Greater efficacy of the ECMS-oil adjuvant over other formulations on immune responses against Bordetella bronchiseptica in rabbits and the underlying mechanism

In this study, the adjuvant effects of the extract of Cochinchina momordica seed ECMS + oil, oil alone, ECMS alone, conventional alum adjuvant on inactivated Bordetella bronchiseptica (Bb) vaccine or control using antigen alone without adjuvant were evaluated along with the underlying mechanism. The results in experiment A demonstrated that antibody levels in Bb whole cell protein in the ECMS800 μg + oil group were significantly higher than in the other adjuvant groups (p < 0.05) on day 21. The agglutination antibody titer was also higher than the other groups (p < 0.05) on day 37. The ECMS800 μg + oil group improved cellular immune responses compared to other adjuvant groups, including control using antigen alone without adjuvant and the PBS group (p < 0.05). After Bb challenge, the ECMS800 μg + oil group showed the highest protection rate, which was significantly higher than ECMS alone or control using antigen alone without adjuvant and the PBS group (p < 0.05 and p < 0.01). IgA cells in the ECMS800 μg + oil group differed significantly from the IgA cells of other groups in the lungs (p < 0.01). The results of cell recruitment showed that the number of lymphocytes in the ECMS400 μg + oil were higher than the number of cells for other groups except the ECMS(100 μg/800 μg) + oil groups (p < 0.05). Intermediate cells in the ECMS(100 μg/400 μg) + oil groups were higher than the number of cells for other groups, including the control using antigen alone group (p < 0.05). Neutrophils in the ECMS(100 μg/400 μg/800 μg) + oil groups were significantly higher than the ECMS 800 μg and control using antigen alone groups (p < 0.05). White blood cells in the ECMS100 μg + oil group were significantly higher than the oil, ECMS800 μg and control using antigen alone groups (p < 0.05). IL-2 expression in the ECMS800 μg + oil group was significantly higher than other groups, except for the ECMS400 μg + oil group (p < 0.05). IL-4 expression in the ECMS800 μg + oil group was significantly higher than other groups (p < 0.05). GATA3 in the ECMS800 μg + oil groups was significantly higher than the oil, ECMS800 μg and control using antigen alone group (p < 0.05). ECMS-oil adjuvant mixture could most effectively protect B. bronchiseptica immunized rabbits and, therefore, could be an alternative way of improving B. bronchiseptica vaccination in rabbits.