Parameters for the characterization of antiviral compounds in cell culture experiments

The antiviral activity of seven compounds against the replication of herpes simplex and rubella viruses in cell culture was examined using different parameters as follows: cytotoxicity (CT) of compounds giving 50 and 0% (CT50, CT0) reduction in cell growth; the slope of the curve of CT; decrease in virus infectivity titer in the presence of CT50 and CT0 concentrations of the compound (D); maximum amount of the compound giving zero inhibition of virus replication (I0); therapeutic index (TI); further decrease in the virus titer after withdrawal of the compound from the medium (DS); and the 'shadow' showing the degree of virus replication after withdrawal of the compound from the medium. The higher the values of D, DS, TI, and the lower the values of I0 and the 'shadow', the more valuable the antiviral compound. These parameters characterize the CT, the potency and the specificity of the antiviral compound and they may be used in antiviral tests to select new and more specific antiviral agents.