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

Abstract

Enteric redmouth disease (ERM or yersiniosis) is one of the most important diseases of salmonids and leads to significant economic losses. It is caused by the Gram-negative bacterium Yersinia ruckeri but can be controlled by bacterin vaccination. The first commercial ERM vaccine was licenced in 1976 and is one of the most significant and successful health practices within the aquaculture industry. Although ERM vaccination provides complete protection, knowledge of the host immune response to the vaccine and the molecular mechanisms that underpin the protection elicited is limited. In this report, we analysed the expression in spleen and gills of a large set of genes encoding for cytokines, acute phase proteins (APPs) and antimicrobial peptides (AMPs) in response to ERM vaccination in rainbow trout, Oncorhynchus mykiss. Many immune genes in teleost fish are known to have multiple paralogues that can show differential responses to ERM vaccination, highlighting the necessity to determine whether all of the genes present react in a similar manner. ERM vaccination immediately activated a balanced inflammatory response with correlated expression of both pro- and anti-inflammatory cytokines (eg IL-1β1-2, TNF-α1-3, IL-6, IL-8 and IL-10A etc.) in the spleen. The increase of pro-inflammatory cytokines may explain the systemic upregulation of APPs (eg serum amyloid A protein and serum amyloid protein P) and AMPs (eg cathelicidins and hepcidin) seen in both spleen and gills. We also observed an upregulation of all the α-chains but only one β-chain (p40B2) of the IL-12 family cytokines, that suggests specific IL-12 and IL-23 isoforms with distinct functions might be produced in the spleen of vaccinated fish. Notably the expression of Th1 cytokines (IFN-γ1-2) and a Th17 cytokine (IL-17A/F1a) was also up-regulated and correlated with enhanced expression of the IL-12 family α-chains, and the majority of pro- and anti-inflammatory cytokines, APPs and AMPs. These expression profiles may suggest that ERM vaccination activates host innate immunity and expression of specific IL-12 and IL-23 isoforms leading to a Th1 and Th17 biased immune response. A late induction of Th2 cytokines (IL-4/13B1-2) was also observed, that may have a homeostatic role and/or involvement in antibody production. This study has increased our understanding of the host immune response to ERM vaccination and the adaptive pathways involved. The early responses of a set of genes established in this study may provide essential information and function as biomarkers in future vaccine development in aquaculture.

Gene expression analysis of isolated salmonid GALT leucocytes in response to PAMPs and recombinant cytokines

“…This induction potentially reflects Th cell or ILC responses, and suggests that multiple subpopulations may be present. Interestingly, IL-4/13 exists as two genes in teleost fish (IL-4/13A, IL-4/13B), with IL-4/13A being more highly expressed constitutively but IL-4/13B is more inducible, as seen post vaccination and infection [56,61]. Similar to PHA, rIL-21 was a good inducer of IL-4/13B, IL-17A/F, IL-22 and IFN-γ, and to a small extent TNF-α, however rIL-2 had very limited effects, although found to be an essential regulator of T cell responses in salmonids [28].…”

Plasma Proteome Responses in Salmonid Fish Following Immunization

“…using disease challenge tests), or indirectly, by studying changes in immune parameters, for example by confirming an antigen-specific antibody response ( 8 , 9 ) or recording changes in the expression of immune molecules (e.g. ( 10 , 11 )). Such work usually relies on the terminal sampling of tissues from large numbers of fish, at different time points, to adequately capture the response dynamic.…”

Distinct response of immune gene expression in peripheral blood leucocytes modulated by bacterin vaccine candidates in rainbow trout Oncorhynchus mykiss: A potential in vitro screening and batch testing system for vaccine development in aquaculture

“…Rainbow trout (Oncorhynchus mykiss) purchased from the Mill of Elrich Trout Fishery (Aberdeenshire, Scotland, UK) were maintained at 14±1°C in a freshwater recirculation aquarium [27,30]. The PBL from four fish were prepared as described previously [25].…”

“…Genes involved in the inflammatory response are modulated in vivo by vaccination in salmonid lymphoid organs such as head kidney [33] and spleen [30]. Therefore, we examined first in PBL the expression of proinflammatory cytokines (IL-1β [34], TNFα [35], IL-6, IL-11 [36], M17 [37] and IL-34 [38]), chemokines (IL-8 and CXCL11_L1 [39]), anti-inflammatory cytokines (IL-10 [40], TGF-β1 [41] and nIL-1Fm [42]), and negative regulators of cytokine signalling (SOCS) [43].…”

“…Lastly, the expression of several APP and AMP genes that are known to be induced in vivo by vaccination and bacterial infection was studied [30,33]. COX2 expression was rapidly induced at 4 h and followed the expression pattern of the other inflammatory genes (Fig.…”