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Chery-Karschney L, Patrapuvich R, Mudeppa DG, Kokkonda S, Chakrabarti R, Sriwichai P, O'Connor RM, Rathod PK, White J. Tartrolon E, a secondary metabolite of a marine symbiotic bacterium, is a potent inhibitor of asexual and sexual Plasmodium falciparum. Antimicrob Agents Chemother 2024; 68:e0068423. [PMID: 38193705 PMCID: PMC10848769 DOI: 10.1128/aac.00684-23] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2023] [Accepted: 11/10/2023] [Indexed: 01/10/2024] Open
Abstract
Due to the spread of resistance to front-line artemisinin derivatives worldwide, there is a need for new antimalarials. Tartrolon E (TrtE), a secondary metabolite of a symbiotic bacterium of marine bivalve mollusks, is a promising antimalarial because it inhibits the growth of sexual and asexual blood stages of Plasmodium falciparum at sub-nanomolar levels. The potency of TrtE warrants further investigation into its mechanism of action, cytotoxicity, and ease with which parasites may evolve resistance to it.
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Affiliation(s)
| | - Rapatbhorn Patrapuvich
- Drug Research Unit for Malaria, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | | | - Sreekanth Kokkonda
- Department of Chemistry, University of Washington, Seattle, Washington, USA
| | - Rimi Chakrabarti
- Department of Chemistry, University of Washington, Seattle, Washington, USA
- Department of Medicine, Goa Medical College and Hospital, Bambolim, Goa, India
| | - Patchara Sriwichai
- Department of Medical Entomology, Faculty of Tropical Medicine, Mahidol University, Bangkok, Thailand
| | - Roberta M. O'Connor
- Department of Veterinary and Biomedical Sciences, College of Veterinary Medicine, University of Minnesota, Minneapolis, Minnesota, USA
| | | | - John White
- Department of Chemistry, University of Washington, Seattle, Washington, USA
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2
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B Henry N, Soulama I, S Sermé S, Bolscher JM, T G Huijs T, S Coulibaly A, Sombié S, Ouédraogo N, Diarra A, Zongo S, Guelbéogo WM, Nébié I, Sirima SB, Tiono AB, Pietro A, Collins KA, Dechering KJ, Bousema T. Assessment of the transmission blocking activity of antimalarial compounds by membrane feeding assays using natural Plasmodium falciparum gametocyte isolates from West-Africa. PLoS One 2023; 18:e0284751. [PMID: 37494413 PMCID: PMC10370769 DOI: 10.1371/journal.pone.0284751] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/15/2022] [Accepted: 04/07/2023] [Indexed: 07/28/2023] Open
Abstract
Antimalarial drugs that can block the transmission of Plasmodium gametocytes to mosquito vectors would be highly beneficial for malaria elimination efforts. Identifying transmission-blocking drugs currently relies on evaluation of their activity against gametocyte-producing laboratory parasite strains and would benefit from a testing pipeline with genetically diverse field isolates. The aims of this study were to develop a pipeline to test drugs against P. falciparum gametocyte field isolates and to evaluate the transmission-blocking activity of a set of novel compounds. Two assays were designed so they could identify both the overall transmission-blocking activity of a number of marketed and experimental drugs by direct membrane feeding assays (DMFA), and then also discriminate between those that are active against the gametocytes (gametocyte killing or sterilizing) or those that block development in the mosquito (sporontocidal). These DMFA assays used venous blood samples from naturally infected Plasmodium falciparum gametocyte carriers and locally reared Anopheles gambiae s.s. mosquitoes. Overall transmission-blocking activity was assessed following a 24 hour incubation of compound with gametocyte infected blood (TB-DMFA). Sporontocidal activity was evaluated following addition of compound directly prior to feeding, without incubation (SPORO-DMFA); Gametocyte viability was retained during 24-hour incubation at 37°C when gametocyte infected red blood cells were reconstituted in RPMI/serum. Methylene-blue, MMV693183, DDD107498, atovaquone and P218 showed potent transmission-blocking activity in the TB-DMFA, and both atovaquone and the novel antifolate P218 were potent inhibitors of sporogonic development in the SPORO-DMA. This work establishes a pipeline for the integral use of field isolates to assess the transmission-blocking capacity of antimalarial drugs to block transmission that should be validated in future studies.
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Affiliation(s)
- Noëlie B Henry
- Groupe de Recherche Action en Santé, Ouagadougou, Burkina Faso
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Issiaka Soulama
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
- Institut de Recherche en Sciences de la Santé (IRSS)/CNRST, Ouagadougou, Burkina Faso
| | - Samuel S Sermé
- Groupe de Recherche Action en Santé, Ouagadougou, Burkina Faso
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | | | | | - Aboubacar S Coulibaly
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Salif Sombié
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Nicolas Ouédraogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Amidou Diarra
- Groupe de Recherche Action en Santé, Ouagadougou, Burkina Faso
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Soumanaba Zongo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Wamdaogo M Guelbéogo
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Issa Nébié
- Groupe de Recherche Action en Santé, Ouagadougou, Burkina Faso
| | | | - Alfred B Tiono
- Centre National de Recherche et de Formation sur le Paludisme, Ouagadougou, Burkina Faso
| | - Alano Pietro
- Dipartimento di Malattie Infettive, Istituto Superiore di Sanità, Roma, Italy
| | - Katharine A Collins
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherland
| | | | - Teun Bousema
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, Netherland
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Miyazaki Y, Vos MW, Geurten FJA, Bigeard P, Kroeze H, Yoshioka S, Arisawa M, Inaoka DK, Soulard V, Dechering KJ, Franke-Fayard B, Miyazaki S. A versatile Plasmodium falciparum reporter line expressing NanoLuc enables highly sensitive multi-stage drug assays. Commun Biol 2023; 6:713. [PMID: 37438491 DOI: 10.1038/s42003-023-05078-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Accepted: 06/27/2023] [Indexed: 07/14/2023] Open
Abstract
Transgenic luciferase-expressing Plasmodium falciparum parasites have been widely used for the evaluation of anti-malarial compounds. Here, to screen for anti-malarial drugs effective against multiple stages of the parasite, we generate a P. falciparum reporter parasite that constitutively expresses NanoLuciferase (NanoLuc) throughout its whole life cycle. The NanoLuc-expressing P. falciparum reporter parasite shows a quantitative NanoLuc signal in the asexual blood, gametocyte, mosquito, and liver stages. We also establish assay systems to evaluate the anti-malarial activity of compounds at the asexual blood, gametocyte, and liver stages, and then determine the 50% inhibitory concentration (IC50) value of several anti-malarial compounds. Through the development of this robust high-throughput screening system, we identify an anti-malarial compound that kills the asexual blood stage parasites. Our study highlights the utility of the NanoLuc reporter line, which may advance anti-malarial drug development through the improved screening of compounds targeting the human malarial parasite at multiple stages.
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Affiliation(s)
- Yukiko Miyazaki
- Department of Molecular Infection Dynamics, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 852-8523, Nagasaki, Japan.
- Department of Parasitology, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands.
- Department of Protozoology, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan.
| | - Martijn W Vos
- TropIQ Health Sciences, Transistorweg 5, 6534 AT, Nijmegen, The Netherlands
| | - Fiona J A Geurten
- Department of Parasitology, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands
| | - Pierre Bigeard
- Sorbonne Université, Inserm, CNRS, Centre d'Immunologie et des Maladies Infectieuses, CIMI-Paris, F-75013, Paris, France
| | - Hans Kroeze
- Department of Parasitology, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands
| | - Shohei Yoshioka
- Graduate School of Pharmaceutical Sciences, Osaka University, 565-0871, Osaka, Japan
| | - Mitsuhiro Arisawa
- Graduate School of Pharmaceutical Sciences, Osaka University, 565-0871, Osaka, Japan
| | - Daniel Ken Inaoka
- Department of Molecular Infection Dynamics, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 852-8523, Nagasaki, Japan
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, 852-8523, Japan
- Department of Biomedical Chemistry, Graduate School of Medicine, The University of Tokyo, Tokyo, 113-0033, Japan
| | - Valerie Soulard
- Sorbonne Université, Inserm, CNRS, Centre d'Immunologie et des Maladies Infectieuses, CIMI-Paris, F-75013, Paris, France
| | - Koen J Dechering
- TropIQ Health Sciences, Transistorweg 5, 6534 AT, Nijmegen, The Netherlands
| | - Blandine Franke-Fayard
- Department of Parasitology, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands
| | - Shinya Miyazaki
- Department of Parasitology, Leiden University Medical Center, 2333 ZA, Leiden, The Netherlands.
