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To reduce the risk of graft-versus-host disease (GVHD) after allogeneic stem cell transplantation (alloSCT), T-cell depletion (TCD) of grafts can be performed by the addition of alemtuzumab (ALT) "to the bag" (in vitro) before transplantation. In this prospective study, the authors analyzed the effect of in vitro incubation with 20 mg ALT on the composition of grafts prior to graft infusion. Furthermore, the authors assessed whether graft composition at the moment of infusion was predictive for T-cell reconstitution and development of GVHD early after TCD alloSCT. Sixty granulocyte colony-stimulating factor-mobilized stem cell grafts were obtained from ≥9/10 HLA-matched related and unrelated donors. The composition of the grafts was analyzed by flow cytometry before and after in vitro incubation with ALT. T-cell reconstitution and incidence of severe GVHD were monitored until 12 weeks after transplantation. In vitro incubation of grafts with 20 mg ALT resulted in an initial median depletion efficiency of T-cell receptor (TCR) α/β T cells of 96.7% (range, 63.5–99.8%), followed by subsequent depletion in vivo. Graft volumes and absolute leukocyte counts of grafts before the addition of ALT were not predictive for the efficiency of TCR α/β T-cell depletion. CD4pos T cells were depleted more efficiently than CD8pos T cells, and naive and regulatory T cells were depleted more efficiently than memory and effector T cells. This differential depletion of T-cell subsets was in line with their reported differential CD52 expression. In vitro depletion efficiencies and absolute numbers of (naive) TCR α/β T cells in the grafts after ALT incubation were not predictive for T-cell reconstitution or development of GVHD post- alloSCT. The addition of ALT to the bag is an easy, fast and generally applicable strategy to prevent GVHD in patients receiving alloSCT after myeloablative or non-myeloablative conditioning because of the efficient differential depletion of donor-derived lymphocytes and T cells. [ABSTRACT FROM AUTHOR]

The most frequent subtype of acute myeloid leukemia (AML) is defined by mutations in the nucleophosmin 1 (NPM1) gene. Mutated NPM1 (ΔNPM1) is an attractive target for immunotherapy, since it is an essential driver gene and 4 bp frameshift insertions occur in the same hotspot in 30%-35% of AMLs, resulting in a C-terminal alternative reading frame of 11 aa. By searching the HLA class I ligandome of primary AMLs, we identified multiple ΔNPM1-derived peptides. For one of these peptides, HLA-A*02:01-binding CLAVEEVSL, we searched for specific T cells in healthy individuals using peptide-HLA tetramers. Tetramer-positive CD8+ T cells were isolated and analyzed for reactivity against primary AMLs. From one clone with superior antitumor reactivity, we isolated the T cell receptor (TCR) and demonstrated specific recognition and lysis of HLA-A*02:01-positive ΔNPM1 AML after retroviral transfer to CD8+ and CD4+ T cells. Antitumor efficacy of TCR-transduced T cells was confirmed in immunodeficient mice engrafted with a human AML cell line expressing ΔNPM1. In conclusion, the data show that ΔNPM1-derived peptides are presented on AML and that CLAVEEVSL is a neoantigen that can be efficiently targeted on AML by ΔNPM1 TCR gene transfer. Immunotherapy targeting ΔNPM1 may therefore contribute to treatment of AML. [ABSTRACT FROM AUTHOR]

Alemtuzumab (ALM) is used for T cell depletion in the context of allogeneic hematopoietic stem cell transplantation (alloSCT) to prevent acute graft-versus-host disease and graft rejection. Following ALM-based T cell-depleted alloSCT, relatively rapid recovery of circulating T cells has been described, including T cells that lack membrane expression of the GPI-anchored ALM target Ag CD52. We show, in a cohort of 89 human recipients of an ALM-based T cell-depleted alloSCT graft, that early lymphocyte reconstitution always coincided with the presence of large populations of T cells lacking CD52 membrane expression. In contrast, loss of CD52 expression was not overt within B cells or NK cells. We show that loss of CD52 expression from the T cell membrane resulted from loss of GPI anchor expression caused by a highly polyclonal mutational landscape in the PIGA gene. This polyclonal mutational landscape in the PIGA gene was also found in CD52- T cells present at a low frequency in peripheral blood of healthy donors. Finally, we demonstrate that the GPI-/CD52- T cell populations that arise after ALM-based T cell-depleted alloSCT contain functional T cells directed against multiple viral targets that can play an important role in immune protection early after ALM-based T cell-depleted transplantation. [ABSTRACT FROM AUTHOR]

