201
|
Mita T, Tanabe K. Evolution of Plasmodium falciparum drug resistance: implications for the development and containment of artemisinin resistance. Jpn J Infect Dis 2012. [DOI: 10.7883/yoken.65.465] [Citation(s) in RCA: 80] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
|
202
|
Ojurongbe O, Tijani BD, Fawole AA, Adeyeba OA, Kun JF. Prevalence of Dihydrofolate reductase gene mutations in Plasmodium falciparum isolate from pregnant women in Nigeria. Infect Dis Rep 2011; 3:e16. [PMID: 24470913 PMCID: PMC3892595 DOI: 10.4081/idr.2011.e16] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 08/12/2011] [Revised: 10/05/2011] [Accepted: 10/30/2011] [Indexed: 11/23/2022] Open
Abstract
We assessed the prevalence of Plasmodium falciparum and the frequency of the dhfr triple mutation that is associated with antifolate drug resistance among P. falciparum isolates obtained from pregnant women in Ilorin, Nigeria. The study included 179 women in the second and third trimester of pregnancy who have been exposed to intermittent preventive treatment in pregnancy (IPTp) with sulfadoxine-pyrimethamine. Thick and thin blood films and PCR were used for malaria parasite detection. Blood group and hemoglobin concentration were also determined. Mutations in P. falciparum dhfr were analyzed by sequencing DNA obtained from blood spots on filter paper. Prevalence of P. falciparum in the population (PCR corrected) was 44.1% (79/179) with 66.7% and 33.3% in the second and third trimester, respectively. Primigravide (51.3%) were more infected than multigravide (48.7%) but the difference was not statistically significant. Women in blood group A had the highest P. falciparum malaria infection (30.8%). The mean hemoglobin concentration was lower among those infected with malaria parasite. Also, more women with the malaria parasite (38.4%) had anemia compare to those without (21.4%). The prevalence of the P. falciparum dhfr mutant alleles was 64.1%, 61.5%, 38.5%, and 12.8% for I51, R59, N108 and T108, respectively. None of the samples had the L164 mutation. The combined triple dhfr mutation (51 + 59 + 108) in the population was 17.9% (7 of 39). Also, the prevalence of the triple mutant alleles was not significantly associated to the number of doses of SP taken by the women. These findings highlight the need for a regular assessment of IPTp/SP efficacy, and evaluation of possible alternative drugs.
Collapse
Affiliation(s)
- Olusola Ojurongbe
- Department of Medical Microbiology and Parasitology, Ladoke Akintola University of Technology, Nigeria; ; Institute of Tropical Medicine, University of Tuebingen, Germany
| | - Bukola D Tijani
- Department of Medical Microbiology and Parasitology, University of Ilorin Teaching Hospital
| | - Adegboyega A Fawole
- Department of Obstetrics and Gynecology, University of Ilorin Teaching Hospital, Nigeria
| | - Oluwaseyi A Adeyeba
- Department of Medical Microbiology and Parasitology, Ladoke Akintola University of Technology, Nigeria
| | - Juergen F Kun
- Institute of Tropical Medicine, University of Tuebingen, Germany
| |
Collapse
|
203
|
Reduced impact of pyrimethamine drug pressure on Plasmodium malariae dihydrofolate reductase gene. Antimicrob Agents Chemother 2011; 56:863-8. [PMID: 22123682 DOI: 10.1128/aac.05284-11] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Molecular investigations performed following the emergence of sulfadoxine-pyrimethamine (SP) resistance in Plasmodium falciparum have allowed the identification of the dihydrofolate reductase (DHFR) enzyme as the target of pyrimethamine. Although clinical cases of Plasmodium malariae are not usually treated with antifolate therapy, incorrect diagnosis and the high frequency of undetected mixed infections has probably exposed non-P. falciparum parasites to antifolate therapy in many areas. In this context, we aimed to assess the worldwide genetic diversity of the P. malariae dhfr gene in 123 samples collected in Africa and Asia, areas with different histories of SP use. Among the 10 polymorphic sites found, we have observed 7 new mutations (K55E, S58R, S59A, F168S, N194S, D207G, and T221A), which led us to describe 6 new DHFR proteins. All isolates from African countries were classified as wild type, while new mutations and haplotypes were recognized as exclusive to Madagascar (except for the double mutations at nucleotides 341 and 342 [S114N] found in one Cambodian isolate). Among these nonsynonymous mutations, two were likely related to pyrimethamine resistance: S58R (corresponding to C59R in P. falciparum and S58R in Plasmodium vivax; observed in one Malagasy sample) and S114N (corresponding to S108N in P. falciparum and S117N in P. vivax; observed in three Cambodian samples).
Collapse
|
204
|
Harrington WE, Mutabingwa TK, Kabyemela E, Fried M, Duffy PE. Intermittent treatment to prevent pregnancy malaria does not confer benefit in an area of widespread drug resistance. Clin Infect Dis 2011; 53:224-30. [PMID: 21765070 DOI: 10.1093/cid/cir376] [Citation(s) in RCA: 118] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/14/2022] Open
Abstract
BACKGROUND Millions of African women receive sulfadoxine-pyrimethamine (SP) as intermittent preventive treatment during pregnancy (IPTp) to avoid poor outcomes that result from malaria. However, parasites resistant to SP are widespread in parts of Africa, and IPTp may perversely exacerbate placental infections that contain SP-resistant parasites. METHODS The study used a cross-sectional design. We determined IPTp use in a delivery cohort of 880 pregnant women in Muheza, Tanzania, by report and by plasma sulfa measurements, and we examined its effects on maternal and fetal delivery outcomes. RESULTS In the overall cohort, IPTp was not associated with decreased odds of placental malaria or with increased mean maternal hemoglobin or mean birth weight. Unexpectedly, IPTp was associated with decreased cord hemoglobin level and increased risk of fetal anemia, which may be related to in utero SP exposure. CONCLUSIONS IPTp does not improve overall pregnancy outcomes in Muheza, Tanzania, where SP-resistant parasites predominate and may increase the odds of fetal anemia. As parasite resistance increases in a community, the overall effect of IPTp may transition from net benefit to neutral or net harm.
Collapse
Affiliation(s)
- Whitney E Harrington
- Malaria Program, Seattle Biomedical Research Institute, Seattle, Washington, USA
| | | | | | | | | |
Collapse
|
205
|
Afsharpad M, Zakeri S, Pirahmadi S, Djadid ND. Molecular assessment of dhfr/dhps mutations among Plasmodium vivax clinical isolates after introduction of sulfadoxine/pyrimethamine in combination with artesunate in Iran. INFECTION GENETICS AND EVOLUTION 2011; 12:38-44. [PMID: 22020253 DOI: 10.1016/j.meegid.2011.10.003] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/15/2011] [Revised: 09/17/2011] [Accepted: 10/06/2011] [Indexed: 01/15/2023]
Abstract
The increasing use of sulfadoxine/pyrimethamine (SP) for treatment of chloroquine-resistant Plasmodium falciparum has resulted in increased exposure of Plasmodium vivax parasites in areas where both species co-exist. In this study, the extent of mutations/haplotypes in pvdhfr and pvdhps was examined using PCR-RFLP methods in 427 P. vivax isolates in Iran after 4 years of introducing SP as the first-line anti-malarial drug in Iran. Mutations were detected in three codons of pvdhfr (F57L, S58R and S117N) and in one of pvdhps (A383G) and the majority of isolates had double mutations (58R/117N, 45.4%). In addition, the frequency of 57L mutation was detected in 8.2% of P. vivax isolates. This frequency was significantly increased when compared with a similar study on P. vivax isolates in 2005 (X(2) test, P<0.0001). Moreover, there was an increase in the frequency of single nucleotide polymorphisms at position 383G in pvdhps (0-2.6%) was found. Furthermore, the number of haplotypes increased from 6 to 12 in the study areas during 2006-2010. Interestingly, when combining the two loci, the frequency of parasites carrying pvdhfr/pvdhps pure mutations (L(57)R(58)/G(383), R(58)N(117)/G(383)) increased from 0% in 2006 to 2.1% in 2010. In conclusion, the present results suggest that SP could be effective in treatment against the erythrocytic stages of vivax malaria in Iran; however, the increased frequency of mutant haplotypes in Iran since 2006 is worrying and indicates the emergence of drug-tolerant/resistant P. vivax isolates in Iran in near future.
Collapse
Affiliation(s)
- Mandana Afsharpad
- Malaria and Vector Research Group (MVRG), Biotechnology Research Center (BRC), Pasteur Institute of Iran, Pasteur Avenue, P.O. Box 1316943551, Tehran, Iran
| | | | | | | |
Collapse
|
206
|
Salcedo-Sora JE, Ochong E, Beveridge S, Johnson D, Nzila A, Biagini GA, Stocks PA, O'Neill PM, Krishna S, Bray PG, Ward SA. The molecular basis of folate salvage in Plasmodium falciparum: characterization of two folate transporters. J Biol Chem 2011; 286:44659-68. [PMID: 21998306 PMCID: PMC3247980 DOI: 10.1074/jbc.m111.286054] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
Tetrahydrofolates are essential cofactors for DNA synthesis and methionine metabolism. Malaria parasites are capable both of synthesizing tetrahydrofolates and precursors de novo and of salvaging them from the environment. The biosynthetic route has been studied in some detail over decades, whereas the molecular mechanisms that underpin the salvage pathway lag behind. Here we identify two functional folate transporters (named PfFT1 and PfFT2) and delineate unexpected substrate preferences of the folate salvage pathway in Plasmodium falciparum. Both proteins are localized in the plasma membrane and internal membranes of the parasite intra-erythrocytic stages. Transport substrates include folic acid, folinic acid, the folate precursor p-amino benzoic acid (pABA), and the human folate catabolite pABAGn. Intriguingly, the major circulating plasma folate, 5-methyltetrahydrofolate, was a poor substrate for transport via PfFT2 and was not transported by PfFT1. Transport of all folates studied was inhibited by probenecid and methotrexate. Growth rescue in Escherichia coli and antifolate antagonism experiments in P. falciparum indicate that functional salvage of 5-methyltetrahydrofolate is detectable but trivial. In fact pABA was the only effective salvage substrate at normal physiological levels. Because pABA is neither synthesized nor required by the human host, pABA metabolism may offer opportunities for chemotherapeutic intervention.
