Novel TRIM Proteins Modulating the Innate Immune Response of Rainbow Trout (Oncorhynchus mykiss)

In higher vertebrates, Tripartite Motif (TRIM) proteins modulate the immune response by coordinating processes related to inflammation such as antiviral restriction, autophagy and inflammasome activation. In fish, TRIM proteins have been reported mainly in cyprinids (e.g., carp-Cyprinus carpio and zebrafish-Danio rerio) and salmonids (i.e., rainbow trout-Oncorhynchus mykiss). However, their molecular mechanisms and functions are still being described in aquatic animals. Thus, our study focused on characterizing novel TRIM proteins involved in the innate immunity of gill cells from rainbow trout (RTgill-W1 and primary cultures) stimulated with lipopolysaccharide (LPS) or polyinosinic-polycytidylic acid (poly I:C). Furthermore, an in vivo experiment with rainbow trout was performed to detect TRIM proteins after the challenge with Flavobacterium psychrophilum (a major bacterial pathogen affecting Chilean salmonid industry). In vitro results showed that OmTRIM25 triggered an LPS-induced expression of pro-inflammatory cytokines such as TNF-α2 and IL-1β. Moreover, in the fish experiment, OmTRIM25 and finTRIM2 were up-regulated in the gills two days post-infection (dpi), whereas IL-1β and TNF-α2 had a higher gene expression at four and six dpi, respectively. To investigate the immunological role of OmTRIM25, a gene silencing strategy using RNA interference (RNAi) was used, confirming the immunomodulatory function of OmTRIM25.