Programmed Death-1 Signaling Research Articles

PD-1 signaling limits expression of phospholipid phosphatase 1 and promotes intratumoral CD8+ T cell ferroptosis

The tumor microenvironment (TME) promotes metabolic reprogramming and dysfunction in immune cells. Here, we examined the impact of the TME on phospholipid metabolism in CD8+ Tcells. In lung cancer, phosphatidylcholine (PC) and phosphatidylethanolamine (PE) were lower in intratumoral CD8+ Tcells than in circulating CD8+ Tcells. Intratumoral CD8+ Tcells exhibited decreased expression of phospholipid phosphatase 1 (PLPP1), which catalyzes PE and PC synthesis. Tcell-specific deletion of Plpp1 impaired antitumor immunity and promoted Tcell death by ferroptosis. Unsaturated fatty acids in the TME stimulated ferroptosis of Plpp1-/- CD8+ Tcells. Mechanistically, programmed death-1 (PD-1) signaling in CD8+ Tcells induced GATA1 binding to the promoter region Plpp1 and thereby suppressed Plpp1 expression. PD-1 blockade increased Plpp1 expression and restored CD8+ Tcell antitumor function but did not rescue dysfunction of Plpp1-/- CD8+ Tcells. Thus, PD-1 signaling regulates phospholipid metabolism in CD8+ Tcells, with therapeutic implications for immunotherapy.

Differential expression of programmed death 1 (PD-1) on various immune cells and its role in human leprosy.

Leprosy is a chronic bacterial disease caused by Mycobacterium leprae. Leprosy patients have been found to have defects in T cells activation, which is critical to the clearance of the bacilli. Treg cell suppression is mediated by inhibitory cytokines such as IL10, IL-35 and TGF-β and its frequency is higher in leprosy patients. Activation and overexpression of programmed death 1 (PD-1) receptor is considered to one of the pathways to inhibit T-cell response in human leprosy. In the current study we address the effect of PD-1 on Tregs function and its immuno-suppressive function in leprosy patients. Flow cytometry was used to evaluate the expression of PD-1 and its ligands on various immune cells T cells, B cells, Tregs and monocytes. We observed higher expression of PD-1 on Tregs is associated with lower production of IL-10 in leprosy patients. PD-1 ligands on T cells, B cells, Tregs and monocytes found to be higher in the leprosy patients as compared to healthy controls. Furthermore, in vitro blocking of PD-1 restores the Tregs mediated suppression of Teff and increase secretion of immunosuppressive cytokine IL-10. Moreover, overexpression of PD-1 positively correlates with disease severity as well as Bacteriological Index (BI) among leprosy patients. Collectively, our data suggested that PD-1 overexpression on various immune cells is associated with disease severity in human leprosy. Manipulation and inhibition of PD-1 signaling pathway on Tregs alter and restore the Treg cell suppression activity in leprosy patients.

Engineered DBCO+PD-1 Nanovesicles Carrying 1-MT for Cancer-Targeted Immunotherapy.

Liver cancer cells evade immune surveillance and anticancer response through various pathways, including the programmed death-ligand 1 (PD-L1)/programmed death-1 (PD-1) immune checkpoint axis that exhausts CD8+ T cells. Inhibitors or antibodies of the PD-L1/PD-1 signaling axis are considered promising drugs for cancer immunotherapy and exhibit favorable clinical responses. However, adverse effects, immune tolerance, and delivery barriers of most patients limit the clinical application of PD-L1/PD-1 antibodies. Thus, it is critical to develop a novel delivery strategy to enhance anticancer immunotherapy. In this study, we bioengineered cell membrane-derived nanovesicles (NVs) presenting PD-1 proteins and dibenzocyclooctyne (DBCO) to encapsulate 1-methyltryptophan (1-MT) (DBCO+PD-1@1-MT NVs). DBCO can specifically interact with N-azidoacetylmannosamine-tetraacetylate (Ac4ManN3) labeled onto metabolic cells for targeted killing of cancers. We next explored the effects of DBCO+PD-1@1-MT NVs on anticancer Hepa1-6 cells in vitro and in vivo. Results showed that PD-1@1-MT NVs dramatically inhibited Hepa1-6 proliferation, promoted peripheral blood mononuclear cell (PBMC) expansion, and strengthened anticancer therapy via blockading the PD-1/PD-L1 immune checkpoint axis, owing to the 1-methyltryptophan (1-MT) enhancement of anticancer immunotherapy efficacy through suppressing the activity of indoleamine 2,3-dioxygenase (IDO). Thus, 1-MT was encapsulated into PD-1 NVs to synergistically enhance cancer immunotherapy. Results have shown that PD-1@1-MT NVs obviously attenuated tumor growth, promoting IFN-γ production, increasing the T cells infiltration in tumors and spleens, and improving the survival period of tumor-bearing mice compared to monotherapy. Therefore, we propose a promising delivery strategy of the combination of DBCO+PD-1 NVs and 1-MT for specific and effective cancer-targeted immunotherapy.

