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Rufino-Moya PJ, Zafra Leva R, Martínez-Moreno Á, Buffoni L, Valderas García E, Pérez Arévalo J, Molina-Hernández V, Ruiz-Campillo MT, Herrera-Torres G, Martínez-Moreno FJ. Advancement in Diagnosis, Treatment, and Vaccines against Fasciola hepatica: A Comprehensive Review. Pathogens 2024; 13:669. [PMID: 39204269 PMCID: PMC11357060 DOI: 10.3390/pathogens13080669] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/28/2024] [Revised: 07/30/2024] [Accepted: 08/06/2024] [Indexed: 09/03/2024] Open
Abstract
In this review article, we aim to provide an overview of fasciolosis in ruminants. Diagnosis through new coprological methods (such as Flukefinder®, FLOTAC®, and Mini-FLOTAC®) remains the most suitable approach for farms. Regarding treatment, there is a scarcity of available drugs, and resistance to them has prompted new approaches (including drug combinations, enhanced metabolism, or the use of natural compounds) to address this issue. Additionally, several researchers have developed vaccines to control the disease, but their efficacy varies, and none are currently sufficient for commercial use. Further studies are needed to better understand all aspects discussed in this manuscript, with the goal of improving diagnosis, treatment, and disease control. It is important to note that this manuscript does not delve into in-depth knowledge of the discussed aspects; rather, it provides an overview of the different methodologies related to these three aspects of parasitic disease.
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Affiliation(s)
- Pablo José Rufino-Moya
- Animal Health Department (Parasitology and Parasitic Diseases), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (P.J.R.-M.); (Á.M.-M.); (L.B.P.); (E.V.G.); (F.J.M.-M.)
| | - Rafael Zafra Leva
- Animal Health Department (Parasitology and Parasitic Diseases), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (P.J.R.-M.); (Á.M.-M.); (L.B.P.); (E.V.G.); (F.J.M.-M.)
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
| | - Álvaro Martínez-Moreno
- Animal Health Department (Parasitology and Parasitic Diseases), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (P.J.R.-M.); (Á.M.-M.); (L.B.P.); (E.V.G.); (F.J.M.-M.)
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
| | - Leandro Buffoni
- Animal Health Department (Parasitology and Parasitic Diseases), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (P.J.R.-M.); (Á.M.-M.); (L.B.P.); (E.V.G.); (F.J.M.-M.)
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
| | - Elora Valderas García
- Animal Health Department (Parasitology and Parasitic Diseases), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (P.J.R.-M.); (Á.M.-M.); (L.B.P.); (E.V.G.); (F.J.M.-M.)
- Departamento de Sanidad Animal, Facultad de Veterinaria, Universidad de León, 24004 León, Spain
| | - José Pérez Arévalo
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
- Department of Anatomy, Comparative Pathology and Toxicology, Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain
| | - Verónica Molina-Hernández
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
- Department of Anatomy, Comparative Pathology and Toxicology, Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain
| | - María T. Ruiz-Campillo
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
- Department of Anatomy, Comparative Pathology and Toxicology, Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain
| | - Guillem Herrera-Torres
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
- Department of Anatomy, Comparative Pathology and Toxicology, Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain
| | - Francisco J. Martínez-Moreno
- Animal Health Department (Parasitology and Parasitic Diseases), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (P.J.R.-M.); (Á.M.-M.); (L.B.P.); (E.V.G.); (F.J.M.-M.)
- UIC Zoonosis y Enfermedades Emergentes (ENZOEM), Faculty of Veterinary Medicine, University of Córdoba, Sanidad Animal Building, Rabanales Campus, 14014 Córdoba, Spain; (J.P.A.); (V.M.-H.); (M.T.R.-C.); (G.H.-T.)
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2
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Ponomarev D, Lvova M, Mordvinov V, Chidunchi I, Dushkin A, Avgustinovich D. Anti-Opisthorchis felineus effects of artemisinin derivatives: An in vitro study. Acta Trop 2024; 254:107196. [PMID: 38521124 DOI: 10.1016/j.actatropica.2024.107196] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2024] [Revised: 03/11/2024] [Accepted: 03/20/2024] [Indexed: 03/25/2024]
Abstract
BACKGROUND The drug of choice for the treatment of opisthorchiasis caused by trematodes Opisthorchis viverrini and O. felineus is praziquantel (PZQ), but there is a constant search for new anthelmintics, including those of plant origin. Positive results on the use of artemisinin derivatives against O. viverrini opisthorchiasis have been shown previously, but the effect of these compounds on O. felineus has not been studied. Therefore, here, a comparative analysis of anthelmintic properties of artemisinin derivatives (artesunate [AS], artemether [AM], and dihydroartemisinin [DHA]) was carried out in vitro in relation to PZQ. Experiments were performed on newly excysted metacercariae (NEMs) and adult flukes of O. felineus. RESULTS Dose- and time-dependent effects of artemisinin derivatives and of PZQ were assessed in terms of motility and mortality of both NEMs and adult flukes. The most pronounced anthelmintic action was exerted by DHA, whose half-maximal inhibitory concentrations (IC50) of 1.9 (NEMs) and 2.02 µg/mL (adult flukes) were lower than those of PZQ (0.56 and 0.25 µg/mL, respectively). In contrast to PZQ, the effects of DHA and AS were similar when we compared the two developmental stages of O. felineus (NEMs and adult flukes). In addition, AM, AS, and especially DHA at doses of 100 µg/mL disrupted tegument integrity in adult flukes, which was not observed with PZQ. CONCLUSIONS Artemisinin derivatives (AS, AM, and DHA) have good anthelmintic efficacy against the trematode O. felineus, and the action of these substances is comparable to (and sometimes better than) the effects of PZQ.
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Affiliation(s)
- Denis Ponomarev
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences (SB RAS), Prospekt Akad. Lavrentyeva 10, Novosibirsk, 630090, Russia.
| | - Maria Lvova
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences (SB RAS), Prospekt Akad. Lavrentyeva 10, Novosibirsk, 630090, Russia
| | - Viatcheslav Mordvinov
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences (SB RAS), Prospekt Akad. Lavrentyeva 10, Novosibirsk, 630090, Russia
| | - Irina Chidunchi
- Toraighyrov University, Lomov Str. 64, Pavlodar, 140000, Kazakhstan
| | - Alexander Dushkin
- Institute of Solid State Chemistry and Mechanochemistry, SB RAS, Kutateladze Str. 18, Novosibirsk, 630090, Russia
| | - Damira Avgustinovich
- Institute of Cytology and Genetics, Siberian Branch of Russian Academy of Sciences (SB RAS), Prospekt Akad. Lavrentyeva 10, Novosibirsk, 630090, Russia; Institute of Solid State Chemistry and Mechanochemistry, SB RAS, Kutateladze Str. 18, Novosibirsk, 630090, Russia
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Rinaldi G, Paz Meseguer C, Cantacessi C, Cortés A. Form and Function in the Digenea, with an Emphasis on Host-Parasite and Parasite-Bacteria Interactions. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2024; 1454:3-45. [PMID: 39008262 DOI: 10.1007/978-3-031-60121-7_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/16/2024]
Abstract
This review covers the general aspects of the anatomy and physiology of the major body systems in digenetic trematodes, with an emphasis on new knowledge of the area acquired since the publication of the second edition of this book in 2019. In addition to reporting on key recent advances in the morphology and physiology of tegumentary, sensory, neuromuscular, digestive, excretory, and reproductive systems, and their roles in host-parasite interactions, this edition includes a section discussing the known and putative roles of bacteria in digenean biology and physiology. Furthermore, a brief discussion of current trends in the development of novel treatment and control strategies based on a better understanding of the trematode body systems and associated bacteria is provided.
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Affiliation(s)
- Gabriel Rinaldi
- Department of Life Sciences, Edward Llwyd Building, Aberystwyth University, Aberystwyth, UK
| | - Carla Paz Meseguer
- Department of Pharmacy and Pharmaceutical Technology and Parasitology, School of Pharmacy and Food Sciences, Universitat de València, Valencia, Spain
| | - Cinzia Cantacessi
- Department of Veterinary Medicine, University of Cambridge, Cambridge, UK
| | - Alba Cortés
- Department of Pharmacy and Pharmaceutical Technology and Parasitology, School of Pharmacy and Food Sciences, Universitat de València, Valencia, Spain.
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Buskes M, Clements M, Bachovchin KA, Jalani HB, Leonard A, Bag S, Klug DM, Singh B, Campbell RF, Sciotti RJ, El-Sakkary N, Caffrey CR, Pollastri MP, Ferrins L. Structure-Bioactivity Relationships of Lapatinib Derived Analogs against Schistosoma mansoni. ACS Med Chem Lett 2020; 11:258-265. [PMID: 32184954 PMCID: PMC7073886 DOI: 10.1021/acsmedchemlett.9b00455] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/01/2019] [Accepted: 01/10/2020] [Indexed: 11/30/2022] Open
Abstract
We recently reported a series of compounds for a solubility-driven optimization campaign of antitrypanosomal compounds. Extending a parasite-hopping approach to the series, a subset of compounds from this library has been cross-screened for activity against the metazoan flatworm parasite, Schistosoma mansoni. This study reports the identification and preliminary development of several potently bioactive compounds against adult schistosomes, one or more of which represent promising leads for further assessment and optimization.
