Human Mesenchymal Stem Cell-Educated Macrophages Are a Distinct High IL-6-Producing Subset that Confer Protection in Graft-versus-Host-Disease and Radiation Injury Models.

Mesenchymal stem cells (MSCs) have immunosuppressive and tissue repair properties, but clinical trials using MSCs to prevent or treat graft-versus-host disease (GVHD) have shown mixed results. Macrophages (MØs) are important regulators of immunity and can promote tissue regeneration and remodeling. We have previously shown that MSCs can educate MØs toward a unique anti-inflammatory immunophenotype (MSC-educated MØs [MEMs]); however, their implications for in vivo models of inflammation have not been studied yet. We now show that in comparison with MØs, MEMs have increased expression of the inhibitory molecules PD-L1, PD-L2, in addition to markers of alternatively activated MØs: CD206 and CD163. RNA-Seq analysis of MEMs, as compared with MØs, show a distinct gene expression profile that positively correlates with multiple pathways important in tissue repair. MEMs also show increased expression of IL-6, transforming growth factor-ß, arginase-1, CD73, and decreased expression of IL-12 and tumor necrosis factor-α. We show that IL-6 secretion is controlled in part by the cyclo-oxygenase-2, arginase, and JAK1/STAT1 pathway. When tested in vivo, we show that human MEMs significantly enhance survival from lethal GVHD and improve survival of mice from radiation injury. We show these effects could be mediated in part through suppression of human T cell proliferation and may have attenuated host tissue injury in part by enhancing murine fibroblast proliferation. MEMs are a unique MØ subset with therapeutic potential for the management of GVHD and/or protection from radiation-induced injury.

Collection of hematopoietic CD34 stem cells in rhesus macaques using Spectra Optia.

BACKGROUND: Nonhuman primates, particularly rhesus macaques, are ideal preclinical large animal models to investigate organ tolerance induction protocols using donor hematopoietic stem cells (HSCs) to induce chimerism. Their relatively small size poses some challenges for the safe and effective collection of peripheral blood HSCs through apheresis procedures. We describe our experiences using the Spectra Optia apheresis unit to successfully obtain HSCs from mobilized peripheral blood of rhesus macaques. METHOD: Mobilization of peripheral blood HSCs was induced using granulocyte stimulating factor (G-CSF) and Mozobil. The Spectra Optia unit was used in 18 apheresis procedures in 13 animals (4.9-10 kg). Animal health was carefully monitored during and after the procedure. Changes in peripheral blood cells before, during and after procedure were determined by complete blood count and flow cytometry. RESULTS: The automatic settings of the Spectra Optia unit were applied successfully to the procedures on the rhesus macaque. All animals tolerated the procedure well with no mortality. Mobilization of HSCs were most consistently achieved using 50 µg/kg of G-CSF for 5 days and a single dose of Mozobil on the 5th day, followed by collection of cells 3 h after Mozobil injection. The final apheresis product contained an average of 23 billion total nucleated cells with 47% granulocytes, 3,871 million total CD3 cells and 77 million CD34 cells which resulted in an average of 10 million CD34+ cells/kg of donor weight. CONCLUSION: Apheresis of peripheral blood mobilized HSCs in rhesus macaques using Spectra Optia is a safe and effective procedure.

Fibroblasts and Mesenchymal Stromal/Stem Cells Are Phenotypically Indistinguishable.

BACKGROUND/AIMS: Human mesenchymal stromal/stem cells (MSCs), derived from many different tissues, are characterized by a fibroblast-like morphology, the expression of certain cell surface markers and their ability to differentiate into adipocytes, chondrocytes and osteoblasts. A number of studies have shown that MSCs share many characteristics with fibroblasts; however, there is no well-defined set of phenotypic characteristics that could distinguish between these 2 types of cells. METHODS: We used 4 well-established human fibroblast strains from 3 different tissue sources and several human MSC strains from 2 different tissue sources to compare the phenotypic and immunological characteristics of these cells. RESULTS: Fibroblast strains had a similar morphology to MSCs, expressed the same cell surface markers as MSCs and could also differentiate into adipocytes, chondrocytes and osteoblasts. Also, similar to MSCs, these fibroblasts were capable of suppressing T cell proliferation and modulating the immunophenotype of macrophages. We also show that MSCs deposit extracellular matrices of collagen type I and fibronectin, and express FSP1 in patterns similar to fibroblasts. CONCLUSIONS: Based on currently accepted definitions for cultured human MSCs and fibroblasts, we could not find any immunophenotypic property that could make a characteristic distinction between MSCs and fibroblasts.

