Epstein-Barr virus (EBV) is associated with severe human diseases. Therapies with conventional anti-herpesviral drugs are mostly ineffective so that novel drugs are urgently needed. As cell culture-based evaluation systems are required, a GFP (green fluorescent protein) reporter system was generated, which was conceived for an easy quantitation of lytic EBV replication and the analysis of EBV drug sensitivity. A reporter construct was generated on the basis of an EBV plasmid mini-replicon which enabled an episomal maintenance and selection of stably transfected Raji and 293T cell clones. Controlled by the viral lytic origin of DNA replication (oriLyt), this reporter construct could be activated through experimental EBV infection or through chemically stimulated reactivation from EBV latency. Using this system, the sensitivity of EBV to the broad-spectrum anti-herpesviral drug artesunate could be demonstrated: (i) artesunate inhibits EBV in the low micromolar range, (ii) two different strains of EBV are equally artesunate-sensitive, (iii) inhibition is detectable similarly in EBV-infected epithelial cells or lymphocytes, and (iv) the mode of antiviral action is based on a block of viral immediate early protein synthesis. The data demonstrate the usefulness of this reporter system for the quantitation of EBV replication and for determining EBV drug sensitivity.
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