Methods and compositions are provided for delivering a polynucleotide encoding agene of interest to a target cell using a virus. The virus envelope comprises acell-specific binding determinant that recognizes and binds to a component onthe target cell surface, leading to endocytosis of the virus. A separate fusogenic moleculeis also present on the envelope and facilitates delivery of the polynucleotide acrossthe membrane and into the cytosol of the target cell. The methods and related compositionscan be used for treating patients having suffering from a wide range of conditions,including infection, such as HIV； cancers, such as non-Hodgkin's lymphomaand breast cancer； and hematological disorders, such as severe combined immunodeficiency.
