Influence of ATLG serum levels on CD3/CD19-depleted hematopoietic grafts and on immune recovery in pediatric haplo-HSCT.

ABSTRACT: Anti-T lymphocyte globulin (ATLG) significantly reduces the risk of engraftment failure in allogeneic hematopoietic stem cell transplant (HSCT) but hampers posttransplant immune reconstitution. We hypothesized that in patients receiving haploidentical CD3/CD19-depleted grafts, these double-edged effects could be better balanced by attaining high ATLG serum concentrations before transplant but as low as possible on the day of transplant. Therefore, we moved the start of ATLG application to day -12 and determined serum concentrations of T-cell-specific ATLG in pediatric patients treated with 3 established dosing regimens (15, 30, or 60 mg/kg). Corresponding mean T-cell-specific ATLG serum concentrations at day 0 were 1.14, 2.99, or 12.10 µg/mL, respectively. Higher ATLG doses correlated with higher peak levels at days -8 and -7 and reduced graft rejection, whereas lower ATLG doses correlated with significantly faster posttransplant recovery of T and natural killer cells. The rate of graft-versus-host disease remained low, independent of ATLG doses. Moreover, in vitro assays showed that ATLG concentrations of 2.0 µg/mL and lower only slightly reduced the activity of natural killer cells, and therefore, the function of such effector cells might be preserved in the grafts. Pharmacokinetic analysis, compatible with linear first-order kinetics, revealed similar half-life values, independent of ATLG doses. Hence, the day on which a desired ATLG serum level is reached can be calculated before HSCT. Our retrospective study demonstrates the relevance of dosing and time of administration of ATLG on engraftment and immune recovery in ex vivo CD3/CD19-depleted haploidentical HSCT.

Anti-GD2 Antibody Dinutuximab Beta and Low-Dose Interleukin 2 After Haploidentical Stem-Cell Transplantation in Patients With Relapsed Neuroblastoma: A Multicenter, Phase I/II Trial.

PURPOSE: Patients with relapsed high-risk neuroblastoma (rHR-NB) have a poor prognosis. We hypothesized that graft-versus-neuroblastoma effects could be elicited by transplantation of haploidentical stem cells (haplo-SCT) exploiting cytotoxic functions of natural killer cells and their activation by the anti-GD2 antibody dinutuximab beta (DB). This phase I/II trial assessed safety, feasibility, and outcomes of immunotherapy with DB plus subcutaneous interleukin-2 (scIL2) after haplo-SCT in patients with rHR-NB. METHODS: Patients age 1-21 years underwent T-/B-cell-depleted haplo-SCT followed by DB and scIL2. The primary end point 'success of treatment' encompassed patients receiving six cycles, being alive 180 days after end of trial treatment without progressive disease, unacceptable toxicity, acute graft-versus-host-disease (GvHD) ≥grade 3, or extensive chronic GvHD. RESULTS: Seventy patients were screened, and 68 were eligible for immunotherapy. Median number of DB cycles was 6 (range, 1-9). Median number of scIL2 cycles was 3 (1-6). The primary end point was met by 37 patients (54.4%). Median observation time was 7.8 years. Five-year event-free survival (EFS) and overall survival from start of trial treatment were 43% (95% CI, 31 to 55) and 53% (95% CI, 41 to 65), respectively. Five-year EFS among patients in complete remission (CR; 52%; 95% CI, 31 to 69) or partial remission (44%; 95% CI, 27 to 60) before immunotherapy were significantly better compared with patients with nonresponse/mixed response/progressive disease (13%; 95% CI, 1 to 42; P = .026). Overall response rate in 43 patients with evidence of disease after haplo-SCT was 51% (22 patients), with 15 achieving CR (35%). Two patients developed GvHD grade 2 and 3 each. No unexpected adverse events occurred. CONCLUSION: DB therapy after haplo-SCT in patients with rHR-NB is feasible, with low risk of inducing GvHD, and results in long-term remissions likely attributable to increased antineuroblastoma activity by donor-derived effector cells.

Automated production of specific T cells for treatment of refractory viral infections after allogeneic stem cell transplantation.