The Programmed Death-1 Signaling Axis Modulates Inflammation and LV Structure/Function in a Stress-Induced Cardiomyopathy Model

The role of immune checkpoints in the setting of tissue injury remains unknown. Using an experimental model of isoproterenol (ISO)-induced stress cardiomyopathy, we show that ISO-induced myocardial injury provokes tissue-autonomous up-regulation of the programmed death-1 (PD-1):programmed death ligand (PD-L) axis in cardiac resident innate immune cells and T cells. PD-1 signaling was responsible for modulating the acute inflammatory response, as well as normalization of impaired left ventricular structure and function after ISO injection. Necrotic cardiac extracts were sufficient to increase the expression of PD-1 in macrophages and T cells invitro. Viewed together these studies suggest that the PD-1:PD-L signaling axis regulates immune responses to cardiac tissue injury and is important for restoring myocardial homeostasis.

Programmed Death-1 Deficiency Aggravates Motor Dysfunction in MPTP Model of Parkinson's Disease by Inducing Microglial Activation and Neuroinflammation in Mice.

Abundant reactive gliosis and neuroinflammation are typical pathogenetic hallmarks of brains in Parkinson's disease (PD) patients, but regulation mechanisms are poorly understood. We are interested in role of programmed death-1 (PD-1) in glial reaction, neuroinflammation and neuronal injury in PD pathogenesis. Using PD mouse model and PD-1 knockout (KO) mice, we designed wild-type-control (WT-CON), WT-1-methyl-4-phenyl-1,2,3,6-tetrahydropyridine (WT-MPTP), PD-1-KO-control (KO-CON) and PD-1-KO-MPTP (KO-MPTP), and observed motor dysfunction of animal, morphological distribution of PD-1-positive cells, dopaminergic neuronal injury, glial activation and generation of inflammatory cytokines in midbrains by motor behavior detection, immunohistochemistry and western blot. WT-MPTP mouse model exhibited decrease of PD-1/Iba1-positive microglial cells in the substantia nigra compared with WT-CON mice. By comparison of four groups, PD-1 deficiency showed exacerbation in motor dysfunction of animals, decreased expression of TH protein and TH-positive neuronal protrusions. PD-1 deficiency enhanced microglial activation, production of proinflammatory cytokines like inducible nitric oxide synthase, tumor necrosis factor-α, interleukin-1β and interleukin-6, and expression and phosphorylation of AKT and ERK1/2 in the substantia nigra of MPTP model. We concluded that PD-1 deficiency could aggravate motor dysfunction of MPTP mouse model by inducing microglial activation and neuroinflammation in midbrains, suggesting that PD-1 signaling abnormality might be possibly involved in PD pathogenesis.

Low-Dose Decitabine Restores Immune Tolerance in ITP By Modulating Regulatory T Cells

