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Highly sensitive and specific platforms for the detection of anti–severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) antibodies are becoming increasingly important for evaluating potential SARS-CoV-2 convalescent plasma donors, studying the spread of SARS-CoV-2 infections, and identifying individuals with seroconversion. This study provides a comparative validation of 4 anti–SARS-CoV-2 platforms. A unique feature of the study is the use of a representative cohort of convalescent patients with coronavirus disease 2019 and a mild to moderate disease course. All platforms showed significant correlations with a SARS-CoV-2 plaque reduction neutralization test, with highest sensitivities for the Euroimmun and the Roche platforms, suggesting their preferential use for screening persons at increased risk of SARS-CoV-2 infections.

Background Effective therapy of Acute Lung Injury (ALI) is still a major scientific and clinical problem. To define novel therapeutic strategies for sequelae of blunt chest trauma (TxT) like ALI/Acute Respiratory Distress Syndrome, we have investigated the immunomodulatory and regenerative effects of a single dose of ex vivo expanded human or rat mesenchymal stromal cells (hMSCs/rMSCs) with or without priming, immediately after the induction of TxT in Wistar rats. Methods We analyzed the histological score of lung injury, the cell count of the broncho alveolar lavage fluid (BAL), the change in local and systemic cytokine level and the recovery of the administered cells 24 h and 5 days post trauma. Results The treatment with hMSCs reduced the injury score 24 h after trauma by at least 50% compared with TxT rats without MSCs. In general, TxT rats treated with hMSCs exhibited a lower level of pro-inflammatory cytokines (interleukin [IL]-1B, IL-6) and chemokines (C-X-C motif chemokine ligand 1 [CXCL1], C-C motif chemokine ligand 2 [CCL2]), but a higher tumor necrosis factor alpha induced protein 6 (TNFAIP6) level in the BAL compared with TxT rats after 24 h. Five days after trauma, cytokine levels and the distribution of inflammatory cells were similar to sham rats. In contrast, the treatment with rMSCs did not reveal such therapeutic effects on the injury score and cytokine levels, except for TNFAIP6 level. Conclusion TxT represents a suitable model to study effects of MSCs as an acute treatment strategy after trauma. However, the source of MSCs has to be carefully considered in the design of future studies.

Background & Aim Background The increasing request for culture expanded mesenchymal stromal cells (MSC) in the last years discloses the need to reduce costs and man power in the manufacturing process. This can be achieved by the use of closed, (semi-)automated bioreactor systems. We have decided to test a functionally closed hollow-fibre bioreactor system (Quantum®). Surveillance of metabolic parameters and adaptation of feeding in dependence of these is possible. However, the nature of the hollow-fibre surface does not support attachment of MSC without coating. Several biological substances for coating are available, either as isolated proteins (e.g. fibronectin, vitronectin), or as complex protein mixtures derived from human blood (e.g. cryoprecipitate, platelet lysate). The use of such closed systems additionally reduces the risk of contaminations. Methods, Results & Conclusion Methods MSC were cultured as conventional cell culture or in a platelet lysate (PL), cryoprecipitate (CP), vitronectin (VN), or fibronectin (FN) coated Quantum® bioreactor (TerumoBCT) for 5 - 15 days in alphaMEM (Lonza), supplemented with 5% - 10% platelet lysate (PL from IKT Ulm) and 1 i.u. heparin (B.Braun). The surface of the Quantum® bioreactor is 21,000 cm2. For Quantum®, the feed rate was adjusted based on daily measured lactate or glucose levels. For conventional cell culture, mainly 2 chamber CellSTACK® (Corning) with a surface of 1272 cm2 were used and complete medium exchange was performed twice a week. TrypZEAN® (Lonza) was used for detachment of cells. Results For results of the cell expansion experiments (N ≥ 3) using the different coating reagents refer to Table 1. Conclusion We showed that the Quantum® bioreactor is suitable for expansion of MSC using PL, CP, FN or VN as coating reagent. Despite higher doubling times for cells grown in the Quantum®, this system may help to save costs since less man power is needed to manage the system and several steps do not necessarily have to be performed in a class A cabinet. In addition, clinically relevant cell numbers could be achieved by the use of a single bioreactor (data not shown). Perspective Protocols for cell expansion in the Quantum® still may have to be optimized in order to increase its potential in saving man power and consumables.

Polytrauma (PT) is a life-threatening disease and a major global burden of injury. Mesenchymal stromal cells (MSC) might be a therapeutic option for PT patients due to their anti-inflammatory and regenerative potential. We hypothesised that the inflammatory response of MSC is similar after exposure to selected trauma-relevant factors to sera from PT patients (PTS). Therefore, we investigated the effects of a mixture of defined factors, supposed to play a role on MSC in the early phase of PT. Additionally, in a translational approach we investigated the effect of serum from PT patients on MSC in vitro. MSC were incubated with a PT cocktail in physiological (PTCL) and supra-physiological (PTCH) concentrations or PTS. The effect on gene expression and protein secretion of MSC was analysed by RNA sequencing, ELISA and Multiplex assays of cell culture supernatant. Stimulation of MSC with PTCH, PTCL or IL1B led to significant up- or downregulation of 470, 183 and 469 genes compared to unstimulated MSC at 6 h. The intersection of differentially expressed genes in these groups was very high (92% overlap with regard to the PTCL group; treated for 6 h). Cytokine secretion profile of MSC revealed that IL1B mimics the effect of a more complex PT cocktail as well. However, there was only a minor proportion of overlapping differentially expressed genes between the MSC group stimulated with early times of PTS and the MSC group stimulated with PTCH, PTCL and IL1B. In conclusion, the effect of sera from PT patients on MSC activation cannot be simulated by the chosen trauma-relevant factors. Furthermore, we conclude that while IL1B might be useful to prime MSC prior to therapeutic application, it might not be as useful for the in vitro study of functional properties of MSC in the context of PT.

Background & Aim Adipose mesenchymal stromal cells (ASC) are commonly utilized in various cell therapies and recently in phase I clinical trials to counteract the development of knee osteoarthritis. Administered-ASC in the knee joints enter in close contact with the OA inflammatory milieu and hypoxic environment,which could modulate their characteristics.Little is known about the OA milieu factors that could enhance the migration and tissue specific engraftment of exogenously injected ASC for successful regenerative cell therapy.Therefore,we tested the effect of OA milieu on good manufactured practice (GMP)-ASC,both in normoxic and hypoxic conditions and evaluated their migration properties and cytokine receptors. Methods, Results & Conclusion We analyzed IL8, IP10,SDF-1,MCP1,MIP1α, MIP1β,RANTES and IL6 cytokines in two different OA milieu:OA synovial fluid (SF) and OA-conditioned medium (CM) from synoviocytes.These milieu adequately represent the OA environment for ASC injection and the milieu containing all the soluble factors released by the target tissue of ASC, respectively. The same cytokines were analyzed also on basal GMP-ASC,both in normoxic and hypoxic conditions. Afterwards, GMP-ASC were treated either with OA-SF or OA-CM for 48hours and tested for migration and cytokine receptors expression, as well as the cytokine secretion, both in normoxia or hypoxia (1,5%O2). Healthy SF was used as control. In OA-SF we detected higher amount of IP10 than in OA-CM while MCP1 and MIP1β were higher in OA-CM compared to OA-SF.All the other cytokines were detected in the same amounts in both OA milieu. We demonstrated that GMP-ASC show an increase in proliferation, migration, no changes in the amount of cytokines released and modulation of CXCR1,CXCR3,CCR1 and CCR5 receptors in hypoxic condition. Moreover,GMP-ASC migration increased 15-fold when treated either with OA-SF or OA-CM compared to healthy SF,both in normoxic and hypoxic conditions.GMP-ASC treated in OA milieu showed an increase of CXCR3, CCR3 and IL6R and a decrease of CCR1,CCR2 receptors. IP10 was the only chemokine of the OA milieu down-modulated after treatment with GMP-ASC.We demonstrated specific effects of OA milieu on both GMP-ASC migration and cytokine receptor expression that were strictly dependent by the inflammatory and hypoxic environment.The use of characterized OA milieu might contributes to define the therapeutic effects of GMP-ASC and indicates that IP10-CXCR3 axis is partially involved in GMP-ASC effect on synovial macrophages.

Background: The risk of microbial contamination of cellular products can be reduced when cultured in the presence of antibiotics. This however, may impact the sensitivity of microbiological tests. Given that the addition of antibiotics to cell/tissue products does not guarantee sterility but may just reduce the proliferation rate of microorganisms, microbiological testing of medicinal products remains obligatory. Thus, an appropriate method to test for microbial contamination of antibiotic-containing products has to be validated. Objectives: In the context of microbiological testing of a cellular advance therapy medicinal product, the method was validated and approved by German competent authorities for four different matrices with three matrices containing antibiotics. The paper shall provide help for establishing test methods for other investigational medicinal products which contain antibiotics. Methods: Matrices were spiked individually with Staphylococcus aureus, Bacillus subtilis, Pseudomonas aeruginosa, Streptococcus pyogenes, Escherichia coli, Clostridium sporogenes, Propionibacterium acnes, Candida albicans, and Aspergillus brasiliensis. Samples were pretreated with penicillinase for 1 h before inoculation and incubation in BacT/ALERT iFA Plus and iFN Plus culture bottles using 3D BacT/ALERT automates. Microorganisms within positive BacT/ALERT bottles were specified. The procedure was performed in two different laboratories to prove robustness of test. Results: All nine tested microorganisms were detected within 14 days of incubation in accordance with requirements of the European Pharmacopoiea in terms of sensitivity, specificity and robustness of the test. Penicillin and streptomycin did not have any influence on specifications defined within the investigational medicinal product dossier. Conclusions: Culturing cellular products in the presence of antibiotics can serve as an effective method to reduce contamination risk but only if the chosen antibiotics neither have any influence on specifications of the investigational medicinal product nor interfere with microbiological tests. Consequently, cells and tissues primarily contaminated with microorganisms, like placenta, may be considered as a source of cellular therapeutics when cultured for a sufficient time with antibiotics and tested with a validated method. The choice of microorganisms for the validation of the microbiological test should always consider all conceivable scenarios and should not be reduced to minimal criteria defined in European Pharmacopoiea, wrongfully believing to thus save time and effort.

