How the Retro-X Universal Packaging System works

Retroviral gene transfer systems depend on packaging cell lines to supply necessary viral structural proteins. The provided GP2-293 cell line contains the Moloney Murine Leukemia Virus (MMLV) gag and pol genes stably integrated into its genome. Simply transfect GP2-293 cells with the retroviral vector and the appropriate viral envelope vector, wait 48 hours, and then collect your viral supernatant which is ready for transduction (Figure 1).

Figure 1. The Retro-X Universal Packaging System. The system consists of the GP2-293 Packaging Cell Line, which expresses viral Gag and Pol proteins, and a set of 4 viral envelope expression vectors. Cotransfecting an envelope vector with your retroviral construct allows you to select the ideal tropism for your virus.

Produce high titer retrovirus for your cell type

Broad tropism—infect all your cells

Viral envelopes are classified by the receptors they use to enter host cells. For example, ecotropic viruses are recognized by receptors only found on mouse and rat cells. The universal packaging system includes four envelope expression vectors—ecotropic, amphotropic, dualtropic (10A1), and pantropic (VSV-G)—allowing you to select the most appropriate envelope protein to infect your cell type (Table 1).

Obtain high titers of retroviral particles

The included cell line, GP2-293, has been optimized for the production of high-titer retrovirus packaged in any of the four envelope proteins (Figure 2). Rapid and easy determination of retroviral titer may be achieved using the Retro-X qRT-PCR Titration Kit (sold separately). If desired, retroviral supernatants are easily concentrated with the Retro-X Concentrator (not shown).

Figure 2. High-titer retroviral packaging in GP2-293 cells. Cells were transfected with a retroviral vector expressing the red fluorescent protein DsRed2, and each of the four envelope vectors supplied with the Retro-X Universal Packaging System (Panels A–D). After incubating the transfected GP2-293 cells for 48 hr, 10 μl of the resulting virus was used to infect NIH 3T3 cells. After 48 hours, titers were measured by flow cytometry. Panel A. Ecotropic envelope. Panel B. Amphotropic envelope. Panel C. 10A1 envelope. Panel D. VSV-G envelope. Positive cells are indicated by the blue-filled line. Negative control cells are indicated by the purple line.

The Retro-X Universal Packaging System provides a rapid and convenient method for producing high titers of replication-incompetent retrovirus. It includes four envelope expression vectors—ecotropic, amphotropic, dualtropic (10A1), and pantropic (VSV-G)—allowing you to select the most appropriate envelope protein to infect your cell type.