This invention relates to a novel gammaretroviral vector packaging cell line and a method of producing gammaretroviral vectors suitable for gene therapy. The described vectors may contain the gibbon ape leukemia virus (GALV) envelope with a CD11D8 epitope tag enabling their purification on a monoclonal antibody conjugated column. These vectors have several advantages over existing systems, including a broader host range, higher infectivity, and lower potential for replication. Further, purification of retroviral vector particles via an epitope tag may remove cellular components and debris toxic to target cells and tissues, providing a safer method of delivery for patients receiving gene therapy.