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Acta Parasitologica

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Volume 61, Issue 4


Development of a rapid and reliable assay for in vitro determination of compound cidality against the asexual stages of Plasmodium falciparum

Pavithra Viswanath
  • Corresponding author
  • Department of Radiology and Biomedical Imaging, University of California San Francisco, 1700 4 Street, San Francisco, California 94143, United States of America
  • Email
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Sapna Morayya
  • Department of Radiology and Biomedical Imaging, University of California San Francisco, 1700 4 Street, San Francisco, California 94143, United States of America
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Nikhil Rautela
  • Department of Radiology and Biomedical Imaging, University of California San Francisco, 1700 4 Street, San Francisco, California 94143, United States of America
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
/ Achyut Sinha
  • Department of Radiology and Biomedical Imaging, University of California San Francisco, 1700 4 Street, San Francisco, California 94143, United States of America
  • Other articles by this author:
  • De Gruyter OnlineGoogle Scholar
Published Online: 2016-10-24 | DOI: https://doi.org/10.1515/ap-2016-0115


The pace of anti-malarial drug discovery is often impeded due to the lack of tools to determine the cidality of compounds in vitro. An anti-malarial compound must have a cidal mode of action, i.e. kill parasites, in order to quickly reduce parasite load. A static compound that merely inhibits growth must be identified early on in the discovery cascade. In this paper, we describe a high-throughput fluorescent assay for determination of the cidality of an anti-malarial compound. The assay works on the principle that cultures treated with a static compound will exhibit re-growth while treatment with a cidal compound leads to a marked reduction in parasite number. Parasite cultures are treated with the drug for 48 or 72 h following which the drug is washed off. Cultures are allowed to recover in drug-free media for 72 h and DNA content estimated using the fluorescent dye SyBR Green I. Following estimation of IC50 and IC99 values, we find that the IC99/IC50 ratio is a reliable indicator of the cidality of a compound. Cidal compounds like artemisinin and chloroquine display an IC99/IC50 ratio <5 while the ratio for a static compound like atovaquone is <5. This correlation holds true for various anti-malarial drugs with known modes of action. Importantly, the IC99/IC50 ratio drops to <5 when a compound becomes cidal in action with longer duration of treatment. The assay is robust, reliable and provides a fast and effective means for prioritizing cidal compounds for progression along the drug discovery cascade.

Keywords: Anti-malarial; cidality; mode of action; malaria; drug discovery; SyBR Green IIntroduction


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About the article

Received: 2016-06-01

Revised: 2016-07-18

Accepted: 2016-08-04

Published Online: 2016-10-24

Published in Print: 2016-12-01

Conflict of Interests

Authors declares no conflict of interests.

Citation Information: Acta Parasitologica, Volume 61, Issue 4, Pages 828–835, ISSN (Online) 1896-1851, ISSN (Print) 1230-2821, DOI: https://doi.org/10.1515/ap-2016-0115.

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