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Affiliation(s)
- Melissa
J. Buskes
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Monica Clements
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Kelly A. Bachovchin
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Hitesh B. Jalani
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Allison Leonard
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Seema Bag
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Dana M. Klug
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Baljinder Singh
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Robert F. Campbell
- Experimental
Therapeutics, Walter Reed Army Institute
of Research, 2460 Linden Lane, Silver Spring, Maryland 20910, United
States
| | - Richard J. Sciotti
- Experimental
Therapeutics, Walter Reed Army Institute
of Research, 2460 Linden Lane, Silver Spring, Maryland 20910, United
States
| | - Nelly El-Sakkary
- Center
for Discovery and Innovation in Parasitic Diseases, Skaggs School
of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, United States
| | - Conor R. Caffrey
- Center
for Discovery and Innovation in Parasitic Diseases, Skaggs School
of Pharmacy and Pharmaceutical Sciences, University of California, San Diego, La Jolla, California 92093, United States
| | - Michael P. Pollastri
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
| | - Lori Ferrins
- Department
of Chemistry and Chemical Biology, Northeastern
University, Boston, Massachusetts 02115, United States
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5
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Form and Function in the Digenea. ADVANCES IN EXPERIMENTAL MEDICINE AND BIOLOGY 2019; 1154:3-20. [DOI: 10.1007/978-3-030-18616-6_1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/26/2022]
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6
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Singh R, Beasley R, Long T, Caffrey CR. Algorithmic Mapping and Characterization of the Drug-Induced Phenotypic-Response Space of Parasites Causing Schistosomiasis. IEEE/ACM TRANSACTIONS ON COMPUTATIONAL BIOLOGY AND BIOINFORMATICS 2018; 15:469-481. [PMID: 27071187 PMCID: PMC5915339 DOI: 10.1109/tcbb.2016.2550444] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/11/2023]
Abstract
Neglected tropical diseases, especially those caused by helminths, constitute some of the most common infections of the world's poorest people. Amongst these, schistosomiasis (bilharzia or 'snail fever'), caused by blood flukes of the genus Schistosoma, ranks second only to malaria in terms of human impact: two hundred million people are infected and close to 800 million are at risk of infection. Drug screening against helminths poses unique challenges: the parasite cannot be cloned and is difficult to target using gene knockouts or RNAi. Consequently, both lead identification and validation involve phenotypic screening, where parasites are exposed to compounds whose effects are determined through the analysis of the ensuing phenotypic responses. The efficacy of leads thus identified derives from one or more or even unknown molecular mechanisms of action. The two most immediate and significant challenges that confront the state-of-the-art in this area are: the development of automated and quantitative phenotypic screening techniques and the mapping and quantitative characterization of the totality of phenotypic responses of the parasite. In this paper, we investigate and propose solutions for the latter problem in terms of the following: (1) mathematical formulation and algorithms that allow rigorous representation of the phenotypic response space of the parasite, (2) application of graph-theoretic and network analysis techniques for quantitative modeling and characterization of the phenotypic space, and (3) application of the aforementioned methodology to analyze the phenotypic space of S. mansoni - one of the etiological agents of schistosomiasis, induced by compounds that target its polo-like kinase 1 (PLK 1) gene - a recently validated drug target. In our approach, first, bio-image analysis algorithms are used to quantify the phenotypic responses of different drugs. Next, these responses are linearly mapped into a low- dimensional space using Principle Component Analysis (PCA). The phenotype space is modeled using neighborhood graphs which are used to represent the similarity amongst the phenotypes. These graphs are characterized and explored using network analysis algorithms. We present a number of results related to both the nature of the phenotypic space of the S. mansoni parasite as well as algorithmic issues encountered in constructing and analyzing the phenotypic-response space. In particular, the phenotype distribution of the parasite was found to have a distinct shape and topology. We have also quantitatively characterized the phenotypic space by varying critical model parameters. Finally, these maps of the phenotype space allows visualization and reasoning about complex relationships between putative drugs and their system-wide effects and can serve as a highly efficient paradigm for assimilating and unifying information from phenotypic screens both during lead identification and lead optimization.
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7
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Bibo-Verdugo B, Jiang Z, Caffrey CR, O'Donoghue AJ. Targeting proteasomes in infectious organisms to combat disease. FEBS J 2017; 284:1503-1517. [PMID: 28122162 DOI: 10.1111/febs.14029] [Citation(s) in RCA: 35] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/25/2016] [Revised: 12/21/2016] [Accepted: 01/23/2017] [Indexed: 01/04/2023]
Abstract
Proteasomes are multisubunit, energy-dependent, proteolytic complexes that play an essential role in intracellular protein turnover. They are present in eukaryotes, archaea, and in some actinobacteria species. Inhibition of proteasome activity has emerged as a powerful strategy for anticancer therapy and three drugs have been approved for treatment of multiple myeloma. These compounds react covalently with a threonine residue located in the active site of a proteasome subunit to block protein degradation. Proteasomes in pathogenic organisms such as Mycobacterium tuberculosis and Plasmodium falciparum also have a nucleophilic threonine residue in the proteasome active site and are therefore sensitive to these anticancer drugs. This review summarizes efforts to validate the proteasome in pathogenic organisms as a therapeutic target. We describe several strategies that have been used to develop inhibitors with increased potency and selectivity for the pathogen proteasome relative to the human proteasome. In addition, we highlight a cell-based chemical screening approach that identified a potent, allosteric inhibitor of proteasomes found in Leishmania and Trypanosoma species. Finally, we discuss the development of proteasome inhibitors as anti-infective agents.
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Affiliation(s)
- Betsaida Bibo-Verdugo
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.,Center for Discovery and Innovation in Parasitic Diseases, University of California San Diego, La Jolla, CA, USA
| | - Zhenze Jiang
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.,Chemistry & Biochemistry Graduate Program, University of California San Diego, La Jolla, CA, USA
| | - Conor R Caffrey
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.,Center for Discovery and Innovation in Parasitic Diseases, University of California San Diego, La Jolla, CA, USA
| | - Anthony J O'Donoghue
- Skaggs School of Pharmacy and Pharmaceutical Sciences, University of California San Diego, La Jolla, CA, USA.,Center for Discovery and Innovation in Parasitic Diseases, University of California San Diego, La Jolla, CA, USA
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8
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Utzinger J, Becker SL, van Lieshout L, van Dam GJ, Knopp S. New diagnostic tools in schistosomiasis. Clin Microbiol Infect 2015; 21:529-42. [PMID: 25843503 DOI: 10.1016/j.cmi.2015.03.014] [Citation(s) in RCA: 181] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2015] [Revised: 03/21/2015] [Accepted: 03/21/2015] [Indexed: 12/22/2022]
Abstract
Schistosomiasis is a water-based parasitic disease that affects over 250 million people. Control efforts have long been in vain, which is one reason why schistosomiasis is considered a neglected tropical disease. However, since the new millennium, interventions against schistosomiasis are escalating. The initial impetus stems from a 2001 World Health Assembly resolution, urging member states to scale-up deworming of school-aged children with the anthelminthic drug praziquantel. Because praziquantel is safe, efficacious and inexpensive when delivered through the school platform, diagnosis before drug intervention was deemed unnecessary and not cost-effective. Hence, there was little interest in research and development of novel diagnostic tools. With the recent publication of the World Health Organization (WHO) Roadmap to overcome the impact of neglected tropical diseases in 2020, we have entered a new era. Elimination of schistosomiasis has become the buzzword and this has important ramifications for diagnostic tools. Indeed, measuring progress towards the WHO Roadmap and whether local elimination has been achieved requires highly accurate diagnostic assays. Here, we introduce target product profiles for diagnostic tools that are required for different stages of a schistosomiasis control programme. We provide an update of the latest developments in schistosomiasis diagnosis, including microscopic techniques, rapid diagnostic tests for antigen detection, polymerase chain reaction (PCR) assays and proxy markers for morbidity assessments. Particular emphasis is placed on challenges and solutions for new technologies to enter clinical practice.
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Affiliation(s)
- J Utzinger
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland.
| | - S L Becker
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland; Institute of Medical Microbiology and Hygiene, Saarland University Medical Centre, Homburg/Saar, Germany
| | - L van Lieshout
- Department of Parasitology, Leiden University Medical Centre, Leiden, The Netherlands
| | - G J van Dam
- Department of Parasitology, Leiden University Medical Centre, Leiden, The Netherlands
| | - S Knopp
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland; University of Basel, Basel, Switzerland; Department of Life Sciences, Natural History Museum, London, UK
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9
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Panic G, Duthaler U, Speich B, Keiser J. Repurposing drugs for the treatment and control of helminth infections. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2014; 4:185-200. [PMID: 25516827 PMCID: PMC4266803 DOI: 10.1016/j.ijpddr.2014.07.002] [Citation(s) in RCA: 118] [Impact Index Per Article: 11.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 04/16/2014] [Revised: 07/04/2014] [Accepted: 07/13/2014] [Indexed: 01/01/2023]
Abstract
Drug repurposing continues to be the central drug discovery strategy for helminths. Most repurposed drugs come from veterinary medicine and known drug classes. Only a handful of drugs have advanced clinically. More collaborations and funding are needed to advance discoveries to the market.
Helminth infections are responsible for a considerable public health burden, yet the current drug armamentarium is small. Given the high cost of drug discovery and development, the high failure rates and the long duration to develop novel treatments, drug repurposing circumvents these obstacles by finding new uses for compounds other than those they were initially intended to treat. In the present review, we summarize in vivo and clinical trial findings testing clinical candidates and marketed drugs against schistosomes, food-borne trematodes, soil-transmitted helminths, Strongyloides stercoralis, the major human filariases lymphatic filariasis and onchocerciasis, taeniasis, neurocysticercosis and echinococcosis. While expanding the applications of broad-spectrum or veterinary anthelmintics continues to fuel alternative treatment options, antimalarials, antibiotics, antiprotozoals and anticancer agents appear to be producing fruitful results as well. The trematodes and nematodes continue to be most investigated, while cestodal drug discovery will need to be accelerated. The most clinically advanced drug candidates include the artemisinins and mefloquine against schistosomiasis, tribendimidine against liver flukes, oxantel pamoate against trichuriasis, and doxycycline against filariasis. Preclinical studies indicate a handful of promising future candidates, and are beginning to elucidate the broad-spectrum activity of some currently used anthelmintics. Challenges and opportunities are further discussed.
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Affiliation(s)
| | | | | | - Jennifer Keiser
- Corresponding author. Address: Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002 Basel, Switzerland. Tel.: +41 61 284 8218; fax: +41 61 284 8105.
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10
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Taman A, Azab M. Present-day anthelmintics and perspectives on future new targets. Parasitol Res 2014; 113:2425-33. [PMID: 24894082 DOI: 10.1007/s00436-014-3969-7] [Citation(s) in RCA: 35] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2014] [Accepted: 05/25/2014] [Indexed: 12/29/2022]
Abstract
In absence of vaccines for the majority of helminths, chemotherapy is still the mainstay for controlling human helminthiases. However, a limited number of drugs are available in the market to combat parasitic helminths in human. Besides, the development and spread of drug resistance have declined the use of most currently available anthelmintics. Clearly, availability of new anthelmintic agents will be essential in the next few years. More research into the mechanisms of drug actions and their targets are eminent for the discovery and development of novel anthelmintic agents. Recent drug discovery techniques mostly rely on mechanism-based screening of compounds on heterologously expressed targets in bacterial, mammalian or yeast cells. Although this is usually a successful approach, it is money- and time-consuming; meanwhile, pharmaceutical companies prefer the tested target that is chosen based on basic research. The nervous system is the site of action of several chemotherapeutics including pesticides and antinematode drugs; accordingly, the nervous system continues to be a promising target. Recent advances in exploring helminths' nervous system, neurotransmitters and receptors have paved the way for the development of potential agents targeting the nervous system and its components.
