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Gebru T, Lalremruata A, Kremsner PG, Mordmüller B, Held J. Life-span of in vitro differentiated Plasmodium falciparum gametocytes. Malar J 2017; 16:330. [PMID: 28800735 PMCID: PMC5553604 DOI: 10.1186/s12936-017-1986-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2017] [Accepted: 08/07/2017] [Indexed: 11/18/2022] Open
Abstract
Background The sexual stages (gametocytes) of Plasmodium falciparum do not directly contribute to the pathology of malaria but are essential for transmission of the parasite from the human host to the mosquito. Mature gametocytes circulate in infected human blood for several days and their circulation time has been modelled mathematically from data of previous in vivo studies. This is the first time that longevity of gametocytes is studied experimentally in vitro. Methods The in vitro longevity of P. falciparum gametocytes of 1 clinical isolate and 2 laboratory strains was assessed by three different methods: microscopy, flow cytometry and reverse transcription quantitative real-time PCR (RT-qPCR). Additionally, the rate of gametocytogenesis of the used P. falciparum strains was compared. Results The maximum in vitro lifespan of P. falciparum gametocytes reached almost 2 months (49 days by flow cytometry, 46 days by microscopy, and at least 52 days by RT-qPCR) from the starting day of gametocyte culture to death of last parasite in the tested strains with an average 50% survival rate of 6.5, 2.6 and 3.5 days, respectively. Peak gametocytaemia was observed on average 19 days after initiation of gametocyte culture followed by a steady decline due to natural decay of the parasites. The rate of gametocytogenesis was highest in the NF54 strain. Conclusions Plasmodium falciparum mature gametocytes can survive up to 16–32 days (at least 14 days for mature male gametocytes) in vitro in absence of the influence of host factors. This confirms experimentally a previous modelling estimate that used molecular tools for gametocyte detection in treated patients. The survival time might reflect the time the parasite can be transmitted to the mosquito after clearance of asexual parasites. These results underline the importance of efficient transmission blocking agents in the fight against malaria. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1986-6) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Tamirat Gebru
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany.,German Centre for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany.,Department of Medical Laboratory Sciences, College of Medical and Health Sciences, Haramaya University, Harar, Ethiopia
| | - Albert Lalremruata
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany.,German Centre for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany
| | - Peter G Kremsner
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany.,German Centre for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany
| | - Benjamin Mordmüller
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany.,German Centre for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany
| | - Jana Held
- Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany. .,German Centre for Infection Research (DZIF), partner site Tübingen, Tübingen, Germany.
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Niikura M, Komatsuya K, Inoue SI, Matsuda R, Asahi H, Inaoka DK, Kita K, Kobayashi F. Suppression of experimental cerebral malaria by disruption of malate:quinone oxidoreductase. Malar J 2017; 16:247. [PMID: 28606087 PMCID: PMC5469008 DOI: 10.1186/s12936-017-1898-5] [Citation(s) in RCA: 18] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2017] [Accepted: 06/06/2017] [Indexed: 01/03/2023] Open
Abstract
Background Aspartate, which is converted from oxaloacetate (OAA) by aspartate aminotransferase, is considered an important precursor for purine salvage and pyrimidine de novo biosynthesis, and is thus indispensable for the growth of Plasmodium parasites at the asexual blood stages. OAA can be produced in malaria parasites via two routes: (i) from phosphoenolpyruvate (PEP) by phosphoenolpyruvate carboxylase (PEPC) in the cytosol, or (ii) from fumarate by consecutive reactions catalyzed by fumarate hydratase (FH) and malate:quinone oxidoreductase (MQO) in the mitochondria of malaria parasites. Although PEPC-deficient Plasmodium falciparum and Plasmodium berghei (rodent malaria) parasites show a growth defect, the mutant P. berghei can still cause experimental cerebral malaria (ECM) with similar dynamics to wild-type parasites. In contrast, the importance of FH and MQO for parasite viability, growth and virulence is not fully understood because no FH- and MQO-deficient P. falciparum has been established. In this study, the role of FH and MQO in the pathogenicity of asexual-blood-stage Plasmodium parasites causing cerebral malaria was examined. Results First, FH- and MQO-deficient parasites were generated by inserting a luciferase-expressing cassette into the fh and mqo loci in the genome of P. berghei ANKA strain. Second, the viability of FH-deficient and MQO-deficient parasites that express luciferase was determined by measuring luciferase activity, and the effect of FH or MQO deficiency on the development of ECM was examined. While the viability of FH-deficient P. berghei was comparable to that of control parasites, MQO-deficient parasites exhibited considerably reduced viability. FH activity derived from erythrocytes was also detected. This result and the absence of phenotype in FH-deficient P. berghei parasites suggest that fumarate can be metabolized to malate by host or parasite FH in P. berghei-infected erythrocytes. Furthermore, although the growth of FH- and MQO-deficient parasites was impaired, the development of ECM was suppressed only in mice infected with MQO-deficient parasites. Conclusions These findings suggest that MQO-mediated mitochondrial functions are required for development of ECM of asexual-blood-stage Plasmodium parasites. Electronic supplementary material The online version of this article (doi:10.1186/s12936-017-1898-5) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Mamoru Niikura
- Department of Infectious Diseases, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - Keisuke Komatsuya
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, 852-8523, Japan.,Department of Biomedical Chemistry, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Shin-Ichi Inoue
- Department of Infectious Diseases, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - Risa Matsuda
- Department of Infectious Diseases, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - Hiroko Asahi
- Department of Infectious Diseases, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan
| | - Daniel Ken Inaoka
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, 852-8523, Japan.,Department of Biomedical Chemistry, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Kiyoshi Kita
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, 852-8523, Japan.,Department of Biomedical Chemistry, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Fumie Kobayashi
- Department of Infectious Diseases, Kyorin University School of Medicine, 6-20-2 Shinkawa, Mitaka, Tokyo, 181-8611, Japan.
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Hundreds of dual-stage antimalarial molecules discovered by a functional gametocyte screen. Nat Commun 2017; 8:15160. [PMID: 28513586 PMCID: PMC5442318 DOI: 10.1038/ncomms15160] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2016] [Accepted: 03/03/2017] [Indexed: 02/07/2023] Open
Abstract
Plasmodium falciparum stage V gametocytes are responsible for parasite transmission, and drugs targeting this stage are needed to support malaria elimination. We here screen the Tres Cantos Antimalarial Set (TCAMS) using the previously developed P. falciparum female gametocyte activation assay (Pf FGAA), which assesses stage V female gametocyte viability and functionality using Pfs25 expression. We identify over 400 compounds with activities <2 μM, chemically classified into 57 clusters and 33 singletons. Up to 68% of the hits are chemotypes described for the first time as late-stage gametocyte-targeting molecules. In addition, the biological profile of 90 compounds representing the chemical diversity is assessed. We confirm in vitro transmission-blocking activity of four of the six selected molecules belonging to three distinct scaffold clusters. Overall, this TCAMS gametocyte screen provides 276 promising antimalarial molecules with dual asexual/sexual activity, representing starting points for target identification and candidate selection. There is a need for Plasmodium transmission blocking drugs for malaria elimination. Here, Miguel-Blanco et al. screen >10,000 compounds against stage V female gametocytes, identify active compounds belonging to 57 chemotypes and confirm transmission blocking activity of four selected compounds in vitro.
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54
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Gebru T, Ajua A, Theisen M, Esen M, Ngoa UA, Issifou S, Adegnika AA, Kremsner PG, Mordmüller B, Held J. Recognition of Plasmodium falciparum mature gametocyte-infected erythrocytes by antibodies of semi-immune adults and malaria-exposed children from Gabon. Malar J 2017; 16:176. [PMID: 28446190 PMCID: PMC5406886 DOI: 10.1186/s12936-017-1827-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/10/2017] [Accepted: 04/19/2017] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Transmission of malaria from man to mosquito depends on the presence of gametocytes, the sexual stage of Plasmodium parasites in the infected host. Naturally acquired antibodies against gametocytes exist and may play a role in controlling transmission by limiting the gametocyte development in the circulation or by interrupting gamete development and fertilization in the mosquito following ingestion. So far, most studies on antibody responses to sexual stage antigens have focused on a subset of gametocyte-surface antigens, even though inhibitory Ab responses to other gametocyte antigens might also play a role in controlling gametocyte density and fertility. Limited information is available on natural antibody response to the surfaces of gametocyte-infected erythrocytes. METHODS Ab responses to surface antigens of erythrocytes infected by in vitro differentiated Plasmodium falciparum mature gametocytes were investigated in sera of semi-immune adults and malaria-exposed children. In addition, the effect of immunization with GMZ2, a blood stage malaria vaccine candidate, and the effect of intestinal helminth infection on the development of immunity to gametocytes of P. falciparum was evaluated in malaria-exposed children and adults from Gabon. Serum samples from two Phase I clinical trials conducted in Gabon were analysed by microscopic and flow-cytometric immunofluorescence assay. RESULTS Adults had a higher Ab response compared to children. Ab reactivity was significantly higher after fixation and permeabilization of parasitized erythrocytes. Following vaccination with the malaria vaccine candidate GMZ2, anti-gametocyte Ab concentration decreased in adults compared to baseline. Ab response to whole asexual stage antigens had a significant but weak positive correlation to anti-gametocyte Ab responses in adults, but not in children. Children infected with Ascaris lumbricoides had a significantly higher anti-gametocyte Ab response compared to non-infected children. CONCLUSION The current data suggest that antigens exposed on the gametocyte-infected red blood cells are recognized by serum antibodies from malaria-exposed children and semi-immune adults. This anti-gametocyte immune response may be influenced by natural exposure and vaccination. Modulation of the natural immune response to gametocytes by co-infecting parasites should be investigated further and may have an important impact on malaria control strategies.
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Affiliation(s)
- Tamirat Gebru
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.,Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon.,German Centre for Infection Research (DZIF), Partner Site Lambaréné, Gabon.,Department of Medical Laboratory Sciences, College of Medical and Health Sciences, Haramaya University, Harar, Ethiopia
| | - Anthony Ajua
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany
| | - Michael Theisen
- Department for Congenital Disorders, Statens Serum Institut, Copenhagen, Denmark.,Center for Medical Parasitology at Department of International Health, Immunology and Microbiology, University of Copenhagen, Copenhagen, Denmark
| | - Meral Esen
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.,Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon.,German Centre for Infection Research (DZIF), Partner Site Lambaréné, Gabon
| | - Ulysse Ateba Ngoa
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.,Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon.,German Centre for Infection Research (DZIF), Partner Site Lambaréné, Gabon.,Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Saadou Issifou
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.,Fondation pour la Recherche Scientifique (FORS), Cotonou, Benin
| | - Ayola A Adegnika
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.,Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon.,German Centre for Infection Research (DZIF), Partner Site Lambaréné, Gabon.,Department of Parasitology, Leiden University Medical Center, Leiden, The Netherlands
| | - Peter G Kremsner
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.,Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon.,German Centre for Infection Research (DZIF), Partner Site Lambaréné, Gabon
| | - Benjamin Mordmüller
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany.,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany.,Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon.,German Centre for Infection Research (DZIF), Partner Site Lambaréné, Gabon
| | - Jana Held
- Institute of Tropical Medicine, University of Tübingen, Wilhelmstraße 27, 72074, Tübingen, Germany. .,German Centre for Infection Research (DZIF), Partner Site Tübingen, Germany. .,Centre de Recherches Médicales de Lambaréné (CERMEL), Lambaréné, Gabon. .,German Centre for Infection Research (DZIF), Partner Site Lambaréné, Gabon.
