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Jeanlouis Nicolas - One of the best experts on this subject based on the ideXlab platform.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD50 value of 3.3 mg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions. q 2005 Elsevier Ltd. All rights reserved.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD(50) value of 3.3 microg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions.
Christophe Lambert - One of the best experts on this subject based on the ideXlab platform.
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Toxic dinoXagellates (Alexandrium fundyense and A. catenella) have minimal apparent eVects on oyster Hemocytes
2020Co-Authors: Hélène Hégaret, Gary H Wikfors, Jean-baptiste Bérard, Sandra E. Shumway, Philippe Soudant, Christophe Lambert, Patrick LassusAbstract:Abstract The possible eVect of Alexandrium spp. containing paralytic shellWsh poisoning (PSP) toxins on the Hemocytes of oysters was tested experimentally. In one trial, eastern oysters, Crassostrea virginica Gmelin, were exposed to bloom concentrations of the sympatric dinoXagellate, Alexandrium fundyense Balech, alone and in a mixture with a non-toxic diatom, Thalassiosira weissXogii (Grun) Fryxell et Hasle. Subsequently, another experiment exposed PaciWc oysters, Crassostrea gigas Thunberg, to a mixed suspension of the sympatric, toxic species Alexandrium catenella (Whedon et Kofoid) Balech, with T. weissXogii. Measurements of numbers of oyster Hemocytes, percentages of diVerent cell types, and functions (phagocytosis, reactive oxygen species (ROS) production, and mortality) were made using Xow-cytometry. During and after exposure, almost no signiWcant eVects of Alexandrium spp. upon hemocyte numbers, morphology, or functions were detected, despite observations of adductor-muscle paralysis in C. virginica and measured toxin accumulation in C. gigas. The only signiWcant correlation found was between toxin accumulation at one temperature and higher numbers of circulating live and dead Hemocytes in C. gigas. The PSP toxins are known to interfere speciWcally with sodiumchannel function; therefore, the Wnding that the toxins had no eVect on measured hemocyte functions suggests that sodium-channel physiology is not important in these hemocyte functions. Finally, because oysters were exposed to the living algae, not puriWed toxins, there was no evidence of bioactive compounds other than PSP toxins aVecting Hemocytes in the two species of Alexandrium studied
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hemocyte characteristics in families of oysters crassostrea gigas selected for differential survival during summer and reared in three sites
Aquaculture, 2007Co-Authors: Jeanne Moal, Frederic Jean, Lionel Dégremont, Pierre Boudry, Maryse Delaporte, Philippe Soudant, Christophe LambertAbstract:High variability among individuals is often encountered when hemocyte characteristics are measured in bivalves. Such variability is suspected to result partly from genetic factors. In this study, hemocyte characteristics of six families of Crassostrea gigas were compared by flow cytometry at one sampling date in October 2001. These families were obtained from a nested, halfsibling cross design, and reared from July to October 2001 at three sites distributed along the French Atlantic coast from north to south: Baie des Veys (Normandy), Riviere d'Auray (Brittany) and Ronce (Marennes-oleron Basin, Poitou Charentes). Among the 15 measured hemocyte characteristics, production of reactive oxygen species (ROS) of untreated Hemocytes (maintained in filtered sterile seawater) and treated Hemocytes (zymosan at 20 particles per hemocyte, and with Vibrio sp. S322 at 50 bacteria per hemocyte) was the most notable differences between families. This supports the existence of a genetic basis, at least partly, for the hemocyte characteristics of oysters, and especially for ROS production. Among the six families analyzed, three have shown high survival during summer (named as "resistant", mean mortality 5.2%) and three experienced high mortality during summer (named as "susceptible", 30.6% mean mortality). Families showing high or low survival to summer mortality had similar hemocyte characteristics, regardless of the environmental conditions or reproductive state. Resistant families were observed to have higher total hemocyte counts and lower production of ROS than susceptible families. Moreover, ROS production of Hemocytes from susceptible families was diminished significantly more by pathogenic Vibrio than that of resistant families. However, this study demonstrates also that rearing site strongly affected the hemocyte characteristics of all families of oysters, most notably hemocyte concentration and morphology (size and granularity), production of reactive oxygen species (ROS), and susceptibility to the cytotoxic activity of the pathogenic Vibrio sp. S322 (50 bacteria/ hemocyte). Food availability and reproductive state are the most probable explanations for the site differences observed. Finally, it appeared difficult to link oyster survival during summer mortality to hemocyte profiles evaluated at one sampling date; other relevant indicators would probably help explaining oyster survival during summer mortality events.