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Affiliation(s)
- Amira Taman
- Department of Medical Parasitology, Faculty of Medicine, Mansoura University, Mansoura, 35516, Egypt,
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11
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Orally active antischistosomal early leads identified from the open access malaria box. PLoS Negl Trop Dis 2014; 8:e2610. [PMID: 24416463 PMCID: PMC3886923 DOI: 10.1371/journal.pntd.0002610] [Citation(s) in RCA: 63] [Impact Index Per Article: 6.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/25/2013] [Accepted: 11/14/2013] [Indexed: 01/08/2023] Open
Abstract
Background Worldwide hundreds of millions of schistosomiasis patients rely on treatment with a single drug, praziquantel. Therapeutic limitations and the threat of praziquantel resistance underline the need to discover and develop next generation drugs. Methodology We studied the antischistosomal properties of the Medicines for Malaria Venture (MMV) malaria box containing 200 diverse drug-like and 200 probe-like compounds with confirmed in vitro activity against Plasmodium falciparum. Compounds were tested against schistosomula and adult Schistosoma mansoni in vitro. Based on in vitro performance, available pharmacokinetic profiles and toxicity data, selected compounds were investigated in vivo. Principal Findings Promising antischistosomal activity (IC50: 1.4–9.5 µM) was observed for 34 compounds against schistosomula. Three compounds presented IC50 values between 0.8 and 1.3 µM against adult S. mansoni. Two promising early leads were identified, namely a N,N′-diarylurea and a 2,3-dianilinoquinoxaline. Treatment of S. mansoni infected mice with a single oral 400 mg/kg dose of these drugs resulted in significant worm burden reductions of 52.5% and 40.8%, respectively. Conclusions/Significance The two candidates identified by investigating the MMV malaria box are characterized by good pharmacokinetic profiles, low cytotoxic potential and easy chemistry and therefore offer an excellent starting point for antischistosomal drug discovery and development. To date, praziquantel is the only available drug for the treatment of the tropical neglected disease schistosomiasis and is widely used in morbidity control programs. To discover new chemical scaffolds for the treatment of schistosomiasis, we investigated the Medicines for Malaria Venture malaria box containing 200 diverse drug-like and 200 probe-like compounds with known antimalarial activity against Schistosoma mansoni. Compounds were first investigated on the larval stage of S. mansoni, followed by testing against adult worms in vitro and by in vivo studies of lead candidates. We identified two entirely new chemical scaffolds: the N,N′-diarylurea and 2,3-dianilinoquinoxaline derivatives with antischistosomal in vitro activity in the sub micromolar range and significant activity in the mouse model. Since both compounds offer a good pharmacokinetic profile, low cytotoxic potential and easy chemistry, structure-activity relationship studies should be launched.
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Patocka N, Sharma N, Rashid M, Ribeiro P. Serotonin signaling in Schistosoma mansoni: a serotonin-activated G protein-coupled receptor controls parasite movement. PLoS Pathog 2014; 10:e1003878. [PMID: 24453972 PMCID: PMC3894222 DOI: 10.1371/journal.ppat.1003878] [Citation(s) in RCA: 69] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2013] [Accepted: 11/25/2013] [Indexed: 01/19/2023] Open
Abstract
Serotonin is an important neuroactive substance in all the parasitic helminths. In Schistosoma mansoni, serotonin is strongly myoexcitatory; it potentiates contraction of the body wall muscles and stimulates motor activity. This is considered to be a critical mechanism of motor control in the parasite, but the mode of action of serotonin is poorly understood. Here we provide the first molecular evidence of a functional serotonin receptor (Sm5HTR) in S. mansoni. The schistosome receptor belongs to the G protein-coupled receptor (GPCR) superfamily and is distantly related to serotonergic type 7 (5HT7) receptors from other species. Functional expression studies in transfected HEK 293 cells showed that Sm5HTR is a specific serotonin receptor and it signals through an increase in intracellular cAMP, consistent with a 5HT7 signaling mechanism. Immunolocalization studies with a specific anti-Sm5HTR antibody revealed that the receptor is abundantly distributed in the worm's nervous system, including the cerebral ganglia and main nerve cords of the central nervous system and the peripheral innervation of the body wall muscles and tegument. RNA interference (RNAi) was performed both in schistosomulae and adult worms to test whether the receptor is required for parasite motility. The RNAi-suppressed adults and larvae were markedly hypoactive compared to the corresponding controls and they were also resistant to exogenous serotonin treatment. These results show that Sm5HTR is at least one of the receptors responsible for the motor effects of serotonin in S. mansoni. The fact that Sm5HTR is expressed in nerve tissue further suggests that serotonin stimulates movement via this receptor by modulating neuronal output to the musculature. Together, the evidence identifies Sm5HTR as an important neuronal protein and a key component of the motor control apparatus in S. mansoni.
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Affiliation(s)
- Nicholas Patocka
- Institute of Parasitology, McGill University, Macdonald Campus, Ste. Anne de Bellevue, Quebec, Canada
| | - Nidhi Sharma
- Institute of Parasitology, McGill University, Macdonald Campus, Ste. Anne de Bellevue, Quebec, Canada
| | - Mohammed Rashid
- Institute of Parasitology, McGill University, Macdonald Campus, Ste. Anne de Bellevue, Quebec, Canada
| | - Paula Ribeiro
- Institute of Parasitology, McGill University, Macdonald Campus, Ste. Anne de Bellevue, Quebec, Canada
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Ribeiro P, Patocka N. Neurotransmitter transporters in schistosomes: Structure, function and prospects for drug discovery. Parasitol Int 2013; 62:629-38. [DOI: 10.1016/j.parint.2013.06.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/05/2013] [Revised: 06/12/2013] [Accepted: 06/14/2013] [Indexed: 12/23/2022]
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Knopp S, Becker SL, Ingram KJ, Keiser J, Utzinger J. Diagnosis and treatment of schistosomiasis in children in the era of intensified control. Expert Rev Anti Infect Ther 2013; 11:1237-58. [PMID: 24127662 DOI: 10.1586/14787210.2013.844066] [Citation(s) in RCA: 66] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
In the current era of intensified and integrated control against schistosomiasis and other neglected tropical diseases, there is a need to carefully rethink and take into consideration disease-specific issues pertaining to the diagnosis, prevention, control and local elimination. Here, we present a comprehensive overview about schistosomiasis including recent trends in the number of people treated with praziquantel and the latest developments in diagnosis and control. Particular emphasis is placed on children. Identified research needs are offered for consideration; namely, expanding our knowledge about schistosomiasis in preschool-aged children, assessing and quantifying the impact of schistosomiasis on infectious and noncommunicable diseases, developing new antischistosomal drugs and child-friendly formulations, designing and implementing setting-specific control packages and developing highly sensitive, but simple diagnostic tools that are able to detect very light infections in young children and in people living in areas targeted for schistosomiasis elimination.
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Affiliation(s)
- Stefanie Knopp
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, P.O. Box, CH-4002, Basel, Switzerland
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Abou-Zeid AH, Abkar TA, Mohamed RO. Schistosomiasis infection among primary school students in a war zone, Southern Kordofan State, Sudan: a cross-sectional study. BMC Public Health 2013; 13:643. [PMID: 23845226 PMCID: PMC3729662 DOI: 10.1186/1471-2458-13-643] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/27/2012] [Accepted: 07/10/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND Schistosomiasis is a major health problem adversely affecting the health of vulnerable populations in Sudan. METHODS We conducted a school-based survey to estimate the prevalence of schistosomiasis in 36 villages in Southern Kordofan (SK) State. A total of 2,302 primary school students were recruited. Each student completed a questionnaire and submitted one urine and one stool sample. RESULTS The prevalence of schistosomiasis haematobium was 23.7%, while schistosomiasis mansoni was not detected among the study participants. S. haematobium infection was identified in all areas, with the highest prevalence in the western locality of SK State. The infection was associated with the distance between home/school and open water sources. In addition, S. haematobium infection was associated with the existence of and distance to open water sources, higher frequency of contact with open water, absence of a health advocacy group in the school and history of schistosomiasis treatment. CONCLUSIONS This study highlights schistosomiasis as a public health problem in SK State. The findings will guide the schistosomiasis Control Program of the State Ministry of Health in developing and applying treatment plans for schistosomiasis in SK State.
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Affiliation(s)
- Alaa H Abou-Zeid
- Public Health Department, Faculty of Medicine, Cairo University, Kasr Al Ainy St., Cairo, Egypt.
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Caffrey CR, Steverding D. Recent initiatives and strategies to developing new drugs for tropical parasitic diseases. Expert Opin Drug Discov 2013; 3:173-86. [PMID: 23480221 DOI: 10.1517/17460441.3.2.173] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/17/2022]
Abstract
BACKGROUND Despite the toll of tropical parasitic diseases on human life in the developing world, present therapies still rely on drugs developed decades ago. In many cases, the clinical usefulness of these compounds is limited due to poor efficacy, toxicity and the constant attrition of drug resistance. The absence of a profit incentive regarding diseases afflicting the very poor has resulted in a lack of investment by the pharmaceutical industry in new chemotherapies. OBJECTIVE Given this background, this review addresses what alternative economic and scientific strategies have been implemented to procure novel drugs. METHODS The latest chemical, genetic and screening technologies to discover and develop drugs for tropical parasitic diseases are reviewed. In many cases these strategies are being implemented within the framework of public-private partnerships established to sustain dynamic drug development portfolios. Examples of public-private partnerships and their portfolios are discussed. Further, the contribution of dedicated academic screening centres to target discovery and preclinical prosecution of new small molecules is also highlighted. In every case, the latest scientific literature is cited, but also relevant press releases and website information to indicate the present vitality in the field. CONCLUSION The tools, institutions and consortia are now in place and evolving to deliver new pharmaceuticals. Short-term results have already been realised in the clinic, mainly through the provision of new formulations of existing drugs. Long-term and consistent investment will be required, however, to identify, develop and clinically validate new chemical entities.