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The need to compare: assessing the level of agreement of three high-throughput assays against Plasmodium falciparum mature gametocytes. Sci Rep 2017; 7:45992. [PMID: 28378767 PMCID: PMC5380998 DOI: 10.1038/srep45992] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/22/2016] [Accepted: 03/07/2017] [Indexed: 12/22/2022] Open
Abstract
Whole-cell High-Throughput Screening (HTS) is a key tool for the discovery of much needed malaria transmission blocking drugs. Discrepancies in the reported outcomes from various HTS Plasmodium falciparum gametocytocidal assays hinder the direct comparison of data and ultimately the interpretation of the transmission blocking potential of hits. To dissect the underlying determinants of such discrepancies and assess the impact that assay-specific factors have on transmission-blocking predictivity, a 39-compound subset from the Medicines for Malaria Venture Malaria Box was tested in parallel against three distinct mature stage gametocytocidal assays, under strictly controlled parasitological, chemical, temporal and analytical conditions resembling the standard membrane feeding assay (SMFA). Apart from a few assay-specific outliers, which highlighted the value of utilizing multiple complementary approaches, good agreement was observed (average ΔpIC50 of 0.12 ± 0.01). Longer compound incubation times improved the ability of the least sensitive assay to detect actives by 2-fold. Finally, combining the number of actives identified by any single assay with those obtained at longer incubation times yielded greatly improved outcomes and agreement with SMFA. Screening compounds using extended incubation times and using multiple in vitro assay technologies are valid approaches for the efficient identification of biologically relevant malaria transmission blocking hits.
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56
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Wong W, Bai XC, Sleebs BE, Triglia T, Brown A, Thompson JK, Jackson KE, Hanssen E, Marapana DS, Fernandez IS, Ralph SA, Cowman AF, Scheres SH, Baum J. Mefloquine targets the Plasmodium falciparum 80S ribosome to inhibit protein synthesis. Nat Microbiol 2017; 2:17031. [PMID: 28288098 PMCID: PMC5439513 DOI: 10.1038/nmicrobiol.2017.31] [Citation(s) in RCA: 97] [Impact Index Per Article: 13.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/21/2016] [Accepted: 02/07/2017] [Indexed: 12/26/2022]
Abstract
Malaria control is heavily dependent on chemotherapeutic agents for disease prevention and drug treatment. Defining the mechanism of action for licensed drugs, for which no target is characterized, is critical to the development of their second-generation derivatives to improve drug potency towards inhibition of their molecular targets. Mefloquine is a widely used antimalarial without a known mode of action. Here, we demonstrate that mefloquine is a protein synthesis inhibitor. We solved a 3.2 Å cryo-electron microscopy structure of the Plasmodium falciparum 80S ribosome with the (+)-mefloquine enantiomer bound to the ribosome GTPase-associated centre. Mutagenesis of mefloquine-binding residues generates parasites with increased resistance, confirming the parasite-killing mechanism. Furthermore, structure-guided derivatives with an altered piperidine group, predicted to improve binding, show enhanced parasiticidal effect. These data reveal one possible mode of action for mefloquine and demonstrate the vast potential of cryo-electron microscopy to guide the development of mefloquine derivatives to inhibit parasite protein synthesis.
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Affiliation(s)
- Wilson Wong
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
| | - Xiao-Chen Bai
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Brad E. Sleebs
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
| | - Tony Triglia
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
| | - Alan Brown
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Jennifer K. Thompson
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
| | - Katherine E. Jackson
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Eric Hanssen
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Danushka S. Marapana
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
| | - Israel S. Fernandez
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Stuart A. Ralph
- Bio21 Molecular Science and Biotechnology Institute, University of Melbourne, Parkville, Victoria 3010, Australia
| | - Alan F. Cowman
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, 3010, Australia
| | - Sjors H.W. Scheres
- MRC Laboratory of Molecular Biology, Cambridge Biomedical Campus, Cambridge CB2 0QH, UK
| | - Jake Baum
- Walter and Eliza Hall Institute of Medical Research, Parkville, Victoria, 3052, Australia
- Department of Medical Biology, University of Melbourne, Parkville, Victoria, 3010, Australia
- Department of Life Sciences, Imperial College London, South Kensington, London, SW7 2AZ, UK
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Abstract
This article attempts to draw together current knowledge on the biology of Plasmodium and experience gained from past control campaigns to interpret and guide current efforts to discover and develop exciting new strategies targeting the parasite with the objective of interrupting transmission. Particular note is made of the advantages of targeting often unappreciated small, yet vital, bottleneck populations to enhance both the impact and the useful lifetime of hard-won interventions. A case is made for the standardization of methods to measure transmission blockade to permit the rational comparison of how diverse interventions (drugs, vaccines, insecticides, Genetically Modified technologies) targeting disparate aspects of parasite biology may impact upon the commonly used parameter of parasite prevalence in the human population.
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Affiliation(s)
- R E Sinden
- The Jenner Institute, Oxford, United Kingdom.
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58
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Metabolomic Profiling of the Malaria Box Reveals Antimalarial Target Pathways. Antimicrob Agents Chemother 2016; 60:6635-6649. [PMID: 27572391 DOI: 10.1128/aac.01224-16] [Citation(s) in RCA: 108] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/10/2016] [Accepted: 08/16/2016] [Indexed: 12/11/2022] Open
Abstract
The threat of widespread drug resistance to frontline antimalarials has renewed the urgency for identifying inexpensive chemotherapeutic compounds that are effective against Plasmodium falciparum, the parasite species responsible for the greatest number of malaria-related deaths worldwide. To aid in the fight against malaria, a recent extensive screening campaign has generated thousands of lead compounds with low micromolar activity against blood stage parasites. A subset of these leads has been compiled by the Medicines for Malaria Venture (MMV) into a collection of structurally diverse compounds known as the MMV Malaria Box. Currently, little is known regarding the activity of these Malaria Box compounds on parasite metabolism during intraerythrocytic development, and a majority of the targets for these drugs have yet to be defined. Here we interrogated the in vitro metabolic effects of 189 drugs (including 169 of the drug-like compounds from the Malaria Box) using ultra-high-performance liquid chromatography-mass spectrometry (UHPLC-MS). The resulting metabolic fingerprints provide information on the parasite biochemical pathways affected by pharmacologic intervention and offer a critical blueprint for selecting and advancing lead compounds as next-generation antimalarial drugs. Our results reveal several major classes of metabolic disruption, which allow us to predict the mode of action (MoA) for many of the Malaria Box compounds. We anticipate that future combination therapies will be greatly informed by these results, allowing for the selection of appropriate drug combinations that simultaneously target multiple metabolic pathways, with the aim of eliminating malaria and forestalling the expansion of drug-resistant parasites in the field.
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Routine in vitro culture of P. falciparum gametocytes to evaluate novel transmission-blocking interventions. Nat Protoc 2016; 11:1668-80. [DOI: 10.1038/nprot.2016.096] [Citation(s) in RCA: 89] [Impact Index Per Article: 11.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022]
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Bahamontes-Rosa N, Gomez-Lorenzo MG, Lelièvre J, Rodriguez Alejandre A, Almela MJ, Lozano S, Herreros E, Gamo FJ. A novel validated assay to support the discovery of new anti-malarial gametocytocidal agents. Malar J 2016; 15:385. [PMID: 27448565 PMCID: PMC4957904 DOI: 10.1186/s12936-016-1429-9] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 07/05/2016] [Indexed: 11/21/2022] Open
Abstract
Background Drugs that kill or inhibit Plasmodium gametocytes in the human host could potentially synergize the impact of other chemotherapeutic interventions by blocking transmission. To develop such agents, reliable methods are needed to study the in vitro activity of compounds against gametocytes. This study describes a novel assay for characterizing the activity of anti-malarial drugs against the later stages of Plasmodium falciparum gametocyte development using real-time PCR (qPCR). Methods Genes previously reported to be transcribed at the different sexual stages of the gametocytogenesis were selected for study and their mRNA expression was measured in a gametocytogenesis course by qPCR. Genes mainly expressed in the later stages of gametocyte development were used as a surrogate measurement of drug activity. To distinguish between cidal and static drug effects, two different experiments were performed in parallel, one with constant drug pressure throughout the experiment (144 h), and another in which the gametocyte cultures were exposed to the compound for only 48 h. Results Four P.falciparum genes coding for proteins Pf77, ROM3, Pfs25, and Pfg377 with transcription specific for late-stage gametocyte development were identified. The in vitro anti-malarial activity of compounds against such gametocytes was assessed by measuring mRNA levels of these genes using qPCR. The assay was validated against standard anti-malarial drugs (epoxomicin, dihydroartemisinin, chloroquine, thiostrepton, and methylene blue) and compounds from the GSK compound library with known anti-gametocyte activity. Conclusions This study describes a novel assay for characterizing the activity of anti-malarial drugs against the later stages of P. falciparum gametocyte development using qPCR in genetically unmodified parasites. The method described is a reliable and user-friendly technique with a medium throughput that could be easily implemented in any laboratory. Electronic supplementary material The online version of this article (doi:10.1186/s12936-016-1429-9) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Noemí Bahamontes-Rosa
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain.
| | - María G Gomez-Lorenzo
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain
| | - Joël Lelièvre
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain
| | - Ane Rodriguez Alejandre
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain
| | - María Jesus Almela
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain
| | - Sonia Lozano
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain
| | - Esperanza Herreros
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain
| | - Francisco-Javier Gamo
- Tres Cantos Medicines Development Campus, Diseases of the Developing World, GlaxoSmithKline, Tres Cantos, 28760, Madrid, Spain
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Birkholtz LM, Coetzer TL, Mancama D, Leroy D, Alano P. Discovering New Transmission-Blocking Antimalarial Compounds: Challenges and Opportunities. Trends Parasitol 2016; 32:669-681. [PMID: 27209388 DOI: 10.1016/j.pt.2016.04.017] [Citation(s) in RCA: 28] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/21/2016] [Revised: 04/24/2016] [Accepted: 04/26/2016] [Indexed: 01/08/2023]
Abstract
The ability to target human-mosquito parasite transmission challenges global malaria elimination. However, it is not obvious what a transmission-blocking drug will look like; should it target only parasite transmission stages; be combined with a partner drug killing the pathogenic asexual stages; or kill both the sexual and asexual blood stages, preferably displaying polypharmacology? The development of transmission-blocking antimalarials requires objective analyses of the current strategies. Here, pertinent issues and questions regarding the target candidate profile of a transmission-blocking compound, and its role in malaria elimination strategies, are highlighted and novel perspectives proposed. The essential role of a test cascade that integrates screening and validation strategies to identify next-generation transmission-blocking antimalarials is emphasised.
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Affiliation(s)
- Lyn-Marie Birkholtz
- Department of Biochemistry, Centre for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa.
| | - Theresa L Coetzer
- Department of Molecular Medicine and Haematology, Wits Research Institute for Malaria, Faculty of Health Sciences, University of the Witwatersrand, National Health Laboratory Service, Johannesburg, South Africa.
| | - Dalu Mancama
- Department of Biochemistry, Centre for Sustainable Malaria Control, Faculty of Natural and Agricultural Sciences, University of Pretoria, Pretoria, South Africa; Biosciences, Council for Scientific and Industrial Research, Pretoria, South Africa.
| | - Didier Leroy
- Medicines for Malaria Venture, Geneva, Switzerland.
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie e Immunomediate, Istituto Superiore di Sanità, Rome, Italy.
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Duffy S, Loganathan S, Holleran JP, Avery VM. Large-scale production of Plasmodium falciparum gametocytes for malaria drug discovery. Nat Protoc 2016; 11:976-92. [PMID: 27123949 DOI: 10.1038/nprot.2016.056] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The tightly controlled induction of Plasmodium falciparum gametocytes in large-scale culture is a fundamental requirement for malaria drug discovery applications including, but not limited to, high-throughput screening. This protocol uses magnetic separation for isolation of hemozoin-containing parasites in order to (i) increase parasitemia, (ii) decrease hematocrit and (iii) introduce higher levels of young red blood cells in a culture simultaneously within 2-4 h. These parameters, along with red blood cell lysis products that are generated through schizont rupture, are highly relevant for enabling optimum induction of gametocytogenesis in vitro. No other previously published protocols have applied this particular approach for parasite isolation and maximization of fresh red blood cells before inducing gametocytogenesis, which is essential for obtaining highly synchronous gametocyte classical stages on a large scale. In summary, 500-1,000 million stage IV gametocytes can be obtained within 16 d from an initial 10 ml of asexual blood-stage culture.
