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Mandalaywala R, Rana A, Ramos AL, Sampson P, Ashkenas J. Physical and pharmacokinetic characterization of Soluvec™, a novel, solvent-free aqueous ivermectin formulation. Ther Deliv 2023; 14:391-399. [PMID: 37535333 DOI: 10.4155/tde-2023-0021] [Citation(s) in RCA: 2] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 08/04/2023] Open
Abstract
Purpose: To describe application of the Quicksol™ solvent-free approach to solubilize ivermectin (IVM). Methods: Lyophilized IVM complexed with hydroxypropyl-β-cyclodextrin (HP-β-CD) was resolubilized in aqueous polysorbate-80, generating Soluvec™. Lyophilizate was examined by Fourier-transform infrared spectroscopy and differential scanning calorimetry; Soluvec, by dynamic light scattering. Pharmacokinetics was evaluated in dogs allocated to subcutaneous (SC) or intramuscular (IM) Soluvec or oral IVM. Results: IVM in Soluvec was tightly bound by HPβCD, forming nearly monodisperse 28 nm particles with solubility ∼2500-times that of free IVM. SC and IM Soluvec increased IVM exposure, peak IVM and extended duration of IVM exposure, versus oral dosing. Conclusion: The Quicksol method generated Soluvec, a concentrated aqueous parenteral IVM formulation with pharmacokinetic properties suitable for veterinary or human use.
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Affiliation(s)
- Richa Mandalaywala
- Mountain Valley MD, 260 Edgeley Blvd - Unit 4, Concord, Ontario, L4K 3Y4, Canada
| | - Azhar Rana
- Mountain Valley MD, 260 Edgeley Blvd - Unit 4, Concord, Ontario, L4K 3Y4, Canada
| | - Aubrey L Ramos
- Mountain Valley MD, 260 Edgeley Blvd - Unit 4, Concord, Ontario, L4K 3Y4, Canada
| | - Peter Sampson
- IntrinsiChem Consulting Inc., Oakville, Ontario, L6M 4A2, Canada
| | - John Ashkenas
- EquiPoise Communication, 491 Brunswick Ave, Toronto, Ontario, M5R 2Z6, Canada
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Reyes-Guerrero DE, Jiménez-Jacinto V, Alonso-Morales RA, Alonso-Díaz MÁ, Maza-Lopez J, Camas-Pereyra R, Olmedo-Juárez A, Higuera-Piedrahita RI, López-Arellano ME. Assembly and Analysis of Haemonchus contortus Transcriptome as a Tool for the Knowledge of Ivermectin Resistance Mechanisms. Pathogens 2023; 12:pathogens12030499. [PMID: 36986421 PMCID: PMC10059914 DOI: 10.3390/pathogens12030499] [Citation(s) in RCA: 9] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/27/2023] [Revised: 03/19/2023] [Accepted: 03/21/2023] [Indexed: 03/30/2023] Open
Abstract
Haemonchus contortus (Hc) is an important parasitic nematode of small ruminants. In this study we assembled the transcriptome of Hc as a model to contribute to the knowledge about the profile of the differential gene expression between two Mexican Hc strains under different anthelmintic resistance statuses, one susceptible and the other resistant to ivermectin (IVMs and IVMr, respectively), in order to improve and/or to have new strategies of control and diagnosis. The transcript sequence reads were assembled and annotated. Overall, ~127 Mbp were assembled and distributed into 77,422 transcript sequences, and 4394 transcripts of the de novo transcriptome were matched base on at least one of the following criteria: (1) Phylum Nemathelminthes and Platyhelminthes, important for animal health care, and (2) ≥55% of sequence identity with other organisms. The gene ontology (GO) enrichment analysis (GOEA) was performed to study the level of gene regulation to IVMr and IVMs strains using Log Fold Change (LFC) filtering values ≥ 1 and ≥ 2. The upregulated-displayed genes obtained via GOEA were: 1993 (for LFC ≥ 1) and 1241 (for LFC ≥ 2) in IVMr and 1929 (for LFC ≥ 1) and 835 (for LFC ≥ 2) in IVMs. The enriched GO terms upregulated per category identified the intracellular structure, intracellular membrane-bounded organelle and integral component of the cell membrane as some principal cellular components. Meanwhile, efflux transmembrane transporter activity, ABC-type xenobiotic transporter activity and ATPase-coupled transmembrane transporter activity were associated with molecular function. Responses to nematicide activity, pharyngeal pumping and positive regulation of synaptic assembly were classified as biological processes that might be involved in events related to the anthelmintic resistance (AR) and nematode biology. The filtering analysis of both LFC values showed similar genes related to AR. This study deepens our knowledge about the mechanisms behind the processes of H. contortus in order to help in tool production and to facilitate the reduction of AR and promote the development of other control strategies, such as anthelmintic drug targets and vaccines.