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Affiliation(s)
- Conor R Caffrey
- University of California San Francisco, Sandler Center for Basic Research in Parasitic Diseases, California Institute for Quantitative Biosciences, Byers Hall 501E, 1700 4th Street, San Francisco, CA 94158, USA
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In vitro antischistosomal evaluation of some newly synthesized praziquantel derivatives. RESEARCH ON CHEMICAL INTERMEDIATES 2012. [DOI: 10.1007/s11164-012-0854-9] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/27/2022]
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Abou-Zeid AHA, Abkar TA, Mohamed RO. Schistosomiasis and soil-transmitted helminths among an adult population in a war affected area, Southern Kordofan state, Sudan. Parasit Vectors 2012; 5:133. [PMID: 22759923 PMCID: PMC3481353 DOI: 10.1186/1756-3305-5-133] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/22/2012] [Accepted: 07/03/2012] [Indexed: 12/03/2022] Open
Abstract
Background Schistosomiasis remains a major health problem at global and national levels, contributing to the vulnerability of the poor people in Sudan. Southern Kordofan is affected by Schistosomiasis but the disease prevalence was unknown. Methods 1826 adults were recruited in a community-based survey. Each recruited subject submitted at least 10 ml urine and one stool sample; they were also interviewed and filled in a questionnaire. Results 1826 adults were recruited in a community-based survey. Each recruited subject submitted at least 10 ml urine and one stool sample; they were also interviewed and filled in a questionnaire. The prevalence of S. haematobium was 6.9 % among the adult population. We estimated S. mansoni prevalence as 0.0 %. S. haematobium infection was focally distributed at the village level. The infection was associated with non preference of latrine use – if available, use of open water source for household affairs such as cleaning and also with the history of schistosomiasis treatment. The prevalence of soil transmitted helminths (STH) was also reported as high at 7.8 %, and two species were identified; Hymenolepis nana and Giardia lamblia. Conclusion Schistosomiasis is a significant health problem among the adult population in Southern Kordofan. The estimated prevalence will serve as a guide in developing a Schistosomiasis Control Program and applying treatment plans.
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Affiliation(s)
- Alaa Hammad Ali Abou-Zeid
- Public Health Department, Faculty of Medicine, Cairo University, Kasr Al Ainy St, Manial, Cairo, Egypt.
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Keiser J, Vargas M, Winter R. Anthelminthic properties of mangostin and mangostin diacetate. Parasitol Int 2012; 61:369-71. [DOI: 10.1016/j.parint.2012.01.004] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/26/2011] [Revised: 01/04/2012] [Accepted: 01/05/2012] [Indexed: 11/30/2022]
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Fürst T, Duthaler U, Sripa B, Utzinger J, Keiser J. Trematode Infections. Infect Dis Clin North Am 2012; 26:399-419. [DOI: 10.1016/j.idc.2012.03.008] [Citation(s) in RCA: 47] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/06/2023]
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Biogenic amines and the control of neuromuscular signaling in schistosomes. INVERTEBRATE NEUROSCIENCE 2012; 12:13-28. [PMID: 22526557 DOI: 10.1007/s10158-012-0132-y] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [Subscribe] [Scholar Register] [Received: 03/19/2012] [Accepted: 03/29/2012] [Indexed: 12/14/2022]
Abstract
Biogenic amines are small cationic monoamines that function broadly as neurotransmitters and/or neuromodulators in every animal phylum. They include such ubiquitous substances as serotonin, dopamine and invertebrate-specific phenolamines (tyramine, octopamine), among others. Biogenic amines are important neuroactive agents in all the flatworms, including blood flukes of the genus Schistosoma, the etiological agents of human schistosomiasis. A large body of evidence spanning nearly five decades identifies biogenic amines as major modulators of neuromuscular function in schistosomes, controlling movement, attachment to the host and other fundamental behaviors. Recent advances in schistosome genomics have made it possible to dissect the molecular mechanisms responsible for these effects and to identify the proteins involved. These efforts have already provided important new information about the mode of action of amine transmitters in the parasite. Moreover, these advances are continuing, as the field moves into a post-genomics era, and new molecular tools for gene and protein analysis are becoming available. Here, we review the current status of this research and discuss future prospects. In particular, we focus our attention on the receptors that mediate biogenic amine activity, their structural characteristics, functional properties and "druggability" potential. One of the themes that will emerge from this discussion is that schistosomes have a rich diversity of aminergic receptors, many of which share little sequence homology with those of the human host, making them ideally suited for selective drug targeting. Strategies for the characterization of these important parasite proteins will be discussed.
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Keiser J, Ingram K, Vargas M, Chollet J, Wang X, Dong Y, Vennerstrom JL. In vivo activity of aryl ozonides against Schistosoma species. Antimicrob Agents Chemother 2012; 56:1090-2. [PMID: 22106214 PMCID: PMC3264258 DOI: 10.1128/aac.05371-11] [Citation(s) in RCA: 58] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2011] [Accepted: 11/10/2011] [Indexed: 11/20/2022] Open
Abstract
We evaluated the in vivo antischistosomal activities of 11 structurally diverse synthetic peroxides. Of all compounds tested, ozonide (1,2,4-trioxolane) OZ418 had the highest activity against adult Schistosoma mansoni, with total and female worm burden reductions of 80 and 90% (P < 0.05), respectively. Furthermore, treatment of S. haematobium-infected mice with OZ418 reduced the total worm burden by 86%. In conclusion, OZ418 is a promising antischistosomal lead compound.
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Affiliation(s)
- Jennifer Keiser
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland.
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Lee H, Moody-Davis A, Saha U, Suzuki BM, Asarnow D, Chen S, Arkin M, Caffrey CR, Singh R. Quantification and clustering of phenotypic screening data using time-series analysis for chemotherapy of schistosomiasis. BMC Genomics 2012; 13 Suppl 1:S4. [PMID: 22369037 PMCID: PMC3471343 DOI: 10.1186/1471-2164-13-s1-s4] [Citation(s) in RCA: 36] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/23/2022] Open
Abstract
Background Neglected tropical diseases, especially those caused by helminths, constitute some of the most common infections of the world's poorest people. Development of techniques for automated, high-throughput drug screening against these diseases, especially in whole-organism settings, constitutes one of the great challenges of modern drug discovery. Method We present a method for enabling high-throughput phenotypic drug screening against diseases caused by helminths with a focus on schistosomiasis. The proposed method allows for a quantitative analysis of the systemic impact of a drug molecule on the pathogen as exhibited by the complex continuum of its phenotypic responses. This method consists of two key parts: first, biological image analysis is employed to automatically monitor and quantify shape-, appearance-, and motion-based phenotypes of the parasites. Next, we represent these phenotypes as time-series and show how to compare, cluster, and quantitatively reason about them using techniques of time-series analysis. Results We present results on a number of algorithmic issues pertinent to the time-series representation of phenotypes. These include results on appropriate representation of phenotypic time-series, analysis of different time-series similarity measures for comparing phenotypic responses over time, and techniques for clustering such responses by similarity. Finally, we show how these algorithmic techniques can be used for quantifying the complex continuum of phenotypic responses of parasites. An important corollary is the ability of our method to recognize and rigorously group parasites based on the variability of their phenotypic response to different drugs. Conclusions The methods and results presented in this paper enable automatic and quantitative scoring of high-throughput phenotypic screens focused on helmintic diseases. Furthermore, these methods allow us to analyze and stratify parasites based on their phenotypic response to drugs. Together, these advancements represent a significant breakthrough for the process of drug discovery against schistosomiasis in particular and can be extended to other helmintic diseases which together afflict a large part of humankind.
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Affiliation(s)
- Hyokyeong Lee
- Department of Computer Science, San Francisco State University, San Francisco, CA 94132, USA
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Xiao SH, Xue J, Mei JY, Jiao PY. Effectiveness of synthetic trioxolane OZ78 against Schistosoma japonicum in mice and rabbits. Parasitol Res 2011; 110:2307-14. [PMID: 22200956 DOI: 10.1007/s00436-011-2765-x] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2011] [Accepted: 12/05/2011] [Indexed: 12/23/2022]
Abstract
Antischistosomal activities of a synthetic peroxide OZ78 (an ozonide carboxylic acid) against Schistosoma japonicum have been studied in mice and rabbits. Among 132 mice used, 30 of them were infected with 80-100 S. japonicum cercariae for collection of juvenile and adult schistosomes applied in in vitro tests. The remaining 102 mice were infected with 40 schistosome cercariae used for experimental treatment. Other 13 rabbits infected each with 200 schistosome cercariae were treated orally with OZ78 42 days post-infection. Most treated mice and rabbits were sacrificed 4 weeks post-treatment to collect residual schistosomes for evaluation of the drug efficacy. OZ78 and its sodium salt (OZ78-Na salt) 10-60 μg/mL alone exhibited no in vitro effect against day 14, day 21 schistosomula, and day 35 adult schistosomes. But OZ78 and OZ78-Na salt 10 and 20 μg/mL together with hemin 80 μg/mL showed decrease in worm motor activity and severe damage to the worm tegument and intestine, and all worms died within 3 days post-incubation. After infected mice were treated orally with OZ78 at a single dose of 400 mg/kg for 1 day, 34.9% of the worms shifted to the liver. Three and 7 days post-treatment, 100% of the worms were recovered from the liver. Fourteen days post-treatment, 92.3% of the worms still remained in the liver and 7.7% of the worms returned back to the mesenteric veins. Male and female worms shifted to the liver revealed in apparent shrinkage, degeneration of worm body, depigmentation in gut, and disappearance of ova in the uterus of some female worms. Meanwhile, dead worm and dead worm fragments were found in the liver tissues. In mice infected with various stages of schistosomes and treated orally with single OZ78 400 mg/kg, moderate or potential effect of the drug against day 0 (3-h-old worm), day 7, day 14, and day 21 juvenile worms and day 28, day 35 as well as day 42 adult worms were observed, the differences of total or female worm burdens between each treated group and control group were statistically significant (P < 0.01 or P < 0.05). Among the various stages of juveniles, day 7 worms were more susceptible to OZ78 with worm reduction of 83.8%, while the effect of OZ78 against day 28 to day 42 adult worms were similar. Finally, rabbits infected with adult schistosomes and treated with OZ78 at a single dose of 45 mg/kg or a daily dose of 35 mg/kg for three consecutive days resulted in significantly lower total and female worm burdens in comparison with that of control (P < 0.05) with total and female worm reductions of 84.1% and 84.7% as well as 74.3% and 77.4%, respectively. The results demonstrate that OZ78 possesses effect against both juvenile and adult S. japonicum in mouse model, and also shows effect against adult schistosomes in rabbits.
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Affiliation(s)
- Shu-Hua Xiao
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Key Laboratory of Parasite and Vector Biology, MOH, WHO Collaborating Centre for Malaria, Schistosomiasis, and Filariasis, Shanghai, 200025, People's Republic of China.
