Impaired negative regulation of homeostatically proliferating T cells

Phase 2 study of PD-1 blockade following autologous transplantation for patients with AML ineligible for allogeneic transplant

Allogeneic transplant remains the best postremission therapy for patients with nonfavorable risk acute myeloid leukemia (AML). However, some patients are ineligible because of psychosocial barriers, such as lack of appropriate caregiver support. We hypothesized that immune checkpoint inhibition after autologous transplant might represent effective postremission therapy in such patients. We conducted a phase 2 study of autologous transplantation followed by administration of pembrolizumab (8 cycles starting day +1). Twenty patients with nonfavorable AML in complete remission were treated (median age, 64 years; CR1, 80%); 55% were non-White and adverse-risk AML was present in 40%. Treatment was well tolerated, with only 1 nonrelapse death. Immune-related adverse events occurred in 9 patients. After a median follow-up of 80 months, 14 patients remain alive, with 10 patients in continuous remission. The estimated 2-year LFS was 48.4%, which met the primary end point of 2-year LFS >25%; the 2-year overall survival (OS), nonrelapse mortality, and cumulative incidences of relapse were 68%, 5%, and 46%, respectively. In comparison with a propensity score-matched cohort group of patients with AML receiving allogeneic transplant, the 3-year OS was similar (73% vs 76%). Patients in the study had inferior LFS (51% vs 75%) but superior postrelapse survival (45% vs 14%). In conclusion, programmed cell death protein-1 blockade after autologous transplant is a safe and effective alternative postremission strategy in patients with nonfavorable risk AML who are ineligible for allogeneic transplant, a context in which there is significant unmet need. This trial was registered at www.clinicaltrials.gov as #NCT02771197.

Effects of ICOS+ T cell depletion via afucosylated monoclonal antibody MEDI-570 on pregnant cynomolgus monkeys and the developing offspring

MEDI-570 is a fully human afucosylated monoclonal antibody (MAb) against Inducible T-cell costimulator (ICOS), highly expressed on CD4+ T follicular helper (T_FH) cells. Effects of MEDI-570 were evaluated in an enhanced pre-postnatal development toxicity (ePPND) study in cynomolgus monkeys. Administration to pregnant monkeys did not cause any abortifacient effects. Changes in hematology and peripheral blood T lymphocyte subsets in maternal animals and infants and the attenuated infant IgG immune response to keyhole limpet hemocyanin (KLH) were attributed to MEDI-570 pharmacology. Adverse findings included aggressive fibromatosis in one dam and two infant losses in the high dose group with anatomic pathology findings suggestive of atypical lymphoid hyperplasia. The margin of safety relative to the no observed adverse effect level (NOAEL) for the highest planned clinical dose in the Phase 1a study was 7. This study suggests that women of child bearing potential employ effective methods of contraception while being treated with MEDI-570.

Mechanisms of diabetic autoimmunity: I--the inductive interface between islets and the immune system at onset of inflammation

The mechanisms of autoimmune reactivity onset in type 1 diabetes (T1D) remain elusive despite extensive experimentation and discussion. We reconsider several key aspects of the early stages of autoimmunity at four levels: islets, pancreatic lymph nodes, thymic function and peripheral immune homeostasis. Antigen presentation is the islets and has the capacity to provoke immune sensitization, either in the process of physiological neonatal β cell apoptosis or as a consequence of cytolytic activity of self-reactive thymocytes that escaped negative regulation. Diabetogenic effectors are efficiently expanded in both the islets and the lymph nodes under conditions of empty lymphoid niches during a period of time coinciding with a synchronized wave of β cell apoptosis surrounding weaning. A major drive of effector cell activation and expansion is inherent peripheral lymphopenia characteristic of neonates, though it remains unclear when is autoimmunity triggered in subjects displaying hyperglycemia in late adolescence. Our analysis suggests that T1D evolves through coordinated activity of multiple physiological mechanisms of stimulation within specific characteristics of the neonate immune system.

Unique human immune signature of Ebola virus disease in Guinea

Despite the magnitude of the Ebola virus disease (EVD) outbreak in West Africa, there is still a fundamental lack of knowledge about the pathophysiology of EVD. In particular, very little is known about human immune responses to Ebola virus. Here we evaluate the physiology of the human T cell immune response in EVD patients at the time of admission to the Ebola Treatment Center in Guinea, and longitudinally until discharge or death. Through the use of multiparametric flow cytometry established by the European Mobile Laboratory in the field, we identify an immune signature that is unique in EVD fatalities. Fatal EVD was characterized by a high percentage of CD4(+) and CD8(+) T cells expressing the inhibitory molecules CTLA-4 and PD-1, which correlated with elevated inflammatory markers and high virus load. Conversely, surviving individuals showed significantly lower expression of CTLA-4 and PD-1 as well as lower inflammation, despite comparable overall T cell activation. Concomitant with virus clearance, survivors mounted a robust Ebola-virus-specific T cell response. Our findings suggest that dysregulation of the T cell response is a key component of EVD pathophysiology.