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toxic dinoflagellates alexandrium fundyense and a catenella have minimal apparent effects on oyster Hemocytes
Marine Biology, 2007Co-Authors: Hélène Hégaret, Gary H Wikfors, Jean-baptiste Bérard, Sandra E. Shumway, Philippe Soudant, Christophe Lambert, Patrick LassusAbstract:The possible effect of Alexandrium spp. containing paralytic shellfish poisoning (PSP) toxins on the Hemocytes of oysters was tested experimentally. In one trial, eastern oysters, Crassostrea virginica Gmelin, were exposed to bloom concentrations of the sympatric dinoflagellate, Alexandrium fundyense Balech, alone and in a mixture with a non-toxic diatom, Thalassiosira weissflogii (Grun) Fryxell et Hasle. Subsequently, another experiment exposed Pacific oysters, Crassostrea gigas Thunberg, to a mixed suspension of the sympatric, toxic species Alexandrium catenella (Whedon et Kofoid) Balech, with T. weissflogii. Measurements of numbers of oyster Hemocytes, percentages of different cell types, and functions (phagocytosis, reactive oxygen species (ROS) production, and mortality) were made using flow-cytometry. During and after exposure, almost no significant effects of Alexandrium spp. upon hemocyte numbers, morphology, or functions were detected, despite observations of adductor-muscle paralysis in C. virginica and measured toxin accumulation in C. gigas. The only significant correlation found was between toxin accumulation at one temperature and higher numbers of circulating live and dead Hemocytes in C. gigas. The PSP toxins are known to interfere specifically with sodium-channel function; therefore, the finding that the toxins had no effect on measured hemocyte functions suggests that sodium-channel physiology is not important in these hemocyte functions. Finally, because oysters were exposed to the living algae, not purified toxins, there was no evidence of bioactive compounds other than PSP toxins affecting Hemocytes in the two species of Alexandrium studied.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD50 value of 3.3 mg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions. q 2005 Elsevier Ltd. All rights reserved.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD(50) value of 3.3 microg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions.
Philippe Soudant - One of the best experts on this subject based on the ideXlab platform.
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Toxic dinoXagellates (Alexandrium fundyense and A. catenella) have minimal apparent eVects on oyster Hemocytes
2020Co-Authors: Hélène Hégaret, Gary H Wikfors, Jean-baptiste Bérard, Sandra E. Shumway, Philippe Soudant, Christophe Lambert, Patrick LassusAbstract:Abstract The possible eVect of Alexandrium spp. containing paralytic shellWsh poisoning (PSP) toxins on the Hemocytes of oysters was tested experimentally. In one trial, eastern oysters, Crassostrea virginica Gmelin, were exposed to bloom concentrations of the sympatric dinoXagellate, Alexandrium fundyense Balech, alone and in a mixture with a non-toxic diatom, Thalassiosira weissXogii (Grun) Fryxell et Hasle. Subsequently, another experiment exposed PaciWc oysters, Crassostrea gigas Thunberg, to a mixed suspension of the sympatric, toxic species Alexandrium catenella (Whedon et Kofoid) Balech, with T. weissXogii. Measurements of numbers of oyster Hemocytes, percentages of diVerent cell types, and functions (phagocytosis, reactive oxygen species (ROS) production, and mortality) were made using Xow-cytometry. During and after exposure, almost no signiWcant eVects of Alexandrium spp. upon hemocyte numbers, morphology, or functions were detected, despite observations of adductor-muscle paralysis in C. virginica and measured toxin accumulation in C. gigas. The only signiWcant correlation found was between toxin accumulation at one temperature and higher numbers of circulating live and dead Hemocytes in C. gigas. The PSP toxins are known to interfere speciWcally with sodiumchannel function; therefore, the Wnding that the toxins had no eVect on measured hemocyte functions suggests that sodium-channel physiology is not important in these hemocyte functions. Finally, because oysters were exposed to the living algae, not puriWed toxins, there was no evidence of bioactive compounds other than PSP toxins aVecting Hemocytes in the two species of Alexandrium studied
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hemocyte characteristics in families of oysters crassostrea gigas selected for differential survival during summer and reared in three sites
Aquaculture, 2007Co-Authors: Jeanne Moal, Frederic Jean, Lionel Dégremont, Pierre Boudry, Maryse Delaporte, Philippe Soudant, Christophe LambertAbstract:High variability among individuals is often encountered when hemocyte characteristics are measured in bivalves. Such variability is suspected to result partly from genetic factors. In this study, hemocyte characteristics of six families of Crassostrea gigas were compared by flow cytometry at one sampling date in October 2001. These families were obtained from a nested, halfsibling cross design, and reared from July to October 2001 at three sites distributed along the French Atlantic coast from north to south: Baie des Veys (Normandy), Riviere d'Auray (Brittany) and Ronce (Marennes-oleron Basin, Poitou Charentes). Among the 15 measured hemocyte characteristics, production of reactive oxygen species (ROS) of untreated Hemocytes (maintained in filtered sterile seawater) and treated Hemocytes (zymosan at 20 particles per hemocyte, and with Vibrio sp. S322 at 50 bacteria per hemocyte) was the most notable differences between families. This supports the existence of a genetic basis, at least partly, for the hemocyte characteristics of oysters, and especially for ROS production. Among the six families analyzed, three have shown high survival during summer (named as "resistant", mean mortality 5.2%) and three experienced high mortality during summer (named as "susceptible", 30.6% mean mortality). Families showing high or low survival to summer mortality had similar hemocyte characteristics, regardless of the environmental conditions or reproductive state. Resistant families were observed to have higher total hemocyte counts and lower production of ROS than susceptible families. Moreover, ROS production of Hemocytes from susceptible families was diminished significantly more by pathogenic Vibrio than that of resistant families. However, this study demonstrates also that rearing site strongly affected the hemocyte characteristics of all families of oysters, most notably hemocyte concentration and morphology (size and granularity), production of reactive oxygen species (ROS), and susceptibility to the cytotoxic activity of the pathogenic Vibrio sp. S322 (50 bacteria/ hemocyte). Food availability and reproductive state are the most probable explanations for the site differences observed. Finally, it appeared difficult to link oyster survival during summer mortality to hemocyte profiles evaluated at one sampling date; other relevant indicators would probably help explaining oyster survival during summer mortality events.
