| Human respiratory syncytial virus (RSV) is the most prevalent infectious agent of acute lower respiratory illness in infants and young children. It also helped to heighten awareness of the extent of mortality and morbidity in immunosuppressed populations and old populations. Now, ribavirin is the only cli nically approved small-molecule therapy for the treatment of RSV, it is strictly u sed in high risk and serious condition children patients. Another therapy for RS V infection are intravenous administration of immunoglobulin and humanized mo noclonal antibody (Synagis), which had been licensed for the clinical use and pr oduced better results. But they can not prevalently used in clinic due to its high price. Heretofore there is no vaccine availability for RSV prevention in clinic. T herefore, it is urgent to develop efficacious and cheap anti-RSV drug in therapy and prophylaxis.In this study, we will screen the antiviral Traditional Chinese me dicinal herbs against RSV in vitro model and separate active site, for the aim of supplying references to the Chinese prescription and the discovering new antiviral drugs.In the first part of the study, we established a rapid and reliable method for screening potential antiviral agents against respiratory syncytial virus based on the cytopathogenic effect inhibition assay. RSV infected different inoculated density Hep-2 cells and the numbers of cytopathogenic effect (CPE) were counted everyday. The appropriate experiment conditions were decided through evaluation of cells growth and the development of CPE. The antiviral effect of ribavirin was tested both by the plaque reduction assay and the improved method, and the results were analyzed with ANOVA by the software of SAS. The results show that the average EC50 has no significant difference with the plaque reduction assay (P>0.05). The appropriate experiment conditions were as follows :Hep-2 cells were inoculated in 96-well plastic plates about(].5~~2.0)xl04 per well, virus suspension containing an appropriate concentrations of the test compounds were inoculated after 24h~36h, CPE was evaluated after 4~5 days of incubations.In the second part of the study, we have screened 38 Chinese medicinal her bs, which are currently used for the treatment of respiratory tract infectious disea ses in China. The concentration reducing CPE by 50% in respect to virus contro 1 was estimated by the improved cytopathic effect assay and was defined as 50 % effective concentration (EC50) and cytotoxicity in Hep-2 was estimated by the MTT (3-(4,5-dimethylthiazole-2-yl) 2,5-diphenyl tetrazolium bromide) assay and w as defined as 50% cytotoxic concentration (CCso),.The selective index or the rati 0 of cytotoxicity (CC50) to antiviral activity (EC50) (SIKX50/EC50) were calculate d, SI>4 will be consided significante. Twenty-three of the 38 medicinal herbs sh owed potent or moderate antiviral activities against RSV with EC50 ranging from 12.2ug/ml to 719.1|ig/ml, and with SI ranging from 4 to 969. All of these tradit ional Chinese medicines extracts were considered active, and of interest for furth er investigation.Chrysanthemum (Flos dendranthemae Morifolii ) has been used in china for a long time. But there is little study on the active site of antiviral activity on RSV. In the former part of study, The highest selectivity index was 969.So, it is worth further investigating to identify the active sites. The antiviral properties wa s further investigated to identify the antiviral mechanism. Chrysanthemum shows strong antiviral properties in the course of replication in vitro.In sum, the active site was tracing by antiviral pharmacology assay in vitro. Firstly, Chrysanthemum powder were extracted with 95% EtOH. The extract was further purified by system extract assay which used Petroleum ether , Chlorofor m and acetic ether in order. The active parts of these extractions were confirmed by antiviral pharmacology assay in vitro and in vivo. It was found that the sam pie extracted by the acetic ether was the active part. Secondly, the acetic etherex...
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