Leukemic stem cells (LSC) might be the source for leukemic disease self-renewal and account for disease relapse after treatment, which makes them a critical target for further therapeutic options. We investigated the role of cytotoxic T-lymphocytes (CTL) counteracting and recognizing LSC. Leukemia-associated antigens (LAA) represent immunogenic structures to target LSC. We enriched the LSC-containing fraction of 20 AML patients and hematopoietic stem cells (HSC) of healthy volunteers. Using microarray analysis and qRT-PCR we detected high expression of several LAA in AML cells but also in LSC. PRAME (p = 0.0085), RHAMM (p = 0.03), WT1 (p = 0.04) and Proteinase 3 (p = 0.04) showed significant differential expression in LSC compared with HSC. PRAME, RHAMM and WT1 are furthermore also lower expressed on leukemic bulk. In contrast, Proteinase 3 indicates a higher expression on leukemic bulk than on LSC. In colony forming unit (CFU) immunoassays, T cells stimulated against various LAA indicated a significant inhibition of CFUs in AML patient samples. The LAA PRAME, RHAMM and WT1 showed highest immunogenic responses with a range up to 58-83%. In a proof of principle xenotransplant mouse model, PRAME-stimulated CTL targeted AML stem cells, reflected by a delayed engraftment of leukemia (p = 0.0159). Taken together, we demonstrated the expression of several LAA in LSC. LAA-specific T cells are able to hamper LSC in immunoassays and in a mouse model, which suggests that immunotherapeutic approaches have the potential to target malignant stem cells.

The estimated frequency of MSCs in BM is about 0.001–0.01% of total nucleated cells. Most commonly, one applied therapeutic cell dose is about 1–5 million MSCs/kg body weight, necessitating a reliable, fast, and safe expansion system. The limited availability of MSCs demands for an extensive ex vivo amplification step to accumulate sufficient cell numbers. Human platelet lysate (PL) has proven to be a safe and feasible alternative to animal-derived serum as supplement for MSC cultivation. We have investigated the functionally closed automated cell culture hollow fiber bioreactor Quantum cell expansion system as an alternative novel tool to conventional tissue flasks for efficient clinical-scale MSC isolation and expansion from bone marrow using PL. Cells expanded in the Quantum system fulfilled MSC criteria as shown by flow cytometry and adipogenic, chondrogenic, and osteogenic differentiation capacity. Cell surface expression of a variety of chemokine receptors, adhesion molecules, and additional MSC markers was monitored for several passages by flow cytometry. The levels of critical media components like glucose and lactate were analyzed. PDGF-AA, PDGF-AB/BB, bFGF, TGF-β1, sICAM-1, sVCAM-1, RANTES, GRO, VEGF, sCD40L, and IL-6 were assessed using a LUMINEX platform. Originally optimized for the use of fetal calf serum (FCS) as supplement and fibronectin as coating reagent, we succeeded to obtain an average of more than 100 × 106 of MSCs from as little as 18.8–28.6 ml of BM aspirate using PL. We obtained similar yields of MSCs/μl BM in the FCS-containing and the xenogen-free expansion system. The Quantum system reliably produces a cellular therapeutic dose in a functionally closed system that requires minimal manipulation. Both isolation and expansion are possible using FCS or PL as supplement. Coating of the hollow fibers of the bioreactor is mandatory when loading MSCs. Fibronectin, PL, and human plasma may serve as coating reagents.

The immune reconstitution after allogeneic hematopoietic stem cell transplantation comprises thymus-dependent and thymus-independent pathways. We wanted to improve the understanding of this complex process using two different measurements at definite checkpoints of T-cell neogenesis. We therefore assessed the thymus-dependent pathway by combining measurements of single joint T-cell receptor excision circles (sjTREC) and β T-cell receptor excision circles (βTREC) in an improved quantitative light-cycler hybridization polymerase chain reaction assay. In a subgroup of patients, we additionally assessed the proliferation kinetics of the CD31(+) thymic naïve cell population, which corresponds to recent thymic emigrants by six-color immunostaining. After the establishment of normal values in 22 healthy volunteers, we applied our polymerase chain reaction to 66 patients undergoing allogeneic hematopoietic stem cell transplantation at a median age of 44 years. It took more than 2 years after transplant to restore the pre-transplant thymic proliferation capacity. Only one third of the patients in our longitudinal study reached age-adjusted normal values for both sjTREC and βTREC at a median follow-up of 558 days, with acute graft-versus-host disease being the most prominent negative factor by univariate analysis. We observed several patterns of sjTREC and βTREC recovery suggesting different mechanisms of thymic damage in individual patients. In a comparison of CD31(+) thymic naïve cells between volunteers and patients after transplant we found a significantly higher peak proliferation rate within the latter population in the first year after transplantation. The combination of measurements of sjTREC and βTREC by our simplified polymerase chain reaction assay provides insight about the stage of T-cell development affected by different types of damage and may help to choose the correct therapeutic intervention. Besides the sole thymic T-cell neogenesis, proliferation within the CD31(+) thymic naïve cell compartment contributed to the replenishment of the naïve T-cell pool after transplantation.

Background aims The clinical use of human mesenchymal stromal cells (MSC) requires ex vivo expansion in media containing supplements such as fetal bovine serum or, alternatively, human platelet lysate (PL). Methods Platelet concentrates were frozen, quarantine stored, thawed and sterile filtered to obtain PL. PL content and its effect on fibroblast-colony-forming unit (CFU-F) formation, MSC proliferation and large-scale expansion were studied. Results PL contained high levels of basic fibroblast growth factor (bFGF), soluble CD40L (sCD40L), vascular cell adhesion molecule-1 (VCAM-1), intercellular adhesion molecule-1 (ICAM-1), platelet-derived growth factor AA (PDGF-AA), platelet-derived growth factor AB/BB (PDGF-AB/BB), chemokine (C-C) ligand 5 (CCL5; RANTES) transforming growth factor-β1 (TGF-β1) and chemokine (C-X-C) ligand 1/2/3 (GRO), with low batch-to-batch variability, and most were stable for up to 14 days. Inhibition of PDGF-BB and bFGF decreased MSC proliferation by about 20% and 50%, respectively. The strongest inhibition (about 75%) was observed with a combination of anti-bFGF + anti-PDGF-BB and anti-bFGF + anti-TGF-β1 + anti-PDGF-BB. Interestingly, various combinations of recombinant PDGF-BB, bFGF and TGF-β1 were not sufficient to promote cell proliferation. PL from whole blood-derived pooled platelet concentrates and apheresis platelet concentrates did not differ significantly in their growth-promoting activity on MSC. Conclusions PL enhances MSC proliferation and can be regarded as a safe tool for MSC expansion for clinical purposes. \in particular, PDGF-BB and bFGF are essential components for the growth-promoting effect of PL, but are not sufficient for MSC proliferation.

Background aims. Mesenchymal stromal cells (MSC) are the focus of research in regenerative medicine aiming at the regulatory approval of these cells for specific indications. To cope with the regulatory requirements for somatic cell therapy, novel approaches that do not interfere with the natural behavior of the cells are necessary. In this context in vivo magnetic resonance imaging (MRI) of labeled MSC could be an appropriate tool. Cell labeling for MRI with a variety of different iron oxide preparations is frequently published. However, most publications lack a comprehensive assessment of the noninterference of the contrast agent with the functionality of the labeled MSC, which is a prerequisite for the validity of cell-tracking via MRI. Methods.We studied the effects of iron oxide-poly(L-lactide) nanoparticles in MSC with flow cytom-etry, transmission electron microscopy (TEM), confocal laser scanning microscopy (CLSM), Prussian blue staining, CyQuant® proliferation testing, colony-forming unit-fibroblast (CFU-F) assays, flow chamber adhesion testing, immuno-logic tests and differentiation tests. Furthermore iron-labeled MSC were studied by MRI in agarose phantoms and Wistar rats. Results. It could be demonstrated that MSC show rapid uptake of nanoparticles and long-lasting intracellular persistence in the endosomal compartment. Labeling of the MSC with these particles has no influence on viability, differentiation, clonogenicity, proliferation, adhesion, phenotype and immunosuppressive properties. They show excellent MRI properties in agarose phantoms and after subcutaneous implantation in rats over several weeks. Conclusions. These particles qualify for studying MSC homing and trafficking via MRI.

Necrosis is a characteristic feature of advanced solid tumors. Released necrotic factors, also referred to as damage associated molecular patterns (DAMPs), are known to critically impact the tumor microenvironment by enhancing angiogenesis or influencing the immune response. We have recently shown that DAMPs can act as chemoattractants and activators of granulocytes. We demonstrate that necrotic material from both normal and tumor cells promotes proliferation and trafficking of human mesenchymal stem cells (MSCs). We characterize the protein high mobility group box 1 (HMGB1) as a crucial member of DAMPs within necrotic material. In addition, we show that DAMPs interfere with expression of indoleamine 2, 3-dioxygenase (IDO) in MSCs. The biological activity of necrotic material toward MSCs is abolished once these DAMPs are oxidized. MSCs found within tumor tissue can act as immunoregulatory cells and are able to promote tumor metastasis, thus playing a crucial role within the tumor microenvironment. Here, we reveal DAMPs to be crucial factors in the setting of MSC biology within the tumor microenvironment. The tumor microenvironment is characterized by reducing and hypoxic conditions that protect DAMPs from oxidation. Based on our results, oxidizing conditions should be considered for therapeutic approaches that target the tumor microenvironment.

BACKGROUND: Cytomegalovirus (CMV) disease constitutes a serious complication after allogeneic stem cell transplantation. For the clearance of CMV, CD8+ T cells are pivotal. STUDY DESIGN AND METHODS: Here, the novel streptamer technology was used at good manufacturing practice (GMP) level for adoptive transfer of CMV-specific T cells into acute leukemia patients with recurrent high CMV antigenemia after allogeneic stem cell transplantation. RESULTS: After a single transfusion, the frequency of CMV-specific CD8+CD45RA+CCR7– effector T cells increased dramatically from 0.0% to a maximum of 27.1% of all T cells. These T cells were clearly donor derived and did not stem from intrinsic reconstitution, as demonstrated by analysis of 1) donor chimerism through single-tandem repeats, 2) T-cell receptor excision circles, and 3) Vβ-chain typing by polymerase chain reaction. Clinically, the specific T-cell transfer resulted in a persistent clearance of the CMV antigenemia, which allowed the patients to discontinue toxic antiviral drug therapy without further high-level reactivation of CMV, demonstrating the power of the streptamer technology. CONCLUSION: Taken together, the streptamer technology offers the advantage of selecting virus-specific CD8+ T cells at GMP level for adoptive T-cell transfer, thus inducing long-lasting specific CD8+ T-cell responses without increasing the risk for graft-versus-host disease.

The Ewing family of tumors (EFT) is an important group of pediatric malignancies with a guarded prognosis. Little is known about the heterogeneity of EFT cells, and the cellular origin of EFT is disputed. We now add evidence that EFT are heterogeneous by showing that EFT cells from spheres growing in serum-free medium are markedly more tumorigenic than adherently growing EFT cells. Furthermore, EFT cells strongly expressing CD57 (HNK-1), a surface marker for migrating and proliferating neural crest cells, are more tumorigenic than cells with low expression of CD57, possibly mediated in part by enhanced adhesion and invasion. We contribute to the controversy about the cellular origin of EFT by clonal analysis, showing that EFT cells can differentiate similar to neural crest cells. These data increase our knowledge about the pathogenesis and heterogeneity of EFT.

