Exposure to artemisinin at the trophozoite stage increases sexual conversion rates in the malaria parasite Plasmodium falciparum

ABSTRACTMalaria transmission is dependent on formation of gametocytes in the human blood. The sexual conversion rate, the proportion of asexual parasites that convert into gametocytes at each multiplication cycle, is variable and reflects the relative parasite investment between transmission and maintaining the infection. The impact of environmental factors such as drugs on sexual conversion rates is not well understood. We developed a robust assay using gametocyte-reporter parasite lines to accurately measure the impact of drugs on conversion rates, independently from their gametocytocidal activity. We found that exposure to subcurative doses of the frontline antimalarial drug dihydroartemisinin (DHA) at the trophozoite stage resulted in a ~4-fold increase in sexual conversion. In contrast, no increase was observed when ring stages were exposed or in cultures in which sexual conversion was stimulated by choline depletion. Our results reveal a complex relationship between antimalarial drugs and sexual conversion, with potential public health implications.

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Artemisinin exposure at the ring or trophozoite stage impacts Plasmodium falciparum sexual conversion differently

eLife ◽

10.7554/elife.60058 ◽

2020 ◽

Vol 9 ◽

Author(s):

Harvie P Portugaliza ◽

Shinya Miyazaki ◽

Fiona JA Geurten ◽

Christopher Pell ◽

Anna Rosanas-Urgell ◽

...

Keyword(s):

Public Health ◽

Plasmodium Falciparum ◽

Complex Relationship ◽

Trophozoite Stage ◽

Fourfold Increase ◽

Conversion Rates ◽

Multiplication Cycle ◽

The Impact ◽

Gametocytocidal Activity ◽

Potential Public Health

Malaria transmission is dependent on the formation of gametocytes in the human blood. The sexual conversion rate, the proportion of asexual parasites that convert into gametocytes at each multiplication cycle, is variable and reflects the relative parasite investment between transmission and maintaining the infection. The impact of environmental factors such as drugs on sexual conversion rates is not well understood. We developed a robust assay using gametocyte-reporter parasite lines to accurately measure the impact of drugs on sexual conversion rates, independently from their gametocytocidal activity. We found that exposure to subcurative doses of the frontline antimalarial drug dihydroartemisinin (DHA) at the trophozoite stage resulted in a ~ fourfold increase in sexual conversion. In contrast, no increase was observed when ring stages were exposed or in cultures in which sexual conversion was stimulated by choline depletion. Our results reveal a complex relationship between antimalarial drugs and sexual conversion, with potential public health implications.

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Reporter lines based on the gexp02 promoter enable early quantification of sexual conversion rates in the malaria parasite Plasmodium falciparum

Scientific Reports ◽

10.1038/s41598-019-50768-y ◽

2019 ◽

Vol 9 (1) ◽

Cited By ~ 10

Author(s):

Harvie P. Portugaliza ◽

Oriol Llorà-Batlle ◽

Anna Rosanas-Urgell ◽

Alfred Cortés

Keyword(s):

Plasmodium Falciparum ◽

Accurate Determination ◽

Epidemiological Studies ◽

Fluorescent Reporter ◽

Conversion Rates ◽

Parasite Plasmodium ◽

Parasite Plasmodium Falciparum ◽

Transgenic Lines ◽

Parasite Replication ◽

The Impact

Abstract Transmission of malaria parasites from humans to mosquito vectors requires that some asexual parasites differentiate into sexual forms termed gametocytes. The balance between proliferation in the same host and conversion into transmission forms can be altered by the conditions of the environment. The ability to accurately measure the rate of sexual conversion under different conditions is essential for research addressing the mechanisms underlying sexual conversion, and to assess the impact of environmental factors. Here we describe new Plasmodium falciparum transgenic lines with genome-integrated constructs in which a fluorescent reporter is expressed under the control of the promoter of the gexp02 gene. Using these parasite lines, we developed a sexual conversion assay that shortens considerably the time needed for an accurate determination of sexual conversion rates, and dispenses the need to add chemicals to inhibit parasite replication. Furthermore, we demonstrate that gexp02 is expressed specifically in sexual parasites, with expression starting as early as the sexual ring stage, which makes it a candidate marker for circulating sexual rings in epidemiological studies.

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Transport of the essential nutrient isoleucine in human erythrocytes infected with the malaria parasite Plasmodium falciparum

Blood ◽

10.1182/blood-2005-11-026963 ◽

2006 ◽

Vol 109 (5) ◽

pp. 2217-2224 ◽

Cited By ~ 70

Author(s):

Rowena E. Martin ◽

Kiaran Kirk

Keyword(s):

Plasmodium Falciparum ◽

Host Cell ◽

Malaria Parasite ◽

Human Erythrocytes ◽

Extracellular Medium ◽

Host Cell Membrane ◽

Trophozoite Stage ◽

Parasite Plasmodium ◽

Parasite Plasmodium Falciparum ◽

Essential Nutrient

AbstractThe intraerythrocytic malaria parasite derives much of its requirement for amino acids from the digestion of the hemoglobin of its host cell. However, one amino acid, isoleucine, is absent from adult human hemoglobin and must therefore be obtained from the extracellular medium. In this study we have characterized the mechanisms involved in the uptake of isoleucine by the intraerythrocytic parasite. Under physiologic conditions the rate of transport of isoleucine into human erythrocytes infected with mature trophozoite-stage Plasmodium falciparum parasites is increased to approximately 5-fold that in uninfected cells, with the increased flux being via the new permeability pathways (NPPs) induced by the parasite in the host cell membrane. Transport via the NPPs ensures that protein synthesis is not rate limited by the flux of isoleucine across the erythrocyte membrane. On entering the infected erythrocyte, isoleucine is taken up into the parasite via a saturable, ATP-, Na+-, and H+-independent system which has the capacity to mediate the influx of isoleucine in exchange for leucine (liberated from hemoglobin). The accumulation of radiolabeled isoleucine within the parasite is mediated by a second (high-affinity, ATP-dependent) mechanism, perhaps involving metabolism and/or the concentration of isoleucine within an intracellular organelle.

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