- Department of Cellular Architecture Studies, Institute of Tropical Medicine (NEKKEN), Nagasaki University, 852-8523, Nagasaki, Japan.
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Hayakawa ESH, Wayama M, Tokumasu F, Ohno N, Matsumoto M, Usukura J. Budding pouches and associated bubbles: 3D visualization of exo-membrane structures in plasmodium falciparum gametocytes. Front Cell Infect Microbiol 2022; 12:962495. [PMID: 36072224 PMCID: PMC9441640 DOI: 10.3389/fcimb.2022.962495] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/06/2022] [Accepted: 08/02/2022] [Indexed: 11/16/2022] Open
Abstract
Plasmodium falciparum gametocytes have unique morphology, metabolism, and protein expression profiles in their asexual stages of development. In addition to the striking changes in their appearance, a wide variety of “exo-membrane structures” are newly formed in the gametocyte stage. Little is known about their function, localization, or three-dimensional structural information, and only some structural data, typically two-dimensional, have been reported using conventional electron microscopy or fluorescence microscopy. For better visualization of intracellular organelle and exo-membrane structures, we previously established an unroofing technique to directly observe Maurer’s clefts (MCs) in asexual parasitized erythrocytes by removing the top part of the cell’s membrane followed by transmission electron microscopy. We found that MCs have numerous tethers connecting themselves to the host erythrocyte membrane skeletons. In this study, we investigated the intracellular structures of gametocytes using unroofing-TEM, Serial Block Face scanning electron microscopy, and fluorescence microscopy to unveil the exo-membrane structures in gametocytes. Our data showed “balloon/pouch”-like objects budding from the parasitophorous vacuole membrane (PVM) in gametocytes, and some balloons included multiple layers of other balloons. Furthermore, numerous bubbles appeared on the inner surface of the erythrocyte membrane or PVM; these were similar to MC-like membranes but were smaller than asexual MCs. Our study demonstrated P. falciparum reforms exo-membranes in erythrocytes to meet stage-specific biological activities during their sexual development.
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Affiliation(s)
- Eri Saki H. Hayakawa
- Division of Medical Zoology, Department of Infection and Immunity, Jichi Medical University, Tochigi, Japan
- *Correspondence: Eri Saki H. Hayakawa, ; Fuyuki Tokumasu,
| | - Marina Wayama
- Nanostructure Characterization Group, Solution Development Department, Hitachi High-Tech Corporation, Tokyo, Japan
| | - Fuyuki Tokumasu
- Department of Cellular Architecture Studies, Institute of Tropical Medicine (NEKKEN), Nagasaki University, Nagasaki, Japan
- *Correspondence: Eri Saki H. Hayakawa, ; Fuyuki Tokumasu,
| | - Nobuhiko Ohno
- Division of Histology and Cell Biology, Department of Anatomy, Jichi Medical University, Tochigi, Japan
- Division of Ultrastructural Research, National Institute for Physiological Sciences, Okazaki, Japan
| | - Mami Matsumoto
- Section of Electron Microscopy, Supportive Center for Brain Research, National Institute for Physiological Sciences, Okazaki, Japan
- Department of Developmental and Regenerative Neurobiology, Institute of Brain Science, Nagoya City University Graduate School of Medical Sciences, Nagoya, Japan
| | - Jiro Usukura
- Institute of Material and Systems for Sustainability, Nagoya University, Nagoya, Japan
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Mughal H, Bell EC, Mughal K, Derbyshire ER, Freundlich JS. Random Forest Model Predictions Afford Dual-Stage Antimalarial Agents. ACS Infect Dis 2022; 8:1553-1562. [PMID: 35894649 PMCID: PMC9987178 DOI: 10.1021/acsinfecdis.2c00189] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
The need for novel antimalarials is apparent given the continuing disease burden worldwide, despite significant drug discovery advances from the bench to the bedside. In particular, small-molecule agents with potent efficacy against both the liver and blood stages of Plasmodium parasite infection are critical for clinical settings as they would simultaneously prevent and treat malaria with a reduced selection pressure for resistance. While experimental screens for such dual-stage inhibitors have been conducted, the time and cost of these efforts limit their scope. Here, we have focused on leveraging machine learning approaches to discover novel antimalarials with such properties. A random forest modeling approach was taken to predict small molecules with in vitro efficacy versus liver-stage Plasmodium berghei parasites and a lack of human liver cell cytotoxicity. Empirical validation of the model was achieved with the realization of hits with liver-stage efficacy after prospective scoring of a commercial diversity library and consideration of structural diversity. A subset of these hits also demonstrated promising blood-stage Plasmodium falciparum efficacy. These 18 validated dual-stage antimalarials represent novel starting points for drug discovery and mechanism of action studies with significant potential for seeding a new generation of therapies.
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Affiliation(s)
- Haseeb Mughal
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers University – New Jersey Medical School, 185 South Orange Ave, Newark, NJ, 07103
| | - Elise C. Bell
- Department of Chemistry, Duke University, 124 Science Drive, Durham, NC 27708, USA
| | - Khadija Mughal
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers University – New Jersey Medical School, 185 South Orange Ave, Newark, NJ, 07103
| | - Emily R. Derbyshire
- Department of Chemistry, Duke University, 124 Science Drive, Durham, NC 27708, USA
- Department of Molecular Genetics and Microbiology, Duke University Medical Center, 213 Research Drive, Durham, NC 27710, USA
| | - Joel S. Freundlich
- Department of Pharmacology, Physiology, and Neuroscience, Rutgers University – New Jersey Medical School, 185 South Orange Ave, Newark, NJ, 07103
- Department of Medicine, Center for Emerging and Re-emerging Pathogens, Rutgers University – New Jersey Medical School, Newark, NJ, 07103
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6
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Gametocyte-specific and all-blood-stage transmission-blocking chemotypes discovered from high throughput screening on Plasmodium falciparum gametocytes. Commun Biol 2022; 5:547. [PMID: 35668202 PMCID: PMC9170688 DOI: 10.1038/s42003-022-03510-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/09/2022] [Accepted: 05/19/2022] [Indexed: 11/25/2022] Open
Abstract
Blocking Plasmodium falciparum human-to-mosquito transmission is essential for malaria elimination, nonetheless drugs killing the pathogenic asexual stages are generally inactive on the parasite transmissible stages, the gametocytes. Due to technical and biological limitations in high throughput screening of non-proliferative stages, the search for gametocyte-killing molecules so far tested one tenth the number of compounds screened on asexual stages. Here we overcome these limitations and rapidly screened around 120,000 compounds, using not purified, bioluminescent mature gametocytes. Orthogonal gametocyte assays, selectivity assays on human cells and asexual parasites, followed by compound clustering, brought to the identification of 84 hits, half of which are gametocyte selective and half with comparable activity against sexual and asexual parasites. We validated seven chemotypes, three of which are, to the best of our knowledge, novel. These molecules are able to inhibit male gametocyte exflagellation and block parasite transmission through the Anopheles mosquito vector in a standard membrane feeding assay. This work shows that interrogating a wide and diverse chemical space, with a streamlined gametocyte HTS and hit validation funnel, holds promise for the identification of dual stage and gametocyte-selective compounds to be developed into new generation of transmission blocking drugs for malaria elimination. High-throughput screening of 120,000 compounds followed by counter-screening and validation assays reveals candidate antimalarial drugs that kill Plasmodium falciparum sexual and asexual blood stages blocking parasite transmission through mosquito.