During the last years remission rates of more than 72% for arsenic(III)-oxide (As(2)O(3)) treatment in relapsed or refractory acute promyelocytic leukemia have been published. As(2)O(3) is under clinical investigation for therapy of leukemia and solid tumors. Due to the chemical affinity of arsenic and antimony, we analyzed the potency of antimony(III)-oxide (Sb(2)O(3)) to exert As(2)O(3)-like effects. Based on the same molar concentrations, lower efficacy in apoptosis induction and caspase-independent decrease of mitochondrial membrane potential was observed for Sb(2)O(3). No difference in sensitivity to As(2)O(3) or Sb(2)O(3) was detected in CEM cells when compared to their multiple drug resistant derivatives. Apoptosis was induced by combining sub-apoptotic concentrations of Sb(2)O(3) or As(2)O(3) with sub-apoptotic concentrations of DL: -buthionine-[S,R]-sulfoximine (BSO). Other modulators of the cellular redox system showed this effect to a lower extent and enhancement was not consistent for the different cell lines tested. Caspase inhibitors protected cell lines from Sb(2)O(3)- and As(2)O(3)-induced apoptosis. When BSO was added, the inhibitors lost their protective ability. The ability of modulators of the cellular redox system in clinically applicable concentrations to enhance the apoptotic effects of the two oxides in a synergistic way may be helpful to reduce their toxicity by optimizing their dose.

Antithymocyte globulin (ATG) and antilymphocyte globulin (ALG) are currently used successfully for immunosuppressive treatment of aplastic anemia. In this study we have investigated whether commercial ATG/ALG preparations contain antibodies against glycosylphosphatidyl-inositol anchored proteins (GPI-AP), which could be responsible for emergence of GPI-deficient populations in aplastic anemia after ATG/ALG therapy. We analyzed four commercial ATG/ALG preparations by competitive binding assays using flow cytometry. Quantification was achieved by calculating the concentration of ATG/ALG required to give 50% inhibition of binding the specific fluorochrome-labeled monoclonal antibody (EC50). High concentrations of antibodies against the GPI-anchored protein CD52 were found in all preparations (Lymphoglobulin Genzyme, Thymoglobulin Genzyme, ATGAM. Pharmacia & Upjohn, and ATG-Fresenius S Fresenius). Antibodies against the GPI-anchored protein CD48 are present in significant concentrations except in the preparation ATGAM. CD16 antibodies were found in lower concentrations. We could not detect significant concentrations of antibodies against the GPI-anchored proteins CD157 and CD14. Campath-1H, a monoclonal antibody against the GPI-anchored protein CD52, has been used as immunosuppressive tool for T-cell depletion. CD52 antibodies in ATG/ALG preparations might contribute in the same way to the immunosuppressive effects in treatment of aplastic anemia. It is known that in a substantial proportion of patients with aplastic anemia GPI-deficient cells are present in a low level at diagnosis or emerge after immunosuppressive therapy. GPI-anchored antibodies in ATG/ALG preparations might lead to a relative advantage for pre-existing GPI-deficient cells caused by an escape from the antibody-mediated attack.

CD4+CD25+ regulatory T cells (Tregs) can influence various immune responses. Little is known about the effects of the Abl/Src kinase inhibitor dasatinib on Tregs which regulate anti-tumor/leukaemia immune responses. The present study demonstrated that dasatinib inhibited proliferation of Tregs and CD4+CD25- T cells in a dose-dependent manner, which was associated with the decreased production of corresponding cytokines. Treatment of Tregs with dasatinib inhibited the suppressive capacity of Tregs. The mechanisms of this inhibition included arrest of cells in the G0/G1 phase of cell cycle, down-regulation of the transcription factor forkhead box P3, glucocorticoid-induced tumour necrosis factor receptor and the cytotoxic T lymphocyte associated protein 4 as well as inhibition of signaling events through Src and nuclear factor kappaB. Dasatinib showed an inhibitory effect on the proliferation and function of both Tregs and CD4+CD25- T cells at therapeutically relevant concentrations of the drug. Clinical administration of dasatinib might influence not only the graft-versus-leukaemia effect but also the graft-versus-host-disease in patients receiving dasatinib after allogeneic stem cell transplantation and/or donor lymphocytes infusion as the function of both Tregs and effector T cells are hampered in a similar way by dasatinib.

Gene transfer into human CD34+ haematopoietic progenitor cells (HPC) and multi-potent mesenchymal stromal cells (MSC) is an essential tool for numerous in vitro and in vivo applications including therapeutic strategies, such as tissue engineering and gene therapy. Virus based methods may be efficient, but bear risks like tumorigenesis and activation of immune responses. A safer alternative is non-viral gene transfer, which is considered to be less efficient and accomplished with high cell toxicity. The truncated low affinity nerve growth factor receptor (ÄLNGFR) is a marker gene approved for human in vivo application. Human CD34+ HPC and human MSC were transfected with in vitro-transcribed mRNA for ΔLNGFR using the method of nucleofection. Transfection efficiency and cell viability were compared to plasmid-based nucleofection. Protein expression was assessed using flow cytometry over a time period of 10 days. Nucleofection of CD34+ HPC and MSC with mRNA resulted in significantly higher transfection efficiencies compared to plasmid transfection. Cell differentiation assays were performed after selecting ΔLNGFR positive cells using a fluorescent activating cell sorter. Neither cell differentiation of MSC into chondrocytes, adipocytes and osteoblasts, nor differentiation of HPC into burst forming unit erythroid (BFU-E) colony forming unit-granulocyte, erythrocyte, macrophage and megakaryocyte (CFU-GEMM), and CFU-granulocyte-macrophage (GM) was reduced. mRNA based nucleofection is a powerful, highly efficient and non-toxic approach for transient labelling of human progenitor cells or, via transfection of selective proteins, for transient manipulation of stem cell function. It may be useful to transiently manipulate stem cell characteristics and thus combine principles of gene therapy and tissue engineering.

Data regarding the role of mitochondria in arsenic trioxide (As2O3)-induced apoptosis are controversial. We investigated the contribution of caspases and mitochondrial depolarization to As2O3-induced apoptosis in the myeloid cell lines NB-4, HL-60 and U-937. Caspase inhibition reduced the amount of cells with As2O3 (20 micromol/l)-induced mitochondrial depolarization by about 50% in all cell lines. As2O3 also induced dose-dependent phosphatidylserine exposure in cells without depolarized mitochondria. We conclude that caspase activation is of similar importance in As2O3-induced apoptosis in myeloid cell lines as direct mitochondrial targeting and mitochondria are not necessary for caspase activation downstream of mitochondria.

Aim The established variability of HLA-C expression on cell surface, although already investigated in African Americans by Apps et al. Science 2013(1), has not been yet accordingly researched in Caucasians. Furthermore, the possibility that HLA-C expression heterogeneity may be attributed to an overall HLA-Class I expression regulation has not been thus far experimentally addressed either. This work aims at elucidating both issues through actual protein expression analysis by flow-cytometry in 188 German healthy blood donors. Methods 188 buffy-coats provided from the Ulm Blood Donor Centre were used for leucocyte collection in order to determine by flow cytometry the protein expression levels of HLA-C and HLA-Class I on lymphocytes as previously described 1 . For HLA-C and HLA-Class I expression estimation, a DT-9 and an anti-HLA-ABC Antibody were used. Median Intensity Fluorescence (MFI) coefficients were calculated for each HLA-C allotype through implementation of a linear regression model. Results According to our findings, HLA-C03, -C07 and -C08 (MFI: 408, 450 and 481 respectively) were ranked as low-expressed HLA-C antigens contrary to HLA -C12, -C14 and -C01, which were notably higher expressed (MFI: 1261, 1280 and 1322 respectively). In addition, our data on overall HLA-Class I expression levels were suggestive of no direct correlation between HLA-C and HLA-Class I expression levels on cells as: (1) The divergence range of expression levels for HLA-Class I was markedly narrower (MFIs: 450–758 vs 408–1322). (2) Low expressed HLA-C allotypes were found linked with high HLA-Class I expression levels (e.g. C08: 758 for HLA-Class I vs 481 for HLA-C). Conclusions Our HLA-C expression results match significantly those of Apps et al. at least with respect to high-and low-expressed HLA-C antigens, despite the different race of subjects included in the two studies. Moreover, of high interest is our finding regarding the lack of association between HLA-C and HLA-Class I expression, which in turn points to an HLA-C rather than an HLA-Class I specific expression- regulating factor accounting for this marked divergence in HLA-C expression levels. Further investigation on a much greater scale is nevertheless mandatory before final conclusions can be drawn.

Cell therapy using multipotent mesenchymal stromal cells (MSCs) is of high interest in various indications. As the pleiotropic effects mediated by MSCs rely mostly on their unique secretory profile, long-term persistence of ex-vivo-expanded cells in the recipient may not always be desirable. Irradiation is a routine procedure in transfusion medicine to prevent long-term persistence of nucleated cells and could therefore also be applied to MSCs. We have exposed human bone-marrow-derived MSCs to 30 or 60 Gy of γ-irradiation and assessed cell proliferation, clonogenicity, differentiation, cytokine levels in media supernatants, surface receptor profile, as well as expression of proto-oncogenes/cell cycle markers, self-renewal/stemness markers, and DNA damage/irradiation markers. Irradiated MSCs show a significant decrease in proliferation and colony-forming unit-fibroblasts. However, a subpopulation of surviving cells is able to differentiate, but is unable to form colonies after irradiation. Irradiated MSCs showed stable expression of CD73 and CD90 and absence of CD3, CD34, and CD45 during a 16-week follow-up period. We found increased vascular endothelial growth factor (VEGF) levels and a decrease of platelet-derived growth factor (PDGF)-AA and PDGF-AB/BB in culture media of nonirradiated cells. Irradiated MSCs showed an inverse pattern, that is, no increase of VEGF, and less consumption of PDGF-AA and PDGF-AB/BB. Interestingly, interleukin-6 (IL-6) levels increased during culture regardless of irradiation. Cells with lower sensitivity toward γ-irradiation showed positive β-galactosidase activity 10 days after irradiation. Gene expression of both irradiated and nonirradiated MSCs 13-16 weeks after irradiation with 60 Gy predominantly followed the same pattern; cell cycle regulators CDKN1A (p21) and CDKN2A (p16) were upregulated, indicating cell cycle arrest, whereas classical proto-oncogenes, respectively, and self-renewal/stemness markers MYC, TP53 (p53), and KLF4 were downregulated. In addition, DNA damage/irradiation markers ATM, ATR, BRCA1, CHEK1, CHEK2, MDC1, and TP53BP1 also mostly showed the same pattern of gene expression as high-dose γ-irradiation. In conclusion, we demonstrated the existence of an MSC subpopulation with remarkable resistance to high-dose γ-irradiation. Cells surviving irradiation retained their trilineage differentiation capacity and surface marker profile but changed their cytokine secretion profile and became prematurely senescent.

