Innate and early immune responses to Yersinia ruckeri in the spleen of rainbow trout (Oncorhynchus mykiss)

Background: Yersinia ruckeri is a pathogen that can cause enteric redmouth disease in salmonid species, damaging global production of economically important fish including rainbow trout ( Oncorhynchus mykiss ). Herein, we conducted the transcriptomic profiling of spleen samples from rainbow trout at 24 h post- Y. ruckeri infection via RNA-seq in an effort to more fully understand their immunological responses. Results: : We identified 2498 differentially expressed genes (DEGs), of which 2083 and 415 were up- and down-regulated, respectively. We then conducted a more in-depth assessment of 78 DEGs associated with the immune system including CCR9, CXCL11, IL-1β, CARD9, IFN, CASP8, NF-κB, NOD1, TLR8α2, HSP90, and MAPK11, revealing these genes to be associated with 20 different immunological KEGG pathways including the Cytokine-cytokine receptor interaction, Toll-like receptor signaling, RIG-I-like receptor signaling, NOD-like receptor signaling, and MAPK signaling pathways. Additionally, the differential expression of 8 of these DEGs was validated by a qPCR approach and their immunological importance was then discussed. Conclusions: : Our findings provide preliminary insight regarding the innate and early immune responses of rainbow trout following Y. ruckeri infection and the base for future studies of host-pathogen interactions in rainbow trout.