2.7. HCMV GFP-Based Replication Assay

HCMV GFP-based replication assays were performed as described previously [49,50]. In brief, 200,000 HFFs were cultivated in 12-well plates for the infection with parental HCMV AD169-GFP or UL97 deletion mutants ∆231–255, ∆256–280 and ∆231–280 at a MOI of 0.25 GFP-FU/cell (i.e., 25% GFP-forming doses of a multi-round infection measured at 7 d) and treated with maribavir (MBV) or ganciclovir (GCV) at serial concentrations. At 7 d.p.i., the cells were lysed and total lysates were subjected to automated GFP quantitation using a Victor 1420 multilabel counter (Perkin-Elmer, Waltham, MA, USA). Mean values ± SD of quadruplicate determinations are given (infections in duplicates, GFP measurements in duplicate).