Therapy-resistant viral reactivations contribute significantly to mortality after hematopoietic stem cell transplantation. Adoptive cellular therapy with virus-specific T cells (VST) has shown efficacy in various single-center trials. However, the scalability of this therapy is hampered by laborious production methods. In this study we describe the in-house production of VST in a closed system (CliniMACS Prodigy® system, Miltenyi Biotec). In addition, we report the efficacy in 26 patients with viral disease following hematopoietic stem cell transplantation in a retrospective analysis (adenovirus, n=7; cytomegalovirus, n=8; Epstein-Barr virus, n=4; multi-viral, n=7). The production of VST was successful in 100% of cases. The safety profile of VST therapy was favorable (n=2 grade 3 and n=1 grade 4 adverse events; all three were reversible). A response was seen in 20 of 26 patients (77%). Responding patients had a significantly better overall survival than patients who did not respond (P<0.001). Virus-specific symptoms were reduced or resolved in 47% of patients. The overall survival of the whole cohort was 28% after 6 months. This study shows the feasibility of automated VST production and safety of application. The scalability of the CliniMACS Prodigy® device increases the accessibility of VST treatment.

Expression of Surface-associated 82 kDa proMMP-9 in Lymphatic Leukemia Blast Cells Differentially Correlates With Prognosis.

BACKGROUND/AIM: Matrix metalloproteinases (MMPs) degrade extracellular matrix and process regulatory proteins. Recently, a membrane-bound 82kDa variant of proMMP-9 identified on myeloid blasts was shown to be associated with prognosis. PATIENTS AND METHODS: To investigate the role of 82kDa proMMP-9 with acute lymphoblastic leukemia (ALL) and chronic lymphoid leukemia (CLL), we performed flow-cytometry analysis of expression on ALL blasts (n=18) and CLL lymphocytes (n=21) from blood and correlated data with clinical parameters. RESULTS: In ALL, mature B-linear blasts expressed higher levels of 82kDa proMMP-9 compared to T-linear blasts. Elevated levels of 82kDa proMMP-9 were found in elderly patients and at patients with relapse. No correlation was observed on blood cells and extramedullary disease. In CLL, the 82kDa proMMP-9 expression did not correlate with any of the clinical parameters. CONCLUSION: Our findings suggest that higher levels of 82kDa proMMP-9 expression on blast cells may correlate with a more unfavorable ALL-subtype. Further studies are required to clarify the prognostic role of the 82kDa pro-MMP-9 expression.

Expression profiles of HMGB1 on B-CLL related leukocytes contribute to prediction of relapse.

BACKGROUND: The High Mobility Group Box 1 (HMGB1) is a nuclear protein that is frequently overexpressed in hematologic diseases and might be of relevance in immunogenic cancer control thus correlating with patients' (pts.) prognosis in diseases such as acute myeloid, acute lymphatic and chronic lymphocytic leukemia. MATERIALS AND METHODS: Expression profiles of blasts from AML (n = 21), ALL (n = 16) and of B-lymphocytes of CLL (n = 9) pts. were analyzed for surface expression of HMGB1 using flow cytometry. Expression was quantified and correlated with clinically and prognostically relevant markers. RESULTS: Expression profiling of HMGB1 in blasts of AML and ALL subtypes did not show differences between primary vs. secondary disease development and gender related differences. In ALL pts. however, age groups at initial diagnosis between ≥20 vs. <20 years were compared and showed significant differences (≥20 vs. <20 years; 89% vs. 49%, p  <0.05) with higher expression in higher age. In AML and CLL these differences were not visible. To evaluate the prognostic significance of HMGB1 expression, expression quantity was correlated with established and prognostic classification systems (in AML ELN, in ALL GMALL) and probability to relapse. No significant correlation was seen in these entities. However, when AML pts. were analyzed for remission rates after first anthracycline based induction therapy, in those who did not experience a complete remission significantly enhanced HMGB1 surface expression was seen (98 vs. 94%; p < 0.05; n = 20). Furthermore, for CLL it was shown that higher HMGB1 expression was found in pretreated patients with relapsed or/and refractory disease (1 vs. more relapses; 94 vs. 98%; p  <0.05; n = 9). CONCLUSION: HMGB1 is frequently expressed in hematologic malignancies. In this study it was shown that HMGB1 surface expression on AML blasts can be used as predictors for treatment response. In CLL it may be a marker for advanced disease. In order to implement this marker in FACS routine it could be a useful and practical tool for prognostic assessment and treatment planning.