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Kumari V, Prasad KM, Kalia I, Sindhu G, Dixit R, Rawat DS, Singh OP, Singh AP, Pandey KC. Dissecting The role of Plasmodium metacaspase-2 in malaria gametogenesis and sporogony. Emerg Microbes Infect 2022; 11:938-955. [PMID: 35264080 PMCID: PMC8973346 DOI: 10.1080/22221751.2022.2052357] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/08/2023]
Abstract
The family of apicomplexan specific proteins contains caspases–like proteins called “metacaspases”. These enzymes are present in the malaria parasite but absent in human; therefore, these can be explored as potential drug targets. We deleted the MCA-2 gene from Plasmodium berghei genome using a gene knockout strategy to decipher its precise function. This study has identified that MCA-2 plays an important role in parasite transmission since it is critical for the formation of gametocytes and for maintaining an appropriate number of infectious sporozoites required for sporogony. It is noticeable that a significant reduction in gametocyte, oocysts, ookinete and sporozoites load along with a delay in hepatocytes invasion were observed in the MCA-2 knockout parasite. Furthermore, a study found the two MCA-2 inhibitory molecules known as C-532 and C-533, which remarkably inhibited the MCA-2 activity, abolished the in vitro parasite growth, and also impaired the transmission cycle of P. falciparum and P. berghei in An. stephensi. Our findings indicate that the deletion of MCA-2 hampers the Plasmodium development during erythrocytic and exo-erythrocytic stages, and its inhibition by C-532 and C-533 critically affects the malaria transmission biology.
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Affiliation(s)
- Vandana Kumari
- ICMR-National Institute of Malaria Research, New Delhi, India
| | | | | | | | - Rajnikant Dixit
- ICMR-National Institute of Malaria Research, New Delhi, India
| | - Diwan S Rawat
- Depatment of Chemistry, University of Delhi, New Delhi, India
| | - O P Singh
- ICMR-National Institute of Malaria Research, New Delhi, India
| | - Agam P Singh
- National Institute of Immunology, New Delhi, India
| | - Kailash C Pandey
- ICMR-National Institute of Malaria Research, New Delhi, India.,Academy of Scientific and Innovative Research (AcSIR), Ghaziabad Uttar Pradesh, UP, India
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Consalvi S, Tammaro C, Appetecchia F, Biava M, Poce G. Malaria transmission blocking compounds: a patent review. Expert Opin Ther Pat 2022; 32:649-666. [PMID: 35240899 DOI: 10.1080/13543776.2022.2049239] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/04/2022]
Abstract
INTRODUCTION Despite substantial progress in the field, malaria remains a global health issue and currently available control strategies are not sufficient to achieve eradication. Agents able to prevent transmission are likely to have a strong impact on malaria control and have been prioritized as a primary objective to reduce the number of secondary infections. Therefore, there is an increased interest in finding novel drugs targeting sexual stages of Plasmodium and innovative methods to target malaria transmission from host to vector, and vice versa. AREAS COVERED This review covers innovative transmission-blocking inventions patented between 2015 and October 2021. The focus is on chemical interventions which could be used as "chemical vaccines" to prevent transmission (small molecules, carbohydrates, and polypeptides). EXPERT OPINION Even though the development of novel strategies to block transmission still requires fundamental additional research and a deeper understanding of parasite sexual stages biology, the research in this field has significantly accelerated. Among innovative inventions patented over the last six years, the surface-delivery of antimalarial drugs to kill transmission-stages parasites in mosquitoes holds the highest promise for success in malaria control strategies, opening completely new scenarios in malaria transmission-blocking drug discovery.
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Affiliation(s)
- Sara Consalvi
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Chiara Tammaro
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Federico Appetecchia
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Mariangela Biava
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
| | - Giovanna Poce
- Department of Chemistry and Technologies of Drug, Sapienza University of Rome, piazzale A. Moro 5, 00185 Rome, Italy
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Birkholtz LM, Alano P, Leroy D. Transmission-blocking drugs for malaria elimination. Trends Parasitol 2022; 38:390-403. [DOI: 10.1016/j.pt.2022.01.011] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/05/2021] [Revised: 01/19/2022] [Accepted: 01/24/2022] [Indexed: 12/24/2022]
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The transcriptional regulator HDP1 controls expansion of the inner membrane complex during early sexual differentiation of malaria parasites. Nat Microbiol 2022; 7:289-299. [PMID: 35087229 PMCID: PMC8852293 DOI: 10.1038/s41564-021-01045-0] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2020] [Accepted: 12/08/2021] [Indexed: 12/28/2022]
Abstract
Transmission of Plasmodium falciparum and other malaria parasites requires their differentiation from asexual blood stages into gametocytes, the non-replicative sexual stage necessary to infect the mosquito vector. This transition involves changes in gene expression and chromatin reorganization that result in the activation and silencing of stage-specific genes. However, the genomes of malaria parasites have been noted for their limited number of transcriptional and chromatin regulators, and the molecular mediators of these changes remain largely unknown. We recently identified homeodomain protein 1 (HDP1) as a DNA-binding protein, first expressed in gametocytes, that enhances the expression of key genes critical for early sexual differentiation. The discovery of HDP1 marks a new class of transcriptional regulator in malaria parasites outside of the better-characterized ApiAP2 family. Here, using molecular biology, biochemistry and microscopy techniques, we show that HDP1 is essential for gametocyte maturation, facilitating the necessary upregulation of inner membrane complex components during early gametocytogenesis that gives P. falciparum gametocytes their characteristic shape.
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11
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Ceravolo IP, Aguiar AC, Adebayo JO, Krettli AU. Studies on Activities and Chemical Characterization of Medicinal Plants in Search for New Antimalarials: A Ten Year Review on Ethnopharmacology. Front Pharmacol 2021; 12:734263. [PMID: 34630109 PMCID: PMC8493299 DOI: 10.3389/fphar.2021.734263] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/30/2021] [Accepted: 08/31/2021] [Indexed: 11/17/2022] Open
Abstract
Malaria is an endemic disease that affected 229 million people and caused 409 thousand deaths, in 2019. Disease control is based on early diagnosis and specific treatment with antimalarial drugs since no effective vaccines are commercially available to prevent the disease. Drug chemotherapy has a strong historical link to the use of traditional plant infusions and other natural products in various cultures. The research based on such knowledge has yielded two drugs in medicine: the alkaloid quinine from Cinchona species, native in the Amazon highland rain forest in South America, and artemisinin from Artemisia annua, a species from the millenary Chinese medicine. The artemisinin-based combination therapies (ACTs), proven to be highly effective against malaria parasites, and considered as “the last bullet to fight drug-resistant malaria parasites,” have limited use now due to the emergence of multidrug resistance. In addition, the limited number of therapeutic options makes urgent the development of new antimalarial drugs. This review focuses on the antimalarial activities of 90 plant species obtained from a search using Pubmed database with keywords “antimalarials,” “plants” and “natural products.” We selected only papers published in the last 10 years (2011–2020), with a further analysis of those which were tested experimentally in malaria infected mice. Most plant species studied were from the African continent, followed by Asia and South America; their antimalarial activities were evaluated against asexual blood parasites, and only one species was evaluated for transmission blocking activity. Only a few compounds isolated from these plants were active and had their mechanisms of action delineated, thereby limiting the contribution of these medicinal plants as sources of novel antimalarial pharmacophores, which are highly necessary for the development of effective drugs. Nevertheless, the search for bioactive compounds remains as a promising strategy for the development of new antimalarials and the validation of traditional treatments against malaria. One species native in South America, Ampelozyzyphus amazonicus, and is largely used against human malaria in Brazil has a prophylactic effect, interfering with the viability of sporozoites in in vitro and in vivo experiments.
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Affiliation(s)
- Isabela P Ceravolo
- Instituto René Rachou, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Brazil
| | - Anna C Aguiar
- Departamento de Biociência, Universidade Federal de São Paulo, Santos, Brazil
| | - Joseph O Adebayo
- Department of Biochemistry, University of Ilorin, Ilorin, Nigeria
| | - Antoniana U Krettli
- Instituto René Rachou, Fundação Oswaldo Cruz (Fiocruz), Belo Horizonte, Brazil
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Kiryukhin MV, Lau HH, Lim SH, Salgado G, Fan C, Ng YZ, Leavesley DI, Upton Z. Arrays of Biocompatible and Mechanically Robust Microchambers Made of Protein-Polyphenol-Clay Multilayer Films. ACS Biomater Sci Eng 2020; 6:5653-5661. [PMID: 33320583 DOI: 10.1021/acsbiomaterials.0c00973] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
There is a growing demand for biocompatible and mechanically robust arrays of microcompartments loaded with minute amounts of active substances for sensing or controlled release applications. Here we report on a novel biocompatible composite material, protein-polyphenol-clay (PPC) multilayer film. The material is shown to be strong enough to make robust microchambers retaining the shape and dimensions of truncated square pyramids. We study the mechanical properties and biocompatibility of the PPC microchambers and compare them to those made of synthetic polyelectrolyte multilayer film, poly(styrenesulfonate)-poly(allylammonium) (PSS-PAH). The mechanical properties of the microchambers were characterized under uniaxial compression using nanoindentation with a flat-punch tip. The effective Young's modulus of PPC microchambers, 166 ± 53 MPa, is found to be lower than that of PSS-PAH microchambers, 245 ± 52 MPa. However, the capacity to elastically absorb the energy of the former, 2.4 ± 1.0 MPa, is marginally higher than of the latter, 2.0 ± 1.3 MPa. Arrays of microchambers were sealed onto a polyethylene film, loaded with a model oil-soluble drug, and their biocompatibility was tested using an ex vivo 3D human skin reconstruct model. We found no evidence for toxicity with the PPC microchambers; however, PSS-PAH microchambers stimulated reduced cell density in the epidermis and significantly affected epidermal-dermal attachment. Both materials do not alter skin cell proliferation but affect skin cell differentiation. We interpret that rather than affecting epidermal barrier function, these data suggest the applied plastic films with microchamber arrays affect transpiration, normoxia, and moisture exchange.
