Microbial ligand-independent regulation of lymphopoiesis by NOD1.

Aberrant differentiation of progenitor cells in the hematopoietic system is known to severely impact host immune responsiveness. Here we demonstrate that NOD1, a cytosolic innate sensor of bacterial peptidoglycan, also functions in murine hematopoietic cells as a major regulator of both the generation and differentiation of lymphoid progenitors as well as peripheral T lymphocyte homeostasis. We further show that NOD1 mediates these functions by facilitating STAT5 signaling downstream of hematopoietic cytokines. In steady-state, loss of NOD1 resulted in a modest but significant decrease in numbers of mature T, B and natural killer cells. During systemic protozoan infection this defect was markedly enhanced, leading to host mortality. Lack of functional NOD1 also impaired T cell-dependent anti-tumor immunity while preventing colitis. These findings reveal that, in addition to its classical role as a bacterial ligand receptor, NOD1 plays an important function in regulating adaptive immunity through interaction with a major host cytokine signaling pathway.

Glycolytic metabolism of pathogenic T cells enables early detection of GVHD by 13C-MRI.

Graft-versus-host disease (GVHD) is a prominent barrier to allogeneic hematopoietic stem cell transplantation (AHSCT). Definitive diagnosis of GVHD is invasive, and biopsies of involved tissues pose a high risk of bleeding and infection. T cells are central to GVHD pathogenesis, and our previous studies in a chronic GVHD mouse model showed that alloreactive CD4+ T cells traffic to the target organs ahead of overt symptoms. Because increased glycolysis is an early feature of T-cell activation, we hypothesized that in vivo metabolic imaging of glycolysis would allow noninvasive detection of liver GVHD as activated CD4+ T cells traffic into the organ. Indeed, hyperpolarized 13C-pyruvate magnetic resonance imaging detected high rates of conversion of pyruvate to lactate in the liver ahead of animals becoming symptomatic, but not during subsequent overt chronic GVHD. Concomitantly, CD4+ T effector memory cells, the predominant pathogenic CD4+ T-cell subset, were confirmed to be highly glycolytic by transcriptomic, protein, metabolite, and ex vivo metabolic activity analyses. Preliminary data from single-cell sequencing of circulating T cells in patients undergoing AHSCT also suggested that increased glycolysis may be a feature of incipient acute GVHD. Metabolic imaging is being increasingly used in the clinic and may be useful in the post-AHSCT setting for noninvasive early detection of GVHD.

Signaling by intrathymic cytokines, not T cell antigen receptors, specifies CD8 lineage choice and promotes the differentiation of cytotoxic-lineage T cells.

Immature CD4(+)CD8(+) (double-positive (DP)) thymocytes are signaled via T cell antigen receptors (TCRs) to undergo positive selection and become responsive to intrathymic cytokines such as interleukin 7 (IL-7). We report here that cytokine signaling is required for positively selected thymocytes to express the transcription factor Runx3, specify CD8 lineage choice and differentiate into cytotoxic-lineage T cells. In DP thymocytes genetically engineered to be cytokine responsive, IL-7 signaling induced TCR-unsignaled DP thymocytes to express Runx3 and to differentiate into mature CD8(+) T cells, completely circumventing positive selection. We conclude that TCR-mediated positive selection converts DP cells into cytokine-responsive thymocytes, but it is subsequent signaling by intrathymic cytokines that specifies CD8 lineage choice and promotes differentiation into cytotoxic-lineage T cells.

Long-term follow-up after lymphodepleting autologous haematopoietic cell transplantation for treatment-resistant systemic lupus erythematosus.