Pediatric ALL relapses after allo-SCT show high individuality, clonal dynamics, selective pressure, and druggable targets.

Survival of patients with pediatric acute lymphoblastic leukemia (ALL) after allogeneic hematopoietic stem cell transplantation (allo-SCT) is mainly compromised by leukemia relapse, carrying dismal prognosis. As novel individualized therapeutic approaches are urgently needed, we performed whole-exome sequencing of leukemic blasts of 10 children with post-allo-SCT relapses with the aim of thoroughly characterizing the mutational landscape and identifying druggable mutations. We found that post-allo-SCT ALL relapses display highly diverse and mostly patient-individual genetic lesions. Moreover, mutational cluster analysis showed substantial clonal dynamics during leukemia progression from initial diagnosis to relapse after allo-SCT. Only very few alterations stayed constant over time. This dynamic clonality was exemplified by the detection of thiopurine resistance-mediating mutations in the nucleotidase NT5C2 in 3 patients' first relapses, which disappeared in the post-allo-SCT relapses on relief of selective pressure of maintenance chemotherapy. Moreover, we identified TP53 mutations in 4 of 10 patients after allo-SCT, reflecting acquired chemoresistance associated with selective pressure of prior antineoplastic treatment. Finally, in 9 of 10 children's post-allo-SCT relapse, we found alterations in genes for which targeted therapies with novel agents are readily available. We could show efficient targeting of leukemic blasts by APR-246 in 2 patients carrying TP53 mutations. Our findings shed light on the genetic basis of post-allo-SCT relapse and may pave the way for unraveling novel therapeutic strategies in this challenging situation.

Presence of centromeric but absence of telomeric group B KIR haplotypes in stem cell donors improve leukaemia control after HSCT for childhood ALL.

Although allogeneic hematopoietic stem-cell transplantation (HSCT) provides high cure rates for children with high-risk acute lymphoblastic leukaemia (ALL), relapses remain the main cause of treatment failure. Whereas donor killer cell immunoglobulin-like receptor (KIR) genotype was shown to impact on relapse incidence in adult myeloid leukaemia similar studies in paediatric ALL are largely missing. Effect of donor KIR genotype on transplant outcome was evaluated in 317 children receiving a first myeloablative HSCT from an HLA-matched unrelated donor or sibling within the prospective ALL-SCT-BFM-2003 trial. Analysis of donor KIR gene polymorphism revealed that centromeric presence and telomeric absence of KIR B haplotypes was associated with reduced relapse risk. A centromeric/telomeric KIR score (ct-KIR score) integrating these observations correlated with relapse risk (hazard ratio (HR) 0.58; P = 0.002) while it had no impact on graft-versus-host disease or non-relapse mortality. In multivariable analyses ct-KIR score was associated with reduced relapse risk (HR 0.58; P = 0.003) and a trend towards improved event-free survival (HR 0.76; P = 0.059). This effect proved independent of MRD level prior to HSCT. Our data suggest that in children with ALL undergoing HSCT after myeloablative conditioning, donor selection based on KIR genotyping holds promise to improve clinical outcome by decreasing relapse risk and prolonged event-free survival.

Clearance of Treatment Refractory Adenoviremia via Adenovirus-specific Donor T-Cell Transfer During Aplasia After αßTCR-CD19-Depleted Stem Cell Transplantation.

Here, we report the case of severe adenoviremia in a 7-year-old boy with highly-resistant, acute leukemia. A combined approach of αßTCR-CD19-depleted stem cell transplantation, enabling immunosuppression-free post-transplant care, and early transfer of adenovirus-specific donor T cells during aplasia resulted in rapid and complete clearance of the treatment-refractory adenoviremia.

Hematopoietic Stem Cell Transplantation as Treatment for Patients with DOCK8 Deficiency.