Collapse
Affiliation(s)
- J Enrique Salcedo-Sora
- Molecular and Biochemical Parasitology Group, Liverpool School of Tropical Medicine, Liverpool L3 5QA, United Kingdom
| | | | | | | | | | | | | | | | | | | | | |
Collapse
|
207
|
Andriantsoanirina V, Durand R, Pradines B, Baret E, Bouchier C, Ratsimbasoa A, Ménard D. In vitro susceptibility to pyrimethamine of DHFR I164L single mutant Plasmodium falciparum. Malar J 2011; 10:283. [PMID: 21951962 PMCID: PMC3192713 DOI: 10.1186/1475-2875-10-283] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/18/2011] [Accepted: 09/27/2011] [Indexed: 11/17/2022] Open
Abstract
Background Recently, Plasmodium falciparum parasites bearing Pfdhfr I164L single mutation were found in Madagascar. These new mutants may challenge the use of antifolates for the intermittent preventive treatment of malaria during pregnancy (IPTp). Assays with transgenic bacteria suggested that I164L parasites have a wild-type phenotype for pyrimethamine but it had to be confirmed by testing the parasites themselves. Methods Thirty Plasmodium falciparum clinical isolates were collected in 2008 in the south-east of Madagascar. A part of Pfdhfr gene encompassing codons 6 to 206 was amplified by PCR and the determination of the presence of single nucleotide polymorphisms was performed by DNA sequencing. The multiplicity of infection was estimated by using an allelic family-specific nested PCR. Isolates that appeared monoclonal were submitted to culture adaptation. Determination of IC50s to pyrimethamine was performed on adapted isolates. Results Four different Pfdhfr alleles were found: the 164L single mutant-type (N = 13), the wild-type (N = 7), the triple mutant-type 51I/59R/108N (N = 9) and the double mutant-type 108N/164L (N = 1). Eleven out 30 (36.7%) of P. falciparum isolates were considered as monoclonal infection. Among them, five isolates were successfully adapted in culture and tested for pyrimethamine in vitro susceptibility. The wild-type allele was the most susceptible with a 50% inhibitory concentration (IC50) < 10 nM. The geometric mean of IC50 of the three I164L mutant isolates was 6-fold higher than the wild-type with 61.3 nM (SD = 3.2 nM, CI95%: 53.9-69.7 nM). These values remained largely below the IC50 of the triple mutant parasite (13,804 nM). Conclusion The IC50s of the I164L mutant isolates were significantly higher than those of the wild-type (6-fold higher) and close from those usually reported for simple mutants S108N (roughly10-fold higher than wild type). Given the observed values, the determination of IC50s directly on parasites did not confirm what has been found on transgenic bacteria. The prevalence increase of the Pfdhfr I164L single mutant parasite since 2006 could be explained by the selective advantage of this allele under sulphadoxine-pyrimethamine pressure. The emergence of highly resistant alleles should be considered in the future, in particular because an unexpected double mutant-type allele S108N/I164L has been already detected.
Collapse
|
208
|
Gama BE, Pereira-Carvalho GAL, Lutucuta Kosi FJI, Almeida de Oliveira NK, Fortes F, Rosenthal PJ, do Rosário VE, Daniel-Ribeiro CT, de Fátima Ferreira-da-Cruz M. Molecular markers of antifolate resistance in Plasmodium falciparum isolates from Luanda, Angola. Malar J 2011; 10:248. [PMID: 21864379 PMCID: PMC3176256 DOI: 10.1186/1475-2875-10-248] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/09/2011] [Accepted: 08/24/2011] [Indexed: 12/04/2022] Open
Abstract
Background Plasmodium falciparum malaria remains a leading health problem in Africa and its control is seriously challenged by drug resistance. Although resistance to the sulphadoxine-pyrimethamine (SP) is widespread, this combination remains an important component of malaria control programmes as intermittent preventive therapy (IPT) for pregnant women and children. In Angola, resistance patterns have been poorly characterized, and IPT has been employed for pregnant women since 2006. The aim of this study was to assess the prevalence of key antifolate resistance mediating polymorphisms in the pfdhfr and pfdhps genes in P. falciparum samples from Angola. Methods Plasmodium falciparum samples collected in Luanda, in 2007, were genotyped by amplification and DNA forward and reverse sequencing of the pfdhfr and pfdhps genes. Results The most prevalent polymorphisms identified were pfdhfr 108N (100%), 51I (93%), 59R (57%) and pfdhps 437G (93%). Resistance-mediating polymorphisms in pfdhps less commonly observed in West Africa were also identified (540E in 10%, 581G in 7% of samples). Conclusion This study documents an important prevalence of 4 P. falciparum polymorphisms that predicts an antifolate resistance in Luanda. Further, some samples presented additional mutations associated to high-level resistance. These results suggest that the use of SP for IPT may no longer be warranted in Angola.
Collapse
Affiliation(s)
- Bianca E Gama
- Laboratory of Malaria Research, Instituto Oswaldo Cruz, Fiocruz, Rio de Janeiro, Brazil
| | | | | | | | | | | | | | | | | |
Collapse
|
209
|
Kuesap J, Rungsrihirunrat K, Thongdee P, Ruangweerayut R, Na-Bangchang K. Change in mutation patterns of Plasmodium vivax dihydrofolate reductase (Pvdhfr) and dihydropteroate synthase (Pvdhps) in P. vivax isolates from malaria endemic areas of Thailand. Mem Inst Oswaldo Cruz 2011; 106 Suppl 1:130-3. [DOI: 10.1590/s0074-02762011000900017] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2010] [Accepted: 02/16/2011] [Indexed: 11/21/2022] Open
|
210
|
Adane L, Bharatam PV. Binding modes of 2,4-diaminoquinazoline and 2,4-diaminopteridine analogs to P. falciparum dihydrofolate reductase enzyme: Molecular docking studies. Indian J Pharm Sci 2011; 72:324-33. [PMID: 21188041 PMCID: PMC3003165 DOI: 10.4103/0250-474x.70478] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/20/2009] [Revised: 02/03/2010] [Accepted: 04/20/2010] [Indexed: 11/30/2022] Open
Abstract
A molecular docking study was carried out on 28 compounds belonging to 2,4-diaminoquinazoline and 2,4-diaminopteridine analogs using Glide, FlexX and GOLD programs and the X-ray crystallographic structures of the quadruple mutant (1J3K:pdb) and wild type (1J3I:pdb) Plasmodium falciparum dihydrofolate reductase enzyme. The experimental conformation the bound ligand WR99210 was precisely reproduced by the docking procedures as demonstrated by low (<2.00 Å) root-mean-square deviations. The results indicated that most of the compounds dock into the active sites of both the wild type and quadruple mutant P. falciparum dihydrofolate reductase enzymes. Visual inspection of the binding modes also demonstrated that most of the compounds could form H-bond interactions with the key amino acid residues (Asp54, Ile14 and Leu/Ile164) and with better docking scores than the bound compound (5). Their long side chains orient in the hydrophobic portion of the active site which is occupied by trichloro aryloxy side chain of WR99210 (5). Thus, avoid potential steric clashes with Asn108 (mutated from Ser108). Such a clash is known to be responsible for the resistance of the P. falciparum to pyrimethamine and cycloguanil.
Collapse
Affiliation(s)
- L Adane
- Department of Medicinal Chemistry, National Institute of Pharmaceutical Education and Research (NIPER), S.A.S. Nagar-160 062, India
| | | |
Collapse
|
211
|
Muregi FW, Ohta I, Masato U, Kino H, Ishih A. Resistance of a rodent malaria parasite to a thymidylate synthase inhibitor induces an apoptotic parasite death and imposes a huge cost of fitness. PLoS One 2011; 6:e21251. [PMID: 21698180 PMCID: PMC3116895 DOI: 10.1371/journal.pone.0021251] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2010] [Accepted: 05/25/2011] [Indexed: 01/09/2023] Open
Abstract
Background The greatest impediment to effective malaria control is drug resistance in Plasmodium falciparum, and thus understanding how resistance impacts on the parasite's fitness and pathogenicity may aid in malaria control strategy. Methodology/Principal Findings To generate resistance, P. berghei NK65 was subjected to 5-fluoroorotate (FOA, an inhibitor of thymidylate synthase, TS) pressure in mice. After 15 generations of drug pressure, the 2% DT (the delay time for proliferation of parasites to 2% parasitaemia, relative to untreated wild-type controls) reduced from 8 days to 4, equalling the controls. Drug sensitivity studies confirmed that FOA-resistance was stable. During serial passaging in the absence of drug, resistant parasite maintained low growth rates (parasitaemia, 15.5%±2.9, 7 dpi) relative to the wild-type (45.6%±8.4), translating into resistance cost of fitness of 66.0%. The resistant parasite showed an apoptosis-like death, as confirmed by light and transmission electron microscopy and corroborated by oligonucleosomal DNA fragmentation. Conclusions/Significance The resistant parasite was less fit than the wild-type, which implies that in the absence of drug pressure in the field, the wild-type alleles may expand and allow drugs withdrawn due to resistance to be reintroduced. FOA resistance led to depleted dTTP pools, causing thymineless parasite death via apoptosis. This supports the tenet that unicellular eukaryotes, like metazoans, also undergo apoptosis. This is the first report where resistance to a chemical stimulus and not the stimulus itself is shown to induce apoptosis in a unicellular parasite. This finding is relevant in cancer therapy, since thymineless cell death induced by resistance to TS-inhibitors can further be optimized via inhibition of pyrimidine salvage enzymes, thus providing a synergistic impact. We conclude that since apoptosis is a process that can be pharmacologically modulated, the parasite's apoptotic machinery may be exploited as a novel drug target in malaria and other protozoan diseases of medical importance.