Immune thrombocytopenia (ITP) is an aquired autoimmune disease triggered by increased platelet destruction and impaired platelet production. Loss of immune tolerance is considered to be the pivotal mechanism of ITP. Decitabine, a hypomethylating agent promoting cell differentiation at low dose, has been applied in the treatment of myelodysplastic syndrome (MDS) with a considerable platelet response. Our previous and current studies demonstrated that low-dose decitabine could significantly increase the number of mature polyploidy megakaryocytes and had a long-term efficacy that could not be explained by its role on promoting platelet production in ITP patients. Recent reports have demonstrated that decitabine could decrease the production of interferon-γ (IFN-γ) and tumor necrosis factor-a (TNF-a), and increase immune suppressive regulatory T cells. Thus, low-dose decitabine might correct the loss of immune tolerance to induce a more durable response in patients with ITP.CD4+CD25+Foxp3+ regulatory T cells (Tregs), which play an important role in maintenance of peripheral tolerance, were reported to be decreased in number and function in ITP (Stasi R et. al. Blood 2008). In the in vitro study, peripheral blood mononuclear cells (PBMCs) were isolated and cultured with 100nM decitabine or PBS for 72h. We performed flow cytometry to determine the percentage of Tregs. It was shown that the percentage of Tregs in PBMCs and CD4+ T cells were significantly elevated after decitabine treatment. We also sorted the CD4+CD25+CD127- Tregs from ITP patients and co-cultured them with CFSE-labeled CD4+CD25-T cells to evaluate the suppressive activity of Tregs. The results indicated that the inhibitory function of Tregs after decitbine treatments was significantly elevated compared with controls.As compared to healthy individuals, patients with ITP also had increased number of TH1, TH17, TH22, Bregs and CD16+ monocytes. We subsequently investigated the effects of low-dose decitabine on those cells in patients with active ITP. Three cycles of decitabine were administered intravenously at a dose of at 3.5 mg/m2 for 3 days per cycle with a 4-week interval between cycles. After decitabine treatment, there was a significant increase in the relative number of CD25+Foxp3+ Tregs in the CD4+ T cell population. We also observed an increase in Tregs function after the decitabine treatment. In contrast, decitabine could significantly decrease the percentage of CD4+IFN-γ+TH1 in the CD4+T cell population and the percentage of CD16+monoyctes. However, we have not observed the effect of decitabine on the CD4+IFN-γ-CD17+TH17, CD4+IFN-γ-CD22+TH22, and CD19+CD24+CD38+Bregs by now.We further established the murine ITP model by transferring the splenocytes of C57BL/6 CD61 knockout mice, which were immunized against platelets from wild-type syngeneic C57BL/6 mice into severe combined immunodeficient (SCID) mice. We treated the ITP mice model with a low-dose range of decitabine (0.01, 0.03 or 0.10 mg/kg) intravenously three times a week. Our data showed a significant effect on PLT increase and the expansion of the Tregs population and the suppression of TH1 cells and CD16+ monocytes .In addition, programmed death-1 (PD-1) is a co-receptor that is expressed predominantly by T cells as well as B cells, monocytes and was found to be lower on the PBMCs and in serum of ITP patients (Zhong J et. al. Hematology. 2016). And research has reported that PD-1 signaling pathway is important in the pathogenesis of autoimmune diseases by inhibition of self-reactive T cells and increasing the development and functions of Tregs. Furthermore, it was reported that the expression of PD-1 is enhanced by decitabine in MDS (Yang H et. al. Leukemia 2014). In our current studies, decreased PD-1 expression on CD4+T cells of ITP patients was observed and decitabine could elevate the PD-1 expression on CD4+T cells after the decitabine treatment in ITP patients. Therefore, decitabine may correct the loss of immune tolerance by upregulating the Expression of PD-1 and be a promising therapeutic strategy for the management in ITP patients. [Display omitted] DisclosuresNo relevant conflicts of interest to declare.

The Clinical and Biological Effects of PD-1 Expression on Tumor Cells in Diffuse Large B-Cell Lymphoma

The clinical and biological significance of programmed death-1 (PD-1) expression by B-lymphoma cells is largely unknown. Here, using multicolor immunofluorescent staining (MC-IF), we investigated PD-1 and PD-L1 expression in PAX5+ (B-lymphoma), CD68+ (macrophage), or CD3+ (T-cell) cells in formalin-fixed, paraffin-embedded samples of 32 consecutive patients with de novo diffuse large B-cell lymphoma (DLBCL) treated with rituximab plus chemotherapy. PD-1- and PD-L1-expressing PAX5+ cells were observed in 59% and 3% of the patients, respectively. PD-1-expressing CD3+ lymphocytes and PD-L1-expressing CD68+ macrophages were observed in 89% and 86% of the patients, respectively. PD-L1 expression on PAX5+ lymphoma cells or CD68+ macrophages and PD-1 expression on CD3+ lymphocytes were not correlated with prognosis. However, patients with PD-1 expression on lymphoma cells showed shorter progression-free survival than those lacking PD-1-expressing lymphoma cells (p = 0.033). Furthermore, genetically modified PD-1-knockout human B-lymphoma VAL cells showed reduced cell growth and migration, and decreased S6 kinase phosphorylation than VAL/mock cells. Our data suggest that PD-1 expression on DLBCL cells detected by MC-IF was associated with poor prognosis and cell-intrinsic PD-1 signaling was related with cell growth and migration in a subpopulation of B-cell lymphoma. These findings may allow the development of distinct DLBCL subtypes affecting prognosis.

