Development of an immunofluorometric, high-capacity, cell-based assay for the measurement of human type I and type II interferons

We have developed a cell-based 96-well microtiter plate, high throughput as say for measuring both type I and type II interferon (IFN) activity on huma n cells. This assay makes use of a previously described IFN-specific report er stably expressed in human HT 1080 cells. The induction of the reporter b y IFN is determined by measuring the IFN-dependent expression of CD2 on the cell surface. The cytokine-induced expression of CD2 occurs within 48 h an d is measured using a time-resolved fluorometric immunoassay. The limit of detection for type I IFN is >0.4 IU/ml, Interassay and intraassay coefficie nts of variation were 1.1% and 1.3% for the medium control (31 IU IFN beta 1b/ml), respectively. The limit of detection for type II IFN is >8 IU/ml, a nd the assay coefficients of variation are similar to those determined for type I IFNs, The level of sensitivity for this assay is comparable to other assays commonly used to measure IFN activity on cells. The current assay h as an advantage over antiviral and antiproliferative assays, in that there is no requirement for the use of pathogenic virus or for determining viable cell numbers. The current assay is ideally suited for increasing sample sc reening and high-capacity automation, making it an excellent tool for drug discovery.