Artemether-Lumefantrine treatment selects Plasmodium falciparum multidrug resistance 1 (pfmdr1) increased copy number among African malaria infections.

Abstract

Background: Decreased efficacy of artemether-lumefantrine, the globally most used antimalarial, has recently emerged in Africa.

Methods: An efficacy trial based on directly observed artemether-lumefantrine therapy at Bengo, Northern Angola. 100 Plasmodium falciparum uncomplicated malaria patients (2-10 year-old) were enrolled, hospitalized for the treatment period, and followed up for 42 days. PCR correction was performed with pfmsp1/2 + glurp, with analysis considering 2 or 3 coincident markers. Infections were tested by qPCR for pfmdr1 copy number (pfmdr1xN), a potential Plasmodium falciparum marker of lumefantrine resistance previously identified in the region. In-vitro clone mixtures were built and used to determine the relation between qPCR copy number scores and actual intra-infection quantitative fractions of pfmdr1xN.

Results: We observed a significant post-treatment selection of gene amplification, suggesting a role in the parasite in vivo response to this drug. pfmdr1x2 qPCR scores of 1.3, 1.4 and 1.5 were determined to correspond to 15%, 25% and 35% intra-infection rates. Patients carrying infections with a score ≥1.4 at baseline were linked to decreased AL day 42 efficacy (79% vs 97% single-copy pfmdr1). All infections were pfmdr1 N86 carriers and no pfk13 mutations were found.

Conclusions: Our study suggests pfmdr1xN as a marker of P. falciparum in vivo response to lumefantrine in Africa, while pointing for patients carrying infections with a pre-treatment pfmdr1xN score ≥1.4 before treatment as a group experiencing decreased artemether-lumefantrine performance.