Autoreactivity of Peripheral Helper T Cells in the Joints of Rheumatoid Arthritis.

Autoreactive CD4 T cells are thought to play pivotal roles in the pathogenesis of rheumatoid arthritis (RA). Recently, a subset of CD4 T cells that express high levels of programmed death-1 (PD-1) but are distinct from follicular helper T cells have been identified in the joints of RA patients and named peripheral helper T (Tph) cells. Because PD-1 is expressed on T cells chronically stimulated with the Ags, we tested a hypothesis that Tph cells are the pathogenic autoreactive CD4 T cells in RA. We found that human Tph cells in RA joints produce proinflammatory effector cytokines, including IFN-γ, TNF-α, and GM-CSF, in addition to B cell-helping cytokines, such as IL-21 and CXCL13. Flow cytometric analysis showed different bias of TCR Vβ usage between PD-1high Tph cells and PD-1low/neg CD4 T cells, including Th1 cells, in the joint or memory CD4 T cells in the peripheral blood, whereas there was little difference between the latter two subsets. In line with this, deep sequencing of TCR demonstrated an overlap of expanded clones between peripheral blood memory CD4 T cells and PD-1low/neg CD4 T cells but not Tph cells in the joint. Interestingly, Tph cells preferentially exhibited autologous MLR in vitro, which required recognition of self-MHC class II and was pronounced by blocking PD-1 signaling. Taken together, these results suggest that Tph cells are the pathogenic autoreactive CD4 T cells in RA, which expand locally in the joints and are regulated by PD-1 signaling.

Differential expression of programmed death-1 and its ligand, programmed death ligand-1 in oral squamous cell carcinoma with and without oral submucous fibrosis

ObjectiveThe aim of our study was to investigate the expression of programmed death ligand-1 (PD-L1)/programmed death-1 (PD-1) between oral squamous cell carcinoma (OSCC) patients with and without oral submucous fibrosis (OSF), and its correlation with clinic-pathologic features and its prognostic value. MethodsPD-L1 and PD-1 expression was evaluated by immunohistochemical staining, double immunofluorescent staining and real-time PCR, and the correlation of PD-L1/PD-1 expression with clinical outcome was assessed. ResultsThe level of PD-L1 expression was significantly higher in OSCC with OSF than in OSCC without OSF (p = 0.006). Moreover, PD-L1 expression was strongly correlated with lymph node metastasis (p = 0.016), and advanced tumor stage (p = 0.030). Increased PD-L1 expression was positively correlated with the incidence of OSCC with OSF (p = 0.006, p = 0.008, respectively). PD-L1 expression was an independent marker of unfavorable prognosis (p = 0.035, p = 0.048, respectively). High PD-L1 expression had a significantly worse outcome in OSCC patients with OSF (p = 0.014). Double immunofluorescent staining showed that OSCC with OSF were more strongly expressed both PD-L1 and PD-1 than OSCC without OSF. Moreover, the expression of PD-L1 were upregulated in OSCC tissues than normal control (p = 0.0422), and both PD-L1 and PD-1 was significantly higher in OSCC with OSF than OSCC without OSF tissues (p = 0.0043 and, p = 0.0012, respectively). ConclusionsThe present study suggested that PD-L1 may be an unfavorable indicator for prognosis. PD-L1/PD-1 signaling might play an important role in the malignant transformation of OSF, and targeting PD-L1/PD-1 signaling may be a new therapeutic strategy for OSCC, especially in OSCC patients with OSF.