A reproducible immunopotency assay to measure mesenchymal stromal cell-mediated T-cell suppression.

BACKGROUND AIMS: The T-cell suppressive property of bone marrow-derived mesenchymal stromal cells (MSCs) has been considered a major mode of action and basis for their utilization in a number of human clinical trials. However, there is no well-established reproducible assay to measure MSC-mediated T-cell suppression. METHODS: At the University of Wisconsin-Madison Production Assistance for Cellular Therapy (PACT) Center, we developed an in vitro quality control T-cell suppression immunopotency assay (IPA) that uses anti-CD3 and anti-CD28 antibodies to stimulate T-cell proliferation. We measured MSC-induced suppression of CD4+ T-cell proliferation at various effector-to-target cell ratios with the use of defined peripheral blood mononuclear cells and in parallel compared with a reference standard MSC product. We calculated an IPA value for suppression of CD4+ T cells for each MSC product. RESULTS: Eleven MSC products generated at three independent PACT centers were evaluated for cell surface phenotypic markers and T-cell suppressive properties. Flow cytometry results demonstrated typical MSC cell surface marker profiles. There was significant variability in the level of suppression of T-cell proliferation, with immunopotency assay values ranging from 27% to 88%. However, MSC suppression did not correlate with human leukocyte antigen-DR expression. CONCLUSIONS: We have developed a reproducible immunopotency assay to measure allogeneic MSC-mediated suppression of CD4+ T cells. Additional studies may be warranted to determine how these in vitro assay results may correlate with other immunomodulatory properties of MSCs, in addition to evaluating the ability of this assay to predict in vivo efficacy.

Efficient manufacturing of therapeutic mesenchymal stromal cells with the use of the Quantum Cell Expansion System.

BACKGROUND: The use of bone marrow-derived mesenchymal stromal cells (MSCs) as a cellular therapy for various diseases, such as graft-versus-host disease, diabetes, ischemic cardiomyopathy and Crohn's disease, has produced promising results in early-phase clinical trials. However, for widespread application and use in later phase studies, manufacture of these cells must be cost-effective, safe and reproducible. Current methods of manufacturing in flasks or cell factories are labor-intensive, involve a large number of open procedures and require prolonged culture times. METHODS: We evaluated the Quantum Cell Expansion System for the expansion of large numbers of MSCs from unprocessed bone marrow in a functionally closed system and compared the results with a flask-based method currently in clinical trials. RESULTS: After only two passages, we were able to expand a mean of 6.6 × 10(8) MSCs from 25 mL of bone marrow reproducibly. The mean expansion time was 21 days, and cells obtained were able to differentiate into all three lineages: chondrocytes, osteoblasts and adipocytes. The Quantum was able to generate the target cell number of 2.0 × 10(8) cells in an average of 9 fewer days and in half the number of passages required during flask-based expansion. We estimated that the Quantum would involve 133 open procedures versus 54,400 in flasks when manufacturing for a clinical trial. Quantum-expanded MSCs infused into an ischemic stroke rat model were therapeutically active. CONCLUSIONS: The Quantum is a novel method of generating high numbers of MSCs in less time and at lower passages when compared with flasks. In the Quantum, the risk of contamination is substantially reduced because of the substantial decrease in open procedures.

Biologic and immunomodulatory properties of mesenchymal stromal cells derived from human pancreatic islets.

