Packaging Cells

The following packaging cell lines express Gag-Pol proteins from Moloney murine leukemia virus (Moloney MLV) and Env proteins from a variety of viruses. All were made using NIH 3T3 TK- mouse cells. The cell lines are named based on the virus origin of the Env protein, for example, PA317 refers to a Packaging cell line expressing an Amphotropic murine retrovirus Env protein. Early packaging cell designs used one plasmid to express the viral proteins, while later designs express the Gag-Pol and Env proteins from different independently-transfected plasmids. The latter strategy for packaging cell line construction, also referred to as "split genome", reduces the potential for generation of replication-competent virus.

PA12 - An early high-titer amphotropic packaging cell line made by transfection of a single plasmid encoding all viral proteins. The Env protein is derived from amphotropic MLV strain 4070A which confers a wide host range to vectors made using this cell line. Reference

PE501 - An early high-titer ecotropic packaging cell line made by transfection of a single plasmid encoding all viral proteins. The Env protein is derived from Moloney MLV. Vectors made from these cells transduce rodent cells only, and not human cells. Reference.

PA317 - A high-titer amphotropic packaging cell line widely used in research and in human gene therapy trials. Made using a single plasmid encoding all viral proteins that had multiple deletions of viral signals required for replication to reduce the potential for production of replication-competent virus. Proper choice of a retroviral vector to avoid overlap of vector sequences with viral DNA sequences present in PA317 cells generally prevents the production of replication-competent virus from these cells. Indeed, PA317 cells that produce a vector encoding the herpes simplex virus thymidine kinase gene have been injected into the brains of over 170 patients with glioblastoma in phase II and phase III clinical trials with no evidence for the production of replication-competent virus (see Shand et al. below). Reference, Source

Examples of clinical gene therapy applications =

Rosenberg et al., N Engl J Med 323:570-578, 1990 Abstract

Blaese et al., Science 270:475-480, 1995 Abstract

PG13 - A high-titer packaging cell line that expresses the Env protein from gibbon ape leukemia virus (GALV). Split genome design. Particularly useful for transduction of hematopoietic cells. Vectors produced have a wide host range but cannot transduce mouse cells, preventing vector reinfection of these mouse cell-derived packaging cells. Reference , Source (No Vector), Source (LN Vector)

PT67 - A high-titer 10A1 amphotropic MLV-based packaging cell line. Can use both Pit1 and Pit2 cell-surface receptors, while standard amphotropic vectors use only Pit2, and GALV vectors use only Pit1. Split genome design. A good choice for human gene therapy in comparison to PA317 cells, although PT67 cells have not been tested as extensively as PA317 cells in human clinical trials to date. Reference, Source

PD223 - Packaging cells expressing the Env protein from Mus dunni endogenous virus (MDEV). Split genome design. Useful for efficient transduction of hamster cells, including CHO cells, and for transduction of hematopoietic cells. Reference

PJ14 - Packaging cells expressing the Env protein from jaagsiekte sheep retrovirus (JSRV). Split genome design. Recognizes the glycosylphosphatidylinositol (GPI)-anchored receptor Hyal2. Reference.