Handicapped retroviral vectors efficiently transduce foreign genes into hematopoietic stem cells.

Retroviral vectors, designated handicapped, are described. These are genetically defective viruses that allow transfer of nonselectable genes under the transcriptional control of internal promoters. The basic handicapped vector (pHHAM) is derived from Harvey, Abelson, and Moloney murine retroviruses. It contains a 327-base-pair deletion in the 3' long terminal repeat that spans enhancer and promoter sequences. The deletion is successfully transferred to the 5' long terminal repeat after reverse transcription of viral RNA, yielding a provirus incapable of synthesizing viral transcripts. HHAM viruses containing the mouse c-myc gene under the control of immunoglobulin kappa chain gene regulatory elements, along with a selectable gene (neo) driven by a weak promoter (tk), were stably transmitted to cultured mouse B cells. The donor c-myc gene was transcribed from the kappa promoter in these cells. Helper-free virus-producing cell lines were generated at titers favorable for the efficient introduction of HHAM viruses, even without selection, into hematopoietic stem cells from mouse bone marrow. When returned to unirradiated congenic recipient mice, the cells were capable of long-term reconstitution of the myeloid and lymphoid lineages of W/Wv mutants and the lymphoid system of scid mutants.