Plasmodium falciparum Polymorphisms Associated with Ex Vivo Drug Susceptibility and Clinical Effectiveness of Artemisinin-Based Combination Therapies in Benin

Abstract

h Artemisinin-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 of Plasmodium falciparum polymorphisms and ex vivo drug 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, and pfdhps polymorphisms were analyzed pretreatment and in recurrent infections. Drug susceptibility was determined in fresh baseline isolates by Plasmodium lactate dehydrogenase enzyme-linked immunosorbent assay (ELISA). A majority had 50% inhibitory concentration (IC 50 ) 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 IC 50 s were higher. No association was found between susceptibility to the ACT compounds and treatment outcome.

Role of Pfmdr1 in In Vitro Plasmodium falciparum Susceptibility to Chloroquine, Quinine, Monodesethylamodiaquine, Mefloquine, Lumefantrine, and Dihydroartemisinin

“…Nonetheless, we show that the 86Y mutation was significantly associated with increased susceptibility to MQ (P ϭ 0.00002). These results are in accordance with previous studies in Asia (12,42) and in Benin (43) and are strengthened by field studies demonstrating MQ selection of the N86 allele in recurrent infections after treatment with artesunate plus MQ (44).…”

“…These results are in accordance with previous in vitro studies in Asia (45), Kenya (17), and Benin (43). Field studies in east Africa also have shown selection of the 86N allele in recurrent infections after treatment with artemether plus LMF (39,40,46,47), which suggests that 86N is a marker of LMF resistance in vivo.…”

“…A similar association was seen for LMF and MQ in previous studies in Benin (43). Similarly, we showed a decreased susceptibility to LMF and MQ in parasites with N86 plus 184F and N86 plus Y184.…”

“…However, these data are in contrast to previous in vitro works. There was no difference in MDAQ IC 50 between the two haplotypes N86 and 86Y in isolates from Benin (43). In other works, the mutant Pfmdr1 86Y allele showed an increased MDAQ IC 50 in isolates from Nigeria (48).…”

Changing Antimalarial Drug Sensitivities in Uganda

“…Third, we Associations of ex vivo drug sensitivity with transporter polymorphisms. We and others have previously shown that polymorphisms in the putative transporters pfcrt and pfmdr1 are associated with altered ex vivo drug sensitivity (7,12,(34)(35)(36)(37)(38). We tested for associations between pfcrt K76T and pfmdr1 N86Y, Y184F, and D1246Y polymorphisms, and the ex vivo drug sensitivities were determined for samples collected in 2016 (Fig.…”