Issue Highlights

IUBMB LifeVolume 72, Issue 8 p. 1545-1545 ISSUE HIGHLIGHTSFree Access Issue Highlights First published: 22 July 2020 https://doi.org/10.1002/iub.2360AboutSectionsPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinkedInRedditWechat 1649 Cytotoxic T lymphocytes exert potent antitumor activity by recognizing the antigen peptide and major histocompatibility complex (MHC) on cancer cells through the T-cell receptor (TCR). Adoptive T-cell therapy (ACT) is a treatment method in which tumor antigen-specific T cells from a cancer patient are activated and expanded in vitro, and then transplanted back into the cancer patient. One of the limiting factors of ACT is that the administered T cells are rendered dysfunctional due to the immunosuppressive tumor microenvironment. We attempted to inhibit interaction between programmed death-1 (PD-1) and its ligand (PD-L1) by genetically modifying T cell medicine to express the anti-PD-L1 molecules. Anti-PD-L1 molecule expression was functional in avoiding T-cell dysfunction by PD-L1/PD-1 signaling. Our concept of anti-PD-L1 molecule-expressing T-cell medicine is thus expected to improve the efficacy of ACT. REFERENCES 1Kento Fujiwara, Kazuki Shigematsu, Masashi Tachibana, Naoki Okada. Development and functional analysis of an anticancer T-cell medicine with immune checkpoint inhibitory ability. IUBMB Life. 2020, 72, 1649– 1658. Volume72, Issue8August 2020Pages 1545-1545 ReferencesRelatedInformation

PD1 Blockade in Cancer: Impact on Myeloid Cells

Programmed death 1 (PD1) has emerged as a major inhibitor of antitumor T cells, and anti-PD1 therapies have demonstrated clinical efficacy in multiple cancers. However, the impact of PD1 on other immune cells had remained unclear. A recent study by Strauss et al. describes how myeloid cell-intrinsic PD1 signaling limits myelopoiesis in cancer pertinent to anti-PD1 therapies.

PD-1 Is Expressed at Low Levels on All Peripheral Blood Natural Killer Cells but Is a Significant Suppressor of NK Function Against PD-1 Ligand Expressing Tumor Targets

PD-1 Is Expressed at Low Levels on All Peripheral Blood Natural Killer Cells but Is a Significant Suppressor of NK Function Against PD-1 Ligand Expressing Tumor Targets

Progress in programmed death-1 signaling pathway in sepsis

Sepsis includes a highly diverse and dynamic mixture of systemic inflammatory response syndrome (SIRS) and compensatory anti-inflammatory response syndrome (CARS). In the past, drugs produced to block the early inflammatory response had little effect on reversing the development of sepsis. Recent studies have shown that the mortality and prognosis of patients are significantly correlated with the immunosuppression of sepsis and the overexpression of co-inhibitory molecules. Programmed death-1 (PD-1) is a recently focused co-inhibitory molecule, which can regulate the functions of a variety of immune cells and participate in innate immunity and acquired immunity. It has important value in risk stratification and prognosis prediction of patients with sepsis, and can be used as one of the intervention targets for immune regulation in sepsis in the future. The role of PD-1 signaling pathway in immunosuppression and its effect on patients' prognosis is reviewed in this article, providing new directions for the treatment of sepsis.

PD-1 signaling affects cristae morphology and leads to mitochondrial dysfunction in human CD8+ T lymphocytes

BackgroundBinding of the programmed death-1 (PD-1) receptor to its ligands (PD-L1/2) transduces inhibitory signals that promote exhaustion of activated T cells. Blockade of the PD-1 pathway is widely used for cancer treatment, yet the inhibitory signals transduced by PD-1 in T cells remain elusive.MethodsExpression profiles of human CD8+ T cells in resting, activated (CD3 + CD28) and PD-1-stimulated cells (CD3 + CD28 + PD-L1-Fc) conditions were evaluated by RNA-seq. Bioinformatic analyses were used to identify signaling pathways differentially regulated in PD-1-stimulated cells. Metabolic analyses were performed with SeaHorse technology, and mitochondrial ultrastructure was determined by transmission electron microscopy. PD-1-regulated mitochondrial genes were silenced using short-hairpin RNA in primary cells. Blue native gel electrophoresis was used to determine respiratory supercomplex assembly.ResultsPD-1 engagement in human CD8+ T cells triggers a specific, progressive genetic program different from that found in resting cells. Gene ontology identified metabolic processes, including glycolysis and oxidative phosphorylation (OXPHOS), as the main pathways targeted by PD-1. We observed severe functional and structural alterations in the mitochondria of PD-1-stimulated cells, including a reduction in the number and length of mitochondrial cristae. These cristae alterations were associated with reduced expression of CHCHD3 and CHCHD10, two proteins that form part of the mitochondrial contact site and cristae organizing system (MICOS). Although PD-1-stimulated cells showed severe cristae alterations, assembly of respiratory supercomplexes was unexpectedly greater in these cells than in activated T cells. CHCHD3 silencing in primary CD8+ T cells recapitulated some effects induced by PD-1 stimulation, including reduced mitochondrial polarization and interferon-γ production following T cell activation with anti-CD3 and -CD28 activating antibodies.ConclusionsOur results suggest that mitochondria are the main targets of PD-1 inhibitory activity. PD-1 reprograms CD8+ T cell metabolism for efficient use of fatty acid oxidation; this mitochondrial phenotype might explain the long-lived phenotype of PD-1-engaged T cells.