Simple stress or necrotic cell death with subsequent release of damage-associated molecular patterns (DAMPs) is a characteristic feature of most advanced tumors. DAMPs within the tumor microenvironment stimulate tumor-associated cells, including dendritic cells and mesenchymal stromal cells (MSCs). The presence of tumor-infiltrating MSCs is associated with tumor progression and metastasis. Oxidized necrotic material loses its stimulatory capacity for MSCs. As a DAMP, S100A4 is sensitive to oxidation whereas uric acid (UA) acts primarily as an antioxidant. We tested these two biologic moieties separately and in combination for their activity on MSCs. Similar to necrotic tumor material, S100A4 and UA both dose-dependently induced chemotaxis of MSCs with synergistic effects when combined. Substituting for UA, alternative antioxidants (vitamin C, DTT, and N-acetylcysteine) also enhanced the chemotactic activity of S100A4 in a synergistic manner. This emphasizes the reducing potential of UA being, at least in part, responsible for the observed synergy. With regard to MSC proliferation, both S100A4 and UA inhibited MSCs without altering survival or inducing differentiation toward adipo-, osteo-, or chondrocytes. In the presence of S100A4 or UA, MSCs gained an immunosuppressive capability and stably induced IL-10– and IDO-expressing lymphocytes that maintained their phenotype following proliferation. We have thus demonstrated that both S100A4 and UA act as DAMPs and, as such, may play a critical role in promoting some aspects of MSC-associated immunoregulation. Our findings have implications for therapeutic approaches targeting the tumor microenvironment and addressing the immunosuppressive nature of unscheduled cell death within the tumor microenvironment.

International audience; The aim of this study was to assess the immune modulatory properties of human mesenchymal stromal cells obtained from bone marrow (BM-MSCs), fat (ASCs) and cord blood (CB-MSCs) in the presence of a novel hydroxyapatite and tricalcium-phosphate (HA/TCP) biomaterial as scaffold for MSC delivery. In resting conditions, a short-term culture with HA/TCP did not modulate the anti-apoptotic and suppressive features of the various MSC types towards T, B and NK cells; in addition, when primed with inflammatory cytokines, MSC maintained or not on HA/TCP similarlyincreased their suppressive capacities. The long-term culture of BM-MSCs with HA/TCP induced an osteoblast-like phenotype with up-regulation of OSTERIX and OSTEOCALCIN, similarly to what obtained with dexamethasone and, to a higher extent, BMP-4 treatment. MSC-derived osteoblasts did not trigger immune cell activation, but were less efficient than undifferentiated MSCs in inhibiting stimulated T and NK cells. Interestingly, their suppressive machinery included not only the activation of IDO, which plays a central role in T-cell inhibition, but also COX-2 that was not significantly involved in immune modulatory effect of human undifferentiated MSCs. COX-2 is significantly involved in bone healing, suggesting that its induction by HA/TCP could also contribute to the therapeutic activity of MSC for bone tissue engineering.

SummaryThe decline in hematopoietic function seen during aging involves a progressive reduction in the immune response and an increased incidence of myeloid malignancy, and has been linked to aging of hematopoietic stem cells (HSCs). The molecular mechanisms underlying HSC aging remain unclear. Here we demonstrate that elevated activity of the small RhoGTPase Cdc42 in aged HSCs is causally linked to HSC aging and correlates with a loss of polarity in aged HSCs. Pharmacological inhibition of Cdc42 activity functionally rejuvenates aged HSCs, increases the percentage of polarized cells in an aged HSC population, and restores the level and spatial distribution of histone H4 lysine 16 acetylation to a status similar to that seen in young HSCs. Our data therefore suggest a mechanistic role for Cdc42 activity in HSC biology and epigenetic regulation, and identify Cdc42 activity as a pharmacological target for ameliorating stem cell aging.

The receptor for hyaluronic acid-mediated motility (RHAMM) is a tumor-associated antigen in chronic lymphocytic leukemia (CLL). CD8(+) T cells primed with the RHAMM-derived epitope R3, which is restricted by human leukocyte antigen (HLA)-A2, effectively lyse RHAMM(+) CLL cells. Therefore, we initiated a phase I clinical trial of R3 peptide vaccination. Six HLA-A2(+) CLL patients were vaccinated four times at biweekly intervals with the R3 peptide (ILSLELMKL; 300 microg per dose) emulsified in incomplete Freund's adjuvant; granulocyte-macrophage colony stimulating factor (100 microg per dose) was administered concomitantly. Detailed immunological analyses were conducted throughout the course of peptide vaccination. No severe adverse events greater than CTC I degrees skin toxicity were observed. Four patients exhibited reduced white blood cell counts during vaccination. In five of six patients, R3-specific CD8(+) T cells were detected with the corresponding peptide/HLA-A2 tetrameric complex; these populations were verified functionally in four of five patients using enzyme-linked immunosorbent spot (ELISpot) assays. In patients with clinical responses, we found increased frequencies of R3-specific CD8(+) T cells that expressed high levels of CD107a and produced both interferon-gamma and granzyme B in response to antigen challenge. Interestingly, vaccination was also associated with the induction of regulatory T cells in four patients. Thus peptide vaccination in six CLL patients was safe and could elicit to some extent specific CD8(+) T-cell responses against the tumor antigen RHAMM.

Background Nilotinib is a tyrosine kinase inhibitor with high target specificity. Here, we characterized the effects of nilotinib for the first time on CD4+CD25+ regulatory T cells (Tregs) which regulate anti-tumor/leukemia immune responses. Design and Methods Carboxyfluorescein diacetate succinimidyl ester (CFSE) and 5-bromo-2-deoxy -uridine (BrdU) were used to assess the proliferation and cell cycle distribution of Tregs. The expression of the transcription factor forkhead box P3 (FoxP3) and the glucocorticoid-induced tumor necrosis factor receptor (GITR) were measured by flow cytometry. Western blotting analysis was used to detect the effects of nilotinib on the signal transduction cascade of T-cell receptor (TCR) in Tregs. Results Nilotinib inhibited the proliferation and suppressive capacity of Tregs in a dose-dependent manner. However, the production of cytokines secreted by Tregs and CD4+CD25- T cells was only inhibited at high concentrations of nilotinib exceeding the mean therapeutic serum concentrations of the drug in patients. Only high doses of nilotinib arrested both Tregs and CD4+CD25- T cells in the G0/G1 phase and down-regulated the expression of FoxP3 and GITR. In western blotting analysis, nilotinib did not show significant inhibitory effects on TCR signaling events in Tregs and CD4+CD25- T cells. Conclusions These findings indicate that nilotinib does not hamper the function of Tregs at clinical relevant doses, while long-term administration of nilotinib still needs to be investigated.

Despite advances in surgery, radio- and chemotherapy, therapeutic approaches for patients with head and neck squamous carcinoma (HNSCC) need to be improved. Immunotherapies eliciting tumor specific immune responses might constitute novel treatment options. We therefore investigated the expression and immunogenicity of two tumor-associated antigens (TAA) the receptor for hyaluronic acid mediated motility (RHAMM) and carboanhydrase IX (G250/CAIX) in HNSCC patients. Twenty-two HNSCC samples were examined for the expression of RHAMM and G250 by Western blotting and immunohistochemistry, 14/22 samples were tested for HLA-A2 expression by flow cytometry. For 8/22 samples single tumor-cell suspensions were generated, and mixed lymphocyte peptide cultures (MLPC) were performed to evaluate the frequencies of cytotoxic T cells specifically recognizing RHAMM and G250 using Tetramer staining/multi-color flow cytometry and enzyme linked immunosorbent spot (ELISPOT) assays. RHAMM and G250 were expressed in 73 and 80% of the HNSCC samples at the protein level. A co-expression of both TAAs could be detected in 60% of the patients. In 4/8 HLA-A2 + patients, 0.06-0.13% of CD8 + effector T cells recognized Tetramers for RHAMM or G250 and secreted IFNy and granzyme B in ELISPOT assays. RHAMM and G250 are expressed at high frequency and high protein level in HNSCCs and are recognized by cytotoxic CD8 + effector T cells. Therefore both TAAs constitute interesting targets for T cell based immunotherapies for HNSCC.

Congenital dyserythropoietic anemias (CDAs) are phenotypically and genotypically heterogeneous diseases(1-4). CDA type II (CDAII) is the most frequent CDA. It is characterized by ineffective erythropoiesis and by the presence of bi- and multinucleated erythroblasts in bone marrow, with nuclei of equal size and DNA content, suggesting a cytokinesis disturbance(5). Other features of the peripheral red blood cells are protein and lipid dysglycosylation and endoplasmic reticulum double-membrane remnants(4,6). Development of other hematopoietic lineages is normal. Individuals with CDAII show progressive splenomegaly, gallstones and iron overload potentially with liver cirrhosis or cardiac failure. Here we show that the gene encoding the secretory COPII component SEC23B is mutated in CDAII. Short hairpin RNA (shRNA)-mediated suppression of SEC23B expression recapitulates the cytokinesis defect. Knockdown of zebrafish sec23b also leads to aberrant erythrocyte development. Our results provide in vivo evidence for SEC23B selectivity in erythroid differentiation and show that SEC23A and SEC23B, although highly related paralogous secretory COPII components, are nonredundant in erythrocyte maturation.

Human severe combined immunodeficiencies (SCID) are phenotypically and genotypically heterogeneous diseases. Reticular dysgenesis is the most severe form of inborn SCID. It is characterized by absence of granulocytes and almost complete deficiency of lymphocytes in peripheral blood, hypoplasia of the thymus and secondary lymphoid organs, and lack of innate and adaptive humoral and cellular immune functions, leading to fatal septicemia within days after birth. In bone marrow of individuals with reticular dysgenesis, myeloid differentiation is blocked at the promyelocytic stage, whereas erythro- and megakaryocytic maturation is generally normal. These features exclude a defect in hematopoietic stem cells but point to a unique aberration of the myelo-lymphoid lineages. The dramatic clinical course of reticular dysgenesis and its unique hematological phenotype have spurred interest in the unknown genetic basis of this syndrome. Here we show that the gene encoding the mitochondrial energy metabolism enzyme adenylate kinase 2 (AK2) is mutated in individuals with reticular dysgenesis. Knockdown of zebrafish ak2 also leads to aberrant leukocyte development, stressing the evolutionarily conserved role of AK2. Our results provide in vivo evidence for AK2 selectivity in leukocyte differentiation. These observations suggest that reticular dysgenesis is the first example of a human immunodeficiency syndrome that is causally linked to energy metabolism and that can therefore be classified as a mitochondriopathy.