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Affiliation(s)
- David Emanuel Reyes-Guerrero
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Carr. Fed. Cuernavaca-Cuautla 8534, Jiutepec C.P. 62574, Morelos, Mexico
- Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Ciudad Universitaria, C.P. 04510, Ciudad de México, Mexico
| | - Verónica Jiménez-Jacinto
- Unidad Universitaria de Secuenciación Masiva y Bioinformática, Instituto de Biotecnología, Universidad Nacional Autónoma de México, Av. Universidad 2001, Chamilpa, Cuernavaca C.P. 62210, Morelos, Mexico
| | - Rogelio Alejandro Alonso-Morales
- Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Ciudad Universitaria, C.P. 04510, Ciudad de México, Mexico
| | - Miguel Ángel Alonso-Díaz
- Centro de Enseñanza, Investigación y Extensión en Ganadería Tropical, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Km. 5. Carr. Fed. Tlapacoyan-Martínez de la Torre, Martínez de la Torre C.P. 93600, Veracruz, Mexico
| | - Jocelyn Maza-Lopez
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Carr. Fed. Cuernavaca-Cuautla 8534, Jiutepec C.P. 62574, Morelos, Mexico
- Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Ciudad Universitaria, C.P. 04510, Ciudad de México, Mexico
| | - René Camas-Pereyra
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Carr. Fed. Cuernavaca-Cuautla 8534, Jiutepec C.P. 62574, Morelos, Mexico
| | - Agustín Olmedo-Juárez
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Carr. Fed. Cuernavaca-Cuautla 8534, Jiutepec C.P. 62574, Morelos, Mexico
| | - Rosa Isabel Higuera-Piedrahita
- Facultad de Estudios Superiores Cuautitlán, Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, Cuautitlán-Teoloyucan Km 2.5, Col. San Sebastián Xhala. Cuautitlán, C.P. 54714, Estado de México, Mexico
| | - María Eugenia López-Arellano
- Centro Nacional de Investigación Disciplinaria en Salud Animal e Inocuidad, Instituto Nacional de Investigaciones Forestales, Agrícolas y Pecuarias, Carr. Fed. Cuernavaca-Cuautla 8534, Jiutepec C.P. 62574, Morelos, Mexico
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Xue W, Mermans C, Papapostolou KM, Lamprousi M, Christou IK, Inak E, Douris V, Vontas J, Dermauw W, Van Leeuwen T. Untangling a Gordian knot: the role of a GluCl3 I321T mutation in abamectin resistance in Tetranychus urticae. PEST MANAGEMENT SCIENCE 2021; 77:1581-1593. [PMID: 33283957 DOI: 10.1002/ps.6215] [Citation(s) in RCA: 22] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/24/2020] [Revised: 11/03/2020] [Accepted: 12/07/2020] [Indexed: 06/12/2023]
Abstract
BACKGROUND The cys-loop ligand-gated ion channels, including the glutamate-gated chloride channel (GluCl) and GABA-gated chloride channel (Rdl) are important targets for drugs and pesticides. The macrocyclic lactone abamectin primarily targets GluCl and is commonly used to control the spider mite Tetranychus urticae, an economically important crop pest. However, abamectin resistance has been reported for multiple T. urticae populations worldwide, and in several cases was associated with the mutations G314D in GluCl1 and G326E in GluCl3. Recently, an additional I321T mutation in GluCl3 was identified in several abamectin resistant T. urticae field populations. Here, we aim to functionally validate this mutation and determine its phenotypic strength. RESULTS The GluCl3 I321T mutation was introgressed into a T. urticae susceptible background by marker-assisted backcrossing, revealing contrasting results in phenotypic strength, ranging from almost none to 50-fold. Next, we used CRISPR-Cas9 to introduce I321T, G314D and G326E in the orthologous Drosophila GluCl. Genome modified flies expressing GluCl I321T were threefold less susceptible to abamectin, while CRISPRed GluCl G314D and G326E flies were lethal. Last, functional analysis in Xenopus oocytes revealed that the I321T mutation might reduce GluCl3 sensitivity to abamectin, but also suggested that all three T. urticae Rdls are affected by abamectin. CONCLUSION Three different techniques were used to characterize the role of I321T in GluCl3 in abamectin resistance and, combining all results, our analysis suggests that the I321T mutation has a complex role in abamectin resistance. Given the reported subtle effect, additional synergistic factors in resistance warrant more investigation. © 2020 Society of Chemical Industry.