Collapse
Affiliation(s)
- Francis W Muregi
- Department of Infectious Diseases, Hamamatsu University School of Medicine, Hamamatsu, Japan.
| | | | | | | | | |
Collapse
|
212
|
Zaman J, Shahbazi A, Asgharzadeh M. Plasmodium vivax dhfr mutations among isolates from malarious areas of Iran. THE KOREAN JOURNAL OF PARASITOLOGY 2011; 49:125-31. [PMID: 21738267 PMCID: PMC3121068 DOI: 10.3347/kjp.2011.49.2.125] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 10/17/2010] [Revised: 01/03/2011] [Accepted: 04/05/2011] [Indexed: 11/26/2022]
Abstract
The use of sulfadoxine and pyrimethamine (SP) for treatment of vivax malaria is uncommon in most malarious areas, but Plasmodium vivax isolates are exposed to SP because of mixed infections with other Plasmodium species. As P. vivax is the most prevalent species of human malaria parasites in Iran, monitoring of resistance of the parasite against the drug is necessary. In the present study, 50 blood samples of symptomatic patients were collected from 4 separated geographical regions of south-east Iran. Point mutations at residues 57, 58, 61, and 117 were detected by the PCR-RFLP method. Polymorphism at positions 58R, 117N, and 117T of P. vivax dihydrofolate reductase (Pvdhfr) gene has been found in 12%, 34%, and 2% of isolates, respectively. Mutation at residues F57 and T61 was not detected. Five distinct haplotypes of the Pvdhfr gene were demonstrated. The 2 most prevalent haplotypes were F57S58T61S117 (62%) and F57S58T61N117 (24%). Haplotypes with 3 and 4 point mutations were not found. The present study suggested that P. vivax in Iran is under the pressure of SP and the sensitivity level of the parasite to SP is diminishing and this fact must be considered in development of malaria control programs.
Collapse
Affiliation(s)
- Jalal Zaman
- Tabriz University of Medical Sciences, Tabriz, Iran
| | | | | |
Collapse
|
213
|
Gravestock D, Rousseau AL, Lourens AC, Moleele SS, van Zyl RL, Steenkamp PA. Expeditious synthesis and biological evaluation of novel 2,N6-disubstituted 1,2-dihydro-1,3,5-triazine-4,6-diamines as potential antimalarials. Eur J Med Chem 2011; 46:2022-30. [DOI: 10.1016/j.ejmech.2011.02.054] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2010] [Revised: 02/10/2011] [Accepted: 02/22/2011] [Indexed: 11/25/2022]
|
214
|
Costanzo MS, Brown KM, Hartl DL. Fitness trade-offs in the evolution of dihydrofolate reductase and drug resistance in Plasmodium falciparum. PLoS One 2011; 6:e19636. [PMID: 21625425 PMCID: PMC3100297 DOI: 10.1371/journal.pone.0019636] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2010] [Accepted: 04/10/2011] [Indexed: 12/04/2022] Open
Abstract
BACKGROUND Patterns of emerging drug resistance reflect the underlying adaptive landscapes for specific drugs. In Plasmodium falciparum, the parasite that causes the most serious form of malaria, antifolate drugs inhibit the function of essential enzymes in the folate pathway. However, a handful of mutations in the gene coding for one such enzyme, dihydrofolate reductase, confer drug resistance. Understanding how evolution proceeds from drug susceptibility to drug resistance is critical if new antifolate treatments are to have sustained usefulness. METHODOLOGY/PRINCIPAL FINDINGS We use a transgenic yeast expression system to build on previous studies that described the adaptive landscape for the antifolate drug pyrimethamine, and we describe the most likely evolutionary trajectories for the evolution of drug resistance to the antifolate chlorcycloguanil. We find that the adaptive landscape for chlorcycloguanil is multi-peaked, not all highly resistant alleles are equally accessible by evolution, and there are both commonalities and differences in adaptive landscapes for chlorcycloguanil and pyrimethamine. CONCLUSIONS/SIGNIFICANCE Our findings suggest that cross-resistance between drugs targeting the same enzyme reflect the fitness landscapes associated with each particular drug and the position of the genotype on both landscapes. The possible public health implications of these findings are discussed.
Collapse
Affiliation(s)
- Marna S Costanzo
- Department of Organismic and Evolutionary Biology, Harvard University, Cambridge, Massachusetts, United States of America.
| | | | | |
Collapse
|
215
|
Kathpal A, Patakottu BR, Patankar S. FORS-D Analysis in P. falciparum can Differentiate Classes of Genes Under Selection. Evol Bioinform Online 2011; 7:21-9. [PMID: 21487534 PMCID: PMC3072625 DOI: 10.4137/ebo.s6609] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
FORS-D is a measure of the contribution of base order to the stem loop potential of a nucleic acid sequence and can also give information on evolutionary pressures on sequences to move away from secondary structure. Negative FORS-D values in a gene are associated with exons and nucleotide substitutions such as SNPs. An analysis of P. falciparum genes under selection pressure shows a correlation between negative FORS-D values and SNP density for genes that drug targets but not for drug transporters or antigenic variation genes. Analysis of the dhfr gene shows that a majority of rare mutations that associate with drug resistance also fall into regions with negative FORS-D values. These data suggest that FORS-D values might be predictors for drug target genes and drug resistance mutations in these genes.
Collapse
Affiliation(s)
- Atish Kathpal
- Birla Institute of Technology and Science, Pilani, Goa Campus, Zuarinagar 403726, Goa, India
| | | | | |
Collapse
|
216
|
Ghanchi NK, Ursing J, Beg MA, Veiga MI, Jafri S, Mårtensson A. Prevalence of resistance associated polymorphisms in Plasmodium falciparum field isolates from southern Pakistan. Malar J 2011; 10:18. [PMID: 21272384 PMCID: PMC3037930 DOI: 10.1186/1475-2875-10-18] [Citation(s) in RCA: 30] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/21/2010] [Accepted: 01/28/2011] [Indexed: 01/23/2023] Open
Abstract
BACKGROUND Scarce data are available on Plasmodium falciparum anti-malarial drug resistance in Pakistan. The aim of this study was, therefore, to determine the prevalence of P. falciparum resistance associated polymorphisms in field isolates from southern Pakistan. METHODS Blood samples from 244 patients with blood-slide confirmed P. falciparum mono-infections were collected between 2005-2007. Single nucleotide polymorphisms in the P. falciparum chloroquine resistance transporter (pfcrt K76T), multi drug resistance (pfmdr1 N86Y), dihydrofolate reductase (pfdhfr A16V, N51I, C59R, S108N, I164L) and dihydropteroate synthetase (pfdhps A436S, G437A and E540K) genes and pfmdr1 gene copy numbers were determined using PCR based methods. RESULTS The prevalence of pfcrt 76T and pfmdr1 86Y was 93% and 57%, respectively. The prevalence of pfdhfr double mutations 59R + 108N/51R + 108N was 92%. The pfdhfr triple mutation (51I, 59R, 108N) occurred in 3% of samples. The pfdhfr (51I, 59R, 108N) and pfdhps (437G, 540E) quintuple mutation was found in one isolate. Pfdhps 437G was observed in 51% and 540E in 1% of the isolates. One isolate had two pfmdr1 copies and carried the pfmdr1 86Y and pfcrt 76T alleles. CONCLUSIONS The results indicate high prevalence of in vivo resistance to chloroquine, whereas high grade resistance to sulphadoxine-pyrimethamine does not appear to be widespread among P. falciparum in southern Pakistan.
Collapse
Affiliation(s)
- Najia Karim Ghanchi
- Department of Pathology and Microbiology, Aga Khan University, Stadium Road, P.O. Box 3500, Karachi 74800, Pakistan
| | - Johan Ursing
- Malaria Research Lab, Infectious Diseases Unit, Department of Medicine, Karolinska University Hospital/Karolinska Institutet, Retziusväg 10, 171 77 Stockholm, Sweden
| | - Mohammad A Beg
- Department of Pathology and Microbiology, Aga Khan University, Stadium Road, P.O. Box 3500, Karachi 74800, Pakistan
| | - Maria I Veiga
- Malaria Research Lab, Infectious Diseases Unit, Department of Medicine, Karolinska University Hospital/Karolinska Institutet, Retziusväg 10, 171 77 Stockholm, Sweden
- Drug Resistance and Pharmacogenetics Group, Institute of Biotechnology and Bioengineering, Centre of Molecular and Structural Biomedicine, University of Algarve, 8500-139 Faro, Portugal
| | - Sana Jafri
- Department of Pathology and Microbiology, Aga Khan University, Stadium Road, P.O. Box 3500, Karachi 74800, Pakistan
| | - Andreas Mårtensson
- Malaria Research Lab, Infectious Diseases Unit, Department of Medicine, Karolinska University Hospital/Karolinska Institutet, Retziusväg 10, 171 77 Stockholm, Sweden
- Division of Global Health (IHCAR), Department of Public Health Sciences, Karolinska Institutet, Nobelsväg 9, S-171 77 Stockholm, Sweden
| |
Collapse
|
217
|
Alam MT, de Souza DK, Vinayak S, Griffing SM, Poe AC, Duah NO, Ghansah A, Asamoa K, Slutsker L, Wilson MD, Barnwell JW, Udhayakumar V, Koram KA. Selective sweeps and genetic lineages of Plasmodium falciparum drug -resistant alleles in Ghana. J Infect Dis 2011; 203:220-7. [PMID: 21288822 PMCID: PMC3071065 DOI: 10.1093/infdis/jiq038] [Citation(s) in RCA: 65] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
BACKGROUND In 2005, Ghana adopted artemisinin-based combination therapy (ACT) for primary treatment of falciparum malaria. A comprehensive study of the drug-resistance-associated mutations and their genetic lineages will lead to a better understanding of the evolution of antimalarial drug resistance in this region. METHODS The pfcrt, pfmdr1, dhps, and dhfr mutations associated with chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) resistance and the microsatellite loci flanking these genes were genotyped in Plasmodium falciparum isolates from Ghana. RESULTS The prevalence of mutations associated with both CQ and SP resistance was high in Ghana. However, we observed a decrease in prevalence of the pfcrt K76T mutation in northern Ghana after the change in drug policy from CQ to ACT. Analysis of genetic diversity and differentiation at microsatellite loci flanking all 4 genes indicated that they have been under strong selection, because of CQ and SP use. The triple-mutant pfcrt and dhfr alleles in Ghana were derived from Southeast Asia, whereas the double-mutant dhfr, dhps, and pfmdr1 alleles were of African lineage. CONCLUSION Because of the possible role of pfmdr1 in amodiaquine and mefloquine resistance, demonstrating selection on pfmdr1 and defining lineages of resistant alleles in an African population holds great importance.