Objective To investigate the inhibitory effects of dasatinib on proliferation, function, and signaling events on CD8 + T cells. Materials and Methods Carboxyfluorescein diacetate succinimidyl ester and 5-bromo-2-deoxyuridine were used to detect proliferation and cell cycle of CD8 + T cells treated with dasatinib, respectively. Frequency and function of viral and leukemia-antigen–specific CD8 + T cells from healthy donors were measured by tetramer staining and ELISPOT assay. Western blotting analysis was performed to detect T-cell receptor (TCR), nuclear factor k appa B (NF-κB) and Src signaling events in T cells treated with dasatinib or imatinib. Results Dasatinib inhibited proliferation of CD8 + T cells in a dose-dependent manner, which was associated with lower secretion of interferon-gamma and granzyme B, as well as with arrest of CD8 + T cells in the G 0 /G 1 phase of cell cycle. Inhibition of CD8 + T cells was proven for blood samples from a patient under dasatinib medication when compared with their T-cell status without dasatinib. Western blotting confirmed that these effects were mediated through downregulation of the phosphorylation level of molecules from the TCR and the NF-κB signaling transduction cascade. Dasatinib proved to be more potent than imatinib on Src and TCR signaling events in Jurkat T cells. Conclusion Our study demonstrated that dasatinib impaired proliferation and function of CD8 + T cells via TCR and NF-κB signaling events without inducing apoptosis. Therefore, dasatinib might alter the graft-vs-leukemia effect and the graft-vs-host disease after allogeneic stem cell transplantation sustained by CD8 + T cells. Dasatinib might also be used as a novel immunosuppressant agent.

The novel selective BCR-ABL Breakpoint cluster region--Abelson murine leukemia viral oncogene homolog 1 (BCR-AML) inhibitor nilotinib (AMN107) is a tyrosine kinase inhibitor that is more potent against leukaemia cells in vitro than imatinib. As nilotinib might be used in the context of allogeneic stem cell transplantation where CD8+ T lymphocytes play a pivotal role in the graft-versus-leukaemia (GVL) effect, we investigated effects of nilotinib on this lymphocyte subpopulation. Nilotinib inhibits phytohemagglutinin (PHA)-induced proliferation of CD8+T lymphocytes in vitro at therapeutically relevant concentrations (0.5-4 microM). The inhibition of CD8+ T lymphocytes specific for leukaemia or viral antigens through nilotinib was associated with a reduced expansion of antigen peptide specific CD8+ T lymphocytes and with a decreased release of interferon-gamma and granzyme B by these cells as analysed by flow cytometry and enzyme-linked immunospot (ELISPOT) assays. The inhibitory effect caused by nilotinib was two times stronger than by imatinib. These effects were mediated through the inhibition of the phosphorylation of ZAP-70, Lck and ERK 1/2 and the NF-kappaB signalling transduction pathway. Taken together, we observed a strong suppressive impact of nilotinib on the CD8+ T lymphocyte function which should be considered carefully in the framework of allogeneic stem cell transplantation or other T cell based immunotherapies.

The tyrosine kinase inhibitor imatinib has been reported to inhibit CD8+ T lymphocytes. Little is known about its effects on CD4+CD25+ regulatory T cells (T(reg) cells) which might regulate the graft-vs.-leukemia (GVL) reaction after allogeneic stem cell transplantation (allo-SCT) and donor lymphocyte infusion (DLI). This is of particular interest in patients with relapse of chronic myeloid leukemia (CML) after allo-SCT, as the two therapeutical options DLI and imatinib might interact reversely. Here, we demonstrate that the proliferation of CD4+CD25+ T(reg) cells and their production of IL-10, TGF-beta1 and granzyme B as markers of activation were significantly down-regulated by imatinib in a dose-dependent manner. In addition, the expression of surface CD69, both surface and intracellular GITR, FoxP3, CD152 (CTLA) of activated CD4+CD25+ T(reg) cells were inhibited by imatinib in a dose-dependent manner. In light of these findings, clinical administration of imatinib might not result in a reduction of the GVL effect on CML patients receiving imatinib after allo-SCT and/or DLI or other CD8+ T lymphocyte based immunotherapies as the function of CD8+ cytotoxic T lymphocytes and CD4+CD25(hi) Treg cells is hampered in a similar way by imatinib.

The proteins of blood group systems are expressed on red blood cells (RBC) by definition. We searched nucleotide databases of human expressed sequence tags (EST) to collate the distribution of 22 distinct membrane proteins in cells and tissues other than RBC. The documented blood group genes are: MNS, Rh, Lutheran, Kell, Duffy, Kidd, Diego, Yt, Xg, Scianna, Dombrock, Colton, Landsteiner-Wiener, Kx, Gerbich, Cromer, Knops, Indian, Ok, Raph, John-Milton-Hagen and Gill. The genes were grouped according to their overall and their relative expression in embryo and adults. We describe the distribution of EST in cells, tissues and cell lines with a focus on non-RBC tissues.

Telomere length has been linked to disease stage and degree of (pan-)cytopenia in patients with bone marrow failure syndromes. The aim of the current study was to analyze the impact of replicative stress on telomere length in residual glycosylphosphatidylinositol-positive (GPI+) versus GPI– hematopoiesis in patients with paroxysmal nocturnal hemoglobinuria (PNH). Peripheral blood granulocytes from 16 patients and 22 healthy individuals were analyzed. For this purpose, we developed proaerolysin flow-FISH, a novel methodology that combines proaerolysin staining (for GPI expression) with flow-FISH (for telomere length measurement). We found significantly shortened telomeres in GPI– granulocytes (mean ± SE: 6.26 ± 0.27 telomere fluorescence units [TFU]), both compared with their GPI+ counterparts (6.88 ± 0.38 TFU; P = .03) as well as with age-matched healthy individuals (7.73 ± 0.23 TFU; P < .001). Our findings are in support of a selective growth advantage model of PNH assuming that damage to the GPI+ hematopoietic stem-cell (HSC) compartment leads to compensatory hyperproliferation of residual GPI–HSCs.

The potency of arsenic trioxide (As 2 O 3 ) as chemotherapeutic agent is under investigation in various clinical trials. As 2 O 3 was shown to be a potent inductor of apoptosis, and several publications describe the involvement of caspases, reduction of mitochondrial membrane potential and modulation of intracellular glutathione level. However, little is known about the involvement of membrane bound cell death receptors. We investigated the role of CD95 and CD95L in As 2 O 3 mediated apoptosis in various lympho-haematopoietic cell lines. Basal CD95-expression did not correlate with sensitivity to As 2 O 3 and incubation with As 2 O 3 did not alter CD95-expression. We therefore chose two CD95 positive cell lines (CCRF-CEM and Jurkat) to analyse a potential activation of this pathway. We were able to induce apoptosis in these CD95 positive cell lines with activating anti-CD95 antibodies and could block induction of apoptosis by inhibitory anti-CD95 antibodies. In contrast we were not able to block As 2 O 3 -induced apoptosis by inhibitory anti-CD95 antibodies. We could block additive effects of arsenic trioxide and an apoptosis-inducing anti-CD95 antibody against CD95 to levels of arsenic trioxide alone using an inhibitory anti-CD95 antibody. Thus, our data provide no evidence for a role of the CD95L/CD95 pathway in As 2 O 3 -induced apoptosis.

Objective. Mitochondrial membrane potential (Δψ m ) and intracellular Ca 2+ play a crucial role in growth and differentiation in hemopoiesis. Some potassium channel openers such as diazoxide have the capacity to elevate cytosolic Ca 2+ and depolarize mitochondria in cardiomyocytes. To clarify if such substances have effects on hemopoietic cells we investigated the commonly used opener of the mitoK ATP channel, diazoxide, and the opener of BK channels, NS1619, for their potential to depolarize mitochondria, elevate cytosolic Ca 2+ , and induce apoptosis in the hemopoietic CD34 + cell line KG-1a. Methods. Fluorescent probes were used to investigate Δψ m , free Ca 2+ , and apoptosis (JC-1, fluo-3-AM and annexin V–FITC) by flow cytometry. To measure Δψ m with JC-1 in glycoprotein P + cells we used an improved dye loading technique with verapamil. Results. NS1619 induced stronger dose-dependent mitochondrial depolarizations than diazoxide. Depolarization was independent from caspase activation and could also be induced when the driving force for K + out of cells was near 0 mV. In Ca 2+ free solutions NS1619 induced stronger Ca 2+ elevations than diazoxide and elevated Ca 2+ also after Ca 2+ depletion of the endoplasmatic reticulum with caffeine. NS1619 did not enhance the Ca 2+ elevation induced by ionophores (CCCP, valinomycin) that depolarize mitochondria. Both agents were weak inducers of apoptosis. Conclusion. Diazoxide has similar effects in CD34 + cells as described for muscle or nerve cells. In accordance to the single channel conductance of mitoK ATP and BK channels, NS1619 is a more potent inducer of mitochondrial depolarization than diazoxide. NS1619 releases Ca 2+ from an intracellular pool that is insensitive to caffeine but depends strongly on Δψ m .

Leukemic stem cells (LSC) might be the source for leukemic disease self-renewal and account for disease relapse after treatment, which makes them a critical target for further therapeutic options. Treatment for acute myeloid leukemia (AML) patients became more effective, yet relapse rates are still high. Immunotherapeutic approaches might overcome the immune escape mechanisms of LSC and might be a therapeutic option. Leukemia-associated antigens (LAA) represent targets that are recognized by cytotoxic T-lymphocytes (CTL) and might be useful for specific immunotherapy. We enriched the LSC containing fraction as CD34+CD38- cells (called LSC-EF) of 20 AML patients using FACS, analyzed expression patterns of LAA in LSC-EF and compared them to patterns in enriched HSC und bulk AML cells by microarray expression analysis and qRT-PCR. In immunoassays, we analysed the functional inhibition of LCS in colony forming assays (CFU) of AML patients by stimulated T cells. We detected a high expression of several LAA in LSC-EF. PRAME (p = 0.0085), RHAMM (p = 0.03), WT1 (p = 0.04) and Proteinase 3 (p = 0.04) showed significant differential expression in LSC-EF compared to HSC. Survivin (p = 0.7), HAGE (p = 0.5), SSXIP2 (p = 0.4) and Aurorakinase A (p = 0.7) did not indicate a significant differential expression. BAGE does not seem to be an ideal candidate as it is significantly higher expressed on normal HSC (p = 0.0056). Further, we evaluated the expression differences of LSC-EF compared to leukemic bulk. PRAME, RHAMM and WT1 qualified as interesting potential targets as they are lower expressed on leukemic bulk than on LSC-EF. In contrast, Proteinase 3 indicates a higher expression on leukemic bulk but lower in LSC-EF. qRT-PCR confirmed our array data. In immunoassays, T cells stimulated against LAA indicated a significant inhibition of CFUs in AML patient samples. PRAME, RHAMM and WT1 showed good immunogenic responses with CTL recognition rates in a range of 58-83%. PRAME hereby proved as most effective using two different patient samples, with a reduction of 83% colonies (p = 0.004). WT1 shows a significant reduction of 74% (p = 0.05) and RHAMM of 58% colonies (p = 0.2). Taken together, several LAA are significantly expressed on the LSC-EF, whereas PRAME, RHAMM and WT1 seemed most promising as these LAA are differentially expressed compared to normal stem cells and stimulation of cytotoxic T cells against these LAAs inhibit LSC in CFU assays. Disclosures No relevant conflicts of interest to declare.

