integrase-deficient lentivirus, non-integrating lentivirus, lentiviral packaging system, lentiviral packaging mix, lentiviral packaging plasmids
The integrase-deficient version of Clontech's 4th generation Lenti-X HTX Packaging System consists of 5 separate components (Panel C), mixed in proprietary proportions for optimized packaging performance. A mutation within the integrase reduces the integration efficiency of transduced virus resulting in transient expression in dividing cells (compare Panel A to Panel C). The separation of the gag, pol, and env genes effectively reduces the incidence of RCL (Wu et al. 2000; Mol. Ther. 2:47–55). High levels of expression of essential viral components are driven by the Tet-Off and Tat transactivators, a cascade of expression resulting in high titers of lentivirus. The pol gene is fused to vpr to ensure transport of the Pol protein into the recombinant lentiviral particle. Not all vector elements are shown. 3rd generation lentiviral packaging systems (Panel B) generate lower titers, do not contain separate gag and pol sequences and do not use a transactivation cascade mechanism.