title: CTLA-4 blockade following relapse of malignancy after allogeneic stem cell transplantation is associated with T cell activation but not with increased levels of T regulatory cells.
abstract: Cytotoxic T lymphocyte-associated antigen 4 (CTLA-4) is a key negative regulator of T cell activation and proliferation. Ipilimumab is a human monoclonal antibody that specifically blocks the binding of CTLA-4 to its ligand. To test the hypothesis that blockade of CTLA-4 by ipilimumab could augment graft-versus-malignancy (GVM) effects without a significant impact on graft-versus-host disease (GVHD), we conducted a phase I clinical trial of ipilimumab infusion in patients with relapsed malignancy following allogeneic hematopoietic stem cell transplantation (allo-HSCT). Here, we report the analysis of peripheral blood T lymphocyte reconstitution, T regulatory cell (Treg) expression, and T cell activation markers after a single dose of ipilimumab in 29 patients. Peripheral blood samples were collected from all patients before and after ipilimumab infusion. Lymphocyte immunophenotyes, including levels of CD4(+)CD25(high) cells and T cell activation markers, were analyzed in all cases. Levels of CD4(+)CD25(high)Foxp3(+) cells and intracellular CTLA-4 in CD4(+) T cells also were evaluated in the last 11 cases. We found lower baseline levels of CD4(+) and CD45RO(+) T cells in patients compared with normal controls. More than 50% of the patients had abnormally low lymphocyte counts (CD4 or/and CD8 T cells), and some had no circulating B lymphocytes. The percentages of both CD4(+)CD25(high) and CD4(+)CD25(high)Foxp3(+) T cells were significantly higher in patients before ipilimumab infusion than in healthy donors. Twenty of 29 patients exhibited an elevated level of CD4(+)CD25(low) activated T cells at baseline, compared with only 3 of 26 healthy donors. Both CD4(+) and CD8(+) T lymphocyte counts were significantly increased after ipilimumab infusion. There was no consistent change in absolute lymphocyte count or in the number of T cells expressing the activation marker CD69. However, increases in CD4(+)CD25(low) T cells were seen in 20 of 29 patients and increases in CD4(+)HLA-DR(+) T cells were seen in the last 10 patients in the first 60 days after ipilimumab infusion. Although the percentages of both CD4(+)CD25(high) and CD4(+)CD25(high)Foxp3(+) T cells decreased significantly during the observation period, the absolute cell counts did not change. Intracellular CTLA-4 expression in CD4(+)CD25(lo/-) T cells increased significantly after ipilimumab infusion. We conclude that CTLA-4 blockade by a single infusion of ipilimumab increased CD4(+) and CD4(+)HLA-DR(+) T lymphocyte counts and intracellular CTLA-4 expression at the highest dose level. There was no significant change in Treg cell numbers after ipilimumab infusion. These data demonstrate that significant changes in T cell populations occur on exposure to a single dose of ipilimumab. Further studies with multiple doses are needed to explore this phenomenon further and to correlate changes in lymphocyte subpopulations with clinical events.
authors: Moores Cancer Center, University of California San Diego, La Jolla, California, USA.
authors: Jiehua
authors: J
authors: Zhou
authors: Asad
authors: A
authors: Bashey
authors: Ruikun
authors: R
authors: Zhong
authors: Sue
authors: S
authors: Corringham
authors: Karen
authors: K
authors: Messer
authors: Minya
authors: M
authors: Pu
authors: Wenxue
authors: W
authors: Ma
authors: Theresa
authors: T
authors: Chut
authors: Robert
authors: R
authors: Soiffer
authors: Rachel C
authors: RC
authors: Mitrovich
authors: Israel
authors: I
authors: Lowy
authors: Edward D
authors: ED
authors: Ball
mesh_terms: D000911:Antibodies, Monoclonal / Q000008:administration & dosage* / Q000378:metabolism / Q000627:therapeutic use; D015703:Antigens, CD / Q000032:analysis / Q000276:immunology / Q000378:metabolism; D000945:Antigens, Differentiation, T-Lymphocyte / Q000032:analysis; D001943:Breast Neoplasms / Q000276:immunology* / Q000503:physiopathology / Q000517:prevention & control / Q000628:therapy; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D060908:CTLA-4 Antigen; D016022:Case-Control Studies; D002452:Cell Count; D005260:Female; D005434:Flow Cytometry; D006086:Graft vs Host Disease / Q000276:immunology; D020350:Graft vs Tumor Effect / Q000187:drug effects; D018380:Hematopoietic Stem Cell Transplantation / Q000009:adverse effects; D006801:Humans; D007275:Injections, Intravenous; D053645:Interleukin-2 Receptor alpha Subunit / Q000032:analysis; D000074324:Ipilimumab; D037181:Lectins, C-Type / Q000032:analysis; D007938:Leukemia / Q000276:immunology* / Q000503:physiopathology / Q000517:prevention & control / Q000628:therapy; D017493:Leukocyte Common Antigens / Q000032:analysis; D008213:Lymphocyte Activation / Q000276:immunology; D008232:Lymphoproliferative Disorders / Q000276:immunology* / Q000503:physiopathology / Q000517:prevention & control / Q000628:therapy; D008297:Male; D012008:Recurrence; D050378:T-Lymphocytes, Regulatory / Q000276:immunology*; D014184:Transplantation, Homologous; D000099192:CD69 Antigens
chemical_list: D000911:Antibodies, Monoclonal; D015703:Antigens, CD; D000945:Antigens, Differentiation, T-Lymphocyte; D060908:CTLA-4 Antigen; D053645:Interleukin-2 Receptor alpha Subunit; D000074324:Ipilimumab; D037181:Lectins, C-Type; D017493:Leukocyte Common Antigens; D000099192:CD69 Antigens; C556706:CTLA4 protein, human