Acquired somatic mutations of the PIG-A gene lead to deficient expression of glycosyl-phosphatidyl-inositol-anchored proteins (GPI-AP) by haematopoietic cells and play a causative role in the pathogenesis of paroxysmal nocturnal haemoglobinuria (PNH). However, PIG-A mutations do not explain how the defective PNH clone can expand. It was hypothesized that a selection process conferring a relative advantage to the GPI-AP-deficient population is required. Since GPI-AP-deficient cells are also detectable in a substantial proportion of patients with otherwise typical aplastic anaemia (AA), the mechanisms inducing bone marrow failure might selectively spare the GPI-deficient cells. In order to examine the growth characteristics of GPI-AP-deficient cells in more detail, we performed repeated analyses of GPI-AP expression on peripheral blood cells in 41 patients with AA. We observed four patterns of the course of GPI-AP-deficient populations: (1) 13 patients showed normal expression of GPI-AP in the first analysis and in at least two follow-up studies at a median time of 709 days after the first analysis. (2) Secondary evolution of a GPI-AP-deficient population was a rare event. Only 4 patients with initially normal GPI-AP expression developed a GPI-AP-deficient population during follow up after immunosuppressive treatment. (3) Persistence of GPI-AP-deficient cells was observed in 16 patients during a median follow-up time of 774 days. However, in some patients, the size of the GPI-AP-deficient population increased substantially. (4) Disappearance of a GPI-AP-deficient population was observed in 8 patients. The time course of GPI-AP expression in relation to the treatment suggests that therapeutic interventions might modulate the ratio of normal versus GPI-AP-deficient haematopoiesis. Overall, these data argue against an ‘absolute growth advantage’ of GPI-AP-deficient cells. Our data are consistent with the hypothesis that haematopoietic failure caused by damage to normal haematopoiesis allows the outgrowth of a GPI-AP-deficient population. Thus, in at least some patients GPI-AP-deficient cells might pre-exist at a very low percentage and replace haematopoiesis after an insult to the normal cells.

Treatment of acute myeloid leukemia (AML) patients became more effective, yet the relapse rate is still high and cure rate still low. Different therapeutic approaches, based on molecular targeting are offering new treatment strategies using markers like FLT3, NPM1, cKIT and DNMT3A. Many others are currently under investigation. Leukemic stem cells (LSC) might be the source for leukemic disease self-renewal and account for disease relapse after treatment. Therefore LSC represent a critical target for further therapeutic options. AML with mutated nucleophosmin (NPM1) gained attention because of its distinctive molecular, clinical, and prognostic features. NPM1 mutation is also an interesting target for specific immunotherapy (Greiner et al., Blood 2012), however LSC of this new entity have not been completely characterized. Differentially expressed genes might influence molecular and immunological relevant pathways which could have an impact on the better overall survival of the mutated patients. In this study, we were interested in expression differences of the LSC enriched cell fraction descendent of NPM1wt and NPM1mut primary AML patients. We suggest that expression differences between the patients groups could be a factor for the better overall survival of NPM1mut patients. In addition we aimed to study new targets on NPM1mut LSC for new therapeutical purposes. We enriched the CD34+CD38- fraction of primary AML peripheral blood mononuclear cells (PBMC), by Fluorescence-activated cell sorting (FACS) and Magnetic-activated cell sorting (MACS), comparing both methods in efficiency and feasibility. We chose FACS for further enrichment assays, as it resulted in a mean purity of 92% vs 88% using MACS, and a higher cell number after sorting (9% more) in the first pilot trials. We sorted 21 AML patient samples; 12 NPM1wt and 9 NPM1mut. We also enriched healthy donor samples for HSC purification using FACS, in order to compare expression levels. We showed that enriched CD34+CD38- cells in NPM1mut AML samples harbor cytoplasmic NPM1 via immunocytochemical staining, indicating that these cells belong to the leukemic clone. The cell number and RNA quality was sufficient for further Microarray studies in which we analysed the CD34+CD38- enriched compartments descendent from NPM1mut and NPM1wt patients. Those showed significant differences in gene expression patterns which noticeably are immunologically coined, for example: immunoglobulin superfamily, member 10 (p = 0.0003405; fold change: 6.22) and the interleukin 12 receptor, beta 1 (p = 0.000834, fold change: 1.87). This impression was confirmed by pathway analysis indicating deregulation of pathways like the NO2-dependent IL 12 Pathway in NK cells and the Th1/Th2 Differentiation and the Platelet Amyloid Precursor Protein Pathway. Functional assays, confirming the biological importance of these factors have been performed for example an assay to test the effect of IL12 on AML cellines. Furthermore we screened our data for new potential therapeutic target structures, specifically on enriched CD34+CD38- cells of NPM1mut patients, comparing the expression level of target genes to NPM1wt CD34+CD38- cells, and the expression level on HSC. Amongst others, our most promising candidates are SERPINA1 (p = 0.0062344, fold change: 14.32), OSCAR (p = 6.11E-05, fold change: 9.03) and several further interesting genes. These genes could be used in order to target CD34+CD38- cells of NPM1mut patients in a therapeutic manner. Taken together, we successfully enriched the CD34+CD38- fraction of NPM1mut and NPM1wt AML patients and performed Microarray analysis, unraveling gene expression differences between the two patients groups, which seem to be of an immunological nature. This could be a factor, amongst others, for the better overall survival of the NPM1mut patient group. Furthermore we described new potential targets structures on CD34+CD38- cells for NPM1mut patient’s treatment. Disclosures: No relevant conflicts of interest to declare.

Bone is one of the most frequently transplanted tissues, with allografts and autografts accounting for more than 80% of total grafts. Synthetic biomaterials in association with autologous or allogeneic mesenchymal stromal cells (MSCs) represent a valid alternative in orthopaedic and maxillofacial surgery. Aim of REBORNE consortium is to perform clinical trials using standardized protocols based on advanced biomaterials and MSCs. Aim of our Unit was to assess MSC immune modulatory properties in presence of a novel biomaterial consisting of hydroxyapatite and tricalcium-phosphate (HA/TCP, Biomatlante, France) as scaffold for MSC delivery. We assessed immune modulatory properties, in terms of immunophenotype, inhibitory and anti-apoptotic effects, of MSCs of different origin when associated with the HA/TCP biomaterial, including bone marrow-derived mesenchymal stromal cells (BM-MSCs), adipose-derived MSCs (ASCs) and cord blood-derived MSCs (CB-MSCs). The culture of all MSCs with HA/TCP, did not modulate the anti-apoptotic and suppressive features of all MSCs toward sorted-T, B and NK lymphocytes as compared to standard culture setting. When exposed to inflammatory cytokines, such as IFN-γ and TNF-α, all MSCs were induced to acquire the suppressive phenotype, characterized by MHC-1 and CAM molecules up-regulation, and de novo expression of HLA-DR molecules. The long-term culture of BM-MSCs with HA/TCP induced an osteoblast-like phenotype, as indicated by the up-regulation of osterix and osteocalcin transcription. The differentiation process is promoted in all MSC types, but especially in BM-MSCs, by dexamethasone and, to a higher extent, BMP-4 treatment. In view of using MSCs for advanced therapies in allogeneic setting, we evaluated the immunogenicity and immune modulatory features of pre-differentiated MSCs in association with HA/TCP towards both innate and adaptive immune cells, as well as the molecular pathways involved in MSC-mediated immune regulation. MSC-derived osteoblasts did not induce immune cell activation, as demonstrated by co-culture of unstimulated immune effector cells with pre-differentiated MSCs. We found a lower suppressive capability of pre-differentiated MSCs towards stimulated T and NK cells. However, some inhibitory effects could be exerted by BMP-4 treated-MSCs, and could be related to the presence of undifferentiated MSCs in culture, which could inhibit lymphocyte proliferation. The balance between the number of bone depositing osteocyte-like MSCs and immunosuppressive undifferentiated MSCs could be useful, in vivo, to promote bone healing and to reduce local inflammation, respectively. We then investigated in pre-differentiated MSCs the molecular mechanisms involved in the inhibition of T cell proliferation, by interfering with IDO and COX-2 activation. We found that pre-differentiated MSCs switched on their suppressive machinery by activating both IDO, which plays a central role in immune regulation, and COX-2, whose role is not significant in undifferentiated MSCs. COX-2 is produced rapidly as inflammation mediator after fracture, and recent data highlighted the role of COX-2 in improving fracture healing. In conclusion, this study increases the knowledge on MSC biology and gives pre-clinical data concerning the use of allogeneic MSC in combination with ceramic scaffolds to treat bone defects. Disclosures: No relevant conflicts of interest to declare.

Background Mesenchymal stromal cells (MSC) have gained importance in tissue repair, tissue engineering and in immunosupressive therapy during the last years. Due to the limited availability of MSC in the bone marrow, ex vivo amplification prior to clinical application is requisite to obtain therapeutic applicable cell doses. Translation of preclinical into clinical-grade large-scale MSC expansion necessitates precise definition and standardization of all procedural parameters including cell seeding density, culture medium and cultivation devices. While xenogeneic additives such as fetal calf serum are still widely used for cell culture, its use in the clinical context is associated with many risks, such as prion and viral transmission or adverse immunological reactions against xenogeneic components. Methods and Findings We established animal-free expansion protocols using platelet lysate as medium supplement and thereby could confirm its safety and feasibility for large-scale MSC isolation and expansion. Five different GMP-compliant standardized protocols designed for the safe, reliable, efficient and economical isolation and expansion of MSC was performed and MSC obtained were analyzed for differentiation capacity by qPCR and histochemistry. Expression of standard MSC markers as defined by the International Society for Cellular Therapy as well as expression of additional MSC markers and of various chemokine and cytokine receptors was analysed by flow cytometry. Changes of metabolic markers and cytokines in the medium were addressed using the LUMINEX platform. Conclusions The five different systems for isolation and expansion of MSC described in this study are all suitable to produce at least 100 millions of MSC, which is commonly regarded as a single clinical dose. Final products are equal according to the minimal criteria for MSC defined by the ISCT. We showed that chemokine and integrin receptors analyzed had the same expression pattern, suggesting that MSC from either of the systems show equal characteristics of homing and adhesion.