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Wang X, Zhao Q, Vargas M, Dong Y, Sriraghavan K, Keiser J, Vennerstrom JL. The activity of dispiro peroxides against Fasciola hepatica. Bioorg Med Chem Lett 2011; 21:5320-3. [PMID: 21802291 PMCID: PMC3159854 DOI: 10.1016/j.bmcl.2011.07.024] [Citation(s) in RCA: 28] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2011] [Revised: 07/01/2011] [Accepted: 07/06/2011] [Indexed: 11/21/2022]
Abstract
Dispiro 1,2,4-trioxanes and 1,2,4,5-tetraoxanes had superior efficacy against Fasciola hepatica than the corresponding ozonides (1,2,4-trioxolanes). For highest efficacy, spiroadamantane and carboxymethyl substructures were required. Three compounds completely cured F. hepatica-infected mice at single oral doses of 50mg/kg and two were partially curative at single doses of 25mg/kg.
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Affiliation(s)
- Xiaofang Wang
- College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, USA
| | - Qingjie Zhao
- College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, USA
| | - Mireille Vargas
- Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4002 Basel, Switzerland
- University of Basel, CH-4003 Basel, Switzerland
| | - Yuxiang Dong
- College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, USA
| | - Kamaraj Sriraghavan
- College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, USA
| | - Jennifer Keiser
- Swiss Tropical and Public Health Institute, Socinstrasse 57, CH-4002 Basel, Switzerland
- University of Basel, CH-4003 Basel, Switzerland
| | - Jonathan L. Vennerstrom
- College of Pharmacy, University of Nebraska Medical Center, 986025 Nebraska Medical Center, Omaha, NE, USA
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Utzinger J, N’Goran EK, Caffrey CR, Keiser J. From innovation to application: social-ecological context, diagnostics, drugs and integrated control of schistosomiasis. Acta Trop 2011; 120 Suppl 1:S121-37. [PMID: 20831855 DOI: 10.1016/j.actatropica.2010.08.020] [Citation(s) in RCA: 150] [Impact Index Per Article: 11.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/02/2010] [Revised: 08/29/2010] [Accepted: 08/30/2010] [Indexed: 12/11/2022]
Abstract
Compared to malaria, tuberculosis and HIV/AIDS, schistosomiasis remains a truly neglected tropical disease. Schistosomiasis, perhaps more than any other disease, is entrenched in prevailing social-ecological systems, since transmission is governed by human behaviour (e.g. open defecation and patterns of unprotected surface water contacts) and ecological features (e.g. living in close proximity to suitable freshwater bodies in which intermediate host snails proliferate). Moreover, schistosomiasis is intimately linked with poverty and the disease has spread to previously non-endemic areas as a result of demographic, ecological and engineering transformations. Importantly though, thanks to increased advocacy there is growing awareness, financial and technical support to control and eventually eliminate schistosomiasis as a public health problem at local, regional and global scales. The purpose of this review is to highlight recent progress made in innovation, validation and application of new tools and strategies for research and integrated control of schistosomiasis. First, we explain that schistosomiasis is deeply embedded in social-ecological systems and explore linkages with poverty. We then summarize and challenge global statistics, risk maps and burden estimates of human schistosomiasis. Discovery and development research pertaining to novel diagnostics and drugs forms the centrepiece of our review. We discuss unresolved issues and emerging opportunities for integrated and sustainable control of schistosomiasis and conclude with a series of research needs.
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Keiser J, Manneck T, Vargas M. Interactions of mefloquine with praziquantel in the Schistosoma mansoni mouse model and in vitro. J Antimicrob Chemother 2011; 66:1791-7. [PMID: 21602552 DOI: 10.1093/jac/dkr178] [Citation(s) in RCA: 55] [Impact Index Per Article: 4.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
OBJECTIVES Mefloquine has interesting antischistosomal properties, hence it might be an attractive partner drug for combination treatment with praziquantel. The aim of this study was to evaluate activities of mefloquine/praziquantel combinations against Schistosoma mansoni in vitro and in vivo. METHODS Dose-response relationships were established following exposure of adult S. mansoni to mefloquine, praziquantel and fixed dose combinations of mefloquine/praziquantel in vitro. S. mansoni-infected mice were treated orally with selected doses of single drugs and drug combinations 7 weeks post-infection. RESULTS We calculated in vitro LC(50) values of 0.024 and 1.9 μg/mL for praziquantel and mefloquine, respectively. Mefloquine/praziquantel combinations showed synergistic effects, with combination index (CI) values <1 when adult S. mansoni were simultaneously incubated with both drugs in vitro. Reduced viabilities were also observed when schistosomes were first exposed to mefloquine followed by praziquantel in vitro. ED(50)s of 62 mg/kg and 172 mg/kg were determined for mefloquine and praziquantel against adult S. mansoni in vivo, respectively. Combinations of praziquantel (50 or 100 mg/kg) followed the next day by mefloquine (50 or 100 mg/kg) treatment revealed only moderate total worm burden reductions of 47.8%-54.7%. On the other hand, when both drugs (100 mg/kg each) were either given simultaneously or mefloquine was given prior to praziquantel, high total and female worm burden reductions of 86.0%-93.1% were observed. For the later treatment regimen, synergistic effects (CI < 1) were calculated when mefloquine and praziquantel were combined using a fixed dose ratio based on their ED(50)s. CONCLUSIONS Combinations of mefloquine and praziquantel may have clinical utility in the treatment of schistosomiasis.
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Affiliation(s)
- Jennifer Keiser
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, CH-4002 Basel, Switzerland.
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Antiparasitic drugs for paediatrics: systematic review, formulations, pharmacokinetics, safety, efficacy and implications for control. Parasitology 2011; 138:1620-32. [PMID: 21349223 DOI: 10.1017/s0031182011000023] [Citation(s) in RCA: 36] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Drug development for paediatric applications entails a number of challenges, such as the wide age spectrum covered - from birth to adolescence - and developmental changes in physiology during biological maturation that influence the efficacy and toxicity of drugs. Safe and efficacious antiparasitic drugs for children are of pivotal importance given the large proportion of burden attributable to parasitic diseases in this age group, and growing efforts to administer, as widely as possible, antiparasitic drugs to at-risk populations, such as infants and school-aged children, often without prior diagnosis. The purpose of this review is to investigate whether antiparasitic drugs have been adequately studied for use in paediatrics. We approached this issue through a systematic review using PubMed and the Cochrane Central Register of Trials covering a period of 10 years and 8 months until the end of August 2010 to identify trials that investigated efficacy, safety and pharmacokinetic (PK) parameters of antiparasitic drugs for paediatrics. Overall, 269 clinical drug trials and 17 PK studies met our inclusion criteria. Antimalarial drugs were the most commonly studied medicines (82·6%). Most trials were carried out in Africa and children aged 2-11 years were the age group most often investigated. Additionally, we critically examined available drug formulations for anthelminthics and identified a number of shortcomings that are discussed. Finally, we shed new light on current proposals to expand 'preventive chemotherapy' to preschool-aged children and emphasise that new research, including risk-benefit analyses, are needed before such a strategy can be adopted more widely.
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RNA interference in Schistosoma mansoni schistosomula: selectivity, sensitivity and operation for larger-scale screening. PLoS Negl Trop Dis 2010; 4:e850. [PMID: 20976050 PMCID: PMC2957409 DOI: 10.1371/journal.pntd.0000850] [Citation(s) in RCA: 96] [Impact Index Per Article: 6.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2010] [Accepted: 09/16/2010] [Indexed: 12/30/2022] Open
Abstract
BACKGROUND The possible emergence of resistance to the only available drug for schistosomiasis spurs drug discovery that has been recently incentivized by the availability of improved transcriptome and genome sequence information. Transient RNAi has emerged as a straightforward and important technique to interrogate that information through decreased or loss of gene function and identify potential drug targets. To date, RNAi studies in schistosome stages infecting humans have focused on single (or up to 3) genes of interest. Therefore, in the context of standardizing larger RNAi screens, data are limited on the extent of possible off-targeting effects, gene-to-gene variability in RNAi efficiency and the operational capabilities and limits of RNAi. METHODOLOGY/PRINCIPAL FINDINGS We investigated in vitro the sensitivity and selectivity of RNAi using double-stranded (ds)RNA (approximately 500 bp) designed to target 11 Schistosoma mansoni genes that are expressed in different tissues; the gut, tegument and otherwise. Among the genes investigated were 5 that had been previously predicted to be essential for parasite survival. We employed mechanically transformed schistosomula that are relevant to parasitism in humans, amenable to screen automation and easier to obtain in greater numbers than adult parasites. The operational parameters investigated included defined culture media for optimal parasite maintenance, transfection strategy, time- and dose-dependency of RNAi, and dosing limits. Of 7 defined culture media tested, Basch Medium 169 was optimal for parasite maintenance. RNAi was best achieved by co-incubating parasites and dsRNA (standardized to 30 µg/ml for 6 days); electroporation provided no added benefit. RNAi, including interference of more than one transcript, was selective to the gene target(s) within the pools of transcripts representative of each tissue. Concentrations of dsRNA above 90 µg/ml were directly toxic. RNAi efficiency was transcript-dependent (from 40 to >75% knockdown relative to controls) and this may have contributed to the lack of obvious phenotypes observed, even after prolonged incubations of 3 weeks. Within minutes of their mechanical preparation from cercariae, schistosomula accumulated fluorescent macromolecules in the gut indicating that the gut is an important route through which RNAi is expedited in the developing parasite. CONCLUSIONS Transient RNAi operates gene-selectively in S. mansoni newly transformed schistosomula yet the sensitivity of individual gene targets varies. These findings and the operational parameters defined will facilitate larger RNAi screens.
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Utzinger J, Bergquist R, Olveda R, Zhou XN. Important helminth infections in Southeast Asia diversity, potential for control and prospects for elimination. ADVANCES IN PARASITOLOGY 2010; 72:1-30. [PMID: 20624526 DOI: 10.1016/s0065-308x(10)72001-7] [Citation(s) in RCA: 67] [Impact Index Per Article: 4.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/28/2022]
Abstract
Besides the 'big three'-HIV/AIDS, malaria and tuberculosis-there are a host of diseases that, by comparison, are truly neglected. These so-called neglected tropical diseases (NTDs), many of which caused by helminths, are intimately linked with poverty and are rampant where housing is poor; access to clean water and adequate sanitation is lacking; hygiene and nutrition is substandard and populations are marginalized and vulnerable. More than a billion people are affected by NTDs, mainly in remote rural and deprived urban settings of the developing world. An overview of papers published in two special thematic volumes of the Advances in Parasitology is provided here under the umbrella of current status of research and control of important helminth infections. A total of 25 comprehensive reviews are presented, which summarise the latest available data pertaining to the diagnosis, epidemiology, pathogenesis, prevention, treatment, control and eventual elimination of NTDs in Southeast Asia and neighbourhood countries. The focus of the first volume provides the current regional status of schistosomiasis, lymphatic filariasis, food-borne trematodiases, echinococcosis and cysticercosis/taeniasis, less common parasitic diseases that can cause epidemic outbreaks and helminth infections affecting the central nervous system. The second volume deals with the tools and strategies for control, including diagnostics, drugs, vaccines and cutting-edge basic research (e.g. the '-omics' sciences). Moreover, cross-cutting themes such as multiparasitism, social sciences, capacity strengthening, geospatial health technologies, health metrics and modelling the potential impact of climate change on helminthic diseases are discussed. Hopefully, these two volumes will become useful for researchers and, most importantly, disease control managers for integrated and sustainable control, rigorous monitoring and eventual elimination of NTDs in Southeast Asia and elsewhere.
