In Vivo Selection ofPlasmodium falciparumParasites Carrying the Chloroquine-SusceptiblepfcrtK76 Allele after Treatment with Artemether-Lumefantrine in Africa

Abstract

Background Artemether-lumefantrine (AL) is a major and highly effective artemisinin-based combination therapy that is becoming increasingly important as a new first-line therapy against Plasmodium falciparum malaria. However, recrudescences occurring after AL treatment have been reported. Identification of drug-specific parasite determinants that contribute to treatment failures will provide important tools for the detection and surveillance of AL resistance. Method The findings from a 42-day follow-up efficacy trial in Tanzania that compared AL with sulfadoxine-pyrimethamine (SP) were analyzed to identify candidate markers for lumefantrine tolerance/resistance in the chloroquine resistance transporter gene (pfcrt) and multidrug resistance gene 1 (pfmdr1). The findings were corroborated in vitro with genetically modified isogenic P. falciparum parasite lines. Results Treatment with AL selected for the chloroquine-susceptible pfcrt K76 allele (P < .0001) and, to a lesser extent, the pfmdr1 N86 (P = .048) allele among recurrent infections. These genotypes were not selected during SP treatment. No pfmdr1 gene amplifications were observed. Isogenic pfcrt-modified parasite lines demonstrated a 2-fold increase in susceptibility to lumefantrine, which was directly attributable to the K76T mutation. Conclusions Our findings suggest that the pfcrt K76T mutation is a drug-specific contributor to enhanced P. falciparum susceptibility to lumefantrine in vivo and in vitro, and they highlight the benefit of using AL in areas affected by chloroquine-resistant P. falciparum malaria.

Incomplete reversal of genotypic resistance of Plasmodium falciparum to chloroquine after a decade of change in malaria treatment policy in Uganda

“…29 In our study, the prevalence of wild type Pfmdr-86N genotype was higher than that of Pfcrt-76K following the introduction of ACTs in malaria treatment over a decade ago. This finding is consistent with that of previous studies 30,31 where emergence of wild type 86N genotype preceded that of 76K after implementation of ACT use. Although artemetherlumefantrine is still very effective in malaria treatment in Uganda, 32 analysis of data from different clinical trials showed that high prevalence of wild type Pfmdr-86N parasite genotype is associated with decreased parasite sensitivity to artemisinin-lumefantrine.…”

Prevalence of Single Nucleotide Polymorphisms in the Plasmodium falciparum Multidrug Resistance Gene (Pfmdr-1) in Korogwe District in Tanzania Before and After Introduction of Artemisinin-Based Combination Therapy

“…Studies in Tanzania have shown that Pfmdr-1 N86 or 184F was selected in reinfections after AL treatment 10 ; furthermore, AL selected Pfcrt K76 and to a lesser extent, the Pfmdr-1 N86 in recurrent infections. 26 In another study performed in Muheza district of Tanzania in 2006, it was reported that 86Y, 184Y, and 1246Y occur more frequently after AQ monotherapy, whereas pre-treatment carriage of N86 or 184F was associated with an increased risk of AL treatment failure. 7 A study from Thailand showed haplotype prevalence of the N86-184F haplotype at 40% in 1988-1993, which increased to 95% in 2003.…”

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

“…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. Another primary determinant of susceptibility to these drugs in P. falciparum is the pfmdr1 gene, which in French Guiana harbors the 86N and 184F residues that are associated with increased LUM susceptibility (31,32). Of note, all isolates remained highly susceptible to LUM, a finding that argues for maintaining the artemether + LUM combination as first-line therapy in the region.…”