Spleen promotes clearance of artesunate-treated P. falciparum in Aotus, independent of the PfK13 C580Y mutation

Introduction: Artemisinin and its derivatives (ART) are vital frontline antimalarial drugs that rapidly clear parasitemia but are frequently followed by recrudescences if used as a monotherapy. Therefore, ART must be used in combination with one or more partner drugs to ensure complete cure of infection. In regions of Southeast Asia including Cambodia, prolonged parasite clearance half-lives (>5 h) have been associated with parasite populations carrying mutations in the Plasmodium falciparum Kelch-propeller protein K13, a particular example being C580Y. However, different parasite clearance times were not linked to C580Y in Aotus nancymaae New World monkeys infected with parasites from a cross between Ghanaian (GB4, K13 C580) and Cambodian (803, K13 C580Y) parental lines. However, in experiments to evaluate for an effect of the spleen, a possible difference was observed between spleen-intact versus splenectomized monkeys infected with the FVO (K13 C580) line that is a standard for vaccine and drug studies.Methods: Using the CRISPR-Cas9 system we engineered the C580Y substitution in the pfK13 gene of FVO to compare isogenic lines in spleen-intact and splenectomized animals.Results: Treatment of Aotus nancymaae and Aotus lemurinus griseimembra with three daily doses of 4 mg/kg of Artesunate (AS) revealed no significant difference in parasite clearance half-life (t1/2) between the isogenic lines. Moreover, recrudescences happened irrespective of their K13 status.Discussion: These results address important gaps in understanding the chemotherapeutic effects of the artemisinin drugs, PfK13 phenotypes, and parasite splenic clearance following drug treatment.