In vitro activities of quinine and other antimalarials and pfnhe polymorphisms in Plasmodium isolates from Kenya.
Resistance to the amino alcohol quinine has been associated with polymorphisms in pfnhe, a sodium hydrogen exchanger. We investigated the role of this gene in quinine resistance in vitro in isolates from Kenya. We analyzed pfnhe whole-gene polymorphisms, using capillary sequencing, and pfcrt at codon 76 (pfcrt-76) and pfmdr1 at codon 86 (pfmdr1-86), using PCR-enzyme restriction methodology, in 29 isolates from Kilifi, Kenya, for association with the in vitro activities of quinine and 2 amino alcohols, mefloquine and halofantrine. In vitro activity was assessed as the drug concentration that inhibits 50% of parasite growth (IC50). The median IC50s of quinine, halofantrine, and mefloquine were 92, 22, and 18 nM, respectively. The presence of 2 DNNND repeats in microsatellite ms4760 of pfnhe was associated with reduced susceptibility to quinine (60 versus 227 nM for 1 and 2 repeats, respectively; P<0.05), while 3 repeats were associated with restoration of susceptibility. The decrease in susceptibility conferred by the 2 DNNND repeats was more pronounced in parasites harboring the pfmdr1-86 mutation. No association was found between susceptibility to quinine and the pfcrt-76 mutation or between susceptibility to mefloquine or halofantrine and the pfnhe gene and the pfcrt-76 and pfmdr1-86 mutations. Using previously published data on the in vitro activities of chloroquine, lumefantrine, piperaquine, and dihydroartemisinin, we investigated the association of their activities with pfnhe polymorphism. With the exception of a modulation of the activity of lumefantrine by a mutation at position 1437, pfnhe did not modulate their activities. Two DNNND repeats combined with the pfmdr1-86 mutation could be used as an indicator of reduced susceptibility to quinine.
Kenya Medical Research Institute (KEMRI)/Wellcome Trust Collaborative Research Program, P.O. Box 230, 80108 Kilifi, Kenya.
John
J
Okombo
Steven M
SM
Kiara
Josea
J
Rono
Leah
L
Mwai
Lewa
L
Pole
Eric
E
Ohuma
Steffen
S
Borrmann
Lynette Isabella
LI
Ochola
Alexis
A
Nzila
D000595:Amino Acid Sequence; D000818:Animals; D000962:Antimalarials / Q000494:pharmacology*; D004351:Drug Resistance / Q000235:genetics; D006801:Humans; D007630:Kenya; D015767:Mefloquine / Q000494:pharmacology; D026901:Membrane Transport Proteins; D008969:Molecular Sequence Data; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D021261:Parasitic Sensitivity Tests; D010616:Phenanthrenes / Q000494:pharmacology; D010963:Plasmodium falciparum / Q000187:drug effects* / Q000235:genetics / Q000302:isolation & purification; D011110:Polymorphism, Genetic; D015800:Protozoan Proteins / Q000737:chemistry / Q000235:genetics; D011803:Quinine / Q000494:pharmacology*; D017422:Sequence Analysis, DNA; D017923:Sodium-Hydrogen Exchangers / Q000737:chemistry / Q000235:genetics*
D000962:Antimalarials; D015767:Mefloquine; D026901:Membrane Transport Proteins; D027425:ATP-Binding Cassette, Sub-Family C Proteins; D010616:Phenanthrenes; D015800:Protozoan Proteins; D011803:Quinine; D017923:Sodium-Hydrogen Exchangers; C513498:Mdr1 protein, Plasmodium falciparum; C416369:PfCRT protein, Plasmodium falciparum; C023768:halofantrine