Retroviral vectors and gene therapy: An update

Gene therapy aims at treatment of diseases by transfer of genetic material into specific cells of a patient. So the transduction of appropriate target cell is critical. Retroviruses infect nearly every cell in the target population and become integrated in host cell genome for a stable expression. All retroviruses have only three structural genes gag, pol and env, except for lentiviruses where two other genes tat, rev and four accessory genes are required (vif, vpu, nif, vpr). There are two components of retroviral vector system—i) Packaging cell lines, which provide the products of gag, pol & env genes but are unable to package itself as they lack the ψ sequence, and ii) retroviral vectors where gag, pol and env are deleted but ψ sequence along with LTR is present. Several other types of vectors are also described.