate binding: DHPPP binds first, followed by the second substrate, pABA (p-aminobenzoic acid). Binding of PPi also allows the enzyme to recognize pABA or sulfonamide drugs, which act as pABA analogues. Using equilibrium and pre-steady state kinetic fluorescence measurements, we show that the on-rate for DHPPP binding to the enzyme is relatively low (2.6×105 M−1·s−1) and propose that binding of this substrate induces a large scale movement of the second loop in the enzyme structure to participate in the formation of the pABA-binding site. Two mutations which confer resistance to sulfonamide drugs do not affect DHPPP binding, but have a substantial effect on pABA and sulfonamide recognition. The results show that binding of DHPPP and pABA are separate distinguishable events in the reaction cycle, and that mutations which confer resistance to sulfonamide drugs act exclusively on the second step in the binding process.
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Changes in the plasmodial surface anion channel reduce leupeptin uptake and can confer drug resistance in Plasmodium falciparum-infected erythrocytes. Antimicrob Agents Chemother 2008; 52:2346-54. [PMID: 18443109 DOI: 10.1128/aac.00057-08] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cysteine protease inhibitors kill malaria parasites and are being pursued for development as antimalarial agents. Because they have multiple targets within bloodstream-stage parasites, workers have assumed that resistance to these inhibitors would not be acquired easily. In the present study, we used in vitro selection to generate a parasite resistant to growth inhibition by leupeptin, a broad-profile cysteine and serine protease inhibitor. Resistance was not associated with upregulation of cysteine protease activity, reduced leupeptin sensitivity of this activity, or expression level changes for putative cysteine or serine proteases in the parasite genome. Instead, it was associated with marked changes in the plasmodial surface anion channel (PSAC), an ion channel on infected erythrocytes that functions in nutrient and bulky organic solute uptake. Osmotic fragility measurements, electrophysiological recordings, and leupeptin uptake studies revealed selective reductions in organic solute permeability via PSAC, altered single-channel gating, and reduced inhibitor affinity. These changes yielded significantly reduced leupeptin uptake and could fully account for the acquired resistance. PSAC represents a novel route for the uptake of bulky hydrophilic compounds acting against intraerythrocytic parasite targets. Drug development based on such compounds should proceed cautiously in light of possible resistance development though the selection of PSAC mutants.
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High frequency of Plasmodium falciparum CICNI/SGEAA and CVIET haplotypes without association with resistance to sulfadoxine/pyrimethamine and chloroquine combination in the Daraweesh area, in Sudan. Eur J Clin Microbiol Infect Dis 2008; 27:725-32. [PMID: 18373107 DOI: 10.1007/s10096-008-0499-1] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/06/2007] [Accepted: 02/18/2008] [Indexed: 10/22/2022]
Abstract
Estimation of the prevalence of the molecular markers of sulfadoxine/pyrimethamine (SP) and chloroquine (CQ) resistance and validation of the association of mutations with resistance in different settings is needed for local policy guidance and for contributing to a global map for anti-malarial drug resistance. In this study, malaria patients treated with SP alone (60) and SP with CQ (194) had a total treatment failure (TF) of 35.4%, with no difference between the two arms. The polymerase chain reaction-enzyme-linked immunosorbent assay (PCR-ELISA) method was used to identify polymorphisms in 15 loci in the dhfr, dhps and pfcrt genes in a subset of 168 infections. The results revealed a similar frequency of all single nucleotide polymorphisms (SNPs) in the two arms, except dhps 581G, which was over-represented in infections that failed to respond to SP alone (TF). In all infections, a high frequency of dhfr CICNI haplotype (51I and 108N) was found, but without discrimination between the adequate clinical and parasitological response (ACPR, 75.6%) and TF (82.9%). Similarly, the dhps SGEAA haplotype (437G and 540E) (ACPR, 60.5%; TF, 65.9%) and the combined CICNI/SGEAA haplotype (ACPR, 50%; TF 55%) were not associated with TF. In contrast to other studies in Africa, the triple 51I/59R/108N mutation was rare (0.6%). In addition, the pfcrt CVIET haplotype (93%) was found to be associated with the CICNI/SGEAA haplotype. Finally, these data represent a baseline for SP resistance molecular markers needed before the deployment of SP/artesunate combination therapy in the Sudan.
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Real-time PCR/MCA assay using fluorescence resonance energy transfer for the genotyping of resistance related DHPS-540 mutations in Plasmodium falciparum. Malar J 2008; 7:48. [PMID: 18346279 PMCID: PMC2276220 DOI: 10.1186/1475-2875-7-48] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/18/2007] [Accepted: 03/17/2008] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Sulphadoxine-pyrimethamine has been abandoned as first- or second-line treatment by most African malaria endemic countries in favour of artemisinin-based combination treatments, but the drug is still used as intermittent preventive treatment during pregnancy. However, resistance to sulphadoxine-pyrimethamine has been increasing in the past few years and, although the link between molecular markers and treatment failure has not been firmly established, at least for pregnant women, it is important to monitor such markers. METHODS This paper reports a novel sensitive, semi-quantitative and specific real-time PCR and melting curve analysis (MCA) assay using fluorescence resonance energy transfer (FRET) for the detection of DHPS-540, an important predictor for SP resistance. FRET/MCA was evaluated using 78 clinical samples from malaria patients and compared to PCR-RFLP. RESULTS Sixty-two samples were in perfect agreement between both assays. One sample showed a small wild type signal with FRET/MCA that indicates a polyclonal infection. Four samples were not able to generate enough material in both assays to distinguish mutant from wild-type infection, six samples gave no signal in PCR-RFLP and five samples gave no amplification in FRET/MCA. CONCLUSION FRET/MCA is an effective tool for the identification of SNPs in drug studies and epidemiological surveys on resistance markers in general and DHPS-540 mutation in particular.
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Raman J, Sharp B, Kleinschmidt I, Roper C, Streat E, Kelly V, Barnes KI. Differential effect of regional drug pressure on dihydrofolate reductase and dihydropteroate synthetase mutations in southern Mozambique. Am J Trop Med Hyg 2008; 78:256-261. [PMID: 18256426 PMCID: PMC3748784] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 05/25/2023] Open
Abstract
The prevalence and frequency of the dihydrofolate reductase (dhfr) and dihydropteroate synthetase (dhps) mutations associated with sulfadoxine-pyrimethamine (SP) resistance at 13 sentinel surveillance sites in southern Mozambique were examined regularly between 1999 and 2004. Frequency of the dhfr triple mutation increased from 0.26 in 1999 to 0.96 in 2003, remaining high in 2004. The dhps double mutation frequency peaked in 2001 (0.22) but declined to baseline levels (0.07) by 2004. Similarly, parasites with both dhfr triple and dhps double mutations had increased in 2001 (0.18) but decreased by 2004 (0.05). The peaking of SP resistance markers in 2001 coincided with a SP-resistant malaria epidemic in neighboring KwaZulu-Natal, South Africa. The decline in dhps (but not dhfr) mutations corresponded with replacement of SP with artemether-lumefantrine as malaria treatment policy in KwaZulu-Natal. Our results show that drug pressure can exert its influence at a regional level rather than merely at a national level.
