Comparative impacts over 5 years of artemisinin-based combination therapies on Plasmodium falciparum polymorphisms that modulate drug sensitivity in Ugandan children

Abstract

Background: Artemisinin-based combination therapies, including artemether-lumefantrine (AL) and dihydroartemisinin-piperaquine (DP), are recommended to treat uncomplicated falciparum malaria. Sensitivities to components of AL and DP are impacted by polymorphisms in pfmdr1 and pfcrt. We monitored changes in prevalences of polymorphisms in Tororo, Uganda, from 2008 to 2012.

Methods: Polymorphic loci in pfmdr1 and pfcrt were characterized in samples from 312 children randomized to AL or DP for each episode of uncomplicated malaria (50 samples per arm for each 3-month interval) utilizing a fluorescent microsphere assay. Treatment outcomes and impacts of prior therapies were also characterized.

Results: Prevalence increased significantly over time for pfmdr1 N86 (AL: odds ratio [OR], 2.08 [95% confidence interval {CI}, 1.83-2.38]; DP: 1.41 [95% CI, 1.25-1.57]), pfmdr1 D1246 (AL: 1.46 [95% CI, 1.29-1.64]; DP: 1.36 [95% CI, 1.23-1.50]), and pfcrt K76 (AL: 3.37 [95% CI, 1.85-6.16]; DP: 5.84 [95% CI, 1.94-17.53], and decreased for pfmdr1 Y184 (AL: 0.78 [95% CI, .70-.86]; DP: 0.84 [95% CI, .76-1.50]); changes were consistently greater in the AL arm. Recent AL treatment selected for pfmdr1 N86, D1246, and 184F in subsequent episodes; DP selected for the opposite alleles.

Conclusions: Genotypes with decreased sensitivity to AL components increased over time. This increase was greater in children receiving AL, suggesting that the choice of treatment regimen can profoundly influence parasite genetics and drug sensitivity.

Clinical trials registration: NCT00527800.

Keywords: Plasmodium falciparum; artemether-lumefantrine; dihydroartemisinin-piperaquine; pfcrt; pfmdr1.

© The Author 2014. Published by Oxford University Press on behalf of the Infectious Diseases Society of America. All rights reserved. For Permissions, please e-mail: journals.permissions@oup.com.

Figures

Figure 1.

Trial and experimental profile. Abbreviations: AL, artemether-lumefantrine; DP, dihydroartemisinin-piperaquine.

Figure 2.

Allele prevalences over time. Prevalences, each based on analysis of 50 samples per treatment arm, are shown over 3-month intervals for wild-type, mixed, and mutant alleles of pfmdr1 86, 184, and 1246; pfcrt 76; and pfmrp1 876 and 1466. Frequency curves, based on MalHaploFreq frequency estimations for each year, are superimposed; error bars represent the 95% confidence intervals for the estimates. Abbreviations: AL, artemether-lumefantrine; DP, dihydroartemisinin-piperaquine.

Figure 3.

Impact of prior therapy on allele prevalences. The prevalences of wild-type, mixed, and mutant sequences at the indicated alleles are shown for samples from episodes that emerged within the indicated time after a prior treatment with artemether-lumefantrine (AL) or dihydroartemisinin-piperaquine (DP). Based on consideration of the distribution of recurrent malaria episodes over time, samples from episodes that emerged more than 56 days and 70 days after treatment are considered not to be under selection for AL and DP, respectively. Asterisks indicate wild-type allele prevalences that are significantly different from those for samples not under selection (P < .05, χ2 test). Abbreviations: AL, artemether-lumefantrine; DP, dihydroartemisinin-piperaquine.