BACKGROUND: Biallelic variations in the dedicator of cytokinesis 8 (DOCK8) gene cause a combined immunodeficiency with eczema, recurrent bacterial and viral infections, and malignancy. Natural disease outcome is dismal, but allogeneic hematopoietic stem cell transplantation (HSCT) can cure the disease. OBJECTIVE: To determine outcome of HSCT for DOCK8 deficiency and define possible outcome variables. METHODS: We performed a retrospective study of the results of HSCT in a large international cohort of DOCK8-deficient patients. RESULTS: We identified 81 patients from 22 centers transplanted at a median age of 9.7 years (range, 0.7-27.2 years) between 1995 and 2015. After median follow-up of 26 months (range, 3-135 months), 68 (84%) patients are alive. Severe acute (III-IV) or chronic graft versus host disease occurred in 11% and 10%, respectively. Causes of death were infections (n = 5), graft versus host disease (5), multiorgan failure (2), and preexistent lymphoma (1). Survival after matched related (n = 40) or unrelated (35) HSCT was 89% and 81%, respectively. Reduced-toxicity conditioning based on either treosulfan or reduced-dose busulfan resulted in superior survival compared with fully myeloablative busulfan-based regimens (97% vs 78%; P = .049). Ninety-six percent of patients younger than 8 years at HSCT survived, compared with 78% of those 8 years and older (P = .06). Of the 73 patients with chimerism data available, 65 (89%) had more than 90% donor T-cell chimerism at last follow-up. Not all disease manifestations responded equally well to HSCT: eczema, infections, and mollusca resolved quicker than food allergies or failure to thrive. CONCLUSIONS: HSCT is curative in most DOCK8-deficient patients, confirming this approach as the treatment of choice. HSCT using a reduced-toxicity regimen may offer the best chance for survival.

Hematopoietic Stem Cell Transplantation in an Infant with Immunodeficiency, Centromeric Instability, and Facial Anomaly Syndrome.

Immunodeficiency, centromeric instability, and facial anomaly (ICF) syndrome is a rare autosomal recessive genetic condition with severe immunodeficiency, which leads to lethal infections if not recognized and treated in early childhood. Up-to-date treatment regimens consist of prophylactic and supportive treatment of the recurrent infections. Here, we report the case of a 1-year-old boy of Moroccan consanguineous parents, who was diagnosed at 4 months of age with ICF syndrome with a homozygous missense mutation in the DNMT3B gene. He was initially admitted to the hospital with recurrent pulmonary infections from the opportunistic pathogen Pneumocystis jirovecii (PJ). Further immunological workup revealed agammaglobulinemia in the presence of B cells. After successful recovery from the PJ pneumonia, he underwent hematopoietic stem cell transplantation (HSCT) from the HLA-matched healthy sister using a chemotherapeutic conditioning regimen consisting of treosulfan, fludarabine, and thiotepa. Other than acute chemotherapy-associated side effects, no serious adverse events occurred. Six months after HSCT immune-reconstitution, he had a stable chimerism with 2.9% autologous portion in the peripheral blood and a normal differential blood cell count, including all immunoglobulin subtypes. This is one of the first cases of successful HSCT in ICF syndrome. Early diagnosis and subsequent HSCT can prevent severe opportunistic infections and cure the immunodeficiency. Centromeric instability and facial anomaly remain unaffected. Although the long-term patient outcome and the neurological development remain to be seen, this curative therapy for immunodeficiency improves life expectancy and quality of life. This case is meant to raise physicians awareness for ICF syndrome and highlight the consideration for HSCT in ICF syndrome early on.

Significance of Frequencies, Compositions, and/or Antileukemic Activity of (DC-stimulated) Invariant NKT, NK and CIK Cells on the Outcome of Patients With AML, ALL and CLL.