Patients with leukemia who receive a T cell-depleted allogeneic stem cell graft followed by postponed donor lymphocyte infusion (DLI) can experience graft-versus-leukemia (GVL) reactivity, with a lower risk of graft-versus-host disease (GVHD). Here, we have investigated the magnitude, diversity, and specificity of alloreactive CD8 T cells in patients who developed GVL reactivity after DLI in the absence or presence of GVHD. We observed a lower magnitude and diversity of CD8 T cells for minor histocompatibility antigens (MiHAs) in patients with selective GVL reactivity without GVHD. Furthermore, we demonstrated that MiHA-specific T cell clones from patients with selective GVL reactivity showed lower reactivity against nonhematopoietic cells, even when pretreated with inflammatory cytokines. Expression analysis of MiHA-encoding genes showed that similar types of antigens were recognized in both patient groups, but in patients who developed GVHD, T cell reactivity was skewed to target broadly expressed MiHAs. As an inflammatory environment can render nonhematopoietic cells susceptible to T cell recognition, prevention of such circumstances favors induction of selective GVL reactivity without development of GVHD. [ABSTRACT FROM AUTHOR]

The immune cell composition of the follicular lymphoma (FL) tumor microenvironment is increasingly recognized as an important determinant for clinical outcome. Here, we explored frequency and distribution of dendritic cell (DC) subtypes in relation to regulatory T cells (Treg) by immunohistochemistry in lymph node biopsies from patients withde novoFL. We found that neoplastic follicles contained lower DC and higher Treg frequencies than hyperplastic follicles in control lymph nodes. Treg numbers particularly correlated with the subset of conventional CD11c+ DCs. Additionally, both a high intra- to interfollicular ratio of CD11c+ DCs and increased intrafollicular Treg frequencies were associated with decreased overall survival. This suggests that functional interactions between these cells may be relevant for FL progression/recurrence. The presence of CD11c+ DCs in the tumor microenvironment may assist tumor infiltration by Tregs, thus contributing to the suppression of an otherwise beneficial T-cell-dominated FL microenvironment. [ABSTRACT FROM AUTHOR]

Induction of tumor-antigen-specific T cells in active cancer immunotherapy is generally difficult due to the very low anti-tumoral precursor cytotoxic T cells. By improving tumor-antigen uptake and presentation by dendritic cells (DCs), this problem can be overcome. Focusing on MAGE-A3 protein, frequently expressed in many types of tumors, we analyzed different DC-uptake routes after additional coating the recombinant MAGE-A3 protein with either a specific monoclonal antibody or an immune complex formulation. Opsonization of the protein with antibody resulted in increased DC-uptake compared to the uncoated rhMAGE-A3 protein. This was partly due to Fcγ receptor-dependent internalization. However, unspecific antigen internalization via macropinocytosis also played a role. When analyzing DC-uptake of MAGE-A3 antigen expressed in multiple myeloma cell line U266, pretreatment with proteasome inhibitor bortezomib resulted in increased apoptosis compared to γ-irradiation. Bortezomib-mediated immunogenic apoptosis, characterized by elevated surface expression of hsp90, triggered higher phagocytosis of U266 cells by DCs involving specific DC-derived receptors. We further investigated the impact of antigen delivery on T-cell priming. Induction of CD8 T-cell response was favored by stimulating naïve T cells with either antibody-opsonized MAGE-A3 protein or with the bortezomib-pretreated U266 cells, indicating that receptor-mediated uptake favors cross-presentation of antigens. In contrast, CD4 T cells were preferentially induced after stimulation with the uncoated protein or protein in the immune complex, both antigen formulations were preferentially internalized by DCs via macropinocytosis. In summary, receptor-mediated DC-uptake mechanisms favored the induction of CD8 T cells, relevant for clinical anti-tumor response. [ABSTRACT FROM AUTHOR]

The idiotypes of B cell lymphomas represent tumor-specific antigens. T cell responses induced by idiotype vaccination in vivo are directed predominantly against CDR peptides, whereas in vitro T cells also recognize framework-derived epitopes. To investigate the mechanisms regulating the specificity of idiotype-specific T cells, BALB/c or B10.D2 mice were immunized with mature dendritic cells loaded with H-2K-restricted peptides from influenza hemagglutinin, or from shared (J region) or unique (CDR3) structures of the A20 lymphoma idiotype. Antigen-specific T cells were induced in vivo by the CDR3 and influenza epitopes, but not by the J peptide. Gene expression profiling of splenic regulatory T cells revealed vaccination-induced Treg activation and proliferation. Treg activity involved J epitope-dependent IL-10 secretion and functional suppression of peptide-specific effector T cells. Vaccination-induced in vivo proliferation of transgenic hemagglutinin-specific T cells was suppressed by co-immunization with the J peptide and was restored in CD25-depleted animals. In conclusion, Treg induced by a shared idiotype epitope can systemically suppress T cell responses against idiotype-derived and immunodominant foreign epitopes in vivo. The results imply that tumor vaccines should avoid epitopes expressed by normal cells in the draining lymph node to achieve optimal anti-tumor efficacy. [ABSTRACT FROM AUTHOR]