Mechanisms of autoimmunity in the non-obese diabetic mouse: effector/regulatory cell equilibrium during peak inflammation

Immune imbalance in autoimmune disorders such as type 1 diabetes may originate from aberrant activities of effector cells or dysfunction of suppressor cells. All possible defective mechanisms have been proposed for diabetes-prone species: (i) quantitative dominance of diabetogenic cells and decreased numbers of regulatory T cells, (ii) excessive aggression of effectors and defective function of suppressors, (iii) perturbed interaction between effector and suppressor cells, and (iv) variations in sensitivity to negative regulation. The experimental evidence available to date presents conflicting information on these mechanisms, with identification of perturbed equilibrium on the one hand and negation of critical role of each mechanism in propagation of diabetic autoimmunity on the other hand. In our analysis, there is no evidence that inherent abnormalities in numbers and function of effector and suppressor T cells are responsible for the immune imbalance responsible for propagation of type 1 diabetes as a chronic inflammatory process. Possibly, the experimental tools for investigation of these features of immune activity are still underdeveloped and lack sufficient resolution, in the presence of the extensive biological viability and functional versatility of effector and suppressor elements.

Stable activity of diabetogenic cells with age in NOD mice: dynamics of reconstitution and adoptive diabetes transfer in immunocompromised mice

The non-obese diabetic (NOD) mouse is a prevalent disease model of type 1 diabetes. Immune aberrations that cause and propagate autoimmune insulitis in these mice are being continually debated, with evidence supporting both dominance of effector cells and insufficiency of suppressor mechanisms. In this study we assessed the behaviour of NOD lymphocytes under extreme expansion conditions using adoptive transfer into immunocompromised NOD.SCID (severe combined immunodeficiency) mice. CD4(+)  CD25(+) T cells do not cause islet inflammation, whereas splenocytes and CD4(+)  CD25(-) T cells induce pancreatic inflammation and hyperglycaemia in 80-100% of the NOD.SCID recipients. Adoptively transferred effector T cells migrate to the lymphoid organs and pancreas, proliferate, are activated in the target organ in situ and initiate inflammatory insulitis. Reconstitution of all components of the CD4(+) subset emphasizes the plastic capacity of different cell types to adopt effector and suppressor phenotypes. Furthermore, similar immune profiles of diabetic and euglycaemic NOD.SCID recipients demonstrate dissociation between fractional expression of CD25 and FoxP3 and the severity of insulitis. There were no evident and consistent differences in diabetogenic activity and immune reconstituting activity of T cells from pre-diabetic (11 weeks) and new onset diabetic NOD females. Similarities in immune phenotypes and variable distribution of effector and suppressor subsets in various stages of inflammation commend caution in interpretation of quantitative and qualitative aberrations as markers of disease severity in adoptive transfer experiments.

CD18 is required for optimal lymphopenia-induced proliferation of mouse T cells

Lymphocyte numbers are tightly regulated; with acute lymphopenia, T cell numbers are reestablished through lymphopenia-induced proliferation. In contrast to the costimulation requirements of antigen-driven proliferation, a number of costimulatory molecules are not required for lymphopenia-induced proliferation. However, the requirement for major histocompatibility complex (MHC)-T cell receptor (TCR) interactions and the enhanced lymphopenia-induced proliferation in T cells with higher TCR affinity argue for a role for surface molecules that contribute to efficient MHC-TCR interactions, in particular adhesion molecules. CD18 is an integrin that contributes to the activation of peripheral and intestinal T cells through adhesive and costimulatory mechanisms. We found that CD18 is required for optimal polyclonal and monoclonal CD4+ T cell lymphopenia-induced proliferation in recombination-activating gene 1-deficient (RAG-1-/-) mice; this requirement persisted over time. Uniquely, the dependency on CD18 in CD4+ T cells is in the rapid proliferation in RAG-1-/- recipients and in the slow homeostatic proliferation in irradiated Balb/c recipients. Consistent with the proposed role for intestinal microbiota in lymphopenia-induced rapid proliferation in RAG-/- mice, we observed a significant reduction in rapid proliferation upon treatment of mice with antibiotics; however, the dependency on CD18 for optimal lymphopenia-induced proliferation persisted. Moreover, the dependency for CD18 is maintained over a wide range of numbers of initially transferred T cells, including a low number of initially transferred T cells, when the drive for proliferation is very strong and proliferation is more rapid. Overall, these data argue for an essential and broad role for CD18 in lymphopenia-induced proliferation.

