Antiviral activities of Lonicera japonica Thunb. Components against grouper iridovirus in vitro and in vivo

Abstract Grouper iridovirus was isolated from the diseased hybrid grouper in Guangxi province, China (SGIV-Gx), which has a high mortality rate in cultured groupers. Effective medicines for controlling SGIV-Gx infection are urgently needed. Lonicera japonica Thunb. (L. japonica) is a well-known medicinal plant. The application of L. japonica components against SGIV-Gx infection was assessed in this study. The safe, appropriate working concentration of each L. japonica component was identified (L. japonica aqueous extracts LAE ≤ 10 mg/mL; chlorogenic acid, CGA ≤ 250 μg/mL; cryptochlorogenic acid, CCGA≤500 μg/mL; isochlorogenic acid A, IAA ≤ 250 μg/mL; isochlorogenic acid B, IAB ≤ 250 μg/mL; isochlorogenic acid C, IAC ≤ 500 μg/mL; caffeic acid, CA ≤ 125 μg/mL; luteolin (LT) and inositol (IS), no cytotoxic effects even at 2000 μg/mL) in vitro and in vivo. The inhibitory activities of each L. japonica component against SGIV-Gx infection were analyzed by three methods: light microscopy, Q3-AFMP and RT-qPCR, which proved that, some L. japonica components (LAE, IAA, IAB, IAC, CA, LT, IS) exhibited the antiviral activity against SGIV-Gx infection in a dose-dependent manner, and LAE, IAA, IAB, IAC, CA, LT had the best antiviral activity against SGIV-Gx infection, with above 90% of inhibitory percentage. Overall, the results in this study suggest that L. japonica components have antiviral effects, making this plant a promising candidate for developing effective medicines for preventing and controlling SGIV-Gx infection in farmed groupers.