Collapse
Affiliation(s)
- Md Tauqeer Alam
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, Atlanta, GA 30329, USA.
| | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
218
|
Miao M, Yang Z, Cui L, Ahlum J, Huang Y, Cui L. Different allele prevalence in the dihydrofolate reductase and dihydropteroate synthase genes in Plasmodium vivax populations from China. Am J Trop Med Hyg 2011; 83:1206-11. [PMID: 21118923 DOI: 10.4269/ajtmh.2010.10-0259] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/12/2023] Open
Abstract
Antifolate resistance in Plasmodium vivax is caused by point mutations in genes encoding dihydrofolate reductase (pvdhfr) and dihydropteroate synthase (pvdhps). In this study, we used direct sequencing to survey pvdhfr and pvdhps mutations in 122 clinical P. vivax isolates from a central and a southern province of China. For pvdhfr, 36.9% were wild-type, whereas mutations were detected at four codons (57, 58, 61, and 117). The S117N/T mutation was the most prevalent (48.4%), followed by the T61M mutation (18.9%). Six pvdhfr mutant alleles were found, ranging from 37.7% to 0.8%. The dramatically different pvdhfr allele frequencies between the two P. vivax populations might be caused by different drug histories or intrinsic difference between temperate and subtropical strains. In contrast, except polymorphisms within a repeat region, no resistance-conferring mutations were detected in pvdhps. Our result suggests that P. vivax populations in China may be relatively susceptible to sulfadoxine-pyrimethamine.
Collapse
Affiliation(s)
- Miao Miao
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania 16802, USA.
| | | | | | | | | | | |
Collapse
|
219
|
Plasmodium vivax: Prevalence of mutations associated with sulfadoxine–pyrimethamine resistance in Plasmodium vivax clinical isolates from Pakistan. Exp Parasitol 2011; 127:167-72. [DOI: 10.1016/j.exppara.2010.07.011] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Revised: 07/17/2010] [Accepted: 07/19/2010] [Indexed: 11/22/2022]
|
220
|
Ferrari S, Morandi F, Motiejunas D, Nerini E, Henrich S, Luciani R, Venturelli A, Lazzari S, Calò S, Gupta S, Hannaert V, Michels PAM, Wade RC, Costi MP. Virtual Screening Identification of Nonfolate Compounds, Including a CNS Drug, as Antiparasitic Agents Inhibiting Pteridine Reductase. J Med Chem 2010; 54:211-21. [DOI: 10.1021/jm1010572] [Citation(s) in RCA: 54] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Affiliation(s)
- Stefania Ferrari
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| | - Federica Morandi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| | - Domantas Motiejunas
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| | - Erika Nerini
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
- Heidelberg Institute for Theoretical Studies (HITS) gGmbH, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
| | - Stefan Henrich
- Heidelberg Institute for Theoretical Studies (HITS) gGmbH, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
| | - Rosaria Luciani
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| | - Alberto Venturelli
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| | - Sandra Lazzari
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| | - Samuele Calò
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| | - Shreedhara Gupta
- Research Unit for Tropical Diseases, de Duve Institute and Laboratory of Biochemistry, Université catholique de Louvain, Avenue Hippocrate 74, B-1200 Brussels, Belgium
| | - Veronique Hannaert
- Research Unit for Tropical Diseases, de Duve Institute and Laboratory of Biochemistry, Université catholique de Louvain, Avenue Hippocrate 74, B-1200 Brussels, Belgium
| | - Paul A. M. Michels
- Research Unit for Tropical Diseases, de Duve Institute and Laboratory of Biochemistry, Université catholique de Louvain, Avenue Hippocrate 74, B-1200 Brussels, Belgium
| | - Rebecca C. Wade
- Heidelberg Institute for Theoretical Studies (HITS) gGmbH, Schloss-Wolfsbrunnenweg 35, 69118 Heidelberg, Germany
| | - M. Paola Costi
- Dipartimento di Scienze Farmaceutiche, Università degli Studi di Modena e Reggio Emilia, Via Campi 183, 41100 Modena, Italy
| |
Collapse
|
221
|
Müller IB, Hyde JE. Antimalarial drugs: modes of action and mechanisms of parasite resistance. Future Microbiol 2010; 5:1857-73. [DOI: 10.2217/fmb.10.136] [Citation(s) in RCA: 69] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/16/2023] Open
Abstract
Malaria represents one of the most serious threats to human health worldwide, and preventing and curing this parasitic disease still depends predominantly on the administration of a small number of drugs whose efficacy is continually threatened and eroded by the emergence of drug-resistant parasite populations. This has an enormous impact on the mortality and morbidity resulting from malaria infection, especially in sub-Saharan Africa, where the lethal human parasite species Plasmodium falciparum accounts for approximately 90% of deaths recorded globally. Successful treatment of uncomplicated malaria is now highly dependent on artemisinin-based combination therapies. However, the first cases of artemisinin-resistant field isolates have been reported recently and potential replacement antimalarials are only in the developmental stages. Here, we summarize recent progress in tackling the problem of parasite resistance and discuss the underlying molecular mechanisms that confer resistance to current antimalarial agents as far as they are known, understanding of which should assist in the rational development of new drugs and the more effective deployment of older ones.
Collapse
Affiliation(s)
- Ingrid B Müller
- Department of Biochemistry, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany
| | - John E Hyde
- Manchester Interdisciplinary Biocentre, Faculty of Life Sciences, University of Manchester, 131 Princess Street, Manchester, M1 7DN, UK
| |
Collapse
|
222
|
Tracking origins and spread of sulfadoxine-resistant Plasmodium falciparum dhps alleles in Thailand. Antimicrob Agents Chemother 2010; 55:155-64. [PMID: 20956597 DOI: 10.1128/aac.00691-10] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The emergence and spread of drug-resistant Plasmodium falciparum have been a major impediment for the control of malaria worldwide. Earlier studies have shown that similar to chloroquine (CQ) resistance, high levels of pyrimethamine resistance in P. falciparum originated independently 4 to 5 times globally, including one origin at the Thailand-Cambodia border. In this study we describe the origins and spread of sulfadoxine-resistance-conferring dihydropteroate synthase (dhps) alleles in Thailand. The dhps mutations and flanking microsatellite loci were genotyped for P. falciparum isolates collected from 11 Thai provinces along the Burma, Cambodia, and Malaysia borders. Results indicated that resistant dhps alleles were fixed in Thailand, predominantly being the SGEGA, AGEAA, and SGNGA triple mutants and the AGKAA double mutant (mutated codons are underlined). These alleles had different geographical distributions. The SGEGA alleles were found mostly at the Burma border, while the SGNGA alleles occurred mainly at the Cambodia border and nearby provinces. Microsatellite data suggested that there were two major genetic lineages of the triple mutants in Thailand, one common for SGEGA/SGNGA alleles and another one independent for AGEAA. Importantly, the newly reported SGNGA alleles possibly originated at the Thailand-Cambodia border. All parasites in the Yala province (Malaysia border) had AGKAA alleles with almost identical flanking microsatellites haplotypes. They were also identical at putatively neutral loci on chromosomes 2 and 3, suggesting a clonal nature of the parasite population in Yala. In summary, this study suggests multiple and independent origins of resistant dhps alleles in Thailand.
Collapse
|
223
|
Ballif M, Hii J, Marfurt J, Crameri A, Fafale A, Felger I, Beck HP, Genton B. Monitoring of malaria parasite resistance to chloroquine and sulphadoxine-pyrimethamine in the Solomon Islands by DNA microarray technology. Malar J 2010; 9:270. [PMID: 20925934 PMCID: PMC2959069 DOI: 10.1186/1475-2875-9-270] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2010] [Accepted: 10/06/2010] [Indexed: 11/14/2022] Open
Abstract
Background Little information is available on resistance to anti-malarial drugs in the Solomon Islands (SI). The analysis of single nucleotide polymorphisms (SNPs) in drug resistance associated parasite genes is a potential alternative to classical time- and resource-consuming in vivo studies to monitor drug resistance. Mutations in pfmdr1 and pfcrt were shown to indicate chloroquine (CQ) resistance, mutations in pfdhfr and pfdhps indicate sulphadoxine-pyrimethamine (SP) resistance, and mutations in pfATPase6 indicate resistance to artemisinin derivatives. Methods The relationship between the rate of treatment failure among 25 symptomatic Plasmodium falciparum-infected patients presenting at the clinic and the pattern of resistance-associated SNPs in P. falciparum infecting 76 asymptomatic individuals from the surrounding population was investigated. The study was conducted in the SI in 2004. Patients presenting at a local clinic with microscopically confirmed P. falciparum malaria were recruited and treated with CQ+SP. Rates of treatment failure were estimated during a 28-day follow-up period. In parallel, a DNA microarray technology was used to analyse mutations associated with CQ, SP, and artemisinin derivative resistance among samples from the asymptomatic community. Mutation and haplotype frequencies were determined, as well as the multiplicity of infection. Results The in vivo study showed an efficacy of 88% for CQ+SP to treat P. falciparum infections. DNA microarray analyses indicated a low diversity in the parasite population with one major haplotype present in 98.7% of the cases. It was composed of fixed mutations at position 86 in pfmdr1, positions 72, 75, 76, 220, 326 and 356 in pfcrt, and positions 59 and 108 in pfdhfr. No mutation was observed in pfdhps or in pfATPase6. The mean multiplicity of infection was 1.39. Conclusion This work provides the first insight into drug resistance markers of P. falciparum in the SI. The obtained results indicated the presence of a very homogenous P. falciparum population circulating in the community. Although CQ+SP could still clear most infections, seven fixed mutations associated with CQ resistance and two fixed mutations related to SP resistance were observed. Whether the absence of mutations in pfATPase6 indicates the efficacy of artemisinin derivatives remains to be proven.