Invariant natural killer T (iNKT)/natural killer (NK)/cytokine-induced killer (CIK) cells are important for immune surveillance. (I) Novel combinations of antibody 6B11 (targeting the Vα24-Jα18-invariant T-cell receptor) with CD4/CD8/CD1d/Vα24 for iNKT subset detection and "T/NK cell-like"-iNKT subsets were defined. Compared with healthy peripheral blood mononuclear cells (MNC) (significantly) lower proportions of iNKT cells (6B11/6B11CD3/6B11CD161), NK cells (CD3CD56/CD3CD161), and CIK cells (CD3CD56/CD3CD161) were found in peripheral blood MNC from acute myeloid (AML)/acute myeloid, lymphoid (ALL)/chronic lymphoid leukemia (CLL) patients in acute disease stages. Subtyping of iNKT cells revealed (significantly) higher proportions of CD3 T cells and CD161 NK cells in AML/ALL/CLL expressing 6B11 compared with healthy MNC. Prognostic evaluations showed higher proportions of iNKT/NK/CIK cells in favorable AML subgroups (younger age, primary, no extramedullary disease, achievement/maintenance of complete remission) or adult ALL and CLL patients. (II) iNKT/NK/CIK cell frequencies increased after (vs. before) mixed lymphocyte cultures of T-cell-enriched immune reactive cells stimulated with MNC/whole blood with or without pretreatment with "cocktails" (dendritic cells generating methods/kits inducing blasts' conversion to leukemia-derived dendritic cells from AML patients). Individual "cocktails" leading to "highest" iNKT cell frequencies could be defined. Antileukemic blast lytic activity correlated significantly with frequencies of iNKT/NK/CIK cells. In summary healthy MNC show significantly more iNKT/NK/CIK cells compared with AML/ALL/CLL MNC, a shift in the iNKT cell composition is seen in healthy versus leukemic samples and iNKT/NK/CIK cell-proportions in AML/ALL/CLL MNC samples correlate with prognosis. "Cocktail"-treated AML blasts lead to higher iNKT/NK/CIK cell frequencies and samples with antileukemic activity show significantly higher frequencies of iNKT/NK/CIK cells. Proportions of iNKT/NK/CIK cells should regularly be evaluated in AML/ALL/CLL diagnosis panels for quantitative/prognostic estimation of individual patients' antileukemic potential and their role in dendritic cells/leukemia-derived dendritic cells triggered immune surveillance.

Reduction of Minimal Residual Disease in Pediatric B-lineage Acute Lymphoblastic Leukemia by an Fc-optimized CD19 Antibody.

Prognosis of primary refractory and relapsed pediatric B-lineage acute lymphoblastic leukemia (ALL) is very poor. Relapse rates significantly correlate with persistent minimal residual disease (MRD). In MRD, favorable effector-target ratios prevail and thus this situation might be optimally suited for immunotherapy with antibodies recruiting immunological effector cells. We here report on the generation, preclinical characterization and first clinical application in B-lineage ALL of an Fc-optimized CD19 antibody. This third-generation antibody (4G7SDIE) mediated enhanced antibody-dependent cellular cytotoxicity (ADCC) against leukemic blasts with effector cells from healthy volunteers and B-lineage ALL patients. The antibody was produced in a university-owned production unit and was applied on a compassionate use basis to 14 pediatric patients with refractory and relapsed B-lineage ALL at the stage of MRD. In 10/14 patients, MRD was reduced by ≥ 1 log or below the patient-individual detection limit, and 5/14 patients have achieved ongoing complete molecular remission with a median leukemia-free survival of 428 days. Two additional patients died in complete molecular remission due to complications not related to antibody therapy. Besides profound in vivo B-cell depletion, side effects were negligible. A clinical phase 1/2 study to further assess the therapeutic activity of 4G7SDIE is in preparation.

De novo PIK3R1 gain-of-function with recurrent sinopulmonary infections, long-lasting chronic CMV-lymphadenitis and microcephaly.

PIK3R1 (phosphoinositide-3-kinase, regulatory subunit 1) gain-of-function has recently been described in patients with recurrent sinopulmonary infections, chronic CMV-/EBV-infections, lymphoproliferation, and hypogammaglobulinemia. Here we report a 15-year-old boy with treatment refractory CMV lymphadenitis, severe combined immunodeficiency, microcephaly and a severe developmental defect of Th17 cells. To avoid poor outcome, hematopoietic stem cell transplantation (HSCT) was performed. Subsequently, whole exome sequencing revealed a de novo heterozygous G-to-C mutation (chr5: 5:67,589,663: G>C) at the splice donor site of the PIK3R1 gene. Our data suggest that PIK3R1 gain-of-function leads to developmental defects in helper and regulatory T-cell subsets, the latter expanding the immunological features of PIK3R1 gain-of-function. T-cell subsets play a critical role in the regulation of immune response against infectious agents and of autoimmunity and thus may be particularly accountable for the clinical phenotype of affected patients.