BACKGROUND AIMS: Mesenchymal stromal cells (MSC) have now been shown to reside in numerous tissues throughout the body, including the pancreas. Ex vivo culture-expanded MSC derived from many tissues display important interactions with different types of immune cells in vitro and potentially play a significant role in tissue homeostasis in vivo. In this study, we investigated the biologic and immunomodulatory properties of human pancreatic islet-derived MSC. METHODS: We culture-expanded MSC from cadaveric human pancreatic islets and characterized them using flow cytometry, differentiation assays and nuclear magnetic resonance-based metabolomics. We also investigated the immunologic properties of pancreatic islet-derived MSC compared with bone marrow (BM) MSC. RESULTS: Pancreatic islet and BM-derived MSC expressed the same cell-surface markers by flow cytometry, and both could differentiate into bone, fat and cartilage. Metabolomics analysis of MSC from BM and pancreatic islets also showed a similar set of metabolic markers but quantitative polymerase chain reactions showed that pancreatic islet MSC expressed more interleukin(IL)-1b, IL-6, STAT3 and FGF9 compared with BM MSC, and less IL-10. However, similar to BM MSC, pancreatic islet MSC were able to suppress proliferation of allogeneic T lymphocytes stimulated with anti-CD3 and anti-CD28 antibodies. CONCLUSIONS: Our in vitro analysis shows pancreatic islet-derived MSC have phenotypic, biologic and immunomodulatory characteristics similar, but not identical, to BM-derived MSC. We propose that pancreatic islet-derived MSC could potentially play an important role in improving the outcome of pancreatic islet transplantation by promoting engraftment and creating a favorable immune environment for long-term survival of islet allografts.

Cytokine kinetics profiling in pediatric renal transplant recipients.

Pediatric renal transplant recipients experience side effects of immunosuppression. Few immunoassays exist which can assess the adequacy of immunosuppression. We developed a CKT, whereby cytokine levels are measured in a five-day mixed lymphocyte reaction. We describe the in vitro cytokine responses to donor and third-party antigen in a pilot study of nine children after living-donor renal transplantation. The CKT identified five patterns of IFN-gamma secretion relative to donor and third-party alloantigen: no response to alloantigen (n = 2), hypo-response to donor (n = 3), equal response (n = 1), hyper-response to donor (n = 1), and intermediate response (n = 2). IL-2 and IL-13 patterning correlated with IFN-gamma expression. Two of nine subjects had acute rejection, which correlated with intermediate and hyper-responsive profiles. No rejection occurred during immunosuppression or donor-specific hypo-responsiveness. Significant immunosuppression was universal early after transplantation. Two of four children showed strong pretransplant responses to donor, which were regained three months post-transplant, and associated with rejection in one subject. The CKT reflects the level of immunosuppression and may offer a method to assess the adequacy of immunosuppression. A pattern of complete non-responsiveness or hypo-responsiveness correlated with lack of acute rejection. The CKT may prove useful in titrating immunosuppression and in improving live donor selection.

Blockade of BAFF Receptor BR3 on T Cells Enhances Their Activation and Cytotoxicity.

The BAFF receptor BR3 plays key roles in B-cell activation, maturation, and survival whereas the function of BR3 on T lymphocytes is less well characterized. Previous reports have demonstrated that BR3 costimulates human T-cell activation in vitro in the presence of high nonphysiological levels of plate-bound BAFF. Here, relying on the soluble and membrane-bound BAFF expressed by T cells themselves, we investigated the function of BR3 on activated primary CD4 and CD8 T lymphocytes using a BR3-specific neutralization antibody and shRNA gene down-modulation. Interestingly, the anti-BR3 blocking antibody resulted in significant augmentation of CD25 and IFN-γ expression by both subsets, as did shRNA-mediated down-modulation of BR3. In addition, granzyme B expression was substantially elevated in anti-BR3-treated and BR3-silenced T cells. Anti-BR3 blockade increased the expression of CD25 on cytolytic CRTAM T cells. Importantly, anti-BR3 significantly enhanced redirected killing of P-815 cells by both CD4 and CD8 cytotoxic T cells [cytotoxic T lymphocytes (CTLs)]. Furthermore, anti-BR3-augmented CD4 T-cell-mediated killing of class II melanoma cell line A375 and cervical cancer cell line HeLa in vitro, increasing the level of granzyme B activity as measured by PARP-1 cleavage and active caspase 3. Together, our data indicate that BR3 neutralization increases the activation and cytolytic function of CD4 and CD8 cytotoxic T lymphocytes. Our findings provide a novel strategy for ex vivo T-cell activation applicable to T-cell immunotherapy platforms such as TIL or CAR-T cell therapeutics.

Alemtuzumab induction and recurrence of glomerular disease after kidney transplantation.