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Affiliation(s)
- Sandra Duffy
- Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
| | - Sasdekumar Loganathan
- Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
| | - John P Holleran
- Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
| | - Vicky M Avery
- Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, Nathan, Queensland, Australia
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63
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Transmission-Blocking Potential of MEFAS, a Hybrid Compound Derived from Artesunate and Mefloquine. Antimicrob Agents Chemother 2016; 60:3145-7. [PMID: 26902763 DOI: 10.1128/aac.02216-15] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Accepted: 02/06/2016] [Indexed: 11/20/2022] Open
Abstract
Most antimalarial drugs target asexual parasites without reducing gametocyte formation or development. Drugs with dual roles, i.e., those that can target both asexual parasites and gametocytes, would improve the control of malaria. In the current study, MEFAS, a hybrid drug derived from mefloquine and artesunate that has been shown to be an active blood schizonticidal drug, was assessed to determine its ability to block the infectivity of Plasmodium falciparum gametocytes. MEFAS was 280 and 15 times more effective than mefloquine alone and artesunate alone, respectively.
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64
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Luciferase-Based, High-Throughput Assay for Screening and Profiling Transmission-Blocking Compounds against Plasmodium falciparum Gametocytes. Antimicrob Agents Chemother 2016; 60:2097-107. [PMID: 26787698 DOI: 10.1128/aac.01949-15] [Citation(s) in RCA: 46] [Impact Index Per Article: 5.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/16/2015] [Accepted: 01/11/2016] [Indexed: 01/11/2023] Open
Abstract
The discovery of new antimalarial drugs able to target both the asexual and gametocyte stages ofPlasmodium falciparumis critical to the success of the malaria eradication campaign. We have developed and validated a robust, rapid, and cost-effective high-throughput reporter gene assay to identify compounds active against late-stage (stage IV and V) gametocytes. The assay, which is suitable for testing compound activity at incubation times up to 72 h, demonstrates excellent quality and reproducibility, with averageZ' values of 0.85 ± 0.01. We used the assay to screen more than 10,000 compounds from three chemically diverse libraries. The screening outcomes highlighted the opportunity to use collections of compounds with known activity against the asexual stages of the parasites as a starting point for gametocytocidal activity detection in order to maximize the chances of identifying gametocytocidal compounds. This assay extends the capabilities of our previously reported luciferase assay, which tested compounds against early-stage gametocytes, and opens possibilities to profile the activities of gametocytocidal compounds over the entire course of gametocytogenesis.
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65
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Gonçalves D, Hunziker P. Transmission-blocking strategies: the roadmap from laboratory bench to the community. Malar J 2016; 15:95. [PMID: 26888537 PMCID: PMC4758146 DOI: 10.1186/s12936-016-1163-3] [Citation(s) in RCA: 35] [Impact Index Per Article: 4.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2015] [Accepted: 02/11/2016] [Indexed: 11/10/2022] Open
Abstract
Malaria remains one of the most prevalent tropical and infectious diseases in the world, with an estimated more than 200 million clinical cases every year. In recent years, the mosquito stages of the parasite life cycle have received renewed attention with some progress being made in the development of transmission-blocking strategies. From gametocytes to late ookinetes, some attractive antigenic targets have been found and tested in order to develop a transmission blocking vaccine, and drugs are being currently screened for gametocytocidal activity, and also some new and less conventional approaches are drawing increased attention, such as genetically modified and fungus-infected mosquitoes that become refractory to Plasmodium infection. In this review some of those strategies focusing on the progress made so far will be summarized, but also, the challenges that come from the translation of early promising benchwork resulting in successful applications in the field. To do this, the available literature will be screened and all the pieces of the puzzle must be combined: from molecular biology to epidemiologic and clinical data.
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Affiliation(s)
- Daniel Gonçalves
- CLINAM Foundation for Nanomedicine, University of Basel, Basel, Switzerland.
| | - Patrick Hunziker
- CLINAM Foundation for Nanomedicine, University of Basel, Basel, Switzerland.
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66
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Fernández-Álvaro E, Hong WD, Nixon GL, O’Neill PM, Calderón F. Antimalarial Chemotherapy: Natural Product Inspired Development of Preclinical and Clinical Candidates with Diverse Mechanisms of Action. J Med Chem 2016; 59:5587-603. [DOI: 10.1021/acs.jmedchem.5b01485] [Citation(s) in RCA: 51] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
Affiliation(s)
- Elena Fernández-Álvaro
- Diseases of the Developing World, Tres
Cantos Medicines Development Campus, GlaxoSmithKline, c/Severo Ochoa, 2, 28760, Tres Cantos, Madrid, Spain
| | - W. David Hong
- Robert Robinson
Laboratories, Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Gemma L. Nixon
- Robert Robinson
Laboratories, Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Paul M. O’Neill
- Robert Robinson
Laboratories, Department of Chemistry, University of Liverpool, Crown Street, Liverpool L69 7ZD, U.K
| | - Félix Calderón
- Diseases of the Developing World, Tres
Cantos Medicines Development Campus, GlaxoSmithKline, c/Severo Ochoa, 2, 28760, Tres Cantos, Madrid, Spain
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67
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Djimde AA, Maiga AW, Ouologuem D, Fofana B, Sagara I, Dembele D, Toure S, Sanogo K, Dama S, Sidibe B, Doumbo OK. Gametocyte clearance dynamics following oral artesunate treatment of uncomplicated falciparum malaria in Malian children. Parasite 2016; 23:3. [PMID: 26839003 PMCID: PMC4738184 DOI: 10.1051/parasite/2016003] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/24/2015] [Accepted: 01/20/2016] [Indexed: 12/16/2022] Open
Abstract
Artemisinin-based combination therapies decrease Plasmodium gametocyte carriage. However, the role of artesunate in monotherapy in vivo, the mechanisms involved, and the utility of gametocyte carriage as a potential tool for the surveillance of antimalarial resistance are poorly understood. In 2010-2011, we conducted an open-label, prospective efficacy study of artesunate as monotherapy in children 1-10 years of age with uncomplicated falciparum malaria in Bougoula-Hameau, Mali. Standard oral doses of artesunate were administered for 7 days and patients were followed up for 28 days. The data were compared to a similar study conducted in 2002-2004. Of 100 children enrolled in the 2010-2011 study, 92 were analyzed and compared to 217 children enrolled in the 2002-2004 study. The proportion of gametocyte carriers was unchanged at the end of treatment (23% at baseline vs. 24% on day 7, p = 1.0) and did not significantly decline until day 21 of follow-up (23% vs. 6%, p = 0.003). The mean gametocyte density at inclusion remained unchanged at the end of treatment (12 gametocytes/μL vs. 16 gametocytes/μL, p = 0.6). Overall, 46% of the 71 initial non-carriers had gametocytes detected by day 7. Similar results were found in the 2002-2004 study. In both studies, although gametocyte carriage significantly decreased by the end of the 28-day follow-up, artesunate did not clear mature gametocytes during treatment and did not prevent the appearance of new stage V gametocytes as assessed by light microscopy. Baseline gametocyte carriage was significantly higher 6 years after the deployment of artemisinin-based combination therapies in this setting.
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Affiliation(s)
- Abdoulaye A. Djimde
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Amelia W. Maiga
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Vanderbilt University Medical Center Nashville TN
37232 USA
| | - Dinkorma Ouologuem
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Bakary Fofana
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Issaka Sagara
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Demba Dembele
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Sekou Toure
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Kassim Sanogo
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Souleymane Dama
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Bakary Sidibe
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
| | - Ogobara K. Doumbo
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Malaria Research and Training Center, Department of Epidemiology of Parasitic Diseases, Faculty of Pharmacy, University of Science, Techniques and Technologies of Bamako P.O. Box 1805 Mali
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68
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Mokgethi-Morule T, N'Da DD. Cell based assays for anti-Plasmodium activity evaluation. Eur J Pharm Sci 2016; 84:26-36. [PMID: 26776968 DOI: 10.1016/j.ejps.2016.01.001] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/10/2015] [Revised: 12/28/2015] [Accepted: 01/02/2016] [Indexed: 10/22/2022]
Abstract
Malaria remains one of the most common and deadly infectious diseases worldwide. The severity of this global public health challenge is reflected by the approximately 198 million people, who were reportedly infected in 2013 and by the more than 584,000 related deaths in that same year. The rising emergence of drug resistance towards the once effective artemisinin combination therapies (ACTs) has become a serious concern and warrants more robust drug development strategies, with the objective of eradicating malaria infections. The intricate biology and life cycle of Plasmodium parasites complicate the understanding of the disease in such a way that would enhance the development of more effective chemotherapies that would achieve radical clinical cure and that would prevent disease relapse. Phenotypic cell based assays have for long been a valuable approach and involve the screening and analysis of diverse compounds with regards to their activities towards whole Plasmodium parasites in vitro. To achieve the Millennium Development Goal (MDG) of malaria eradication by 2020, new generation drugs that are active against all parasite stages (erythrocytic (blood), exo-erythrocytic (liver stages and gametocytes)) are needed. Significant advances are being made in assay development to overcome some of the practical challenges of assessing drug efficacy, particularly in the liver and transmission stage Plasmodium models. This review discusses primary screening models and the fundamental progress being made in whole cell based efficacy screens of anti-malarial activity. Ongoing challenges and some opportunities for improvements in assay development that would assist in the discovery of effective, safe and affordable drugs for malaria treatments are also discussed.
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Affiliation(s)
- Thabang Mokgethi-Morule
- Drug Design, Centre of Excellence for Pharmaceutical Sciences (PHARMACEN), North-West University, Potchefstroom 2520, South Africa
| | - David D N'Da
- Drug Design, Centre of Excellence for Pharmaceutical Sciences (PHARMACEN), North-West University, Potchefstroom 2520, South Africa.
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69
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Plouffe DM, Wree M, Du AY, Meister S, Li F, Patra K, Lubar A, Okitsu SL, Flannery EL, Kato N, Tanaseichuk O, Comer E, Zhou B, Kuhen K, Zhou Y, Leroy D, Schreiber SL, Scherer CA, Vinetz J, Winzeler EA. High-Throughput Assay and Discovery of Small Molecules that Interrupt Malaria Transmission. Cell Host Microbe 2015; 19:114-26. [PMID: 26749441 PMCID: PMC4723716 DOI: 10.1016/j.chom.2015.12.001] [Citation(s) in RCA: 117] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/04/2015] [Revised: 11/13/2015] [Accepted: 12/11/2015] [Indexed: 11/18/2022]
Abstract
Preventing transmission is an important element of malaria control. However, most of the current available methods to assay for malaria transmission blocking are relatively low throughput and cannot be applied to large chemical libraries. We have developed a high-throughput and cost-effective assay, the Saponin-lysis Sexual Stage Assay (SaLSSA), for identifying small molecules with transmission-blocking capacity. SaLSSA analysis of 13,983 unique compounds uncovered that >90% of well-characterized antimalarials, including endoperoxides and 4-aminoquinolines, as well as compounds active against asexual blood stages, lost most of their killing activity when parasites developed into metabolically quiescent stage V gametocytes. On the other hand, we identified compounds with consistent low nanomolar transmission-blocking activity, some of which showed cross-reactivity against asexual blood and liver stages. The data clearly emphasize substantial physiological differences between sexual and asexual parasites and provide a tool and starting points for the discovery and development of transmission-blocking drugs.