OBJECTIVE: Autologous haematopoietic cell transplantation (AHSCT) improves immunologic dysfunction in patients with SLE. However, the curative potential of this therapy remains uncertain. This study reports outcomes in SLE patients receiving a lymphodepleting, reduced intensity regimen for AHSCT in SLE. METHODS: Eight patients with SLE refractory to treatment, including i.v. cyclophosphamide (CYC), were enrolled. Five had LN and three CNS involvement as primary indications for transplant. Haematopoietic cell mobilization with CYC, G-CSF and rituximab was followed by collection of CD34+ positively selected cells. The conditioning regimen consisted of concurrent administration of CYC, fludarabine and rituximab. All immunosuppressive medications were discontinued at the start of mobilization and CS were rapidly tapered after the transplant. RESULTS: Five of eight patients achieved a complete response, including a decline in the SLEDAI to zero, which was sustained in four patients for a median of 165 months (range 138-191). One patient achieved a partial response, which was followed by relapse at month 18. Two patients with nephritis and underlying comorbidities in most organs had early deaths from infection and multiorgan failure. AHSCT resulted in profound lymphodepletion, followed by expansion of Treg cells and repopulation of naive T and B cells. Patients with a complete response showed a sustained suppression of the SLE-associated IFN-induced gene signature, marked depletion of memory and plasmablast B cells and resultant sustained elimination of anti-dsDNA antibody. CONCLUSION: Durable clinical and serologic remissions with suppression in the IFN gene signature can be achieved in refractory SLE following lymphodepleting AHSCT. TRIAL REGISTRATION: ClinicalTrials.gov, https://clinicaltrials.gov, NCT00076752.

The Abundance and Availability of Cytokine Receptor IL-2Rß (CD122) Constrain the Lymphopenia-Induced Homeostatic Proliferation of Naive CD4 T Cells.

Lymphopenia-induced homeostatic proliferation (LIP) is a critical mechanism for restoring T cell immunity upon lymphodepleting insults or infections. LIP is primarily driven by homeostatic cytokines, such as IL-7 and IL-15, but not all T cells respond with the same efficiency to homeostatic proliferative cues. Although CD8 T cells vigorously proliferate under lymphopenic conditions, naive CD4 T cells are substantially impaired in their response to homeostatic cytokines, and they fail to fully expand. In this study, we show that the availability of IL-2Rß (CD122), which is a receptor subunit shared by IL-2 and IL-15, affects both the cytokine responsiveness and the LIP of naive CD4 T cells in the mouse. The enumeration of surface IL-2Rß molecules on murine naive CD4 and naive CD8 T cells revealed a 5-fold difference in IL-2Rß abundance. Notably, it was the limited availability of IL-2Rß that impaired CD4 T cell responsiveness to IL-15 and suppressed their LIP. As such, forced IL-2Rß expression on CD4 T cells by transgenesis bestowed IL-15 responsiveness onto naive CD4 T cells, which thus acquired the ability to undergo robust LIP. Collectively, these results identify IL-2Rß availability as a new regulatory mechanism to control cytokine responsiveness and the homeostatic proliferation of murine CD4 T cells.

Prospective Study of a Novel, Radiation-Free, Reduced-Intensity Bone Marrow Transplantation Platform for Primary Immunodeficiency Diseases.

Allogeneic blood or marrow transplantation (BMT) is a potentially curative therapy for patients with primary immunodeficiency (PID). Safe and effective reduced-intensity conditioning (RIC) approaches that are associated with low toxicity, use alternative donors, and afford good immune reconstitution are needed to advance the field. Twenty PID patients, ranging in age from 4 to 58 years, were treated on a prospective clinical trial of a novel, radiation-free and serotherapy-free RIC, T-cell-replete BMT approach using pentostatin, low-dose cyclophosphamide, and busulfan for conditioning with post-transplantation cyclophosphamide-based graft-versus-host-disease (GVHD) prophylaxis. This was a high-risk cohort with a median hematopoietic cell transplantation comorbidity index of 3. With median follow-up of survivors of 1.9 years, 1-year overall survival was 90% and grade III to IV acute GVHD-free, graft-failure-free survival was 80% at day +180. Graft failure incidence was 10%. Split chimerism was frequently observed at early post-BMT timepoints, with a lower percentage of donor T cells, which gradually increased by day +60. The cumulative incidences of grade II to IV and grade III to IV acute GVHD (aGVHD) were 15% and 5%, respectively. All aGVHD was steroid responsive. No patients developed chronic GVHD. Few significant organ toxicities were observed. Evidence of phenotype reversal was observed for all engrafted patients, even those with significantly mixed chimerism (n = 2) or with unknown underlying genetic defect (n = 3). All 6 patients with pre-BMT malignancies or lymphoproliferative disorders remain in remission. Most patients have discontinued immunoglobulin replacement. All survivors are off immunosuppression for GVHD prophylaxis or treatment. This novel RIC BMT approach for patients with PID has yielded promising results, even for high-risk patients.

Cytomegalovirus Infection Incidence and Risk Factors Across Diverse Hematopoietic Cell Transplantation Platforms Using a Standardized Monitoring and Treatment Approach: A Comprehensive Evaluation from a Single Institution.

