| Abstrakt: |
Streptococcus iniae and Aeromonas hydrophila are the two major pathogens of tilapia, and considered a significant problem with huge economic losses in global aquaculture. Infections by these pathogens can be prevented via vaccination. This study measures the expression of immune genes and the subsequent systemic and mucosal immune responses following administration of a feed-based bivalent vaccine against streptococcosis and motile aeromonad septicemia (MAS) in red hybrid tilapia. A total of 1176 healthy red hybrid tilapias were dispersed into four experimental groups with triplicates. Group BI was vaccinated with a bivalent vaccine containing killed S. iniae and A. hydrophila that were mixed into feed. Group MS was similarly vaccinated with a monovalent vaccine containing killed S. iniae, group MA was vaccinated with a monovalent vaccine containing killed A. hydrophila, while group control was fed the normal feed that contained no vaccine. The vaccines were delivered orally at 5% of bodyweight for 5 consecutive days, and the double booster doses were administered in same manner on 14 and 42 days post-vaccination (dpv). Quantitative real-time PCR revealed significant (P < 0.05) upregulation of IL-1β, C-type lysozyme, TNF-α, TGF-β, CD4, MHC-I, MHC-II, and IgT in the spleen, head kidney, and hindgut of the BI and MS groups. The highest expressions of IL-1β, TNF-α, and IgT were observed in the spleen (3.91-fold), head kidney (3.61-fold), and hindgut (8.85-fold) of the BI fish. Lysozyme activity increased significantly (P < 0.05) on days 21, 35, 63, and 105 in BI group, while phagocytic activity was significantly (P < 0.05) higher on days 7, 63, and 77 in BI group than other vaccinated groups. The current experiment showed the upregulation of immune genes in systemic and mucosal tissues of immunized fish with subsequent higher immune activities. Thus, the feed-based bivalent vaccine was able to stimulate the innate and adaptive immune responses against streptococcosis and MAS. [ABSTRACT FROM AUTHOR] |
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