Arthritogenic T cells drive the recovery of autoantibody-producing B cell homeostasis and the adoptive transfer of arthritis in SCID mice

T cells orchestrate joint inflammation in rheumatoid arthritis (RA), but B cells/B cell-derived factors are also involved in disease pathogenesis. The goal of this study was to understand the role of antigen-specific T and B cells in the pathological events of arthritis, which is impossible to study in humans due to the small number of antigen-specific cells. To determine the significance of antigen-specific lymphocytes and antibodies in the development of an autoimmune mouse model of RA, we generated TCR transgenic (TCR-Tg) mice specific for the dominant arthritogenic epitope of cartilage proteoglycan (PG) and performed a series of combined transfers of T cells, B cells and autoantibodies into BALB/c.Scid mice. The adoptive transfer of highly purified T cells from naive TCR-Tg, arthritic TCR-Tg or arthritic wild-type mice induced arthritis in SCID recipients, but the onset and severity of the disease were dependent on the sequential events of the T cell-supported reconstitution of PG-specific B cells and autoantibodies. The presence of activated PG-specific T cells was critical for disease induction, establishing a unique milieu for the selective homeostasis of autoantibody-producing B cells. In this permissive environment, anti-PG autoantibodies bound to cartilage and induced activation of the complement cascade, leading to irreversible cartilage destruction in affected joints. These findings may lead to a better understanding of the complex molecular and cellular mechanisms of RA.

Quantitative monitoring of mouse lung tumors by magnetic resonance imaging

Primary lung cancer remains the leading cause of cancer-related death in the Western world, and the lung is a common site for recurrence of extrathoracic malignancies. Small-animal (rodent) models of cancer can have a very valuable role in the development of improved therapeutic strategies. However, detection of mouse pulmonary tumors and their subsequent response to therapy in situ is challenging. We have recently described MRI as a reliable, reproducible and nondestructive modality for the detection and serial monitoring of pulmonary tumors. By combining respiratory-gated data acquisition methods with manual and automated segmentation algorithms described by our laboratory, pulmonary tumor burden can be quantitatively measured in approximately 1 h (data acquisition plus analysis) per mouse. Quantitative, analytical methods are described for measuring tumor burden in both primary (discrete tumors) and metastatic (diffuse tumors) disease. Thus, small-animal MRI represents a novel and unique research tool for preclinical investigation of therapeutic strategies for treatment of pulmonary malignancies, and it may be valuable in evaluating new compounds targeting lung cancer in vivo.

The inhibitory role of b7-h4 in antitumor immunity: association with cancer progression and survival

B7-H4 is one of the most recently identified members of B7 superfamily of costimulatory molecules serving as an inhibitory modulator of T-cell response. B7-H4 is broadly expressed in human peripheral tissues and inducibly expressed in immune cells. The expression of B7-H4 has been observed in various types of human cancer tissues, and its soluble form has been detected in blood samples from cancer patients. However, its precise physiological role is still elusive, as its receptor has not been identified and the expression levels are not consistent. This paper summarizes the pertinent data on the inhibitory role of B7-H4 in antitumor immunity and its association with cancer progression and survival in human patients. The paper also discusses the clinical significance of investigating B7-H4 as potential markers for cancer diagnosis and prognosis, and as therapeutic targets.

Adaptive and innate transforming growth factor beta signaling impact herpes simplex virus 1 latency and reactivation

Innate and adaptive immunity play important protective roles by combating herpes simplex virus 1 (HSV-1) infection. Transforming growth factor β (TGF-β) is a key negative cytokine regulator of both innate and adaptive immune responses. Yet, it is unknown whether TGF-β signaling in either immune compartment impacts HSV-1 replication and latency. We undertook genetic approaches to address these issues by infecting two different dominant negative TGF-β receptor type II transgenic mouse lines. These mice have specific TGF-β signaling blockades in either T cells or innate cells. Mice were ocularly infected with HSV-1 to evaluate the effects of restricted innate or adaptive TGF-β signaling during acute and latent infections. Limiting innate cell but not T cell TGF-β signaling reduced virus replication in the eyes of infected mice. On the other hand, blocking TGF-β signaling in either innate cells or T cells resulted in decreased latency in the trigeminal ganglia of infected mice. Furthermore, inhibiting TGF-β signaling in T cells reduced cell lysis and leukocyte infiltration in corneas and trigeminal ganglia during primary HSV-1 infection of mice. These findings strongly suggest that TGF-β signaling, which generally functions to dampen immune responses, results in increased HSV-1 latency.

