A comparison of the antiproliferative and antiviral activities of alpha-, beta- and gamma-interferons: description of a unified assay for comparing both effects simultaneously.
An assay system is described which allows simultaneous measurement of antiviral (AV) and antiproliferative (AP) activities of various interferons (IFNs) with the same indicator cells and tests one biological function, i.e. the reduction of DNA synthesis. Human IFN-alpha, -beta, and -gamma preparations were investigated for their respective AV and AP activities. In repeated independent experiments the AP:AV ratio was found to be constant for each IFN preparation. However, striking difference in the AP:AV ratios was found between the preparations, being highest in IFN-gamma and lowest in IFN-alpha. The validity of this assay was substantiated by the observation that the AP activity of the IFNs is not influenced by virus once the cells are protected by sufficient amounts of IFN and that the score of the microscopically assessed cytopathic effect (CPE) strongly correlates with the reduction of [3H]TdR uptake in the cultures. The AP:AV ratio of a Corynebacterium parvum induced IFN resembled that of the IFN-alpha-reference, suggesting that contrary to previous reports, the C. parvum induced is of alpha type. It is suggested that the assay system presented here provides a simple means not only of comparing AP and AV ratios of various IFNs but also of characterizing IFNs of unknown type.