ERVW-1 and infection: Importantly, we also found that these A549 cells stably expressing the ZIKV-NLS-GFP reporter supported ZIKV replication to a similar level as the parental A549 cells, as determined by the number of cells that stained positive for ZIKV Envelope protein (Env) at 24, 36, and 48 h post-infection with ZIKV-PR (Figure 2d).