BACKGROUND: An increase in the incidence of autoimmune diseases has been described in patients receiving alemtuzumab. METHODS: To determine whether induction with alemtuzumab increases recurrence of glomerular disease, we performed a retrospective study in 443 patients with biopsy-proven glomerular diseases undergoing kidney transplantation. Patients receiving alemtuzumab (n=161) were compared with those receiving interleukin (IL)-2-receptor antagonists (n=217) or antithymocyte globulin (n=64). RESULTS: Biopsy-proven glomerular disease recurrence was similar in patients induced with alemtuzumab or IL-2 receptor antagonists. Patients receiving antithymocyte antibody had a lower recurrence rate than patients treated with other induction agents, with borderline significance (hazard ratio [HR] 0.13, 95% confidence interval [95% CI] 0.02-0.98, P=0.047). Patients with systemic lupus treated with alemtuzumab had a similar re-emergence of autoreactive antibodies to patients treated with other agents. Recurrent disease increased the risk of allograft failure (HR 2.36, 95% CI 1.28-4.32, P=0.0056). The development of acute rejection and the use of deceased (vs. living) donor kidneys were also significant factors influencing graft survival. A greater risk of mortality was detected in those patients with recurrent glomerular disease (HR 3.76, 95% CI 1.37-10.35, P=0.01), whereas increased age at transplantation (HR 1.05) and the use of deceased (vs. living) donor kidneys (HR 3.20) also increased mortality. No specific induction agent significantly affected graft loss or mortality when using adjusted or unadjusted hazard ratios. CONCLUSIONS: In this retrospective analysis, induction with alemtuzumab did not increase the rate of re-emergence of autoantibodies or biopsy-proven recurrence of glomerular disease. A slight reduction in the incidence of recurrence was observed in patients treated with thymoglobulin, yet this observation can only be validated in a prospective randomized trial.

T-lymphocyte alloresponses of Campath-1H-treated kidney transplant patients.

BACKGROUND: Kidney transplant patients given Campath-1H (Alemtuzumab) immunodepletion therapy and long-term rapamycin monotherapy have excellent graft survival and function at three years. As an initial step in understanding the characteristics of repopulated T lymphocytes in these patients, we performed several assays to assess alloreactivity. METHODS: We measured T-cell responses using CFSE-labeled recipient lymphocytes in a direct one-way MLR, and also analyzed the kinetics of expression of IFN-gamma. We examined the T-cell responses of Campath-treated transplant patients on monotherapy versus those treated with anti-CD25 (Basiliximab) induction therapy and maintenance immunosuppression consisting of cyclosporine A, mycophenolate mofetil, and steroids. RESULTS: On average, proliferative responses to donor antigen were equal between Campath and control groups. However, the Campath group displayed a greater response to third party compared to donor antigen (CD3 P = 0.04, CD4 P = 0.07, CD8 P < 0.01), whereas the control group did not display a greater response to third party (CD3 P = 0.69, CD4 P = 0.72, CD8 P = 0.60). Interestingly, more Campath patients (4 of 15) than control patients (0 of 8) displayed donor specific unresponsiveness as gauged by IFN-gamma expression and T-cell proliferation (P = 0.15). CONCLUSIONS: These studies suggest that Campath-1H in conjunction with rapamycin monotherapy retains intact immune responses to third party alloantigen, yet may promote hyporesponsiveness to donor antigen.

Autologous Bone Marrow-Derived Mesenchymal Stem Cells Modulate Molecular Markers of Inflammation in Dogs with Cruciate Ligament Rupture.

