YFV antigen expression from a non-purified virus stock. Western blot analysis of yellow fever prME protein expression was performed at different passages of an unselected rMVA-YF/D4 stock, using a polyclonal anti YFV guinea pig serum that detects the YFV E protein as a ~50 kDa band. The blot shows the primary virus crude stock following infection of DF-1 cells with dMVA-ZG and transfection with pDM-D4R/YF (lane 2), and harvest from the first (lane 3), the second (lane 4) and the third passage (lane 5) of this stock. In parallel, the plasmid pd3-YFprMEco that lacks the D4R gene was transfected into dMVA-ZG infected DF-1 cells (lane 6) and passaged once (lane 7). As a positive control, clonally purified rMVA-YF/del3 was used (lane 8). Uninfected cells are shown on lane 9.