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Affiliation(s)
- David M Plouffe
- The Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Drive, San Diego, CA 92121, USA
| | - Melanie Wree
- Division of Pharmacology and Drug Discovery, Department of Pediatrics, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Alan Y Du
- Division of Pharmacology and Drug Discovery, Department of Pediatrics, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Stephan Meister
- Division of Pharmacology and Drug Discovery, Department of Pediatrics, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Fengwu Li
- Division of Infectious Disease, Department of Medicine, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Kailash Patra
- Division of Infectious Disease, Department of Medicine, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Aristea Lubar
- Division of Infectious Disease, Department of Medicine, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Shinji L Okitsu
- Division of Pharmacology and Drug Discovery, Department of Pediatrics, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Erika L Flannery
- Division of Pharmacology and Drug Discovery, Department of Pediatrics, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Nobutaka Kato
- Broad Institute, 415 Main Street, Cambridge MA 02142
| | - Olga Tanaseichuk
- The Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Drive, San Diego, CA 92121, USA
| | - Eamon Comer
- Broad Institute, 415 Main Street, Cambridge MA 02142
| | - Bin Zhou
- The Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Drive, San Diego, CA 92121, USA
| | - Kelli Kuhen
- The Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Drive, San Diego, CA 92121, USA
| | - Yingyao Zhou
- The Genomics Institute of the Novartis Research Foundation, 10675 John J. Hopkins Drive, San Diego, CA 92121, USA
| | - Didier Leroy
- Medicines for Malaria Venture (MMV), PO Box 1826, 20 Route de Pré-Bois, 1215 Geneva 15, Switzerland
| | - Stuart L Schreiber
- Broad Institute, 415 Main Street, Cambridge MA 02142; Department of Chemistry and Chemical Biology, Harvard University, 7 Cambridge Center, Cambridge, MA 02142, USA
| | | | - Joseph Vinetz
- Division of Infectious Disease, Department of Medicine, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA
| | - Elizabeth A Winzeler
- Division of Pharmacology and Drug Discovery, Department of Pediatrics, University of California San Diego School of Medicine, 9500 Gilman Drive, La Jolla, CA 92093, USA.
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70
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A semi-automated luminescence based standard membrane feeding assay identifies novel small molecules that inhibit transmission of malaria parasites by mosquitoes. Sci Rep 2015; 5:18704. [PMID: 26687564 PMCID: PMC4685452 DOI: 10.1038/srep18704] [Citation(s) in RCA: 54] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/21/2015] [Accepted: 11/24/2015] [Indexed: 12/27/2022] Open
Abstract
Current first-line treatments for uncomplicated falciparum malaria rapidly clear the asexual stages of the parasite, but do not fully prevent parasite transmission by mosquitoes. The standard membrane feeding assay (SMFA) is the biological gold standard assessment of transmission reducing activity (TRA), but its throughput is limited by the need to determine mosquito infection status by dissection and microscopy. Here we present a novel dissection-free luminescence based SMFA format using a transgenic Plasmodium falciparum reporter parasite without resistance to known antimalarials and therefore unrestricted in its utility in compound screening. Analyses of sixty-five compounds from the Medicines for Malaria Venture validation and malaria boxes identified 37 compounds with high levels of TRA (>80%); different assay modes allowed discrimination between gametocytocidal and downstream modes of action. Comparison of SMFA data to published assay formats for predicting parasite infectivity indicated that individual in vitro screens show substantial numbers of false negatives. These results highlight the importance of the SMFA in the screening pipeline for transmission reducing compounds and present a rapid and objective method. In addition we present sixteen diverse chemical scaffolds from the malaria box that may serve as a starting point for further discovery and development of malaria transmission blocking drugs.
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71
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Lucantoni L, Silvestrini F, Signore M, Siciliano G, Eldering M, Dechering KJ, Avery VM, Alano P. A simple and predictive phenotypic High Content Imaging assay for Plasmodium falciparum mature gametocytes to identify malaria transmission blocking compounds. Sci Rep 2015; 5:16414. [PMID: 26553647 PMCID: PMC4639769 DOI: 10.1038/srep16414] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2015] [Accepted: 10/14/2015] [Indexed: 11/15/2022] Open
Abstract
Plasmodium falciparum gametocytes, specifically the mature stages, are the only malaria parasite stage in humans transmissible to the mosquito vector. Anti-malarial drugs capable of killing these forms are considered essential for the eradication of malaria and tools allowing the screening of large compound libraries with high predictive power are needed to identify new candidates. As gametocytes are not a replicative stage it is difficult to apply the same drug screening methods used for asexual stages. Here we propose an assay, based on high content imaging, combining “classic” gametocyte viability readout based on gametocyte counts with a functional viability readout, based on gametocyte activation and the discrimination of the typical gamete spherical morphology. This simple and rapid assay has been miniaturized to a 384-well format using acridine orange staining of wild type P. falciparum 3D7A sexual forms, and was validated by screening reference antimalarial drugs and the MMV Malaria Box. The assay demonstrated excellent robustness and ability to identify quality hits with high likelihood of confirmation of transmission reducing activity in subsequent mosquito membrane feeding assays.
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Affiliation(s)
- Leonardo Lucantoni
- Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, 4111 Nathan, Queensland, Australia
| | - Francesco Silvestrini
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Viale Regina Elena n. 299, 00161 Roma, Italy
| | - Michele Signore
- Dipartimento di Ematologia, Oncologia e Medicina Molecolare, Istituto Superiore di Sanità, Viale Regina Elena n. 299, 00161 Roma, Italy
| | - Giulia Siciliano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Viale Regina Elena n. 299, 00161 Roma, Italy
| | - Maarten Eldering
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA Nijmegen, The Netherlands
| | - Koen J Dechering
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA Nijmegen, The Netherlands
| | - Vicky M Avery
- Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, 4111 Nathan, Queensland, Australia
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Viale Regina Elena n. 299, 00161 Roma, Italy
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72
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In Vitro Activities of Primaquine-Schizonticide Combinations on Asexual Blood Stages and Gametocytes of Plasmodium falciparum. Antimicrob Agents Chemother 2015; 59:7650-6. [PMID: 26416869 DOI: 10.1128/aac.01948-15] [Citation(s) in RCA: 21] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2015] [Accepted: 09/23/2015] [Indexed: 12/28/2022] Open
Abstract
Currently, the World Health Organization recommends addition of a 0.25-mg base/kg single dose of primaquine (PQ) to artemisinin combination therapies (ACTs) for Plasmodium falciparum malaria as a gametocytocidal agent for reducing transmission. Here, we investigated the potential interactions of PQ with the long-lasting components of the ACT drugs for eliminating the asexual blood stages and gametocytes of in vitro-cultured P. falciparum strains. Using the SYBR green I assay for asexual parasites and a flow cytometry-based assay for gametocytes, we determined the interactions of PQ with the schizonticides chloroquine, mefloquine, piperaquine, lumefantrine, and naphthoquine. With the sums of fractional inhibitory concentrations and isobolograms, we were able to determine mostly synergistic interactions for the various PQ and schizonticide combinations on the blood stages of P. falciparum laboratory strains. The synergism in inhibiting asexual stages and gametocytes was highly evident with PQ-naphthoquine, whereas synergism was moderate for the PQ-piperaquine, PQ-chloroquine, and PQ-mefloquine combinations. We have detected potentially antagonistic interactions between PQ and lumefantrine under certain drug combination ratios, suggesting that precautions might be needed when PQ is added as the gametocytocide to the artemether-lumefantrine ACT (Coartem).
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73
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Almela MJ, Lozano S, Lelièvre J, Colmenarejo G, Coterón JM, Rodrigues J, Gonzalez C, Herreros E. A New Set of Chemical Starting Points with Plasmodium falciparum Transmission-Blocking Potential for Antimalarial Drug Discovery. PLoS One 2015; 10:e0135139. [PMID: 26317851 PMCID: PMC4552634 DOI: 10.1371/journal.pone.0135139] [Citation(s) in RCA: 42] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/04/2015] [Accepted: 07/17/2015] [Indexed: 11/23/2022] Open
Abstract
The discovery of new antimalarials with transmission blocking activity remains a key issue in efforts to control malaria and eventually eradicate the disease. Recently, high-throughput screening (HTS) assays have been successfully applied to Plasmodium falciparum asexual stages to screen millions of compounds, with the identification of thousands of new active molecules, some of which are already in clinical phases. The same approach has now been applied to identify compounds that are active against P. falciparum gametocytes, the parasite stage responsible for transmission. This study reports screening results for the Tres Cantos Antimalarial Set (TCAMS), of approximately 13,533 molecules, against P. falciparum stage V gametocytes. Secondary confirmation and cytotoxicity assays led to the identification of 98 selective molecules with dual activity against gametocytes and asexual stages. Hit compounds were chemically clustered and analyzed for appropriate physicochemical properties. The TCAMS chemical space around the prioritized hits was also studied. A selection of hit compounds was assessed ex vivo in the standard membrane feeding assay and demonstrated complete block in transmission. As a result of this effort, new chemical structures not connected to previously described antimalarials have been identified. This new set of compounds may serve as starting points for future drug discovery programs as well as tool compounds for identifying new modes of action involved in malaria transmission.
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Affiliation(s)
- Maria Jesus Almela
- GlaxoSmithKline, Tres Cantos Medicines Development Campus-Diseases of the Developing World, Severo Ochoa 2, Tres Cantos, 28760, Madrid, Spain
- Universidad Nacional de Educación a Distancia (UNED), C/ Senda del Rey 11, 28040, Madrid, Spain
| | - Sonia Lozano
- GlaxoSmithKline, Tres Cantos Medicines Development Campus-Diseases of the Developing World, Severo Ochoa 2, Tres Cantos, 28760, Madrid, Spain
| | - Joël Lelièvre
- GlaxoSmithKline, Tres Cantos Medicines Development Campus-Diseases of the Developing World, Severo Ochoa 2, Tres Cantos, 28760, Madrid, Spain
| | - Gonzalo Colmenarejo
- GlaxoSmithKline, Basic Research Center, Computational Chemistry Department, C/ Santiago Grisolía 4, Tres Cantos, 28760, Madrid, Spain
| | - José Miguel Coterón
- GlaxoSmithKline, Tres Cantos Medicines Development Campus-Diseases of the Developing World, Severo Ochoa 2, Tres Cantos, 28760, Madrid, Spain
| | - Janneth Rodrigues
- GlaxoSmithKline, Tres Cantos Medicines Development Campus-Diseases of the Developing World, Severo Ochoa 2, Tres Cantos, 28760, Madrid, Spain
| | - Carolina Gonzalez
- GlaxoSmithKline, Tres Cantos Medicines Development Campus-Diseases of the Developing World, Severo Ochoa 2, Tres Cantos, 28760, Madrid, Spain
| | - Esperanza Herreros
- GlaxoSmithKline, Tres Cantos Medicines Development Campus-Diseases of the Developing World, Severo Ochoa 2, Tres Cantos, 28760, Madrid, Spain
- * E-mail:
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74
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An assay to probe Plasmodium falciparum growth, transmission stage formation and early gametocyte development. Nat Protoc 2015; 10:1131-42. [PMID: 26134953 DOI: 10.1038/nprot.2015.072] [Citation(s) in RCA: 47] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/14/2023]
Abstract
Conversion from asexual proliferation to sexual differentiation initiates the production of the gametocyte, which is the malaria parasite stage required for human-to-mosquito transmission. This protocol describes an assay designed to probe the effect of drugs or other perturbations on asexual replication, sexual conversion and early gametocyte development in the major human malaria parasite Plasmodium falciparum. Synchronized asexually replicating parasites are induced for gametocyte production by the addition of conditioned medium, and they are then exposed to the treatment of interest during sexual commitment or at any subsequent stage of early gametocyte development. Flow cytometry is used to measure asexual proliferation and gametocyte production via DNA dye staining and the gametocyte-specific expression of a fluorescent protein, respectively. This screening approach may be used to identify and evaluate potential transmission-blocking compounds and to further investigate the mechanism of sexual conversion in malaria parasites. The full protocol can be completed in 11 d.
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Duez J, Holleran JP, Ndour PA, Pionneau C, Diakité S, Roussel C, Dussiot M, Amireault P, Avery VM, Buffet PA. Mechanical clearance of red blood cells by the human spleen: Potential therapeutic applications of a biomimetic RBC filtration method. Transfus Clin Biol 2015; 22:151-7. [PMID: 26138907 DOI: 10.1016/j.tracli.2015.05.004] [Citation(s) in RCA: 25] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/11/2015] [Indexed: 01/09/2023]
Abstract
During their lifespan, circulating RBC are frequently checked for their deformability. This mechanical quality control operates essentially in the human spleen. RBC unable to squeeze though narrow splenic slits are retained and cleared from the blood circulation. Under physiological conditions this prevents microvessels from being clogged by senescent, rigid RBC. Retention of poorly deformable RBC is an important determinant of pathogenesis in malaria and may also impact the clinical benefit of transfusion. Modulating the splenic retention of RBC has already been proposed to support therapeutic approaches in these research fields. To this aim, the development of microplates for high throughput filtration of RBC through microsphere layers (microplate-based microsphiltration) has been undertaken. This review focuses on potential therapeutic applications provided by this technology in malaria chemotherapy and transfusion.