Collapse
Affiliation(s)
- Marie Ballif
- Swiss Tropical and Public Health Institute, Department of Medical Parasitology and Biology of Infection, Department of Epidemiology and Public Health, Socinstrasse 57, 4002 Basel, Switzerland
| | | | | | | | | | | | | | | |
Collapse
|
224
|
Ojha PK, Roy K. Chemometric modelling of antimalarial activity of aryltriazolylhydroxamates. MOLECULAR SIMULATION 2010. [DOI: 10.1080/08927022.2010.492835] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/18/2022]
|
225
|
Martinelli A, Henriques G, Cravo P, Hunt P. Whole genome re-sequencing identifies a mutation in an ABC transporter (mdr2) in a Plasmodium chabaudi clone with altered susceptibility to antifolate drugs. Int J Parasitol 2010; 41:165-71. [PMID: 20858498 PMCID: PMC3034870 DOI: 10.1016/j.ijpara.2010.08.008] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2010] [Revised: 07/27/2010] [Accepted: 08/13/2010] [Indexed: 12/16/2022]
Abstract
In malaria parasites, mutations in two genes of folate biosynthesis encoding dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) modify responses to antifolate therapies which target these enzymes. However, the involvement of other genes which modify the availability of exogenous folate, for example, has been proposed. Here, we used short-read whole-genome re-sequencing to determine the mutations in a clone of the rodent malaria parasite, Plasmodium chabaudi, which has altered susceptibility to both sulphadoxine and pyrimethamine. This clone bears a previously identified S106N mutation in dhfr and no mutation in dhps. Instead, three additional point mutations in genes on chromosomes 2, 13 and 14 were identified. The mutated gene on chromosome 13 (mdr2 K392Q) encodes an ABC transporter. Because Quantitative Trait Locus analysis previously indicated an association of genetic markers on chromosome 13 with responses to individual and combined antifolates, MDR2 is proposed to modulate antifolate responses, possibly mediated by the transport of folate intermediates.
Collapse
Affiliation(s)
- Axel Martinelli
- Centro de Malaria e Outras Doenças Tropicais/IHMT/UEI Biologia Molecular, Universidade Nova de Lisboa, Rua da Junqueira 96, 1349-008 Lisbon, Portugal.
| | | | | | | |
Collapse
|
226
|
Non-variant specific antibody responses to the C-terminal region of merozoite surface protein-1 of Plasmodium falciparum (PfMSP-119) in Iranians exposed to unstable malaria transmission. Malar J 2010; 9:257. [PMID: 20846388 PMCID: PMC2945361 DOI: 10.1186/1475-2875-9-257] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2010] [Accepted: 09/16/2010] [Indexed: 11/12/2022] Open
Abstract
Background The C-terminal region of Plasmodium falciparum merozoite surface protein-1 (PfMSP-119) is a leading malaria vaccine candidate antigen. However, the existence of different variants of this antigen can limit efficacy of the vaccine development based on this protein. Therefore, in this study, the main objective was to define the frequency of PfMSP-119 haplotypes in malaria hypoendemic region of Iran and also to analyse cross-reactive and/or variant-specific antibody responses to four PfMSP-119 variant forms. Methods The PfMSP-119 was genotyped in 50 infected subjects with P. falciparum collected during 2006-2008. Four GST-PfMSP-119 variants (E/TSR/L, E/TSG/L, E/KNG/F and Q/KNG/L) were produced in Escherichia coli and naturally occurring IgG antibody to these proteins was evaluated in malaria patients' sera (n = 50) using ELISA. To determine the cross-reactivity of antibodies against each PfMSP-119 variant in P. falciparum-infected human sera, an antibody depletion assay was performed in eleven corresponding patients' sera. Results Sequence data of the PfMSP-119 revealed five variant forms in which the haplotypes Q/KNG/L and Q/KNG/F were predominant types and the second most frequent haplotype was E/KNG/F. In addition, the prevalence of IgG antibodies to all four PfMSP-119 variant forms was equal and high (84%) among the studied patients' sera. Immunodepletion results showed that in Iranian malaria patients, Q/KNG/L variant could induce not only cross-reactive antibody responses to other PfMSP-119 variants, but also could induce some specific antibodies that are not able to recognize the E/TSG/L or E/TSR/L variant forms. Conclusion The present findings demonstrated the presence of non-variant specific antibodies to PfMSP-119 in Iranian falciparum malaria patients. This data suggests that polymorphism in PfMSP-119 is less important and one variant of this antigen, particularly Q/KNG/L, may be sufficient to be included in PfMSP-119-based vaccine.
Collapse
|
227
|
de Almeida A, Rosário VED, Henriques G, Arez AP, Cravo P. Plasmodium vivax in the Democratic Republic of East Timor: Parasite prevalence and antifolate resistance-associated mutations. Acta Trop 2010; 115:288-92. [PMID: 20412783 DOI: 10.1016/j.actatropica.2010.04.008] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2009] [Revised: 04/08/2010] [Accepted: 04/12/2010] [Indexed: 10/19/2022]
Abstract
In the Democratic Republic of East Timor, Plasmodium falciparum and Plasmodium vivax malaria coexist, but limited information is available about the latter species. Consequently, the prevalence of P. vivax and of its corresponding antifolate resistance-associated mutations in the pvdhfr and pvdhps genes was assessed here. Blood samples were collected from 650 individuals distributed among six districts, over two different periods, by either passive case detection (PCD) or active case detection (ACD). As expected, malaria was over-represented in the PCD sample (26% PCD vs 5% ACD), because the infection increases medical care seeking. Additionally, the relative frequency of P. vivax infections in symptomatic individuals (37%) was twice as high as the one in the asymptomatic sampling group (18%), suggesting that that this parasite is accounting for a significant proportion malaria-attributed morbidity. The frequency of specific sulfadoxine-pyrimethamine resistance-associated mutations genes was ascertained in P. vivax positive samples by PCR-RFLP. Although no mutants were detected in codons 383 and 553 of pvdhps, 48%, 76% and 82% of P. vivax-infected samples harbored the dhfr 33L, 58R and 117N mutations, respectively. Additionally, the frequency of parasites carrying both pvdhfr 58R and 117N mutant alleles accounted for a third of all genotypes analyzed, most likely due to inadvertent SP use in the past. In conclusion, evidence-based information is provided to promote optimized drug deployment and limit the evolution of resistance to antifolate resistance in P. vivax from East Timor.
Collapse
|
228
|
Sridaran S, McClintock SK, Syphard LM, Herman KM, Barnwell JW, Udhayakumar V. Anti-folate drug resistance in Africa: meta-analysis of reported dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) mutant genotype frequencies in African Plasmodium falciparum parasite populations. Malar J 2010; 9:247. [PMID: 20799995 PMCID: PMC2940896 DOI: 10.1186/1475-2875-9-247] [Citation(s) in RCA: 81] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2010] [Accepted: 08/30/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Mutations in the dihydrofolate reductase (dhfr) and dihydropteroate synthase (dhps) genes of Plasmodium falciparum are associated with resistance to anti-folate drugs, most notably sulphadoxine-pyrimethamine (SP). Molecular studies document the prevalence of these mutations in parasite populations across the African continent. However, there is no systematic review examining the collective epidemiological significance of these studies. This meta-analysis attempts to: 1) summarize genotype frequency data that are critical for molecular surveillance of anti-folate resistance and 2) identify the specific challenges facing the development of future molecular databases. METHODS This review consists of 220 studies published prior to 2009 that report the frequency of select dhfr and dhps mutations in 31 African countries. Maps were created to summarize the location and prevalence of the highly resistant dhfr triple mutant (N51I, C59R, S108N) genotype and dhps double mutant (A437G and K540E) genotype in Africa. A hierarchical mixed effects logistic regression was used to examine the influence of various factors on reported mutant genotype frequency. These factors include: year and location of study, age and clinical status of sampled population, and reporting conventions for mixed genotype data. RESULTS A database consisting of dhfr and dhps mutant genotype frequencies from all African studies that met selection criteria was created for this analysis. The map illustrates particularly high prevalence of both the dhfr triple and dhps double mutant genotypes along the Kenya-Tanzania border and Malawi. The regression model shows a statistically significant increase in the prevalence of both the dhfr triple and dhps double mutant genotypes in Africa. CONCLUSION Increasing prevalence of the dhfr triple mutant and dhps double mutant genotypes in Africa are consistent with the loss of efficacy of SP for treatment of clinical malaria in most parts of this continent. Continued assessment of the effectiveness of SP for the treatment of clinical malaria and intermittent preventive treatment in pregnancy is needed. The creation of a centralized resistance data network, such as the one proposed by the WorldWide Antimalarial Resistance Network (WWARN), will become a valuable resource for planning timely actions to combat drug resistant malaria.
