Objective To study the
inhibition of respiratory syncytial virus (RSV) by Ara-AMP,
virazole,bupleu-rum root injection (bupleurum)
and their joint application.Methods Ara-AMP,virazole and bupleurum were diluted to dif-ferent concentrations,and the cell poison reaction by drug cytotoxicity was observed by cell culture;cytopathic effect (CPE) and RSV
inhibition by drugs were observed by the way of drug administration two hours after Vero cells were
infected by virus. Re-sults The toxic dosages (TD) to Vero cells of Ara-AMP,virazole and bupleurum were 0.25,0.2 and 2 mg/ml,respectively. The drug cytotoxicity was not enhanced when Ara-AMP or virazole combined with bupleurum,but it was done when Ara-AMP combined with virazole.Each of the three drugs inhibited RSV in Vero cells,and the effective dosage of Ara-AMP and virazole was both 25 μg/ml,and bupleurum was 125 μg/ml.The combinations of 3 drugs showed synergism without an-tagonism.After Vero cells were infected by RSV 100 TCID 50 /0.1 ml(ie. median tissue culture infective dose),the results showed RSV was inhibited significantly when Ara-AMP 125 μg/ml,virazole 100 μg/ml and bupleurum 1 000 μg/ml were given to Vero cells tubes in the time of Vero cells just being infected and having been infected for 2 h and 12 h;the inhibition effects were reduced when drugs were given after Vero cells had been infected for 24 h;and no inhibition effects were showed after 36 h.Conclusion RSV could be inhibited by Ara-AMP,virazole and bupleurum,respectively.Significant synergism against RSV was showed by their joint application,this not only can decrease the dosage,toxicity,but also enhance the inhibition ef-fect on RSV obviously.