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Affiliation(s)
- Maxim V Kiryukhin
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634
| | - Hooi Hong Lau
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634
| | - Su Hui Lim
- Institute of Materials Research and Engineering, Agency for Science, Technology and Research (A*STAR), 2 Fusionopolis Way, Innovis, #08-03, Singapore 138634
| | - Giorgiana Salgado
- Skin Research Institute of Singapore, A*STAR, 11 Mandalay Road, #17-01, Singapore 308232
| | - Chen Fan
- Skin Research Institute of Singapore, A*STAR, 11 Mandalay Road, #17-01, Singapore 308232
| | - Yi Zhen Ng
- Skin Research Institute of Singapore, A*STAR, 11 Mandalay Road, #17-01, Singapore 308232
| | - David I Leavesley
- Skin Research Institute of Singapore, A*STAR, 11 Mandalay Road, #17-01, Singapore 308232
| | - Zee Upton
- Skin Research Institute of Singapore, A*STAR, 11 Mandalay Road, #17-01, Singapore 308232
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13
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Abstract
As the world gets closer to eliminating malaria, the scientific community worldwide has begun to realize the importance of malaria transmission-blocking interventions. The onus of breaking the life cycle of the human malaria parasite Plasmodium falciparum predominantly rests upon transmission-blocking drugs because of emerging resistance to commonly used schizonticides and insecticides. This third part of our review series on malaria transmission-blocking entails transmission-blocking potential of preclinical transmission-blocking antimalarials and other non-malaria drugs/experimental compounds that are not in clinical or preclinical development for malaria but possess transmission-blocking potential. Collective analysis of the structure and the activity of these experimental compounds might pave the way toward generation of novel prototypes of next-generation transmission-blocking drugs.
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14
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Abstract
The scientific community worldwide has realized that malaria elimination will not be possible without development of safe and effective transmission-blocking interventions. Primaquine, the only WHO recommended transmission-blocking drug, is not extensively utilized because of the toxicity issues in G6PD deficient individuals. Therefore, there is an urgent need to develop novel therapeutic interventions that can target malaria parasites and effectively block transmission. But at first, it is imperative to unravel the existing portfolio of transmission-blocking drugs. This review highlights transmission-blocking potential of current antimalarial drugs and drugs that are in various stages of clinical development. The collective analysis of the relationships between the structure and the activity of transmission-blocking drugs is expected to help in the design of new transmission-blocking antimalarials.
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15
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Valenciano AL, Fernández-Murga ML, Merino EF, Holderman NR, Butschek GJ, Shaffer KJ, Tyler PC, Cassera MB. Metabolic dependency of chorismate in Plasmodium falciparum suggests an alternative source for the ubiquinone biosynthesis precursor. Sci Rep 2019; 9:13936. [PMID: 31558748 PMCID: PMC6763611 DOI: 10.1038/s41598-019-50319-5] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/21/2019] [Accepted: 09/10/2019] [Indexed: 01/17/2023] Open
Abstract
The shikimate pathway, a metabolic pathway absent in humans, is responsible for the production of chorismate, a branch point metabolite. In the malaria parasite, chorismate is postulated to be a direct precursor in the synthesis of p-aminobenzoic acid (folate biosynthesis), p-hydroxybenzoic acid (ubiquinone biosynthesis), menaquinone, and aromatic amino acids. While the potential value of the shikimate pathway as a drug target is debatable, the metabolic dependency of chorismate in P. falciparum remains unclear. Current evidence suggests that the main role of chorismate is folate biosynthesis despite ubiquinone biosynthesis being active and essential in the malaria parasite. Our goal in the present work was to expand our knowledge of the ubiquinone head group biosynthesis and its potential metabolic dependency on chorismate in P. falciparum. We systematically assessed the development of both asexual and sexual stages of P. falciparum in a defined medium in the absence of an exogenous supply of chorismate end-products and present biochemical evidence suggesting that the benzoquinone ring of ubiquinones in this parasite may be synthesized through a yet unidentified route.
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Affiliation(s)
- Ana Lisa Valenciano
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Maria L Fernández-Murga
- Laboratory of Experimental Pathology, Health Research Institute Hospital La Fe, Valencia, 46026, Spain
| | - Emilio F Merino
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Nicole R Holderman
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Grant J Butschek
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States
| | - Karl J Shaffer
- The Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Peter C Tyler
- The Ferrier Research Institute, Victoria University of Wellington, Lower Hutt, New Zealand
| | - Maria Belen Cassera
- Department of Biochemistry & Molecular Biology, and Center for Tropical and Emerging Global Diseases (CTEGD), University of Georgia, Athens, Georgia, 30602, United States.
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16
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Tanaka TQ, Tokuoka SM, Nakatani D, Hamano F, Kawazu SI, Wellems TE, Kita K, Shimizu T, Tokumasu F. Polyunsaturated fatty acids promote Plasmodium falciparum gametocytogenesis. Biol Open 2019; 8:bio.042259. [PMID: 31221627 PMCID: PMC6679406 DOI: 10.1242/bio.042259] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022] Open
Abstract
The molecular triggers of sexual differentiation into gametocytes by blood stage Plasmodium falciparum, the most malignant human malaria parasites, are subject of much investigation for potential transmission-blocking strategies. The parasites are readily grown in vitro with culture media supplemented by the addition of human serum (10%) or by a commercially available substitute (0.5% AlbuMAX). We found better gametocytemia with serum than AlbuMAX, suggesting suboptimal concentrations of some components in the commercial product; consistent with this hypothesis, substantial concentration differences of multiple fatty acids were detected between serum- and AlbuMAX-supplemented media. Mass spectroscopy analysis distinguished the lipid profiles of gametocyte- and asexual stage-parasite membranes. Delivery of various combinations of unsaturated fatty-acid-containing phospholipids to AlbuMAX-supported gametocyte cultures improved gametocyte production to the levels achieved with human-serum-supplemented media. Maturing gametocytes readily incorporated externally supplied d5-labeled glycerol with fatty acids into unsaturated phospholipids. Phospholipids identified in this work thus may be taken up from extracellular sources or generated internally for important steps of gametocyte development. Further study of polyunsaturated fatty-acid metabolism and phospholipid profiles will improve understanding of gametocyte development and malaria parasite transmission.