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Affiliation(s)
- Jaishree Raman
- Address correspondence to Malaria Lead Programme, Medical Research Council, 491 Ridge Road, Overport, Durban, KZN, 4067 South Africa.
| | | | - Immo Kleinschmidt
- London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, England, Telephone: +44 207 927 2103, Fax: +44 207 636 8739,
| | - Cally Roper
- Department of Infectious and Tropical Diseases, London School of Hygiene and Tropical Medicine, Keppel Street, London, WC1E 7HT, England, Telephone: +44 207 927 2331, Fax: +44 207 636 8739;
| | - Elizabeth Streat
- Maputo Province Directorate of Health, Av. Gov. Raimundo Bila 438, Matola City, Maputo Province, Mozambique, Telephone: +258 2172 2929, Fax: +258 2172 2929,
| | - Val Kelly
- Malaria Lead Programme, Medical Research Council, 491 Ridge Road, Durban, 4067, KwaZulu-Natal, South Africa, Telephone: +27 31 203 4782, Fax: +27 31 203 4704,
| | - Karen I. Barnes
- Division of Clinical Pharmacology, Department of Medicine, University of Cape Town, Groote Schuur Hospital, Old Main Road, Cape Town, 7707, Western Cape, South Africa, Telephone: +27 21 406 6294, Fax: +27 21 406 6759,
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Fatumo S, Plaimas K, Mallm JP, Schramm G, Adebiyi E, Oswald M, Eils R, König R. Estimating novel potential drug targets of Plasmodium falciparum by analysing the metabolic network of knock-out strains in silico. INFECTION GENETICS AND EVOLUTION 2008; 9:351-8. [PMID: 18313365 DOI: 10.1016/j.meegid.2008.01.007] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/12/2007] [Revised: 12/21/2007] [Accepted: 01/17/2008] [Indexed: 10/22/2022]
Abstract
Malaria is one of the world's most common and serious diseases causing death of about 3 million people each year. Its most severe occurrence is caused by the protozoan Plasmodium falciparum. Biomedical research could enable treating the disease by effectively and specifically targeting essential enzymes of this parasite. However, the parasite has developed resistance to existing drugs making it indispensable to discover new drugs. We have established a simple computational tool which analyses the topology of the metabolic network of P. falciparum to identify essential enzymes as possible drug targets. We investigated the essentiality of a reaction in the metabolic network by deleting (knocking-out) such a reaction in silico. The algorithm selected neighbouring compounds of the investigated reaction that had to be produced by alternative biochemical pathways. Using breadth first searches, we tested qualitatively if these products could be generated by reactions that serve as potential deviations of the metabolic flux. With this we identified 70 essential reactions. Our results were compared with a comprehensive list of 38 targets of approved malaria drugs. When combining our approach with an in silico analysis performed recently [Yeh, I., Hanekamp, T., Tsoka, S., Karp, P.D., Altman, R.B., 2004. Computational analysis of Plasmodium falciparum metabolism: organizing genomic information to facilitate drug discovery. Genome Res. 14, 917-924] we could improve the precision of the prediction results. Finally we present a refined list of 22 new potential candidate targets for P. falciparum, half of which have reasonable evidence to be valid targets against micro-organisms and cancer.
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Affiliation(s)
- Segun Fatumo
- Computer and Information Sciences Department, Covenant University, Ota, Nigeria
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Ndounga M, Tahar R, Basco LK, Casimiro PN, Malonga DA, Ntoumi F. Therapeutic efficacy of sulfadoxine-pyrimethamine and the prevalence of molecular markers of resistance in under 5-year olds in Brazzaville, Congo. Trop Med Int Health 2007; 12:1164-71. [PMID: 17956498 DOI: 10.1111/j.1365-3156.2007.01904.x] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
OBJECTIVE To test the efficacy of sulfadoxine-pyremethamine (SP) monotherapy and establish the prevalence of mutations in dhfr and dhps in Brazzaville, Congo. METHOD We recruited 97 patients aged 6-59 months with uncomplicated malaria who attended Tenrikyo public health centre. Eighty-three were followed until day 28. SP efficacy was determined by the WHO 28-day test and analysis of mutations in the Plasmodium falciparum dihydrofolate reductase (pfdhfr) and dihydropteroate synthase (pfdhps) genes. RESULTS There were seven (8.4%) early treatment failures, 23 late treatment failures (27.7%), nine (10.8%) late parasitological failures and 44 (53%) adequate clinical and parasitological responses (ACPR). After polymerase chain reaction (PCR) analysis of 64 available samples, the corrected results there were 44 (68.8%) ACPR and 19 recrudescent cases (31.2%). Approximately, 97.5% of samples bore the Asn51Ile mutation, 66.2% the Cys59Arg mutation and 98.8% the Ser108Asn mutation. Mutations of dhps at positions 437 (Ala-Gly) and 436 (Ser-Ala) were found in 85% and 12.5% of samples. Quadruple mutations (pfdhfr triple mutations in codons 51, 59 and 108+ pfdhps mutation in 437) were found in 42 samples (52.5%) and associated with treatment failures. CONCLUSION This high level of treatment failures and mutations in both genes calls for the urgent application of the new policy for malaria treatment to delay the spread of SP resistance.
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Affiliation(s)
- Mathieu Ndounga
- Laboratoire de Pharmacologie, Centre d'Etudes sur les Ressources Végétales, Brazzaville, Congo.
