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Isabelle Arzul - One of the best experts on this subject based on the ideXlab platform.
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An eDNA/eRNA-based approach to investigate the life cycle of non-cultivable shellfish micro-parasites: the case of Bonamia ostreae, a parasite of the European flat oyster Ostrea edulis.
Microbial biotechnology, 2020Co-Authors: Nicolas Merou, Cyrielle Lecadet, Stephane Pouvreau, Isabelle ArzulAbstract:Environmental DNA approaches are increasingly used to detect microorganisms in environmental compartments, including water. They show considerable advantages to study non-cultivable microorganisms like Bonamia ostreae, a protozoan parasite inducing significant mortality in populations of flat oyster Ostrea edulis. Although B. ostreae development within the host has been well described, questions remain about its behaviour in the environment. As B. ostreae transmission is direct, seawater appears as an interesting target to develop early detection tools and improve our understanding of disease transmission mechanisms. In this context, we have developed an eDNA/eRNA approach allowing detecting and quantifying B. ostreae 18S rDNA/rRNA as well as monitoring its presence in seawater by real-time PCR. B. ostreae DNA could be detected up to 4 days while RNA could be detected up to 30 days, suggesting a higher sensitivity of the eRNA-based tool. Additionally, more than 90% of shed parasites were no longer detected after 2 days outside the oysters. By allowing B. ostreae detection in seawater, this approach would not only be useful to monitor the presence of the parasite in oyster production areas but also to evaluate the effect of changing environmental factors on parasite survival and transmission.
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an edna erna based approach to investigate the life cycle of non cultivable shellfish micro parasites the case of Bonamia ostreae a parasite of the european flat oyster ostrea edulis
Microbial Biotechnology, 2020Co-Authors: Nicolas Merou, Cyrielle Lecadet, Stephane Pouvreau, Isabelle ArzulAbstract:Environmental DNA approaches are increasingly used to detect microorganisms in environmental compartments, including water. They show considerable advantages to study non-cultivable microorganisms like Bonamia ostreae, a protozoan parasite inducing significant mortality in populations of flat oyster Ostrea edulis. Although B. ostreae development within the host has been well described, questions remain about its behaviour in the environment. As B. ostreae transmission is direct, seawater appears as an interesting target to develop early detection tools and improve our understanding of disease transmission mechanisms. In this context, we have developed an eDNA/eRNA approach allowing detecting and quantifying B. ostreae 18S rDNA/rRNA as well as monitoring its presence in seawater by real-time PCR. B. ostreae DNA could be detected up to 4 days while RNA could be detected up to 30 days, suggesting a higher sensitivity of the eRNA-based tool. Additionally, more than 90% of shed parasites were no longer detected after 2 days outside the oysters. By allowing B. ostreae detection in seawater, this approach would not only be useful to monitor the presence of the parasite in oyster production areas but also to evaluate the effect of changing environmental factors on parasite survival and transmission.
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is pallial mucus involved in ostrea edulis defenses against the parasite Bonamia ostreae
Journal of Invertebrate Pathology, 2020Co-Authors: Bruno Chollet, Maria Pradoalvarez, Ophelie Gervais, Sergio Fernandezboo, Stephane Claverol, Cyrielle Lecadet, Christine Dubreuil, Isabelle ArzulAbstract:Abstract Bonamia ostreae is an intrahemocytic parasite that has been responsible for severe mortalities in the flat oyster Ostrea edulis since the 1970s. The Pacific oyster Crassostrea gigas is considered to be resistant to the disease and appears to have mechanisms to avoid infection. Most studies carried out on the invertebrate immune system focus on the role of hemolymph, although mucus, which covers the body surface of molluscs, could also act as a barrier against pathogens. In this study, the in vitro effect of mucus from the oyster species Ostrea edulis and C. gigas on B. ostreae was investigated using flow cytometry. Results showed an increase in esterase activities and mortality rate of parasites exposed to mucus from both oyster species. In order to better understand the potential role of mucus in the defense of the oyster against parasites such as B. ostreae, liquid chromatography and tandem mass spectrometry were used to describe and compare mucus protein composition from both species. In all oyster species, pallial mucus contains a high level of proteins; however, O. edulis mucus produced a variety of proteins that could be involved in the immune response against the parasite, including Cu/Zn extracellular superoxide dismutase, thioxiredoxin, peroxiredon VI, heat shock protein 90 as well as several hydrolases. Conversely, a different set of antioxidant proteins, hydrolases and stress related proteins were identified in mucus from C. gigas. Our results suggest an innate immunity adaptation of oysters to develop a specific response against their respective pathogens. The mucosal protein composition also provides new insights for further investigations into the immune response in oysters.
