Retroviral Vector

The virus is a desirable gene delivery vehicles or vectors because of its capacity to efficiently carry and deliver foreign genes to achieve stable gene expression,

The most commonly used vectors are developed from retroviruses, the adenovirus, the herpes simplex virus (HSV), and the adeno-associated virus (AAV). Among virus types that are generally used in clinical gene therapy, the retrovirus is the leading delivery system due to its efficiency.

Four steps for gene transfer using lentivirus. First, there is a transfection of the lentivirus vector into the packaging cell. After that, the retrovirus particle is formed and now carries the gene. The third step is the transduction of the target cell, like a fibroblast cell. Finally, the transcription factor is expressed by the cell.

Figure 1: Gene transfer using lentivirus

In order to increase vector biosafety, the retroviral vector gene is modified by removing up to six genes essential for HIV replication and pathogenesis. The overall principle of lentivirus vector gene transfer is described as follows:

  • The genes that encode the structural protein (gag, pol and env) are deleted from the virus vector (plasmid).

  • The virus vector carries the gene of interest/ foreign gene and psi packaging

  • The virus vector is cotransfected with packaging plasmids that carry the viral structural genes to the 293FT packaging cell line.

  • The recombinant lentivirus is produced in the 293FT cell line before it is extracted.

  • The recombinant lentivirus particle is transduced into target cells, where reverse transcription, foreign gene integration, and foreign gene ectopic expression take place.

Advantage of retroviral vector