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Affiliation(s)
- Takeshi Q Tanaka
- International Medical Zoology, Graduate School of Medicine, Kagawa University, Kagawa, 761-0793, Japan.,Laboratory of Malaria and Vector Research, National Institute of Allergy and Vector Research, National Institutes of Health, Bethesda, MD 20892-8132, USA.,Research Unit of Advanced Preventive Medicine, National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Suzumi M Tokuoka
- Department of Lipidomics, Graduate School of Medicine, The University of Tokyo, Tokyo, 103-0033, Japan
| | - Daichi Nakatani
- Research Unit of Advanced Preventive Medicine, National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Fumie Hamano
- Lipid Signaling Project, Research Institute National Center for Global Health and Medicine, Tokyo, 162-8655, Japan
| | - Shin-Ichiro Kawazu
- Research Unit of Advanced Preventive Medicine, National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Obihiro, Hokkaido 080-8555, Japan
| | - Thomas E Wellems
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Vector Research, National Institutes of Health, Bethesda, MD 20892-8132, USA
| | - Kiyoshi Kita
- School of Tropical Medicine and Global Health, Nagasaki University, Nagasaki, 852-8523, Japan
| | - Takao Shimizu
- Department of Lipidomics, Graduate School of Medicine, The University of Tokyo, Tokyo, 103-0033, Japan.,Lipid Signaling Project, Research Institute National Center for Global Health and Medicine, Tokyo, 162-8655, Japan
| | - Fuyuki Tokumasu
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Vector Research, National Institutes of Health, Bethesda, MD 20892-8132, USA .,Department of Lipidomics, Graduate School of Medicine, The University of Tokyo, Tokyo, 103-0033, Japan
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17
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Yahiya S, Rueda-Zubiaurre A, Delves MJ, Fuchter MJ, Baum J. The antimalarial screening landscape-looking beyond the asexual blood stage. Curr Opin Chem Biol 2019; 50:1-9. [PMID: 30875617 PMCID: PMC6591700 DOI: 10.1016/j.cbpa.2019.01.029] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/17/2018] [Revised: 01/28/2019] [Accepted: 01/30/2019] [Indexed: 12/20/2022]
Abstract
In recent years, the research agenda to tackle global morbidity and mortality from malaria disease has shifted towards innovation, in the hope that efforts at the frontiers of scientific research may re-invigorate gains made towards eradication. Discovery of new antimalarial drugs with novel chemotypes or modes of action lie at the heart of these efforts. There is a particular interest in drug candidates that target stages of the malaria parasite lifecycle beyond the symptomatic asexual blood stages. This is especially important given the spectre of emerging drug resistance to all current frontline antimalarials. One approach gaining increased interest is the potential of designing novel drugs that target parasite passage from infected individual to feeding mosquito and back again. Action of such therapeutics is geared much more at the population level rather than just concerned with the infected individual. The search for novel drugs active against these stages has been helped by improvements to in vitro culture of transmission and pre-erythrocytic parasite lifecycle stages, robotic automation and high content imaging, methodologies that permit the high-throughput screening (HTS) of compound libraries for drug discovery. Here, we review recent advances in the antimalarial screening landscape, focussed on transmission blocking as a key aim for drug-treatment campaigns of the future.
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Affiliation(s)
- Sabrina Yahiya
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London SW7 2AZ, UK
| | - Ainoa Rueda-Zubiaurre
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 OBZ, UK
| | - Michael J Delves
- London School of Hygiene and Tropical Medicine, Keppel Street, London WC1E 7HT, UK
| | - Matthew J Fuchter
- Department of Chemistry, Imperial College London, Molecular Sciences Research Hub, White City Campus, Wood Lane, London W12 OBZ, UK
| | - Jake Baum
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London SW7 2AZ, UK.
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18
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Critical examination of approaches exploited to assess the effectiveness of transmission-blocking drugs for malaria. Future Med Chem 2018; 10:2619-2639. [PMID: 30499742 DOI: 10.4155/fmc-2018-0169] [Citation(s) in RCA: 15] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/05/2023] Open
Abstract
In the absence of clinically proven vaccines and emerging resistance to common antimalarials and insecticides, the onus of interrupting the life cycle of Plasmodium falciparum, is upon the transmission-blocking drugs. Current transmission-blocking drug primaquine finds its use restricted because of associated hemolytic toxicity issues in Glucose-6-Phosphate-Dehydrogenase deficient individuals. This article provides an extensive review of the assays used by the investigators to evaluate the transmission-blocking activity of drugs. Furthermore, limitations in existing transmission-blocking assessment approaches/studies are also covered in detail. This review is expected to help in the identification of lacunae in current understanding of transmission-blocking strategies, which are hindering our efforts to develop sustainable and effective transmission-blocking interventions.
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19
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Delves MJ, Miguel-Blanco C, Matthews H, Molina I, Ruecker A, Yahiya S, Straschil U, Abraham M, León ML, Fischer OJ, Rueda-Zubiaurre A, Brandt JR, Cortés Á, Barnard A, Fuchter MJ, Calderón F, Winzeler EA, Sinden RE, Herreros E, Gamo FJ, Baum J. A high throughput screen for next-generation leads targeting malaria parasite transmission. Nat Commun 2018; 9:3805. [PMID: 30228275 PMCID: PMC6143625 DOI: 10.1038/s41467-018-05777-2] [Citation(s) in RCA: 70] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2018] [Accepted: 07/26/2018] [Indexed: 01/22/2023] Open
Abstract
Spread of parasite resistance to artemisinin threatens current frontline antimalarial therapies, highlighting the need for new drugs with alternative modes of action. Since only 0.2–1% of asexual parasites differentiate into sexual, transmission-competent forms, targeting this natural bottleneck provides a tangible route to interrupt disease transmission and mitigate resistance selection. Here we present a high-throughput screen of gametogenesis against a ~70,000 compound diversity library, identifying seventeen drug-like molecules that target transmission. Hit molecules possess varied activity profiles including male-specific, dual acting male–female and dual-asexual-sexual, with one promising N-((4-hydroxychroman-4-yl)methyl)-sulphonamide scaffold found to have sub-micromolar activity in vitro and in vivo efficacy. Development of leads with modes of action focussed on the sexual stages of malaria parasite development provide a previously unexplored base from which future therapeutics can be developed, capable of preventing parasite transmission through the population. Sexual forms of malaria parasites are responsible for transmission to the mosquito. Anti-malarial drug resistance remains a serious problem and requires advent of new drug therapies. Here, the authors present a high-throughput screen of potential antimalarial compounds, identifying seventeen drug-like molecules specifically targeting transmission.
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Affiliation(s)
- Michael J Delves
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Celia Miguel-Blanco
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK.,Diseases of the Developing World (DDW), GlaxoSmithKline, 28760, Tres Cantos, Madrid, Spain
| | - Holly Matthews
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Irene Molina
- Diseases of the Developing World (DDW), GlaxoSmithKline, 28760, Tres Cantos, Madrid, Spain
| | - Andrea Ruecker
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Sabrina Yahiya
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Ursula Straschil
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Matthew Abraham
- School of Medicine, University of California San Diego, 9500 Gilman Drive 0760, La Jolla, CA, 92093, USA
| | - María Luisa León
- Diseases of the Developing World (DDW), GlaxoSmithKline, 28760, Tres Cantos, Madrid, Spain
| | - Oliver J Fischer
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Ainoa Rueda-Zubiaurre
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Jochen R Brandt
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Álvaro Cortés
- Diseases of the Developing World (DDW), GlaxoSmithKline, 28760, Tres Cantos, Madrid, Spain
| | - Anna Barnard
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Matthew J Fuchter
- Department of Chemistry, Imperial College London, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Félix Calderón
- Diseases of the Developing World (DDW), GlaxoSmithKline, 28760, Tres Cantos, Madrid, Spain
| | - Elizabeth A Winzeler
- School of Medicine, University of California San Diego, 9500 Gilman Drive 0760, La Jolla, CA, 92093, USA
| | - Robert E Sinden
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK
| | - Esperanza Herreros
- Diseases of the Developing World (DDW), GlaxoSmithKline, 28760, Tres Cantos, Madrid, Spain
| | - Francisco J Gamo
- Diseases of the Developing World (DDW), GlaxoSmithKline, 28760, Tres Cantos, Madrid, Spain.
| | - Jake Baum
- Department of Life Sciences, Imperial College London, Sir Alexander Fleming Building, Exhibition Road, South Kensington, London, SW7 2AZ, UK.
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20
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Antimalarial Transmission-Blocking Interventions: Past, Present, and Future. Trends Parasitol 2018; 34:735-746. [PMID: 30082147 DOI: 10.1016/j.pt.2018.07.001] [Citation(s) in RCA: 47] [Impact Index Per Article: 7.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2018] [Revised: 06/14/2018] [Accepted: 07/02/2018] [Indexed: 12/17/2022]
Abstract
Malaria remains a major global health challenge. Appropriate use of current antimalarial tools has reduced the disease burden, but morbidity and mortality remain unacceptably high. It is widely accepted that, to achieve long-term control/eradication, it will be necessary to use interventions that inhibit the transmission of parasites to mosquitoes - these tools are termed transmission-blocking interventions (TBIs). This article aims to outline the rationale for the development of TBIs, with a focus on transmission-blocking drugs and (parasite-derived) transmission-blocking vaccines. We describe and summarise the current status of each of these intervention classes and attempt to identify future requirements in development, with a focus on the challenges of establishing each method within an integrated malarial control programme in the future.
