Susceptibility of Vero E6 cells to tilapia lake virus (TiLV) and anti-TiLV activity of type I interferon

Tilapia lake virus (TiLV) is an emerging orthomyxovirus-like pathogen first identified in Israel in 2014. TiLV can cause up to 90% mortality in tilapia and poses a severe threat to the global tilapia industry. There is no cure for TiLV infection and no commercially available vaccine. It was shown that TiLV can infect cell lines from many different fish species, but TiLV infection and replication in mammalian cells have not been documented. Here, we report that TiLV can infect and replicate in Vero E6 cells, thus expanding the systems available for studying TiLV to a well-characterized cell line. In addition, we investigated the effect of mammalian type I interferon on TiLV infection in this cell culture system. Our results show the robust antiviral activity of mammalian type I interferon against TiLV. Importantly, a recombinant fish type I interferon that we produced in mammalian cells also exhibited potent antiviral activity against TiLV in E11 cells. In conclusion, our studies demonstrate the protective effect of type I interferon against TiLV infection, which may point to a mechanism of TiLV pathogenesis and aid in developing vaccines and antiviral therapies against this important fish pathogen.