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Dittrich S, Mitchell SL, Blagborough AM, Wang Q, Wang P, Sims PFG, Hyde JE. An atypical orthologue of 6-pyruvoyltetrahydropterin synthase can provide the missing link in the folate biosynthesis pathway of malaria parasites. Mol Microbiol 2007; 67:609-18. [PMID: 18093090 PMCID: PMC2229834 DOI: 10.1111/j.1365-2958.2007.06073.x] [Citation(s) in RCA: 34] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
Folate metabolism in malaria parasites is a long-standing, clinical target for chemotherapy and prophylaxis. However, despite determination of the complete genome sequence of the lethal species Plasmodium falciparum, the pathway of de novo folate biosynthesis remains incomplete, as no candidate gene for dihydroneopterin aldolase (DHNA) could be identified. This enzyme catalyses the third step in the well-characterized pathway of plants, bacteria, and those eukaryotic microorganisms capable of synthesizing their own folate. Utilizing bioinformatics searches based on both primary and higher protein structures, together with biochemical assays, we demonstrate that P. falciparum cell extracts lack detectable DHNA activity, but that the parasite possesses an unusual orthologue of 6-pyruvoyltetrahydropterin synthase (PTPS), which simultaneously gives rise to two products in comparable amounts, the predominant of which is 6-hydroxymethyl-7,8-dihydropterin, the substrate for the fourth step in folate biosynthesis (catalysed by 6-hydroxymethyl-7,8-dihydropterin pyrophosphokinase; PPPK). This can provide a bypass for the missing DHNA activity and thus a means of completing the biosynthetic pathway from GTP to dihydrofolate. Supported by site-directed mutagenesis experiments, we ascribe the novel catalytic activity of the malarial PTPS to a Cys to Glu change at its active site relative to all previously characterized PTPS molecules, including that of the human host.
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Affiliation(s)
- Sabine Dittrich
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7DN, UK
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177
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A network to monitor antimalarial drug resistance: a plan for moving forward. Trends Parasitol 2007; 24:43-8. [PMID: 18042432 DOI: 10.1016/j.pt.2007.09.008] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2007] [Revised: 09/25/2007] [Accepted: 09/25/2007] [Indexed: 01/27/2023]
Abstract
The spread of resistance to antimalarial drugs has required changes in the recommended first-line treatment for falciparum malaria in almost all regions. Most drugs recommended currently are combinations of a long-acting antimalarial and an artemisinin derivative. This article presents the rationale for establishing a web-based, open-access database of antimalarial drug resistance and efficacy: the World Antimalarial Resistance Network (WARN). The goal of this network is to assemble the tools and information that will enable the malaria community to collate, analyze and share contemporary information on antimalarial-drug efficacy in all endemic regions so that decisions on antimalarial-drug use are based on solid evidence.
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Zakeri S, Afsharpad M, Raeisi A, Djadid ND. Prevalence of mutations associated with antimalarial drugs in Plasmodium falciparum isolates prior to the introduction of sulphadoxine-pyrimethamine as first-line treatment in Iran. Malar J 2007; 6:148. [PMID: 17999755 PMCID: PMC2214731 DOI: 10.1186/1475-2875-6-148] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/26/2007] [Accepted: 11/13/2007] [Indexed: 11/26/2022] Open
Abstract
Background This work was carried out to assess the patterns and prevalence of resistance to chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) in Iran. Methods The prevalence of pfcrt K76T, pfmdr1 N86Y, pfdhfr N51I, C59R, S108N/T and I164L and codons S436F/A, A437G, K540E, A581E, and A613S/T in pfdhps genes were genotyped by PCR/RFLP methods in 206 Plasmodium falciparum isolates from Chabahar and Sarbaz districts in Sistan and Baluchistan province, Iran, during 2003–2005. Results All P. falciparum isolates carried the 108N, while 98.5% parasite isolates carried the 59R mutation. 98.5% of patients carried both 108N and 59R. The prevalence of pfdhps 437G mutation was 17% (Chabahar) and 33% (Sarbaz) isolates. 20.4% of samples presented the pfdhfr 108N, 59R with pfdhps 437G mutations. The frequency of allele pfcrt 76T was 98%, while 41.4% (Chabahar) and 27.7% (Sarbaz) isolates carried pfmdr1 86Y allele. Eight distinct haplotypes were identified in all 206 samples, while the most prevalent haplotype was T76/N86/N51R59N108/A437 among both study areas. Conclusion Finding the fixed level of CQ resistance polymorphisms (pfcrt 76T) suggests that CQ must be withdrawn from the current treatment strategy in Iran, while SP may remain the treatment of choice for uncomplicated malaria.
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Affiliation(s)
- Sedigheh Zakeri
- Malaria and Vector Research Group (MVRG), Biotechnology Research Center, Institut Pasteur of Iran, Pasteur Avenue, PO BOX 1316943551, Tehran, Iran.
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Kidgell C, Winzeler EA. Using the genome to dissect the molecular basis of drug resistance. Future Microbiol 2007; 1:185-99. [PMID: 17661664 DOI: 10.2217/17460913.1.2.185] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
The need to understand the genetic basis of drug resistance in human pathogens has never been greater. The global incidence of drug-resistant organisms, such as those that cause malaria, continues to rise, while the repertoire of effective, inexpensive drugs is declining. Genomic technologies, such as DNA microarrays and full-genome sequencing offer new hope in advancing our understanding of the underlying genetic processes that facilitate a resistance phenotype. Importantly, evidence that drug resistance in many organisms can be a multigene, complex phenomenon implies that unbiased, genome-wide scans of diversity will be required to fully understand the molecular mechanisms of both established and novel resistance traits. While the potential application of full-genome approaches for deciphering mechanisms of drug resistance has yet to be fully realized, this review evaluates drug resistance in human malaria parasites and discusses the exciting role genome-based systems could play in monitoring drug resistance, as well as guiding the implementation of efficient therapeutic strategies for malaria. The approaches reviewed within this article will be applicable to all known or emerging microbial pathogens.
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Affiliation(s)
- Claire Kidgell
- The Scripps Research Institute, ICND 202, La Jolla, CA 92037, USA.
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The implication of dihydrofolate reductase and dihydropteroate synthetase gene mutations in modification of Plasmodium falciparum characteristics. Malar J 2007; 6:108. [PMID: 17686173 PMCID: PMC1971711 DOI: 10.1186/1475-2875-6-108] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2007] [Accepted: 08/08/2007] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The Plasmodium falciparum dihydrofolate reductase (DHFR) and dihydropteroate synthetase (DHPS) are enzymes of central importance in parasite metabolism. The dhfr and dhps gene mutations are known to be associated with sulphadoxine/pyrimethamine (SP) resistance. OBJECTIVE To investigate the effects of dhfr/dhps mutations on parasite characteristics other than SP resistance. METHOD Parasite infections obtained from 153 Sudanese patients with uncomplicated falciparum malaria treated with SP or SP + chloroquine, were successfully genotyped at nine codons in the dhfr/dhps genes by PCR-ELISA. RESULTS & CONCLUSION Mutations were detected in dhfr at N51I, S108N and C59R, and in at dhps at A/S436F, A437G, K540E and A581G, the maximum number of mutations per infection were five. Based on number of mutant codons per infection (multiplicity of mutation, MOM), the infections were organized into six grades: wild-types (grade 0; frequency, 0.03) and infections with MOM grades of 1 to 5, with the following cumulative frequency; 0.97, 0.931, 0.866, 0.719, 0.121, respectively. There was no significant association between the MOM and SP response. Importantly, immunity, using age as a surrogate marker, contributed significantly to the clearance of parasites with multiple dhfr/dhps mutations. However, these mutations have a survival advantage as they were associated with increased gametocytogenesis. The above implications of dhfr/dhps mutations were associated with MOM 2 to 5, regardless of the gene/codon locus.
