title: Natural selection of K13 mutants of Plasmodium falciparum in response to artemisinin combination therapies in Thailand.
abstract: Resistance of Plasmodium falciparum to artemisinin combination therapy (ACT) in Southeast Asia can have a devastating impact on chemotherapy and control measures. In this study, the evolution of artemisinin-resistant P. falciparum in Thailand was assessed by exploring mutations in the K13 locus believed to confer drug resistance phenotype. P. falciparum-infected blood samples were obtained from patients in eight provinces of Thailand over two decades (1991-2014; n = 904). Analysis of the K13 gene was performed by either sequencing the complete coding region (n = 259) or mutation-specific PCR-restriction fragment length polymorphism method (n = 645). K13 mutations related to artesunate resistance were detected in isolates from Trat province bordering Cambodia in 1991, about 4 years preceding widespread deployment of ACT in Thailand and increased in frequency over time. Nonsynonymous nucleotide diversity exceeded synonymous nucleotide diversity in the propeller region of the K13 gene, supporting the hypothesis that this diversity was driven by natural selection. No single mutant appeared to be favoured in every population, and propeller-region mutants were rarely observed in linkage with each other in the same haplotype. On the other hand, there was a highly significant association between the occurrence of a propeller mutant and the insertion of two or three asparagines after residue 139 of K13. Whether this insertion plays a compensatory role for deleterious effects of propeller mutants on the function of the K13 protein requires further investigation. However, modification of duration of ACT from 2-day to 3-day regimens in 2008 throughout the country does not halt the increase in frequency of mutants conferring artemisinin resistance phenotype.
authors.affiliation: Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand. Electronic address: p.chaturong@gmail.com.
authors.forename: C
authors.initials: C
authors.lastname: Putaporntip
authors.affiliation: Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: N
authors.initials: N
authors.lastname: Kuamsab
authors.affiliation: Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: R
authors.initials: R
authors.lastname: Kosuwin
authors.affiliation: Umphang Hospital, Tak Province, Thailand.
authors.forename: W
authors.initials: W
authors.lastname: Tantiwattanasub
authors.affiliation: Department of Medicine, Bundarik Hospital, Ubon Ratchathani Province, Thailand.
authors.forename: P
authors.initials: P
authors.lastname: Vejakama
authors.affiliation: Department of Biochemistry, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: T
authors.initials: T
authors.lastname: Sueblinvong
authors.affiliation: Department of Biology, Faculty of Science, Naresuan University, Phitsanulok Province, Thailand.
authors.forename: S
authors.initials: S
authors.lastname: Seethamchai
authors.affiliation: Molecular Biology of Malaria and Opportunistic Parasites Research Unit, Department of Parasitology, Faculty of Medicine, Chulalongkorn University, Bangkok, Thailand.
authors.forename: S
authors.initials: S
authors.lastname: Jongwutiwes
authors.affiliation: Department of Biological Sciences, University of South Carolina, Columbia, SC, USA.
authors.forename: A L
authors.initials: AL
authors.lastname: Hughes
mesh_terms: D019943:Amino Acid Substitution; D000962:Antimalarials / Q000494:pharmacology / Q000627:therapeutic use*; D037621:Artemisinins / Q000494:pharmacology / Q000627:therapeutic use*; D003062:Codon; D004351:Drug Resistance; D004359:Drug Therapy, Combination; D017125:Genes, Protozoan; D006801:Humans; D016778:Malaria, Falciparum / Q000188:drug therapy* / Q000453:epidemiology / Q000469:parasitology*; D009154:Mutation; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics*; D011110:Polymorphism, Genetic; D012641:Selection, Genetic; D017422:Sequence Analysis, DNA; D013785:Thailand / Q000453:epidemiology
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D003062:Codon; C031327:artemisinin
keywords: Artemisinin resistance; K13 propeller; Plasmodium falciparum; Thailand; malaria; natural selection