ADJUVANT ACTIVITY OF POLAR GLYCOPEPTIDOLIPIDS FROM MYCOBACTERIUM-CHELONAE IN EXPERIMENTAL VACCINES AGAINST AEROMONAS-SALMONICIDA IN SALMONID FISH

In order to evaluate the adjuvant activity in fish of polar glycopepti dolipids from Mycobacterium chelonae (pGPL-Mc), salmonids were injecte d with pGPL-Mc alone or in combination with Aeromonas salmonicida bact erin. Side-effects, antibody production against A. salmonicida and lym phocyte stimulation were studied. Twelve weeks after vaccination, the antibody responses of fish injected with 0.25 mg kg(-1) pGPL-Mc in add ition to bacterial antigen were significantly stronger than those in f ish injected with a non-adjuvanted bacterin, and insignificantly lower than the antibody titles achieved with an oil-adjuvanted reference va ccine. Higher doses of pGPL-Mc reduced the levels of specific antibodi es. The lymphocyte responses to lipopolysaccharide (LPS), a potent B-c ell mitogen, were higher in rainbow trout injected with pGPL-Mc alone, compared to the fish injected with saline, suggesting B-cell activati on as a mechanism. pCPL-Mc showed a weak dose-dependent mitogen effect on fish leucocytes. No significant side-effects were observed after i ntraperitoneal injection of pGPL-Mc. The relatively long-term immunost imulation in fish with no side-effects makes pGPL-Mc an interesting ca ndidate adjuvant for incorporation in future vaccine formulations. (C) 1997 Academic Press Limited.