Polymorphisms in the K13-Propeller Gene in Artemisinin-Resistant in Mice.

Introduction: Artemisinin-based combination therapies (ACTs) act as first-line antimalarial drugs and play a crucial role in the successful control of malaria. However, the recent emergence of resistance of to ACTs in South East Asia is of particular concern. Hence, there is an urgent need to identify the genetic determinants of and understand the molecular mechanisms underpinning such resistance. Artemisinin resistance (AR) is primarily driven by the mutations in the K13 protein, which is widely recognized as the major molecular marker of AR. However, association of K13 mutations with in vivo AR has been ambiguous due to the absence of a tractable model.

Methods: In this study, we have successfully produced artemisinin- and piperaquine-resistant K173 following drug administrations. Prolonged parasite clearance and early recrudescence were found following daily exposure to high doses of artemisinin and piperaquine. We have also sequenced the DNA of artemisinin-resistant strains and piperaquine-resistant strains of K173 to explore the relationship between and AR.

Results: The resistance index of K173 reached 12.4 after 30 artemisinin-resistant generations, but AR declined gradually after 30 generations. On the 50th generation, the resistance index of artemisinin-resistant strains was only 5.0 compared with the severe drug resistance of piperaquine-resistant strains (I=148.8). DNA sequencing of artemisinin-resistant strains showed that there were 9 meaningful mutations at K13-propeller domain, but the above mutations did not include common clinical point mutations.

Conclusion: Our data show that artemisinin is less susceptible to severe resistance compared with other antimalarial drugs. In addition, mutation on K13 has a multi-drug-resistant phenotype and may be used as a biomarker to monitor its resistance. More studies need to be conducted on the new mutations detected so as to understand their association, if any, with ACT resistance.