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Affiliation(s)
- J Duez
- CIMI-Paris U1135, équipe 4, hôpital La Pitié-Salpêtrière, 75013 Paris, France; Laboratoire d'excellence GR-Ex, 24, boulevard du Montparnasse, 75015, Paris, France; HRA Pharma Laboratoires, 15, rue de Béranger, 75003 Paris, France; Eskitis Institute for Drug Discovery, Griffith University, Brisbane Innovation Park, Don Young Road, Nathan, QLD 4111, Australia
| | - J P Holleran
- Eskitis Institute for Drug Discovery, Griffith University, Brisbane Innovation Park, Don Young Road, Nathan, QLD 4111, Australia
| | - P A Ndour
- CIMI-Paris U1135, équipe 4, hôpital La Pitié-Salpêtrière, 75013 Paris, France; Laboratoire d'excellence GR-Ex, 24, boulevard du Montparnasse, 75015, Paris, France
| | - C Pionneau
- CIMI-Paris Plateforme post-génomique de la Pitié Salpêtrière, P3S, hôpital La Pitié-Salpêtrière, 75013 Paris, France
| | - S Diakité
- CIMI-Paris U1135, équipe 4, hôpital La Pitié-Salpêtrière, 75013 Paris, France; Laboratoire d'excellence GR-Ex, 24, boulevard du Montparnasse, 75015, Paris, France
| | - C Roussel
- Laboratoire d'excellence GR-Ex, 24, boulevard du Montparnasse, 75015, Paris, France; Inserm U1163/CNRS ERL 8254, Imagine Institute, Paris Descartes-Sorbonne Paris Cité University, 75015 Paris, France; Institut national de la transfusion sanguine (INTS), 75015 Paris, France
| | - M Dussiot
- Laboratoire d'excellence GR-Ex, 24, boulevard du Montparnasse, 75015, Paris, France; Inserm U1163/CNRS ERL 8254, Imagine Institute, Paris Descartes-Sorbonne Paris Cité University, 75015 Paris, France; Institut national de la transfusion sanguine (INTS), 75015 Paris, France
| | - P Amireault
- Laboratoire d'excellence GR-Ex, 24, boulevard du Montparnasse, 75015, Paris, France; Inserm U1163/CNRS ERL 8254, Imagine Institute, Paris Descartes-Sorbonne Paris Cité University, 75015 Paris, France; Institut national de la transfusion sanguine (INTS), 75015 Paris, France
| | - V M Avery
- Eskitis Institute for Drug Discovery, Griffith University, Brisbane Innovation Park, Don Young Road, Nathan, QLD 4111, Australia
| | - P A Buffet
- CIMI-Paris U1135, équipe 4, hôpital La Pitié-Salpêtrière, 75013 Paris, France; Laboratoire d'excellence GR-Ex, 24, boulevard du Montparnasse, 75015, Paris, France.
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76
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Reader J, Botha M, Theron A, Lauterbach SB, Rossouw C, Engelbrecht D, Wepener M, Smit A, Leroy D, Mancama D, Coetzer TL, Birkholtz LM. Nowhere to hide: interrogating different metabolic parameters of Plasmodium falciparum gametocytes in a transmission blocking drug discovery pipeline towards malaria elimination. Malar J 2015; 14:213. [PMID: 25994518 PMCID: PMC4449569 DOI: 10.1186/s12936-015-0718-z] [Citation(s) in RCA: 70] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/10/2015] [Accepted: 04/22/2015] [Indexed: 12/23/2022] Open
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. Electronic supplementary material The online version of this article (doi:10.1186/s12936-015-0718-z) contains supplementary material, which is available to authorized users.
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Affiliation(s)
- Janette Reader
- Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa.
| | - Mariëtte Botha
- Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa.
| | - Anjo Theron
- Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria, 0001, South Africa.
| | - Sonja B Lauterbach
- 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.
| | - Claire Rossouw
- Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria, 0001, South Africa.
| | - Dewaldt Engelbrecht
- 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.
| | - Melanie Wepener
- 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.
| | - Annél Smit
- Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa.
| | - Didier Leroy
- Medicines for Malaria Venture, Geneva, Switzerland.
| | - Dalu Mancama
- Biosciences, Council for Scientific and Industrial Research, PO Box 395, Pretoria, 0001, South Africa.
| | - Theresa L Coetzer
- 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.
| | - Lyn-Marie Birkholtz
- Malaria Parasite Molecular Laboratory, Centre for Sustainable Malaria Control, Department of Biochemistry, University of Pretoria, Private Bag x20, Hatfield, Pretoria, 0028, South Africa.
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Keurulainen L, Vahermo M, Puente-Felipe M, Sandoval-Izquierdo E, Crespo-Fernández B, Guijarro-López L, Huertas-Valentín L, de las Heras-Dueña L, Leino TO, Siiskonen A, Ballell-Pages L, Sanz LM, Castañeda-Casado P, Jiménez-Díaz MB, Martínez-Martínez MS, Viera S, Kiuru P, Calderón F, Yli-Kauhaluoma J. A Developability-Focused Optimization Approach Allows Identification of in Vivo Fast-Acting Antimalarials: N-[3-[(Benzimidazol-2-yl)amino]propyl]amides. J Med Chem 2015; 58:4573-80. [DOI: 10.1021/acs.jmedchem.5b00114] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023]
Affiliation(s)
- Leena Keurulainen
- Faculty
of Pharmacy, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Viikinkaari 5 E (P.O. Box 56), FI-00014 Helsinki, Finland
| | - Mikko Vahermo
- Faculty
of Pharmacy, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Viikinkaari 5 E (P.O. Box 56), FI-00014 Helsinki, Finland
| | - Margarita Puente-Felipe
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Elena Sandoval-Izquierdo
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Benigno Crespo-Fernández
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Laura Guijarro-López
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Leticia Huertas-Valentín
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Laura de las Heras-Dueña
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Teppo O. Leino
- Faculty
of Pharmacy, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Viikinkaari 5 E (P.O. Box 56), FI-00014 Helsinki, Finland
| | - Antti Siiskonen
- Faculty
of Pharmacy, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Viikinkaari 5 E (P.O. Box 56), FI-00014 Helsinki, Finland
| | - Lluís Ballell-Pages
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Laura M. Sanz
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Pablo Castañeda-Casado
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - M. Belén Jiménez-Díaz
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - María S. Martínez-Martínez
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Sara Viera
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Paula Kiuru
- Faculty
of Pharmacy, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Viikinkaari 5 E (P.O. Box 56), FI-00014 Helsinki, Finland
| | - Félix Calderón
- Tres
Cantos Medicines Development Campus, GlaxoSmithKline, Severo Ochoa 2, Tres Cantos, Madrid 28760, Spain
| | - Jari Yli-Kauhaluoma
- Faculty
of Pharmacy, Division of Pharmaceutical Chemistry and Technology, University of Helsinki, Viikinkaari 5 E (P.O. Box 56), FI-00014 Helsinki, Finland
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Splenic retention of Plasmodium falciparum gametocytes to block the transmission of malaria. Antimicrob Agents Chemother 2015; 59:4206-14. [PMID: 25941228 DOI: 10.1128/aac.05030-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2014] [Accepted: 04/29/2015] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum is transmitted from humans to Anopheles mosquito vectors via the sexual erythrocytic forms termed gametocytes. Erythrocyte filtration through microsphere layers (microsphiltration) had shown that circulating gametocytes are deformable. Compounds reducing gametocyte deformability would induce their splenic clearance, thus removing them from the blood circulation and blocking malaria transmission. The hand-made, single-sample prototype for microsphiltration was miniaturized to a 96-well microtiter plate format, and gametocyte retention in the microsphere filters was quantified by high-content imaging. The stiffening activity of 40 pharmacological compounds was assessed in microtiter plates, using a small molecule (calyculin) as a positive control. The stiffening activity of calyculin was assessed in spleen-mimetic microfluidic chips and in macrophage-depleted mice. Marked mechanical retention (80% to 90%) of mature gametocytes was obtained in microplates following exposure to calyculin at concentrations with no effect on parasite viability. Of the 40 compounds tested, including 20 antimalarials, only 5 endoperoxides significantly increased gametocyte retention (1.5- to 2.5-fold; 24 h of exposure at 1 μM). Mature gametocytes exposed to calyculin accumulated in microfluidic chips and were cleared from the circulation of macrophage-depleted mice as rapidly as heat-stiffened erythrocytes, thus confirming results obtained using the microsphiltration assay. An automated miniaturized approach to select compounds for their gametocyte-stiffening effect has been established. Stiffening induces gametocyte clearance both in vitro and in vivo. Based on physiologically validated tools, this screening cascade can identify novel compounds and uncover new targets to block malaria transmission. Innovative applications in hematology are also envisioned.
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79
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Kumar S, Kumari R, Pandey R. New insight-guided approaches to detect, cure, prevent and eliminate malaria. PROTOPLASMA 2015; 252:717-753. [PMID: 25323622 DOI: 10.1007/s00709-014-0697-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/18/2014] [Accepted: 09/01/2014] [Indexed: 06/04/2023]
Abstract
New challenges posed by the development of resistance against artemisinin-based combination therapies (ACTs) as well as previous first-line therapies, and the continuing absence of vaccine, have given impetus to research in all areas of malaria control. This review portrays the ongoing progress in several directions of malaria research. The variants of RTS,S and apical membrane antigen 1 (AMA1) are being developed and test adapted as multicomponent and multistage malaria control vaccines, while many other vaccine candidates and methodologies to produce antigens are under experimentation. To track and prevent the spread of artemisinin resistance from Southeast Asia to other parts of the world, rolling circle-enhanced enzyme activity detection (REEAD), a time- and cost-effective malaria diagnosis in field conditions, and a DNA marker associated with artemisinin resistance have become available. Novel mosquito repellents and mosquito trapping and killing techniques much more effective than the prevalent ones are undergoing field testing. Mosquito lines stably infected with their symbiotic wild-type or genetically engineered bacteria that kill sympatric malaria parasites are being constructed and field tested for stopping malaria transmission. A complementary approach being pursued is the addition of ivermectin-like drug molecules to ACTs to cure malaria and kill mosquitoes. Experiments are in progress to eradicate malaria mosquito by making it genetically male sterile. High-throughput screening procedures are being developed and used to discover molecules that possess long in vivo half life and are active against liver and blood stages for the fast cure of malaria symptoms caused by simple or relapsing and drug-sensitive and drug-resistant types of varied malaria parasites, can stop gametocytogenesis and sporogony and could be given in one dose. Target-based antimalarial drug designing has begun. Some of the putative next-generation antimalarials that possess in their scaffold structure several of the desired properties of malaria cure and control are exemplified by OZ439, NITD609, ELQ300 and tafenoquine that are already undergoing clinical trials, and decoquinate, usnic acid, torin-2, ferroquine, WEHI-916, MMV396749 and benzothiophene-type N-myristoyltransferase (NMT) inhibitors, which are candidates for future clinical usage. Among these, NITD609, ELQ300, decoquinate, usnic acid, torin-2 and NMT inhibitors not only cure simple malaria and are prophylactic against simple malaria, but they also cure relapsing malaria.