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Affiliation(s)
- Wenxin Xue
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Catherine Mermans
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Kyriaki-Maria Papapostolou
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology Hellas, Heraklion, Greece
- Department of Biology, University of Crete, Heraklion, Greece
| | - Mantha Lamprousi
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology Hellas, Heraklion, Greece
- Department of Biology, University of Crete, Heraklion, Greece
| | - Iason-Konstantinos Christou
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology Hellas, Heraklion, Greece
- Department of Biology, University of Crete, Heraklion, Greece
| | - Emre Inak
- Department of Plant Protection, Faculty of Agriculture, Ankara University, Ankara, Turkey
| | - Vassilis Douris
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology Hellas, Heraklion, Greece
- Department of Biological Applications and Technology, University of Ioannina, Ioannina, Greece
| | - John Vontas
- Institute of Molecular Biology & Biotechnology, Foundation for Research & Technology Hellas, Heraklion, Greece
- Laboratory of Pesticide Science, Department of Crop Science, Agricultural University of Athens, Athens, Greece
| | - Wannes Dermauw
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
| | - Thomas Van Leeuwen
- Department of Plants and Crops, Faculty of Bioscience Engineering, Ghent University, Ghent, Belgium
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Martin F, Dube F, Karlsson Lindsjö O, Eydal M, Höglund J, Bergström TF, Tydén E. Transcriptional responses in Parascaris univalens after in vitro exposure to ivermectin, pyrantel citrate and thiabendazole. Parasit Vectors 2020; 13:342. [PMID: 32646465 PMCID: PMC7346371 DOI: 10.1186/s13071-020-04212-0] [Citation(s) in RCA: 14] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/17/2020] [Accepted: 07/02/2020] [Indexed: 12/14/2022] Open
Abstract
Background Parascaris univalens is a pathogenic parasite of foals and yearlings worldwide. In recent years, Parascaris spp. worms have developed resistance to several of the commonly used anthelmintics, though currently the mechanisms behind this development are unknown. The aim of this study was to investigate the transcriptional responses in adult P. univalens worms after in vitro exposure to different concentrations of three anthelmintic drugs, focusing on drug targets and drug metabolising pathways. Methods Adult worms were collected from the intestines of two foals at slaughter. The foals were naturally infected and had never been treated with anthelmintics. Worms were incubated in cell culture media containing different concentrations of either ivermectin (10−9 M, 10−11 M, 10−13 M), pyrantel citrate (10−6 M, 10−8 M, 10−10 M), thiabendazole (10−5 M, 10−7 M, 10−9 M) or without anthelmintics (control) at 37 °C for 24 h. After incubation, the viability of the worms was assessed and RNA extracted from the anterior region of 36 worms and sequenced on an Illumina NovaSeq 6000 system. Results All worms were alive at the end of the incubation but showed varying degrees of viability depending on the drug and concentration used. Differential expression (Padj < 0.05 and log2 fold change ≥ 1 or ≤ − 1) analysis showed similarities and differences in the transcriptional response after exposure to the different drug classes. Candidate genes upregulated or downregulated in drug exposed worms include members of the phase I metabolic pathway short-chain dehydrogenase/reductase superfamily (SDR), flavin containing monooxygenase superfamily (FMO) and cytochrome P450-family (CYP), as well as members of the membrane transporters major facilitator superfamily (MFS) and solute carrier superfamily (SLC). Generally, different targets of the anthelmintics used were found to be upregulated and downregulated in an unspecific pattern after drug exposure, apart from the GABA receptor subunit lgc-37, which was upregulated only in worms exposed to 10−9 M of ivermectin. Conclusions To our knowledge, this is the first time the expression of lgc-37 and members of the FMO, SDR, MFS and SLC superfamilies have been described in P. univalens and future work should be focused on characterising these candidate genes to further explore their potential involvement in drug metabolism and anthelmintic resistance.![]()
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Affiliation(s)
- Frida Martin
- Division of Parasitology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Box 7036, 750 07, Uppsala, Sweden.
| | - Faruk Dube
- Division of Parasitology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Box 7036, 750 07, Uppsala, Sweden
| | - Oskar Karlsson Lindsjö
- SLU-Global Bioinformatics Centre, Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Box 7023, 750 07, Uppsala, Sweden
| | - Matthías Eydal
- Institute for Experimental Pathology at Keldur, University of Iceland, Keldnavegur 3, 112, Reykjavik, Iceland
| | - Johan Höglund
- Division of Parasitology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Box 7036, 750 07, Uppsala, Sweden
| | - Tomas F Bergström
- Department of Animal Breeding and Genetics, Swedish University of Agricultural Sciences, Box 7023, 750 07, Uppsala, Sweden
| | - Eva Tydén
- Division of Parasitology, Department of Biomedical Sciences and Veterinary Public Health, Swedish University of Agricultural Sciences, Box 7036, 750 07, Uppsala, Sweden
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Whittaker JH, Carlson SA, Jones DE, Brewer MT. Molecular mechanisms for anthelmintic resistance in strongyle nematode parasites of veterinary importance. J Vet Pharmacol Ther 2016; 40:105-115. [PMID: 27302747 DOI: 10.1111/jvp.12330] [Citation(s) in RCA: 42] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2015] [Accepted: 05/02/2016] [Indexed: 11/26/2022]
Abstract
Veterinarians rely on a relatively limited spectrum of anthelmintic agents to control nematode parasites in domestic animals. Unfortunately, anthelmintic resistance has been an emerging problem in veterinary medicine. In particular, resistance has emerged among the strongyles, a group of gastrointestinal nematodes that infect a variety of hosts that range from large herbivores to small companion animals. Over the last several decades, a great deal of research effort has been directed toward developing an understanding of the mechanisms conferring resistance against the three major groups of anthelmintics: macrocyclic lactones, benzimidazoles, and nicotinic agonists. Our understanding of anthelmintic resistance has been largely formed by determining the mechanism of action for each drug class and then evaluating drug-resistant nematode isolates for mutations or differences in expression of target genes. More recently, drug efflux pumps have been recognized for their potential contribution to anthelmintic resistance. In this mini-review, we summarize the evidence for mechanisms of resistance in strongyle nematodes.