Human cytomegalovirus (CMV) infection and disease remains a significant cause of morbidity and mortality for hematopoietic cell transplantation (HCT) recipients. Disruption of or weak reconstitution of virus-specific cellular immune function, such as with certain HCT approaches, poses significant risk for CMV-related complications. The incidence of and risk factors for CMV infection and the nature of CMV disease were evaluated retrospectively among 356 consecutive HCT recipients transplanted at the National Institutes of Health using all graft sources, including bone marrow, peripheral blood stem cell (PBSC), and umbilical cord blood (UCB), and a range of in vivo and ex vivo approaches for graft-versus-host disease (GVHD) prophylaxis. The cumulative incidence of CMV infection was higher for CMV-seropositive recipients at 33%, regardless of donor CMV serostatus. Patients transplanted with CMV-seropositive donors had a significantly shorter duration of antiviral therapy. Among graft sources UCB was associated with the highest cumulative incidence of CMV infection at 65% and significantly longer treatment duration at a median of 36days, whereas PBSC HCT was associated with the lowest incidence at 26% and the shortest CMV treatment duration at a median of 21days. There were significant differences in the cumulative incidence of CMV infection by T cell manipulation strategy when systemic steroids were included as a risk-modifying event. Over one-third of CMV infections occurred in the setting of systemic steroid administration. CMV disease occurred in 5% of HCT recipients, with 70% of cases in the setting of treatment for GVHD. Although factors related to serostatus, graft source, and GVHD prophylaxis were associated with varied CMV infection incidence, unplanned post-HCT corticosteroid therapy contributed greatly to the incidence of both CMV infection and disease across HCT approaches, highlighting this post-HCT intervention as a key time to potentially tailor the approach to monitoring, preemptive therapy, and even prophylaxis.

T cells expressing an anti-B-cell maturation antigen chimeric antigen receptor cause remissions of multiple myeloma.

Therapies with novel mechanisms of action are needed for multiple myeloma (MM). B-cell maturation antigen (BCMA) is expressed in most cases of MM. We conducted the first-in-humans clinical trial of chimeric antigen receptor (CAR) T cells targeting BCMA. T cells expressing the CAR used in this work (CAR-BCMA) specifically recognized BCMA-expressing cells. Twelve patients received CAR-BCMA T cells in this dose-escalation trial. Among the 6 patients treated on the lowest 2 dose levels, limited antimyeloma activity and mild toxicity occurred. On the third dose level, 1 patient obtained a very good partial remission. Two patients were treated on the fourth dose level of 9 × 10(6) CAR(+) T cells/kg body weight. Before treatment, the first patient on the fourth dose level had chemotherapy-resistant MM, making up 90% of bone marrow cells. After treatment, bone marrow plasma cells became undetectable by flow cytometry, and the patient's MM entered a stringent complete remission that lasted for 17 weeks before relapse. The second patient on the fourth dose level had chemotherapy-resistant MM making up 80% of bone marrow cells before treatment. Twenty-eight weeks after this patient received CAR-BCMA T cells, bone marrow plasma cells were undetectable by flow cytometry, and the serum monoclonal protein had decreased by >95%. This patient is in an ongoing very good partial remission. Both patients treated on the fourth dose level had toxicity consistent with cytokine-release syndrome including fever, hypotension, and dyspnea. Both patients had prolonged cytopenias. Our findings demonstrate antimyeloma activity of CAR-BCMA T cells. This trial was registered to www.clinicaltrials.gov as #NCT02215967.

Generation of clinical-grade CD19-specific CAR-modified CD8+ memory stem cells for the treatment of human B-cell malignancies.