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toxic dinoflagellates alexandrium fundyense and a catenella have minimal apparent effects on oyster Hemocytes
Marine Biology, 2007Co-Authors: Hélène Hégaret, Gary H Wikfors, Jean-baptiste Bérard, Sandra E. Shumway, Philippe Soudant, Christophe Lambert, Patrick LassusAbstract:The possible effect of Alexandrium spp. containing paralytic shellfish poisoning (PSP) toxins on the Hemocytes of oysters was tested experimentally. In one trial, eastern oysters, Crassostrea virginica Gmelin, were exposed to bloom concentrations of the sympatric dinoflagellate, Alexandrium fundyense Balech, alone and in a mixture with a non-toxic diatom, Thalassiosira weissflogii (Grun) Fryxell et Hasle. Subsequently, another experiment exposed Pacific oysters, Crassostrea gigas Thunberg, to a mixed suspension of the sympatric, toxic species Alexandrium catenella (Whedon et Kofoid) Balech, with T. weissflogii. Measurements of numbers of oyster Hemocytes, percentages of different cell types, and functions (phagocytosis, reactive oxygen species (ROS) production, and mortality) were made using flow-cytometry. During and after exposure, almost no significant effects of Alexandrium spp. upon hemocyte numbers, morphology, or functions were detected, despite observations of adductor-muscle paralysis in C. virginica and measured toxin accumulation in C. gigas. The only significant correlation found was between toxin accumulation at one temperature and higher numbers of circulating live and dead Hemocytes in C. gigas. The PSP toxins are known to interfere specifically with sodium-channel function; therefore, the finding that the toxins had no effect on measured hemocyte functions suggests that sodium-channel physiology is not important in these hemocyte functions. Finally, because oysters were exposed to the living algae, not purified toxins, there was no evidence of bioactive compounds other than PSP toxins affecting Hemocytes in the two species of Alexandrium studied.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD50 value of 3.3 mg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions. q 2005 Elsevier Ltd. All rights reserved.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD(50) value of 3.3 microg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions.
Yannick Labreuche - One of the best experts on this subject based on the ideXlab platform.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD50 value of 3.3 mg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions. q 2005 Elsevier Ltd. All rights reserved.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD(50) value of 3.3 microg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions.
Madeleine Goncalves - One of the best experts on this subject based on the ideXlab platform.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD50 value of 3.3 mg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions. q 2005 Elsevier Ltd. All rights reserved.
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effects of extracellular products from the pathogenic vibrio aestuarianus strain 01 32 on lethality and cellular immune responses of the oyster crassostrea gigas
Developmental and Comparative Immunology, 2006Co-Authors: Yannick Labreuche, Philippe Soudant, Christophe Lambert, Madeleine Goncalves, Jeanlouis NicolasAbstract:Vibrio aestuarianus strain 01/32 was previously shown to be pathogenic to Crassostrea gigas juveniles. To investigate virulence mechanisms of this pathogen, we studied the toxicity to oysters of its extracellular products (ECPs). ECPs displayed lethality to animals, with a LD(50) value of 3.3 microg/g body weight. To determine the oyster cellular immune responses induced by these ECPs, we further examined in vitro their effects on C. gigas Hemocytes, using flow cytometric-based hemocyte assays. Treatment of hemolymph with ECPs caused a significant inhibition of hemocyte phagocytosis and adhesive capabilities. In contrast, the pathway of reactive oxygen species production was enhanced by higher ECP concentrations. Exposure of Hemocytes to live bacteria induced no changes in hemocyte parameters. Together, these results suggest that V. aestuarianus strain 01/32 secretes one or more factors which may play an important role in the pathogenicity of this microorganism, and which display immunosuppressant activities on hemocyte functions.