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involvement of apoptosis in the dialogue between the parasite Bonamia ostreae and the flat oyster ostrea edulis
Fish & Shellfish Immunology, 2019Co-Authors: Ophelie Gervais, Bruno Chollet, Chunyan Feng, Cyrielle Lecadet, Christine Dubreuil, Serena Durante, Cyril Henard, Delphine Serpin, Renault Tristan, Isabelle ArzulAbstract:The protozoan parasite Bonamia ostreae has been associated with the decline of flat oyster Ostrea edulis populations in some European countries. Control of shellfish diseases mostly relies on prevention measures including transfer restrictions and stock management measures such as breeding programmes. These prevention and mitigation measures require a better understanding of interactions between host and pathogens. Previous in vitro studies allowed identifying apoptosis as a mechanism activated by the flat oyster in response to B. ostreae. However, these experiments also suggested that the parasite is able to regulate apoptosis in order to survive and multiply within hemocytes. By simplifying the conditions of infection, in vitro studies allow identifying most distinct features of the response of the host. In order to appreciate the relative importance of apoptosis in this response at the oyster scale, in vivo trials were carried out by injecting with parasites oysters from two French locations, Quiberon Bay (Brittany) and Diana Lagoon (Corsica). Apoptosis was investigated on pools of hemolymph from oysters collected at early and later times after injection using previously developed tools. Apoptotic cellular activities including intracytoplasmic calcium concentration, mitochondrial membrane potential and phosphatidyl serine externalization were analysed using flow cytometry. Moreover, the expression of flat oyster genes involved in both extrinsic and intrinsic pathways was measured using real time quantitative PCR.
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contribution of in vivo experimental challenges to understanding flat oyster ostrea edulis resistance to Bonamia ostreae
Frontiers in Cellular and Infection Microbiology, 2017Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Estelle Harrang, Sylvie Lapegue, Bruno Chollet, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analysed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analysed by flow cytometry. Four genes homologous to genes shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls, phagocytosis allow parasite degradation, but it also contribute to spreading of B. ostreae infection. Infected selected oyster show a lower phagocytosis activity might be a solution against the parasite infection. The expression of the OeIAP gene and OeFas-ligand gene was significantly increased in selected oysters at 5 days post injection. OeIAP gene expression appeared significantly increased in wild-type oysters at 8 days post injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.
Benjamin Morga - One of the best experts on this subject based on the ideXlab platform.
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Etude des interactions hôte/parasite chez l'huître plate Ostrea edulis et son parasite Bonamia ostreae, Study of host/parasite interactions in the flat oyster Ostrea edulis and the parasite Bonamia ostreae
2020Co-Authors: Benjamin MorgaAbstract:The history of the French oyster production highlights the fragility of this production against overexploitation and disease outbreaks. In particular, the production of flot oyster, Ostrea edulis, has decreased following the emergence of two parasitic diseases including bonamiosis. The means to fight against bonamiosis are relatively limited. They are mainly based on oyster health surveillance to limit the spread of the disease. However, the use of predictive models of disease progression in infected area would help to improve stock management and minimize the impact pathogens. Moreover the development of resistant animais could help to revive this production. These different approaches require appropriate diagnostic tools, a good knowledge of the life cycle of the pathogen, and the interactions between the parasite and its host. In this context, the main objective of the phD work is to understand the interactions between the fiat oyster Ostrea edulis and the parasite Bonamia ostreae, and particularly the molecular basis of the resistance to the parasite. In a first step, a subtractive cDNA bank allowed the identification of ESTs differentially expressed in haemocytes in response to the parasite. Expression of some genes, among which a galectin, was measured by Real lime PCR in the context of in vitro infections. In addition, the cellular response was investigated by flow cytometry and the infection was checked by microscopy. These experiments showed a multiplication of the parasite inside haemocytes assoclated with a decreased of esterases and of the production of ROS. In a second step, a comparative approach was carried out between a population of oysters resistant to bonamiosis and a natural population. Results suggest that modulation of apopotosis and decrease of phagocytosis could be involved in mechanisms related to resistance to bonamiosis...