Long-lived, self-renewing, multipotent T memory stem cells (TSCM) can trigger profound and sustained tumor regression but their rareness poses a major hurdle to their clinical application. Presently, clinically compliant procedures to generate relevant numbers of this T-cell population are undefined. Here, we provide a strategy for deriving large numbers of clinical-grade tumor-redirected TSCM starting from naive precursors. CD8(+)CD62L(+)CD45RA(+) naive T cells enriched by streptamer-based serial-positive selection were activated by CD3/CD28 engagement in the presence of interleukin-7 (IL-7), IL-21, and the glycogen synthase-3ß inhibitor TWS119, and genetically engineered to express a CD19-specific chimeric antigen receptor (CD19-CAR). These conditions enabled the generation of CD19-CAR-modified CD8(+) TSCM that were phenotypically, functionally, and transcriptomically equivalent to their naturally occurring counterpart. Compared with CD8(+) T cells generated with clinical protocols currently under investigation, CD19-CAR-modified CD8(+) TSCM exhibited enhanced metabolic fitness and mediated robust, long-lasting antitumor responses against systemic acute lymphoblastic leukemia xenografts. This clinical-grade platform provides the basis for a phase 1 trial evaluating the activity of CD19-CAR-modified CD8(+) TSCM in patients with B-cell malignancies refractory to prior allogeneic hematopoietic stem cell transplantation.

Upregulation of IFN-Inducible and Damage-Response Pathways in Chronic Graft-versus-Host Disease.

Although chronic graft-versus-host disease (CGVHD) is the primary nonrelapse complication of allogeneic transplantation, understanding of its pathogenesis is limited. To identify the main operant pathways across the spectrum of CGVHD, we analyzed gene expression in circulating monocytes, chosen as in situ systemic reporter cells. Microarrays identified two interrelated pathways: 1) IFN-inducible genes, and 2) innate receptors for cellular damage. Corroborating these with multiplex RNA quantitation, we found that multiple IFN-inducible genes (affecting lymphocyte trafficking, differentiation, and Ag presentation) were concurrently upregulated in CGVHD monocytes compared with normal subjects and non-CGVHD control patients. IFN-inducible chemokines were elevated in both lichenoid and sclerotic CGHVD plasma and were linked to CXCR3+ lymphocyte trafficking. Furthermore, the levels of the IFN-inducible genes CXCL10 and TNFSF13B (BAFF) were correlated at both the gene and the plasma levels, implicating IFN induction as a factor in elevated BAFF levels in CGVHD. In the second pathway, damage-/pathogen-associated molecular pattern receptor genes capable of inducing type I IFN were upregulated. Type I IFN-inducible MxA was expressed in proportion to CGVHD activity in skin, mucosa, and glands, and expression of TLR7 and DDX58 receptor genes correlated with upregulation of type I IFN-inducible genes in monocytes. Finally, in serial analyses after transplant, IFN-inducible and damage-response genes were upregulated in monocytes at CGVHD onset and declined upon therapy and resolution in both lichenoid and sclerotic CGVHD patients. This interlocking analysis of IFN-inducible genes, plasma analytes, and tissue immunohistochemistry strongly supports a unifying hypothesis of induction of IFN by innate response to cellular damage as a mechanism for initiation and persistence of CGVHD.

Predictors for Permanent Discontinuation of Systemic Immunosuppression in Severely Affected Chronic Graft-Versus-Host Disease Patients.

Predicting the duration of systemic therapy in patients with chronic graft-versus-host disease (cGVHD) is of critical clinical importance when counseling patients and for treatment planning. cGVHD characteristics associated with this outcome have not been studied in severely affected patients. The National Institutes of Health (NIH) cGVHD scoring provides a standardized set of organ severity measures that could represent clinically useful and reproducible predictive characteristics. We analyzed 227 previously treated patients most with moderate (n = 54) or severe (n = 170) cGVHD defined by NIH criteria who were prospectively enrolled in a natural history protocol (NCT00092235). Patients received a median of 4 prior systemic therapy regimens and were seen at the NIH for a single time-point visit and were then monitored for survival and ability to discontinue cGVHD systemic therapy. With a median follow-up of 71.1 months, the cumulative incidence of systemic therapy discontinuation was 9.5% (95% confidence interval, 6.0% to 13.9%) at 2 years and 27.7% (95% confidence interval, 20.9% to 34.8%) by 5 years after the initial visit. Factors associated with a higher incidence of immunosuppression discontinuation included lower NIH global severity (P = .019) and lung (P = .030) scores and less extensive deep sclerosis (<37% body surface area, P = .024). Lower patient- and clinician-reported 0 to 10 severity NIH scores and noncyclosporine prophylaxis regimens were also associated with higher incidence of immunosuppression discontinuation (P <.05). In conclusion, we found low success rates for immune suppression discontinuation in previously treated patients who were severely affected with cGVHD. NIH scoring and clinical measures provide new standardized disease-specific tools to predict discontinuation of systemic therapy.

