The impact of Vibrio anguillarum challenging on nonspecific immune responses of sea perch Lateolabrax japonicus

Abstract:

Vibrio anguillarum is a common form of bacterial pathogens for marine fish. In this paper, sea perch (Lateolabrax japonicus) was challenged with an intraperitoneal injection at different concentrations of V. anguillarum: namely treatments A: 1*10⁶ pfu/mL, B:1*10⁷ pfu/mL, C:1*10⁸ pfu/mL and the innate immunity indicators were investigated. Blood samples were taken at different time, and the effects of challenging of V. anguillarum on the immunity responses were studied by measuring the respiratory burst, alkaline phosphatase (ALP), acid phosphatase (ACP), phenoloxidase (PO) and superoxide dismutase (SOD) activities. The results showed that: 1) Compared with the control group, the respiratory burst activity of treatment B and C decreased significantly (P<0.01) at 12h and 36h of injection. 2) Compared with the control group, the PO activity of treatment A, B and C at 12 h, 36 h ,60 h, 84 h and 108 h after injection decreased significantly (P<0.01). 3) There was no significant difference between treatments and control groups for ALP activity except for at 60 h. 4) Compared with the control group, the ACP activity of treatment A, B and C at 60 h, 84 h and 108 h after injection increased significantly (P<0.05). 5) There was no significant difference between treatments and control groups for SOD activity at 12 h, 36 h, 60 h, 84 h and 108 h(P>0.05). Moreover, in the semilethal experiment, V. anguillarum at the concentration of 1*10⁶ pfu/mL,1*10⁷ pfu/mL and 1*10⁸ pfu/mL 50%, of death in experimental group occurred on 12 d,11 d and 8d respectively, while no death for control group. During infection, experimental group has different symptoms: caudal fin ulceration, gill pale, whitish cornea, the mouth's ulceration, the inside has yellow viscous ascites. The higher the concentration infection with V. anguillarum, the earlier was for 50% of the death. These results indicated that V. anguillarum concentration and the mortality rate are positively correlated.