In situ enzyme immunoassay for antiviral susceptibility testing of respiratory syncytial virus.

An enzyme immunoassay (EIA), performed directly on fixed infected monolayers of HEp-2 cells in microtiter plates, was compared with the conventional plaque reduction assay (PRA) method for the determination of antiviral activity of ribavirin against respiratory syncytial virus. A 50% reduction in virus replication was observed at 3.4 and 5.9 mg/L of the drug by EIA and PRA, respectively. EIA is simple to perform and reproducible and has objective end points. Moreover, EIA has advantages over PRA in that results are available sooner and a much wider range of inoculum size can be used without affecting susceptibility data. EIA is suitable for the rapid susceptibility and accurate testing of a large number of clinical isolates.