Selective Modification of Antigen-Specific CD4+ T Cells by Retroviral-Mediated Gene Transfer and in Vitro Sensitization with Dendritic Cells

Adoptive therapy with antigen-specific T cells is a potential treatment against cancers and viral diseases. To establish a system to modify the genes of these cells to increase their effectiveness, we examined whether the combined use of retroviral vector, which only infects dividing cells, and in vitro sensitization of T cells with antigen-loaded dendritic cells (DCs) could selectively modify antigen-specific T cells with a bcl-2 gene. Human CD4+ T cells were used as target cells. Autologous DCs transfected with genes of hepatitis B virus (HBV) stimulated a specific T cell proliferation. Importantly, these proliferating T cells were selectively transduced by a bcl-2-retrovirus, and CD25+ T cells isolated from them contained higher levels of integrated provirus. To select bcl-2-transduced, activated T cells, cells were subjected to interleukin-2 (IL-2) withdrawal. In contrast to CD25− and mock-infected CD25+ T cells, 70% of CD25+ T cells transduced with bcl-2-retrovirus survived IL-2 withdrawal. These surviving T cells were demonstrated to contain integrated bcl-2 provirus and exhibited HBV-specific proliferation and interferon-γ secretion. In addition, bcl-2 overexpression protected HBV-specific T cells from transforming growth factor (TGF)-β-induced cell death. These results demonstrate the feasibility of our strategy in the generation of genetically modified antigen-specific CD4+ T cells and show that bcl-2-transduced antigen-specific T cells survive IL-2 withdrawal and TGF-β-induced apoptosis.