Retroviral packaging cell line and viral vector production.

Viral genes expressed from nonretroviral promoters are introduced into cells, where they are stably maintained and where they produce viral structural and enzymatic proteins. When a retroviral vector is introduced into the cell, viral vector RNA can be packaged, resulting in the production of virus particles containing the vector genome. This virus can be harvested and used to infect target cells to introduce the foreign gene on the vector into the cells. Because these target cells do not express viral proteins, the vector will not be propagated further. The viral genes in the packaging cells are not carried along with the vector because they lack the cis-acting sequences necessary for propagation.