Bioimmunoassays (BIAs) of human interferon.

Simple, sensitive, and reproducible assay systems for measurement of the biological activity of interferon are described. The methods used are based on the quantification of cell membrane-bound viral and cellular antigens in interferon-treated cells by enzyme immunoassays. To measure the antiviral activity, samples of human interferon are titrated in microplates with human or bovine cells. After incubation with challenge virus (vesicular stomatitis or herpes simplex virus) the cells are fixed with glutaraldehyde and assayed for viral antigens by enzyme-labeled antibodies. This assay permits the detection of less than 0.1 unit of interferon per milliliter, after optimization of several factors, such as type of cell, multiplicity of infection, temperature, and period of incubation. The effect of interferon on cellular antigens is measured in a similar way, by using peroxidase-labeled antibodies directed against beta 2-microglobulin. The two types of assays described appear suitable for kinetic experiments and for detection of interferons of different specificities in body fluids.