HUMAN HLA-SPECIFIC T-CELL CLONES WITH STABLE EXPRESSION OF A SUICIDE GENE - A POSSIBLE TOOL TO DRIVE AND CONTROL A GRAFT-VERSUS-HOST-GRAFT-VERSUS-LEUKEMIA REACTION

Allogeneic bone marrow transplantation is stilt limited by the morbidi ty and mortality caused by graft-versus-host disease (GVHD), resulting from host recognition by donor T lymphocytes. st is possible to drast ically reduce the T-cell content of the graft. However, transplanted T cells can also have a beneficial affect by graft enhancement and the graft-versus-leukemia effect. How can we keep the beneficial GVL effec t while protecting the patient from possible GVHD? A recent report pro posed the ex vivo transfer of the herpes simplex thymidine kinase (HSv -tk) gene into donor T cells before their infusion with hematopoietic stem cells, This procedure is expected to allow selective donor T-cell depletion with ganciclovir should GVHD occur, but it has two major dr awbacks: reinjection of a fraction of untransfected T cells cannot be avoided and heterogeneity of the transfected population results in inc reased risks such as HSv-tk gene instability or dysfunction of some of the transfected T cell. Alternative approaches must be considered. We demonstrate here the feasibility of generating HSv-tk transfected HLA -specific CD4+ cytotoxic T-cell clonal populations, in which 100% of t he cells have the HSv-tk gene inserted at a single site within their g enome. These clones retained their specificity, their function, and th eir sensitivity to ganciclovir treatment. Our approach is not limited to bone marrow transplantation. indeed, this procedure represents a us eful alternative to retroviral gene transduction and is applicable to every circumstance where clinical use of gene modified T-cell clones i s to be considered. (C) 1996 by The American Society of Hematology.