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contribution of in vivo experimental challenges to understanding flat oyster ostrea edulis resistance to Bonamia ostreae
Frontiers in Cellular and Infection Microbiology, 2017Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Estelle Harrang, Sylvie Lapegue, Bruno Chollet, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analysed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analysed by flow cytometry. Four genes homologous to genes shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls, phagocytosis allow parasite degradation, but it also contribute to spreading of B. ostreae infection. Infected selected oyster show a lower phagocytosis activity might be a solution against the parasite infection. The expression of the OeIAP gene and OeFas-ligand gene was significantly increased in selected oysters at 5 days post injection. OeIAP gene expression appeared significantly increased in wild-type oysters at 8 days post injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.
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Contribution of in Vivo Experimental Challenges to Understanding Flat Oyster Ostrea edulis Resistance to Bonamia ostreae
Frontiers in Cellular and Infection Microbiology, 2017Co-Authors: Benjamin Morga, Barthelemy Chollet, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Estelle Harrang, Sylvie Lapegue, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in European flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand the mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analyzed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analyzed by flow cytometry. Four genes homologous to those shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD, and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls. Infected selected oyster show a lower phagocytosis activity which might be a protection against the parasite infection. The expression of OeIAP and OeFas-ligand gene was significantly increased in selected oysters at 5 days post-injection. OeIAP gene expression appeared to be significantly increased in wild-type oysters at 8 days post-injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.
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heat shock protein 90 of Bonamia ostreae characterization and possible correlation with infection of the flat oyster ostrea edulis
Journal of Eukaryotic Microbiology, 2013Co-Authors: Maria Pradoalvarez, Benjamin Morga, Bruno Chollet, Yann Couraleau, Isabelle ArzulAbstract:In this study, we described the cytosolic HSP90 of Bonamia ostreae, an intracellular parasite of Ostrea edulis hemocytes. The complete open reading frame was assembled by Rapid Amplification cDNA Ends reactions on cDNA of B. ostreae-infected hemocytes. HSP90 amplification was corroborated in infected oysters and B. ostreae purified cells. The functionality of the HSP90, studied by inhibitory assays with radicicol, suggests that this protein may play a role in hemocyte invasion. Our results inform the molecular basis that governs B. ostreae-O. edulis interactions.
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new insights in flat oyster ostrea edulis resistance against the parasite Bonamia ostreae
Fish & Shellfish Immunology, 2012Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality in flat oyster stocks in Europe. Control of the disease currently relies on disease management practices and transfer restriction. Previously, massal selections based on survival to challenge to infection with B. ostreae have been applied to produce flat oyster families with resistant progeny. In an attempt to understand the molecular mechanisms involved in disease resistance, differentially expressed sequence tags between resistant and wild Ostrea edulis haemocytes, both infected with the parasite, were identified using suppression subtractive hybridisation. Expression of seven ESTs has been studied using quantitative reverse-transcriptase PCR. The base-line expression of an extracellular superoxide dismutase, inhibitor of apoptosis (OeIAP), Fas ligand (OeFas-ligand) and Cathepsin B was significantly increased, whilst cyclophilin B appeared significantly decreased in resistant oysters. Considering their great interest for further studies, the open reading frames of the OeFas-ligand and OeIAP were completely sequenced.
Tristan Renault - One of the best experts on this subject based on the ideXlab platform.