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Affiliation(s)
- Sushil Kumar
- SKA Institution for Research, Education and Development (SKAIRED), 4/11 SarvPriya Vihar, New Delhi, 110016, India,
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Imaging-based high-throughput screening assay to identify new molecules with transmission-blocking potential against Plasmodium falciparum female gamete formation. Antimicrob Agents Chemother 2015; 59:3298-305. [PMID: 25801574 DOI: 10.1128/aac.04684-14] [Citation(s) in RCA: 41] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/31/2014] [Accepted: 03/16/2015] [Indexed: 11/20/2022] Open
Abstract
In response to a call for the global eradication of malaria, drug discovery has recently been extended to identify compounds that prevent the onward transmission of the parasite, which is mediated by Plasmodium falciparum stage V gametocytes. Lately, metabolic activity has been used in vitro as a surrogate for gametocyte viability; however, as gametocytes remain relatively quiescent at this stage, their ability to undergo onward development (gamete formation) may be a better measure of their functional viability. During gamete formation, female gametocytes undergo profound morphological changes and express translationally repressed mRNA. By assessing female gamete cell surface expression of one such repressed protein, Pfs25, as the readout for female gametocyte functional viability, we developed an imaging-based high-throughput screening (HTS) assay to identify transmission-blocking compounds. This assay, designated the P. falciparum female gametocyte activation assay (FGAA), was scaled up to a high-throughput format (Z' factor, 0.7 ± 0.1) and subsequently validated using a selection of 50 known antimalarials from diverse chemical families. Only a few of these agents showed submicromolar 50% inhibitory concentrations in the assay: thiostrepton, methylene blue, and some endoperoxides. To determine the best conditions for HTS, a robustness test was performed with a selection of the GlaxoSmithKline Tres Cantos Antimalarial Set (TCAMS) and the final screening conditions for this library were determined to be a 2 μM concentration and 48 h of incubation with gametocytes. The P. falciparum FGAA has been proven to be a robust HTS assay faithful to Plasmodium transmission-stage cell biology, and it is an innovative useful tool for antimalarial drug discovery which aims to identify new molecules with transmission-blocking potential.
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81
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Bolscher JM, Koolen KMJ, van Gemert GJ, van de Vegte-Bolmer MG, Bousema T, Leroy D, Sauerwein RW, Dechering KJ. A combination of new screening assays for prioritization of transmission-blocking antimalarials reveals distinct dynamics of marketed and experimental drugs. J Antimicrob Chemother 2015; 70:1357-66. [PMID: 25667405 DOI: 10.1093/jac/dkv003] [Citation(s) in RCA: 45] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2014] [Accepted: 12/29/2014] [Indexed: 12/23/2022] Open
Abstract
OBJECTIVES The development of drugs to reduce malaria transmission is an important part of malaria eradication plans. We set out to develop and validate a combination of new screening assays for prioritization of transmission-blocking molecules. METHODS We developed high-throughput assays for screening compounds against gametocytes, the parasite stages responsible for onward transmission to mosquitoes. An existing gametocyte parasitic lactate dehydrogenase (pLDH) assay was adapted for use in 384-well plates, and a novel homogeneous immunoassay to monitor the functional transition of female gametocytes into gametes was developed. A collection of 48 marketed and experimental antimalarials was screened and subsequently tested for impact on sporogony in Anopheles mosquitoes, to directly quantify the transmission-blocking properties of antimalarials in relation to their effects on gametocyte pLDH activity or gametogenesis. RESULTS AND CONCLUSIONS The novel screening assays revealed distinct stage-specific kinetics and dynamics of drug effects. Peroxides showed the most potent transmission-blocking effects, with an intermediate speed of action and IC50 values that were 20-40-fold higher than the IC50s against the asexual stages causing clinical malaria. Finally, the novel synthetic peroxide OZ439 appeared to be a promising drug candidate as it exerted gametocytocidal and transmission-blocking effects at clinically relevant concentrations.
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Affiliation(s)
- J M Bolscher
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands
| | - K M J Koolen
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands
| | - G J van Gemert
- Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | | | - T Bousema
- Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - D Leroy
- Medicines for Malaria Venture, Route de Pré-Bois 20, 1215 Geneva 15, Switzerland
| | - R W Sauerwein
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands Radboud University Nijmegen Medical Center, PO Box 9101, 6500 HB Nijmegen, The Netherlands
| | - K J Dechering
- TropIQ Health Sciences, Geert Grooteplein 28, huispost 268, 6525 GA, Nijmegen, The Netherlands
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Upton LM, Brock PM, Churcher TS, Ghani AC, Gething PW, Delves MJ, Sala KA, Leroy D, Sinden RE, Blagborough AM. Lead clinical and preclinical antimalarial drugs can significantly reduce sporozoite transmission to vertebrate populations. Antimicrob Agents Chemother 2015; 59:490-7. [PMID: 25385107 PMCID: PMC4291391 DOI: 10.1128/aac.03942-14] [Citation(s) in RCA: 19] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/23/2014] [Accepted: 10/31/2014] [Indexed: 02/01/2023] Open
Abstract
To achieve malarial elimination, we must employ interventions that reduce the exposure of human populations to infectious mosquitoes. To this end, numerous antimalarial drugs are under assessment in a variety of transmission-blocking assays which fail to measure the single crucial criteria of a successful intervention, namely impact on case incidence within a vertebrate population (reduction in reproductive number/effect size). Consequently, any reduction in new infections due to drug treatment (and how this may be influenced by differing transmission settings) is not currently examined, limiting the translation of any findings. We describe the use of a laboratory population model to assess how individual antimalarial drugs can impact the number of secondary Plasmodium berghei infections over a cycle of transmission. We examine the impact of multiple clinical and preclinical drugs on both insect and vertebrate populations at multiple transmission settings. Both primaquine (>6 mg/kg of body weight) and NITD609 (8.1 mg/kg) have significant impacts across multiple transmission settings, but artemether and lumefantrine (57 and 11.8 mg/kg), OZ439 (6.5 mg/kg), and primaquine (<1.25 mg/kg) demonstrated potent efficacy only at lower-transmission settings. While directly demonstrating the impact of antimalarial drug treatment on vertebrate populations, we additionally calculate effect size for each treatment, allowing for head-to-head comparison of the potential impact of individual drugs within epidemiologically relevant settings, supporting their usage within elimination campaigns.
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Affiliation(s)
- L M Upton
- Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - P M Brock
- Department of Infectious Disease Epidemiology, Imperial College London, St. Mary's Campus, London, United Kingdom
| | - T S Churcher
- Department of Infectious Disease Epidemiology, Imperial College London, St. Mary's Campus, London, United Kingdom
| | - A C Ghani
- Department of Infectious Disease Epidemiology, Imperial College London, St. Mary's Campus, London, United Kingdom
| | - P W Gething
- Spatial Ecology and Epidemiology Group, Department of Zoology, University of Oxford, Oxford, United Kingdom
| | - M J Delves
- Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - K A Sala
- Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
| | - D Leroy
- Medicines for Malaria Venture, Geneva, Switzerland
| | - R E Sinden
- Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom Jenner Institute, the University of Oxford, Oxford, United Kingdom
| | - A M Blagborough
- Department of Life Sciences, Imperial College London, South Kensington, London, United Kingdom
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83
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Isoprenoid precursor biosynthesis is the essential metabolic role of the apicoplast during gametocytogenesis in Plasmodium falciparum. EUKARYOTIC CELL 2014; 14:128-39. [PMID: 25446055 DOI: 10.1128/ec.00198-14] [Citation(s) in RCA: 33] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
The malaria parasite harbors a relict plastid called the apicoplast and its discovery opened a new avenue for drug discovery and development due to its unusual, nonmammalian metabolism. The apicoplast is essential during the asexual intraerythrocytic and hepatic stages of the parasite, and there is strong evidence supporting its essential metabolic role during the mosquito stages of the parasite. Supply of the isoprenoid building blocks isopentenyl diphosphate (IPP) and dimethylallyl diphosphate (DMAPP) is the essential metabolic function of the apicoplast during the asexual intraerythrocytic stages. However, the metabolic role of the apicoplast during gametocyte development, the malaria stages transmitted to the mosquito, remains unknown. In this study, we showed that production of IPP for isoprenoid biosynthesis is the essential metabolic function of the apicoplast during gametocytogenesis, by obtaining normal gametocytes lacking the apicoplast when supplemented with IPP. When IPP supplementation was removed early in gametocytogenesis, developmental defects were observed, supporting the essential role of isoprenoids for normal gametocytogenesis. Furthermore, mosquitoes infected with gametocytes lacking the apicoplast developed fewer and smaller oocysts that failed to produce sporozoites. This finding further supports the essential role of the apicoplast in establishing a successful infection in the mosquito vector. Our study supports isoprenoid biosynthesis as a valid drug target for development of malaria transmission-blocking inhibitors.
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84
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Effect of fluorescent dyes on in vitro-differentiated, late-stage Plasmodium falciparum gametocytes. Antimicrob Agents Chemother 2014; 58:7398-404. [PMID: 25267675 DOI: 10.1128/aac.03772-14] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022] Open
Abstract
Plasmodium falciparum gametocytes are not associated with clinical symptoms, but they are responsible for transmitting the pathogen to mosquitoes. Therefore, gametocytocidal interventions are important for malaria control and resistance containment. Currently available drugs and vaccines are not well suited for that purpose. Several dyes have potent antimicrobial activity, but their use against gametocytes has not been investigated systematically. The gametocytocidal activity of nine synthetic dyes and four control compounds was tested against stage V gametocytes of the laboratory strain 3D7 and three clinical isolates of P. falciparum with a bioluminescence assay. Five of the fluorescent dyes had submicromolar 50% inhibitory concentration (IC50) values against mature gametocytes. Three mitochondrial dyes, MitoRed, dihexyloxacarbocyanine iodide (DiOC6), and rhodamine B, were highly active (IC(50)s < 200 nM). MitoRed showed the highest activity against gametocytes, with IC(50)s of 70 nM against 3D7 and 120 to 210 nM against clinical isolates. All compounds were more active against the laboratory strain 3D7 than against clinical isolates. In particular, the endoperoxides artesunate and dihydroartemisinin showed a 10-fold higher activity against 3D7 than against clinical isolates. In contrast to all clinically used antimalarials, several fluorescent dyes had surprisingly high in vitro activity against late-stage gametocytes. Since they also act against asexual blood stages, they shall be considered starting points for the development of new antimalarial lead compounds.
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85
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A male and female gametocyte functional viability assay to identify biologically relevant malaria transmission-blocking drugs. Antimicrob Agents Chemother 2014; 58:7292-302. [PMID: 25267664 DOI: 10.1128/aac.03666-14] [Citation(s) in RCA: 98] [Impact Index Per Article: 9.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/29/2023] Open
Abstract
Malaria elimination will require interventions that prevent parasite transmission from the human host to the mosquito. Experimentally, this is usually determined by the expensive and laborious Plasmodium falciparum standard membrane feeding assay (PfSMFA), which has limited utility for high-throughput drug screening. In response, we developed the P. falciparum dual gamete formation assay (PfDGFA), which faithfully simulates the initial stages of the PfSMFA in vitro. It utilizes a dual readout that individually and simultaneously reports on the functional viability of male and female mature stage V gametocytes. To validate, we screen the Medicines for Malaria Venture (MMV) Malaria Box library with the PfDGFA. Unique to this assay, we find compounds that target male gametocytes only and also compounds with reversible and irreversible activity. Most importantly, we show that compound activity in the PfDGFA accurately predicts activity in PfSMFAs, which validates and supports its adoption into the transmission-stage screening pipeline.
