Ad vector overexpression of gO during ME replication. nHDF or HFFFtet cells were infected with ME for 2 days and then superinfected with Ad vectors expressing either GFP or MEgO for an additional 4 days. Extracts of infected cells (A) or extracellular virions (B) were separated by reducing (A and B, top) or nonreducing (B, bottom) SDS-PAGE and analyzed by immunoblot probing for MEgO, actin, MCP, or gL, as indicated to the right.