Packaging and infection of pBG78 replicons in BHK and C6/36 cells. pBG78 PIPS were generated by co-transfecting pBG78 and pBG44 plasmid DNA into BHK cells. Media was collected 24 hrs post transfection and 100 ul of the clarified media was added to new BHK or C6/36 cells. 24 hrs after infection the media was replaced with fresh media containing10 ug/ml blasticidin and the cultures were maintained for an additional three weeks. Media was replaced every 3–4 days. GFP fluorescence was detected at 3 days post infection (panels B and E) and 3 weeks post infection (panels D and H).