Despite improvements in HLA typing, graft-versus-host disease (GVHD) continues to impair the results after volunteer unrelated donor bone marrow transplantation (VUD-BMT) in adult patients compared with matched sibling BMT. Here, the outcome after VUD-BMT using a specific regimen with high-dose anti-T-lymphocyte globulin (ATG) was analysed. Fifty-five adult patients, median age 34 years (range 17–55 years), with acute or chronic leukaemia or myelodysplastic syndrome (MDS) were transplanted in first complete remission (CR1)/first chronic phase (CP1) (early disease) (n = 21) or in advanced (CR2/CP2, no remission) disease (n = 34) from an unrelated marrow donor. GVHD prophylaxis consisted of ATG-S (Fresenius) 60–90 mg/kg b.w. prior to transplantation, in addition to cyclosporin A and short-course methotrexate. Graft failure did not occur and white blood cell count (WBC) > 1·0 × 109/l was reached at median day +16. The cumulative incidence of acute (a)GVHD grade II–IV was 15% [95% CI (8%, 28%)] and of chronic GVHD was 51% [95% CI (38%, 68%)]. The cumulative incidence of relapse within 1 year was 0% [95% CI (0%, 19%)] and 21% [95% CI (11%, 40%)] for patients with early and advanced disease respectively. With a median follow-up of 28 months (range 16–45 months), 2-year disease-free and overall survival for patients transplanted in CR1/CP1 was 81% and 81% [95% CI (64%, 98%)], respectively, and for patients with advanced disease was 33% [95% CI (17%, 50%)] and 40% [95% CI (23%, 57%)] respectively. Complete and persistent donor chimaerism was seen in 77·5% of 40 patients evaluated. All 14 chronic myeloid leukaemia (CML)-CP1 patients became bcr–abl negative within 250 d. High-dose ATG pretransplant results in a low incidence of severe aGVHD without compromising donor chimaerism or elimination of minimal residual disease. Our results are similar to data obtained after matched sibling donor transplantation. [ABSTRACT FROM AUTHOR]

We used a gene amplification strategy to analyze T-cell receptor (TCR) gene rearrangements in 185 specimens, including mycosis fungoides/Sezary syndrome (MF/SS), other cutaneous neoplasms, inflammatory dermatoses, reactive lymphoid tissues,and normal skin. Genomic DNA was extracted from lesional tissues and rearrangements of the TCR-γ chain gene were amplified using the polymerase chain reaction (PCR) with primers specific for rearrangements involving Vγ1-8 or Vγ9 gene segments. The resulting PCR products were then separated according to their nucleotide sequence as well as size by denaturing gradient gel electrophoresis (DGGE). Dominant clonal TCR-γ gene rearrangements were detected in 61 of 68 MF/SS cases by PCR/DGGE. This sensitivity of 90% compared to a sensitivity of only 59% when dominant clonality was sought in 17 of these same cases by Southern blot analysis of TCR-&betal gene rearrangements. This difference in sensitivity was greatest in early, minimally infiltrated skin lesions. PCR/DGGE was also more sensitive than Southern blot analysis for detecting peripheral blood involvement in two cases of early MF. Among 12 additional specimens of suspected MF/SS, nine (75%) showed clonal TCR-γ gene rearrangements by PCR/DGGE including six of eight cases with a previously confirmed diagnosis of MF/SS and three of four cases without prior known MF/SS. Among 105 non-MF/SS specimens, dominant TCR-γ gene rearrangements were detected in only six cases (6%). Four were diagnosed as chronic dermatitis and two were diagnosed as cutaneous lymphoid hyperplasia. We conclude that the large majority of MF/SS cases, including patch phase disease, possess dominant clonal TCR-γ gene rearrangements. PCR/DGGE is more sensitive than Southern blot analysis for detecting dominant clonality and staging disease in patients with a confirmed diagnosis of MF/SS. However, because PCR/DGGE is sensitive enough to detect dominant TCR-y gene rearrangements in a subset of patients with chronic dermatitis, it cannot be used as the sole criterion for establishing a diagnosis of T-cell lymphoma. As with other molecular biologic clonality assays, clinicopathologic correclation is essential. Nevertheless, the detection of dominant clonality in some cases of histologically nonspecific dermatitis allows the identification of a previously unrecognized subset of patients, i.e., those with "clonal dermatitis." It will be important to determine the long-term risk of MF/SS among these patients because our study indicated that MF/SS can sometimes present with lesions indistinguishable from clonal dermatitis. [ABSTRACT FROM AUTHOR]

An abstract of the medical research "Molecular and functional analysis of γδ T cell expansions in immunodeficient patients," by Paul Fisch, Petros Christopoulus, Elisabeth Nikolopoulos, Hendrik Veelken and Stephan Wehl is presented.