ADJUVANT ACTIVITIES OF A VIBRIO-SALMONICIDA BACTERIN ON T-DEPENDENT AND T-INDEPENDENT ANTIGENS IN RAINBOW-TROUT (ONCORHYNCHUS-MYKISS)

Groups of rainbow trout received two injections of the T-dependent ant igen Limulus polyphemus haemocyanin (LPH) or the T-independent antigen Escherichia coli lipopolysaccharide O 111:B4 (E.coli LPS), mixed with either Freund's complete adjuvant (FCA), or a Vibrio salmonicida bact erin or phosphate buffered saline (PBS). One group that received an in jection of PBS served as a negative control for both antigens. The ant ibody responses against E. coli LPS and LPH were measured by enzyme li nked immunosorbent assays 6, 10 and 14 weeks after the second immunisa tion. The groups injected with E. coli LPS or LPH in FCA responded wit h high antibody titers. The groups that received E. coli LPS or LPH mi xed with V. salmonicida or PBS, responded with relatively low antibody titers to the antigens. However, the fish injected with LPH and V. sa lmonicida bacterin responded significantly better to LPH six weeks pos t immunisation than the fish that received LPH and PBS. Ten and 14 wee ks p.i. there were no significant differences between these groups. Th ere was no difference in the response to E. coli LPS between the fish that received E. coli LPS mixed with V. salmonicida bacterin and those injected with LPS in PBS neither 6, 10 nor 14 weeks p.i. The results of the present study show that a V. salmonicida bacterin enhances the antibody response to a T-dependent antigen in rainbow trout. (C) 1998 Academic Press Limited.