Abstract: To evaluate the effect of Forsythia Fructus on the proliferation of H5N1 and H9N2 avian influenza viruses(AIVs) and their mediated inflammation in vitro. The aqueous extract of Forsythiae Fructus was prepared in this experiment, and CCK-8 method was used to examine the cytotoxicity of Forsythiae Fructus aqueous extract to DF-1 cells, firstly. Three methods of treatments including infection after co-incubation of the AIVs and Forsythiae Fructus aqueous extract, treatment of cells by Forsythiae Fructus aqueous extract post virus infection and administration method treatment of cells by Forsythiae Fructus aqueous extract prior to virus inoculation were used to screen the optimal administration method of the of Forsythiae Fructus aqueous extract. TCID₅₀ method was used to detect the proliferation of H5N1 and H9N2 avian influenza viruses and the expression changes of inflammatory chemokines and cytokines were detected by qRT-PCR under the optimal administration method. The results indicated that Forsythiae Fructus aqueous extract showed no cytotoxicity to DF-1 cells below the concentration of 4 mg·mL^-1 and treatment of Forsythiae Fructus aqueous extract post virus infection was the optimal administration method. Forsythiae Fructus aqueous extract significantly reduced the virus titers of H5N1 and H9N2 AIVs at various time points in a concentration-dependent manner. The expression of CX3CL1, IL8L1, CCL5, SCYA4, IFN-α, IL-1β, IL-6 and TNF-α decreased significantly in H5N1 AIV treated by the aqueous extract group compared with the control. While in H9N2 AIV group, the expression of CX3CL1, IL8L1, CCL5, IFN-β, IL-6 and TNF-α showed a similar trend. These results indicated that Forsythiae Fructus has shown promising antiviral and antiinflammation activity by inhibiting the proliferation of H5N1 and H9N2 AIVs in DF-1 cells and reducing the expression of inflammation related cytokine genes.

Key words: avian influenza virus, virus proliferation, inflammation, Forsythiae Fructus