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Malar J. 2015 May 22;14:213. doi: 10.1186/s12936-015-0718-z.

Nowhere to hide: interrogating different metabolic parameters of Plasmodium falciparum gametocytes in a transmission blocking drug discovery pipeline towards malaria elimination.

Author information

1
Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa. Janette.reader@up.ac.za.
2
Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa. mariette.botha@up.ac.za.
3
Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria, 0001, South Africa. ANTheron@csir.co.za.
4
Plasmodium Molecular Research Unit, Wits Research Institute for Malaria, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg, 2193, South Africa. sonja.lauterbach@gmail.com.
5
Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria, 0001, South Africa. clairerossouw@gmail.com.
6
Plasmodium Molecular Research Unit, Wits Research Institute for Malaria, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg, 2193, South Africa. dewaldtengelbrecht@gmail.com.
7
Plasmodium Molecular Research Unit, Wits Research Institute for Malaria, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg, 2193, South Africa. melfried88@gmail.com.
8
Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa. annel.smit@up.ac.za.
9
Medicines for Malaria Venture, Geneva, Switzerland. leroyd@mmv.org.
10
Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria, 0001, South Africa. DMancama@csir.co.za.
11
Plasmodium Molecular Research Unit, Wits Research Institute for Malaria, Department of Molecular Medicine and Haematology, School of Pathology, Faculty of Health Sciences, University of the Witwatersrand and National Health Laboratory Service, Johannesburg, 2193, South Africa. theresa.coetzer@nhls.ac.za.
12
Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa. lbirkholtz@up.ac.za.

Abstract

BACKGROUND:

The discovery of malaria transmission-blocking compounds is seen as key to malaria elimination strategies and gametocyte-screening platforms are critical filters to identify active molecules. However, unlike asexual parasite assays measuring parasite proliferation, greater variability in end-point readout exists between different gametocytocidal assays. This is compounded by difficulties in routinely producing viable, functional and stage-specific gametocyte populations. Here, a parallel evaluation of four assay platforms on the same gametocyte populations was performed for the first time. This allowed the direct comparison of the ability of different assay platforms to detect compounds with gametocytocidal activity and revealed caveats in some assay readouts that interrogate different parasite biological functions.

METHODS:

Gametocytogenesis from Plasmodium falciparum (NF54) was optimized with a robust and standardized protocol. ATP, pLDH, luciferase reporter and PrestoBlue® assays were compared in context of a set of 10 reference compounds. The assays were performed in parallel on the same gametocyte preparation (except for luciferase reporter lines) using the same drug preparations (48 h). The remaining parameters for each assay were all comparable.

RESULTS:

A highly robust method for generating viable and functional gametocytes was developed and comprehensively validated resulting in an average gametocytaemia of 4%. Subsequent parallel assays for gametocytocidal activity indicated that different assay platforms were not able to screen compounds with variant chemical scaffolds similarly. Luciferase reporter assays revealed that synchronized stage-specific gametocyte production is essential for drug discovery, as differential susceptibility in various gametocyte developmental populations is evident.

CONCLUSIONS:

With this study, the key parameters for assays aiming at testing the gametocytocidal activity of potential transmission blocking molecules against Plasmodium gametocytes were accurately dissected. This first and uniquely comparative study emphasizes differential effects seen with the use of different assay platforms interrogating variant biological systems. Whilst this data is informative from a biological perspective and may provide indications of the drug mode of action, it does highlight the care that must be taken when screening broad-diversity chemotypes with a single assay platform against gametocytes for which the biology is not clearly understood.

PMID:
25994518
PMCID:
PMC4449569
DOI:
10.1186/s12936-015-0718-z
[Indexed for MEDLINE]
Free PMC Article

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