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86
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Strategic use of antimalarial drugs that block falciparum malaria parasite transmission to mosquitoes to achieve local malaria elimination. Parasitol Res 2014; 113:3535-46. [PMID: 25185662 DOI: 10.1007/s00436-014-4091-6] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/28/2014] [Accepted: 08/25/2014] [Indexed: 01/03/2023]
Abstract
The ultimate aim of malaria chemotherapy is not only to treat symptomatic infection but also to reduce transmission potential. With the absence of clinically proven vaccines, drug-mediated blocking of malaria transmission gains growing interest in the research agenda for malaria control and elimination. In addition to the limited arsenal of antimalarials available, the situation is further complicated by the fact that most commonly used antimalarials are being extensively resisted by the parasite and do not assist in blocking its transmission to vectors. Most antimalarials do not exhibit gametocytocidal and/ or sporontocidal activity against the sexual stages of Plasmodium falciparum but may even enhance gametocytogenesis and gametocyte transmissibility. Artemisinin derivatives and 8-aminoquinolines are useful transmission-blocking antimalarials whose optimal actions are on different stages of gametocytes. Transmission control interventions that include gametocytocides covering the spectrum of gametocyte development should be used to reduce and, if possible, stop transmission and infectivity of gametocytes to mosquitoes. Potent gametocytocidal drugs could also help deter the spread of antimalarial drug resistance. Novel proof-of-concept compounds with gametocytocidal activity, such as trioxaquines, synthetic endoperoxides, and spiroindolone, should be further tested for possible clinical utility before investigating the possibility of integrating them in transmission-reducing interventions. Strategic use of potent gametocytocides at appropriate timing with artemisinin-based combination therapies should be given attention, at least, in the short run. This review highlights the role that antimalarials could play in blocking gametocyte transmission and infectivity to mosquitoes and, hence, in reducing the potential of falciparum malaria transmissibility and drug resistance spread.
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87
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Sanders NG, Sullivan DJ, Mlambo G, Dimopoulos G, Tripathi AK. Gametocytocidal screen identifies novel chemical classes with Plasmodium falciparum transmission blocking activity. PLoS One 2014; 9:e105817. [PMID: 25157792 PMCID: PMC4144897 DOI: 10.1371/journal.pone.0105817] [Citation(s) in RCA: 43] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/03/2014] [Accepted: 07/28/2014] [Indexed: 12/24/2022] Open
Abstract
Discovery of transmission blocking compounds is an important intervention strategy necessary to eliminate and eradicate malaria. To date only a small number of drugs that inhibit gametocyte development and thereby transmission from the mosquito to the human host exist. This limitation is largely due to a lack of screening assays easily adaptable to high throughput because of multiple incubation steps or the requirement for high gametocytemia. Here we report the discovery of new compounds with gametocytocidal activity using a simple and robust SYBR Green I- based DNA assay. Our assay utilizes the exflagellation step in male gametocytes and a background suppressor, which masks the staining of dead cells to achieve healthy signal to noise ratio by increasing signal of viable parasites and subtracting signal from dead parasites. By determining the contribution of exflagellation to fluorescent signal and using appropriate cutoff values, we were able to screen for gametocytocidal compounds. After assay validation and optimization, we screened an FDA approved drug library of approximately 1500 compounds, as well as the 400 compound MMV malaria box and identified 44 gametocytocidal compounds with sub to low micromolar IC50s. Major classes of compounds with gametocytocidal activity included quaternary ammonium compounds with structural similarity to choline, acridine-like compounds similar to quinacrine and pyronaridine, as well as antidepressant, antineoplastic, and anthelminthic compounds. Top drug candidates showed near complete transmission blocking in membrane feeding assays. This assay is simple, reproducible and demonstrated robust Z-factor values at low gametocytemia levels, making it amenable to HTS for identification of novel and potent gametocytocidal compounds.
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Affiliation(s)
- Natalie G. Sanders
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - David J. Sullivan
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Godfree Mlambo
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - George Dimopoulos
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
| | - Abhai K. Tripathi
- W. Harry Feinstone Department of Molecular Microbiology and Immunology, Johns Hopkins Bloomberg School of Public Health, Johns Hopkins University, Baltimore, Maryland, United States of America
- * E-mail:
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88
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Cevenini L, Camarda G, Michelini E, Siciliano G, Calabretta MM, Bona R, Kumar TRS, Cara A, Branchini BR, Fidock DA, Roda A, Alano P. Multicolor bioluminescence boosts malaria research: quantitative dual-color assay and single-cell imaging in Plasmodium falciparum parasites. Anal Chem 2014; 86:8814-21. [PMID: 25102353 PMCID: PMC4151787 DOI: 10.1021/ac502098w] [Citation(s) in RCA: 49] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
![]()
New
reliable and cost-effective antimalarial drug screening assays
are urgently needed to identify drugs acting on different stages of
the parasite Plasmodium falciparum,
and particularly those responsible for human-to-mosquito transmission,
that is, the P. falciparum gametocytes.
Low Z′ factors, narrow dynamic ranges, and/or
extended assay times are commonly reported in current gametocyte assays
measuring gametocyte-expressed fluorescent or luciferase reporters,
endogenous ATP levels, activity of gametocyte enzymes, or redox-dependent
dye fluorescence. We hereby report on a dual-luciferase gametocyte
assay with immature and mature P. falciparum gametocyte stages expressing red and green-emitting luciferases
from Pyrophorus plagiophthalamus under
the control of the parasite sexual stage-specific pfs16 gene promoter. The assay was validated with reference antimalarial
drugs and allowed to quantitatively and simultaneously measure stage-specific
drug effects on parasites at different developmental stages. The optimized
assay, requiring only 48 h incubation with drugs and using a cost-effective
luminogenic substrate, significantly reduces assay cost and time in
comparison to state-of-the-art analogous assays. The assay had a Z′ factor of 0.71 ± 0.03, and it is suitable
for implementation in 96- and 384-well microplate formats. Moreover,
the use of a nonlysing d-luciferin substrate significantly
improved the reliability of the assay and allowed one to perform,
for the first time, P. falciparum bioluminescence
imaging at single-cell level.
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Affiliation(s)
- Luca Cevenini
- INBB, Istituto Nazionale di Biostrutture e Biosistemi , 00136 Rome, Italy
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89
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Leroy D, Campo B, Ding XC, Burrows JN, Cherbuin S. Defining the biology component of the drug discovery strategy for malaria eradication. Trends Parasitol 2014; 30:478-90. [PMID: 25131411 DOI: 10.1016/j.pt.2014.07.004] [Citation(s) in RCA: 34] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/16/2014] [Revised: 07/14/2014] [Accepted: 07/15/2014] [Indexed: 10/24/2022]
Abstract
Malaria is still considered a deadly scourge in Africa, Asia, and South America despite improved vector control and curative treatments with new antimalarial combinations. The next challenge is to work towards disease eradication. To achieve this goal it is crucial to develop, validate, and integrate biological assays into test cascades that align with the key target product profiles. For anti-relapse, a parent molecule should kill hypnozoites or cause activation of Plasmodium vivax liver stages. For transmission blocking, dual equal-activity antimalarials killing both the asexual and the sexual parasite stages in human blood are favored. Finally, by assessing cross resistance and generating drug resistance in the laboratory, it is expected that new medicines with acceptable resistance profiles will be forthcoming.
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Affiliation(s)
- Didier Leroy
- Medicines for Malaria Venture (MMV), PO Box 1826, 20 route de Pré-Bois, 1215 Geneva 15, Switzerland.
| | - Brice Campo
- Medicines for Malaria Venture (MMV), PO Box 1826, 20 route de Pré-Bois, 1215 Geneva 15, Switzerland
| | - Xavier C Ding
- Medicines for Malaria Venture (MMV), PO Box 1826, 20 route de Pré-Bois, 1215 Geneva 15, Switzerland
| | - Jeremy N Burrows
- Medicines for Malaria Venture (MMV), PO Box 1826, 20 route de Pré-Bois, 1215 Geneva 15, Switzerland
| | - Stéphanie Cherbuin
- Medicines for Malaria Venture (MMV), PO Box 1826, 20 route de Pré-Bois, 1215 Geneva 15, Switzerland
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90
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Antimalarial activity of the myxobacterial macrolide chlorotonil a. Antimicrob Agents Chemother 2014; 58:6378-84. [PMID: 25114138 DOI: 10.1128/aac.03326-14] [Citation(s) in RCA: 45] [Impact Index Per Article: 4.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Myxobacteria are Gram-negative soil-dwelling bacteria belonging to the phylum Proteobacteria. They are a rich source of promising compounds for clinical application, such as epothilones for cancer therapy and several new antibiotics. In the course of a bioactivity screening program of secondary metabolites produced by Sorangium cellulosum strains, the macrolide chlorotonil A was found to exhibit promising antimalarial activity. Subsequently, we evaluated chlorotonil A against Plasmodium falciparum laboratory strains and clinical isolates from Gabon. Chlorotonil A was highly active, with a 50% inhibitory concentration between 4 and 32 nM; additionally, no correlations between the activities of chlorotonil A and artesunate (rho, 0.208) or chloroquine (rho, -0.046) were observed. Per os treatment of Plasmodium berghei-infected mice with four doses of as little as 36 mg of chlorotonil A per kg of body weight led to the suppression of parasitemia with no obvious signs of toxicity. Chlorotonil A acts against all stages of intraerythrocytic parasite development, including ring-stage parasites and stage IV to V gametocytes, and it requires only a very short exposure to the parasite to exert its antimalarial action. Conclusively, chlorotonil A has an exceptional and unprecedented profile of action and represents an urgently required novel antimalarial chemical scaffold. Therefore, we propose it as a lead structure for further development as an antimalarial chemotherapeutic.
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91
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Wang Z, Liu M, Liang X, Siriwat S, Li X, Chen X, Parker DM, Miao J, Cui L. A flow cytometry-based quantitative drug sensitivity assay for all Plasmodium falciparum gametocyte stages. PLoS One 2014; 9:e93825. [PMID: 24736563 PMCID: PMC3988044 DOI: 10.1371/journal.pone.0093825] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2013] [Accepted: 03/09/2014] [Indexed: 12/16/2022] Open
Abstract
Background Malaria elimination/eradication campaigns emphasize interruption of parasite transmission as a priority strategy. Screening for new drugs and vaccines against gametocytes is therefore urgently needed. However, current methods for sexual stage drug assays, usually performed by counting or via fluorescent markers are either laborious or restricted to a certain stage. Here we describe the use of a transgenic parasite line for assaying drug sensitivity in all gametocyte stages. Methods A transgenic parasite line expressing green fluorescence protein (GFP) under the control of the gametocyte-specific gene α-tubulin II promoter was generated. This parasite line expresses GFP in all gametocyte stages. Using this transgenic line, we developed a flow cytometry-based assay to determine drug sensitivity of all gametocyte stages, and tested the gametocytocidal activities of four antimalarial drugs. Findings This assay proved to be suitable for determining drug sensitivity of all sexual stages and can be automated. A Z’ factor of 0.79±0.02 indicated that this assay could be further optimized for high-throughput screening. The daily sensitivity of gametocytes to three antimalarial drugs (chloroquine, dihydroartemisinin and pyronaridine) showed a drastic decrease from stage III on, whereas it remained relatively steady for primaquine. Conclusions A drug assay was developed to use a single transgenic parasite line for determining drug susceptibility of all gametocyte stages. This assay may be further automated into a high-throughput platform for screening compound libraries against P. falciparum gametocytes.
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Affiliation(s)
- Zenglei Wang
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Min Liu
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- Department of Parasitology, School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, Guangdong, P.R. China
| | - Xiaoying Liang
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Salil Siriwat
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Xiaolian Li
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Xiaoguang Chen
- Department of Parasitology, School of Public Health and Tropical Medicine, Southern Medical University, Guangzhou, Guangdong, P.R. China
| | - Daniel M. Parker
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
| | - Jun Miao
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail: (JM); (LC)
| | - Liwang Cui
- Department of Entomology, Pennsylvania State University, University Park, Pennsylvania, United States of America
- * E-mail: (JM); (LC)
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92
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Morahan B, Garcia-Bustos J. Kinase signalling in Plasmodium sexual stages and interventions to stop malaria transmission. Mol Biochem Parasitol 2014; 193:23-32. [PMID: 24509402 DOI: 10.1016/j.molbiopara.2014.01.005] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2013] [Revised: 01/22/2014] [Accepted: 01/28/2014] [Indexed: 12/26/2022]
Abstract
The symptoms of malaria, one of the infectious diseases with the highest mortality and morbidity world-wide, are caused by asexual parasites replicating inside red blood cells. Disease transmission, however, is effected by non-replicating cells which have differentiated into male or female gametocytes. These are the forms infectious to mosquito vectors and the insects are the only hosts where parasite sexual reproduction can take place. Malaria is thus a complex infection in which pharmacological treatment of symptoms may still allow transmission for long periods, while pharmacological blockage of infectivity may not cure symptoms. The process of parasite sexual differentiation and development is still being revealed but it is clear that kinase-mediated signalling mechanisms play a significant role. This review attempts to summarise our limited current knowledge on the signalling mechanisms involved in the transition from asexual replication to sexual differentiation and reproduction, with a brief mention to the effects of current treatments on the sexual stages and to some of the difficulties inherent in developing pharmacological interventions to curtail disease transmission.
