Tissue-restricted T cell alloresponses across HLA barriers: selection and identification of leukemia-restricted CTL in HLA-mismatched stimulator–responder pairs

Abstract

Summary:Exploiting the graft-versus-leukemia (GVL) effect in mismatched transplants requires its separation from graftversus-host disease (GVHD). We generated leukemiaspecific cytotoxic T lymphocytes (CTL) in three haplotype-mismatched, two class I-mismatched and two single HLA-A locus-matched stimulator-responder pairs. Six patients with chronic myelogenous leukemia and one patient with acute myeloid leukemia transformed from MDS were studied. CTL generated after 10 days stimulation with unselected leukemic peripheral blood mononuclear cells inhibited leukemic CFU-GM colony growth (485% at 10:1 effector:target ratio) with no third-party colony inhibition. In five pairs, responders were cultured separately with leukemia cells, PHA-B or LCL from the stimulator. After 2-4 restimulations, the T cell repertoire was examined by flow analysis using Vb-specific antibodies. Test cultures (but not controls) showed preferential expansion of 1-4 Vb families either common to two or more stimulators or unique to a particular stimulator. Notably, we elicited leukemia-specific TCR Vb expansions on four out of five occasions. In two pairs, responder cells selected for the appropriate leukemia-specific Vb family were shown to have leukemia-specific cytotoxicity. These leukemia-restricted T-cells were CD8+ or CD4+ and CD25+ or CD57+. The results support the development of strategies to selectively deplete GVHD and conserve GVL reactivity in mismatched transplants. Bone Marrow Transplantation (2003) 32, 371-378. doi:10.1038/sj.bmt.1704142Keywords: leukemia-restriction; cytotoxic T-lymphocytes; HLA-mismatched; stem cell transplant The curative effect of allogeneic bone marrow transplantation (allo-BMT) from an HLA-identical donor is well established for a variety of hematological malignancies. Nevertheless, despite the increasing availability of unrelated donors, a suitable HLA-identical donor cannot be identified in a timely fashion for at least 50% of patients. 2,3Animal transplantation models indicate that powerful antitumor cytotoxic T lymphocyte (CTL) can be elicited in an MHC-mismatched setting.4,5 These observations support limited clinical experience in HLA-mismatched transplants indicating a strong graft-versus-leukemia (GVL) effect in high-risk patients with advanced leukemia and in leukemia relapsing after BMT treated with donor lymphocyte infusions.6-9 However, it is also clear that HLA disparity increases the risk of severe graft-versus-host disease (GVHD).10-12 As a result of the risk from GVHD, current HLA-mismatched transplant protocols use T cell depletion and potent immunosuppression to prevent GVHD, which in turn compromises the GVL effect. Separation of GVL alloresponses from the GVHD T cell alloresponse would permit the full exploitation of the therapeutic effect of the haplotype-mismatched transplant. Previous studies in HLA-matched transplants have defined an immunological basis for separating T cell clones with GVHD or GVL alloresponsiveness; while many alloantigens are shared between hematopoietic and nonhe...

Immune Reconstitution in Recipients of Photodepleted HLA-Identical Sibling Donor Stem Cell Transplantations: T Cell Subset Frequencies Predict Outcome

“…The possibility of preventing GVHD by selectively removing alloreactive T cells from the SCT product has for more than a decade stimulated us and numerous other investigators to develop selective allodepletion strategies 2, 4, 17 . Our most recent attempt using PD in the HLA-identical sibling transplant setting resulted in encouragingly low rates of acute GVHD and relapse, but was complicated by a high incidence of viral reactivation and high transplant related mortality, prompting early closure of the study 9 .…”

“…The GVHD alloresponse can be prevented or reduced in severity by post-transplant immune suppression and T cell depletion (TCD), but with a risk of impairing anti-viral and anti-tumor responses of the incoming donor immune system 1 . One approach to selectively reduce the risk of GVHD is to stimulate the donor lymphocyte product prior to transplantation with recipient antigen-presenting cells (APC), and then subsequently target and eliminate host-alloreactive T cells 2-5 . We recently conducted a clinical trial using a photodepletion (PD) technique to selectively deplete host-reacting T cells from HLA-matched sibling SCTs with the goal of reducing acute GVHD.…”

Matching for the MICA-129 polymorphism is beneficial in unrelated hematopoietic stem cell transplantation

“…14,28 Furthermore, MICA polymorphisms might lead to differences in the antigenic repertoires between donor and recipient in mismatched MICA allotypes. 27,29,30 …”

“…3 In a transplantation setting, MICA polymorphisms may influence alloreactivity of immune effector cells bearing the cognate receptor, leading to differences in relapse control. [25][26][27] In particular, the MICA-129 dimorphism (met/val) has been associated with differential binding affinity toward the NKG2D receptor. 28 It has been shown that this, in turn, leads to differences in downstream phosphorylation of SRC kinases.…”

Targeting T Cell Bioenergetics by Modulating P-Glycoprotein Selectively Depletes Alloreactive T Cells To Prevent Graft-versus-Host Disease

“…The goal of selective depletion is to prevent acute GVHD by removing only the GVHD-causing T cells from the graft prior to transplant. Pre-clinical experiments demonstrate that when GVHD-causing cells are selectively eliminated, healthy lymphocytes remain that may mediate anti-leukemia, antiviral, and antifungal immune responses (6, 7). This technique requires the co-culturing of leukemia-free, patient-derived antigen presenting cells with donor lymphocytes.…”