Radiotherapy Both Promotes and Inhibits Myeloid-Derived Suppressor Cell Function: Novel Strategies for Preventing the Tumor-Protective Effects of Radiotherapy.

Cancer immunotherapies aimed at neutralizing the programmed death-1 (PD-1) immune suppressive pathway have yielded significant therapeutic efficacy in a subset of cancer patients. However, only a subset of patients responds to antibody therapy with either anti-PD-1 or anti-PD-L1 antibodies. These patients appear to have so-called “hot” tumors containing tumor-reactive T cells. Therefore, checkpoint blockade therapy may be effective in a larger percentage of cancer patients if combined with therapeutics that also activate tumor-reactive T cells. Radiotherapy (RT) is a prime candidate for combination therapy because it facilitates activation of both local antitumor immunity and antitumor immunity at non-radiated, distant sites (abscopal response). However, RT also promotes tumor cell expression of PD-L1 and facilitates the development of myeloid-derived suppressor cells (MDSC), a population of immune suppressive cells that also suppress through PD-L1. This article will review how RT induces MDSC, and then describe two novel therapeutics that are designed to simultaneously activate tumor-reactive T cells and neutralize PD-1-mediated immune suppression. One therapeutic, a CD3xPD-L1 bispecific T cell engager (BiTE), activates and targets cytotoxic T and NKT cells to kill PD-L1+ tumor cells, despite the presence of MDSC. The BiTE significantly extends the survival time of humanized NSG mice reconstituted with human PBMC and carrying established metastatic human melanoma tumors. The second therapeutic is a soluble form of the costimulatory molecule CD80 (sCD80). In addition to costimulating through CD28, sCD80 inhibits PD-1 suppression by binding to PD-L1 and sterically blocking PD-L1/PD-1 signaling. sCD80 increases tumor-infiltrating T cells and significantly extends survival time of mice carrying established, syngeneic tumors. sCD80 does not suppress T cell function via CTLA-4. These studies suggest that the CD3xPD-L1 BiTE and sCD80 may be efficacious therapeutics either as monotherapies or in combination with other therapies such as radiation therapy for the treatment of cancer.

Molecular cloning, expression and characterization of Pekin duck programmed death-1

Programmed death-1 (PD-1) has a pivotal role in the attenuation of adaptive immune responses and peripheral tolerance. Here we describe the identification of the Pekin duck programmed death-1 orthologue (duPD-1). The duPD-1 cDNA encodes a 283-amino acid polypeptide that has an amino acid identity of 70%, 32% and 31% with chicken, murine and human PD-1, respectively. The duck PD-1 gene shares five conserved exons with chicken, murine and human PD-1 genes. A cluster of putative regulatory elements within the conserved region B (CR-B) of the basal promotor is conserved. Homology modeling was most compatible with the two β-sheet IgV domain structure of murine PD-1. Contact residues, shown to be critical for binding of the respective human and murine PD-1 ligands are mostly conserved between avian and mammalian species, whereas residues that define the cytoplasmic immunoreceptor tyrosine-based inhibitory motif (ITIM) and immunoreceptor tyrosine-based switch motif (ITSM) are highly conserved across higher vertebrates and frog. Constitutive expression of duPD-1 transcripts was predominantly found in lymphocyte-rich tissues, and mitogen-stimulation of duck peripheral blood mononuclear cells transiently increased duPD-1 mRNA expression. A soluble duPD-1 protein was expressed and shown to engage the identified duck PD-1 ligands. Our observations show considerable evolutionary conservation between mammalian and avian PD-1 orthologues. This work will facilitate further investigation of the role of PD-1 signaling in adaptive immunity in the Pekin duck, a non-mammalian vertebrate and pathogen host with relevance for human and animal health.