Allogeneic Hematopoietic Cell Transplantation for Aggressive NK Cell Leukemia. A Center for International Blood and Marrow Transplant Research Analysis.

Aggressive NK cell leukemia (ANKL) is an exceedingly rare form of leukemia and carries a poor prognosis, with a median survival of only 2 months. Using the Center for International Blood and Marrow Transplant Research database, we evaluated outcomes of allogeneic hematopoietic cell transplantation (alloHCT) in patients with ANKL. Twenty-one patients with a centrally confirmed diagnosis of ANKL were included. Median patient age was 42 years and 15 patients (71%) were Caucasian. Fourteen patients (67%) were in complete remission (CR) at the time of alloHCT, and 5 patients had active disease. Median follow-up of survivors was 25 months (range, 12 to 116). The 2-year estimates of nonrelapse mortality, relapse/progression, progression-free (PFS), and overall survival (OS) were 21%, 59%, 20%, and 24%, respectively. The 2-year PFS of patients in CR at the time of alloHCT was significantly better than that of patients with active disease at transplantation (30% versus 0%; P = .001). The 2-year OS in similar order was 38% versus 0% (P < .001). In conclusion, this registry analysis that included majority non-Asian patient population shows that alloHCT can provide durable disease control in a subset of ANKL patients. Achieving CR before transplantation appears to be a prerequisite for successful transplantation outcomes.

Distinct IL-7 signaling in recent thymic emigrants versus mature naïve T cells controls T-cell homeostasis.

IL-7 is essential for T-cell survival but its availability is limited in vivo. Consequently, all peripheral T cells, including recent thymic emigrants (RTEs) are constantly competing for IL-7 to survive. RTEs are required to replenish TCR diversity and rejuvenate the peripheral T-cell pool. However, it remains unknown how RTEs successfully compete with resident mature T cells for IL-7. Moreover, RTEs express low levels of IL-7 receptors, presumably rendering them even less competitive. Here, we show that, surprisingly, RTEs are more responsive to IL-7 than mature naïve T cells as demonstrated by markedly increased STAT5 phosphorylation upon IL-7 stimulation. Nonetheless, adoptive transfer of RTE cells into lymphopenic host mice resulted in slower IL-7-induced homeostatic proliferation and diminished expansion compared to naïve donor T cells. Mechanistically, we found that IL-7 signaling in RTEs preferentially upregulated expression of Bcl-2, which is anti-apoptotic but also anti-proliferative. In contrast, naïve T cells showed diminished Bcl-2 induction but greater proliferative response to IL-7. Collectively, these data indicate that IL-7 responsiveness in RTE is designed to maximize survival at the expense of reduced proliferation, consistent with RTE serving as a subpopulation of T cells rich in diversity but not in frequency.

Serial changes in lymphocyte subsets in patients with newly diagnosed high grade astrocytomas treated with standard radiation and temozolomide.

The immune system plays a significant role in cancer prevention and outcome. In high grade astrocytomas (HGA), severe lymphopenia is associated with shortened survival due to tumor progression. This study was performed to quantify serial changes in lymphocyte subsets in HGA following standard radiation (RT) and temozolomide (TMZ). Adults (KPS >60, HIV negative) with newly diagnosed HGA scheduled to receive concurrent RT and TMZ and adjuvant TMZ were eligible. Blood was collected before beginning concurrent RT/TMZ and at weeks 6, 10, 18, and 26, and 3 months after completing adjuvant TMZ. Lymphocyte subsets were analyzed by flow cytometry. Twenty patients (70% glioblastoma, median age 53, 50% male, 80% Caucasian) who enrolled from January 2014 to August 2014 were followed until April 2016. Baseline dexamethasone dose was 0.5 mg/day and 15% had absolute lymphocyte counts (ALC) <1000 cells/mm3 before starting RT/TMZ. However, 75% developed lymphopenia with ALC <1000 cells/mm3 after completion of RT/TMZ. NK cells, B cells and all T lymphocytes subsets dropped significantly after concurrent RT/TMZ and remained depressed for the 48 weeks of observation. The CD4+/CD8+ ratio was not affected significantly during follow-up. Severe lymphopenia involving all subsets occurred early in treatment and remained present for nearly 1 year. To our knowledge, this is the first report of serial trends in lymphocyte subsets following standard RT and TMZ for HGA.

