An interferon assay based on yield reduction of vesicular stomatitis virus antigen measured by enzyme immunoassay.

A modification of yield reduction assay for interferon was developed. The standard micromethod of inhibition of cytopathogenic effect (CPE) of vesicular stomatitis virus (VSV) was first applied and the amount of virus antigen released to the supernatant was then measured by a competitive enzyme immunoassay technique. This assay was four times more sensitive than the CPE inhibition method and was able to detect 0.50-0.25 international units/ml of human interferon-alpha and was also applicable to interferon-gamma determinations. It is a suitable method when small volumes of samples containing low levels of interferon are tested.