Biography
Dr. Tiehui Wang
Dr. Tiehui Wang
University of Aberdeen, UK
Title: BACTERIAL FLAGELLIN IS A POTENT IMMUNE STIMULANT OF FISH IN VITRO AND IN VIVO: POTENTIAL APPLICATIONS IN AQUACULTURE
Abstract: 

Flagellin is the principal component of the bacterial flagellum and a major target of the host immune system. To provide new insights into the role of flagellin in fish immune responses to flagellated microorganisms and its potential use in aquaculture, recombinant flagellins have been produced in E. coli from pathogenic and non-pathogenic bacteria and their bioactivity investigated in vitro in the rainbow trout macrophage cell line RTS-11, and in vivo in rainbow trout. The full-length recombinant flagellins, with different size and potency, are strong activators of pro-inflammatory cytokines, acute phase proteins, antimicrobial peptides and subunits of the IL-12 cytokine family in vitro. Administration of flagellin in rainbow trout by ip injection initiated a rapid systemic inflammatory response. The expression of major pro-inflammatory cytokines (IL-1β, TNF-α, IL-6, IL-8 etc.) was seen from 6-24 h in multiple tissues after injection. The anti-microbial defence was also activated systemically with heightened expression of acute phase proteins (eg SAA) and antimicrobial peptides (cathelicidins, hepcidin etc.) in multiple tissues. However, the anti-inflammatory and adaptive pathways are refractory to flagellin, with no induction of IL-10 and IFNγ expression seen. The recombinant flagellin, when immunized with Freund’s adjuvant, induced a strong antibody response in rainbow trout. The antibody produced in fish reacts against the middle domain of the flagellin protein. Furthermore, a miniature form of flagellin (mFlagellin), with the antigenic middle domain removed, has been engineered. This mFlagellin is small in size, high in potency, easy to produce and stable. The application of the mFlagellin in aquaculture will be discussed, in terms of immune stimulation and use as a novel vaccine adjuvant in fish.