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Role of pfmdr1 amplification and expression in induction of resistance to artemisinin derivatives in Plasmodium falciparum.

ABSTRACT: Artemisinin and its derivatives are the most rapidly acting and efficacious antimalarial drugs currently available. Although resistance to these drugs has not been documented, there is growing concern about the potential for resistance to develop. In this paper we report the selection of parasite resistance to artelinic acid (AL) and artemisinin (QHS) in vitro and the molecular changes that occurred during the selection. Exposure of three Plasmodium falciparum lines (W2, D6, and TM91C235) to AL resulted in decreases in parasite susceptibilities to AL and QHS, as well as to mefloquine, quinine, halofantrine, and lumefantrine. The changes in parasite susceptibility were accompanied by increases in the copy number, mRNA expression, and protein expression of the pfmdr1 gene in the resistant progenies of W2 and TM91C235 parasites but not in those of D6 parasites. No changes were detected in the coding sequences of the pfmdr1, pfcrt, pfatp6, pftctp, and pfubcth genes or in the expression levels of pfatp6 and pftctp. Our data demonstrate that P. falciparum lines have the capacity to develop resistance to artemisinin derivatives in vitro and that this resistance is achieved by multiple mechanisms, to include amplification and increased expression of pfmdr1, a mechanism that also confers resistance to mefloquine. This observation is of practical importance, because artemisinin drugs are often used in combination with mefloquine for the treatment of malaria.

SUBMITTER: Chavchich M

PROVIDER: S-EPMC2876417 | biostudies-literature | 2010 Jun

REPOSITORIES: biostudies-literature

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Role of pfmdr1 amplification and expression in induction of resistance to artemisinin derivatives in Plasmodium falciparum.

Chavchich Marina M Gerena Lucia L Peters Jennifer J Chen Nanhua N Cheng Qin Q Kyle Dennis E DE

Antimicrobial agents and chemotherapy 20100329 6

Artemisinin and its derivatives are the most rapidly acting and efficacious antimalarial drugs currently available. Although resistance to these drugs has not been documented, there is growing concern about the potential for resistance to develop. In this paper we report the selection of parasite resistance to artelinic acid (AL) and artemisinin (QHS) in vitro and the molecular changes that occurred during the selection. Exposure of three Plasmodium falciparum lines (W2, D6, and TM91C235) to AL ...[more]

PMID: 20350946

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Project description:BackgroundAnti-malarial drugs are the major focus in the prevention and treatment of malaria. Artemisinin-based combination therapy (ACT) is the WHO recommended first-line treatment for Plasmodium falciparum malaria across the endemic world. Also ACT is increasingly relied upon in treating Plasmodium vivax malaria where chloroquine is failing. The emergence of artemisinin drug-resistant parasites is a serious threat faced by global malaria control programmes. Therefore, the success of treatment and intervention strategies is highly pegged on understanding the genetic basis of resistance.MethodsHere, resistance in P. falciparum was generated in vitro for artemisinin to produce levels above clinically relevant concentrations in vivo, and the molecular haplotypes investigated. Genomic DNA was extracted using the QIAamp mini DNA kit. DNA sequences of Pfk13, Pfcrt and Pfmdr1 genes were amplified by PCR and the amplicons were successfully sequenced. Single nucleotide polymorphisms were traced by standard bidirectional sequencing and reading the transcripts against wild-type sequences in Codon code Aligner Version 5.1 and NCBI blast.ResultsExposure of parasite strains D6 and W2 to artemisinin resulted in a decrease in parasite susceptibility to artemisinin (W2 and D6) and lumefantrine (D6 only). The parasites exhibited elevated IC50s to multiple artemisinins, with >twofold resistance to artemisinin; however, the resistance index obtained with standard methods was noticeably less than expected for parasite lines recovered from 50 µg/ml 48 h drug pressure. The change in parasite susceptibility was associated with Pfmdr-185K mutation, a mutation never reported before. The Pfcrt-CVMNK genotype (Pfcrt codons 72-76) was retained and notably, the study did not detect any polymorphisms reported to reduce P. falciparum susceptibility in vivo in the coding sequences of the Pfk13 gene.DiscussionThis data demonstrate that P. falciparum has the capacity to develop resistance to artemisinin derivatives in vitro and that this phenotype is achieved by mutations in Pfmdr1, the genetic changes that are also underpinning lumefantrine resistance. This finding is of practical importance, because artemisinin drugs in Kenya are used in combination with lumefantrine for the treatment of malaria.ConclusionArtemisinin resistance phenotype as has been shown in this work, is a decrease in parasites susceptibility to artemisinin derivatives together with the parasite's ability to recover from drug-induced dormancy after exposure to drug dosage above the in vivo clinical concentrations. The study surmises that Pfmdr1 may play a role in the anti-malarial activity of artemisinin.

Project description:Artemisinin-based combination therapies are the recommended first-line treatments of falciparum malaria in all countries with endemic disease. There are recent concerns that the efficacy of such therapies has declined on the Thai-Cambodian border, historically a site of emerging antimalarial-drug resistance.In two open-label, randomized trials, we compared the efficacies of two treatments for uncomplicated falciparum malaria in Pailin, western Cambodia, and Wang Pha, northwestern Thailand: oral artesunate given at a dose of 2 mg per kilogram of body weight per day, for 7 days, and artesunate given at a dose of 4 mg per kilogram per day, for 3 days, followed by mefloquine at two doses totaling 25 mg per kilogram. We assessed in vitro and in vivo Plasmodium falciparum susceptibility, artesunate pharmacokinetics, and molecular markers of resistance.We studied 40 patients in each of the two locations. The overall median parasite clearance times were 84 hours (interquartile range, 60 to 96) in Pailin and 48 hours (interquartile range, 36 to 66) in Wang Pha (P<0.001). Recrudescence confirmed by means of polymerase-chain-reaction assay occurred in 6 of 20 patients (30%) receiving artesunate monotherapy and 1 of 20 (5%) receiving artesunate-mefloquine therapy in Pailin, as compared with 2 of 20 (10%) and 1 of 20 (5%), respectively, in Wang Pha (P=0.31). These markedly different parasitologic responses were not explained by differences in age, artesunate or dihydroartemisinin pharmacokinetics, results of isotopic in vitro sensitivity tests, or putative molecular correlates of P. falciparum drug resistance (mutations or amplifications of the gene encoding a multidrug resistance protein [PfMDR1] or mutations in the gene encoding sarco-endoplasmic reticulum calcium ATPase6 [PfSERCA]). Adverse events were mild and did not differ significantly between the two treatment groups.P. falciparum has reduced in vivo susceptibility to artesunate in western Cambodia as compared with northwestern Thailand. Resistance is characterized by slow parasite clearance in vivo without corresponding reductions on conventional in vitro susceptibility testing. Containment measures are urgently needed. (ClinicalTrials.gov number, NCT00493363, and Current Controlled Trials number, ISRCTN64835265.)

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Role of pfmdr1 amplification and expression in induction of resistance to artemisinin derivatives in Plasmodium falciparum.

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Role of pfmdr1 amplification and expression in induction of resistance to artemisinin derivatives in Plasmodium falciparum.

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