Graft engineering using ex vivo methods to limit GVHD: Fludarabine treatment generates superior GVL effects in allogeneic BMT

Abstract

To compare the abilities of different ex vivo methods of treating donor lymphocytes to inhibit graft-vs-host disease (GVHD) while preserving graft-vs-leukemia (GVL) activity in murine models of allogeneic bone marrow transplantation. Donor/recipient pairs included MHC fully mismatched, MHC haplomismatched, and MiHA mismatched strain combinations. T cell-depleted BM (TCD-BM) was transplanted in combination with untreated, fludarabine-treated, 7.5-Gy gamma-irradiated, or psoralen/UVA (PUVA)-treated splenocytes. GVL activity was studied by adding a lethal number of recipient-type lymphoma cells. Posttransplant survival was determined, and GVHD and GVL activity were assessed by clinical and pathological scoring. Hematopoietic chimerism and donor T-cell expansion were analyzed by flow cytometry of peripheral blood samples at 30 and 60 days posttransplant. Allogeneic splenocytes treated with fludarabine, 7.5 Gy gamma-irradiation, or PUVA had significantly diminished GVHD activity, and all treated donor T cells facilitated engraftment by low-dose TCD-BM. Allogeneic splenocytes treated with fludarabine and, to a lesser extent, PUVA retained GVL activity and contributed more to donor T-cell chimerism compared to gamma-irradiated donor splenocytes. Among ex vivo methods of treating donor T cells to limit their proliferative capacity, fludarabine exposure had the greatest differential ability to inhibit the GVHD activity of allogeneic lymphocytes, while preserving their GVL activity and ability to engraft recipients. Thus, ex vivo treatment with fludarabine was superior to gamma-irradiation or PUVA in separating GVL from GVHD activity in murine models of allogeneic bone marrow transplantation.