BHK-21 cells were cultured overnight in 24 well plates before media was removed and serial dilutions (10-fold) of virus culture supernatants added to individual wells. Plates were incubated for 1 hr before media was aspirated and replaced with 0.5 ml of 0.8% methyl-cellulose medium (with 2% FBS). Plates were then incubated for 5 days before the media was removed and cells fixed in 4% formaldehyde for 20 min, rinsed in water, stained with crystal violet for 20 min then rinsed again. Plaques were counted manually and concentrations of plaque forming units per ml (pfu/ ml) in the cell culture supernatant calculated. For drug intervention studies, HepG2 cells were treated with compound, or DMSO, at the indicated concentration and time. While the culture supernatants were collected for plaque assay, cytotoxicity in HepG2 cells was monitored using fluorescein diacetate (FDA, Acros Organics, Belgium), 10 mg/ml added to cells for 25 min at room temperature, and measured using a fluorescent plate reader (485 nm excitation/535 nm emission).