Collapse
Affiliation(s)
- Sankar Sridaran
- Malaria Branch, Division of Parasitic Diseases and Malaria, Center for Global Health, Centers for Disease Control and Prevention, 1600 Clifton road NE, Mail Stop D-67 Atlanta, GA, 30333, USA.
| | | | | | | | | | | |
Collapse
|
229
|
Gasasira AF, Kamya MR, Ochong EO, Vora N, Achan J, Charlebois E, Ruel T, Kateera F, Meya DN, Havlir D, Rosenthal PJ, Dorsey G. Effect of trimethoprim-sulphamethoxazole on the risk of malaria in HIV-infected Ugandan children living in an area of widespread antifolate resistance. Malar J 2010; 9:177. [PMID: 20573194 PMCID: PMC2903607 DOI: 10.1186/1475-2875-9-177] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2010] [Accepted: 06/23/2010] [Indexed: 11/15/2022] Open
Abstract
Background Daily trimethoprim-sulfamethoxazole (TS) protects against malaria, but efficacy may be diminished as anti-folate resistance increases. This study assessed the incidence of falciparum malaria and the prevalence of resistance-conferring Plasmodium falciparum mutations in HIV-infected children receiving daily TS and HIV-uninfected children not taking TS. Materials and methods Subjects were 292 HIV-infected and 517 uninfected children from two cohort studies in Kampala, Uganda observed from August 2006 to December 2008. Daily TS was given to HIV-infected, but not HIV-uninfected children and all participants were provided an insecticide-treated bed net. Standardized protocols were used to measure the incidence of malaria and identify markers of antifolate resistance. Results Sixty-five episodes of falciparum malaria occurred in HIV-infected and 491 episodes in uninfected children during the observation period. TS was associated with a protective efficacy of 80% (0.10 vs. 0.45 episodes per person year, p < 0.001), and efficacy did not vary over three consecutive 9.5 month periods (81%, 74%, 80% respectively, p = 0.506). The prevalences of dhfr 51I, 108N, and 59R and dhps 437G and 540E mutations were each over 90% among parasites infecting both HIV-infected and uninfected children. Prevalence of the dhfr 164L mutation, which is associated with high-level resistance, was significantly higher in parasites from HIV-infected compared to uninfected children (8% vs. 1%, p = 0.001). Sequencing of the dhfr and dhps genes identified only one additional polymorphism, dhps 581G, in 2 of 30 samples from HIV-infected and 0 of 54 samples from uninfected children. Conclusion Despite high prevalence of known anti-folate resistance-mediating mutations, TS prophylaxis was highly effective against malaria, but was associated with presence of dhfr 164L mutation.
Collapse
|
230
|
An analytical model for genetic hitchhiking in the evolution of antimalarial drug resistance. Theor Popul Biol 2010; 78:93-108. [PMID: 20600206 DOI: 10.1016/j.tpb.2010.06.005] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/05/2009] [Revised: 06/04/2010] [Accepted: 06/07/2010] [Indexed: 11/21/2022]
Abstract
We analytically study a deterministic model for the spread of drug resistance among human malaria parasites. The model incorporates all major characteristics of the complex malaria transmission cycle and accounts for the fact that only a fraction alpha of infected hosts receive drug treatment. Furthermore, the model incorporates that hosts can be co-infected. The number m of parasites co-infecting a host is either a constant or, more generally, follows a given frequency distribution. Although the model is formulated in a multilocus setup, for our results we assume that drug resistance is caused by a single locus with two alleles - a sensitive one and a resistant one. We assume that the resistant allele has a selective advantage only in treated hosts and pays metabolic costs, which causes this allele to be deleterious in untreated hosts. We provide necessary and sufficient conditions for the fixation of the resistant allele. Moreover, provided the resistant allele will sweep through the population, we derive a formula for the time until it reaches a given frequency and in particular for the time until quasi-fixation. Furthermore, we establish an analytical solution for allele frequency changes at a linked neutral biallelic locus due to the rapid increase in frequency of the resistant allele. Our solution describes a local reduction in heterozygosity among parasite chromosomes around the resistant allele, the effect commonly referred to as the hitchhiking effect, as a function of alpha and m. The result therefore allows the investigation of selective sweep patterns under specific demographic settings. We find that the hitchhiking effect is similar but different from the standard model of genetic hitchhiking that assumes random mating and homogeneous selection. In particular, the process of recombination and selection cannot be decoupled. We further explain why standard hitchhiking theory cannot be applied to drug resistance in malaria. Furthermore, we will show that a genome-wide reduction in relative heterozygosity can occur provided a fraction of hosts is infected by a single parasite haplotype. Finally, we show how to incorporate host heterogeneity, and generalize our results to this biologically more realistic case.
Collapse
|
231
|
Roy K, Ojha PK. Advances in quantitative structure–activity relationship models of antimalarials. Expert Opin Drug Discov 2010; 5:751-78. [DOI: 10.1517/17460441.2010.497812] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
232
|
Marma ASP, Mita T, Eto H, Tsukahara T, Sarker S, Endo H. High prevalence of sulfadoxine/pyrimethamine resistance alleles in Plasmodium falciparum parasites from Bangladesh. Parasitol Int 2010; 59:178-82. [DOI: 10.1016/j.parint.2010.01.003] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2009] [Revised: 12/20/2009] [Accepted: 01/15/2010] [Indexed: 10/19/2022]
|
233
|
Origin and dissemination across the Colombian Andes mountain range of sulfadoxine-pyrimethamine resistance in Plasmodium falciparum. Antimicrob Agents Chemother 2010; 54:3121-5. [PMID: 20498318 DOI: 10.1128/aac.00036-10] [Citation(s) in RCA: 19] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/19/2022] Open
Abstract
The therapeutic efficacy of sulfadoxine-pyrimethamine (SP) in treating uncomplicated Plasmodium falciparum malaria is unevenly distributed in Colombia. The Andes mountain range separates regions in the west where malaria is endemic from those in the east and constitutes a barrier against gene flow and the dispersal of parasite populations. The distribution of dhfr and dhps genotypes of 146 P. falciparum samples from the eastern Amazon and Orinoco basins and Northwest and Southwest Pacific regions of Colombia was consistent with the documented levels of therapeutic efficacy of SP. The diversity of four dhfr- and dhps-linked microsatellites indicated that double- and triple-mutant alleles for both resistance loci have a single origin. Likewise, multilocus association genotypes, including two unlinked microsatellite loci, suggested that genetic exchanges between the eastern Orinoco and Northwest Pacific populations has taken place across the Andes, most probably via migration of infected people.
Collapse
|
234
|
Westenberger SJ, McClean CM, Chattopadhyay R, Dharia NV, Carlton JM, Barnwell JW, Collins WE, Hoffman SL, Zhou Y, Vinetz JM, Winzeler EA. A systems-based analysis of Plasmodium vivax lifecycle transcription from human to mosquito. PLoS Negl Trop Dis 2010; 4:e653. [PMID: 20386602 PMCID: PMC2850316 DOI: 10.1371/journal.pntd.0000653] [Citation(s) in RCA: 90] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2009] [Accepted: 03/01/2010] [Indexed: 11/18/2022] Open
Abstract
Background Up to 40% of the world's population is at risk for Plasmodium vivax malaria, a disease that imposes a major public health and economic burden on endemic countries. Because P. vivax produces latent liver forms, eradication of P. vivax malaria is more challenging than it is for P. falciparum. Genetic analysis of P. vivax is exceptionally difficult due to limitations of in vitro culture. To overcome the barriers to traditional molecular biology in P. vivax, we examined parasite transcriptional changes in samples from infected patients and mosquitoes in order to characterize gene function, define regulatory sequences and reveal new potential vaccine candidate genes. Principal Findings We observed dramatic changes in transcript levels for various genes at different lifecycle stages, indicating that development is partially regulated through modulation of mRNA levels. Our data show that genes involved in common biological processes or molecular machinery are co-expressed. We identified DNA sequence motifs upstream of co-expressed genes that are conserved across Plasmodium species that are likely binding sites of proteins that regulate stage-specific transcription. Despite their capacity to form hypnozoites we found that P. vivax sporozoites show stage-specific expression of the same genes needed for hepatocyte invasion and liver stage development in other Plasmodium species. We show that many of the predicted exported proteins and members of multigene families show highly coordinated transcription as well. Conclusions We conclude that high-quality gene expression data can be readily obtained directly from patient samples and that many of the same uncharacterized genes that are upregulated in different P. vivax lifecycle stages are also upregulated in similar stages in other Plasmodium species. We also provide numerous examples of how systems biology is a powerful method for determining the likely function of genes in pathogens that are neglected due to experimental intractability. Most of the 250 million malaria cases outside of Africa are caused by the parasite Plasmodium vivax. Although drugs can be used to treat P. vivax malaria, drug resistance is spreading and there is no available vaccine. Because this species cannot be readily grown in the laboratory there are added challenges to understanding the function of the many hypothetical genes in the genome. We isolated transcriptional messages from parasites growing in human blood and in mosquitoes, labeled the messages and measured how their levels for different parasite growth conditions. The data for 5,419 parasite genes shows extensive changes as the parasite moves between human and mosquito and reveals highly expressed genes whose proteins might represent new therapeutic targets for experimental vaccines. We discover sets of genes that are likely to play a role in the earliest stages of hepatocyte infection. We find intriguing differences in the expression patterns of different blood stage parasites that may be related to host-response status.
Collapse
Affiliation(s)
- Scott J. Westenberger
- Department of Cell Biology ICND 202, The Scripps Research Institute, La Jolla, California, United States of America
| | - Colleen M. McClean
- Division of Infectious Diseases, Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | | | - Neekesh V. Dharia
- Department of Cell Biology ICND 202, The Scripps Research Institute, La Jolla, California, United States of America
| | - Jane M. Carlton
- Department of Medical Parasitology, New York University Langone Medical Center, New York, New York, United States of America
| | - John W. Barnwell
- Centers for Disease Control and Prevention, Division of Parasitic Diseases, Atlanta, Georgia, United States of America
| | - William E. Collins
- Centers for Disease Control and Prevention, Division of Parasitic Diseases, Atlanta, Georgia, United States of America
| | | | - Yingyao Zhou
- Genomics Institute of the Novartis Research Foundation, San Diego, California, United States of America
| | - Joseph M. Vinetz
- Division of Infectious Diseases, Department of Medicine, University of California San Diego School of Medicine, La Jolla, California, United States of America
| | - Elizabeth A. Winzeler
- Department of Cell Biology ICND 202, The Scripps Research Institute, La Jolla, California, United States of America
- * E-mail:
| |
Collapse
|
235
|
Abstract
Malaria, particularly that one caused by Plasmodium falciparum, remains a serious health problem in Africa, South America, and many parts of Asia where it afflicts about 500 million people and is responsible for the death of more than one million children each year. The main reasons for the persistence of malaria are the emergence of resistance to common antimalarial drugs, inadequate control of mosquito vectors, and the lack of effective vaccines. Therefore, the identification and characterization of new targets for antimalarial chemotherapy are of urgent priority. This review is focused on inhibitors of falcipain-2, a cysteine protease from P. falciparum, which represents one of the most promising targets for antimalarial drug design. Falcipain-2 is a key enzyme in the life cycle of P. falciparum since it degrades hemoglobin, at the early trophozoite stage, and cleaves ankyrin and protein 4.1, the cytoskeletal elements vital to the stability of red cell membrane, at the schizont stage. The main classes of falcipain-2 inhibitors are peptides or peptidomimetics bearing the most popular pharmacophores of cysteine protease inhibitors, such as vinyl sulfones, halomethyl ketones, and aldehydes. Furthermore, many other chemotypes have been identified as inhibitors of falcipain-2, such as isoquinolines, thiosemicarbazones, and chalcones. These inhibitors represent all classes, which, to the best of our knowledge, have been disclosed in journal articles to date.