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181
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Tahar R, Basco LK. Molecular epidemiology of malaria in Cameroon. XXVII. Clinical and parasitological response to sulfadoxine-pyrimethamine treatment and Plasmodium falciparum dihydrofolate reductase and dihydropteroate synthase alleles in Cameroonian children. Acta Trop 2007; 103:81-9. [PMID: 17640607 DOI: 10.1016/j.actatropica.2007.04.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/04/2006] [Revised: 03/09/2007] [Accepted: 04/17/2007] [Indexed: 10/23/2022]
Abstract
The rapidly changing epidemiology of antifolate-resistant Plasmodium falciparum in Africa requires monitoring. The present study was designed to assess the degree of association between the clinical and parasitological response to sulfadoxine-pyrimethamine and allelic combinations of dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes. Of 357 children who completed the 14-day follow-up, an adequate clinical and parasitological response was observed in 316 patients (88.5%) and early and late failures occurred in 18 (5%) and 23 (6.4%, mostly due to recrudescence) patients, respectively. The majority of clinical isolates were characterized as "quadruple" (n=196, 55.2%; N51I-C59R-S108N in DHFR and A437G in DHPS) or "triple" mutants (n=97, 27.3%; N51I-C59R-S108N in DHFR and wild-type DHPS; S108N+N51I or C59R in DHFR and A437G in DHPS). Wild-type, single mutation, and double mutation were observed in 29, 20, and 13 parasites, respectively. The comparison of different sets of mutations and early or late failures did not reveal any molecular marker associated with treatment outcome when the follow-up period was limited to 14 days (P>0.05). In this study, the determination of dhfr-dhps genotypes was of limited value to predict the treatment outcome in individual patients, mostly due to few treatment failures and few wild-type haplotypes. Further monitoring will be required to define the relationship between clinical response to SP therapy and parasite genotypes in our epidemiological setting.
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Affiliation(s)
- Rachida Tahar
- Unité de Recherche 77 Paludologie Afro-tropicale, Institut de Recherche pour le Développement, Laboratoire de Recherche sur le Paludisme, Organisation de Coordination pour la lutte contre les Endémies en Afrique Centrale, B. P. 288, Yaoundé, Cameroon
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182
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Prajapati SK, Joshi H, Valecha N, Reetha AM, Eapen A, Kumar A, Das MK, Yadav RS, Rizvi MA, Dash AP. Allelic polymorphism in the Plasmodium vivax dihydrofolate reductase gene among Indian field isolates. Clin Microbiol Infect 2007; 13:331-4. [PMID: 17391393 DOI: 10.1111/j.1469-0691.2006.01639.x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
In total, 129 Plasmodium vivax isolates from different geographical areas in India were analysed for point mutations in the P. vivax dihydrofolate reductase gene that were associated with pyrimethamine resistance. A gradual increase in the frequency of mutant genotypes was observed from north to south (p <0.0001). In the northern region (Delhi, Panna and Nadiad), the wild-type genotype was most prevalent, while the mutant genotype predominated in the coastal regions of southern India (Navi Mumbai, Goa and Chennai). Isolates from the Car-Nicobar islands showed only mutant genotypes. The differential geographical pattern of mutations may be associated with the transmission pattern.
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Affiliation(s)
- S K Prajapati
- National Institute of Malaria Research (ICMR), Delhi, India
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183
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Abstract
Synthesis de novo, acquisition by salvage and interconversion of purines and pyrimidines represent the fundamental requirements for their eventual assembly into nucleic acids as nucleotides and the deployment of their derivatives in other biochemical pathways. A small number of drugs targeted to nucleotide metabolism, by virtue of their effect on folate biosynthesis and recycling, have been successfully used against apicomplexan parasites such as Plasmodium and Toxoplasma for many years, although resistance is now a major problem in the prevention and treatment of malaria. Many targets not involving folate metabolism have also been explored at the experimental level. However, the unravelling of the genome sequences of these eukaryotic unicellular organisms, together with increasingly sophisticated molecular analyses, opens up possibilities of introducing new drugs that could interfere with these processes. This review examines the status of established drugs of this type and the potential for further exploiting the vulnerability of apicomplexan human pathogens to inhibition of this key area of metabolism.
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Affiliation(s)
- John E Hyde
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester M1 7ND, UK.
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184
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Carnevale EP, Kouri D, DaRe JT, McNamara DT, Mueller I, Zimmerman PA. A multiplex ligase detection reaction-fluorescent microsphere assay for simultaneous detection of single nucleotide polymorphisms associated with Plasmodium falciparum drug resistance. J Clin Microbiol 2006; 45:752-61. [PMID: 17121999 PMCID: PMC1829096 DOI: 10.1128/jcm.01683-06] [Citation(s) in RCA: 31] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Incomplete malaria control efforts have resulted in a worldwide increase in resistance to drugs used to treat the disease. A complex array of mutations underlying antimalarial drug resistance complicates efficient monitoring of parasite populations and limits the success of malaria control efforts in regions of endemicity. To improve the surveillance of Plasmodium falciparum drug resistance, we developed a multiplex ligase detection reaction-fluorescent-microsphere-based assay (LDR-FMA) that identifies single nucleotide polymorphisms (SNPs) in the P. falciparum dhfr (9 alleles), dhps (10 alleles), and pfcrt (3 alleles) genes associated with resistance to Fansidar and chloroquine. We evaluated 1,121 blood samples from study participants in the Wosera region of Papua New Guinea, where malaria is endemic. Results showed that 468 samples were P. falciparum negative and 453 samples were P. falciparum positive by a Plasmodium species assay and all three gene assays (concordance, 82.2%). For P. falciparum infections where the assay for each gene was positive, 2 samples carried resistance alleles for all three genes, 299 carried resistance alleles for dhfr and pfcrt, 131 carried resistance alleles for only one gene (dhfr [n = 40], dhps [n = 1], or pfcrt [n = 90]), and 21 carried only sensitive alleles at all three genes. Mixed-strain infections characterized 100 samples. Overall, 95.4% (432/453) of P. falciparum-infected samples carried at least one allele associated with resistance to Fansidar or chloroquine. In view of the fact that 86.3% (391/453) of P. falciparum-infected samples carried pfcrt mutations, chloroquine is largely ineffective against P. falciparum in Papua New Guinea. Surveillance of additional dhfr and dhps polymorphisms in order to monitor the continued effectiveness of Fansidar is recommended.