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21
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Vandana, Singh AP, Singh J, Sharma R, Akhter M, Mishra PK, Saxena AK, Dixit R, Rathi B, Katyal A, Pandey KC. Biochemical characterization of unusual cysteine protease of P. falciparum, metacaspase-2 (MCA-2). Mol Biochem Parasitol 2018; 220:28-41. [PMID: 29317266 DOI: 10.1016/j.molbiopara.2018.01.001] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/26/2017] [Revised: 01/02/2018] [Accepted: 01/03/2018] [Indexed: 02/05/2023]
Abstract
Earlier studies on Plasmodium apoptosis revealed the presence of proteases with caspases like- activity, which are known as "metacaspases". Although this family of cysteine proteases is structurally similar to caspases with Cys-His dyad but their evolutionary significance and functional relevance remains largely unknown. These proteases are considered to be an important target against malaria due to their absence in humans. In this report, we have biochemically characterized metacaspase-2 (PfMCA-2) of P.falciparum. Enzymatic assay showed that PfMCA-2 efficiently cleaved arginine/lysine specific peptide, but not caspase-specific substrate. Consistently, PfMCA-2 activity was sensitive to effector caspases inhibitor, Z-FA-FMK, and mildly inhibited by aprotinin and E-64. However, general caspase inhibitors such as Z-VAD-FMK and Z-DEVD-FMK had no effect on PfMCA-2 activity. Z-FA-FMK inhibits parasite growth with an IC50 value of 2.7 μM along with the notable morphological changes. PfMCA-2 specifically expressed in schizonts and gametocyte stages and there was a notable depletion of PfMCA-2 expression in Z-FA-FMK treated schizonts and gametocytes stages of parasite. Notably, PfMCA-2 cleaves a phylogenetically conserved protein, TSN (Tudor staphylococcal nuclease) and the proteolysis of PfTSN did not occur after treatment with the Z-FA-FMK. The production of large amount of reactive oxygen species in presence of Z-FA-FMK caused oxidative stress which in turn leads to loss of cell viability. The oxidative stress further generates positive feedback for the occurrence of cell death in term of phosphatidylserine externalization and DNA fragmentation in vitro.
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Affiliation(s)
- Vandana
- National Institute of Malaria Research, New Delhi, 110077, India; Dr B. R. Ambedkar Centre for Biomedical Research, Delhi University, New Delhi, 110007, India
| | - Agam P Singh
- National Institute of Immunology, New Delhi, 110067, India
| | - Jitendra Singh
- Faculty of Pharmacy, Jamia Hamdard, New Delhi, 110062, India
| | - Ruby Sharma
- Jawaharlal Nehru University, New Delhi, 110067, India
| | - Mymoona Akhter
- Faculty of Pharmacy, Jamia Hamdard, New Delhi, 110062, India
| | - Pradyumna K Mishra
- National Institute for Research in Environmental Health, Bhopal 462001, India
| | - Ajay K Saxena
- Jawaharlal Nehru University, New Delhi, 110067, India
| | - Rajnikant Dixit
- National Institute of Malaria Research, New Delhi, 110077, India
| | - Brijesh Rathi
- Dept of Chemistry, Hans Raj College, Delhi University, India
| | - Anju Katyal
- Dr B. R. Ambedkar Centre for Biomedical Research, Delhi University, New Delhi, 110007, India
| | - Kailash C Pandey
- National Institute for Research in Environmental Health, Bhopal 462001, India.
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22
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Li H, Sun W, Huang X, Lu X, Patel PR, Kim M, Orr MJ, Fisher RM, Tanaka TQ, McKew JC, Simeonov A, Sanderson PE, Zheng W, Williamson KC, Huang W. Efficient Synthesis of 1,9-Substituted Benzo[h][1,6]naphthyridin-2(1H)-ones and Evaluation of their Plasmodium falciparum Gametocytocidal Activities. ACS COMBINATORIAL SCIENCE 2017; 19:748-754. [PMID: 29024590 DOI: 10.1021/acscombsci.7b00119] [Citation(s) in RCA: 6] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
A novel three-component, two-step, one-pot nucleophilic aromatic substitution (SNAr)-intramolecular cyclization-Suzuki coupling reaction was developed for the synthesis of benzo[h][1,6]naphthyridin-2(1H)-ones (Torins). On the basis of the new efficiently convergent synthetic route, a library of Torin analogs was synthesized. The antimalarial activities of these compounds were evaluated against asexual parasites using a growth inhibition assay and gametocytes using a viability assay.
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Affiliation(s)
- Hao Li
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Wei Sun
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Xiuli Huang
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Xiao Lu
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Paresma R. Patel
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Myunghoon Kim
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Meghan J. Orr
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Richard M. Fisher
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Takeshi Q Tanaka
- Laboratory
of Malaria and Vector Research, National Institute of Allergy and
Infectious Diseases, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - John C. McKew
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Anton Simeonov
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Philip E. Sanderson
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Wei Zheng
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
| | - Kim C. Williamson
- Department
of Biology, Loyola University Chicago, Chicago, Illinois 60660, United States
- Microbiology
and Immunology Department, Uniformed Services University of the Health Sciences, 4301 Jones Bridge Road, Bethesda, Maryland 20814, United States
| | - Wenwei Huang
- National
Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, Maryland 20892, United States
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23
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Sinha S, Sarma P, Sehgal R, Medhi B. Development in Assay Methods for in Vitro Antimalarial Drug Efficacy Testing: A Systematic Review. Front Pharmacol 2017; 8:754. [PMID: 29123481 PMCID: PMC5662882 DOI: 10.3389/fphar.2017.00754] [Citation(s) in RCA: 20] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/03/2017] [Accepted: 10/04/2017] [Indexed: 11/13/2022] Open
Abstract
The emergence and spread of drug resistance are the major challenges in malaria eradication mission. Besides various strategies laid down by World Health Organization, such as vector management, source reduction, early case detection, prompt treatment, and development of new diagnostics and vaccines, nevertheless the need for new and efficacious drugs against malaria has become a critical priority on the global malaria research agenda. At several screening stages, millions of compounds are screened (1,000–2,000,000 compounds per screening campaign), before pre-clinical trials to select optimum lead. Carrying out in vitro screening of antimalarials is very difficult as different assay methods are subject to numerous sources of variability across different laboratories around the globe. Despite this, in vitro screening is an essential part of antimalarial drug development as it enables to resource various confounding factors such as host immune response and drug–drug interaction. Therefore, in this article, we try to illustrate the basic necessity behind in vitro study and how new methods are developed and subsequently adopted for high-throughput antimalarial drug screening and its application in achieving the next level of in vitro screening based on the current approaches (such as stem cells).
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Affiliation(s)
- Shweta Sinha
- Department of Medical Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Phulen Sarma
- Department of Pharmacology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Rakesh Sehgal
- Department of Medical Parasitology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
| | - Bikash Medhi
- Department of Pharmacology, Postgraduate Institute of Medical Education and Research, Chandigarh, India
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Sun W, Huang X, Li H, Tawa G, Fisher E, Tanaka TQ, Shinn P, Huang W, Williamson KC, Zheng W. Novel lead structures with both Plasmodium falciparum gametocytocidal and asexual blood stage activity identified from high throughput compound screening. Malar J 2017; 16:147. [PMID: 28407766 PMCID: PMC5390467 DOI: 10.1186/s12936-017-1805-0] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2016] [Accepted: 04/06/2017] [Indexed: 12/31/2022] Open
Abstract
BACKGROUND Blocking malaria transmission is an important step in eradicating malaria. In the field, transmission requires the production of sexual stage Plasmodium parasites, called gametocytes, which are not effectively killed by the commonly used anti-malarials allowing individuals to remain infectious after clearance of asexual parasites. METHODS To identify new gametocytocidal compounds, a library of 45,056 compounds with diverse structures was screened using a high throughput gametocyte viability assay. The characteristics of active hits were further evaluated against asexual stage parasites in a growth inhibition assay. Their cytotoxicity were tested against mammalian cells in a cytotoxicity assay. The chemical scaffold similarity of active hits were studied using scaffold cluster analysis. RESULTS A set of 23 compounds were identified and further confirmed for their activity against gametocytes. All the 23 confirmed compounds possess dual-activities against both gametocytes responsible for human to mosquito transmission and asexual parasites that cause the clinical symptoms. Three of these compounds were fourfold more active against gametocytes than asexual parasites. Further cheminformatic analysis revealed three sets of novel scaffolds, including highly selective 4-1H-pyrazol-5-yl piperidine analogs. CONCLUSIONS This study revealed important new structural scaffolds that can be used as starting points for dual activity anti-malarial drug development.
