Efficient transduction and selection of human T-lymphocytes with bicistronic Thy1/HSV1-TK retroviral vector produced by a human packaging cell line

Background: T-cells expressing the HSV1-TK suicide gene can be used for the control of graft-versus-host disease following allogeneic stem cell transplantation. To develop clinical trials based on such a strategy, we have generated under good manufacturing procedures a novel 'split genome' human packaging cell line (1704 cells).

Methods: To minimize the risk of generating replication-competent retroviruses, pol was truncated to remove sequences overlapping with env. To improve retroviral infection and selection of transduced T-cells, high titers of GALV-pseudotyped retroviral particles harboring a bicistronic Thy1-IRES-TK vector coding for the CD90 GPI-anchored membrane molecule were produced by 1704 cells.

Results: Using 1704 cell supernatant and an optimized transduction protocol, approximately 50% of primary T-cells were transduced and could then be purified (approximately 95%) using clinical-grade immunomagnetic beads directed against CD90. Over 96% of these OKT3/IL-2-activated CD90(+)-selected T-cells were killed by ganciclovir. Cell proliferation and cytokine production of transduced T-cells and HLA-restricted cytotoxicity of transduced T-cell clones were identical to those of their non-transduced counterparts cultured under the same conditions.

Conclusions: GALV-pseudotyped retroviral particles harboring a bicistronic Thy1-IRES-TK vector allow efficient transduction and rapid selection of human T-cells under conditions applicable for clinical trials using the new human 1704 packaging cell line.