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contribution of in vivo experimental challenges to understanding flat oyster ostrea edulis resistance to Bonamia ostreae
Frontiers in Cellular and Infection Microbiology, 2017Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Estelle Harrang, Sylvie Lapegue, Bruno Chollet, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analysed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analysed by flow cytometry. Four genes homologous to genes shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls, phagocytosis allow parasite degradation, but it also contribute to spreading of B. ostreae infection. Infected selected oyster show a lower phagocytosis activity might be a solution against the parasite infection. The expression of the OeIAP gene and OeFas-ligand gene was significantly increased in selected oysters at 5 days post injection. OeIAP gene expression appeared significantly increased in wild-type oysters at 8 days post injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.
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Contribution of in Vivo Experimental Challenges to Understanding Flat Oyster Ostrea edulis Resistance to Bonamia ostreae
Frontiers in Cellular and Infection Microbiology, 2017Co-Authors: Benjamin Morga, Barthelemy Chollet, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Estelle Harrang, Sylvie Lapegue, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in European flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand the mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analyzed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analyzed by flow cytometry. Four genes homologous to those shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD, and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls. Infected selected oyster show a lower phagocytosis activity which might be a protection against the parasite infection. The expression of OeIAP and OeFas-ligand gene was significantly increased in selected oysters at 5 days post-injection. OeIAP gene expression appeared to be significantly increased in wild-type oysters at 8 days post-injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.
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flat oyster follows the apoptosis pathway to defend against the protozoan parasite Bonamia ostreae
Fish & Shellfish Immunology, 2016Co-Authors: Ophelie Gervais, Tristan Renault, Bruno Chollet, Isabelle ArzulAbstract:The in vitro model Ostrea edulis hemocyte - Bonamia ostreae is interesting to investigate host-parasite interactions at the cellular level. Indeed, this unicellular parasite infects the flat oyster Ostrea edulis and multiplies within hemocytes, the central effectors of oyster defenses. Apoptosis is a mechanism used by many organisms to eliminate infected cells. In order to study the potential involvement of this mechanism in the oyster response to B. ostreae, in vitro experiments were carried out by exposing hemocytes from the naturally susceptible oyster O. edulis and a resistant oyster species Crassostrea gigas to live and heat-inactivated parasites. Hemocyte apoptotic response was measured using a combination of flow cytometry and microscopy analyses. Whatever the host species was, the parasite was engulfed in hemocytes and induced an increase of apoptotic parameters including intracytoplasmic calcium concentration, mitochondrial membrane potential or phosphatidyl-serine externalization as well as ultrastructural modifications. However, the parasite appears more able to infect flat oyster than cupped oyster hemocytes and the apoptotic response was more important against live than dead parasites in the natural host than in C. gigas. Our results suggest that O. edulis specifically responds to B. ostreae by inducing apoptosis of hemocytes.
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new insights in flat oyster ostrea edulis resistance against the parasite Bonamia ostreae
Fish & Shellfish Immunology, 2012Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality in flat oyster stocks in Europe. Control of the disease currently relies on disease management practices and transfer restriction. Previously, massal selections based on survival to challenge to infection with B. ostreae have been applied to produce flat oyster families with resistant progeny. In an attempt to understand the molecular mechanisms involved in disease resistance, differentially expressed sequence tags between resistant and wild Ostrea edulis haemocytes, both infected with the parasite, were identified using suppression subtractive hybridisation. Expression of seven ESTs has been studied using quantitative reverse-transcriptase PCR. The base-line expression of an extracellular superoxide dismutase, inhibitor of apoptosis (OeIAP), Fas ligand (OeFas-ligand) and Cathepsin B was significantly increased, whilst cyclophilin B appeared significantly decreased in resistant oysters. Considering their great interest for further studies, the open reading frames of the OeFas-ligand and OeIAP were completely sequenced.