Abstract A174: The anti-LAG-3 antibody REGN3767 promotes immune activation in the tumor microenvironment and enhances antitumor activity of anti-PD-1 antibody REGN2810 in PD-1/LAG-3 humanized mice

Abstract The immune checkpoint receptor lymphocyte activation gene 3 (LAG-3) inhibits proliferation and cytokine production by activated CD4 and CD8 T-cells upon binding to major histocompatibility complex class II (MHC II). Another inhibitory receptor, programmed death 1 (PD-1), and its ligands PD-L1 and PD-L2, are critical for the establishment and maintenance of peripheral T-cell tolerance. Because PD-1 and LAG-3 signaling in the tumor microenvironment enables tumors to escape immune surveillance, combined targeting of PD-1 and LAG-3 has emerged as a promising therapeutic strategy. REGN3767 is a human monoclonal antibody that binds LAG-3 with high affinity and rescues T-cell function by blocking its interaction with MHC II. Similarly, the human monoclonal antibody REGN2810 blocks PD-1 interaction with PD-L1 and PD-L2. To test the in vivo activity of REGN3767 alone or in combination with REGN2810, we generated humanized PD-1/LAG-3 knock-in mice, in which the extracellular domains of mouse Pdcd1 and Lag3 genes were replaced with the corresponding regions of human PD-1 and human LAG-3, respectively. In these mice, combined REGN2810 and REGN3767 therapy reduced MC38.Ova tumor growth and prolonged survival, compared to REGN2810 and REGN3767 monotherapies. To explore the underlying molecular mechanisms, we conducted RNA sequencing and RT PCR analyses of MC38.Ova tumors in PD-1/LAG-3 humanized mice following administration of one or two doses of REGN2810, REGN3767, or the combination. Both REGN3767 and REGN2810 promoted robust transcriptional changes in tumors, and combined PD-1 and LAG-3 blockade resulted in enhanced immune activation signatures. Analysis of differentially expressed genes revealed T-cell expansion and activation induced by either antibody monotherapy. While tumor immune responses to REGN3767 were delayed compared to REGN2810, both agents induced similar gene changes via shared pathways. In addition to T-cell activation, REGN2810 or REGN3767 treatments engaged other tumor-infiltrating leukocytes, including neutrophils, myeloid and NK cells. Stronger tumor growth inhibition in response to REGN2810 or REGN3767 therapy was associated with more robust immune activation signatures. Combination of REGN2810 and REGN3767 enhanced antitumor efficacy, resulting in gene expression changes not seen with either monotherapy. The combination therapy also enhanced immune responses promoted by either antibody alone, including genes associated with T-cell activation and effector function. REGN2810 and REGN3767 combination also increased the expression of other checkpoint and costimulatory molecules, including CTLA-4, CD40 and VISTA. The robust intratumoral immune activation associated with antitumor efficacy in preclinical setting supports the clinical development of REGN2810 and REGN3767 as a combination cancer immunotherapy. Citation Format: Elena Burova, Gabor Halls, Omaira Allbritton, Wen Zhang, William Olson, Markus Mohrs, Gavin Thurston, Ella Ioffe. The anti-LAG-3 antibody REGN3767 promotes immune activation in the tumor microenvironment and enhances antitumor activity of anti-PD-1 antibody REGN2810 in PD-1/LAG-3 humanized mice [abstract]. In: Proceedings of the Fourth CRI-CIMT-EATI-AACR International Cancer Immunotherapy Conference: Translating Science into Survival; Sept 30-Oct 3, 2018; New York, NY. Philadelphia (PA): AACR; Cancer Immunol Res 2019;7(2 Suppl):Abstract nr A174.

Percutaneous ablative cryoimmunotherapy for micrometastaic abscopal effect: No complications

Recent studies have shown efficacy of nivolumab, a monoclonal antibody specific for an immunoregulatory protein termed programmed death 1 (PD-1), against metastatic renal cell carcinoma. PD-1 is a transmembrane protein expressed on T cells that suppresses activation upon binding to its ligands, which may be secreted paraneoplastically by various cancers. Inhibition of PD-1 signaling via nivolumab may sensitize tumor-specific T lymphocytes in the immunosuppressive tumor microenvironment. Systemic elimination of micrometastases requires robust activation and proliferation of tumor antigen stimulated T cells. Cryoablation lyses tumor cell membranes but leaves intracellular tumor antigens intact for recognition by effectors systemically, while eliminating permissive T cell subtypes locally. This single case report describes CT-guided percutaneous cryoablation of a metastatic renal cell carcinoma with local administration of nivolumab to simultaneously debulk the primary tumor, sensitize effector T cells against tumor antigens, and augment the systemic immune response elicited against established metastases. One month follow up PET scan revealed decreased uptake in the two smaller metastatic bone lesions with the smallest lesion completely eliminated. The largest metastatic bone lesion was slightly decreased in size and exhibited slightly increased uptake. The patient's presenting complaint of hip pain was abrogated, allowing her to resume independent ambulation. CT-guided percutaneous cryoablation is minimally invasive and preserves tumor antigens, which are subsequently presented to tumor-specific T cells; their differentiation into cytotoxic T cells may be guided and their proliferation may be augmented by local administration of immunostimulatory pharmacotherapy at the time of the procedure.

