Vibrio splendidus is an oyster pathogen associated with the summer mortalities affecting the production of Crassostrea gigas oysters worldwide. The increasing experimental evidence suggests that there are some forms of specific acquired immunity in invertebrates, but the underlying mechanism is not fully understood. In the present study, Pacific oyster (Crassostrea gigas) stimulated primarily by exposure to 105 Vibrio splendidus displayed stronger immune responses levels when they encountered the secondary challenge of 108 V.splendidus.we tested Vibrio primed by exposure to colonized in oysters to investigate their resistance against hemolymph in vivo and in vitro experiments. we investigated the immunological responses in oysters and whether this colonization results in elevated mortality.The selected strains showed higher survival in seconde challenge in oyster model and cross- protection against Vibrio splendidus in vitro. A population of oyster selected for resistance to the Vibrio splendidus showed increased in vivo survival, in addition, V.Splendidus reduction of pathogen shedding. In conclusion, our results suggest that the primary stimulation of V. splendidus led to immune priming in oysters when encountering the secondary challenge with V. splendidus, in addition, the increased survival of oysters almost certainly by stimulating the immune system in hosts led to prevent vibriosis in the oyster.
Keywords: Vibrio splendidus, oyster Crassostrea gigas , Immune priming ,cross-protection