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Affiliation(s)
- J H Whittaker
- Department of Biomedical Sciences, Iowa State University College of Veterinary Medicine, Ames, IA, USA
| | - S A Carlson
- Department of Biomedical Sciences, Iowa State University College of Veterinary Medicine, Ames, IA, USA
| | - D E Jones
- Department of Veterinary Pathology, Iowa State University College of Veterinary Medicine, Ames, IA, USA
| | - M T Brewer
- Department of Veterinary Pathology, Iowa State University College of Veterinary Medicine, Ames, IA, USA
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Wolstenholme AJ, Maclean MJ, Coates R, McCoy CJ, Reaves BJ. How do the macrocyclic lactones kill filarial nematode larvae? INVERTEBRATE NEUROSCIENCE 2016; 16:7. [PMID: 27279086 DOI: 10.1007/s10158-016-0190-7] [Citation(s) in RCA: 39] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/25/2016] [Accepted: 05/30/2016] [Indexed: 12/17/2022]
Abstract
The macrocyclic lactones (MLs) are one of the few classes of drug used in the control of the human filarial infections, onchocerciasis and lymphatic filariasis, and the only one used to prevent heartworm disease in dogs and cats. Despite their importance in preventing filarial diseases, the way in which the MLs work against these parasites is unclear. In vitro measurements of nematode motility have revealed a large discrepancy between the maximum plasma concentrations achieved after drug administration and the amounts required to paralyze worms. Recent evidence has shed new light on the likely functions of the ML target, glutamate-gated chloride channels, in filarial nematodes and supports the hypothesis that the rapid clearance of microfilariae that follows treatment involves the host immune system.
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Affiliation(s)
- Adrian J Wolstenholme
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, 30602, USA. .,Department of Infectious Diseases, College of Veterinary Medicine, 501 D. W. Brooks Drive, Athens, GA, 30602, USA.
| | - Mary J Maclean
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, 30602, USA
| | - Ruby Coates
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, 30602, USA.,Department of Biology and Biochemistry, University of Bath, Bath, BA2 7AY, UK
| | - Ciaran J McCoy
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, 30602, USA.,School of Biological Sciences, Medical Biology Centre, Queen's University, 97 Lisburn Road, Belfast, BT9 7BL, UK
| | - Barbara J Reaves
- Department of Infectious Diseases and Center for Tropical and Emerging Global Diseases, University of Georgia, Athens, GA, 30602, USA
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Rezansoff AM, Laing R, Gilleard JS. Evidence from two independent backcross experiments supports genetic linkage of microsatellite Hcms8a20, but not other candidate loci, to a major ivermectin resistance locus in Haemonchus contortus. Int J Parasitol 2016; 46:653-61. [PMID: 27216082 DOI: 10.1016/j.ijpara.2016.04.007] [Citation(s) in RCA: 24] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/20/2016] [Revised: 04/08/2016] [Accepted: 04/11/2016] [Indexed: 11/15/2022]
Abstract
Haemonchus contortus is the leading parasitic nematode species used to study anthelmintic drug resistance. A variety of candidate loci have been implicated as being associated with ivermectin resistance in this parasite but definitive evidence of their importance is still lacking. We have previously performed two independent serial backcross experiments to introgress ivermectin resistance loci from two H. contortus ivermectin-resistant strains - MHco4(WRS) and MHco10(CAVR) - into the genetic background of the ivermectin-susceptible genome reference strain MHco3(ISE). We have interrogated a number of candidate ivermectin resistance loci in the resulting backcross populations and assessed the evidence for their genetic linkage to an ivermectin resistance locus. These include the microsatellite marker Hcms8a20 and six candidate genes Hco-glc-5, Hco-avr-14, Hco-lgc-37 (previously designated Hco-hg-1), Hco-pgp-9 (previously designated Hco-pgp-1), Hco-pgp-2 and Hco-dyf-7. We have sampled the haplotype diversity of amplicon markers within, or adjacent to, each of these loci in the parental strains and fourth generation backcross populations to assess the evidence for haplotype introgression from the resistant parental strain into the genomic background of the susceptible parental strain in each backcross. The microsatellite Hcms8a20 locus showed strong evidence of such introgression in both independent backcrosses, suggesting it is linked to an important ivermectin resistance mutation in both the MHco4(WRS) and MHco10(CAVR) strains. In contrast, Hco-glc-5, Hco-avr-14, Hco-pgp-9 and Hco-dyf-7 showed no evidence of introgression in either backcross. Hco-lgc-37 and Hco-pgp-2 showed only weak evidence of introgression in the MHco3/4 backcross but not in the MHco3/10 backcross. Overall, these results suggest that microsatellite marker Hcms8a20, but not the other candidate genes tested, is linked to a major ivermectin resistance locus in the MHco4(WRS) and MHco10(CAVR) strains. This work also emphasises the need for genome-wide approaches to identify mutations responsible for the ivermectin resistance in this parasite.
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Affiliation(s)
- Andrew M Rezansoff
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Alberta, Canada
| | - Roz Laing
- Institute of Biodiversity, Animal Health and Comparative Medicine, College of Medical, Veterinary and Life Sciences, University of Glasgow, Scotland, UK
| | - John S Gilleard
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, University of Calgary, Alberta, Canada.