Hormonal vitamin D up-regulates tissue-specific PD-L1 and PD-L2 surface glycoprotein expression in humans but not mice

PD-L1 (programmed death ligand 1) and PD-L2 are cell-surface glycoproteins that interact with programmed death 1 (PD-1) on T cells to attenuate inflammation. PD-1 signaling has attracted intense interest for its role in a pathophysiological context: suppression of anti-tumor immunity. Similarly, vitamin D signaling has been increasingly investigated for its non-classical actions in stimulation of innate immunity and suppression of inflammatory responses. Here, we show that hormonal 1,25-dihydroxyvitamin D (1,25D) is a direct transcriptional inducer of the human genes encoding PD-L1 and PD-L2 through the vitamin D receptor, a ligand-regulated transcription factor. 1,25D stimulated transcription of the gene encoding PD-L1 in epithelial and myeloid cells, whereas the gene encoding the more tissue-restricted PD-L2 was regulated only in myeloid cells. We identified and characterized vitamin D response elements (VDREs) located in both genes and showed that 1,25D treatment induces cell-surface expression of PD-L1 in epithelial and myeloid cells. In co-culture experiments with primary human T cells, epithelial cells pretreated with 1,25D suppressed activation of CD4+ and CD8+ cells and inhibited inflammatory cytokine production in a manner that was abrogated by anti-PD-L1 blocking antibody. Consistent with previous observations of species-specific regulation of immunity by vitamin D, the VDREs are present in primate genes, but neither the VDREs nor the regulation by 1,25D is present in mice. These findings reinforce the physiological role of 1,25D in controlling inflammatory immune responses but may represent a double-edged sword, as they suggest that elevated vitamin D signaling in humans could suppress anti-tumor immunity.

PD-1 Blockade Promotes Epitope Spreading in Anticancer CD8+ T Cell Responses by Preventing Fratricidal Death of Subdominant Clones To Relieve Immunodomination.

The interactions between programmed death-1 (PD-1) and its ligands hamper tumor-specific CD8+ T cell (TCD8) responses, and PD-1-based "checkpoint inhibitors" have shown promise in certain cancers, thus revitalizing interest in immunotherapy. PD-1-targeted therapies reverse TCD8 exhaustion/anergy. However, whether they alter the epitope breadth of TCD8 responses remains unclear. This is an important question because subdominant TCD8 are more likely than immunodominant clones to escape tolerance mechanisms and may contribute to protective anticancer immunity. We have addressed this question in an in vivo model of TCD8 responses to well-defined epitopes of a clinically relevant oncoprotein, large T Ag. We found that unlike other coinhibitory molecules (CTLA-4, LAG-3, TIM-3), PD-1 was highly expressed by subdominant TCD8, which correlated with their propensity to favorably respond to PD-1/PD-1 ligand-1 (PD-L1)-blocking Abs. PD-1 blockade increased the size of subdominant TCD8 clones at the peak of their primary response, and it also sustained their presence, thus giving rise to an enlarged memory pool. The expanded population was fully functional as judged by IFN-γ production and MHC class I-restricted cytotoxicity. The selective increase in subdominant TCD8 clonal size was due to their enhanced survival, not proliferation. Further mechanistic studies utilizing peptide-pulsed dendritic cells, recombinant vaccinia viruses encoding full-length T Ag or epitope mingenes, and tumor cells expressing T Ag variants revealed that anti-PD-1 invigorates subdominant TCD8 responses by relieving their lysis-dependent suppression by immunodominant TCD8 To our knowledge, our work constitutes the first report that interfering with PD-1 signaling potentiates epitope spreading in tumor-specific responses, a finding with clear implications for cancer immunotherapy and vaccination.