Nutritional immunomodulation of Atlantic salmon response to Renibacterium salmoninarum bacterin

• Published in: Frontiers in Molecular Biosciences
• Main Authors: Emam, Mohamed, Eslamloo, Khalil, Caballero-Solares, Albert, Lorenz, Evandro Kleber, Xue, Xi, Umasuthan, Navaneethaiyer, Gnanagobal, Hajarooba, Santander, Javier, Taylor, Richard G., Balder, Rachel, Parrish, Christopher C., Rise, Matthew L.
• Format: Article in Journal/Newspaper
• Language: unknown
• Published: Frontiers Media SA 2022
• Subjects: Atlantic salmon; Salmo salar
• Online Access: http://dx.doi.org/10.3389/fmolb.2022.931548; https://www.frontiersin.org/articles/10.3389/fmolb.2022.931548/full

We investigated the immunomodulatory effect of varying levels of dietary ω6/ω3 fatty acids (FA) on Atlantic salmon ( Salmo salar ) antibacterial response. Two groups were fed either high-18:3ω3 or high-18:2ω6 FA diets for 8 weeks, and a third group was fed for 4 weeks on the high-18:2ω6 diet followed by 4 weeks on the high-18:3ω3 diet and termed “switched-diet”. Following the second 4 weeks of feeding (i.e., at 8 weeks), head kidney tissues from all groups were sampled for FA analysis. Fish were then intraperitoneally injected with either a formalin-killed Renibacterium salmoninarum bacterin (5 × 10 7 cells mL −1 ) or phosphate-buffered saline (PBS control), and head kidney tissues for gene expression analysis were sampled at 24 h post-injection. FA analysis showed that the head kidney profile reflected the dietary FA, especially for C 18 FAs. The qPCR analyses of twenty-three genes showed that both the high-ω6 and high-ω3 groups had significant bacterin-dependent induction of some transcripts involved in lipid metabolism ( ch25ha and lipe ), pathogen recognition ( clec12b and tlr5 ), and immune effectors ( znrf1 and cish ) . In contrast, these transcripts did not significantly respond to the bacterin in the “switched-diet” group. Concurrently, biomarkers encoding proteins with putative roles in biotic inflammatory response ( tnfrsf6b ) and dendritic cell maturation ( ccl13 ) were upregulated, and a chemokine receptor ( cxcr1 ) was downregulated with the bacterin injection regardless of the experimental diets. On the other hand, an inflammatory regulator biomarker, bcl3 , was only significantly upregulated in the high-ω3 fed group, and a C-type lectin family member ( clec3a ) was only significantly downregulated in the switched-diet group with the bacterin injection (compared with diet-matched PBS-injected controls). Transcript fold-change (FC: bacterin/PBS) showed that tlr5 was significantly over 2-fold higher in the high-18:2ω6 diet group compared with other diet groups. FC and FA associations highlighted the ...