Effect of Montanide™ IMS 1312 VG adjuvant on efficacy of Yersinia ruckeri vaccine in rainbow trout (Oncorhynchus mykiss)

The efficacy of immersion vaccination Yersinia ruckeri bacterin containing Montanide (TM) IMS 1312 VG was evaluated in 100-120 g rainbow trout against yersiniosis. Healthy fish were vaccinated by immersion vaccination with inactivated whole cells (1 x 10(8) cells/ml) of a virulent strain of Y. ruckeri biotype I with and without Montanide (1:1; Montanide/antigen) for 2 min at 12-14 degrees C. Control group was immersed in sterile PBS. Leukocyte counts, serum lysozyme assay, alternative hemolytic complement (ACH(50)) assay, antibody titration and relative percent survival (RPS) were measured on 2-10 weeks post-immunization. No significant difference was seen in leucocyte population of trout immunized either with Y. ruckeri antigen or Y. ruckeri antigen containing Montanide (P > 0.05), while leucocyte and heterophil populations in control group were significantly lower and higher, respectively, than both immunized groups (P < 0.05). In addition, there was no significant difference in lymphocyte population of trout immunized either with Y. ruckeri antigen or Y ruckeri antigen containing Montanide (P > 0.05), while lymphocyte population in control group was significantly lower than both immunized groups (P < 0.05). Lysozyme activity in immunized fish with Y. ruckeri containing Montanide was higher than the immunized fish with Y. ruckeri antigen alone during 8 weeks post-immunization ((P < 0.05). Also, level of lysozyme in control fish was generally lower than both immunized groups (P < 0.05). The level of ACH(50) between both immunized groups was insignificant (P > 0.05) but these were significantly higher than control group through the experiment (P < 0.05). The lowest anti-Y.ruckeri antibody titers in both immersion vaccination groups were significantly higher through 2-8 weeks post-vaccination compared to the control group (P < 0.05). In the group immersion vaccinated with Y ruckeri bacterin plus Montanide the titers 2-8 weeks post-vaccination were significantly higher the titer in the immersion vaccinated with Y. ruckeri bacterin (P < 0.05). Fish vaccinated with antigen without Montanide resulted in RPS of 80-82% on 2-10 weeks post-vaccination, while those for antigen containing montanide gave RPSs of 93.8-100% 2-10 weeks post-immunization (P < 0.05). (C) 2014 Elsevier Ltd. All rights reserved.