Figure 15.2 Generation of lentiviral vector:

Diagram depicts a HIV based vector system where viral essential genes have been replaced by the transgene. Cytomegalovirus promoter is used to transcribe the transgene as well as gag, RRE, and cPPT. RRE acts a cis -acting sequence essential for nuclear export of viral RNA while polypurine tract (cPPT) helps in the import of proviral DNA. The deletion in U3 region in the genome makes it inaccessible to use LTR for transcription. The packaging system consists of gag / pol , VSV-G, and rev expressing constructs. Presence of RRE along with gag / pol helps in nuclear export of the RNA by transcribing rev protein. Lentiviral vectors are produced by transfection of vector construct along with the packaging constructs in producer cells. Vector RNA genomes are packaged by precursor proteins at the cellular membrane. The mature particles bud through the cellular membrane, containing the envelope derived from VSV-G glycoproteins.