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Affiliation(s)
- Wei Sun
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
| | - Xiuli Huang
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
| | - Hao Li
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
| | - Gregory Tawa
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
| | - Ethan Fisher
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
| | - Takeshi Q. Tanaka
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, Bethesda, MD USA
| | - Paul Shinn
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
| | - Wenwei Huang
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
| | - Kim C. Williamson
- Department of Microbiology and Immunology, Uniformed Services University of the Health Sciences, Bethesda, MD 20814 USA
| | - Wei Zheng
- National Center for Advancing Translational Sciences, National Institutes of Health, 9800 Medical Center Drive, Bethesda, MD 20892 USA
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25
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Siciliano G, Santha Kumar TR, Bona R, Camarda G, Calabretta MM, Cevenini L, Davioud-Charvet E, Becker K, Cara A, Fidock DA, Alano P. A high susceptibility to redox imbalance of the transmissible stages of Plasmodium falciparum revealed with a luciferase-based mature gametocyte assay. Mol Microbiol 2017; 104:306-318. [PMID: 28118506 DOI: 10.1111/mmi.13626] [Citation(s) in RCA: 25] [Impact Index Per Article: 3.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 01/17/2017] [Indexed: 12/18/2022]
Abstract
The goal to prevent Plasmodium falciparum transmission from humans to mosquitoes requires the identification of targetable metabolic processes in the mature (stage V) gametocytes, the sexual stages circulating in the bloodstream. This task is complicated by the apparently low metabolism of these cells, which renders them refractory to most antimalarial inhibitors and constrains the development of specific and sensitive cell-based assays. Here, we identify and functionally characterize the regulatory regions of the P. falciparum gene PF3D7_1234700, encoding a CPW-WPC protein and named here Upregulated in Late Gametocytes (ULG8), which we have leveraged to express reporter genes in mature male and female gametocytes. Using transgenic parasites containing a pfULG8-luciferase cassette, we investigated the susceptibility of stage V gametocytes to compounds specifically affecting redox metabolism. Our results reveal a high sensitivity of mature gametocytes to the glutathione reductase inhibitor and redox cycler drug methylene blue (MB). Using isobologram analysis, we find that a concomitant inhibition of the parasite enzyme glucose-6-phosphate dehydrogenase-6-phosphogluconolactonase, a key component of NADPH synthesis, potently synergizes MB activity. These data suggest that redox metabolism and detoxification activity play an unsuspected yet vital role in stage V gametocytes, rendering these cells exquisitely sensitive to decreases in NADPH concentration.
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Affiliation(s)
- Giulia Siciliano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Rome, Italy
| | - T R Santha Kumar
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA
| | - Roberta Bona
- Dipartimento Farmaco, Istituto Superiore di Sanità, Rome, Italy
| | - Grazia Camarda
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Rome, Italy
| | | | - Luca Cevenini
- Department of Chemistry "G. Ciamician", University of Bologna, Bologna, Italy
| | - Elisabeth Davioud-Charvet
- European School of Chemistry, Polymers and Materials (ECPM), UMR 7509 Centre National de la Recherche Scientifique and University of Strasbourg, Strasbourg, France
| | - Katja Becker
- Biochemistry and Molecular Biology, Interdisciplinary Research Center, Justus Liebig University Giessen, Germany
| | - Andrea Cara
- Dipartimento Farmaco, Istituto Superiore di Sanità, Rome, Italy
| | - David A Fidock
- Department of Microbiology and Immunology, Columbia University Medical Center, New York, NY, USA.,Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, NY, USA
| | - Pietro Alano
- Dipartimento di Malattie Infettive, Parassitarie ed Immunomediate, Istituto Superiore di Sanità, Rome, Italy
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26
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Abstract
A portable kinetics fluorometer is developed to detect viable cells which may be contaminating various samples. The portable device acts as a single-excitation, single-emission photometer that continuously measures fluorescence intensity of an indicator dye and plots it. The slope of the plot depends on the number of colony forming units per milliliter. The device uses resazurin as the indicator dye. Viable cells reduce resazurin to resorufin, which is more fluorescent. Photodiode is used to detect fluorescence change. The photodiode generated current proportional to the intensity of the light that reached it, and an op-amp is used in a transimpedance differential configuration to ensure amplification of the photodiode's signal. A microfluidic chip is designed specifically for the device. It acts as a fully enclosed cuvette, which enhances the resazurin reduction rate. In tests, the E. coli-containing media are injected into the microfluidic chip and the device is able to detect the presence of E. coli in LB media based on the fluorescence change that occurred in the indicator dye. The device provides fast, accurate, and inexpensive means to optical detection of the presence of viable cells and could be used in the field in place of more complex methods, i.e., loop-meditated isothermal amplification of DNA (LAMP) to detect bacteria in pharmaceutical samples (Jimenez et al., J Microbiol Methods 41(3):259-265, 2000) or measuring the intrinsic fluorescence of the bacterial or yeast chromophores (Estes et al., Biosens Bioelectron 18(5):511-519, 2003).
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27
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Tarkang PA, Appiah-Opong R, Ofori MF, Ayong LS, Nyarko AK. Application of multi-target phytotherapeutic concept in malaria drug discovery: a systems biology approach in biomarker identification. Biomark Res 2016; 4:25. [PMID: 27999673 PMCID: PMC5154004 DOI: 10.1186/s40364-016-0077-0] [Citation(s) in RCA: 17] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/08/2016] [Accepted: 11/29/2016] [Indexed: 01/20/2023] Open
Abstract
There is an urgent need for new anti-malaria drugs with broad therapeutic potential and novel mode of action, for effective treatment and to overcome emerging drug resistance. Plant-derived anti-malarials remain a significant source of bioactive molecules in this regard. The multicomponent formulation forms the basis of phytotherapy. Mechanistic reasons for the poly-pharmacological effects of plants constitute increased bioavailability, interference with cellular transport processes, activation of pro-drugs/deactivation of active compounds to inactive metabolites and action of synergistic partners at different points of the same signaling cascade. These effects are known as the multi-target concept. However, due to the intrinsic complexity of natural products-based drug discovery, there is need to rethink the approaches toward understanding their therapeutic effect. This review discusses the multi-target phytotherapeutic concept and its application in biomarker identification using the modified reverse pharmacology - systems biology approach. Considerations include the generation of a product library, high throughput screening (HTS) techniques for efficacy and interaction assessment, High Performance Liquid Chromatography (HPLC)-based anti-malarial profiling and animal pharmacology. This approach is an integrated interdisciplinary implementation of tailored technology platforms coupled to miniaturized biological assays, to track and characterize the multi-target bioactive components of botanicals as well as identify potential biomarkers. While preserving biodiversity, this will serve as a primary step towards the development of standardized phytomedicines, as well as facilitate lead discovery for chemical prioritization and downstream clinical development.
