Adenovirus-Mediated Transfer of the Amphotropic Retrovirus Receptor cDNA Increases Retroviral Transduction in Cultured Cells

The presence of functional amphotropic receptors on the cell surface is necessary for amphotropic retrovirus-mediated gene transfer. A recombinant adenoviral vector that expresses the receptor for amphotropic retrovirus (RAM) was constructed and used to express the receptor cDNA in different cell types in culture. Transfer of the RAM cDNA increased amphotropic retroviral-mediated transfer from 0 to 60% in Chinese hamster ovary cells. RAM expression increased retroviral transduction four- to eight-fold from 2–4% to 18%–35% in HeLa, Namalva, and X63 cells, but had no effect on 208F and HepG2 cells which have high baseline retroviral transduction rates of about 50%. For the purpose of application to ex vivo gene therapy, primary mouse hepatocytes were studied in a similar manner. Hepatocytes had a baseline transduction efficiency of about 40% and did not have increased rates of retroviral-mediated gene transfer with expression of recombinant RAM. This recombinant adenoviral vector conferred infection of amphotropic retrovirus into cells that were relatively resistant to infection, thus offering a rapid and easy method to stably introduce genes into these cell lines. A recombinant adenoviral vector that contains the rat amphotropic cDNA was used to increase retroviral-mediated gene transfer in cell lines normally resistant to amphotropic retroviral infection. This allows for the rapid production of stable genetically modified cells in culture. This strategy may ultimately be useful for obtaining higher levels of permanent gene transfer in tissues that are normally resistant to retroviral-mediated gene transfer. The use of two different vector systems to improve upon gene transfer and expression in primary cells may have general applications in gene therapy.