Immune Response of Eel to Edwardsiella tarda Lipid

To confirm the properties of the lipid from Edwardsiella tarda as immunosuppressor in the eel, suggested by previous studies, lipid extracted from the whole cell (Lipid), crude lipopolysaccharide (LPS), formalin killed cell (FKC) and whole cell without lipid (CWL) were injected intramuscularly in the eels. To compare the protective effect of the preparations, the eels were challenged with live E. tarda, strain EF-1. The eels immunized with the Lipid preparation did not show differences in protection against challenge in comparison with the control group, and the highest survival rate was recorded in eels immunized with the crude LPS preparation. The antibody titer of the Lipid immunization group was very low and the highest was in the crude LPS immunization group. In vitro phagocytic activity of the total blood was significantly lower in the Lipid immunization group than that found in the control group, whereas higher activity was shown in the crude LPS immunization group. The phagocytic activity of FKC and CWL immunization groups was not significantly different from that of the control group. The results confirm immunogenic properties of E. tarda lipid as immunosuppressor, which decreases the level of phagocytosis in the eel.