Baicalin, a promising therapeutic drug against tilapia lake virus (TiLV) infection

Tilapia lake virus (TiLV) has caused serious deadly epidemics and still remains a devastating threat to tilapia aquaculture worldwide, with no practical therapeutic measures. In the study, anti-TiLV activities of 22 kinds of drugs are checked to develop a potential strategy for TiLV control. Safety of the selected drugs to E-11 cells is firstly evaluated to determine their maximum safe concentration (MSC). For preliminary screening in vitro , three 10-fold gradient-diluted drug concentrations (10 −2 , 10 −1 and 10 0 * MSC) are prepared. Baicalin shows the strongest inhibition activity on TiLV-induced cytopathic effects with an inhibition rate close to 80 % at 100 mg/L, and followed by favipiravir and amantadine hydrochloride. Baicalin can completely suppress viral infection at 200 mg/L as verification by Western blot and RT-qPCR analysis, and the 90 % inhibitory concentrations of baicalin on TiLV is 61.33 mg/L. Baicalin shows no obvious anti-TiLV activity by pre-treatment of E-11 cells before TiLV infection, while the infectivity of TiLV is significantly weakened following baicalin treatment, and baicalin has a strong anti-TiLV activity at the post-entry stage of TiLV infection. Besides, baicalin shows no obvious effects on the TiLV attachment to E-11 cells, but has significant inhibition on TiLV multiplication. Therefore, baicalin may have a direct virucidal effect, and/or block the viral genome translation and replication. For anti-TiLV activity evaluation in vivo , baicalin can improve the survival rate of TiLV-infected Nile tilapia ( Oreochromis niloticus ) to 81.8 % following treatment with 10 μg/g baicalin for 3 times, while that was 54.5 % for TiLV-infected tilapia without baicalin treatment. Moreover, the viral titers in liver of TiLV-infected tilapia are generally decreased after baicalin treatment. Results so far indicated that baicalin is a promising therapeutic drug against TiLV infection, providing a potential strategy for TiLV control and promoting the healthy development of tilapia aquaculture.