Characterization and Risk Factor Analysis of Osteoporosis in a Large Cohort of Patients with Chronic Graft-versus-Host Disease.

The National Institutes of Health Chronic Graft-versus-Host Disease (cGVHD) Consensus Project Ancillary and Supportive Care Guidelines recommend annual assessment of bone mineral density (BMD) to monitor bone health. The study of osteoporosis in patients with cGVHD has been limited to small numbers of patients, and the guidelines are based on experience with other chronic diseases and expert opinion. We hypothesized that the prevalence of osteoporosis is high in a cohort of 258 patients with moderate to severe cGVHD because of prolonged exposure to risk factors for osteoporosis after allogeneic hematopoietic stem cell transplantation. We defined osteoporosis using BMD criteria (T-score ≤-2.5) at 3 anatomic sites-the femoral neck (FN), lumbar spine (LS), and total hip (TH)-and characterized risk factors through univariate and multivariate analyses. We found that low body weight (FN, P < .0001; LS, P = .0002; TH, P < .0001), malnutrition (FN, P = .0002; LS, P = .03; TH, P = .0076), higher platelet count (FN, P = .0065; TH, P = .0025), higher average National Institutes of Health organ score (FN, P = .038), higher prednisone dose (LS, P = .032), lower complement component 3 (LS, P = .0073), and physical inactivity (FN, P = .01) were associated with osteoporosis in at least 1 site. T-scores were significantly lower in the FN compared with the LS or TH (P < .0001 for both). The prevalence of osteoporosis and osteopenia was high (17% and 60%, respectively), supporting current recommendations for frequent monitoring of BMD. The association of higher platelet count in patients with cGVHD and osteoporosis has not been reported previously and represents a new area of interest in the study of osteoporosis after allogeneic hematopoietic stem cell transplantation.

Accumulation of 4-1BBL+ B cells in the elderly induces the generation of granzyme-B+ CD8+ T cells with potential antitumor activity.

Although the accumulation of highly-differentiated and granzyme B (GrB)-expressing CD8(+)CD28(-) T cells has been associated with aging, the mechanism for their enrichment and contribution to immune function remains poorly understood. Here we report a novel B-cell subset expressing 4-1BBL, which increases with age in humans, rhesus macaques, and mice, and with immune reconstitution after chemotherapy and autologous progenitor cell transplantation. These cells (termed 4BL cells) induce GrB(+)CD8(+) T cells by presenting endogenous antigens and using the 4-1BBL/4-1BB axis. We found that the 4BL cells increase antitumor responses in old mice, which may explain in part the paradox of retarded tumor growth in the elderly. 4BL cell accumulation and its capacity to evoke the generation of GrB(+)CD8(+) T cells can be eliminated by inducing reconstitution of B cells in old mice, suggesting that the age-associated skewed cellular immune responses are reversible. We propose that 4BL cells and the 4-1BBL signaling pathway are useful targets for improved effectiveness of natural antitumor defenses and therapeutic immune manipulations in the elderly.

Bone marrow-derived mesenchymal stromal cells harness purinergenic signaling to tolerize human Th1 cells in vivo.

The use of bone marrow-derived mesenchymal stromal cells (BMSC) in the treatment of alloimmune and autoimmune conditions has generated much interest, yet an understanding of the therapeutic mechanism remains elusive. We therefore explored immune modulation by a clinical-grade BMSC product in a model of human-into-mouse xenogeneic graft-versus-host disease (x-GVHD) mediated by human CD4(+) Th1 cells. BMSC reversed established, lethal x-GVHD through marked inhibition of Th1 cell effector function. Gene marking studies indicated BMSC engraftment was limited to the lung; furthermore, there was no increase in regulatory T cells, thereby suggesting a paracrine mechanism of BMSC action. BMSC recipients had increased serum CD73 expressing exosomes that promoted adenosine accumulation ex vivo. Importantly, immune modulation mediated by BMSC was fully abrogated by pharmacologic therapy with an adenosine A2A receptor antagonist. To investigate the potential clinical relevance of these mechanistic findings, patient serum samples collected pre- and post-BMSC treatment were studied for exosome content: CD73 expressing exosomes promoting adenosine accumulation were detected in post-BMSC samples. In conclusion, BMSC effectively modulate experimental GVHD through a paracrine mechanism that promotes adenosine-based immune suppression.

