A practical cytopathic effect/dye-uptake interferon assay for routine use in the clinical laboratory

The clinical value of interferon (IFN) level determinations has been demonstrated, but a practical assay procedure for routine use in the diagnostic laboratory has not been available. The authors examined the susceptibility of five cell lines (WISH, HEp-2, Vero, A549, and WI-26VA4) to vesicular stomatitis virus (VSV) and encephalomyocarditis virus (EMCV), and compared the response of these cells to the inhibitory activity of IFN-alpha and IFN-gamma for the respective viral cytopathic effect (CPE). The WISH-EMCV system was the most sensitive for IFN-alpha, and was approximately as sensitive as the HEp-2-VSV system for IFN-gamma. WISH cells were found to be significantly more sensitive for both IFN-alpha and IFN-gamma when EMCV, instead of VSV, was used (P less than 0.001). Therefore, the latter system served as the basis for developing a CPE dye-uptake procedure that was found to be considerably more rapid but slightly less sensitive than the conventional technic. However, both procedures were equally reproducible and should be suitable for automation.