Studies on the Use of Flagellin as an Immunostimulant and Vaccine Adjuvant in Fish Aquaculture

Immunostimulants and vaccines are important for controlling infectious diseases in fish aquaculture. In this study we assess the potential of flagellin to be used for such purposes in rainbow trout (Oncorhynchus mykiss). A recombinant flagellin from the salmonid pathogen Yersinia ruckeri (YRF) has been produced previously by us and shown to be a potent activator of inflammatory cytokines, acute phase proteins and antimicrobial peptides in vitro. Here we show that YRF is the most potent inflammatory activator of three bacterial PAMPs (LPS, peptidoglycan and flagellin) tested. The host response to flagellin was next studied in vivo. The YRF modulated gene expression was examined in two systemic (spleen and liver) and two mucosa-associated (gills and skin) tissues. YRF injection initiated a transient systemic inflammatory response with key pro-inflammatory cytokines (IL-1β, TNFα, IL-6, and IL-11 etc.) and chemokines (CXCL_F4 and CXCL-8) induced rapidly (by 6 h) but subsiding quickly (by 24 h) in multiple tissues. Consequently, a variety of anti-microbial pathways were activated systemically with heightened expression of acute phase proteins, antimicrobial peptides and complement genes in multiple tissues, which was sustained to 24 h in the liver and mucosal tissues. The Th17 cytokine IL-17A/F1 was also induced in the spleen and liver, and Th2 cytokine IL-4/13 was induced in the liver. However, the anti-inflammatory IL-10 and the Th1 cytokine IFNγ were refractory. A secreted form of TLR5 (TLR5s) was induced by flagellin in all tissues examined whilst the membrane form was refractory, suggesting that TLR5s may function as a negative feedback regulator. Trout liver appeared to be an important organ responding to flagellin stimulation, with marked induction of IL-11, IL-23P19, IL-17C1, SAA, and cathelicidin-2. YRF induced a strong antibody response. These antibodies reacted against the middle domain of YRF and were able to decrease YRF bioactivity. Intact YRF was necessary for its bioactivity, as deletion of the N-terminal, C terminal or middle domain of YRF led to functional loss. This study suggests that flagellin could be a potent immunostimulant and vaccine adjuvant for fish aquaculture

Re-examination of the rainbow trout (Oncorhynchus mykiss) immune response to flagellin : Yersinia ruckeri flagellin is a potent activator of acute phase proteins, anti-microbial peptides and pro-inflammatory cytokines in vitro

Acknowledgements E.W. was supported by a PhD studentship from the Ministry of Science and Technology of Thailand and Mahasarakham University. T.W. received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland), that is funded by the Scottish Funding Council (grant reference HR09011). This research was also funded by the European Commission under the 7th Framework Programme for Research and Technological Development (FP7) of the European Union (grant agreement No. 311993 TARGETFISH).Peer reviewedPostprin

Dissecting the immune pathways stimulated following injection vaccination of rainbow trout (Oncorhynchus mykiss) against enteric redmouth disease (ERM)

This research was financially supported by the European Commission under the 7th Framework Programme for Research and Technological Development (EP7) of the European Union (grant agreement No. 311993 TARGETFISH). E.W. was supported by a PhD studentship from the royal Thai government. T.W. received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland), that is funded by the Scottish Funding Council (grant reference HR09011).Peer reviewedPostprin

Insights into the evolution of the suppressors of cytokine signalling (SOCS) gene family in vertebrates

This study was supported by the National Natural Science Foundation of China (Grant No. 31702386), International Cooperation Science & Technology Planning Project of Guangdong Province of China (Grant No. 2017A050501037). E.W. was supported financially by the Ministry of Science and Technology of Thailand and Mahasarakham University. T.W. received funding from the Marine Alliance for Science and Technology for Scotland (MASTS), a pooling initiative funded by the Scottish Funding Council (grant reference HR09011).Peer reviewedPublisher PD

Rainbow trout (Oncorhynchus mykiss) adipose tissue undergoes major changes in immune gene expression following bacterial infection or stimulation with pro-inflammatory molecules

KAV was supported by ELANCO and SEPPIC to undertake a PhD program at the University of Aberdeen. EW was supported by a PhD studentship from the Ministry of Science and Technology of Thailand and Mahasarakham University. TH received funding from the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland). MASTS is funded by the Scottish Funding Council (grant reference HR09011).Peer reviewedPostprin

Characterisation of arginase paralogues in salmonids and their modulation by immune stimulation/ infection

Acknowledgements OB was supported by a PhD studentship from the Marine Collaboration Research Forum (MarCRF), which is a collaboration between the University of Aberdeen and Marine Scotland Science, Marine Laboratory (MSS), and through Scottish Government project AQ0080. EW was supported by a PhD studentship from the Ministry of Science and Technology of Thailand and Mahasarakham University. TW received funding from the Marine Alliance for Science and Technology for Scotland (MASTS), a pooling initiative funded by the Scottish Funding Council (grant reference HR09011), and JWH was supported by the Swiss National Science Foundation (grant reference CRSII3_147649-1).Peer reviewedPostprin

Comparative study of the effects of Montanide™ ISA 763A VG and ISA 763B VG adjuvants on the immune response against Streptococcus agalactiae in Nile tilapia (Oreochromis niloticus)

Acknowledgements We are highly grateful to thank Seppic, France, for providing us with the commercial products of MontanideTM ISA 763A VG and MontanideTM 437 ISA 763B VG. Funding This research project was financially supported by Mahasarakham University (Grant No. 6517022Peer reviewedPostprin

Sequence and Expression Analysis of Interferon Regulatory Factor 10 (IRF10) in Three Diverse Teleost Fish Reveals Its Role in Antiviral Defense

Acknowledgments This research was supported financially by the National Natural Science Foundation of China (31101928), the National Science and Technology Support Program of China (2013BAD20B06), the State Key Laboratory of Freshwater Ecology and Biotechnology (2010FB02) and the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) funded by the Scottish Funding Council (grant reference HR09011). Q.X. and Y.J. were supported financially by the National Scholarship Council of China. Funding: This research was supported financially by the National Natural Science Foundation of China (31101928), the National Science and Technology Support Program of China (2013BAD20B06), the State Key Laboratory of Freshwater Ecology and Biotechnology (2010FB02) and the MASTS pooling initiative (The Marine Alliance for Science and Technology for Scotland) funded by the Scottish Funding Council (grant reference HR09011). Q.X. and Y.J. were supported financially by the National Scholarship Council of China. The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.Peer reviewedPublisher PD