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Gárcia CMB, Sprenger LK, Ortiz EB, Molento MB. First report of multiple anthelmintic resistance in nematodes of sheep in Colombia. AN ACAD BRAS CIENC 2016; 88:397-402. [PMID: 26871489 DOI: 10.1590/0001-3765201620140360] [Citation(s) in RCA: 10] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/22/2014] [Accepted: 05/28/2015] [Indexed: 11/22/2022] Open
Abstract
This study aimed to report the presence of parasites resistant to the most used anthelmintic drugs in sheep in Colombia. Four farms (denominated farm 1, 2, 3 and 4) were selected where the animals were not treated with anthelmintics for two months before the trial. Animals with faecal egg count (FEC) above 150 and of different ages were allocated into six groups, each consisting of at least 5 animals. The drugs and dosages used were: ivermectin 1% (0.2 mg/kg), albendazole 25% (5 mg/kg), fenbendazole 10% (5 mg/kg), levamisole 10% (5 mg/kg), and moxidectin 1% (0.2 mg/kg). Anthelmintic efficacy was determined by the FEC reduction test (FECRT) with a second sampling 14 days post-treatment. The efficacy of albendazole and fenbendazole at farm 1 was above 95%, which was different from the others farms. The FECRT indicated the presence of multidrug resistance in the other farms where no tested drugs showed activity higher than 79% (albendazole: 0 to 55%, fenbendazole: 51.4 to 76.6%, ivermectin: 67.3 to 93.1%, levamisole: 0 to 78.1%, and moxidectin: 49.2 to 64.1%).Haemonchus contortus was the predominant (96%) species, followed by a small presence of Trichostrongylus sp. (3%) andCooperia sp. (1%). Therefore, we report for the first time the existence of multiple anthelmintic resistance in gastrointestinal nematodes of sheep in Colombia.
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Affiliation(s)
- Carlos M B Gárcia
- College of Agricultural Sciences, University of La Salle, Bogota, Colombia
| | - Lew K Sprenger
- Departamento de Medicina Veterinária, Universidade Federal do Paraná, Curitiba, PR, Brasil
| | - Efraín B Ortiz
- College of Agricultural Sciences, University of La Salle, Bogota, Colombia
| | - Marcelo B Molento
- Departamento de Medicina Veterinária, Universidade Federal do Paraná, Curitiba, PR, Brasil
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The emergence of macrocyclic lactone resistance in the canine heartworm, Dirofilaria immitis. Parasitology 2015; 142:1249-59. [PMID: 26040450 DOI: 10.1017/s003118201500061x] [Citation(s) in RCA: 58] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
Prevention of heartworm disease caused by Dirofilaria immitis in domestic dogs and cats relies on a single drug class, the macrocyclic lactones (MLs). Recently, it has been demonstrated that ML-resistant D. immitis are circulating in the Mississippi Delta region of the USA, but the prevalence and impact of these resistant parasites remains unknown. We review published studies that demonstrated resistance in D.immitis, along with our current understanding of its mechanisms. Efforts to develop in vitro tests for resistance have not yet yielded a suitable assay, so testing infected animals for microfilariae that persist in the face of ML treatment may be the best current option. Since the vast majority of D. immitis populations continue to be drug-sensitive, protected dogs are likely to be infected with only a few parasites and experience relatively mild disease. In cats, infection with small numbers of worms can cause severe disease and so the clinical consequences of drug resistance may be more severe. Since melarsomine dihydrochloride, the drug used to remove adult worms, is not an ML, the ML-resistance should have no impact on our ability to treat diseased animals. A large refugium of heartworms that are not exposed to drugs exists in unprotected dogs and in wild canids, which may limit the development and spread of resistance alleles.
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The evolution of pentameric ligand-gated ion-channels and the changing family of anthelmintic drug targets. Parasitology 2014; 142:303-17. [PMID: 25354656 DOI: 10.1017/s003118201400170x] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023]
Abstract
SUMMARY Pentameric ligand-gated ion-channels rapidly transduce synaptic neurotransmitter signals to an electrical response in post-synaptic neuronal or muscle cells and control the neuromusculature of a majority of multicellular animals. A wide range of pharmaceuticals target these receptors including ethanol, nicotine, anti-depressants and other mood regulating drugs, compounds that control pain and mobility and are targeted by a majority of anthelmintic drugs used to control parasitic infection of humans and livestock. Major advances have been made in recent years to our understanding of the structure, function, activity and the profile of compounds that can activate specific receptors. It is becoming clear that these anthelmintic drug targets are not fixed, but differ in significant details from one nematode species to another. Here we review what is known about the evolution of the pentameric ligand-gated ion-channels, paying particular attention to the nematodes, how we can infer the origins of such receptors and understand the factors that determine how they change both over time and from one species to another. Using this knowledge provides a biological framework in which to understand these important drug targets and avenues to identify new receptors and aid the search for new anthelmintic drugs.
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Laing R, Kikuchi T, Martinelli A, Tsai IJ, Beech RN, Redman E, Holroyd N, Bartley DJ, Beasley H, Britton C, Curran D, Devaney E, Gilabert A, Hunt M, Jackson F, Johnston SL, Kryukov I, Li K, Morrison AA, Reid AJ, Sargison N, Saunders GI, Wasmuth JD, Wolstenholme A, Berriman M, Gilleard JS, Cotton JA. The genome and transcriptome of Haemonchus contortus, a key model parasite for drug and vaccine discovery. Genome Biol 2013; 14:R88. [PMID: 23985316 PMCID: PMC4054779 DOI: 10.1186/gb-2013-14-8-r88] [Citation(s) in RCA: 263] [Impact Index Per Article: 23.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2013] [Revised: 06/27/2013] [Accepted: 08/28/2013] [Indexed: 11/10/2022] Open
Abstract
BACKGROUND The small ruminant parasite Haemonchus contortus is the most widely used parasitic nematode in drug discovery, vaccine development and anthelmintic resistance research. Its remarkable propensity to develop resistance threatens the viability of the sheep industry in many regions of the world and provides a cautionary example of the effect of mass drug administration to control parasitic nematodes. Its phylogenetic position makes it particularly well placed for comparison with the free-living nematode Caenorhabditis elegans and the most economically important parasites of livestock and humans. RESULTS Here we report the detailed analysis of a draft genome assembly and extensive transcriptomic dataset for H. contortus. This represents the first genome to be published for a strongylid nematode and the most extensive transcriptomic dataset for any parasitic nematode reported to date. We show a general pattern of conservation of genome structure and gene content between H. contortus and C. elegans, but also a dramatic expansion of important parasite gene families. We identify genes involved in parasite-specific pathways such as blood feeding, neurological function, and drug metabolism. In particular, we describe complete gene repertoires for known drug target families, providing the most comprehensive understanding yet of the action of several important anthelmintics. Also, we identify a set of genes enriched in the parasitic stages of the lifecycle and the parasite gut that provide a rich source of vaccine and drug target candidates. CONCLUSIONS The H. contortus genome and transcriptome provide an essential platform for postgenomic research in this and other important strongylid parasites.
