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Table 15.1 Different genes of lentivirus and their functions:

Figure 15.1 Schematic diagram of lentivirus:

Gene therapy vectors based on lentiviruses lack all the viral sequences except the LTRs, rev responsive element (RRE), and cis -acting elements. Usually viral rev proteins are added in trans in order to facilitate the trafficking of viral RNA genome in the nucleus following efficient binding with RRE. The production of vector RNA is either directed by LTRs or by tissue specific promoter. Generally vectors are designed in such a way so as to utilize tissue specific promoter (CMV) and LTR hybrid promoter (CMV/LTR). The use of CMV/LTR hybrid promoter allows abundant vector RNA production independent of transactivation by tat protein. HIV accessory proteins, vif, vpr, nef, and vpu can be deleted during the lentiviral production. Sometimes polypurine tract present in the HIV genome can be included as a cis - active element during the viral production in order to enhance the nuclear trafficking. The HIV-1 infects only the cells that contain CD4 receptor and co-receptors such as CXCR4 and CCR5.The attachment of HIV to the receptor and co-receptors is largely mediated by viral glycoproteins. This specificity restricts the host range for HIV-1 infection. Scientists worldwide are trying to broaden the host range by various molecular biology techniques. One such technique is to generate a pseudo type HIV virus that contains vesicular stomatitis glycoprotein along with env protein, which is having broad tropism.