Dendritic cells transfected with PD-L1 recombinant adenovirus induces T cell suppression and long-term acceptance of allograft transplantation

The purpose of this study is to assess the potential of dendritic cells transfected with PD-L1 recombinant adenovirus induces CD8+ T cell suppression and kidney allograft tolerance. To prove it, DCs transfected with PD-L1 recombinant adenovirus (DC/Ad-PD-L1) were transferred into the MHC-mismatched rat kidney transplants. After kidney transplantation, the mixed lymphocyte reaction (MLR) assay and kidney function were analyzed. The results demonstrated that after administration of DC/Ad-PD-L1, the proliferation, cytokines secretion and activation marker expression of CD8+ T cells were suppressed. In addition, DC/Ad-PD-L1 could improve kidney function and survival of transplants. The findings suggested that DC/Ad-PD-L1 could induce CD8+ T cell tolerance and lead to kidney allograft tolerance, which provided a promising finding for clinical application.

Immunosuppressive therapy exacerbates autoimmunity in NOD mice and diminishes the protective activity of regulatory T cells

Mounting evidence indicates that immunosuppressive therapy and autologous bone marrow transplantation are relatively inefficient approaches to treat autoimmune diabetes. In this study we assessed the impact of immunosuppression on inflammatory insulitis in NOD mice, and the effect of radiation on immunomodulation mediated by adoptive transfer of various cell subsets. Sublethal radiation of NOD females at the age of 14 weeks (onset of hyperglycemia) delayed the onset of hyperglycemia, however two thirds of the mice became diabetic. Adoptive transfer of splenocytes into irradiated NON and NOD mice precipitated disease onset despite increased contents of CD25(+)FoxP3(+) T cells in the pancreas and regional lymphatics. Similar phenotypic changes were observed when CD25(+) T cells were infused after radiation, which also delayed disease onset without affecting its incidence. Importantly, irradiation increased the susceptibility to diabetes in NOD and NON mice (71-84%) as compared to immunomodulation with splenocytes and CD25(+) T cells in naïve recipients (44-50%). Although irradiation had significant and durable influence on pancreatic infiltrates and the fractions of functional CD25(+)FoxP3(+) Treg cells were elevated by adoptive cell transfer, this approach conferred no protection from disease progression. Irradiation was ineffective both in debulking of pathogenic clones and in restoring immune homeostasis, and the consequent homeostatic expansion evolves as an unfavorable factor in attempts to restore self-tolerance and might even provoke uncontrolled proliferation of pathogenic clones. The obstacles imposed by immunosuppression on abrogation of autoimmune insulitis require replacement of non-specific immunosuppressive therapy by selective immunomodulation that does not cause lymphopenia.

Blockade of programmed death ligand 1 enhances the therapeutic efficacy of combination immunotherapy against melanoma

Inhibition of antitumor T cell responses can be mediated by the productive interaction between the programmed death-1 (PD-1) receptor on T cells and its ligand PD-L1. PD-L1 is highly expressed on both murine bone marrow-derived dendritic cells (DCs) and B16 melanoma. In this study, in vitro blockade of PD-L1 interaction on DCs led to enhanced IFN-gamma production and cytotoxicity by Ag-specific T cells. In vivo, the systemic administration of anti-PD-L1 Ab plus melanoma peptide-pulsed DCs resulted in a higher number of melanoma peptide-specific CD8(+) T cells, but this combination was insufficient to delay the growth of established B16 melanoma. Although the addition of 600 rad of total body irradiation delayed tumor growth, further adoptive transfer of Ag-specific CD8(+) T cells was needed to achieve tumor regression and long-term survival of the treated mice. Lymphopenic mice treated with anti-PD-L1 Ab demonstrated increased activation and persistence of adoptively transferred T cells, including a higher number of CD8(+) T cells infiltrating the tumor mass. Together, these studies support the blocking of PD-L1 signaling as a means to enhance combined immunotherapy approaches against melanoma.