Abstract 3671 Poster Board III-607 For effective elimination of malignant cells by specific T cells a co-activation of CD4- and CD8-positive T cells might be important. We performed two RHAMM-R3 peptide vaccination trials using 300μg and 1000μg for patients with AML, MDS and multiple myeloma overexpressing RHAMM. Similar mild toxicity of both cohorts was found, only mild drug-related adverse events were observed such as erythema and induration of the skin. In the 300μg cohort we detected in 7/10 (70 %) patients specific immune responses and also positive clinical effects in 5/10 (50 %) patients. In the high dose peptide vaccination trial (1000μg peptide) 4/9 (44 %) patients showed positive immune responses. These patients showed an increase of CD8+RHAMM-R3 tetramer+/CD45RA+/CCR7-/CD27-/CD28- effector T cells and an increase of R3-specific CD8+ T cells. In the higher peptide dose cohort three patients showed positive clinical effects. However, higher doses of peptide do not improve the frequency and intensity of immune responses in this clinical trial and might induce immune tolerance. In this work, we investigated the co-existence of serological immune responses against RHAMM detected by a RHAMM-specific ELISA of patients with AML, MDS and multiple myeloma treated in these two peptide vaccination trials. We correlated these results to specific T cell responses of CD8-positive T cells measured by ELISpot assays for interferon gamma and Granzyme B, tetramer staining and chromium release assays. Moreover, these results were compared to the frequency of regulatory T cells. 4/19 patients have a positive serological immune response in ELISA assay, all of these patients developed also strong specific CD8-positive T cell responses during peptide vaccination detected by ELISpot assays and tetramer staining. As expected, peptide vaccination did not result in the induction of humoral immune responses. In further ELISA assays we measured IL-2 and IL-10 levels in the sera of the patients before and three weeks after four vaccinations. While IL-10 levels remained at a rather low level over the time of vaccination, we detected an increase of IL-2 up to the five-fold of the initial levels in four of ten patients. Moreover, we performed a proteome array to detect cytokine and chemokine regulation in sera of patients vaccinated in these two trials during and after RHAMM-R3 peptide vaccination. 36 cytokines, chemokines and acute phase proteins were measured and both cohorts vaccinated with different peptide doses were compared. Taken together, RHAMM-R3 peptide vaccination induced both immunological and clinical responses. Co-existence of immune responses of CD4-positive T cells against the target RHAMM seems to be important for an induction of strong immune responses of CD8-positive T cells. Disclosures: No relevant conflicts of interest to declare.

Introduction: Eculizumab is a humanized monoclonal antibody inhibiting the cleavage of complement factor C5 and preventing terminal complement activation. Therapy with eculizumab leads to a highly significant reduction of complement-mediated intravascular hemolysis and related morbidities including thromboembolic events in Paroxysmal Nocturnal Hemoglobinuria (PNH). It is a new targeted, disease-modifying treatment of PNH. In a placebo-controlled, double-blind randomized study of eculizumab more than 50% of patients (pts) achieved transfusion independence with the remaining pts showing a 44% reduction in the number of red blood cell (RBC) units transfused. In this study we analyzed the proportion of cells with deficiency of GPI-anchored proteins, i.e. PNH cell populations, during eculizumab therapy. Furthermore, we examined a potential mechanism to explain residual hemolysis in some pts despite complete blockade of the terminal complement cascade. Methods: We performed flow cytometric analysis of GPI-anchored proteins, measured levels of hemolysis (LDH), direct bilirubin, hemoglobin and ferritin, and carried out a direct antiglobulin test in samples from 15 (7 female, 8 male) PNH pts during eculizumab therapy. To identify PNH cells, flow cytometric analyses of CD58/CD59 on reticulocytes and erythrocytes, CD66b/CD24/CD16 on granulocytes as well as CD14/CD48 on monocytes were performed. For comparison, the direct antiglobulin test was also performed in 22 (11 female, 11 male) PNH pts without eculizumab therapy. Results: Flow cytometric results of the 15 PNH pts before eculizumab (baseline) and at the time of latest follow-up during eculizumab were compared: GPI-deficient erythrocyte population doubled (29.3% +/−19.3% vs. 56.9% +/−24.0%). The proportion of GPI-deficient reticulocytes (79.1% +/−6.8% vs. 84.6% +/−8.7%), granulocytes (87.5% +/−9.7% vs. 85.5% +/−12.4%) and monocytes (79.0% +/−20.6% versus 73.6%+/−16.2%) did not change significantly. We observed a mean decrease in LDH from 2802 U/l +/− 1015 U/l to 240 U/l +/− 62 U/l; while total bilirubin was stable (47.2 +/− 33.3 μmol/l versus 45.0 +/− 27.8 μmol/l), direct bilirubin showed a threefold increase (3.2 +/− 3.2 μmol/l versus 9.6 +/− 2.4 μmol/l). An increase of ferritin levels was also observed (270 +/− 609 ng/ml versus 651 +/− 652 ng/ml). We performed a direct antiglobulin test in the control group of 22 pts not receiving eculizumab therapy and in 12 pts that received eculizumab. 10 of the 12 pts were tested before and during eculizumab therapy. Only three of all 34 pt who had not received eculizumab at time of antiglobulin test showed a positive antiglobulin test with polyspecific antiglobulin serum, two of them with monospecific anti-IgG and one of them was positive with monospecific anti-C3d. In contrast, all but one of the 12 pts during eculizumab therapy reacted positive with polyspecific antiglobulin serum and monospecific anti-IgG and anti-C3d; in addition, one pt was positive with anti-C3c. The only patient with a negative antiglobulin test during eculizumab therapy was treated for PNH-related thromboembolic events without having transfusion dependent hemolytic anemia. Two of the 12 pts had anti-erythrocytic allo-antibodies (anti-D, -C, -E, -Lua, and -Kpa) before initiation of eculizumab therapy and one of them had additional warm auto-antibodies. Conclusions: 1) A positive direct antiglobulin test (due to C3d loading of PNH RBC) seems to be a consistent finding during eculizumab therapy, which has therefore to be taken into account as a new differential diagnosis of a positive direct antiglobulin test. 2) Eculizumab does not block the early stages of complement activation and therefore C3 cleavage products may occur and bind to CD55/CD59-deficient RBC. The inhibition of terminal membrane attack complex formation by eculizumab allows the survival of these cells which otherwise would undergo a rapid intravascular hemolysis due to C5b-9 formation. 3) The endogenous population of GPI–anchored protein deficient RBC increases during eculizumab therapy. 4) Our data are preliminary and need to be confirmed in larger patient groups: For this purpose, we recommend the monitoring of signs of extravascular hemolysis and ferritin during eculizumab therapy.

Cytomegalovirus (CMV) reactivation constitutes a serious complication after allogeneic peripheral blood stem cell transplantation (PBSCT). The frequency of CMVpp65 specific CD8+ T cells is pivotal for the clearance of CMV. CMVpp65 specific CD8+ T cell frequencies can be measured using tetra-, penta- and streptamer technologies, streptamers can also be applied therapeutically. In donors, these frequencies might allow us to define the best available donor in addition to the mere serostatus. In the present study we investigated the specificity and sensitivity of all three methods and compared the results to the serostatus. A therapeutical application, i.e. an adoptive transfer of CMV specific CD8+ T cells selected by streptamer technology to a patient with acute lymphatic leukemia suffering from life-threatening CMV antigenemia after allogeneic PBSCT was performed. 23 samples from CMV seropositive healthy volunteers (HV) and 10 samples from CMV seropositive patients before and after allogeneic stem cell transplantation (all HLA-A2 or -B7 positive) were analyzed with tetra-, penta- or streptamer conjugated to PE by flow cytometry. Our lab took part in an inter-lab CMV multimer assay including 20 European countries in the framework of www.kimt.de. For the adoptive T cell transfer a donor leukapheresis was performed followed by an HLA-B7 CMVpp65 streptamer positive selection. The patient received 2×10E5 CMV specific CD8+ T cells per kg body weight as a single transfusion. Optimal amounts of HLA-A2 multimers to stain a pellet of 10E6 cells were 0.44 mcg tetramer, 0.15 mcg pentamer and 0.2 mcg MHC/0.3 mcg streptactin complex. Surprisingly, only in 48% (11/23) seropositive HV CD8+ multimer+ T cells could be detected. The ALL patient developed a foscarvir resistant CMV antigenemia with a maximum of 959/500,000 CMVpp65 positive cells. After a switch to ganciclovir/valganciclovir and an adoptive transfer of CMV specific T cells, the antigenemia was cleared. Valganciclovir was discontinued, but CMV antigenemia remained controlled. The frequency of CMVpp65 specific CD8+ T cells increased dramatically from 0.0% till 19.8%. All of these T cells were donor derived as demonstrated by small tandem repeat (STR) analysis. The patient did not develop signs of CMV disease at any time point. This study demonstrates the power of multimer staining to define appropriate donors for transplantation. Donors should be screened for their CMVpp65 specific CD8+ T cell frequency. All three multimer technologies can be used yielding similar results. The streptamer technology additionally offers the advantage to select CMVpp65 specific CD8+ T cells at the GMP level for adoptive T cell transfer and can induce long-lasting CD8+ T cell responses effectively clearing even a high virus load.

Background: For CML/ALL patients with refractory disease or at relapse after allogeneic stem cell transplantation (allo-PBSCT), one might administer tyrosine kinase inhibitors (TKIs) like imatinib (Glivec), nilotinib (Tasigna) and dasatinib (Sprycel), or donor lymphocyte infusions (DLIs). TKIs will inhibit the proliferation of CML progenitor cells, but might also hamper the graft-versus-leukemia (GVL) effect considered to be crucial for the eradication of the disease. Moreover, CD8+ T cells specific for cytomegalovirus (CMVpp65) might be impaired. Methods: Imatinib, nilotinib and dasatinib were added at concentrations of 0–20 μM, 0–4 μM and 0–50 nM respectively to proliferation assays of Tregs and CD8+ T cells. Mixed lymphocyte peptide cultures (MLPCs) were performed with peptides derived from influenza matrix protein (IMP), CMVpp65 as a viral antigen and the receptor for hyaluronic acid mediated motility (RHAMM-R3) as a leukemia-associated antigen. CD8+ T cells from these MLPCs from healthy donors and patients with CML after allo-PSCT by tetramer staining/multi-color flow cytometry and enzyme linked immunosorbent spot (ELISPOT) assays, as well as Tregs after 3 days of culture with anti-CD3 and anti-CD28. Activity of T cells from the peripheral blood of patients under dasatinib and after withdrawal of dasatinib. Western blots (WBs) for T cell receptor (TCR) related molecules and NFkB were performed. Results: The release of interferon gamma and granzyme B by CD8+ HLA-A2/tetramer+effector T cells specific for IMP, CMVpp65 and RHAMM-R3 was inhibited by all TKIs in a dose-dependent fashion and correlating to the time of TKI exposure. The inhibition was reversible after removal of the drugs from the MLPC. The proliferation and function of Tregs were also significantly inhibited by TKIs in a dose-related fashion. In WBs, TKIs decreased the expression of ZAP70, Lck and Akt, as well as NFκB p65/p100/p105 and c-Rel. T cell activity was impaired when TKIs were clinically administered. The potency of T cell inhibition was imatinib: nilotinib: dasatinib = 1:2:40 under therapeutical serum respectively culture medium levels (2 μM:1 μM: 25 nM). Conclusion: When administering TKIs to patients after allo-PBSCT, the inhibition of both CD8+ and Tregs must be taken into consideration with respect to GVL and anti-viral T cell response. Inhibition of CD8+ T lymphocytes was partially reversible after removal of TKIs from the cultures. Using western blotting analysis, we found that these effects are mediated at least in part by down-regulating the levels of phosphorylation of TCR and NF-κB family members.