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Affiliation(s)
- Roz Laing
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 464 Bearsden Road, Glasgow, Scotland, G61 1QH, UK
| | - Taisei Kikuchi
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
- Division of Parasitology, Department of Infectious Disease, Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692 Japan
| | - Axel Martinelli
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Isheng J Tsai
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
- Division of Parasitology, Department of Infectious Disease, Faculty of Medicine, University of Miyazaki, Miyazaki, 889-1692 Japan
| | - Robin N Beech
- Institute of Parasitology, Macdonald Campus, McGill University, 21,111 Lakeshore Road, Ste. Anne de Bellevue, Québec, Canada H9X 3V9
| | - Elizabeth Redman
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, Faculty of Veterinary Medicine, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - Nancy Holroyd
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - David J Bartley
- Disease Control, Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK
| | - Helen Beasley
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Collette Britton
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 464 Bearsden Road, Glasgow, Scotland, G61 1QH, UK
| | - David Curran
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, Faculty of Veterinary Medicine, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - Eileen Devaney
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 464 Bearsden Road, Glasgow, Scotland, G61 1QH, UK
| | - Aude Gilabert
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, Faculty of Veterinary Medicine, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - Martin Hunt
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Frank Jackson
- Disease Control, Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK
| | - Stephanie L Johnston
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 464 Bearsden Road, Glasgow, Scotland, G61 1QH, UK
| | - Ivan Kryukov
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, Faculty of Veterinary Medicine, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - Keyu Li
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, Faculty of Veterinary Medicine, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - Alison A Morrison
- Disease Control, Moredun Research Institute, Pentlands Science Park, Bush Loan, Penicuik, Midlothian, EH26 0PZ, UK
| | - Adam J Reid
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - Neil Sargison
- Royal (Dick) School of Veterinary Studies, University of Edinburgh, Easter Bush Veterinary Centre, Roslin, Midlothian EH25 9RG, Scotland, UK
| | - Gary I Saunders
- Institute of Infection, Immunity and Inflammation, College of Medical, Veterinary and Life Sciences, University of Glasgow, 464 Bearsden Road, Glasgow, Scotland, G61 1QH, UK
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - James D Wasmuth
- Department of Ecosystem and Public Health, Faculty of Veterinary Medicine, Faculty of Veterinary Medicine, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - Adrian Wolstenholme
- Department of Infectious Diseases and Center for Tropical and Emerging Global Disease, University of Georgia, Athens, Georgia 30602, USA
| | - Matthew Berriman
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
| | - John S Gilleard
- Department of Comparative Biology and Experimental Medicine, Faculty of Veterinary Medicine, Faculty of Veterinary Medicine, 3330 Hospital Drive NW, Calgary, Alberta, Canada T2N 1N4
| | - James A Cotton
- Wellcome Trust Sanger Institute, Wellcome Trust Genome Campus, Hinxton, Cambridge, CB10 1SA, UK
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Prichard R, Ménez C, Lespine A. Moxidectin and the avermectins: Consanguinity but not identity. INTERNATIONAL JOURNAL FOR PARASITOLOGY-DRUGS AND DRUG RESISTANCE 2012; 2:134-53. [PMID: 24533275 DOI: 10.1016/j.ijpddr.2012.04.001] [Citation(s) in RCA: 168] [Impact Index Per Article: 14.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/01/2012] [Revised: 03/29/2012] [Accepted: 04/01/2012] [Indexed: 01/16/2023]
Abstract
The avermectins and milbemycins contain a common macrocyclic lactone (ML) ring, but are fermentation products of different organisms. The principal structural difference is that avermectins have sugar groups at C13 of the macrocyclic ring, whereas the milbemycins are protonated at C13. Moxidectin (MOX), belonging to the milbemycin family, has other differences, including a methoxime at C23. The avermectins and MOX have broad-spectrum activity against nematodes and arthropods. They have similar but not identical, spectral ranges of activity and some avermectins and MOX have diverse formulations for great user flexibility. The longer half-life of MOX and its safety profile, allow MOX to be used in long-acting formulations. Some important differences between MOX and avermectins in interaction with various invertebrate ligand-gated ion channels are known and could be the basis of different efficacy and safety profiles. Modelling of IVM interaction with glutamate-gated ion channels suggest different interactions will occur with MOX. Similarly, profound differences between MOX and the avermectins are seen in interactions with ABC transporters in mammals and nematodes. These differences are important for pharmacokinetics, toxicity in animals with defective transporter expression, and probable mechanisms of resistance. Resistance to the avermectins has become widespread in parasites of some hosts and MOX resistance also exists and is increasing. There is some degree of cross-resistance between the avermectins and MOX, but avermectin resistance and MOX resistance are not identical. In many cases when resistance to avermectins is noticed, MOX produces a higher efficacy and quite often is fully effective at recommended dose rates. These similarities and differences should be appreciated for optimal decisions about parasite control, delaying, managing or reversing resistances, and also for appropriate anthelmintic combination.