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Affiliation(s)
- Protus Arrey Tarkang
- Centre for Research on Medicinal Plants and Traditional Medicine, Institute of Medical Research and Medicinal Plants Studies (IMPM), P. O. Box 8013, Yaoundé, Cameroon
- Department of Clinical Pathology, Noguchi Memorial Institute for Medical Research, University of Ghana, P. O. Box LG 581, Legon, Accra Ghana
| | - Regina Appiah-Opong
- Department of Clinical Pathology, Noguchi Memorial Institute for Medical Research, University of Ghana, P. O. Box LG 581, Legon, Accra Ghana
| | - Michael F. Ofori
- Department of Immunology, Noguchi Memorial Institute for Medical Research, University of Ghana, P. O. Box LG581, Legon, Accra Ghana
| | - Lawrence S. Ayong
- Malaria Research Laboratory, Centre Pasteur Cameroon, BP 1274 Yaoundé, Cameroon
| | - Alexander K. Nyarko
- Department of Clinical Pathology, Noguchi Memorial Institute for Medical Research, University of Ghana, P. O. Box LG 581, Legon, Accra Ghana
- School of Pharmacy, University of Ghana, P.O. Box LG43, Legon, Accra Ghana
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28
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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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29
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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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30
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Patel PR, Sun W, Kim M, Huang X, Sanderson PE, Tanaka TQ, McKew JC, Simeonov A, Williamson KC, Zheng W, Huang W. In vitro evaluation of imidazo[4,5-c]quinolin-2-ones as gametocytocidal antimalarial agents. Bioorg Med Chem Lett 2016; 26:2907-2911. [PMID: 27156776 DOI: 10.1016/j.bmcl.2016.04.045] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2016] [Revised: 04/15/2016] [Accepted: 04/16/2016] [Indexed: 11/30/2022]
Abstract
Novel imidazo[4,5-c]quinolin-2-ones were synthesized and evaluated in asexual blood stage and late stage gametocyte assays of Plasmodium falciparum, a major causative agent of malaria. The design of these compounds is based on a recently identified lead compound from a high throughput screen. A concise synthesis was developed that allowed for generation of analogues with substitution around both the quinoline and imidazolidinone rings. Through structure-activity relationship studies, a number of potent compounds were identified that possessed excellent antimalarial activity against both the asexual and sexual stages with minimal cytotoxicity in mammalian cells. This is the first Letter describing SAR and gametocytocidal activity of imidazo[4,5-c]quinolin-2-ones, a new lead series for malaria treatment and prevention.
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Affiliation(s)
- Paresma R Patel
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Wei Sun
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Myunghoon Kim
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Xiuli Huang
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Philip E Sanderson
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Takeshi Q Tanaka
- Department of Biology, Loyola University Chicago, Chicago, IL 60660, United States
| | - John C McKew
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Anton Simeonov
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Kim C Williamson
- Department of Biology, Loyola University Chicago, Chicago, IL 60660, United States
| | - Wei Zheng
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States
| | - Wenwei Huang
- National Center for Advancing Translational Sciences, National Institutes of Health, Bethesda, MD 20892, United States.
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31
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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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32
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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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33
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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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34
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Amoah LE, Kakaney C, Kwansa-Bentum B, Kusi KA. Activity of Herbal Medicines on Plasmodium falciparum Gametocytes: Implications for Malaria Transmission in Ghana. PLoS One 2015; 10:e0142587. [PMID: 26562778 PMCID: PMC4642932 DOI: 10.1371/journal.pone.0142587] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/22/2015] [Accepted: 10/23/2015] [Indexed: 12/17/2022] Open
Abstract
Background Malaria still remains a major health issue in Ghana despite the introduction of Artemisinin-based combination therapy (ACT) coupled with other preventative measures such as the use of insecticide treated nets (ITNs). The global quest for eradication of malaria has heightened the interest of identifying drugs that target the sexual stage of the parasite, referred to as transmission-blocking drugs. This study aimed at assessing the efficacy and gametocydal effects of some commonly used herbal malaria products in Ghana. Methodology/Principal Findings After identifying herbal anti-malarial products frequently purchased on the Ghanaian market, ten of them were selected and lyophilized. In vitro drug sensitivity testing of different concentrations of the herbal products was carried out on asexual and in vitro generated gametocytes of the 3D7 strain of Plasmodium falciparum. The efficacies of the products were assessed by microscopy. Cultures containing low dose of RT also produced the least number of late stage gametocytes. Two of the herbal products CM and RT inhibited the growth of late stage gametocytes by > 80% at 100 μg/ml whilst KG was the most inhibitory to early stage gametocytes at that same concentration. However at 1 μg/ml, only YF significantly inhibited the survival of late stage gametocytes although at that same concentration YF barely inhibited the survival of early stage gametocytes. Conclusions/Significance Herbal product RT (Aloe schweinfurthii, Khaya senegalensis, Piliostigma thonningii and Cassia siamea) demonstrated properties of a highly efficacious gametocydal product. Low dose of herbal product RT exhibited the highest gametocydal activity and at 100 μg/ml, RT exhibited >80% inhibition of late stage gametocytes. However inhibition of asexual stage parasite by RT was not optimal. Improving the asexual inhibition of RT could convert RT into an ideal antimalarial herbal product. We also found that generally C. sanguinolenta containing herbal products exhibited gametocydal activity in addition to high asexual efficacy. Herbal products with high gametocydal activity can help in the fight to reduce malaria transmission.
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Affiliation(s)
- Linda Eva Amoah
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
| | - Courage Kakaney
- Department of Animal Biology and Conservation Science, College of Basic and Applied Sciences, University of Ghana, Legon, Ghana
| | - Bethel Kwansa-Bentum
- Department of Animal Biology and Conservation Science, College of Basic and Applied Sciences, University of Ghana, Legon, Ghana
| | - Kwadwo Asamoah Kusi
- Department of Immunology, Noguchi Memorial Institute for Medical Research, College of Health Sciences, University of Ghana, Legon, Ghana
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35
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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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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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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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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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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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40
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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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41
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Potent Plasmodium falciparum gametocytocidal activity of diaminonaphthoquinones, lead antimalarial chemotypes identified in an antimalarial compound screen. Antimicrob Agents Chemother 2014; 59:1389-97. [PMID: 25512421 DOI: 10.1128/aac.01930-13] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/07/2023] Open
Abstract
Forty percent of the world's population is threatened by malaria, which is caused by Plasmodium parasites and results in an estimated 200 million clinical cases and 650,000 deaths each year. Drug resistance has been reported for all commonly used antimalarials and has prompted screens to identify new drug candidates. However, many of these new candidates have not been evaluated against the parasite stage responsible for transmission, gametocytes. If Plasmodium falciparum gametocytes are not eliminated, patients continue to spread malaria for weeks after asexual parasite clearance. Asymptomatic individuals can also harbor gametocyte burdens sufficient for transmission, and a safe, effective gametocytocidal agent could also be used in community-wide malaria control programs. Here, we identify 15 small molecules with nanomolar activity against late-stage gametocytes. Fourteen are diaminonaphthoquinones (DANQs), and one is a 2-imino-benzo[d]imidazole (IBI). One of the DANQs identified, SJ000030570, is a lead antimalarial candidate. In contrast, 94% of the 650 compounds tested are inactive against late-stage gametocytes. Consistent with the ineffectiveness of most approved antimalarials against gametocytes, of the 19 novel compounds with activity against known anti-asexual-stage targets, only 3 had any strong effect on gametocyte viability. These data demonstrate the distinct biology of the transmission stages and emphasize the importance of screening for gametocytocidal activity. The potent gametocytocidal activity of DANQ and IBI coupled with their efficacy against asexual parasites provides leads for the development of antimalarials with the potential to prevent both the symptoms and the spread of malaria.
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42
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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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43
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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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44
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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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45
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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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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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Suganuma K, Allamanda P, Hakimi H, Zhou M, Angeles JM, Kawazu SI, Inoue N. Establishment of ATP-based luciferase viability assay in 96-well plate for Trypanosoma congolense. J Vet Med Sci 2014; 76:1437-41. [PMID: 25056575 PMCID: PMC4272975 DOI: 10.1292/jvms.14-0273] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/22/2022] Open
Abstract
Animal African trypanosomosis (AAT), caused by Trypanosoma congolense, is widespread throughout sub-Saharan Africa. There are significant concerns related to the current drugs available for the treatment of AAT due to their limited effectiveness across species and their adverse effects. Moreover, drug resistant trypanosomes have recently been reported in the field. High throughput screening (HTS) of large chemical compound library collections is a promising approach for identifying novel drug candidates. While HTS for Trypanozoon trypanosomes, T. brucei sspp. and T. evansi is well established, no assays have been developed for T. congolense. In the present study, the authors developed an ATP-based luciferase viability assay for T. congolense in a 96-well plate format. The calculated 50% inhibitory concentration (IC50) values for pentamidine and diminazene were 10-100 times higher in T. congolense than in T. brucei. This result suggests that the transporters for the 2 tested compounds differ between T. congolense and T. brucei. This assay could further be applied to screen novel chemical compounds for the treatment of AAT caused by T. congolense.
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Affiliation(s)
- Keisuke Suganuma
- National Research Center for Protozoan Diseases, Obihiro University of Agriculture and Veterinary Medicine, Inada, Obihiro, Hokkaido 080-8555, Japan
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48
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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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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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50
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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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