THE NONSPECIFIC IMMUNOSTIMULATION AND ADJUVANT EFFECTS OF VIBRIO-ANGUILLARUM BACTERIN, M-GLUCAN, CHITIN AND FREUNDS COMPLETE ADJUVANT AGAINST PASTEURELLA-PISCICIDA INFECTION IN YELLOWTAIL

The non-specific immunostimulation and adjuvant effects of Vibrio angu illarum bacterin (VAB), M-glucan, chitin and Freund's complete adjuvan t (FCA) against pasteurellosis were examined in yellowtail, Seriola qu inqueradiata. Control fish were injected intraperitoneally with 0.1 mi of sterile phosphate buffered saline (PBS). Experimental fish were in jected similarly with either vaccine (lipopolysaccharide-mixed chlorof orm-killed Pasteurella piscicida, LPS-CKC), an immunostimulant or mixt ure of the vaccine and an immunostimulant. All fish were subsequently challenged by the same but live P. piscicida strain using an immersion method at 15, 25, 35 and 45 days post-inoculation. Immunostimulants a lone were found ro slightly increase the protection against Pasteurell a infection, but the effects were not statistically significant. The m ost effective adjuvant was FCA, however the enhanced protection was no t statistically different from that of fish inoculated with LPS-CKC al one. However, the relative percent survival (RPS) of fish vaccinated w ith M-glucan, chitin or Vibrio bacterin as adjuvant was lower than tha t of fish vaccinated with only LPS-CKC bacterin alone. Thus, M-glucan, chitin and Vibrio bacterin had no positive adjuvant effects on the P. piscicida vaccine.