The immune enhancement activity of exopolysacharide from marine bacteria on the IBDV immune response induced by B87 vaccine

Abstract

Abstract Infectious bursal disease (IBD), which is caused by infectious bursal disease virus (IBDV), is a fatal or immunosuppressive disease of young chickens. Immunization is still an important way to prevent the outbreak of the disease. The purpose of this study was aimed to investigate the immune enhancement activity of two kinds of exopolysacharide (EPS), on the IBDV immune response induced by an IBD vaccine (B87). B87 vaccine plus EPS or B87 only were performed twice (at 7 and 14-day old) on commercial Three-Yellow-Chickens. The antibodies and IL-1 level were evaluated after immunization. The vvIBDV challenging was performed at 28-day old. The protection were assessed at 3 and 7 days post infection (dpi). The results showed that IBDV antibodies and IL-1 level in 04 EPS+B87 and 09 EPS+B87 groups were significantly higher than B87 group. Further, the IL-1 level in groups received EPS only were significantly higher than the group received PBS only. High levels of IBDV antibody and IL-1 lasted at least for 5 weeks. After challenged with vvIBDV, the morbidity in 04 EPS+B87 and 09 EPS+B87 groups was 20%, lower than any other. The BBIX of bursa and thymus in 04 EPS+B87 and 09 EPS+B87 groups were significantly higher than the B87 group but lower than negative control, suggested that either the 04 and 09 EPS might have the ability to repair the immune organ damages induced by B87 vaccine. The trend of T cells (both CD4+ and CD8+) and B cells number, and the viral load, at 3 and 7 dpi, respectively, were consistent with the changing trend in BBIX value. We concluded that either 04 or 09 EPS showed the activity of immune enhancement in Three-Yellow-Chickens, the combination of EPS and B87 could induce higher titers of anti-IBDV antibody and protect chickens from vvIBDV challenge.