Vero cells were inoculated at MOI = 0.1 and incubated at 35°C for 4 days. Cells and supernatant were scraped together and total RNA was extracted using Trizol reagent (Invitrogen) followed by an additional phenol-chloro-form extraction and ethanol precipitation. RNA was separated on 1% agarose gel in the presence of 0.44 M formaldehyde and transferred to a positively charged nylon membrane (Amersham Biosciences). The RNA was hybridized with gene-specific riboprobes labeled with digoxigenin using a DIG RNA labeling kit (Roche). The hybridized bands were visualized with a DIG luminescent detection kit (Roche).