Comparative Immunological Analysis of Innate Immunity Activation after Oral Administration of Wheat Fermented Extract to Teleost Fish

Background: Intradermal or oral administration of lipopolysaccharide derived from Pantoea agglomerans (IP-PA1) has shown prophylactic and antitumor effects without serious side-effects. While it is known that tumor necrosis factor (TNF)-alpha produced by activated macrophages plays an important role in the expression mechanism following intradermal administration, details of the mechanism after oral administration remain unclear. In this study, the activation of innate immunity using fish as an animal model was investigated. In fish, the innate immunity system is dominant over acquired immunity. Materials and Methods: Carp (Cyprinus carpio L) were fed IP-PA1 for 7 days. Total RNA was extracted from the head kidney (a major immune organ of teleost fish), and interleukin (IL) -1 beta, IL-6, IL-8, IL-10, IL-12, TNF-alpha and transforming forming growth factor (TGF)-beta mRNAs were quantified by one-step real-time PCR. Phagocytic and bactericidal activity of head kidney leukocytes were estimated using zymosan and Aeromonas hydrophila (a pathogenic bacteria), respectively. Serum lysozyme activity was assayed with Remazol brilliant Blue stained Micrococcus lysodeikticus. Results: Oral administration of IP-PA1 for 7 days augmented the quantity of mRNA expression of IL-1 beta, IL-8, and TNF-alpha mRNA and reduced the expression level of IL-6 mRNA in the head kidney. Phagocytic and bactericidal activity of head kidney leukocytes were significantly enhanced. Moreover, serum lysozyme activities were significantly augmented. Conclusion: The results suggest that oral administration of IP-PA1 induced activation of M1 type macrophages in the immune organ of fish, and this enhanced the function of pathogen elimination. Since the functions of macrophages are highly preserved in comparative immunology, there is a high probability that the preventative or curative effect on various diseases that have been observed in mammals is also related to the activation of macrophages to the M1 type.