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Affiliation(s)
- Eric P Carnevale
- The Center for Global Health and Diseases, Case Western Reserve University, Wolstein Research Building, Room 4-125, 2103 Cornell Rd., Cleveland, OH 44106-7286, USA
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185
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Fernley RT, Iliades P, Macreadie I. A rapid assay for dihydropteroate synthase activity suitable for identification of inhibitors. Anal Biochem 2006; 360:227-34. [PMID: 17134675 DOI: 10.1016/j.ab.2006.10.036] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/27/2006] [Revised: 09/27/2006] [Accepted: 10/24/2006] [Indexed: 11/25/2022]
Abstract
The enzymes 6-hydroxymethylpterin pyrophosphokinase (HPPK) and dihydropteroate synthase (DHPS) catalyze sequential steps in folate biosynthesis. They are present in microorganisms but absent in mammals and therefore are especially suitable targets for antimicrobials. Sulfa drugs (sulfonamides and sulfones) currently are used as antimicrobials targeting DHPS, although resistance to these drugs is increasing. The most widely used assay that measures activity of these enzymes, to assess new inhibitors in vitro, is not amenable to automation. This article describes a simple, coupled, enzymatic spectrophotometric assay where the product of the DHPS reaction, dihydropteroate, is reduced to tetrahydropteroate by excess dihydrofolate reductase (DHFR) using the cofactor NADPH. The oxidation of NADPH is monitored at 340 nm. The activity of both HPPK and DHPS can be measured in this assay, and it has been used to measure kinetic parameters of wild-type and sulfa drug-resistant DHPS enzymes to demonstrate the utility of the assay. It is a sensitive and reproducible assay that can be readily automated and used in multiwell plates. This NADPH-coupled microplate photometric assay could be used for rapid screening of chemical libraries for novel inhibitors of folate biosynthesis as the first step in developing new antimicrobial drugs targeting the folate biosynthetic pathway.
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Affiliation(s)
- Ross T Fernley
- CSIRO, Molecular and Health Technologies, Parkville, Vic. 3052, Australia.
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186
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de Beer TAP, Louw AI, Joubert F. Elucidation of sulfadoxine resistance with structural models of the bifunctional Plasmodium falciparum dihydropterin pyrophosphokinase–dihydropteroate synthase. Bioorg Med Chem 2006; 14:4433-43. [PMID: 16517168 DOI: 10.1016/j.bmc.2006.02.035] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2006] [Revised: 02/16/2006] [Accepted: 02/17/2006] [Indexed: 11/24/2022]
Abstract
Resistance of the most virulent human malaria parasite, Plasmodium falciparum, to antifolates is spreading with increasing speed, especially in Africa. Antifolate resistance is mainly caused by point mutations in the P. falciparum dihydropteroate synthase (DHPS) and dihydrofolate reductase (DHFR) target proteins. Homology models of the bifunctional P. falciparum dihydropterin pyrophosphokinase-dihydropteroate synthase (PPPK-DHPS) enzyme as well as the separate domains complete with bound substrates were constructed using the crystal structures of Saccharomyces cerevisiae (PPPK-DHPS), Mycobacterium tuberculosis (DHPS), Bacillus anthracis (DHPS), and Escherichia coli (PPPK) as templates. The resulting structures were subsequently solvated and refined using molecular dynamics. The active site residues of DHPS are highly conserved in S. cerevisiae, M. tuberculosis, E. coli, S. aureus, and B. anthracis, an attribute also shared by P. falciparum DHPS. Sulfadoxine was superimposed into the equivalent position of the p-aminobenzoic acid substrate and its binding parameters were refined using minimization and molecular dynamics. Sulfadoxine appears to interact mainly with P. falciparum DHPS mainly through hydrophobic interactions. Rational explanations are provided by the model for the sulfadoxine resistance-causing effects of four of the five known mutations in P. falciparum DHPS. A possible structure for the bifunctional PPPK-DHPS was derived from the structure from the S. cerevisiae bifunctional enzyme. The active site residues of P. falciparum PPPK are also conserved when compared to S. cerevisiae, Haemophilus influenzae, and E. coli. The informative nature of these models opens up avenues for structure-based drug design approaches toward the development of alternative and more effective inhibitors of P. falciparum PPPK-DHPS.
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Affiliation(s)
- Tjaart A P de Beer
- Bioinformatics and Computational Biology Unit, Department of Biochemistry, Faculty of Natural and Agricultural Sciences, University of Pretoria, South Africa
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187
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Coulibaly SO, Nezien D, Traoré S, Koné B, Magnussen P. Therapeutic efficacy of sulphadoxine-pyrimethamine and chloroquine for the treatment of uncomplicated malaria in pregnancy in Burkina Faso. Malar J 2006; 5:49. [PMID: 16776817 PMCID: PMC1533839 DOI: 10.1186/1475-2875-5-49] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/30/2006] [Accepted: 06/15/2006] [Indexed: 11/23/2022] Open
Abstract
BACKGROUND A reduction in the therapeutic efficacy of chloroquine (CQ) and sulphadoxine-pyrimethamine (SP) has recently been observed in Burkina Faso. As these two drugs are used in pregnancy, their efficacy in pregnant women was studied to directly assess the level of drug resistance in this specific population, rather than to extrapolate results of studies conducted in children < 5 years of age. METHODS During the malaria transmission season of 2003 in Ouagadougou, the clinical efficacy of SP and CQ, using the WHO 28-day protocol, was assessed in primigravidae and secundigravidae presenting with uncomplicated malaria. RESULTS PCR-corrected results by day 28 showed that among 62 women treated with SP, eight (12.9%) experienced late parasitological failure, but no clinical failures. Among 60 women treated with CQ, the overall failure rate was 46.7% including 1.7% early treatment failures, 5% late clinical failures and 40% late parasitological failures. SP induced a haemoglobin gain of 0.3 g/dL by day 14 and 0.9 g/dL by day 28. Treatment responses were independent of gravidity, gestational age and prior antenatal care visits. CONCLUSION While CQ should no longer be used, the efficacy of SP is still compatible with use for intermittent preventive treatment (IPT) in pregnancy. However, given the possible spread of resistance, the drug should be restricted in its use.
