Volume 13 Supplement 1

Challenges in malaria research: Core science and innovation

Open Access

Novel phenotypic resistance to artemisinin results in reduced exposure to drug at the most sensitive stage of intraerythrocytic development in Plasmodium falciparum

  • Amanda Hott1,
  • Debora Casandra1,
  • Kansas Sparks1,
  • Geocel Castarnes1,
  • Amanda Rutter1 and
  • Dennis Kyle1
Malaria Journal201413(Suppl 1):P43

https://doi.org/10.1186/1475-2875-13-S1-P43

Published: 22 September 2014

Background

Recent emergence of artemisinin resistant Plasmodium falciparum in Southeast Asia has threatened malaria control efforts across the globe. Clinical resistance is characterized by reduced rates of parasite clearance following treatment; yet in vitro phenotypes of artemisinin resistance suitable for elucidating molecular mechanisms of resistance remain elusive.

Materials and methods

In this study we culture adapted and characterized a series of P. falciparum clones from Cambodia; these included parasites from cases with reduced parasite clearance rates in vivo. In vitro artemisinin resistance phenotypes were assessed by using T0 3H-hypoxanthine assays, a novel parasite clearance assay, microscopy and flow cytometry to characterize intraerythrocytic development, and limiting dilution to assess parasite viability.

Results

Detailed phenotypic characterization of artemisinin resistant P. falciparum revealed a series of complex phenotypes that included 4-8 fold resistance to multiple artemisinin derivatives in vitro that is stable for >1 year. By using a novel parasite clearance assay we observed reduced parasite reduction rates (PRRs) for resistant clones in vitro and these were positively correlated with parasitemia clearance half-lives in vivo. Most remarkably we discovered an altered pattern of intraerythrocytic development of the artemisinin resistant clones of P. falciparum. In the absence of any drug pressure, resistant clones exhibited a prolonged phase of ring stage development followed by a significantly shortened trophozoite stage of development. Given that ring stages are the most resistant to inhibition by artemisinin and the trophozoites are the most susceptible, this novel phenotypic resistance to artemisinin results in reduced exposure to drug at the most sensitive stage of development (trophozoite). Additional confirmation of the selective pressure driving this phenotype is one resistant clone exhibited a 12 hour shorter erythrocytic life cycle that also compressed the trophozoite stage of development.

Conclusions

The evolution of artemisinin resistance appears to select for altered intraerythrocytic development such that the most susceptible stage of development is significantly reduced in the cell cycle. Our data demonstrate that altered intraerythrocytic development is a novel mechanism of phenotypic resistance to artemisinin antimalarial drugs.

Authors’ Affiliations

(1)
University of South Florida

Copyright

© Hott et al; licensee BioMed Central Ltd. 2014

This article is published under license to BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. The Creative Commons Public Domain Dedication waiver (http://creativecommons.org/publicdomain/zero/1.0/) applies to the data made available in this article, unless otherwise stated.

Comments

By submitting a comment you agree to abide by our Terms and Community Guidelines. If you find something abusive or that does not comply with our terms or guidelines please flag it as inappropriate.

Advertisement