Taurochenodeoxycholic acid exerts anti-viral activities upon SGIV infection via anti-inflammatory response

Taurine chenodeoxycholic acid (TCDCA), a combination of taurine and chenodeoxycholic acid, plays anti-inflammatory roles in many diseases. However, little is known about its antiviral activity in aquaculture. Singapore grouper iridovirus (SGIV), a novel member of the genus Ranavirus, is an important viral pathogen in grouper aquaculture. Here, the effects of TCDCA on SGIV replication in vitro and in vivo were investigated. TCDCA treatment inhibited SGIV infection in grouper spleen (GS) cells, evidenced by the delayed CPE progression and decreased viral gene transcription, protein expression and viral progeny production. TCDCA treatment suppressed the mRNA level of pro-inflammatory factors and NF-kappa B promoter activities in SGIV-infected cells compared with mock-infected cells. Inhibition of NF-kappa B activity enhanced the inhibitory effects of TCDCA on SGIV replication, indicating that TCDCA inhibited SGIV replication in vitro via regulating host inflammatory response. Furthermore, TCDCA treatment protected grouper from SGIV infection, evidenced by the decreased mortality, the down-regulated transcription levels of viral genes and the improved pathological symptoms. In addition, the expression levels of SGIV induced pro-inflammation factors were decreased, while those of the antioxidant genes were increased after the supplement with TCDCA. Thus, our findings will not only contribute greatly to understanding the mechanism of SGIV pathogenesis, but also demonstrate that TCDCA might be a potential antiviral agent against SGIV infection.