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Affiliation(s)
- Sheick Oumar Coulibaly
- Laboratoire National de Santé Publique, 09 BP 24 Ouagadougou 09, Burkina Faso
- UFR Sciences de la Santé, Université de Ouagadougou, 03 B.P. 7021 Ouagadougou 03, Burkina Faso
| | - Désiré Nezien
- Laboratoire National de Santé Publique, 09 BP 24 Ouagadougou 09, Burkina Faso
| | - Salifou Traoré
- Centre Medical Paul VI, 01 BP 2099 Ouagadougou 01, Burkina Faso
| | - Bibiane Koné
- UFR Sciences de la Santé, Université de Ouagadougou, 03 B.P. 7021 Ouagadougou 03, Burkina Faso
| | - Pascal Magnussen
- DBL – Institute for Health Research and Development, Copenhagen, Jaegersborg Allé 1 D DK-2920 Charlottenlund, Denmark
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188
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Platteeuw JJ. Resistance to sulphadrug-based antifolate therapy in malaria: are we looking in the right place? Trop Med Int Health 2006; 11:804-8. [PMID: 16772001 DOI: 10.1111/j.1365-3156.2006.01646.x] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Sulphadrug treatment failure in malaria therapy cannot solely be ascribed to the build-up of genetic resistance within the parasitic genome. Although numerous in vitro studies have tried to determine the exact genetic markers that could predict treatment outcome in patients, this research has not been conclusive. Sulphadrugs work by competitive inhibition with pABA at one point of the pathway to de novo folate synthesis. However, evidence suggests that the malaria parasite is capable of overcoming this competitive inhibition by switching over to other metabolic pathways, like direct folate salvage from a person's bloodstream. In other words, increased folic acid administration, via diet or supplementation, may have reduced the effectiveness of sulphadrugs more than genetic mutations. Although in vitro studies are valuable for understanding disease mechanisms, we should not forget that the human being is infinitely more complex than any laboratory model.
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189
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Yuthavong Y, Kamchonwongpaisan S, Leartsakulpanich U, Chitnumsub P. Folate metabolism as a source of molecular targets for antimalarials. Future Microbiol 2006; 1:113-25. [PMID: 17661690 DOI: 10.2217/17460913.1.1.113] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
Folate metabolism of the malaria parasites provides two targets for current antimalarials: dihydrofolate reductase and dihydropteroate synthase. Dihydrofolate reductase inhibitors have been used as antimalarials over the past few decades, often in combination with dihydropteroate synthase inhibitors. Resistance to these antifolate drugs developed through mutations in both target enzymes. However, limited mutation possibilities gave opportunities for the development of new drugs. Furthermore, other enzymes in the folate and related pathways are potential new targets that remain to be exploited. These include thymidylate synthase, an enzyme fused with dihydrofolate reductase in the same protein chain, serine hydroxymethyltransferase, methylene tetrahydrofolate dehydrogenase, methionine synthase and enzymes in the glycine cleavage pathway.
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190
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Menegon M, Majori G, Severini C. Genetic variations of the Plasmodium vivax dihydropteroate synthase gene. Acta Trop 2006; 98:196-9. [PMID: 16647679 DOI: 10.1016/j.actatropica.2006.03.003] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2005] [Revised: 03/17/2006] [Accepted: 03/30/2006] [Indexed: 10/24/2022]
Abstract
Dihydropteroate synthase gene of Plasmodium vivax was recently identified. In the present study, the sequences of the dyhydropteroate synthase gene of 68 P. vivax isolates from various geographic areas were compared. Sequencing revealed limited polymorphism at codons 383 and 553 in all analyzed samples. Interstrain analysis showed several genotypic variations in the tandem repeats domain which produce length polymorphism between different parasite isolates.
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Affiliation(s)
- Michela Menegon
- Department of Infectious, Parasitic and Immunomediated Diseases, Istituto Superiore di Sanità, Rome, Italy.
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191
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Gatton ML, Cheng Q. Plasmodium falciparum infection dynamics and transmission potential following treatment with sulfadoxine-pyrimethamine. J Antimicrob Chemother 2006; 58:47-51. [PMID: 16641113 PMCID: PMC1592320 DOI: 10.1093/jac/dkl158] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
OBJECTIVES To investigate the overall efficacy of sulfadoxine-pyrimethamine (SP) treatment and the corresponding transmission potential for patients infected with SP-resistant Plasmodium falciparum. METHODS A mathematical model of the in-host dynamics of P. falciparum infections was used to simulate infections with parasites having different numbers of mutations in the dhfr and dhps genes and their responses to SP treatment. The treatment outcome and transmission potential of each simulated infection following SP treatment was assessed by tracking asexual parasite density and the number of days with sufficient mature gametocytes to give a > 95% probability of infecting a mosquito. RESULTS The results show treatment failure only occurring in patients infected with parasites having two mutations in dihydrofolate reductase (DHFR) combined with at least two mutations in dihydropteroate synthetase (DHPS) or with parasites having a triple mutation in DHFR. Highly mutated parasites (three mutations in each gene) caused the highest clinical failure rate, while moderately mutated parasites (three mutations in DHFR plus one mutation in DHPS) produced a high rate of asymptomatic parasitological failure following SP treatment. This high rate of asymptomatic recrudescence caused the transmission potential of infections with moderately resistant parasites to exceed that of highly resistant parasites. CONCLUSIONS The model output suggests that infection dynamics following SP treatment and the overall transmission potential are inherently linked. The combination of prolonged asymptomatic parasitaemia and increased transmission potential allows parasites having three mutations in DHFR, but fewer mutations in DHPS, to expand largely unnoticed.
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Affiliation(s)
- Michelle L Gatton
- Australian Centre for International and Tropical Health and Nutrition, University of Queensland Brisbane, Australia.
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192
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Imwong M, Pukrittayakamee S, Cheng Q, Moore C, Looareesuwan S, Snounou G, White NJ, Day NPJ. Limited polymorphism in the dihydropteroate synthetase gene (dhps) of Plasmodium vivax isolates from Thailand. Antimicrob Agents Chemother 2006; 49:4393-5. [PMID: 16189131 PMCID: PMC1251524 DOI: 10.1128/aac.49.10.4393-4395.2005] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The dhps sequences of 55 Plasmodium vivax isolates (39 from Thailand and 16 from elsewhere) revealed mutant Pvdhps at codons 383 and/or 553 (A --> G) in 33 isolates, all from Thailand. Mutations of Pvdhps and Pvdhfr were correlated. Multiple mutations were associated with high-grade sulfadoxine-pyrimethamine resistance.