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Affiliation(s)
- Jürg Utzinger
- Department of Epidemiology and Public Health, Swiss Tropical and Public Health Institute, Basel, Switzerland
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Keiser J, Utzinger J. The drugs we have and the drugs we need against major helminth infections. ADVANCES IN PARASITOLOGY 2010; 73:197-230. [PMID: 20627144 DOI: 10.1016/s0065-308x(10)73008-6] [Citation(s) in RCA: 200] [Impact Index Per Article: 14.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/19/2022]
Abstract
Parasitic worms (helminths) have accompanied humans for thousands of years and, still today, they are pervasive where poverty persists, including large parts of Southeast Asia and the Western Pacific Region. The global strategy for the control of helminth infections is morbidity control and elimination as a public health problem. Regular administration of anthelminthic drugs to at-risk populations (e.g. school-aged children) serves as the backbone of interventions in areas where helminth infections are highly endemic. In this review, we focus on soil-transmitted helminthiasis (ascariasis, hookworm disease, strongyloidiasis and trichuriasis) and food-borne trematodiasis (clonorchiasis, fascioliasis, intestinal fluke infections, opisthorchiasis and paragonimiasis) and discuss the few drugs that are currently available for their treatment and control. Emphasis is placed on efficacy with new light shed on multiple dosing and combination therapy. We summarise recent advances made with anthelminthic drugs that might become the future armentarium for the control of major helminthiasis (e.g. artemisinins, cyclooctadepsipeptides, mefloquine, monepantel, nitazoxandide, synthetic peroxides and tribendimidine). Issuing from our review are current research gaps and the need for concerted efforts to discover, develop and deploy the next generation of anthelminthic drugs.
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Affiliation(s)
- Jennifer Keiser
- Department of Medical Parasitology and Infection Biology, Swiss Tropical and Public Health Institute, Basel, Switzerland
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Effectiveness of mefloquine against Clonorchis sinensis in rats and Paragonimus westermani in dogs. Parasitol Res 2010; 107:1391-7. [PMID: 20680332 DOI: 10.1007/s00436-010-2007-7] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/12/2010] [Accepted: 07/22/2010] [Indexed: 12/21/2022]
Abstract
The aim of the study is to explore the effect of mefloquine against Clonorchis sinensis and Paragonimus westermani. For anti-C. sinensis study, a total of 71 rats were divided into four batches for oral infection of each rat with 50 C. sinensis metacercariae. Five to 7 weeks post-infection, groups of rats were treated orally with mefloquine at single doses or multiple daily doses while infected, but untreated rats served as control. All treated rats were euthanized 2 weeks post-treatment for assessment of efficacy. For anti-P. westermani study, two batches of eight and ten dogs were each infected intraperitoneally with 100 P. westermani metacercariae. Eighty-five to 96 days post-infection, groups of two or three dogs were treated orally with mefloquine and groups of two dogs were treated with praziquantel at a single dose or multiple doses. In each batch of test, three untreated but infected dogs served as control. All treated dogs were euthanized 26-30 days post-treatment for evaluation of efficacy. In rats infected with C. sinensis and treated orally with mefloquine at a single dose of 75 and 150 mg/kg, no effect against C. sinensis was observed. When the dose of mefloquine was increased to 250 mg/kg, one third (five out of 15) rats died 3-5 days post-treatment. Although the mean worm burden was lower than that of the control, the difference between the treated and control groups was not statistically significant (P>0.05) with worm burden reduction of 22.4%. Whereas, the group of infected rats received mefloquine at a daily dose of 100 mg/kg for 3 days, one out of five rats died after the last administration. The mean worm burden was significantly lower than that of the control with worm burden reduction of 67.6% (P<0.01). In the first test of mefloquine against P. westermani, three infected dogs received two oral doses of the drug, 50 mg/kg, given at a 4-h interval, the mean worm burden were similar to that of the control. While other two dogs were treated with praziquantel at the same dose schedule, the worm burden reduction of 78% was observed. In the second test, three and two dogs were treated with mefloquine 50 mg/kg daily for 5 days or 100 mg/kg daily for 2 days; the mean worm burdens of the two groups were lower than that of the control with worm burden reduction of 65.6% and 51.9%, respectively. However, only the difference of mean worm burdens between mefloquine 50 mg/kg given daily for 5 days and the control was statistically significant (P<0.05). Other two dogs treated with praziquantel at a single dose of 100 mg/kg were cured. The results indicate that under the appropriate dose schedule mefloquine exhibits less effect against C. sinensis in rats and P. westermani in dogs.
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Zhao Q, Vargas M, Dong Y, Zhou L, Wang X, Sriraghavan K, Keiser J, Vennerstrom JL. Structure-activity relationship of an ozonide carboxylic acid (OZ78) against Fasciola hepatica. J Med Chem 2010; 53:4223-33. [PMID: 20423101 DOI: 10.1021/jm100226t] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022]
Abstract
In this paper, we describe the SAR of ozonide carboxylic acid OZ78 (1) as the first part of our search for a trematocidal synthetic peroxide drug development candidate. We found that relatively small structural changes to 1 resulted most commonly in loss of activity against Fasciola hepatica in vivo. A spiroadamantane substructure and acidic functional group (or ester prodrug) were required for activity. Of 26 new compounds administered at single 100 mg/kg oral doses to F. hepatica infected rats, 8 had statistically significant worm burden reductions, 7 were partially curative, and 1 (acylsulfonamide 6) was completely curative and comparable to 1 in flukicidal efficacy. This study also showed that the activity of 1 is peroxide-bond-dependent, suggesting that its flukicidal efficacy depends upon hemoglobin digestion in F. hepatica.
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Affiliation(s)
- Qingjie Zhao
- College of Pharmacy, University of Nebraska Medical Center, Omaha, Nebraska, USA
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Schistosomiasis and neglected tropical diseases: towards integrated and sustainable control and a word of caution. Parasitology 2010; 136:1859-74. [PMID: 19906318 DOI: 10.1017/s0031182009991600] [Citation(s) in RCA: 281] [Impact Index Per Article: 20.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
In May 2001, the World Health Assembly (WHA) passed a resolution which urged member states to attain, by 2010, a minimum target of regularly administering anthelminthic drugs to at least 75% and up to 100% of all school-aged children at risk of morbidity. The refined global strategy for the prevention and control of schistosomiasis and soil-transmitted helminthiasis was issued in the following year and large-scale administration of anthelminthic drugs endorsed as the central feature. This strategy has subsequently been termed 'preventive chemotherapy'. Clearly, the 2001 WHA resolution led the way for concurrently controlling multiple neglected tropical diseases. In this paper, we recall the schistosomiasis situation in Africa in mid-2003. Adhering to strategic guidelines issued by the World Health Organization, we estimate the projected annual treatment needs with praziquantel among the school-aged population and critically discuss these estimates. The important role of geospatial tools for disease risk mapping, surveillance and predictions for resource allocation is emphasised. We clarify that schistosomiasis is only one of many neglected tropical diseases and that considerable uncertainties remain regarding global burden estimates. We examine new control initiatives targeting schistosomiasis and other tropical diseases that are often neglected. The prospect and challenges of integrated control are discussed and the need for combining biomedical, educational and engineering strategies and geospatial tools for sustainable disease control are highlighted. We conclude that, for achieving integrated and sustainable control of neglected tropical diseases, a set of interventions must be tailored to a given endemic setting and fine-tuned over time in response to the changing nature and impact of control. Consequently, besides the environment, the prevailing demographic, health and social systems contexts need to be considered.
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Keiser J, Veneziano V, Rinaldi L, Mezzino L, Duthaler U, Cringoli G. Anthelmintic activity of artesunate against Fasciola hepatica in naturally infected sheep. Res Vet Sci 2010; 88:107-10. [DOI: 10.1016/j.rvsc.2009.05.007] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/14/2008] [Revised: 03/17/2009] [Accepted: 05/11/2009] [Indexed: 10/20/2022]
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Botros SS, William S, Beadle JR, Valiaeva N, Hostetler KY. Antischistosomal activity of hexadecyloxypropyl cyclic 9-(S)-[3-hydroxy-2-(phosphonomethoxy)propyl]adenine and other alkoxyalkyl esters of acyclic nucleoside phosphonates assessed by schistosome worm killing in vitro. Antimicrob Agents Chemother 2009; 53:5284-7. [PMID: 19704122 PMCID: PMC2786359 DOI: 10.1128/aac.00840-09] [Citation(s) in RCA: 14] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/22/2009] [Revised: 07/17/2009] [Accepted: 08/18/2009] [Indexed: 11/20/2022] Open
Abstract
9-(S)-[3-Hydroxy-2-(phosphonomethoxy)propyl]adenine [(S)-HPMPA] has been reported to have antischistosomal activity. Ether lipid esters of (S)-HPMPA and cidofovir (CDV) have greatly increased activities in antiviral assays and in lethal animal models of poxvirus diseases. To see if ether lipid esters of CDV and (S)-HPMPA enhance antischistosomal activity, we tested their alkoxyalkyl esters using Schistosoma mansoni worm killing in vitro. Hexadecyloxypropyl (HDP)-cyclic-(S)-HPMPA and HDP-cyclic-CDV exhibited significant in vitro antischistosomal activities and may offer promise alone or in combination with praziquantel.
