Evolution of Multidrug Resistance in Plasmodium falciparum: a Longitudinal Study of Genetic Resistance Markers in the Greater Mekong Subregion

Abstract

Increasing drug resistance in Plasmodium falciparum to artemisinins and their ACT partner drugs jeopardises effective antimalarial treatment. Resistance is worst in the Greater Mekong Subregion. Monitoring genetic markers of resistance can help to guide antimalarial therapy. Markers of resistance to artemisinins ( PfKelch mutations), mefloquine (amplification of P. falciparum multidrug resistance-1, PfMDR1, ), and piperaquine ( PfPlasmepsin2/3 amplification and specific P. falciparum chloroquine resistance transporter, PfCRT, mutations) were assessed in 6,722 P. falciparum samples from Vietnam, Lao PDR, Cambodia, Thailand, Myanmar between 2007 and 2019. Against a high background prevalence of PfKelch mutations, PfMDR1 and PfPlasmepsin2/3 amplification closely followed regional drug pressures over time. PfPlasmepsin2/3 amplification preceded piperaquine-resistance associated PfCRT mutations in Cambodia, and reached a peak prevalence of 23/28 (82%) in 2015. This declined to 57/156 (38%) after changing first-line treatment away from dihydroartemisinin-piperaquine to artesunate-mefloquine (ASMQ) between 2014 and 2017. PfMDR1 amplification increased from 0/293 (0%) between 2012 and 2017 to 12/156 (8%) in 2019. Amplification of PfMDR1 and PfPlasmepsin2/3 in the same parasites was extremely rare (4/6,722; 0.06%) and dispersed over time. Mechanisms conferring mefloquine and piperaquine resistance may be counterbalancing. This supports the development of ASMQ plus piperaquine as a triple artemisinin combination therapy.

Artemisinin resistance in the malaria parasite, Plasmodium falciparum, originates from its initial transcriptional response

“…Since its emergence in 2009, artemisinin resistance exerted strong selection effects on the GMS P. falciparum population due to a continuous drug pressure resulting from intensive high-coverage treatment programmes implemented by all countries in the region 11 , 43 , 70 . There is now a clear distinction between the P. falciparum population in the wGMS (Myanmar, Thai-Myanmar border, and Bangladesh) and eGMS (Cambodia Laos and Southern Vietnam), the latter of which likely provided the supporting genetic background for artemisinin resistance 40 .…”

Expert perspectives on the introduction of Triple Artemisinin-based Combination Therapies (TACTs) in Southeast Asia: a Delphi study

“…ACT combines a highly potent, rapidly cleared artemisinin derivative and a less potent, slowly cleared partner drug such as lumefantrine, amodiaquine, piperaquine, pyronaridine or mefloquine. A worrying recent development is multidrug resistance that has emerged to these artemisinin and partner drug combinations and is now spreading through large regions of Southeast Asia [ 7 – 9 ]. In response, policy makers in Cambodia, the country with the highest burden of multidrug-resistant malaria, opt to switch between ACTs when treatment failure is observed [ 10 , 11 ].…”

Molecular surveillance of dihydroartemisinin-piperaquine resistance in northwestern Thailand

“…Ampli cation of plasmepsin-2 is widely used as a marker to trace PPQ resistance [9,[12][13][14][15]. Previous studies suggested that this genotype was restricted to eastern GMS [10,14,15]. Consistent with these reports, none of the P. falciparum isolates in Tak province from 2013-2019 had plasmepsin-2 ampli cation.…”