title: Targeting the cell stress response of Plasmodium falciparum to overcome artemisinin resistance.
abstract: Successful control of falciparum malaria depends greatly on treatment with artemisinin combination therapies. Thus, reports that resistance to artemisinins (ARTs) has emerged, and that the prevalence of this resistance is increasing, are alarming. ART resistance has recently been linked to mutations in the K13 propeller protein. We undertook a detailed kinetic analysis of the drug responses of K13 wild-type and mutant isolates of Plasmodium falciparum sourced from a region in Cambodia (Pailin). We demonstrate that ART treatment induces growth retardation and an accumulation of ubiquitinated proteins, indicative of a cellular stress response that engages the ubiquitin/proteasome system. We show that resistant parasites exhibit lower levels of ubiquitinated proteins and delayed onset of cell death, indicating an enhanced cell stress response. We found that the stress response can be targeted by inhibiting the proteasome. Accordingly, clinically used proteasome inhibitors strongly synergize ART activity against both sensitive and resistant parasites, including isogenic lines expressing mutant or wild-type K13. Synergy is also observed against Plasmodium berghei in vivo. We developed a detailed model of parasite responses that enables us to infer, for the first time, in vivo parasite clearance profiles from in vitro assessments of ART sensitivity. We provide evidence that the clinical marker of resistance (delayed parasite clearance) is an indirect measure of drug efficacy because of the persistence of unviable parasites with unchanged morphology in the circulation, and we suggest alternative approaches for the direct measurement of viability. Our model predicts that extending current three-day ART treatment courses to four days, or splitting the doses, will efficiently clear resistant parasite infections. This work provides a rationale for improving the detection of ART resistance in the field and for treatment strategies that can be employed in areas with ART resistance.
authors.affiliation: Department of Biochemistry and Molecular Biology and ARC Centre of Excellence for Coherent X-ray Science, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Con
authors.initials: C
authors.lastname: Dogovski
authors.affiliation: Department of Biochemistry and Molecular Biology and ARC Centre of Excellence for Coherent X-ray Science, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Stanley C
authors.initials: SC
authors.lastname: Xie
authors.affiliation: John Curtin School of Medical Research, the Australian National University, Canberra, Australian Capital Territory, Australia; Australian School of Advanced Medicine, Macquarie University, Sydney, New South Wales, Australia.
authors.forename: Gaetan
authors.initials: G
authors.lastname: Burgio
authors.affiliation: Department of Biochemistry and Molecular Biology and ARC Centre of Excellence for Coherent X-ray Science, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Jess
authors.initials: J
authors.lastname: Bridgford
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore.
authors.forename: Sachel
authors.initials: S
authors.lastname: Mok
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Parkville, Victoria, Australia; Murdoch Childrens Research Institute, Royal Childrens Hospital, Victoria, Australia.
authors.forename: James M
authors.initials: JM
authors.lastname: McCaw
authors.affiliation: Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand.
authors.forename: Kesinee
authors.initials: K
authors.lastname: Chotivanich
authors.affiliation: Department of Biochemistry and Molecular Biology and ARC Centre of Excellence for Coherent X-ray Science, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Shannon
authors.initials: S
authors.lastname: Kenny
authors.affiliation: Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America.
authors.forename: Nina
authors.initials: N
authors.lastname: Gnädig
authors.affiliation: Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America.
authors.forename: Judith
authors.initials: J
authors.lastname: Straimer
authors.affiliation: School of Biological Sciences, Nanyang Technological University, Singapore.
authors.forename: Zbynek
authors.initials: Z
authors.lastname: Bozdech
authors.affiliation: Department of Microbiology and Immunology, Columbia University Medical Center, New York, New York, United States of America; Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, New York, United States of America.
authors.forename: David A
authors.initials: DA
authors.lastname: Fidock
authors.affiliation: Centre for Epidemiology and Biostatistics, Melbourne School of Population and Global Health, University of Melbourne, Parkville, Victoria, Australia.
authors.forename: Julie A
authors.initials: JA
authors.lastname: Simpson
authors.affiliation: Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand; Centre for Tropical Medicine, Nuffield Department of Clinical Medicine, Oxford, United Kingdom.
authors.forename: Arjen M
authors.initials: AM
authors.lastname: Dondorp
authors.affiliation: John Curtin School of Medical Research, the Australian National University, Canberra, Australian Capital Territory, Australia.
authors.forename: Simon
authors.initials: S
authors.lastname: Foote
authors.affiliation: Department of Biochemistry and Molecular Biology and ARC Centre of Excellence for Coherent X-ray Science, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Nectarios
authors.initials: N
authors.lastname: Klonis
authors.affiliation: Department of Biochemistry and Molecular Biology and ARC Centre of Excellence for Coherent X-ray Science, Bio21 Molecular Science and Biotechnology Institute, The University of Melbourne, Melbourne, Victoria, Australia.
authors.forename: Leann
authors.initials: L
authors.lastname: Tilley
mesh_terms: D000818:Animals; D037621:Artemisinins / Q000494:pharmacology*; D004305:Dose-Response Relationship, Drug; D004351:Drug Resistance; D018503:Genome, Protozoan; D009154:Mutation; D010963:Plasmodium falciparum / Q000187:drug effects / Q000235:genetics / Q000502:physiology*; D013312:Stress, Physiological
chemical_list: D037621:Artemisinins; C031327:artemisinin