Outline of the D4R-dominant host range selection system. a. Schematic representation of the plasmid pDM-Zgpt for the construction of the D4R-deleted dMVA-ZG, and the corresponding insertion locus in the genome of MVA. b. Plasmid pDM-D4R-YF and the defective parental virus dMVA-ZG. MVA sequences are represented by boxes. The MVA genes D3R, D4R, D5R are marked grey. Foreign genes cassettes inserted into MVA are symbolized by hatched boxes. Arrows indicate the binding sites of the PCR primers that were used for confirmation of the structure and purity of dMVA-ZG.