Thymic medullary epithelium and thymocyte self-tolerance require cooperation between CD28-CD80/86 and CD40-CD40L costimulatory pathways.

A critical process during thymic development of the T cell repertoire is the induction of self-tolerance. Tolerance in developing T cells is highly dependent on medullary thymic epithelial cells (mTEC), and mTEC development in turn requires signals from mature single-positive thymocytes, a bidirectional relationship termed thymus crosstalk. We show that CD28-CD80/86 and CD40-CD40L costimulatory interactions, which mediate negative selection and self-tolerance, upregulate expression of LTα, LTß, and receptor activator for NF-κB in the thymus and are necessary for medullary development. Combined absence of CD28-CD80/86 and CD40-CD40L results in profound deficiency in mTEC development comparable to that observed in the absence of single-positive thymocytes. This requirement for costimulatory signaling is maintained even in a TCR transgenic model of high-affinity TCR-ligand interactions. CD4 thymocytes maturing in the altered thymic epithelial environment of CD40/CD80/86 knockout mice are highly autoreactive in vitro and are lethal in congenic adoptive transfer in vivo, demonstrating a critical role for these costimulatory pathways in self-tolerance as well as thymic epithelial development. These findings demonstrate that cooperativity between CD28-CD80/86 and CD40-CD40L pathways is required for normal medullary epithelium and for maintenance of self-tolerance in thymocyte development.

Phase 2 clinical trial of rapamycin-resistant donor CD4+ Th2/Th1 (T-Rapa) cells after low-intensity allogeneic hematopoietic cell transplantation.

In experimental models, ex vivo induced T-cell rapamycin resistance occurred independent of T helper 1 (Th1)/T helper 2 (Th2) differentiation and yielded allogeneic CD4(+) T cells of increased in vivo efficacy that facilitated engraftment and permitted graft-versus-tumor effects while minimizing graft-versus-host disease (GVHD). To translate these findings, we performed a phase 2 multicenter clinical trial of rapamycin-resistant donor CD4(+) Th2/Th1 (T-Rapa) cells after allogeneic-matched sibling donor hematopoietic cell transplantation (HCT) for therapy of refractory hematologic malignancy. T-Rapa cell products, which expressed a balanced Th2/Th1 phenotype, were administered as a preemptive donor lymphocyte infusion at day 14 post-HCT. After T-Rapa cell infusion, mixed donor/host chimerism rapidly converted, and there was preferential immune reconstitution with donor CD4(+) Th2 and Th1 cells relative to regulatory T cells and CD8(+) T cells. The cumulative incidence probability of acute GVHD was 20% and 40% at days 100 and 180 post-HCT, respectively. There was no transplant-related mortality. Eighteen of 40 patients (45%) remain in sustained complete remission (range of follow-up: 42-84 months). These results demonstrate the safety of this low-intensity transplant approach and the feasibility of subsequent randomized studies to compare T-Rapa cell-based therapy with standard transplantation regimens.

Donor-derived CD19-targeted T cells cause regression of malignancy persisting after allogeneic hematopoietic stem cell transplantation.

New treatments are needed for B-cell malignancies persisting after allogeneic hematopoietic stem cell transplantation (alloHSCT). We conducted a clinical trial of allogeneic T cells genetically modified to express a chimeric antigen receptor (CAR) targeting the B-cell antigen CD19. T cells for genetic modification were obtained from each patient's alloHSCT donor. All patients had malignancy that persisted after alloHSCT and standard donor lymphocyte infusions (DLIs). Patients did not receive chemotherapy prior to the CAR T-cell infusions and were not lymphocyte depleted at the time of the infusions. The 10 treated patients received a single infusion of allogeneic anti-CD19-CAR T cells. Three patients had regressions of their malignancies. One patient with chronic lymphocytic leukemia (CLL) obtained an ongoing complete remission after treatment with allogeneic anti-CD19-CAR T cells, another CLL patient had tumor lysis syndrome as his leukemia dramatically regressed, and a patient with mantle cell lymphoma obtained an ongoing partial remission. None of the 10 patients developed graft-versus-host disease (GVHD). Toxicities included transient hypotension and fever. We detected cells containing the anti-CD19-CAR gene in the blood of 8 of 10 patients. These results show for the first time that donor-derived allogeneic anti-CD19-CAR T cells can cause regression of B-cell malignancies resistant to standard DLIs without causing GVHD.