Murine acute graft-versus-host disease can be prevented by depletion of alloreactive T lymphocytes using activation-induced cell death

Abstract

Depletion of T lymphocytes from allogeneic bone marrow transplants successfully prevents the development of graftversus-host disease (GvHD) but is associated with impaired engraftment, immunosuppression, and abrogation of the graft-versus-leukemia effect. We therefore explored the possibility of selectively eliminating alloreactive T cells by CD95/ CD95L-mediated activation-induced cell death (AICD) in a major histocompatibility complex allogeneic murine model system. Activation of resting or preactivated T lymphocytes from C3H/HeJ (H-2 k ) mice was induced with irradiated BALB/cJ (H- 2 IntroductionGraft-versus-host disease (GvHD) represents a major complication of allogeneic bone marrow transplantation (BMT), which results in significant morbidity and mortality. Donor T lymphocytes present in the BM or peripheral blood stem cell transplant cause GvHD by recognizing major as well as minor histocompatibility antigens (reviewed by Ferrara et al 1 ). Although innovative strategies for the prediction, prevention, or treatment of this caveat in allogeneic BMT have been proposed, 2-9 prophylaxis or treatment of GvHD still remains unsatisfactory. Removal of donor-derived T lymphocytes prior to transplantation efficiently ameliorates GvHD. However, ex vivo depletion of T cells has been associated with an increased risk of viral opportunistic infections, 10 impaired engraftment, 11 and the loss of the graft-versus-leukemia (GvL) effect, resulting in an increased incidence of recurrence of leukemia. 12,13 These observations emphasize the clinical importance of allogeneic T cells in conferring a protective antiviral immunity as well as mediating a GvL effect. Several clinical and experimental studies support the idea that GvHD and GvL are not only mediated by the same (host-specific) T cell but also by distinct (leukemia-specific) alloreactive donor T-cell populations. 14-16 Moreover, allo-major histocompatibility complex (MHC)-restricted cytotoxic T lymphocytes (CTLs) to antigens frequently expressed at elevated levels on leukemic cells can be cloned from an allorestricted T-cell repertoire and used to mediate a GvL reaction without causing GvHD. [17][18][19] However, immunotherapy with ex vivo-generated specific T cells requires the identification and characterization of tumor-specific antigens to be targeted. To circumvent this prerequisite of cloning leukemia-specific T cells, we aimed to develop a complementing strategy that would allow ex vivo elimination of alloreactive T cells responsible for GvHD while preserving an allorestricted T-cell population able to both mediate GvL and antiviral immunity effects. Because the activation-induced cell death (AICD) mediated by CD95/CD95 ligand (CD95L) (reviewed by Lenardo et al 20 ) represents an important physiologic pathway to control the expansion of antigen-activated T cells at the down phase of an immune response, it therefore might provide a means to selectively deplete activated alloreactive T lymphocytes. Induction of AICD triggered by repetitive T-cell receptor (TCR...

“Pruning” of Alloreactive CD4+ T Cells Using 5- (and 6-)Carboxyfluorescein Diacetate Succinimidyl Ester Prolongs Skin Allograft Survival

“…Most have used modified MLCs and have included deletional Abs or immunotoxins against activation markers (32)(33)(34), enhancement of activation-induced cell death in the alloreactive population (35), magnetic bead sorting to remove cells expressing activation markers such as CD69 or CD25 (36 -38), cell sorting by flow cytometry based on cell size and activation markers (39), viral infection of stimulator cells to enhance activation in the MLC (40), and keratinocytes as stimulator cells (41). Most recently, the use of CFSE to remove alloreactive T cells has been shown in BMT to reduce GVHD (42).…”

Depletion of alloreactive T cells via CD69: implications on antiviral, antileukemic and immunoregulatory T lymphocytes

“…Several conceptually different strategies to selectively deplete alloreactive donor T lymphocytes either ex vivo, for example by photodynamic purging, 12 by CD95-mediated activation-induced apoptosis, 7 or in vivo by inducible 'suicide' genes expressed in genetically modified allogeneic T lymphocytes 13 have been proposed. Alternatively, numerous studies on the selective removal of alloreactive T cells based on their de novo expression of antigens upon activation such as CD25, [14][15][16][17] CD69, 18,19 or CD4 20 have been reported.…”

“…[3][4][5] However, alloreactive TCD are also central mediators of the graft-versus-host disease (GVHD), 6,7 which remains the major complication in AHSCT and thus limits its broader application. Nonselective depletion of TCD effectively controls GVHD, but simultaneously increases the risk for opportunistic infections and abolishes therapeutically desired alloreactivity against recurrent leukemia.…”

Selective elimination of alloreactivity in vitro and in vivo while sparing other T-cell-mediated immune responses

“…[10][11][12][13][14] The alloreactive T cells were sorted by means of (a) photosensitizing drugs, which can be preferentially incorporated and retained in activated T cells as opposed to resting T cells, 15,16 (b) specific monoclonal antibodies directed against activation markers such as CD25, CD69, CD40L, CD134 and CD137 that are differentially expressed on activated T cells [17][18][19][20][21][22][23][24] or (c) via activation-induced cell-mediated death by the CD95/ CD95L complex. 25,26 Throughout our attempts to develop selective elimination of alloreactive T cells, which would allow for safe engraftment of allogeneic hematopoietic cells while controlling GVHD, we applied a pharmacological approach using synthetic low molecular chemical compounds that were screened for their ability to affect T-cell proliferation in response to mitogenic and allogeneic stimuli. The most effective compound that led to selective elimination of allogeneic cells in vitro was a quinazoline derivative, AO#349, which was further tested in vivo in a murine experimental model of GVHD.…”