Mid-substance rupture of the canine cranial cruciate ligament rupture (CR) and associated stifle osteoarthritis (OA) is an important veterinary health problem. CR causes stifle joint instability and contralateral CR often develops. The dog is an important model for human anterior cruciate ligament (ACL) rupture, where rupture of graft repair or the contralateral ACL is also common. This suggests that both genetic and environmental factors may increase ligament rupture risk. We investigated use of bone marrow-derived mesenchymal stem cells (BM-MSCs) to reduce systemic and stifle joint inflammatory responses in dogs with CR. Twelve dogs with unilateral CR and contralateral stable partial CR were enrolled prospectively. BM-MSCs were collected during surgical treatment of the unstable CR stifle and culture-expanded. BM-MSCs were subsequently injected at a dose of 2x106 BM-MSCs/kg intravenously and 5x106 BM-MSCs by intra-articular injection of the partial CR stifle. Blood (entry, 4 and 8 weeks) and stifle synovial fluid (entry and 8 weeks) were obtained after BM-MSC injection. No adverse events after BM-MSC treatment were detected. Circulating CD8+ T lymphocytes were lower after BM-MSC injection. Serum C-reactive protein (CRP) was decreased at 4 weeks and serum CXCL8 was increased at 8 weeks. Synovial CRP in the complete CR stifle was decreased at 8 weeks. Synovial IFNγ was also lower in both stifles after BM-MSC injection. Synovial/serum CRP ratio at diagnosis in the partial CR stifle was significantly correlated with development of a second CR. Systemic and intra-articular injection of autologous BM-MSCs in dogs with partial CR suppresses systemic and stifle joint inflammation, including CRP concentrations. Intra-articular injection of autologous BM-MSCs had profound effects on the correlation and conditional dependencies of cytokines using causal networks. Such treatment effects could ameliorate risk of a second CR by modifying the stifle joint inflammatory response associated with cranial cruciate ligament matrix degeneration or damage.

Correlation between human leukocyte antigen antibody production and serum creatinine in patients receiving sirolimus monotherapy after Campath-1H induction.

BACKGROUND: In this study, we determined whether Campath-1H induction followed by sirolimus monotherapy inhibited alloantibody production in renal transplantation. Second, we evaluated the correlation between human leukocyte antigen (HLA) antibody production and serum creatinine levels. METHODS: Sera were taken 1 to 24 months after transplantation from 24 patients treated with Campath-1H and sirolimus and tested for serum creatinine and HLA-specific antibody by using flow cytometry and enzyme-linked immunosorbent assay. RESULTS: Ten (42%) of the 24 patients treated with Campath-1H and sirolimus produced HLA antibodies. Six of these 10 developed both donor-specific antibodies (DSAs) and non-donor-specific antibodies (NDSAs), whereas only NDSAs were detected in the other four patients. In patients with biopsy-diagnosed humoral rejection (C4d+), serum levels of both DSA and NDSA significantly correlated with patient serum creatinine levels. Rejection treatment successfully reduced both DSAs and NDSAs and reversed humoral rejection. CONCLUSIONS: The numeric relationship between serum creatinine and DSA levels suggests a causal relationship between alloantibody and transplant rejection.

Monotherapy with the novel human anti-CD154 monoclonal antibody ABI793 in rhesus monkey renal transplantation model.

BACKGROUND: This study assesses the safety and efficacy of the novel human anti-human CD154 monoclonal antibody ABI793 in rhesus monkeys. METHODS: Outbred rhesus monkeys were used for renal transplantation from major histocompatibility complex-mismatched donors. Seven recipients were treated with ABI793, and six untreated recipients were used as controls. Graft function was monitored by urine output, serum creatinine, and renal biopsy. Phenotypic analysis of peripheral blood lymphocytes and mixed lymphocyte reaction were performed before transplantation and periodically after transplantation. Anti-donor major histocompatibility complex class I antibody levels were measured at the time of sacrifice. RESULTS: Monkeys in the treated group demonstrated prolonged graft survival compared with controls. One monkey was sacrificed because of a urine leak on postoperative day 13. Three monkeys were sacrificed because of acute rejection (days 44, 149, and 158). Two monkeys were sacrificed because of chronic active rejection (days 154 and 221). One monkey was sacrificed on day 139 without rejection to observe the effects of ABI793 in the absence of rejection. There were no obvious clinical side effects of ABI793, but microscopic thromboembolic changes were observed in two monkeys. Lymphocyte subsets remained unaltered in all monkeys. Mixed lymphocyte reaction showed nonspecific suppression 6 weeks after transplantation. The monkeys with chronic active rejection showed relatively strong alloantibody responses. CONCLUSIONS: ABI793 induces prolonged renal allograft survival in rhesus monkeys. Nevertheless, thromboembolic complications may occur and chronic allograft nephropathy may develop after anti-CD154 treatment is discontinued.

The gene related to anergy in lymphocytes, an E3 ubiquitin ligase, is necessary for anergy induction in CD4 T cells.

