Screening And Studying Its Regulation Mechanism On TLR3of Antiviral Glycoside Compounds

Many plant polysaccharides exhabit a wide range of biological activities.Glycoside, the derivatives of polysaccharides, is a kind of important component oftraditional Chinese medicine which is safety and low toxicity. It also showsimmunomodulatory and antiviral activity. The poultry industry occupies a highproportion in animal farming industry. However, the spread of avian disease alwaysrestricts the development of poultry industry, especially the viral diseases, such ashighly pathogenic avian influenza,Newcastle disease,and infectious bursal disease. Ithas been reported that TLRs play an important role in resisting and controlling thevirus infection. In particular, TLR3can specifically recognize virus double-strandedRNA, such as nucleic acid of dsRNA virus, the dsRNA producing in the replicationprocess of ssRNA virus, and the RNA emerging during the expression andproliferation of DNA virus in the host cell. In this study, the glycoside which showsant-IBDV activity was screened, and the regulation of TLR3and other genes treatedby glycoside has been researched.The candidate glycosides include: baicalin, ginsenoside,oleuropein, geniposide,naringin, phlorizin, salidroside, astragalus polysaccharide, ginseng polysaccharide,and polysaccharopeptide. By using MTT and CPE, the anti-virus activity of theseglycosides were also detected when cocultured with DF1(infected by100TCID50). Itindicated that the maximum inhibitory rates (MIR) and therapeutic index (TI) ofbaicalin and oleuropein are>70%and>4respectively，so these two glycosides wereare able to inhabit the reproduction of virus. In addition, the maximum inhibitionratios of baicalin and oleuropein were greater than58%in blocking effect(pretreatment with baicalin or oleuropein three-days) and reproduction assay.However, they can not kill virus and inhabit the adsorption and penetration of virus. Thus, baicalin and oleuropein may exert the antivirus activity by regulating signalpath of cells. Real-time PCR indicated that baicalin and oleuropein regulated the levelof TLR3in cells infected by IBDV to various degrees.Additionally, the levels ofTLR3and IFN-βwere up-regulated in normal cell treated by baicalin and oleuropeinto some extent. Otherwise, the expression levels of TLR3, TRIF, and IFN-βwereincreased in the DF1cells which have been transfected using poly（I:C). While,baicalin and oleuropein showed ability of down-regulating the levels of TLR3, TRIF,and IFN-β.Therefore, the effect of baicalin and oleuropein can exert the antivirusactivity by regulating signal path of TLR3.This is the first research for the screening and researching the antiviral glycosideby using IBDV which could activating the TLR3signal path. This study provides anecessary basis for the application a of antiviral glycoside, such as baicalin andoleuropein.