Alpha interferon (IFN‐α) gene transfer into hematopoietic stem cells

Gene transfer or gene therapy has advantages in the treatment of a variety of disorders due to its selective expression within specific mammalian cells. Interferon‐a (IFN‐α) has been used in the management of leukemia, but its diverse adverse activities with multiple potential side effects, possibly unrelated to therapeutic targets, may negatively influence the ability of IFN‐α to treat this disorder. Therefore, we examined the ability of adenovirus (Ad)IFN‐α gene construct to transfect normal (CD34 + cells) and chronic myelogenous leukemia (CML) bone marrow mononuclear cells (BMMNC) and the transient overexpression of IFN‐α in these cells. Ad‐cytomegalovirus (CMV) promoter‐driven IFN‐α (AdCMV‐IFN‐α) at multiple doses was assessed to transfect highly purified CD34 + cells in liquid culture, and optimal transduction of CD34 + cells was achieved using 120 plaque‐forming units. Flow cytometric determinations revealed that there was no significant difference in cell viability for the 4‐ or 24‐h transfection periods. Immunoassay of IFN‐α produced by CD34 + cells shows that IFN‐α levels increased several‐fold in transfected cells. Transient expression of the IFN‐α gene did not suppress proliferation of CD34 + progenitors as indicated by BFU‐E or colony‐forming units granulocyte, macrophage (CFU‐GM) growth. Reverse transcriptase/polymerase chain reaction analysis of RNA from CD34 + ‐harvested CFU‐GM progenitor cells demonstrated transient IFN‐α mRNA expression. Similarly, CML BMMNC were transfected with AdCMV‐IFN‐α under similar conditions as described for CD34 + cells. BMMNC exposed to adenovirus for 24‐ and 48 h were found to express IFN‐α at a substantial level. These in vitro data suggest that adenovirus‐mediated gene transfer of IFN‐α into hematopoietic stem cells can be achieved and that the IFN‐α gene can be translated into its specific mRNA in CD34 progenitor cells.