Figure 5-1.4.4(e): Propagation of retroviral vectors in helper cells.

(Adapted from Hu W-S, Pathak VK. 2000. Design of Retroviral Vectors and Helper Cells for Gene Therapy. Pharmacol Rev, 52: 493–511)

Figure 5-1.4.4(f): cis -acting elements required by a prototypical retroviral vector. The plasmid backbone contains a bacterial origin of replication (ori) and a drug resistance gene.

(Adapted from Hu W-S, Pathak VK. 2000. Design of Retroviral Vectors and Helper Cells for Gene Therapy. Pharmacol Rev, 52: 493–511.).

Advantages

•  Well studied system having high transduction efficiency

•  Insert size up to 8 kb

•  Integration into host genome resulting in sustained expression of the vector

•  Vector proteins are not expressed in host

Disadvantages

•  Infection by retrovirus requires dividing cells

•  Low titres (10⁶ -10⁷)

•  Random integration

•  Poor in vivo delivery