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Affiliation(s)
- Mallika Imwong
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
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193
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Thera MA, Sehdev PS, Coulibaly D, Traore K, Garba MN, Cissoko Y, Kone A, Guindo A, Dicko A, Beavogui AH, Djimde AA, Lyke KE, Diallo DA, Doumbo OK, Plowe CV. Impact of trimethoprim-sulfamethoxazole prophylaxis on falciparum malaria infection and disease. J Infect Dis 2005; 192:1823-9. [PMID: 16235184 PMCID: PMC2740817 DOI: 10.1086/498249] [Citation(s) in RCA: 94] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2005] [Accepted: 09/19/2005] [Indexed: 11/04/2022] Open
Abstract
BACKGROUND Trimethoprim-sulfamethoxazole (TS) prophylaxis is recommended for persons living with human immunodeficiency virus infection and acquired immunodeficiency syndrome in Africa. TS and the antimalarial combination sulfadoxine-pyrimethamine (SP) share mechanisms of action and resistance patterns, and concerns about the impact of TS resistance on SP efficacy have contributed to reluctance to implement TS prophylaxis in Africa. METHODS To determine whether TS prophylaxis impairs SP efficacy for treatment of uncomplicated falciparum malaria, we conducted a randomized, controlled, open-label study of TS prophylaxis. Two hundred and forty children 5-15 years old were randomized in a 2 : 1 fashion to receive either thrice-weekly TS for 12 weeks or no prophylaxis and were treated with SP for subsequent episodes of malaria. The incidence of malaria, SP efficacy, and the prevalence of parasite mutations that confer antifolate drug resistance were measured. RESULTS TS prophylaxis had a 99.5% protective efficacy against episodes of clinical malaria, with 97% efficacy against infection. Four SP treatment failures occurred in the control group, and none occurred in the TS group. No evidence was seen for selection by TS of antifolate resistance-conferring mutations in parasite dihydrofolate reductase or dihydropteroate synthase during subclinical infections. CONCLUSIONS In this setting of low antifolate resistance, TS was highly effective in preventing falciparum malaria infection and disease and did not appear to select for SP-resistant parasites.
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Affiliation(s)
- Mahamadou A Thera
- Bandiagara Malaria Project, Malaria Research and Training Center, University of Bamako, Mali
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194
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Berglez J, Pilling P, Macreadie I, Fernley RT. Purification, properties, and crystallization of Saccharomyces cerevisiae dihydropterin pyrophosphokinase-dihydropteroate synthase. Protein Expr Purif 2005; 41:355-62. [PMID: 15866722 DOI: 10.1016/j.pep.2005.02.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/13/2004] [Revised: 02/02/2005] [Indexed: 11/29/2022]
Abstract
The tri-functional enzyme of Saccharomyces cerevisiae dihydroneopterin aldolase (DHNA)-dihydropterin pyrophosphokinase (PPPK)-dihydropteroate synthase (DHPS) catalyzes three sequential steps in folate biosynthesis. A cDNA encoding the PPPK and DHPS domains of the tri-functional enzyme has been cloned. This bi-functional enzyme was expressed as a His(6) fusion protein in Escherichia coli and the protein was purified to apparent homogeneity. The purified protein possesses both PPPK and DHPS activities as measured by the incorporation of [(3)H]p-ABA into the appropriate substrate. The pH optimum of the DHPS activity was determined to be 8.5. Gel filtration measurement indicates that the protein exists as a dimer in solution. A robotic screening method was used to identify crystallization conditions. Bi-pyramidal crystals of the enzyme formed with the protein in the presence of a pterin substrate analog in phosphate buffer (pH 6.3) and these diffracted to 2.3A. Structural information from these crystals could be used to design novel drugs to inhibit folate biosynthesis.
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195
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Arav-Boger R, Shapiro TA. MOLECULAR MECHANISMS OF RESISTANCE IN ANTIMALARIAL CHEMOTHERAPY: The Unmet Challenge. Annu Rev Pharmacol Toxicol 2005; 45:565-85. [PMID: 15822189 DOI: 10.1146/annurev.pharmtox.45.120403.095946] [Citation(s) in RCA: 39] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
▪ Abstract The enormous public health problem posed by malaria has been substantially worsened in recent years by the emergence and worldwide spread of drug-resistant parasites. The utility of two major therapies, chloroquine and the synergistic combination of pyrimethamine/sulfadoxine, is now seriously compromised. Although several genetic mechanisms have been described, the major source of drug resistance appears to be point mutations in protein target genes. Clinically significant resistance to these agents requires the accumulation of multiple mutations, which genetic studies of parasite populations suggest arise focally and sweep through the population. Efforts to circumvent resistance range from the use of combination therapy with existing agents to laboratory studies directed toward discovering novel targets and therapies. The prevention and management of drug resistance are among the most important practical problems of tropical medicine and public health. Leonard J. Bruce-Chwatt, 1972
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Affiliation(s)
- Ravit Arav-Boger
- Division of Infectious Diseases, Department of Pediatrics, The Johns Hopkins University School of Medicine, Baltimore, Maryland 21205, USA.
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196
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Khim N, Bouchier C, Ekala MT, Incardona S, Lim P, Legrand E, Jambou R, Doung S, Puijalon OM, Fandeur T. Countrywide survey shows very high prevalence of Plasmodium falciparum multilocus resistance genotypes in Cambodia. Antimicrob Agents Chemother 2005; 49:3147-52. [PMID: 16048916 PMCID: PMC1196218 DOI: 10.1128/aac.49.8.3147-3152.2005] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Cambodia is located in an area of resistance to multiple antimalarials and has been the first country to implement the systematic use of an artesunate-mefloquine combination as first-line treatment for Plasmodium falciparum malaria. Little is known, however, about the prevalence of resistance mutations within the natural parasite populations, impeding rational drug policy in this context. Using direct sequencing of PCR products, we have analyzed sequence polymorphism of the dihydrofolate reductase-thymidylate synthase, dihydropteroate synthetase, and multidrug resistance 1 genes in a large number of clinical P. falciparum isolates collected in various areas of Cambodia. This highlighted a 100% prevalence of haplotypes with multiple mutations in the target genes of antifolates after more than a decade without use of antifolates for malaria therapy. A high prevalence of mutations in Pfmdr1, including mutations associated with decreased in vitro susceptibility to mefloquine and quinine, was also observed. In addition, novel, low-frequency mutations were detected in Pfmdr1. Our findings show an alarming rate of multilocus resistance genotypes in Cambodia, requiring diligent surveillance and imposing limitations on possible future drug combinations.