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cellular and molecular responses of haemocytes from ostrea edulis during in vitro infection by the parasite Bonamia ostreae
International Journal for Parasitology, 2011Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Bruno Chollet, Isabelle ArzulAbstract:Abstract Bonamia ostreae is a protozoan, affiliated to the order Haplosporidia and to the phylum Cercozoa. This parasite is intracellular and infects haemocytes, cells notably involved in oyster defence mechanisms. Bonamiosis due to the parasite B. ostreae is a disease affecting the flat oyster, Ostrea edulis. The strategies used by protozoan parasites to circumvent host defence mechanisms remain largely unknown in marine bivalve molluscs. In the present work, in vitro experiments were carried out in order to study the interactions between haemocytes from O. edulis and purified parasite, B. ostreae. We monitored cellular and molecular responses of oyster haemocytes by light microscopy, flow cytometry and real-time PCR 1, 2, 4 and 8 h p.i. Light microscopy was used to measure parasite phagocytosis by oyster haemocytes. Parasites were observed inside haemocytes 1 h p.i. and the parasite number increased during the time course of the experiment. Moreover, some bi-nucleated and tri-nucleated parasites were found within haemocytes 2 and 4 h p.i., respectively, suggesting that the parasite can divide inside haemocytes. Host responses to B. ostreae were investigated at the cellular and molecular levels using flow cytometry and real-time PCR. Phagocytosis capacity of haemocytes, esterase activity and production of radical oxygen species appeared modulated during the infection with B. ostreae. Expression levels of expressed sequence tags selected in this study showed variations during the experiment as soon as 1 h p.i. An up-regulation of galectin (OeGal), cytochrome p450 (CYP450), lysozyme, omega GST (OGST), super oxide dismutase Cu/Zn (Oe-SOD Cu/Zn) and a down-regulation of the extracellular super oxide dismutase SOD (Oe-EcSOD) were observed in the presence of the parasite. Finally, the open reading frames of both SODs (Oe-SOD Cu/Zn and Oe-EcSOD) were completely sequenced. These findings provide new insights into the cellular and molecular bases of the host–parasite interactions between the flat oyster, O. edulis, and the parasite, B. ostreae.
Sarah C Culloty - One of the best experts on this subject based on the ideXlab platform.
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a naive population of european oyster ostrea edulis with reduced susceptibility to the pathogen Bonamia ostreae are s strategy life traits providing protection
Integrative and Comparative Biology, 2020Co-Authors: Sian Egerton, Sharon A Lynch, Maria Pradoalvarez, Grace Flannery, Tristan Hughjones, David Hughjones, Elaine Brennan, Sarah C CullotyAbstract:European populations of the native flat oyster, Ostrea edulis, have been heavily depleted by two protozoan parasites, Marteila refringens and Bonamia ostreae, with mortalities of up to 90% reported in naive populations. However, in studies carried out over a ten-year period, researching the parasite-host relationship of B. ostreae and O. edulis in several age cohorts within a naive O. edulis population from Loch Ryan (LR), Scotland, 1,364 specimens were challenged and only 64 (5%), across multiple testing protocols, screened positive for B. ostreae. This article presents a case for the development of S-strategy life traits in the LR population that coincide with enhanced immune function and survival. Oysters are considered typical r-strategists (small in size with fast development and high fecundity) while S-strategists, as outlined in Grime's (1977) C-S-R (competitor-stress tolerant-ruderal) triangle theory, are characterized by slow growth and investment in the durability of individuals. This study hypothesises that slower growth and reduced reproductive output in LR oysters has resulted in the investment of an enhanced immune function and reduced susceptibility to B. ostreae i.e. r-strategists with S-strategy life traits equates to protection from significant pathogens. The findings presented here within provide a strong case study for local adaptation of energy allocation and provides empirical support for the C-S-R triangle theory in a marine organism.
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investigating the significance of the role of ostrea edulis larvae in the transmission and transfer of Bonamia ostreae
Journal of Invertebrate Pathology, 2016Co-Authors: Grace Flannery, Sharon A Lynch, Sarah C CullotyAbstract:In this study, the ability of oyster larvae, brooded in the pallial cavity of the parent oyster, to become infected in the pallial fluid, which is influenced by the brooding oyster and surrounding environment, was investigated. Larvae were collected over three summers from three areas around Ireland. Samples were screened for the presence of Bonamia ostreae DNA using PCR analysis. Four samples of larvae were found to be positive for B. ostreae DNA, though the parent oysters were negative for infection. Larvae may be able to acquire the pathogen from the water column during filter feeding or elimination of pseudo-faeces by the brooding adult.
