Schematic representation of the gene-transfer vectors pHR-CD80, pHR-GM-CSF, and PHR-GM/CD.

The long terminal repeats (LTR), the splice donor site (SD), the splice acceptor site (SA), the packaging signal, the cytomegalovirus (CMV) enhancer-promoter element, and the truncated and out-of-framegag gene (Ga) upstream of the Rev responsive element (RRE) are indicated (not in scale). The complementary DNA encoding human CD80 and human granulocyte-macrophage colony-stimulating factor (GM-CSF) are shown. To construct pHR-GM/CD, a bicistronic message was generated; this contained an internal ribosome entry site (IRES) upstream of the human CD80 open-reading frame. Some of the cleavage sites for restriction enzymes used for the design or verification of the constructs are shown.