Establishment of a tilapia lake virus (TiLV)-susceptible cell line for anti-TiLV Chinese herbal compound screening

Tilapia lake virus (TiLV) has caused many deadly epidemics in wild and farmed tilapia, posing a great threat to the global tilapia-based industry. It is necessary and urgent to develop effective measures for TiLV control. Previously, we isolated a TiLV strain from naturally diseased tilapia, and its main target tissues are liver, spleen and brain. In the study, a TiLV-susceptive cell line is established based on the tissue tropism, and anti-TiLV activity of 11 Chinese herbal compounds (CHCs) is checked in vitro. A cell line from the brain of tilapia, designated as Nt-B, can be continuously subcultured for >100 passages and maintain a good proliferating state in L-15 media supplemented with 10% FBS at 28 degrees C. Following infection with TiLV, a series of cytopathic effects can be observed, including rounding, accumulation, vacuolation and detachment of cells. Enveloped viral particles can be observed in TiLV-infected cells, and TiLV-specific bands are identified by PCR analysis, confirming susceptibility of Nt-B cells to TiLV. For anti-TiLV activity evaluation, the selected CHCs show inhibition activity on TiLV-induced CPEs in different degrees except CHC-I. Two kinds of CHCs, CHC-II and CHC-X, have inhibition activity on TiLV-induced CPEs higher than 80%. Besides, the 90% inhibitory concentrations of CHC-II and CHC-X on TiLV are 51.12 +/- 3.04 and 68.28 +/- 6.37 mg/L, respectively. In summary, the newly established Nt-B cell line provides a useful tool for TiLV-related studies, moreover, CHC-II is a promising therapeutic agent against TiLV infection. Further studies will be required to reveal the active compounds and anti-TiLV mechanism of CHC-II.