Innate response of rainbow trout gill epithelial (RTgill-W1) cell line to ultraviolet-inactivated VHSV and FliC and rhabdovirus infection

Gills reportedly play a crucial role in induction of an antiviral immune response in fish. We investigated the expression of innate response genes in the rainbow trout gill epithelial cell line RTgill-W1 36 h after pretreatment with ultraviolet-inactivated viral hemorrhagic septicemia virus (UV-VHSV), flagellin C protein from Edwardsiella tarda (FliC), VHSV and SVCV using an Agilent 4 × 44k cGRASP salmonid microarray. RTgill-W1 cells pretreated with UV-VHSV, triggered an independent gene expression profile from those treated with a recombinant flagellin C protein from Edwardsiella tarda. In addition, exposure of RTgill-W1 cells to live viruses spring viremia of carp virus and viral hemorrhagic septicemia virus induced a less robust transcriptional change of 24 and 22 gene probes, respectively, when compared to 123 genes for UV-VHSV. Further the pretreatment of RTgill-W1 cells with (UV-VHSV) significantly reduced VHSV genome copy number at 6 d post infection (dpi) relative to the FliC-treated and untreated control. A quantitative PCR was used to study the transcriptional modulation of a set of 25 innate immune-related genes highlighted by the microarray data and a panel of 7 established antiviral genes in the protected cells. Notably, the expression of ifn1, ifn2, mx1 and mx3 were expressed more in untreated cells than in UV-VHSV-treated cells where virus replication was inhibited. The results from this study shed light on the mechanisms and pathways used by teleost gill epithelium innate immunity in combating viral and bacterial infection.