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Affiliation(s)
- Belinda Morahan
- Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
| | - Jose Garcia-Bustos
- Department of Microbiology, Monash University, Clayton, Victoria 3800, Australia.
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93
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Chemical signatures and new drug targets for gametocytocidal drug development. Sci Rep 2014; 4:3743. [PMID: 24434750 PMCID: PMC3894558 DOI: 10.1038/srep03743] [Citation(s) in RCA: 80] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/11/2013] [Accepted: 12/20/2013] [Indexed: 01/14/2023] Open
Abstract
Control of parasite transmission is critical for the eradication of malaria. However, most antimalarial drugs are not active against P. falciparum gametocytes, responsible for the spread of malaria. Consequently, patients can remain infectious for weeks after the clearance of asexual parasites and clinical symptoms. Here we report the identification of 27 potent gametocytocidal compounds (IC50 < 1 μM) from screening 5,215 known drugs and compounds. All these compounds were active against three strains of gametocytes with different drug sensitivities and geographical origins, 3D7, HB3 and Dd2. Cheminformatic analysis revealed chemical signatures for P. falciparum sexual and asexual stages indicative of druggability and suggesting potential targets. Torin 2, a top lead compound (IC50 = 8 nM against gametocytes in vitro), completely blocked oocyst formation in a mouse model of transmission. These results provide critical new leads and potential targets to expand the repertoire of malaria transmission-blocking reagents.
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94
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Duffy S, Avery VM. Identification of inhibitors of Plasmodium falciparum gametocyte development. Malar J 2013; 12:408. [PMID: 24206914 PMCID: PMC3842684 DOI: 10.1186/1475-2875-12-408] [Citation(s) in RCA: 117] [Impact Index Per Article: 10.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2013] [Accepted: 11/05/2013] [Indexed: 12/28/2022] Open
Abstract
Background Plasmodium falciparum gametocytes, specifically mature stages, are the only stage in man transmissible to the mosquito vector responsible for malaria transmission. Anti-malarial drugs capable of killing these forms are considered essential for the eradication of malaria. The comprehensive profiling of in vitro activity of anti-malarial compounds against both early (I-III) and late (IV-V) stage P. falciparum gametocytes, along with the high throughput screening (HTS) outcomes from the MMV malaria box are described. Method Two anti-gametocyte HTS assays based on confocal fluorescence microscopy, utilizing both a gametocyte specific protein (pfs16-Luc-GFP) and a viability marker (MitoTracker Red CM-H2XRos) (MTR), were used for the measurement of anti-gametocytocidal activity. This combination provided a direct observation of gametocyte number per assay well, whilst defining the viability of each gametocyte imaged. Results IC50 values were obtained for 36 current anti-malarial compounds for activities against asexual, early and late stage gametocytes. The MMV malaria box was screened and actives progressed for IC50 evaluation. Seven % of the “drug-like” and 21% of the “probe-like” compounds from the MMV malaria box demonstrated equivalent activity against both asexual and late stage gametocytes. Conclusions The assays described were shown to selectively identify compounds with gametocytocidal activity and have been demonstrated suitable for HTS with the capability of screening in the order of 20,000 compounds per screening campaign, two to three times per seven-day week.
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Affiliation(s)
| | - Vicky M Avery
- Discovery Biology, Eskitis Institute for Drug Discovery, Griffith University, Nathan, Queensland 4111, Australia.
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95
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Abstract
Malaria elimination has recently been reinstated as a global health priority but current therapies seem to be insufficient for the task. Elimination efforts require new drug classes that alleviate symptoms, prevent transmission and provide a radical cure. To develop these next-generation medicines, public-private partnerships are funding innovative approaches to identify compounds that target multiple parasite species at multiple stages of the parasite life cycle. In this Review, we discuss the cell-, chemistry- and target-based approaches used to discover new drug candidates that are currently in clinical trials or undergoing preclinical testing.
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96
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Vial H, Taramelli D, Boulton IC, Ward SA, Doerig C, Chibale K. CRIMALDDI: platform technologies and novel anti-malarial drug targets. Malar J 2013; 12:396. [PMID: 24498961 PMCID: PMC3827883 DOI: 10.1186/1475-2875-12-396] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/17/2013] [Accepted: 10/22/2013] [Indexed: 12/24/2022] Open
Abstract
The Coordination, Rationalization, and Integration of antiMALarial drug Discovery & Development Initiatives (CRIMALDDI) Consortium, funded by the EU Framework Seven Programme, has attempted, through a series of interactive and facilitated workshops, to develop priorities for research to expedite the discovery of new anti-malarials. This paper outlines the recommendations for the development of enabling technologies and the identification of novel targets.Screening systems must be robust, validated, reproducible, and represent human malaria. They also need to be cost-effective. While such systems exist to screen for activity against blood stage Plasmodium falciparum, they are lacking for other Plasmodium spp. and other stages of the parasite's life cycle. Priority needs to be given to developing high-throughput screens that can identify activity against the liver and sexual stages. This in turn requires other enabling technologies to be developed to allow the study of these stages and to allow for the culture of liver cells and the parasite at all stages of its life cycle.As these enabling technologies become available, they will allow novel drug targets to be studied. Currently anti-malarials are mostly targeting the asexual blood stage of the parasite's life cycle. There are many other attractive targets that need to be investigated. The liver stages and the sexual stages will become more important as malaria control moves towards malaria elimination. Sexual development is a process offering multiple targets, even though the mechanisms of differentiation are still not fully understood. However, designing a drug whose effect is not curative but would be used in asymptomatic patients is difficult given current safety thresholds. Compounds active against the liver schizont would have a prophylactic effect and Plasmodium vivax elimination requires effectors against the dormant liver hypnozoites. It may be that drugs to be used in elimination campaigns will also need to have utility in the control phase. Compounds with activity against blood stages need to be screened for activity against other stages.Natural products should also be a valuable source of new compounds. They often occupy non-Lipinski chemical space and so may reveal valuable new chemotypes.
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Affiliation(s)
| | | | | | - Steve A Ward
- Liverpool School of Tropical Medicine, Pembroke Place, Liverpool L3 5QA, UK.
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97
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Held J, Kreidenweiss A, Mordmüller B. Novel approaches in antimalarial drug discovery. Expert Opin Drug Discov 2013; 8:1325-37. [PMID: 24090219 DOI: 10.1517/17460441.2013.843522] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
INTRODUCTION The development of new antimalarial drugs remains of the utmost importance, since Plasmodium falciparum has developed resistance against nearly all chemotherapeutics in clinical use. In an effort to contain the resistance of P. falciparum against artemisinins and to further eradication efforts, studies are ongoing to identify novel and more efficacious approaches to develop antimalarials. AREAS COVERED The authors review the classical and new approaches to antimalarial drug discovery, with a special emphasis on the various stages of the parasite's life cycle and the different Plasmodium species. The authors discuss the methodologies and strategies for early efficacy testing that aim to narrow down the portfolio of promising compounds. EXPERT OPINION The increased efforts in the discovery and development of new antimalarial compounds have led to the recognition of new promising hits. However, there is still major roadblock of selecting the most promising compounds and then further testing them in early clinical trials, especially in the current restricted economy. Controlled human malaria infection has much potential for speeding-up the early development process of many drug candidates including those which target the pre-erythrocytic stages.
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Affiliation(s)
- Jana Held
- University of Tübingen, Institute of Tropical Medicine , Wilhelmstraße 27, D-72074 Tübingen , Germany +49 7071 29 82364 ; +49 7071 295189 ;
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98
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Identification of MMV malaria box inhibitors of plasmodium falciparum early-stage gametocytes using a luciferase-based high-throughput assay. Antimicrob Agents Chemother 2013; 57:6050-62. [PMID: 24060871 DOI: 10.1128/aac.00870-13] [Citation(s) in RCA: 84] [Impact Index Per Article: 7.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
The design of new antimalarial combinations to treat Plasmodium falciparum infections requires drugs that, in addition to resolving disease symptoms caused by asexual blood stage parasites, can also interrupt transmission to the mosquito vector. Gametocytes, which are essential for transmission, develop as sexual blood stage parasites in the human host over 8 to 12 days and are the most accessible developmental stage for transmission-blocking drugs. Considerable effort is currently being devoted to identifying compounds active against mature gametocytes. However, investigations on the drug sensitivity of developing gametocytes, as well as screening methods for identifying inhibitors of early gametocytogenesis, remain scarce. We have developed a luciferase-based high-throughput screening (HTS) assay using tightly synchronous stage I to III gametocytes from a recombinant P. falciparum line expressing green fluorescent protein (GFP)-luciferase. The assay has been used to evaluate the early-stage gametocytocidal activity of the MMV Malaria Box, a collection of 400 compounds with known antimalarial (asexual blood stage) activity. Screening this collection against early-stage (I to III) gametocytes yielded 64 gametocytocidal compounds with 50% inhibitory concentrations (IC50s) below 2.5 μM. This assay is reproducible and suitable for the screening of large compound libraries, with an average percent coefficient of variance (%CV) of ≤5%, an average signal-to-noise ratio (S:N) of >30, and a Z' of ∼0.8. Our findings highlight the need for screening efforts directed specifically against early gametocytogenesis and indicate the importance of experimental verification of early-stage gametocytocidal activity in the development of new antimalarial candidates for combination therapy.
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99
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Flannery EL, Fidock DA, Winzeler EA. Using genetic methods to define the targets of compounds with antimalarial activity. J Med Chem 2013; 56:7761-71. [PMID: 23927658 DOI: 10.1021/jm400325j] [Citation(s) in RCA: 59] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
Abstract
Although phenotypic cellular screening has been used to drive antimalarial drug discovery in recent years, in some cases target-based drug discovery remains more attractive. This is especially true when appropriate high-throughput cellular assays are lacking, as is the case for drug discovery efforts that aim to provide a replacement for primaquine (4-N-(6-methoxyquinolin-8-yl)pentane-1,4-diamine), the only drug that can block Plasmodium transmission to Anopheles mosquitoes and eliminate liver-stage hypnozoites. At present, however, there are no known chemically validated parasite protein targets that are important in all Plasmodium parasite developmental stages and that can be used in traditional biochemical compound screens. We propose that a plethora of novel, chemically validated, cross-stage antimalarial targets still remain to be discovered from the ~5,500 proteins encoded by the Plasmodium genomes. Here we discuss how in vitro evolution of drug-resistant strains of Plasmodium falciparum and subsequent whole-genome analysis can be used to find the targets of some of the many compounds discovered in whole-cell phenotypic screens.
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Affiliation(s)
- Erika L Flannery
- Department of Pediatrics, University of California, San Diego, School of Medicine , 9500 Gilman Drive 0741, La Jolla, California 92093, United States
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Abstract
Drugs that kill or inhibit the sexual stages of Plasmodium in order to prevent transmission are important components of malaria control programmes. Reducing gametocyte carriage is central to the control of Plasmodium falciparum transmission as infection can result in extended periods of gametocytaemia. Unfortunately the number of drugs with activity against gametocytes is limited. Primaquine is currently the only licensed drug with activity against the sexual stages of malaria parasites and its use is hampered by safety concerns. This shortcoming is likely the result of the technical challenges associated with gametocyte studies together with the focus of previous drug discovery campaigns on asexual parasite stages. However recent emphasis on malaria eradication has resulted in an upsurge of interest in identifying compounds with activity against gametocytes. This review examines the gametocytocidal properties of currently available drugs as well as those in the development pipeline and examines the prospects for discovery of new anti-gametocyte compounds.
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