Collapse
Affiliation(s)
- Roberta Ettari
- Dipartimento Farmaco-Chimico, University of Messina, Messina, Italy.
| | | | | | | | | |
Collapse
|
236
|
Basak SC, Mills D. Quantitative structure-activity relationships for cycloguanil analogs as PfDHFR inhibitors using mathematical molecular descriptors. SAR AND QSAR IN ENVIRONMENTAL RESEARCH 2010; 21:215-229. [PMID: 20544548 DOI: 10.1080/10629361003770951] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/29/2023]
Abstract
Computed molecular descriptors were used to develop quantitative structure-activity relationships (QSARs) for binding affinities (K(i)) for a set of 58 cycloguanil (2,4-diamino-1,6-dihydro-1,3,5-triazine) analogues for dihydrofolate reductase (DHFR) enzyme extracted from wild and A16V+S108T mutant type (a double mutation) malaria parasite Plasmodium falciparum (Pf). High-quality models were obtained in both cases. The results of statistical analyses show that ridge regression (RR) outperformed the two other modelling methods, principal component regression (PCR) and partial least squares (PLS). For both enzymes, recognition of the inhibitors was based on four broad categories of descriptors encoding information on: (1) the electronic character of the various atoms in the molecule, (2) the size and shape of the structure, (3) the degree of branching in the molecular skeleton, and (4) two to five atom molecular fragments with aliphatic carbon at one end and aliphatic or aromatic carbon or nitrogen at the other end. The subsets of influential descriptors underlying the QSARs for the wild versus the mutant DHFR are quite non-overlapping. This indicates that the two enzymes recognize the inhibitor molecules on the basis of mutually distinct structural attributes. Such differential QSARs can be useful in the design of novel drugs active against malaria parasites which are growing in resistant to existing chemotherapeutic agents.
Collapse
Affiliation(s)
- S C Basak
- Center for Water and the Environment, Natural Resources Research Institute, University of Minnesota Duluth, Duluth, USA.
| | | |
Collapse
|
237
|
Preclinical evaluation of the antifolate QN254, 5-chloro- N'6'-(2,5-dimethoxy-benzyl)-quinazoline-2,4,6-triamine, as an antimalarial drug candidate. Antimicrob Agents Chemother 2010; 54:2603-10. [PMID: 20350951 DOI: 10.1128/aac.01526-09] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022] Open
Abstract
Drug resistance against dihydrofolate reductase (DHFR) inhibitors-such as pyrimethamine (PM)-has now spread to almost all regions where malaria is endemic, rendering antifolate-based malaria treatments highly ineffective. We have previously shown that the di-amino quinazoline QN254 [5-chloro-N'6'-(2,5-dimethoxy-benzyl)-quinazoline-2,4,6-triamine] is active against the highly PM-resistant Plasmodium falciparum V1S strain, suggesting that QN254 could be used to treat malaria in regions with a high prevalence of antifolate resistance. Here, we further demonstrate that QN254 is highly active against Plasmodium falciparum clinical isolates, displaying various levels of antifolate drug resistance, and we provide biochemical and structural evidence that QN254 binds and inhibits the function of both the wild-type and the quadruple-mutant (V1S) forms of the DHFR enzyme. In addition, we have assessed QN254 oral bioavailability, efficacy, and safety in vivo. The compound displays favorable pharmacokinetic properties after oral administration in rodents. The drug was remarkably efficacious against Plasmodium berghei and could fully cure infected mice with three daily oral doses of 30 mg/kg. In the course of these efficacy studies, we have uncovered some dose limiting toxicity at higher doses that was confirmed in rats. Thus, despite its relative in vitro selectivity toward the Plasmodium DHFR enzyme, QN254 does not show the adequate therapeutic index to justify its further development as a single agent.
Collapse
|
238
|
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.
Collapse
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:
| |
Collapse
|
239
|
Origins of the recent emergence of Plasmodium falciparum pyrimethamine resistance alleles in Madagascar. Antimicrob Agents Chemother 2010; 54:2323-9. [PMID: 20308388 DOI: 10.1128/aac.01511-09] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The combination of sulfadoxine-pyrimethamine is recommended for use as intermittent preventive treatment of malaria during pregnancy and is deployed in Africa. The emergence and the spread of resistant parasites are major threats to such an intervention. We have characterized the Plasmodium falciparum dhfr (pfdhfr) haplotypes and flanking microsatellites in 322 P. falciparum isolates collected from the Comoros Islands and Madagascar. One hundred fifty-six (48.4%) carried the wild-type pfdhfr allele, 19 (5.9%) carried the S108N single-mutation allele, 30 (9.3%) carried the I164L single-mutation allele, 114 (35.4%) carried the N51I/C59R/S108N triple-mutation allele, and 3 (1.0%) carried the N51I/C59R/S108N/I164L quadruple-mutation allele. Microsatellite analysis showed the introduction from the Comoros Islands of the ancestral pfdhfr triple mutant allele of Asian origin and its spread in Madagascar. Evidence for the emergence on multiple occasions of the I164L single-mutation pfdhfr allele in Madagascar was also obtained. Thus, the conditions required to generate mutants with quadruple mutations are met in Madagascar, representing a serious threat to current drug policy.
Collapse
|
240
|
Selection of known Plasmodium falciparum resistance-mediating polymorphisms by artemether-lumefantrine and amodiaquine-sulfadoxine-pyrimethamine but not dihydroartemisinin-piperaquine in Burkina Faso. Antimicrob Agents Chemother 2010; 54:1949-54. [PMID: 20231394 DOI: 10.1128/aac.01413-09] [Citation(s) in RCA: 84] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Artemether-lumefantrine (AL), dihydroartemisinin-piperaquine (DP), and amodiaquine-sulfadoxine-pyrimethamine (AQ-SP) offer excellent antimalarial efficacy but may select for parasite polymorphisms that decrease drug sensitivity. We evaluated the selection of known polymorphisms in genes encoding putative transporters (pfcrt and pfmdr1) and SP targets (pfdhfr and pfdhps) in parasites that caused new infections within 42 days of therapy for uncomplicated falciparum malaria in Burkina Faso. In 559 children in 2006, 42-day genotype-uncorrected failures were seen in 31.2% with AL, 11.8% with AQ-SP, and 7.6% with DP. After prior AL therapy, selection of wild-type sequences was seen for K76T in pfcrt (72.7% mixed or mutant results pretreatment versus 52.1% in new infections; P = 0.008) and N86Y (36.0% versus 18.7%; P = 0.025) and Y184F (66.7% versus 45.8%; P = 0.009) in pfmdr1. After prior AQ-SP therapy, selection of mutant sequences was seen for N51I (30.8% versus 61.5%; P = 0.05), C59R (28.2% versus 76.9%; P = 0.002), and S108N (30.8% versus 76.9%; P = 0.005) in pfdhfr. After prior DP therapy, selection was not seen for K76T (72.7% versus 77.8%; P = 0.96) in pfcrt or N86Y (36.0% versus 33.3%; P = 0.84), Y184F (66.7% versus 77.8%; P = 0.39), or D1246Y (9.3% versus 0%; P = 0.42) in pfmdr1. In 378 additional treatments with DP in 2007, 42-day uncorrected failure was seen in 10.9%. After prior DP, selection was again not seen for K76T (66.7% mixed or mutant results versus 59.5%; P = 0.43) in pfcrt or N86Y (38.7% versus 40.5%; P = 0.85), Y184F (67.6% versus 73.0%; P = 0.54), or D1246Y (3.6% versus 8.1%; P = 0.50) in pfmdr1. Despite its chemical similarity, piperaquine did not select for the same polymorphisms as chloroquine or AQ, suggesting different mechanisms of resistance.
Collapse
|
241
|
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.
Collapse
Affiliation(s)
- Sedigheh Zakeri
- Malaria and Vector Research Group, Biotechnology Research Center, Institut Pasteur of Iran, Pasteur Avenue, PO BOX 1316943551, Tehran, Iran.
| | | | | | | | | | | | | | | |
Collapse
|
242
|
Choowongkomon K, Theppabutr S, Songtawee N, Day NPJ, White NJ, Woodrow CJ, Imwong M. Computational analysis of binding between malarial dihydrofolate reductases and anti-folates. Malar J 2010; 9:65. [PMID: 20193090 PMCID: PMC2838911 DOI: 10.1186/1475-2875-9-65] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2009] [Accepted: 03/02/2010] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Plasmodium falciparum readily develops resistance to the anti-folates pyrimethamine and proguanil via a characteristic set of mutations in the dihydrofolate reductase (PfDHFR) gene that leads to reduced competitive drug binding at the enzyme's active site. Analogous mutations can be found in the DHFR gene in isolates of Plasmodium vivax (PvDHFR) although anti-folates have not been widely used for the treatment of this infection. Here the interactions between DHFR inhibitors and modelled structures of the DHFR enzymes of Plasmodium malariae (PmDHFR) and Plasmodium ovale (PoDHFR) are described, along with an investigation of the effect of recently reported mutations within PmDHFR. METHODS DHFR models for PmDHFR and PoDHFR were constructed using the solved PfDHFR-TS and PvDHFR structures respectively as templates. The modelled structures were docked with three DHFR inhibitors as ligands and more detailed interactions were explored via simulation of molecular dynamics. RESULTS Highly accurate models were obtained containing sets of residues that mediate ligand binding which are highly comparable to those mediating binding in known crystal structures. Within this set, there were differences in the relative contribution of individual residues to inhibitor binding. Modelling of PmDHFR mutant sequences revealed that PmDHFR I170M was associated with a significant reduction in binding energy to all DHFR inhibitors studied, while the other predicted resistance mutations had lesser or no effects on ligand binding. CONCLUSIONS Binding of DHFR inhibitors to the active sites of all four Plasmodium enzymes is broadly similar, being determined by an analogous set of seven residues. PmDHFR mutations found in field isolates influenced inhibitor interactions to a varying extent. In the case of the isolated I170M mutation, the loss of interaction with pyrimethamine suggests that DHFR-inhibitor interactions in P. malariae are different to those seen for DHFRs from P. falciparum and P. vivax.