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Affiliation(s)
- Sanaa S. Botros
- Departments of Pharmacology, Parasitology, Theodor Bilharz Research Institute, Warrak el-Hadar, Imbaba, P.O. Box 30, Giza 12411, Egypt, San Diego Veterans Medical Research Foundation and Department of Medicine, Division of Infectious Disease, University of California, San Diego, La Jolla, California 92093
| | - Samia William
- Departments of Pharmacology, Parasitology, Theodor Bilharz Research Institute, Warrak el-Hadar, Imbaba, P.O. Box 30, Giza 12411, Egypt, San Diego Veterans Medical Research Foundation and Department of Medicine, Division of Infectious Disease, University of California, San Diego, La Jolla, California 92093
| | - James R. Beadle
- Departments of Pharmacology, Parasitology, Theodor Bilharz Research Institute, Warrak el-Hadar, Imbaba, P.O. Box 30, Giza 12411, Egypt, San Diego Veterans Medical Research Foundation and Department of Medicine, Division of Infectious Disease, University of California, San Diego, La Jolla, California 92093
| | - Nadejda Valiaeva
- Departments of Pharmacology, Parasitology, Theodor Bilharz Research Institute, Warrak el-Hadar, Imbaba, P.O. Box 30, Giza 12411, Egypt, San Diego Veterans Medical Research Foundation and Department of Medicine, Division of Infectious Disease, University of California, San Diego, La Jolla, California 92093
| | - Karl Y. Hostetler
- Departments of Pharmacology, Parasitology, Theodor Bilharz Research Institute, Warrak el-Hadar, Imbaba, P.O. Box 30, Giza 12411, Egypt, San Diego Veterans Medical Research Foundation and Department of Medicine, Division of Infectious Disease, University of California, San Diego, La Jolla, California 92093
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Morphological effects and tegumental alterations induced by mefloquine on schistosomula and adult flukes of Schistosoma mansoni. Parasitology 2009; 137:85-98. [PMID: 19814844 DOI: 10.1017/s0031182009990965] [Citation(s) in RCA: 134] [Impact Index Per Article: 8.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
Abstract
There is a pressing need to develop novel anti-schistosomal drugs, as current treatment relies largely on praziquantel (PZQ). To further strengthen current evidence of the anti-schistosomal properties of mefloquine (MQ), we studied the temporal effect of this compound in vitro and in vivo, and examined alterations on the tegumental surface of schistosomula and adults of S. mansoni by means of scanning electron microscopy (SEM). Schistosomula and adults were each incubated in vitro using MQ over a wide concentration range (1-100 microg/ml). In addition, mice infected with adult S. mansoni were treated with a single oral dose of 400 mg/kg MQ, and worms were recovered 24, 48, 72, 96 and 120 h following treatment. MQ showed a rapid onset of action on schistosomula in vitro; 100 and 75 microg/ml of MQ killed schistosomula immediately; the minimal lethal and effective concentrations of MQ on schistosomula after 1 h were 25 and 5 microg/ml, respectively. Adult worms incubated with 100 and 10 microg/ml of MQ were dead after 1 h and 24 h of incubation, respectively. A hepatic shift of adult schistosomes was observed in mice already 24 h after treatment, and 120 h following treatment >98% of all worms had translocated to the liver. SEM observations revealed extensive tegumental destruction, including blebbing, shrinking and sloughing, particularly following in vitro incubation and on the tegument of female worms.
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Xiao SH, Chollet J, Utzinger J, Mei JY, Jiao PY, Keiser J, Tanner M. Effect of single-dose oral mefloquine on the morphology of adult Schistosoma japonicum in mice. Parasitol Res 2009; 105:853-61. [PMID: 19458964 DOI: 10.1007/s00436-009-1471-4] [Citation(s) in RCA: 25] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2009] [Accepted: 05/05/2009] [Indexed: 01/14/2023]
Abstract
It has been recently documented that the antimalarial drug mefloquine shows in vivo activity against schistosomes. In the present study, we assessed the effect of mefloquine on the morphology of adult Schistosoma japonicum worms. Mice were infected with S. japonicum cercariae for 35 days and then treated with a single 400-mg/kg oral dose of mefloquine. Groups of mice were killed between 24 h and 14 days post-treatment and worms were recovered from the liver and mesenteric veins, fixed in 70% alcohol, stained with acid carmine, and examined under a light microscope. Worms obtained from nontreated mice served as controls. S. japonicum recovered from mice 24 h post-treatment had severely dilated guts and the entire worm body was swollen. Meanwhile, reproductive glands, including the testis, ovary, and vitelline gland, showed signs of degeneration. Damage further progressed, particularly among vitelline glands, which resulted in disturbance of ova formation and cessation of oviposition 3 days post-treatment. Three to 7 days after mefloquine administration, adherence of host leukocytes on the damaged tegument was observed. Our results confirm that mefloquine possesses antischistosomal properties, exhibiting a rapid onset of action and causing extensive morphologic damage to adult S. japonicum.
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Affiliation(s)
- Shu-Hua Xiao
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, 200025, People's Republic of China.
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Caffrey CR, Rohwer A, Oellien F, Marhöfer RJ, Braschi S, Oliveira G, McKerrow JH, Selzer PM. A comparative chemogenomics strategy to predict potential drug targets in the metazoan pathogen, Schistosoma mansoni. PLoS One 2009; 4:e4413. [PMID: 19198654 PMCID: PMC2635471 DOI: 10.1371/journal.pone.0004413] [Citation(s) in RCA: 88] [Impact Index Per Article: 5.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2008] [Accepted: 12/15/2008] [Indexed: 12/11/2022] Open
Abstract
Schistosomiasis is a prevalent and chronic helmintic disease in tropical regions. Treatment and control relies on chemotherapy with just one drug, praziquantel and this reliance is of concern should clinically relevant drug resistance emerge and spread. Therefore, to identify potential target proteins for new avenues of drug discovery we have taken a comparative chemogenomics approach utilizing the putative proteome of Schistosoma mansoni compared to the proteomes of two model organisms, the nematode, Caenorhabditis elegans and the fruitfly, Drosophila melanogaster. Using the genome comparison software Genlight, two separate in silico workflows were implemented to derive a set of parasite proteins for which gene disruption of the orthologs in both the model organisms yielded deleterious phenotypes (e.g., lethal, impairment of motility), i.e., are essential genes/proteins. Of the 67 and 68 sequences generated for each workflow, 63 were identical in both sets, leading to a final set of 72 parasite proteins. All but one of these were expressed in the relevant developmental stages of the parasite infecting humans. Subsequent in depth manual curation of the combined workflow output revealed 57 candidate proteins. Scrutiny of these for 'druggable' protein homologs in the literature identified 35 S. mansoni sequences, 18 of which were homologous to proteins with 3D structures including co-crystallized ligands that will allow further structure-based drug design studies. The comparative chemogenomics strategy presented generates a tractable set of S. mansoni proteins for experimental validation as drug targets against this insidious human pathogen.
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Affiliation(s)
- Conor R. Caffrey
- Sandler Center for Basic Research in Parasitic Diseases, California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California, United States of America
| | - Andreas Rohwer
- Intervet Innovation GmbH, BioChemInformatics, Schwabenheim, Germany
| | - Frank Oellien
- Intervet Innovation GmbH, BioChemInformatics, Schwabenheim, Germany
| | | | - Simon Braschi
- Sandler Center for Basic Research in Parasitic Diseases, California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California, United States of America
| | - Guilherme Oliveira
- Laboratory of Cellular and Molecular Parasitology, Centro de Pesquisas René Rachou, Fundação Oswaldo Cruz, Belo Horizonte, Brazil
| | - James H. McKerrow
- Sandler Center for Basic Research in Parasitic Diseases, California Institute for Quantitative Biosciences, University of California San Francisco, San Francisco, California, United States of America
| | - Paul M. Selzer
- Intervet Innovation GmbH, BioChemInformatics, Schwabenheim, Germany
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Keiser J, Chollet J, Xiao SH, Mei JY, Jiao PY, Utzinger J, Tanner M. Mefloquine--an aminoalcohol with promising antischistosomal properties in mice. PLoS Negl Trop Dis 2009; 3:e350. [PMID: 19125172 PMCID: PMC2600813 DOI: 10.1371/journal.pntd.0000350] [Citation(s) in RCA: 161] [Impact Index Per Article: 10.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2008] [Accepted: 11/25/2008] [Indexed: 12/14/2022] Open
Abstract
BACKGROUND The treatment and control of schistosomiasis, an often neglected tropical disease that exacerbates poverty, depends on a single drug, praziquantel. The large-scale use of praziquantel might select for drug-resistant parasites, hence there is a need to develop new antischistosomal compounds. Here, we report that the antimalarial drug mefloquine possesses promising antischistosomal properties in mice. METHODOLOGY/PRINCIPAL FINDINGS A single dose of mefloquine (200 or 400 mg/kg) administered orally to mice infected with adult Schistosoma mansoni or adult S. japonicum resulted in high or complete total and female worm burden reductions (72.3%-100%). Importantly, high worm burden reductions were also observed for young developing stages of S. mansoni and S. japonicum harbored in the mouse. Both mefloquine erythro-enantiomers resulted in high and comparable total and female worm burden reductions when given to mice with either a sub-patent or patent S. mansoni infection. CONCLUSIONS/SIGNIFICANCE Our findings hold promise for the development of a novel antischistosomal drug based on an aminoalcohol functionality. Further in vitro and in vivo studies have been launched to elucidate the possible mechanism of action and to study the effect of mefloquine on S. haematobium and other trematodes. It will be interesting to investigate whether mefloquine, which is widely and effectively used for the treatment of malaria, has an impact on schistosomiasis in areas where both malaria and schistosomiasis co-exist.
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Affiliation(s)
- Jennifer Keiser
- Department of Medical Parasitology and Infection Biology, Swiss Tropical Institute, Basel, Switzerland
| | - Jacques Chollet
- Department of Medical Parasitology and Infection Biology, Swiss Tropical Institute, Basel, Switzerland
| | - Shu-Hua Xiao
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Jin-Yan Mei
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Pei-Ying Jiao
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, People's Republic of China
| | - Jürg Utzinger
- Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland
| | - Marcel Tanner
- Department of Public Health and Epidemiology, Swiss Tropical Institute, Basel, Switzerland
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Doenhoff MJ, Cioli D, Utzinger J. Praziquantel: mechanisms of action, resistance and new derivatives for schistosomiasis. Curr Opin Infect Dis 2008; 21:659-67. [PMID: 18978535 DOI: 10.1097/qco.0b013e328318978f] [Citation(s) in RCA: 522] [Impact Index Per Article: 32.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
PURPOSE OF REVIEW Praziquantel (PZQ) is the only drug being used to treat human schistosomiasis on a large scale. This review focuses on current knowledge about the mechanisms of action of PZQ, prospects for PZQ resistance, possible future alternative drugs and on exhortations that control of schistosomiasis and other so-called neglected tropical diseases becomes more integrated. RECENT FINDINGS Schistosome calcium ion (Ca2+) channels are the only moiety so far identified as the molecular target of PZQ, but the evidence remains indirect. In the presence of cytochalasin D worms survive high concentrations of PZQ and experiments with cytochalasin D also indicated that PZQ induced worm death and Ca2+ influx are not correlated. Despite PZQ being widely used, there is no clinically relevant evidence for resistance to date, but worryingly low-cure rates have been recorded in some studies in Africa. Artemisinins and the related 1,2,4-trioxolanes are new promising antischistosomal compounds, as are inhibitors of a schistosome-specific bifunctional enzyme, thioredoxin-glutathione reductase. SUMMARY Use of PZQ will increase in the foreseeable future, whether given alone or coadministered with other anthelminthics in integrated control programmes. PZQ resistance remains a threat and its prevention requires adequate monitoring of current mass drug administration programmes and development of new schistosomicides.