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oral immunostimulation of the oyster ostrea edulis impacts on the parasite Bonamia ostreae
Fish & Shellfish Immunology, 2015Co-Authors: M Pradoalvarez, Sharon A Lynch, A Kane, Grainne Darmody, Belen G Pardo, Paulino Martinez, J Cotterill, T Wontnersmith, Sarah C CullotyAbstract:Abstract Bioactive compounds were orally administered to the native European oyster Ostrea edulis to evaluate the immune response and the progression of infection of the protozoan parasite Bonamia ostreae . The immunostimulants lipopolysaccharide and zymosan directly administrated to the water column induced an increase in lysozyme activity and the percentage of granulocytes in naive oysters over a period of 7 days. In another set of experiments, zymosan and curdlan were microencapsulated in alginate and also administered to the water column to naive and B. ostreae infected O. edulis . Oyster mortality, prevalence and intensity of infection and several immune parameters were evaluated up to 28 days post-administration. Lysozyme activity, nitric oxide production and the expression of galectin, lysozyme and superoxide dismutase increased after 24 h in both infected and uninfected oysters. Zymosan immunostimulated oysters displayed a decrease in the prevalence of B. ostreae infection not attributed to mortalities but which could be associated to the enhanced ability of immunostimulants to evoke an enhanced immune response in the oysters and reduce infection.
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assessment of the impact of a pathogen Bonamia ostreae on ostrea edulis oyster stocks with different histories of exposure to the parasite in ireland
Aquaculture, 2014Co-Authors: Grace Flannery, Sharon A Lynch, T F Cross, Jens Carlsson, Sarah C CullotyAbstract:Abstract The protozoan parasite Bonamia ostreae has decimated Ostrea edulis stocks throughout Europe over the past four decades. A study of two stocks of O. edulis in Ireland with varying periods of exposure to B. ostreae , 5 years and 22 years, was undertaken. The objective of the study was to determine if varying lengths of exposure would translate into observations of differing susceptibilities to B. ostreae . A number of oyster beds within each area were screened. The study was carried out over 13 months to investigate seasonality and the role of environmental parameters, population density and size on disease development. Of particular interest was the fact that prevalence of infection in both stocks was very similar. The stock that had been exposed for 22 years had a similar prevalence, intensity and seasonality of infection as the stock infected for 5 years. B. ostreae was detected in both stocks throughout the year with the highest prevalence in spring, possibly related to the increase in water temperature and/or oysters directing their energy towards gametogenesis. The study indicated that oyster stocks can maintain themselves over extended periods of time in B. ostreae endemic areas. However, prevalence of B. ostreae will remain relatively stable within the stock without some intervention to improve resistance levels e.g. by breeding for resistance over a number of years. Some natural resistance to infection will build up in individual oysters but in natural populations this will continually be diluted by cross fertilisation with more susceptible oysters.
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thirty year history of irish rossmore ostrea edulis selectively bred for disease resistance to Bonamia ostreae
Diseases of Aquatic Organisms, 2014Co-Authors: Sharon A Lynch, Grace Flannery, Tristan Hughjones, David Hughjones, Sarah C CullotyAbstract:The protistan pathogen Bonamia ostreae was first detected in Ostrea edulis at Ross- more, Cork Harbour, on the south coast of Ireland in 1987. A selective breeding programme com- menced in 1988 by Atlantic Shellfish Ltd. to produce B. ostreae-resistant oysters using 3 to 4 yr old survivors as broodstock for controlled spawning in land-based spatting ponds. On-growing of oyster spat settled on mussel cultch was carried out on designated beds within Cork Harbour. Oyster pro- duction subsequently increased successfully, resulting in 3 yr old Rossmore O. edulis being mar- keted from 1993 onwards and a record tonnage of 4 yr old oysters being produced in 1995 and 1996. O. edulis production, B. ostreae prevalence and oyster mortalities have been monitored and recorded at Rossmore for over 30 yr. The collation and analysis of this data from 52 samples and 3190 oysters demonstrate the introduction and progression of bonamiosis and subsequent interventions to ame- liorate disease effects during this period at Rossmore. Results suggest that O. edulis mortalities are now negligible during the first 4 yr of growth, prevalence of B. ostreae infection is low, and no corre- lation exists between prevalence of infection and oyster mortalities. This study, when compared to other studies of bonamiosis-infected oyster populations, suggests that an intervention in the form of a selective breeding programme is required to reduce the impact of the disease.
