Differential expression of the pro-inflammatory cytokines IL-1β-1, TNFα-1 and IL-8 in vaccinated pink (Oncorhynchus gorbuscha) and chum (Oncorhynchus keta) salmon juveniles

Laboratory-reared pink and chum salmon juveniles (∼2 g) received an intraperitoneal injection with a commercial, unadjuvanted Aeromonas salmonicida bacterin or sterile saline. Relative to elongation factor-1A, expression levels of genes encoding the proinflammatory cytokines interleukin-1β-1 (IL-1β), tumour necrosis factor-α-1 (TNFα) and interleukin-8 (IL-8) in pools of kidney and liver were examined 6- and 24-h after injection. Expression of IL-1β was significantly elevated in pink and chum salmon by 6-h, and declined in pink salmon but not in chum salmon by 24-h. Similarly, expression of TNFα was significantly elevated in both species at 6 h and only in chum salmon after 24-h. Expression of IL-8 was significantly elevated in both species at 6- and 24-h after injection. Expression of the three proinflammatory cytokine genes differed between salmon species both in the timing and magnitude of their expression. The significance of these differences with respect to immune function in these fish requires further research.