Impact of treatment and re-treatment with artemether-lumefantrine and artesunate-amodiaquine on selection of Plasmodium falciparum multidrug resistance gene-1 polymorphisms in the Democratic Republic of Congo and Uganda

BACKGROUND: The emergence of resistance against artemisinin combination treatment is a major concern for malaria control. ACTs are recommended as the rescue treatment, however, there is limited evidence as to whether treatment and re-treatment with ACTs select for drug-resistant P. falciparum parasites. Thus, the purpose of the present study is to investigate the impact of (re-)treatment using artesunate-amodiaquine (ASAQ) and artemether-lumefantrine (AL) on the selection of P. falciparum multidrug resistance-1 (Pfmdr1) alleles in clinical settings.METHODS: P. falciparum positive samples were collected from children aged 12-59 months in a clinical trial in DR Congo and Uganda. Pfmdr1 single nucleotide polymorphisms (SNPs) analysis at codons N86Y, Y184F, and D1246Y were performed at baseline and post-treatment with either AL or ASAQ as a rescue treatment using nested PCR followed by restriction fragment length polymorphism (RFLP) assays.RESULTS: The pre-treatment prevalence of Pfmdr1 N86 and D1246Y varied significantly between the sites, (p>0.001) and (p = 0.013), respectively. There was borderline significant directional selection for Pfmdr1 184F in recurrent malaria infections after treatment with AL in Uganda site (p = 0.05). Pfmdr1 NFD haplotype did not significantly change in post-treatment infections after re-treatment with either AL or ASAQ. Comparison between pre-treatment and post-treatment recurrences did not indicate directional selection of Pfmdr1 N86, D1246 alleles in the pre-RCT, RCT and post-RCT phases in both AL and ASAQ treatment arms. Pfmdr1 86Y was significantly associated with reduced risk of AL treatment failure (RR = 0.34, 95% CI:0.11-1.05, p = 0.04) while no evidence for D1246 allele (RR = 1.02; 95% CI: 0.42-2.47, p = 1.0). Survival estimates showed that the Pfmdr1 alleles had comparable mean-time to PCR-corrected recrudescence and new infections in both AL and ASAQ treatment arms.CONCLUSION: We found limited impact o