Novel TRIM Proteins Involved in Rainbow Trout Innate Immune Response

In mammals, Tripartite motif-containing (TRIM) proteins modulate the immune response by coordinating pro-inflammatory related processes such as antiviral restriction, cellular autophagy and inflammasome activation. In fish, TRIM proteins have been reported mainly in cyprinids (e.g., carp, zebrafish) and salmonids (rainbow trout). However, their molecular mechanisms and functions are still being described these animals. Our study focused on characterizing novel TRIM proteins involved in the innate immune response of gill cells from rainbow trout stimulated with LPS or poly(I:C). Also, a fish trial was performed to detect TRIM proteins of rainbow trout after a challenge with Flavobacterium psychrophilum, a salmonid bacterial pathogen. At in vitro level, the results showed that, among several TRIM proteins, OmTRIM25 triggered an LPS-induced expression of pro-inflammatory cytokines (TNF-α2 and IL-1β), suggesting a potential local modulatory function. Moreover, in the fish trial, while OmTRIM25 and finTRIM2 were up-regulated in the gills two days post infection (dpi), IL-1β and TNF-α2 reached their peaks of expression at four- and six-dpi. Finally, after delving into the function of OmTRIM25 by RNA interference (RNAi) gene-silencing, we propose that TRIM proteins such as OmTRIM25 are needed to induce the pro-inflammatory response in the gills of rainbow trout, which confirms their immunomodulatory function.