title: In vitro-reduced susceptibility to artemether in P. falciparum and its association with polymorphisms on transporter genes.
abstract: Plasmodium falciparum with reduced sensitivity to artemisinin derivatives has been observed in endemic areas, but the molecular mechanisms for this reduced sensitivity remain unclear. We evaluated the association between in vitro susceptibility of P. falciparum isolates obtained from southwest Nigeria and polymorphisms in selected putative transporter genes (PFE0775C, PF13_0271, pfmrp1, pfcrt, and pfmdr1). Modified schizont inhibition assay was used to determine the in vitro parasite susceptibility to artemether (ATH). Polymorphisms in selected genes were detected by polymerase chain reaction followed by direct DNA sequencing. The half-maximal inhibitory concentration (IC(50)) geometric mean (GM) for all P. falciparum isolates was 1.78 nM (range, 0.03-10.43 nM). Polymorphisms at codons 241, 86, and 76 of PFE0775C, pfmdr1, and pfcrt genes, respectively, were associated with reduced susceptibility to ATH. A new S263P single-nucleotide polymorphism on the PFE0775C gene was also detected in 27% of the isolates. Patient isolates harboring V241L or S263P polymorphisms on the PFE0775C gene showed increased IC(50) (GM: 3.08 nM and 1.79 nM, respectively). Plasmodium falciparum isolates harboring mutant Y86 pfmdr1 and P263 PFE0775C alleles showed a 2.5-5.5-fold increase in ATH IC(50.) This study shows that polymorphisms on the PFE0775C and pfmdr1 genes are associated with reduced sensitivity to ATH in fresh isolates of P. falciparum from Nigeria.
authors.affiliation: Laboratory of Molecular Infectology and Parasitology,  Clementino Fraga Filho University Hospital,  Federal University of Rio de Janeiro,  Brazil.
authors.forename: Carolina
authors.initials: C
authors.lastname: Bustamante
authors.forename: Onikepe A
authors.initials: OA
authors.lastname: Folarin
authors.forename: Grace O
authors.initials: GO
authors.lastname: Gbotosho
authors.forename: Camila N
authors.initials: CN
authors.lastname: Batista
authors.forename: Elieth A
authors.initials: EA
authors.lastname: Mesquita
authors.forename: Rodrigo M
authors.initials: RM
authors.lastname: Brindeiro
authors.forename: Amilcar
authors.initials: A
authors.lastname: Tanuri
authors.forename: Claudio J
authors.initials: CJ
authors.lastname: Struchiner
authors.forename: Akintunde
authors.initials: A
authors.lastname: Sowunmi
authors.forename: Ayoade
authors.initials: A
authors.lastname: Oduola
authors.forename: Dyann F
authors.initials: DF
authors.lastname: Wirth
authors.forename: Mariano G
authors.initials: MG
authors.lastname: Zalis
authors.forename: Christian T
authors.initials: CT
authors.lastname: Happi
mesh_terms: D000962:Antimalarials / Q000494:pharmacology*; D000077549:Artemether; D037621:Artemisinins / Q000494:pharmacology*; D002352:Carrier Proteins / Q000235:genetics* / Q000378:metabolism; D002648:Child; D016054:DNA, Protozoan / Q000235:genetics / Q000302:isolation & purification; D004351:Drug Resistance / Q000235:genetics*; D005786:Gene Expression Regulation; D006801:Humans; D020128:Inhibitory Concentration 50; D021261:Parasitic Sensitivity Tests / Q000379:methods; D010963:Plasmodium falciparum / Q000187:drug effects*; D016133:Polymerase Chain Reaction / Q000379:methods; D011110:Polymorphism, Genetic; D015800:Protozoan Proteins / Q000235:genetics / Q000378:metabolism
chemical_list: D000962:Antimalarials; D037621:Artemisinins; D002352:Carrier Proteins; D016054:DNA, Protozoan; D015800:Protozoan Proteins; D000077549:Artemether