Retroviral vectors have gained an increasing value in gene therapy because they stably deliver therapeutic genes to the host cell genome. These therapeutic genes are supposed to rectify consequences of inherited and acquired mutated genes in the host cell genome, or alter host cell function to cure diseases. In the following section we will discuss the biology and life cycle of retroviruses which starts with viral entry into the host cell, reverse transcription of viral RNA, nuclear import of the provirus, and finally integration of viral DNA into the cell host genome (Flint, Racaniello et al. 2004)
