Immune Response of Red Sea Bream to Edwardsiella tarda Antigens

Abstract

Red sea bream, Pagrus major, were injected intramuscularly once with Edwardsiella tarda crude lipopolysaccharide (LPS) and formalin killed cells (FKC) preparations. The immune response of red sea bream was studied 1, 2, 3 and 4 weeks after the immunization. The protein, albumin and glucose of the serum, agglutination antibody titer, passive hemagglutination titer, complement-like factor activity, bacteriolytic activity, hemagglutination activity of the serum and the skin mucus and the in vitro phagocytic index of the total blood of the immunized fish were determined.
The results of the protein, albumin and glucose analysis of the immunized red sea bream serum did not show differences to the unimmunized fish. The agglutination and passive hemagglutination titers of the skin mucus did not show increase; however, the agglutination and passive hemagglutination titers of the serum showed increase from the first week after immunization, particularly in the FKC immunized fish. The activity of the serum complement-like factor showed apparently no increase of the immunized group, when compared to the unimmunized fish. The bacteriolytic activity of serum and skin mucus did not show differences between the immunized and unimmunized fish. The hemagglutination activity increases in both LPS and FKC immunized groups after two weeks from the immunization. The results of the in vitro phagocytic index of the total blood showed enhance from the first week after immunization in both LPS and FKC immunized groups, more than the unimmunized fish. The results suggest that the phagocytosis could be one important mechanism of red sea bream defence to E. tarda infection.