Bruno Chollet - One of the best experts on this subject based on the ideXlab platform.
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is pallial mucus involved in ostrea edulis defenses against the parasite Bonamia ostreae
Journal of Invertebrate Pathology, 2020Co-Authors: Bruno Chollet, Maria Pradoalvarez, Ophelie Gervais, Sergio Fernandezboo, Stephane Claverol, Cyrielle Lecadet, Christine Dubreuil, Isabelle ArzulAbstract:Abstract Bonamia ostreae is an intrahemocytic parasite that has been responsible for severe mortalities in the flat oyster Ostrea edulis since the 1970s. The Pacific oyster Crassostrea gigas is considered to be resistant to the disease and appears to have mechanisms to avoid infection. Most studies carried out on the invertebrate immune system focus on the role of hemolymph, although mucus, which covers the body surface of molluscs, could also act as a barrier against pathogens. In this study, the in vitro effect of mucus from the oyster species Ostrea edulis and C. gigas on B. ostreae was investigated using flow cytometry. Results showed an increase in esterase activities and mortality rate of parasites exposed to mucus from both oyster species. In order to better understand the potential role of mucus in the defense of the oyster against parasites such as B. ostreae, liquid chromatography and tandem mass spectrometry were used to describe and compare mucus protein composition from both species. In all oyster species, pallial mucus contains a high level of proteins; however, O. edulis mucus produced a variety of proteins that could be involved in the immune response against the parasite, including Cu/Zn extracellular superoxide dismutase, thioxiredoxin, peroxiredon VI, heat shock protein 90 as well as several hydrolases. Conversely, a different set of antioxidant proteins, hydrolases and stress related proteins were identified in mucus from C. gigas. Our results suggest an innate immunity adaptation of oysters to develop a specific response against their respective pathogens. The mucosal protein composition also provides new insights for further investigations into the immune response in oysters.
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involvement of apoptosis in the dialogue between the parasite Bonamia ostreae and the flat oyster ostrea edulis
Fish & Shellfish Immunology, 2019Co-Authors: Ophelie Gervais, Bruno Chollet, Chunyan Feng, Cyrielle Lecadet, Christine Dubreuil, Serena Durante, Cyril Henard, Delphine Serpin, Renault Tristan, Isabelle ArzulAbstract:The protozoan parasite Bonamia ostreae has been associated with the decline of flat oyster Ostrea edulis populations in some European countries. Control of shellfish diseases mostly relies on prevention measures including transfer restrictions and stock management measures such as breeding programmes. These prevention and mitigation measures require a better understanding of interactions between host and pathogens. Previous in vitro studies allowed identifying apoptosis as a mechanism activated by the flat oyster in response to B. ostreae. However, these experiments also suggested that the parasite is able to regulate apoptosis in order to survive and multiply within hemocytes. By simplifying the conditions of infection, in vitro studies allow identifying most distinct features of the response of the host. In order to appreciate the relative importance of apoptosis in this response at the oyster scale, in vivo trials were carried out by injecting with parasites oysters from two French locations, Quiberon Bay (Brittany) and Diana Lagoon (Corsica). Apoptosis was investigated on pools of hemolymph from oysters collected at early and later times after injection using previously developed tools. Apoptotic cellular activities including intracytoplasmic calcium concentration, mitochondrial membrane potential and phosphatidyl serine externalization were analysed using flow cytometry. Moreover, the expression of flat oyster genes involved in both extrinsic and intrinsic pathways was measured using real time quantitative PCR.
