A cell line modified genetically (Vero-ICP10-SEAP) that responds to infection by herpes simplex virus (HSV) was established. The cell line was constructed by stable transfection of Vero cell with a plasmid encoding the secreted alkaline phosphatase (SEAP) driven by the promoter of the HSV-2 ICP10 gene. Following infection with HSV, the stable line secretes a high level of the SEAP in the supernatants as measured by a chemiluminescence-based assay. The detection system is sensitive to an HSV titer as low as a single plaque-forming unit (PFU), with a linear range up to the equivalent of 2.5 x 10(4) PFU inoculum after infection for 24 h. There was no detectable enhancement in SEAP activities following inoculations with several viruses other than HSV. The Vero-ICP10-SEAP cell line was also utilized to develop an assay for determination of antiviral susceptibility given that the induced SEAP activity appeared to reflect the numbers of plaque. Evaluations of the stable line with representative acyclovir (ACV)-sensitive and-resistant HSV isolates demonstrated that their drug susceptibilities were determined accurately. In summary, this novel SEAP reporter system is a sensitive means for rapid diagnosis, quantitation, and drug susceptibility testing for HSV, with potential to the development of an automated assay. (C) 2002 Wiley-Liss, Inc.