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Affiliation(s)
- Roger Prichard
- Institute of Parasitology, McGill University, Montreal, Canada
| | - Cécile Ménez
- INRA, UMR 1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France ; Université de Toulouse, INP, UMR 1331, Toxalim, F-31000 Toulouse, France
| | - Anne Lespine
- INRA, UMR 1331, Toxalim, Research Centre in Food Toxicology, F-31027 Toulouse, France ; Université de Toulouse, INP, UMR 1331, Toxalim, F-31000 Toulouse, France
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Millares P, LaCourse EJ, Perally S, Ward DA, Prescott MC, Hodgkinson JE, Brophy PM, Rees HH. Proteomic profiling and protein identification by MALDI-TOF mass spectrometry in unsequenced parasitic nematodes. PLoS One 2012; 7:e33590. [PMID: 22479418 PMCID: PMC3315570 DOI: 10.1371/journal.pone.0033590] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2011] [Accepted: 02/16/2012] [Indexed: 11/19/2022] Open
Abstract
Lack of genomic sequence data and the relatively high cost of tandem mass spectrometry have hampered proteomic investigations into helminths, such as resolving the mechanism underpinning globally reported anthelmintic resistance. Whilst detailed mechanisms of resistance remain unknown for the majority of drug-parasite interactions, gene mutations and changes in gene and protein expression are proposed key aspects of resistance. Comparative proteomic analysis of drug-resistant and -susceptible nematodes may reveal protein profiles reflecting drug-related phenotypes. Using the gastro-intestinal nematode, Haemonchus contortus as case study, we report the application of freely available expressed sequence tag (EST) datasets to support proteomic studies in unsequenced nematodes. EST datasets were translated to theoretical protein sequences to generate a searchable database. In conjunction with matrix-assisted laser desorption ionisation time-of-flight mass spectrometry (MALDI-TOF-MS), Peptide Mass Fingerprint (PMF) searching of databases enabled a cost-effective protein identification strategy. The effectiveness of this approach was verified in comparison with MS/MS de novo sequencing with searching of the same EST protein database and subsequent searches of the NCBInr protein database using the Basic Local Alignment Search Tool (BLAST) to provide protein annotation. Of 100 proteins from 2-DE gel spots, 62 were identified by MALDI-TOF-MS and PMF searching of the EST database. Twenty randomly selected spots were analysed by electrospray MS/MS and MASCOT Ion Searches of the same database. The resulting sequences were subjected to BLAST searches of the NCBI protein database to provide annotation of the proteins and confirm concordance in protein identity from both approaches. Further confirmation of protein identifications from the MS/MS data were obtained by de novo sequencing of peptides, followed by FASTS algorithm searches of the EST putative protein database. This study demonstrates the cost-effective use of available EST databases and inexpensive, accessible MALDI-TOF MS in conjunction with PMF for reliable protein identification in unsequenced organisms.
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Affiliation(s)
- Paul Millares
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | | | - Samirah Perally
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Aberystwyth, United Kingdom
| | - Deborah A. Ward
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Mark C. Prescott
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
| | - Jane E. Hodgkinson
- Institute of Infection and Global Health, University of Liverpool, Liverpool, United Kingdom
| | - Peter M. Brophy
- Institute of Biological, Environmental and Rural Sciences (IBERS), Aberystwyth University, Aberystwyth, United Kingdom
| | - Huw H. Rees
- Institute of Integrative Biology, University of Liverpool, Liverpool, United Kingdom
- * E-mail:
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Accardi MV, Beech RN, Forrester SG. Nematode cys-loop GABA receptors: biological function, pharmacology and sites of action for anthelmintics. INVERTEBRATE NEUROSCIENCE 2012; 12:3-12. [PMID: 22430311 DOI: 10.1007/s10158-012-0129-6] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/03/2012] [Accepted: 03/03/2012] [Indexed: 10/28/2022]
Abstract
Parasitic nematode infection of humans and livestock is a major problem globally. Attempts to control nematode populations have led to the development of several classes of anthelmintic, which target cys-loop ligand-gated ion channels. Unlike the vertebrate nervous system, the nematode nervous system possesses a large and diversified array of ligand-gated chloride channels that comprise key components of the inhibitory neurotransmission system. In particular, cys-loop GABA receptors have evolved to play many fundamental roles in nematode behaviour such as locomotion. Analysis of the genomes of several free-living and parasitic nematodes suggests that there are several groups of cys-loop GABA receptor subunits that, for the most part, are conserved among nematodes. Despite many similarities with vertebrate cys-loop GABA receptors, those in nematodes are quite distinct in sequence similarity, subunit composition and biological function. With rising anthelmintic resistance in many nematode populations worldwide, GABA receptors should become an area of increased scientific investigation in the development of the next generation of anthelmintics.
