Rapid quantitation of interferon with chronically oncornavirus producing cells

The capacity of interferon to inhibit virus production in cells chronically infected with oncornavirus enabled to develop a simple system for interferon quantitation that was independent of exogenous viral infection. The release of the virus to the culture medium was determined by its reverse transcriptase activity. The inhibitory effect of interferon in this system was linearly proportional to the log of its dilution over a range between 5 and 80% inhibition. The sensitivity of the system was comparable to that of the vesicular stomatitis virus plaque reduction assay, whereas its reproducibility was found to be even better. This method is very rapid and can be completed within less than 24 h.