Plasmodium falciparum Polymorphisms Associated withEx VivoDrug Susceptibility and Clinical Effectiveness of Artemisinin-Based Combination Therapies in Benin

Abstract

ABSTRACTArtemisinin-based combination therapies (ACTs) are the main option to treat malaria, and their efficacy and susceptibility must be closely monitored to avoid resistance. We assessed the association ofPlasmodium falciparumpolymorphisms andex vivodrug susceptibility with clinical effectiveness. Patients enrolled in an effectiveness trial comparing artemether-lumefantrine (n= 96), fixed-dose artesunate-amodiaquine (n= 96), and sulfadoxine-pyrimethamine (n= 48) for the treatment of uncomplicated malaria 2007 in Benin were assessed.pfcrt,pfmdr1,pfmrp1,pfdhfr, andpfdhpspolymorphisms were analyzed pretreatment and in recurrent infections. Drug susceptibility was determined in fresh baseline isolates byPlasmodiumlactate dehydrogenase enzyme-linked immunosorbent assay (ELISA). A majority had 50% inhibitory concentration (IC50) estimates (the concentration required for 50% growth inhibition) lower than those of the 3D7 reference clone for desethylamodiaquine, lumefantrine, mefloquine, and quinine and was considered to be susceptible, while dihydroartemisinin and pyrimethamine IC50s were higher. No association was found between susceptibility to the ACT compounds and treatment outcome. Selection was observed for thepfmdr1N86 allele in artemether-lumefantrine recrudescences (recurring infections) (4/7 [57.1%] versus 36/195 [18.5%]), and of the opposite allele, 86Y, in artesunate-amodiaquine reinfections (new infections) (20/22 [90.9%] versus 137/195 [70.3%]) compared to baseline infections. The importance ofpfmdr1N86 in lumefantrine tolerance was emphasized by its association with elevated lumefantrine IC50s. Genetic linkage between N86 and Y184 was observed, which together with the low frequency of 1246Y may explain regional differences in selection ofpfmdr1loci. Selection of opposite alleles in artemether-lumefantrine and artesunate-amodiaquine recurrent infections supports the strategy of multiple first-line treatment. Surveillance based on clinical,ex vivo, molecular, and pharmacological data is warranted.