Mechanism of Illicium verum Hook. f. extracts to regulate host immune response against Singapore grouper iridovirus

【Objective】 To explore mechanism of Illicium verum Hook.f. extracts(IVE) to regulate host immune response against Singapore grouper iridovirus(SGIV) from the perspective of immune response, so as to provide a theoreti-cal basis for utilizing I. verum Hook. f. to be developed into a green, safe and efficient fishery drug for grouper breeding industry.【Method】 The safe working concentration of IVE was determined by light microscope observation and CCK-8 cell viability assay;the real-time fluorescence quantitative PCR(qRT-PCR) method was used to analyze the effect of IVE on the host interferon(IFN) related genes immune factors(IFN, STAT1, PKR, ISG15, IKKα, STING and IRF3) expression;then the effect of IVE against SGIV at the cellular level was analyzed by light microscopy and qRT-PCR methods. The anti-SGIV effect of IVE was further verified through in vivo grouper experiment.【Result】 The safe working concentration of IVE was ≤ 0.5 mg/mL;GS cells IVE-pretreated for 2 h could significantly(P<0.05, the same below) or extremely significantly(P<0.01, the same below) activate the expression of genes involved in STAT1 system(STAT1, PKR, IKKα, IRF3 and STING). At 24 h and 48 h of SGIV infection, the cytopathic effects(CPEs) of IVE-pretreated cells occurred less significantly than GS cells without IVE pretreatment;and MCP gene relative expression of SGIV decreased extremely significantly, suggesting that IVE could effectively inhibit the infection of SGIV. Moreover, IVE could enhance IFN-related gene expression of SGIV-infected GS cells as IFN, STAT1 and IRF3 genes were extremely significantly up-regulated 24 h after infection and PKR, IKKα, ISG15 and STING genes were significantly or extremely significantly up-regulated 24 h and 48 h after infection. In the in vivo experiment, the relative expression of the MCP gene of SGIV in the spleen of the grouper injected with IVE and SGIV was extremely significantly lower than that of the grouper injected with SGIV at 24 and 48 h.【Conclusion】 IVE can inhibit SGIV infection probably through the mechanism which induces expression of IFNrelated genes to activate anti-viral function of host, thus indirectly fight against SGIV. It also suggests that I. verum Hook. f. has the potential to be developed into an anti-aquatic virus drug.