Effects of immunopotentiators on biochemical parameters, proinflammatory cytokine, and nonspecific immune responses in Shaoxing ducklings

Antibiotics are one of the most important medical discoveries of the 20th century and will remain an essential tool for treating animal and human diseases in the 21st century. However, misuse of antibiotics imperils the development of animal husbandry and human health all over the world, and it is important to find reliable alternatives to antibiotics to reduce the use of antibiotics. In this study, 22 potential immunopotentiators were screened on the levels of apoptosis and inflammatory factor in duck embryo fibroblast cells (DEFs). The results indicated that interferon (IFN)-β and tumor necrosis factor-α gene transcriptions were significantly upregulated, while interleukin (IL)-2 and Bcl2 mRNA levels were significantly decreased during 22 immunopotentiators treatment. Besides, the expression level of IL-1β mRNA showed significant increase during dihydromyricetin, chlorogenic acid, naringin, imiquimod, thymopentin, β-D-Glucan, astragalus polysacharin, astragalus saponin I, astragalus flavone, curcumin, CpG-DNA-2, and LPS treatment. And the level of caspase 3 protein was significantly upregulated with treating chlorogenic acid, β-D-Glucan, astragalus polysacharin, astragalus flavone, curcumin, CpG-DNA-2, chicken IgG, LPS, and poly(I:C). These results indicated that chlorogenic acid, β-D-Glucan, astragalus flavone, CpG-DNA-2, and chicken IgG have the positive immune regulation effects on duck DEFs. Thus, the 5 immunopotentiators were chosen to further verify their immunomodulatory function in vivo. The results showed that the activity of serum AST was significantly downregulated during all immunopotentiators treatments excepting for β-D-Glucan, and the activities of serum IL12p40, IL-1β, IFN-α, and IFN-β were significantly increased compared with the control group. Five immunopotentiators also induced the duck's pattern recognition receptors and inflammatory factor gene expression. In addition, 5 immunopotentiators could facilitate the contents of serum caspase 3, iNOSm and COX2 and reduce the Bcl2. These results suggested that these 5 immunopotentiators could enhance duck innate immune responses. Taken together, our study not only screened out 5 kinds of duck innate immune immunopotentiators but also initially clarified their underlying mechanism of action, which provide a new insight for the development of efficient approaches to prevent the duck disease from pathogen infections.