What is the difference between 2nd generation and 3rd generation lentiviral systems?
For a full description of 2nd and 3rd generation lentiviruses please see the page on packaging plasmids. Briefly, 2nd generation lentiviral systems use more HIV proteins (on fewer plasmids) in order to produce functional lentiviral particles than 3rd generation systems. • 2nd generation packaging systems – express the HIV gag, pol, rev, and tat genes all from a single packaging vector such as psPAX2 • 3rd generation packaging systems – express gag and pol from one packaging vector and rev from another, such as pMDLg/pRRE and pRSV-Rev. 3rd generation packaging systems DO NOT express tat. 3rd generation lentiviral systems are considered safer than second generation systems, but are more difficult to use because they require transfection with four separate vectors in order to create functional lentiviral particles. IMPORTANT: A 3rd generation transfer vector can be used with a 2nd generation packaging system, but a 2nd generation transfer vector cannot be used with a 3rd generation packag