Adoptive T-cell therapy with hexon-specific Th1 cells as a treatment of refractory adenovirus infection after HSCT.

Hematopoietic stem cell transplantation (HSCT) has improved over the last few decades. However, viral infections are often refractory to pharmacologic treatment and require alternative treatment strategies such as immunotherapy. Adenovirus (AdV) is th predominant disease-causing pathogen in pediatric HSCT. In a clinical trial, we analyzed safety and efficacy of ex vivo adoptive T-cell transfer (ACT) with hexon-specific T cells, predominantly of the T-helper cell 1 (Th1) phenotype, in 30 patients with AdV disease or viremia. ACT was feasible with no acute toxicities or significant onset of graft-versus-host disease. ACT led to in vivo antiviral immunity for up to 6 months with viral control, resulting in complete clearance of viremia in 86% of patients with antigen-specific T-cell responses. After ACT and a follow-up of 6 months, overall survival was markedly increased in responders (mean, 122 days; 15 survivors) compared with nonresponders who all died shortly after ACT (mean, 24 days; no survivors). AdV-related mortality was 100% in nonresponders compared with 9.5% in responders (≥1 log reduction of DNA copies per milliliter after ACT). In summary, ex vivo ACT of AdV-specific Th1 cells was well tolerated and led to successful and sustained restoration of T-cell immunity correlated with virologic response and protection from virus-related mortality. This cellular immunotherapy is a short-term available and broadly applicable treatment. The study is registered at European Union Clinical Trials Register as 2005-001092-35.

Cytokine Release Patterns in Mixed Lymphocyte Culture (MLC) of T-Cells with Dendritic Cells (DC) Generated from AML Blasts Contribute to Predict anti-Leukaemic T-Cell Reactions and Patients' Response to Immunotherapy.

To enlighten interactions between autologous, allogeneic or T-cells from patients after stem cell transplantation with leukaemia-derived-dendritic-cells containing dendritic cells or blast containing mononuclear cells (n = 21, respectively), we determined cytokine-concentrations (interleukin 2, 4, 6, 10, tumor-necrosis-factor-α, interferon-γ) in supernatants of mixed-lymphocyte-culture and in serum (n = 16) of 20 patients with acute myeloid leukaemia and three patients with myelodysplastic syndromes by cytometric-bead-assay. We correlated our data with lytic capabilities of stimulated T-cells in a fluorolysis-assay and clinical data: Dendritic-cell-/mononuclear-cell-stimulation of T-cells resulted in increased cytokine-levels in culture-medium compared to serum. There were no significant differences between cytokine-patterns of cases with/without lytic T-cell-activity, response to immunotherapy (stem cell transplantation/donor-lymphocyte-infusion) or graft-versus-host-disease. However, some predictive cytokine-cut-off-values for antileukaemic T-cell-activity, patients' response to immunotherapy and graft-versus-host-disease could be defined. Cytokine-profiles alone, without functional assays, are no useful tool to predict antileukaemic T-cell-function, although they can indicate lytic T-cell-activity, patients' response to immunotherapy and graft-versus-host-disease.

Immunotherapy with the trifunctional anti-CD20 x anti-CD3 antibody FBTA05 (Lymphomun) in paediatric high-risk patients with recurrent CD20-positive B cell malignancies.

Children with B cell malignancies refractory to standard therapy are known to have a poor prognosis and very limited treatment options. Here, we report on the treatment and follow-up of ten patients diagnosed with relapsed or refractory mature B-cell Non Hodgkin Lymphoma (B-NHL), Burkitt leukaemia (B-AL) or pre B-acute lymphoblastic leukaemia (pre B-ALL). All children were treated with FBTA05 (now designated Lymphomun), an anti-CD3 x anti-CD20 trifunctional bispecific antibody (trAb) in compassionate use. Within individual treatment schedules, Lymphomun was applied (a) after allogeneic stem cell transplantation (allo-SCT, n = 6) to induce sustained long-term remission, or (b) stand alone prior to subsequent chemotherapy to eradicate residual disease before allo-SCT (n = 4). Nine of ten children displayed a clinical response: three stable diseases (SD), one partial remission (PR) and five induced or sustained complete remissions (CR). Five of these nine responders died during follow-up. The other patients still maintain CR with a current overall survival of 874-1424 days (median: 1150 days). In conclusion, despite the dismal clinical prognosis of children refractory to standard therapy, immunotherapy with Lymphomun resulted in a favourable clinical outcome in this cohort of refractory paediatric patients.