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Affiliation(s)
- Nimol Khim
- Faculté de Pharmacie, UFR sciences pharmaceutiques, UMR INRA-Université d'Immunologie Parasitaire et de Vaccinologie, 31, avenue Monge Parc Grandmont, 37200 Tours, France.
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197
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Happi CT, Gbotosho GO, Folarin OA, Akinboye DO, Yusuf BO, Ebong OO, Sowunmi A, Kyle DE, Milhous W, Wirth DF, Oduola AMJ. Polymorphisms in Plasmodium falciparum dhfr and dhps genes and age related in vivo sulfadoxine-pyrimethamine resistance in malaria-infected patients from Nigeria. Acta Trop 2005; 95:183-93. [PMID: 16023986 DOI: 10.1016/j.actatropica.2005.06.015] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2005] [Revised: 06/04/2005] [Accepted: 06/06/2005] [Indexed: 11/26/2022]
Abstract
Mutations in Plasmodium falciparum dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes have been used as means to predict treatment failure to sulfadoxine-pyrimethamine (SP) and for monitoring/surveillance of resistance to the drug in many areas where malaria is endemic. However, patients responses to treatment are significantly dependent on factors like host immunity profile of treated patients. In order to investigate the relationship between molecular markers of SP resistance, host immunity and clinical outcome, the association between pre-treatment dhfr and dhps genotypes, age and treatment outcomes was evaluated in 109 children treated with SP for acute uncomplicated malaria in Ibadan, Nigeria. Seventy-three percent of the children were cured with the drug, while 27% failed treatment after 28 days of follow-up. All children infected with parasites harboring less than two dhfr/dhps mutations were cured with SP. The dhfr triple (Asn-108/Ile-51/Arg-59) mutants or the dhps double mutants (Gly-437/Glu-540) were independently associated with SP treatment failure in children aged less than 5 years, but not in older children. The dhfr and dhps quintuple mutant (dhfr triple mutant+dhps double mutant) was the genotype most strongly associated with SP treatment failure (OR=24.72, 95%CI=8.24-74.15) in both younger and older children.
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Affiliation(s)
- C T Happi
- Malaria Research Laboratories, Postgraduate Institute for Medical Research and Training (PIMRAT), College of Medicine, University of Ibadan, Ibadan, Nigeria.
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198
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Wilson PE, Alker AP, Meshnick SR. Real-time PCR methods for monitoring antimalarial drug resistance. Trends Parasitol 2005; 21:278-83. [PMID: 15922249 DOI: 10.1016/j.pt.2005.04.007] [Citation(s) in RCA: 43] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/22/2004] [Revised: 02/24/2005] [Accepted: 04/12/2005] [Indexed: 11/25/2022]
Abstract
Drug-resistant Plasmodium falciparum is a challenge to malaria control programs. Policy makers currently depend on in vivo (and, sometimes, in vitro) resistance testing to set treatment guidelines. Molecular markers such as mutations in dhfr, dhps, pfcrt and pfmdr1 represent potential surveillance tools. In this article, we describe newer high-throughput methods for detecting these molecular markers. One method, 5' nuclease real-time polymerase chain reaction, is discussed in detail.
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Affiliation(s)
- Paul E Wilson
- University of North Carolina School of Medicine, Department of Microbiology and Immunology, CB 7290, Chapel Hill, NC 27599, USA
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199
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Pink R, Hudson A, Mouriès MA, Bendig M. Opportunities and Challenges in Antiparasitic Drug Discovery. Nat Rev Drug Discov 2005; 4:727-40. [PMID: 16138106 DOI: 10.1038/nrd1824] [Citation(s) in RCA: 338] [Impact Index Per Article: 17.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
New antiparasitic drugs are urgently needed to treat and control diseases such as malaria, leishmaniasis, sleeping sickness and filariasis, which affect millions of people each year. However, because the majority of those infected live in countries in which the prospects of any financial return on investment are too low to support market-driven drug discovery and development, alternative approaches are needed. In this article, challenges and opportunities for antiparasitic drug discovery are considered, highlighting some of the progress that has been made in recent years, partly through scientific advances, but also by more effective partnership between the public and private sectors.
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Affiliation(s)
- Richard Pink
- TDR (the UNICEF/UNDP/World Bank/WHO/Special Programme for Research and Training in Tropical Diseases), Geneva 1211, Switzerland
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200
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Elandalloussi LM, Rodrigues PM, Afonso R, Leite RB, Nunes PA, Cancela ML. Shikimate and folate pathways in the protozoan parasite, Perkinsus olseni. Mol Biochem Parasitol 2005; 142:106-9. [PMID: 15907564 DOI: 10.1016/j.molbiopara.2005.03.014] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2004] [Revised: 03/15/2005] [Accepted: 03/15/2005] [Indexed: 10/25/2022]
Abstract
We have exploited the experimental accessibility of the protozoan parasite Perkinsus olseni and its similarities to apicomplexan parasites to investigate the influence of specific drugs on its proliferation. For this purpose, shikimate and folate pathways present an attractive target for parasitic therapy given their major differences with mammalian pathways. Glyphosate, a potent inhibitor of the shikimate pathway enzyme EPSP synthase inhibited the in vitro proliferation of P. olseni in a dose-dependent manner and this effect was reversed by addition of chorismate, indicating the presence of a shikimate pathway. However, this effect was not antagonised by p-aminobenzoate or folic acid. Furthermore, antagonism was observed, via pyrimethamine to glyphosate inhibitory effect, suggesting that the shikimate pathway is not essential for the biosynthesis of folate precursors and is therefore crucial for another pathway downstream from chorismate. In addition, sulfadiazine, a well known inhibitor of dihydropteorate synthase, an enzyme of the folate biosynthetic pathway,had no inhibitory effect on P. olseni proliferation. In view of these results, the parasite does not appear to require the folate biosynthesis pathway for its survival and is most likely able to use exogenous folate. Even though pyrimethamine was found to inhibit P. atlanticus growth, this inhibitory effect could not be reversed by co-addition of folic acid. Therefore, we propose that the effect of pyrimethamine observed in this study results from the inhibition of a target other than dihydrofolate reductase. Similarly, proguanil target is likely to be separate from DHFR since only its metabolite cycloguanil has been shown to have inhibitory properties on DHFR.
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