Collapse
Affiliation(s)
- Kiattawee Choowongkomon
- Department of Clinical Tropical Medicine, Faculty of Tropical Medicine, Mahidol University, Phayathai, Bangkok 10400, Thailand
| | | | | | | | | | | | | |
Collapse
|
243
|
Parikh S, Rosenthal PJ. Intermittent preventive therapy for malaria in pregnancy: is sulfadoxine-pyrimethamine the right drug? Clin Pharmacol Ther 2010; 87:160-2. [PMID: 20107451 DOI: 10.1038/clpt.2009.284] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
Abstract
Pregnant women are at particularly high risk for morbidity and mortality from malaria, and pregnancy can markedly affect drug pharmacokinetics, yet the pharmacokinetics of antimalarial drugs in pregnancy has been little studied. An important malaria-control measure in Africa is intermittent preventive therapy (IPT) with sulfadoxine-pyrimethamine (SP) during pregnancy. We discuss IPT with SP in light of several concerns and highlight recent findings from a pharmacokinetic study of SP in this population.
Collapse
Affiliation(s)
- S Parikh
- Department of Medicine, San Francisco General Hospital, University of California, San Francisco, San Francisco, California, USA.
| | | |
Collapse
|
244
|
Marfurt J, Smith TA, Hastings IM, Müller I, Sie A, Oa O, Baisor M, Reeder JC, Beck HP, Genton B. Plasmodium falciparum resistance to anti-malarial drugs in Papua New Guinea: evaluation of a community-based approach for the molecular monitoring of resistance. Malar J 2010; 9:8. [PMID: 20053293 PMCID: PMC2820042 DOI: 10.1186/1475-2875-9-8] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/06/2009] [Accepted: 01/07/2010] [Indexed: 11/23/2022] Open
Abstract
Background Molecular monitoring of parasite resistance has become an important complementary tool in establishing rational anti-malarial drug policies. Community surveys provide a representative sample of the parasite population and can be carried out more rapidly than accrual of samples from clinical cases, but it is not known whether the frequencies of genetic resistance markers in clinical cases differ from those in the overall population, or whether such community surveys can provide good predictions of treatment failure rates. Methods Between 2003 and 2005, in vivo drug efficacy of amodiaquine or chloroquine plus sulphadoxine-pyrimethamine was determined at three sites in Papua New Guinea. The genetic drug resistance profile (i.e., 33 single nucleotide polymorphisms in Plasmodium falciparum crt, mdr1, dhfr, dhps, and ATPase6) was concurrently assessed in 639 community samples collected in the catchment areas of the respective health facilities by using a DNA microarray-based method. Mutant allele and haplotype frequencies were determined and their relationship with treatment failure rates at each site in each year was investigated. Results PCR-corrected in vivo treatment failure rates were between 12% and 28% and varied by site and year with variable longitudinal trends. In the community samples, the frequencies of mutations in pfcrt and pfmdr1 were high and did not show significant changes over time. Mutant allele frequencies in pfdhfr were moderate and those in pfdhps were low. No mutations were detected in pfATPase6. There was much more variation between sites than temporal, within-site, variation in allele and haplotype frequencies. This variation did not correlate well with treatment failure rates. Allele and haplotype frequencies were very similar in clinical and community samples from the same site. Conclusions The relationship between parasite genetics and in vivo treatment failure rate is not straightforward. The frequencies of genetic anti-malarial resistance markers appear to be very similar in community and clinical samples, but cannot be used to make precise predictions of clinical outcome. Thus, indicators based on molecular data have to be considered with caution and interpreted in the local context, especially with regard to prior drug usage and level of pre-existing immunity. Testing community samples for molecular drug resistance markers is a complementary tool that should help decision-making for the best treatment options and appropriate potential alternatives.
Collapse
Affiliation(s)
- Jutta Marfurt
- Swiss Tropical Institute, Department of Medical Parasitology and Infection Biology, and Department of Public Health and Epidemiology, Socinstrasse 57, PO Box, CH-4002 Basel, Switzerland
| | | | | | | | | | | | | | | | | | | |
Collapse
|
245
|
Adane L, Patel DS, Bharatam PV. Shape- and Chemical Feature-Based 3D-Pharmacophore Model Generation and Virtual Screening: Identification of Potential Leads forP. falciparumDHFR Enzyme Inhibition. Chem Biol Drug Des 2010; 75:115-26. [DOI: 10.1111/j.1747-0285.2009.00908.x] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
|
246
|
Nzila A, Mwai L. In vitro selection of Plasmodium falciparum drug-resistant parasite lines. J Antimicrob Chemother 2009; 65:390-8. [PMID: 20022938 PMCID: PMC2818104 DOI: 10.1093/jac/dkp449] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
Abstract
The in vitro selection of antimicrobial resistance in important pathogens can provide critical information on the genetic basis of drug resistance, and such information can be used to predict, anticipate and even contain the spread of resistance in clinical practice. For instance, the discovery of the role of pfmdr1 in mefloquine resistance in malaria parasites resulted from in vitro studies. However, the in vitro selection of resistance is difficult, challenging and time consuming. In this review, we discuss the key parameters that impact on the efficiency of the in vitro selection of resistance, and propose strategies to improve and streamline this process.
Collapse
Affiliation(s)
- Alexis Nzila
- Kenya Medical Research Institute (KEMRI)/Wellcome Trust Collaborative Research Program, PO Box 230, 80108 Kilifi, Kenya.
| | | |
Collapse
|
247
|
Müller IB, Hyde JE, Wrenger C. Vitamin B metabolism in Plasmodium falciparum as a source of drug targets. Trends Parasitol 2009; 26:35-43. [PMID: 19939733 DOI: 10.1016/j.pt.2009.10.006] [Citation(s) in RCA: 44] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/27/2009] [Revised: 09/25/2009] [Accepted: 10/22/2009] [Indexed: 10/20/2022]
Abstract
The malaria parasite Plasmodium falciparum depends primarily on nutrient sources from its human host. Most compounds, such as glucose, purines, amino acids, as well as cofactors and vitamins, are abundantly available in the host cell, and can be readily salvaged by the parasite. However, in some cases the parasite can also synthesize cofactors de novo in reactions that appear to be essential. Importantly, the three biosynthetic pathways that produce vitamins B(1), B(6) and B(9) are absent from the host, but are well established in P. falciparum. This review summarizes and updates the current knowledge of vitamin B de novo synthesis and salvage in P. falciparum and focuses on their potential as targets for drug intervention.
Collapse
Affiliation(s)
- Ingrid B Müller
- Department of Biochemistry, Bernhard Nocht Institute for Tropical Medicine, Hamburg, Germany.
| | | | | |
Collapse
|
248
|
Eastman RT, Fidock DA. Artemisinin-based combination therapies: a vital tool in efforts to eliminate malaria. Nat Rev Microbiol 2009; 7:864-74. [PMID: 19881520 DOI: 10.1038/nrmicro2239] [Citation(s) in RCA: 369] [Impact Index Per Article: 24.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Plasmodium falciparum resistance to chloroquine and sulphadoxine-pyrimethamine has led to the recent adoption of artemisinin-based combination therapies (ACTs) as the first line of treatment against malaria. ACTs comprise semisynthetic artemisinin derivatives paired with distinct chemical classes of longer acting drugs. These artemisinins are exceptionally potent against the pathogenic asexual blood stages of Plasmodium parasites and also act on the transmissible sexual stages. These combinations increase the rates of clinical and parasitological cures and decrease the selection pressure for the emergence of antimalarial resistance. This Review article discusses our current knowledge about the mode of action of ACTs, their pharmacological properties and the proposed mechanisms of drug resistance.
Collapse
Affiliation(s)
- Richard T Eastman
- Department of Microbiology & Immunology, Columbia University College of Physicians and Surgeons, Hammer Health Sciences Center, Room 1502, 701 West 168th Street, New York 10032, New York, USA.
| | | |
Collapse
|
249
|
Adane L, Bharatam PV. 3D-QSAR analysis of cycloguanil derivatives as inhibitors of A16V+S108T mutant Plasmodium falciparum dihydrofolate reductase enzyme. J Mol Graph Model 2009; 28:357-67. [DOI: 10.1016/j.jmgm.2009.09.001] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2009] [Revised: 08/27/2009] [Accepted: 09/01/2009] [Indexed: 12/17/2022]
|
250
|
Escalante AA, Smith DL, Kim Y. The dynamics of mutations associated with anti-malarial drug resistance in Plasmodium falciparum. Trends Parasitol 2009; 25:557-63. [PMID: 19864183 DOI: 10.1016/j.pt.2009.09.008] [Citation(s) in RCA: 32] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2009] [Revised: 07/22/2009] [Accepted: 09/10/2009] [Indexed: 10/20/2022]
Abstract
The evolution of resistance in Plasmodium falciparum against safe and affordable drugs such as chloroquine (CQ) and sulfadoxine-pyrimethamine (SP) is a major global health threat. Investigating the dynamics of resistance against these antimalarial drugs will lead to approaches for addressing the problem of resistance in malarial parasites that are solidly based in evolutionary genetics and population biology. In this article, we discuss current developments in population biology modeling and evolutionary genetics. Despite great advancements achieved in the past decade, understanding the complex dynamics of mutations conferring drug resistance in P. falciparum requires approaches that consider the parasite population structure among other demographic processes.
Collapse
Affiliation(s)
- Ananias A Escalante
- School of Life Sciences, Arizona State University, PO Box 874501, Tempe, AZ 85287-4501, USA.
| | | | | |
Collapse
|