In Vitro Activities of Piperaquine, Lumefantrine, and Dihydroartemisinin in Kenyan Plasmodium falciparum Isolates and Polymorphisms in p fcrt and p fmdr1

Abstract

We have analyzed the in vitro chemosensitivity profiles of 115 Kenyan isolates for chloroquine (CQ), piperaquine, lumefantrine (LM), and dihydroartemisinin in association with polymorphisms in pfcrt at codon 76 and pfmdr1 at codon 86, as well as with variations of the copy number of pfmdr1. The median drug concentrations that inhibit 50% of parasite growth (IC 50 s) were 41 nM (interquartile range [IQR], 18 to 73 nM), 50 nM (IQR, 29 to 96 nM), 32 nM (IQR, 17 to 46 nM), and 2 nM (IQR, 1 to 3 nM) for CQ, LM, piperaquine, and dihydroartemisinin, respectively. The activity of CQ correlated inversely with that of LM (r 2 ‫؍‬ ؊0.26; P ‫؍‬ 0.02). Interestingly, parasites for which LM IC 50 s were higher were wild type for pfcrt-76 and pfmdr1-86. All isolates had one pfmdr1 copy. Thus, the decrease in LM activity is associated with the selection of wild-type pfcrt-76 and pfmdr1-86 parasites, a feature that accounts for the inverse relationship between CQ and LM. Therefore, the use of LM-artemether is likely to lead to the selection of more CQ-susceptible parasites.Chemotherapy is still the main approach for the control of malaria, and current strategies for malaria treatment rely on the use of combinations of drugs that include artemisinin compounds. Although this strategy is designed to reduce the chance of resistance emerging, there is considerable concern that this will inevitably occur.For instance, the combination of lumefantrine (LM) and artemether (ATM), known as Coartem, has become the firstline treatment for malaria in many African countries, including Kenya (19). ATM is converted in vivo to dihydroartemisinin (DHA). Emerging reports indicate that the use of LM (in Coartem) selects for parasites that show increased tolerance to Coartem, and these parasites select for a wild-type pfmdr1 genotype or show increased copy numbers of pfmdr1, a gene associated with chloroquine (CQ) and mefloquine (MFQ) resistance (7,13,15,20,36,38). Thus, there is concern that resistance to LM could emerge rapidly. On the other hand, recent reports from Southeast Asia indicate that resistance to artemisinin derivatives is increasing, threatening the concept of artemisinin-based combinations (8).Another combination, piperaquine (PQ) and DHA, known as Artekin, is undergoing clinical evaluation (17,39,42). This drug is efficacious, safe, and affordable and thus is likely to become an alternative to Coartem. PQ is a bisquinoline derivative consisting of two linked CQ molecules. Although reports indicate that PQ retains potency against CQ-resistant parasites (3), there is concern that PQ could become less susceptible against a backdrop of high CQ resistance (17,22).In this paper, we sought to analyze the in vitro activities of the antimalarials LM, DHA, and PQ in relation to polymorphisms in pfcrt at codon 76 (pfcrt-76) and in pfmdr1 at codon 86 (pfmdr1-86) and in relation to pfmdr1 copy number variations in Kenyan isolates. We used CQ as a reference drug. MATERIALS AND METHODSCQ was purchased from Sigma Chemical Co. (Poole, Dorset, United...

Pfmdr1 gene polymorphism of Plasmodium falciparum isolates from asymptomatic individuals of Dienga, southeastern Gabon

“…The YYD haplotype significantly increased in 2014, in contrast to Kenya and Tanzania where a decrease of Lumefantrine susceptibility was reported followed by increase of the prevalence of NFD, NYD, YYY and YYD [44,36]. A rise of YYD in 2014 was observed and is consistent with the work of Morris U et al who reported that YYD is the most prevalent haplotype in asymptomatic malaria infection [45].…”

“…A relative high prevalence of mutant types 184F and 1246Y in samples from 2013 (54.76 and 64.0%, respectively) was [39,36].…”

“…Moreover, in a study performed in Uganda, it has been documented that genotype 86Y was more important in asymptomatic carriers compared to febrile ones [36]. It has been previously documented that Pfmdr1 86Y and 1246Y mutations decrease chloroquine and amodiaquine sensitivity, but they increase lumefantrine, mefloquine and dihydroartemisin sensitivity according to Pickard [13,40,36,41].…”

“…The increase of genotype N86 has been associated with a decreased susceptibility to artemisinins in vitro [36,37].…”

Adaptive evolution of malaria parasites in French Guiana: Reversal of chloroquine resistance by acquisition of a mutation in pfcrt

“…This result reveals a pleiotropic role for this recently emerged pfcrt allele in modulating parasite susceptibility to clinically important antimalarials. This role differs from what is generally observed in Africa with the PfCRT CVIET haplotype or even the PfCRT SVMNT haplotype in Papua New Guinea (29,30). This effect of C350R on QN and MQ, however, was not replicated in field isolates, underscoring a complex genetic basis of susceptibility in the field.…”