Effects of extracellular products from the pathogenic Vibrio aestuarianus strain 01/32 on lethality and cellular immune responses of the oyster Crassostrea gigas.
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.
Labreuche
Yannick
Y
Unité Mixte de Recherche Physiologie et Ecophysiologie des Mollusques Marins, IFREMER, Centre de Brest, B.P. 70, 29280 Plouzané, France.
Soudant
Philippe
P
Gonçalves
Madeleine
M
Lambert
Christophe
C
Nicolas
Jean-Louis
JL
D000818:Animals; D002448:Cell Adhesion; D006434:Hemocytes / Q000166:cytology / Q000187:drug effects / Q000276:immunology / Q000382:microbiology; D006458:Hemolymph / Q000187:drug effects; D007928:Lethal Dose 50; D010125:Ostreidae / Q000276:immunology* / Q000382:microbiology*; D010587:Phagocytosis / Q000187:drug effects; D017382:Reactive Oxygen Species / Q000378:metabolism; D014733:Vibrio / Q000145:classification / Q000276:immunology / Q000378:metabolism* / Q000472:pathogenicity*; D014774:Virulence
D017382:Reactive Oxygen Species