Lowest numbers of primary CD8(+) T cells can reconstitute protective immunity upon adoptive immunotherapy.

Patients undergoing allogeneic hematopoietic stem cell transplantation (allo-HSCT) are threatened by potentially lethal viral manifestations like cytomegalovirus (CMV) reactivation. Because the success of today's virostatic treatment is limited by side effects and resistance development, adoptive transfer of virus-specific memory T cells derived from the stem cell donor has been proposed as an alternative therapeutic strategy. In this context, dose minimization of adoptively transferred T cells might be warranted for the avoidance of graft-versus-host disease (GVHD), in particular in prophylactic settings after T-cell-depleting allo-HSCT protocols. To establish a lower limit for successful adoptive T-cell therapy, we conducted low-dose CD8(+) T-cell transfers in the well-established murine Listeria monocytogenes (L.m.) infection model. Major histocompatibility complex-Streptamer-enriched antigen-specific CD62L(hi) but not CD62L(lo) CD8(+) memory T cells proliferated, differentiated, and protected against L.m. infections after prophylactic application. Even progenies derived from a single CD62L(hi) L.m.-specific CD8(+) T cell could be protective against bacterial challenge. In analogy, low-dose transfers of Streptamer-enriched human CMV-specific CD8(+) T cells into allo-HSCT recipients led to strong pathogen-specific T-cell expansion in a compassionate-use setting. In summary, low-dose adoptive T-cell transfer (ACT) could be a promising strategy, particularly for prophylactic treatment of infectious complications after allo-HSCT.

CD4(+)and CD8(+)T-cell reactions against leukemia-associated- or minor-histocompatibility-antigens in AML-patients after allogeneic SCT.

T-cells play an important role in the remission-maintenance in AML-patients (pts) after SCT, however the role of LAA- (WT1, PR1, PRAME) or minor-histocompatibility (mHag, HA1) antigen-specific CD4(+) and CD8(+)T-cells is not defined. A LAA/HA1-peptide/protein stimulation, cloning and monitoring strategy for specific CD8(+)/CD4(+)T-cells in AML-pts after SCT is given. Our results show that (1) LAA-peptide-specific CD8+T-cells are detectable in every AML-pt after SCT. CD8(+)T-cells, recognizing two different antigens detectable in 5 of 7 cases correlate with long-lasting remissions. Clonal TCR-Vß-restriction exemplarily proven by spectratyping in PRAME-specific CD8(+)T-cells; high PRAME-peptide-reactivity was CD4(+)-associated, as shown by IFN-γ-release. (2) Two types of antigen-presenting cells (APCs) were tested for presentation of LAA/HA1-proteins to CD4(+)T-cells: miniEBV-transduced lymphoblastoid cells (B-cell-source) and CD4-depleted MNC (source for B-cell/monocyte/DC). We provide a refined cloning-system for proliferating, CD40L(+)CD4(+)T-cells after LAA/HA1-stimulation. CD4(+)T-cells produced cytokines (GM-CSF, IFN-γ) upon exposure to LAA/HA1-stimulation until after at least 7 restimulations and demonstrated cytotoxic activity against naive blasts, but not fibroblasts. Antileukemic activity of unstimulated, stimulated or cloned CD4(+)T-cells correlated with defined T-cell-subtypes and the clinical course of the disease. In conclusion we provide immunological tools to enrich and monitor LAA/HA1-CD4(+)- and CD8(+)T-cells in AML-pts after SCT and generate data with relevant prognostic value. We were able to demonstrate the presence of LAA-peptide-specific CD8(+)T-cell clones in AML-pts after SCT. In addition, we were also able to enrich specific antileukemic reactive CD4(+)T-cells without GvH-reactivity upon repeated LAA/HA1-protein stimulation and limiting dilution cloning.