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Affiliation(s)
- Michael J Doenhoff
- School of Biology, University of Nottingham, University Park, Nottingham, UK.
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Antischistosomal activity of aminoalkanethiols, aminoalkanethiosulfuric acids and the corresponding disulfides. Acta Trop 2008; 108:249-55. [PMID: 18996349 DOI: 10.1016/j.actatropica.2008.10.005] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/19/2007] [Revised: 09/19/2008] [Accepted: 10/04/2008] [Indexed: 11/23/2022]
Abstract
This paper discusses the development of a series of sulfur-containing compounds that show an interesting in vivo activity against infection by Schistosoma mansoni. These substances include the aminoalkanethiols, aminoalkanethiosulfuric acids and aminoalkyl disulfides, among others. Although the aminoethanethiols and their disulfide derivatives have presented a relatively high toxicity for the host animal, the aminoalkanethiosulfuric acids have a low toxicity and a high specificity for the adult female S. mansoni worms. In vitro studies with schistosomula, lung-phase schistosomula and adult worms have demonstrated effects on the tegument and the metabolism on these different stages of S. mansoni worms. The encapsulation of these drugs in a nanoemulsion has resulted in an increase in the in vitro activity.
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Liu Q, Tian LG, Xiao SH, Qi Z, Steinmann P, Mak TK, Utzinger J, Zhou XN. Harnessing the wealth of Chinese scientific literature: schistosomiasis research and control in China. Emerg Themes Epidemiol 2008; 5:19. [PMID: 18826598 PMCID: PMC2576166 DOI: 10.1186/1742-7622-5-19] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2007] [Accepted: 09/30/2008] [Indexed: 11/24/2022] Open
Abstract
The economy of China continues to boom and so have its biomedical research and related publishing activities. Several so-called neglected tropical diseases that are most common in the developing world are still rampant or even emerging in some parts of China. The purpose of this article is to document the significant research potential from the Chinese biomedical bibliographic databases. The research contributions from China in the epidemiology and control of schistosomiasis provide an excellent illustration. We searched two widely used databases, namely China National Knowledge Infrastructure (CNKI) and VIP Information (VIP). Employing the keyword "Schistosoma" () and covering the period 1990–2006, we obtained 10,244 hits in the CNKI database and 5,975 in VIP. We examined 10 Chinese biomedical journals that published the highest number of original research articles on schistosomiasis for issues including languages and open access. Although most of the journals are published in Chinese, English abstracts are usually available. Open access to full articles was available in China Tropical Medicine in 2005/2006 and is granted by the Chinese Journal of Parasitology and Parasitic Diseases since 2003; none of the other journals examined offered open access. We reviewed (i) the discovery and development of antischistosomal drugs, (ii) the progress made with molluscicides and (iii) environmental management for schistosomiasis control in China over the past 20 years. In conclusion, significant research is published in the Chinese literature, which is relevant for local control measures and global scientific knowledge. Open access should be encouraged and language barriers removed so the wealth of Chinese research can be more fully appreciated by the scientific community.
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Affiliation(s)
- Qin Liu
- National Institute of Parasitic Diseases, Chinese Center for Disease Control and Prevention, Shanghai, PR China.
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Keiser J, Rinaldi L, Veneziano V, Mezzino L, Tanner M, Utzinger J, Cringoli G. Efficacy and safety of artemether against a natural Fasciola hepatica infection in sheep. Parasitol Res 2008; 103:517-22. [PMID: 18481085 DOI: 10.1007/s00436-008-0998-0] [Citation(s) in RCA: 47] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2008] [Accepted: 04/10/2008] [Indexed: 01/04/2023]
Abstract
Triclabendazole is the current drug of choice against Fasciola spp. infections in livestock, but resistance has become a major problem. In this study, we assessed the efficacy and safety of artemether, a derivative of artemisinin, in sheep with a low natural Fasciola hepatica infection. Artemether was administered orally or intramuscularly; sheep were monitored for 8 h posttreatment and then once daily for adverse events, and drug efficacy was estimated by fecal egg count reductions and worm burden reductions. Single 40- and 80-mg/kg oral doses of artemether showed no effect on F. hepatica egg and worm burden. Treatment with a single 160-mg/kg intramuscular dose of artemether significantly reduced the egg burden (64.9%) and worm burden (91.3%). At half this dose, a worm burden reduction of 65.3% was obtained, which was still statistically significant (P < 0.05). The lowest intramuscular dose of artemether investigated (40 mg/kg) yielded no effect on egg counts and worm burden. There were no adverse events due to artemether; however, two abortions were observed 7 days posttreatment. In conclusion, artemether shows interesting fasciocidal properties in sheep, but embryotoxicity is of concern. Further studies are warranted to assess the potential of additional artemisinin derivatives and other peroxidic compounds for the treatment of Fasciola spp. infections in different ruminants.
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Affiliation(s)
- Jennifer Keiser
- Department of Medical Parasitology and Infection Biology, Swiss Tropical Institute, Basel, Switzerland.
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Xiao SH, Jian X, Tanner M, Yong-Nian Z, Keiser J, Utzinger J, Hui-Qiang Q. Artemether, artesunate, praziquantel and tribendimidine administered singly at different dosages against Clonorchis sinensis: a comparative in vivo study. Acta Trop 2008; 106:54-9. [PMID: 18308285 DOI: 10.1016/j.actatropica.2008.01.003] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/23/2007] [Revised: 01/04/2008] [Accepted: 01/18/2008] [Indexed: 10/22/2022]
Abstract
We comparatively assessed the in vivo efficacy of artemether, artesunate, praziquantel and tribendimidine against different stages of Clonorchis sinensis. Rats were infected with 40-50 C. sinensis metacercariae, and drugs were administered singly by the oral route at different dosages. Rats were dissected 2-4 weeks post-treatment and C. sinensis trematodes were removed from the liver and bile ducts and counted. We used a negative binomial regression model to test the effect of drug and dosage in terms of worm burden reduction. Single 150 mg/kg oral doses of artesunate, artemether, tribendimidine and praziquantel, administered to rats infected with adult C. sinensis, resulted in mean worm burden reductions of 100, 100, 89.5 and 80.7%, respectively (all P<0.001). Halving the dose to 75 mg/kg still resulted in highly significant worm burden reductions for artesunate, artemether and tribendimidine (71.4-100%), but not for praziquantel (20.7%). In the juvenile infection model, a single 150 mg/kg oral dose of tribendimidine and praziquantel resulted in mean worm burden reductions of 99.1 and 90.0%, respectively, whereas considerably lower reductions were observed for artemether (59.2%) and artesunate (57.6%) when used at the same single dose. The in vivo results presented here with the artemisinins and tribendimidine provide further data for clinical investigations to assess the safety and efficacy of these drugs in clonorchiasis patients.
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Strongyloides ratti: in vitro and in vivo activity of tribendimidine. PLoS Negl Trop Dis 2008; 2:e136. [PMID: 18235851 PMCID: PMC2217669 DOI: 10.1371/journal.pntd.0000136] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2007] [Accepted: 10/29/2007] [Indexed: 11/19/2022] Open
Abstract
Background Strongyloidiasis is a truly neglected tropical disease, but its public health significance is far from being negligible. At present, only a few drugs are available for the treatment and control of strongyloidiasis. Methodology/Principal Findings We investigated the activity of tribendimidine against third-stage larvae (L3) of Strongyloides ratti in vitro and against juvenile and adult stages of the parasite in vivo. S. ratti larvae incubated in PBS buffer containing 10–100 µg/ml tribendimidine died within 24 hours. A single 50 mg/kg oral dose of tribendimidine administered to rats infected with 1-day-old S. ratti showed no effect. The same dose administered to rats harboring a 2-day-old infection showed a moderate reduction of the intestinal parasite load. Three days post-exposure a significant reduction of the immature worm burden was found. Administration of tribendimidine at doses of 50 mg/kg and above to rats harboring mature S. ratti resulted in a complete elimination of the larval and adult worm burden. For comparison, we also administered ivermectin at a single 0.5 mg/kg oral dose to rats infected with adult S. ratti and found a 90% reduction of larvae and a 100% reduction of adult worms. Conclusion/Significance Tribendimidine exhibits activity against S. ratti in vitro and in vivo. The effect of tribendimidine in humans infected with S. stercoralis should be assessed. Although an estimated 30–100 million individuals are infected with the parasitic roundworm Strongyloides stercoralis, which can cause strongyloidiasis, it is a so-called neglected tropical disease. There are only very few drugs available for treating strongyloidiasis. We evaluated the strongyloicidal properties of the anthelmintic compound tribendimidine in vitro and in an animal model. Larvae from S. ratti incubated in PBS buffer containing 10–100 µg/ml tribendimidine died within 24 hours. Tribendimidine showed a significant activity against adult S. ratti harbored in rats: oral administration of tribendimidine at single doses of 50 mg/kg and above resulted in a complete elimination of larvae and adult worms. A single 50 mg/kg oral dose of tribendimidine was less effective against the migrating tissue stages, in particular the 1- and 2-day-old S. ratti. In view of our findings, the effect of tribendimidine against S. stercoralis infections in humans should be assessed.
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Keiser J, Utzinger J, Xiao SH, Odermatt P, Tesana S. Opisthorchis viverrini: efficacy and tegumental alterations following administration of tribendimidine in vivo and in vitro. Parasitol Res 2008; 102:771-6. [DOI: 10.1007/s00436-007-0838-7] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2007] [Accepted: 11/30/2007] [Indexed: 10/22/2022]
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Xue J, Utzinger J, Zhang YN, Tanner M, Keiser J, Xiao SH. Artemether and tribendimidine lack activity in experimental treatment of Paragonimus westermani in the dog. Parasitol Res 2007; 102:537-40. [DOI: 10.1007/s00436-007-0801-7] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/29/2007] [Accepted: 10/31/2007] [Indexed: 11/29/2022]
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