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Affiliation(s)
- Michael V Accardi
- Department of Pharmacology and Therapeutics, McGill University, Bellini Life Sciences Complex, 3649 Sir William Osler Promenade, Montreal, QC H3G 0B1, Canada
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Candidate anthelmintic resistance-associated gene expression and sequence polymorphisms in a triple-resistant field isolate of Haemonchus contortus. Mol Biochem Parasitol 2011; 180:99-105. [DOI: 10.1016/j.molbiopara.2011.09.003] [Citation(s) in RCA: 93] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/29/2011] [Revised: 09/01/2011] [Accepted: 09/06/2011] [Indexed: 11/24/2022]
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Pharmacological characterization of the Haemonchus contortus GABA-gated chloride channel, Hco-UNC-49: modulation by macrocyclic lactone anthelmintics and a receptor for piperazine. Vet Parasitol 2011; 185:201-9. [PMID: 22075040 DOI: 10.1016/j.vetpar.2011.10.006] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/15/2011] [Revised: 09/28/2011] [Accepted: 10/07/2011] [Indexed: 11/20/2022]
Abstract
Invertebrate ligand-gated chloride channels are well recognized as important targets for several insecticides and anthelmintics. Hco-UNC-49 is a GABA-gated chloride channel from the parasitic nematode Haemonchus contortus and is an orthologue to the neuromuscular receptor (Cel-UNC-49) from the free-living nematode Caenorhabditis elegans. While the receptors from the two nematodes are similar in sequence, they exhibit different sensitivities to GABA which may reflect differences in in vivo function. The aim of the current study was to further characterize the pharmacology of the Hco-UNC-49 receptor by examining its sensitivity to various insecticides and anthelmintics using two-electrode voltage clamp. Specifically, the insecticides fipronil and picrotoxin appear to inhibit the channel in a similar manner. The IC(50) of picrotoxin on the homomeric channel was 3.65 ± 0.64 μM and for the heteromeric channel was 134.56 ± 44.12 μM. On the other hand, dieldrin, a well-known insect GABA receptor blocker, had little effect on the UNC-49 channel. The anthelmintics ivermectin and moxidectin both moderately potentiated the activation of Hco-UNC-49 by GABA, while piperazine was able to directly activate both the Hco-UNC-49 homomeric and heteromeric channels with EC(50) values of 6.23 ± 0.45 mM and 5.09 ± 0.32 mM, respectively. This piperazine current was reversibly blocked by picrotoxin which demonstrates that the anthelmintic specifically targets Hco-UNC-49. These results demonstrate that Hco-UNC-49 exhibits binding sites for several molecules including piperazine and macrocyclic lactone anthelmintics. In addition, this is the first report of the heterologous expression and subsequent characterization of a receptor for piperazine.
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Ali A, Cablewski T, Francis CL, Ganguly AK, Sargent RM, Sawutz DG, Winzenberg KN. 2-Phenylimidazo[1,2-b]pyridazine derivatives highly active against Haemonchus contortus. Bioorg Med Chem Lett 2011; 21:4160-3. [DOI: 10.1016/j.bmcl.2011.05.096] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2011] [Revised: 05/24/2011] [Accepted: 05/25/2011] [Indexed: 11/28/2022]
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Abstract
Since 1977, >2000 research papers described attempts to detect, identify and/or quantify parasites, or disease organisms carried by ecto-parasites, using DNA-based tests and 148 reviews of the topic were published. Despite this, only a few DNA-based tests for parasitic diseases are routinely available, and most of these are optional tests used occasionally in disease diagnosis. Malaria, trypanosomiasis, toxoplasmosis, leishmaniasis and cryptosporidiosis diagnosis may be assisted by DNA-based testing in some countries, but there are very few cases where the detection of veterinary parasites is assisted by DNA-based tests. The diagnoses of some bacterial (e.g. lyme disease) and viral diseases (e.g. tick borne encephalitis) which are transmitted by ecto-parasites more commonly use DNA-based tests, and research developing tests for these species makes up almost 20% of the literature. Other important uses of DNA-based tests are for epidemiological and risk assessment, quality control for food and water, forensic diagnosis and in parasite biology research. Some DNA-based tests for water-borne parasites, including Cryptosporidium and Giardia, are used in routine checks of water treatment, but forensic and food-testing applications have not been adopted in routine practice. Biological research, including epidemiological research, makes the widest use of DNA-based diagnostics, delivering enhanced understanding of parasites and guidelines for managing parasitic diseases. Despite the limited uptake of DNA-based tests to date, there is little doubt that they offer great potential to not only detect, identify and quantify parasites, but also to provide further information important for the implementation of parasite control strategies. For example, variant sequences within species of parasites and other organisms can be differentiated by tests in a manner similar to genetic testing in medicine or livestock breeding. If an association between DNA sequence and phenotype has been demonstrated, then qualities such as drug resistance, strain divergence, virulence, and origin of isolates could be inferred by DNA-based tests. No such tests are in clinical or commercial use in parasitology and few tests are available for other organisms. Why have DNA-based tests not had a bigger impact in veterinary and human medicine? To explore this question, technological, biological, economic and sociological factors must be considered. Additionally, a realistic expectation of research progress is needed. DNA-based tests could enhance parasite management in many ways, but patience, persistence and dedication will be needed to achieve this goal.
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