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contribution of in vivo experimental challenges to understanding flat oyster ostrea edulis resistance to Bonamia ostreae
Frontiers in Cellular and Infection Microbiology, 2017Co-Authors: Benjamin Morga, Tristan Renault, Nicole Faury, Sophie Lerond, Celine Garcia, Jean-pierre Joly, Estelle Harrang, Sylvie Lapegue, Bruno Chollet, Isabelle ArzulAbstract:Bonamiosis due to the parasite Bonamia ostreae has been associated with massive mortality outbreaks in flat oyster stocks in Europe. As eradication and treatment are not possible, the control of the disease mainly relies on transfer restriction. Moreover, selection has been applied to produce resistant flat oyster families, which present better survival and lower prevalence than non-selected oysters. In order to better understand mechanisms involved in resistance to bonamiosis, cellular and molecular responses of 2 oyster groups (selected oysters and wild-type oysters) were analysed in the context of experimental injection and cohabitation infections. Cellular responses including non-specific esterases detection, ROS production and phagocytosis activity were analysed by flow cytometry. Four genes homologous to genes shown to be involved in immunity were selected (Inhibitor of apotosis OeIAP, Fas ligand OeFas-ligand, Oe-SOD and OeEc-SOD) and monitored by quantitative reverse-transcription PCR (qRT-PCR). Infected oysters showed higher phagocytosis activity than controls, phagocytosis allow parasite degradation, but it also contribute to spreading of B. ostreae infection. Infected selected oyster show a lower phagocytosis activity might be a solution against the parasite infection. The expression of the OeIAP gene and OeFas-ligand gene was significantly increased in selected oysters at 5 days post injection. OeIAP gene expression appeared significantly increased in wild-type oysters at 8 days post injection. Our results suggest that resistance to bonamiosis partly relies on the ability of the oysters to modulate apoptosis.
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flat oyster follows the apoptosis pathway to defend against the protozoan parasite Bonamia ostreae
Fish & Shellfish Immunology, 2016Co-Authors: Ophelie Gervais, Tristan Renault, Bruno Chollet, Isabelle ArzulAbstract:The in vitro model Ostrea edulis hemocyte - Bonamia ostreae is interesting to investigate host-parasite interactions at the cellular level. Indeed, this unicellular parasite infects the flat oyster Ostrea edulis and multiplies within hemocytes, the central effectors of oyster defenses. Apoptosis is a mechanism used by many organisms to eliminate infected cells. In order to study the potential involvement of this mechanism in the oyster response to B. ostreae, in vitro experiments were carried out by exposing hemocytes from the naturally susceptible oyster O. edulis and a resistant oyster species Crassostrea gigas to live and heat-inactivated parasites. Hemocyte apoptotic response was measured using a combination of flow cytometry and microscopy analyses. Whatever the host species was, the parasite was engulfed in hemocytes and induced an increase of apoptotic parameters including intracytoplasmic calcium concentration, mitochondrial membrane potential or phosphatidyl-serine externalization as well as ultrastructural modifications. However, the parasite appears more able to infect flat oyster than cupped oyster hemocytes and the apoptotic response was more important against live than dead parasites in the natural host than in C. gigas. Our results suggest that O. edulis specifically responds to B. ostreae by inducing apoptosis of hemocytes.
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heat shock protein 90 of Bonamia ostreae characterization and possible correlation with infection of the flat oyster ostrea edulis
Journal of Eukaryotic Microbiology, 2013Co-Authors: Maria Pradoalvarez, Benjamin Morga, Bruno Chollet, Yann Couraleau, Isabelle ArzulAbstract:In this study, we described the cytosolic HSP90 of Bonamia ostreae, an intracellular parasite of Ostrea edulis hemocytes. The complete open reading frame was assembled by Rapid Amplification cDNA Ends reactions on cDNA of B. ostreae-infected hemocytes. HSP90 amplification was corroborated in infected oysters and B. ostreae purified cells. The functionality of the HSP90, studied by inhibitory assays with radicicol, suggests that this protein may play a role in hemocyte invasion. Our results inform the molecular basis that governs B. ostreae-O. edulis interactions.