Retroviruses are lipid-enveloped particles comprised of linear single-stranded RNA genomes of 7 to 11 kilo bases. The main features of retroviral vectors are reverse transcription of the viral RNA genome into DNA, and stable integration into the host DNA. Lentivirus is a genus of retroviruses. Example of lentivirus is human immunodeficiency virus (HIV).

Figure 1. Phylogeny of Retrovirus

At the end of all retroviral genomes there are two long terminal repeat (LTR) sequences. The LTR sequences become the border of the gag, pol and env genes. Lentivirus also encodes tat and rev. The function of each gene is as follows:

  • gag: structural protein

  • pol: nucleic acid polymerase/integrases

  • env: surface glycoprotein

  • tat: regulatory protein for gene expression

  • rev: regulatory protein accessory genes

Retrovirus are desirable gene delivery vehicles or vectors