Most patients with AML, MDS, MM and chronic lymphatic leukemia (CLL) express the receptor for hyaluronic acid mediated motility (RHAMM/CD168) on their tumor cells. We characterized RHAMM/CD168 as a leukemia-associated antigen (LAA) eliciting both humoral and cellular immune responses in patients with different hematological malignancies. CD8 positive T cells primed with the RHAMM/CD168-derived peptide R3 (ILSLELMKL) were able to lyse autologous AML blasts expressing this LAA. Therefore, we initiated a phase I/II R3 peptide vaccination to induce immunological and hematological responses for patients with AML, MDS or MM overexpressing RHAMM/CD168. Patients were included with positive RHAMM/CD168 expression but with a limited tumor load. At a biweekly interval, RHAMM R3 peptide (300 mcg for the first 12 patients and 1000 mcg for patients 13–24) emulsified with the incomplete Freund’s adjuvant (day 3) and GM-CSF (100 mcg, days 1–5) was administrated four times subcutaneously. The primary aim of the study is safety and feasibility of this peptide vaccination, secondary aims the evaluation of a specific T cell immune response to RHAMM/CD168 R3 peptide and the assessment of the influence of the R3 peptide vaccination on the remission status. Since January 2005, 14 patients have been enrolled in the study. The first ten patients (2 AML, 4 MDS, 4 MM) have completed the course of four vaccinations and have been completely evaluated. Therapy related adverse events observed under R3-peptide vaccination were erythema and induration of the skin at the site of injection (CTC I°). In 5/10 patients, we detected in the peripheral blood a significant increase of specific CD8+ T cells recognizing the R3 peptide in ELISPOT analysis and seven-color flow cytometry including tetramer staining. As expected, after vaccination with the HLA class I peptide R3 no significant increase of IgG titers against the antigen RHAMM could be detected. Clinical responses have been assessed by the examination of peripheral blood and bone-marrow samples before and after vaccination. Patients showed a reduction of the tumor-specific expressed antigen RHAMM/CD168 in real-time RT-PCR analysis after vaccination. 3/6 patients with myeloid disorders (1 AML, 2 MDS/RAEB1) showed a reduction of CD33+ cells in FACS analysis of the bone-marrow after four vaccinations from 10 and 7 % to 1–2 and

The method of gene transfer into progenitor cells is critical as viral vector transduction involves the risk of tumor induction by non-specific genomic integration. Non-viral transfection systems often fail due to low transfection efficiency. However, gene transfer into human CD34+ hematopoietic progenitor (HPC) and mesenchymal stem cells (MSC) is an essential tool for in vitro- and in vivo-applications and therapeutic strategies such as tissue engineering and gene therapy. We recently reported an transient genetic labelling of human CD34+ HPC with deltaLNGFR-plasmid-DNA for in vivo application: Transient transfection was efficient for both, CD34+ HSC (41% ± 2%) and leukemia cell lines (55% ± 4.9%) using the method of nucleofection. Moreover, mature myeloid cells (CD66b+) derived from transfected human CD34+ HPC and leukemia cells maintained deltaLNGFR expression at a high percentage (70% ± 1.6% and 58% ± 2% respectively). In this work, we investigated labelling of CD34+ HPC with mRNA. Human CD34+ HPC and human MSC were transfected with in vitro-transcribed mRNA for deltaLNGFR, a marker gene approved for human in vivo-application, using nucleofection. EGFP was used as a control. 24h after nucleofection, FACS-analysis showed a higher transfection efficiency compared to plasmid transfected CD34+ HPC and MSC: A high transfection frequency was found for mRNA-transfected HPCs using deltaLNGFR (82.4±9.7%) and EGFP (88.7±2.6%). We found also a high transfection rate for MSC using the marker genes deltaLNGFR (92.4±3.6%) and EGFP (83.3±4.1%). Cell viability was not affected by mRNA-transfection. Moreover, differentiation assays of deltaLNGFR-selected MSC after transfection, showed that differentiation of MSC into mesenchymal cells like chondrocytes, adipocytes and osteoblasts was not affected by mRNA nucleofection. Taken together, mRNA based nucleofection is a powerful, highly efficient and non-toxic approach for transient labelling of human progenitor cells or, via transfection of selective proteins, for transient manipulation of stem cell function. It may thus be useful to transiently manipulate stem cell characteristics and combine principles of gene therapy and tissue engineering.

Imatinib mesylate (IM, STI571, Gleevec®) is highly effective in the treatment of patients with chronic myelogenous leukemia (CML). In patients with residual disease or relapse after allogeneic stem cell transplantation (allo-SCT), the optimal strategy is a matter of debate: donor lymphocyte infusions (DLIs) alone, IM alone or a combination of both have been administered to CML patients in this clinical situation. As an impairment of anti-viral CD8+ T lymphocyte function by IM has been described, we questioned whether IM also affects specific anti-leukemic CD8+ T lymphocytes. Moreover, we asked to which extent CD4+CD25hi T regulatory cells might be affected by IM thus changing the balance between cytotoxic and tolerogenic T cells. After mixed lymphocyte peptide culture (MLPC), we assessed CD8+ T cells from healthy donors and patients with CML after allo-SCT by tetramer staining/multi-color flow cytometry and enzyme linked immunosorbent spot (ELISPOT) assays, as well as CD4+CD25hicells after 3 days of culture with anti-CD3 and anti-CD28. The release of interferon gamma and granzyme B by CD8+ T lymphocytes specific for R3 (ILSLELMKL), a T cell epitope peptide derived from the leukemia-associated antigen designated RHAMM/CD168 (receptor for hyaluronic acid mediated motility) was inhibited by IM in a clearly dose-dependent fashion in a range from 1 to 25 μM. These T cells were further characterized as CD8+ HLA-A2/R3_tetramer+ WT1_tetra-CD45RA+CD27-CD28-CCR7- effector T cells with the ability to lyse R3 peptide labeled T2 cells and CD34+ CML progenitor cells. The inhibition of CD8+ T lymphocytes was a function of the time of exposure to IM and reversible after removal of IM from the MLPC. On the other hand, the proliferation and function of CD4+CD25hiFoxP3+GITR+TGFß1+ CD69+CD152+ T regulatory cells were also significantly inhibited by IM in a dose-related fashion. These findings suggest that the clinical impact IM must not necessarily result in a reduced efficacy of the graft-versus-leukemia effect observed after allo-SCT and/or DLIs but might depend rather on the ratio of CD8+ cytotoxic T cells and CD4+CD25hi T regulatory cells.

Objective: Replication-dependent telomere shortening can result in cellular senescence or genetic instability. Telomere length both reflects and limits the replicative potential of normal somatic cells. Shortened telomeres have been linked to disease stage, degree of cytopenia as well as to response to treatment in patients with bone marrow failure syndromes. Paroxysmal nocturnal haemoglobinuria (PNH) is caused by a somatic mutation in the X-linked PIG-A gene resulting in a deficiency of GPI-linked proteins on the cell surface. Pancytopenia in PNH is thought to result from an auto-immune mediated depletion of the GPI+ stem cell compartment. In the current study, we aimed to develop a methodology that allows the selective analysis of telomere length in granulocytes from patients with PNH dependent on GPI expression. The aim was to find out whether replicative stress posed on the residual GPI− HSC is reflected in shortened telomere length compared to their GPI+ counterparts. Methods: The telomere length of GPI+ and GPI− granulocytes of 12 patients with PNH and 22 healthy individuals was analysed. For this purpose, we developed Proearolysine Multi-color flow FISH which is based on the crosslinking of a fluorescence-labeled non-toxic derivative of the bacterial toxine Aerolysine (that selectively binds to the GPI anchor of cells) in combination with fluorescence in situ hybridization and flow cytometry. Results: We found significantly (p Conclusion: Autoimmune-mediated damage to the GPI+ HSC compartment leads to compensatory hyperproliferation of predominantly residual GPI− HSC. In line with this hypothesis, coexisting GPI-negative HSC clones showed even more accelerated telomere shortening as compared to their GPI+ counterparts. Potentially, replicative exhaustion of individual HSC clones could contribute to disease progression in PNH. Whether acquired genetic instability due to progressive telomere shortening also accounts for an increased incidence of secondary clonal disorders will need to be evaluated in future prospective studies.

The objective of this study was to define the effects of osteoarthritic (OA) milieu on good manufactured practice‐adipose‐derived mesenchymal stromal cells (GMP‐ASC) that are commonly utilized in cell therapies. Two different OA milieu: OA synovial fluid (SF) and OA‐conditioned medium (CM) from synoviocytes were used to treat GMP‐ASC both in normoxia or hypoxia. GMP‐ASC were tested for cell migration, proliferation, cytokine receptors expression (CXCR1, CXCR2, CXCR3, CXCR4, CXCR7, CCR1, CCR2, CCR3, CCR5, IL6R), and cytokines (CXCL8/IL8, CXCL10/IP10, CXCL12/SDF‐1, CCL2/MCP1, CCL3/MIP1α, CCL4/MIP1β, CCL5/RANTES, IL6) release. Healthy SF was used as controls. We demonstrated that GMP‐ASC show an increase in proliferation, migration, and modulation of CXCR1, CXCR3, CCR1, and CCR5 receptors in hypoxic condition. Moreover, GMP‐ASC migration increased 15‐fold when treated either with OA‐SF or OA‐CM compared with healthy SF both in normoxia and hypoxia. GMP‐ASC treated in both OA milieu showed an increase in CXCR3, CCR3, and IL6R and a decrease in CCR1 and CCR2 receptors. In OA‐SF, we detected higher amount of CXCL10/IP10 than in OA‐CM, while CCL2/MCP1 and CCL4/MIP1β were higher in OA‐CM compared with OA‐SF. CXCL10/IP10 was the only chemokine of the OA milieu, which was down‐modulated after treatment with GMP‐ASC. In conclusion, we demonstrated specific effects of OA milieu on both GMP‐ASC proliferation, migration, and cytokine receptor expression that were strictly dependent on the inflammatory and hypoxic environment. The use of characterized OA milieu is crucial to define the therapeutic effect of GMP‐ASC and indicates that CXCL10/IP10–CXCR3 axis is partially involved in the GMP‐ASC effect on synovial macrophages. © 2019 The Authors. Journal of Orthopaedic Research® published by Wiley Periodicals, Inc. on behalf of Orthopaedic Research Society. J Orthop Res 38:336‐347, 2020, The objective of this study was to define in vitro the effects of osteoarthritic (OA) milieu and hypoxia on good manufactured practice‐adipose‐derived mesenchymal stromal cells (GMP‐ASC) that are commonly utilized in cell therapies. Hypoxia increased GMP‐ASC proliferation. OA milieu‐treated GMP‐ASC showed an increase in cellular migration, as well as in CXCR3, CCR3, and IL6R and a decrease in CCR1 and CCR2 receptors in hypoxia. CXCL10/IP10 was the only chemokine of the OA milieu down‐modulated after treatment with GMP‐ASC.