Acquisition of the anergy phenotype in T cells is blocked by inhibitors of protein synthesis and calcineurin activity, suggesting that anergic T cells may have a unique genetic program. Retroviral transduction of hemopoietic stem cells from TCR transgenic mice and subsequent reconstitution of syngeneic mice to express the E3 ubiquitin ligase, gene related to anergy in lymphocytes (GRAIL), or an enzymatically inactive form, H2N2 GRAIL, allowed analysis of the role of GRAIL in T cell anergy in vivo. Constitutive expression of GRAIL was sufficient to render naive CD4 T cells anergic, however, when the enzymatically inactive form H2N2 GRAIL was expressed, it functioned as a dominant negative of endogenous GRAIL and blocked the development of anergy. These data provide direct evidence that a biochemical pathway composed of GRAIL and/or GRAIL-interacting proteins is important in the development of the CD4 T cell anergic phenotype in vivo.

GRAIL: an E3 ubiquitin ligase that inhibits cytokine gene transcription is expressed in anergic CD4+ T cells.

T cell anergy may serve to limit autoreactive T cell responses. We examined early changes in gene expression after antigen-TCR signaling in the presence (activation) or absence (anergy) of B7 costimulation. Induced expression of GRAIL (gene related to anergy in lymphocytes) was observed in anergic CD4(+) T cells. GRAIL is a type I transmembrane protein that localizes to the endocytic pathway and bears homology to RING zinc-finger proteins. Ubiquitination studies in vitro support GRAIL function as an E3 ubiquitin ligase. Expression of GRAIL in retrovirally transduced T cell hybridomas dramatically limits activation-induced IL-2 and IL-4 production. Additional studies suggest that GRAIL E3 ubiquitin ligase activity and intact endocytic trafficking are critical for cytokine transcriptional regulation. Expression of GRAIL after an anergizing stimulus may result in ubiquitin-mediated regulation of proteins essential for mitogenic cytokine expression, thus positioning GRAIL as a key player in the induction of the anergic phenotype.

Campath-1H induction plus rapamycin monotherapy for renal transplantation: results of a pilot study.

Campath-1H, an anti-CD52 monoclonal antibody, was used as induction therapy (40 mg i.v. total dose) in 29 primary human renal transplants, and the patients were maintained on rapamycin monotherapy (levels 8-15 ng/mL) post-transplant. Campath-1H profoundly depletes lymphocytes long-term and more transiently depletes B cells and monocytes. All patients are alive and well at 3-29 months of follow up. One graft was lost because of rejection. There have been no systemic infections and no malignancies. Eight of 29 patients have experienced rejection, which was successfully treated in seven of eight patients. Five of these patients had pathological evidence of a humoral component of their rejection. Seven of the 29 patients were converted to standard triple therapy on account of rejection. Rapamycin was generally well tolerated in that there were no significant wound-healing problems; two lymphoceles required surgical drainage; and most patients were treated with a lipid-lowering agent. Flow crossmatch testing post-transplant revealed evidence of alloantibody in two patients tested with previous combined cellular and humoral rejection. Biopsies have shown no chronic allograft nephropathy to date. In view of the relatively high incidence of early humoral rejection, we plan to modify the immunosuppressive regimen in subsequent pilot studies. This clinical trial provides insight into the use of Campath-1H induction in combination with rapamycin maintenance monotherapy.

Essential role of the E3 ubiquitin ligase Cbl-b in T cell anergy induction.

Antigen-specific immunotolerance limits the expansion of self-reactive T cells involved in autoimmune diseases. Here, we show that the E3 ubiquitin ligase Cbl-b is upregulated in T cells after tolerizing signals. Loss of Cbl-b in mice results in impaired induction of T cell tolerance both in vitro and in vivo. Importantly, rechallenge of Cbl-b mutant mice with the tolerizing antigen results in massive lethality. Moreover, ablation of Cbl-b resulted in exacerbated autoimmunity. Mechanistically, loss of Cbl-b rescues reduced calcium mobilization of anergic T cells, which was attributed to Cbl-b-mediated regulation of PLCgamma-1 phosphorylation. Our results show a critical role for Cbl-b in the regulation of peripheral tolerance and anergy of T cells.