Anti-angiogenic agents - overcoming tumour endothelial cell anergy and improving immunotherapy outcomes.

Immune checkpoint inhibitors have revolutionized medical oncology, although currently only a subset of patients has a response to such treatment. A compelling body of evidence indicates that anti-angiogenic therapy has the capacity to ameliorate antitumour immunity owing to the inhibition of various immunosuppressive features of angiogenesis. Hence, combinations of anti-angiogenic agents and immunotherapy are currently being tested in >90 clinical trials and 5 such combinations have been approved by the FDA in the past few years. In this Perspective, we describe how the angiogenesis-induced endothelial immune cell barrier hampers antitumour immunity and the role of endothelial cell anergy as the vascular counterpart of immune checkpoints. We review the antitumour immunity-promoting effects of anti-angiogenic agents and provide an update on the current clinical successes achieved when these agents are combined with immune checkpoint inhibitors. Finally, we propose that anti-angiogenic agents are immunotherapies - and vice versa - and discuss future research priorities.

Serial Stimulation of Invariant Natural Killer T Cells with Covalently Stabilized Bispecific T-cell Engagers Generates Antitumor Immunity While Avoiding Anergy.

CD1d-restricted invariant natural killer T cells (iNKT cells) mediate strong antitumor immunity when stimulated by glycolipid agonists. However, attempts to develop effective iNKT cell agonists for clinical applications have been thwarted by potential problems with dose-limiting toxicity and by activation-induced iNKT cell anergy, which limits the efficacy of repeated administration. To overcome these issues, we developed a unique bispecific T-cell engager (BiTE) based on covalent conjugates of soluble CD1d with photoreactive analogues of the glycolipid α-galactosylceramide. Here we characterize the in vivo activities of iNKT cell-specific BiTEs and assess their efficacy for cancer immunotherapy in mouse models using transplantable colorectal cancer or melanoma tumor lines engineered to express human Her2 as a tumor-associated antigen. Systemic administration of conjugated BiTEs stimulated multiple iNKT cell effector functions including cytokine release, secondary activation of NK cells, and induction of dendritic cell maturation and also initiated epitope spreading for tumor-specific CD8+ cytolytic T-cell responses. The antitumor effects of iNKT-cell activation with conjugated BiTEs were further enhanced by simultaneous checkpoint blockade with antibodies to CTLA-4, providing a potential approach for combination immunotherapy. Multiple injections of covalently stabilized iNKT cell-specific BiTEs activated iNKT cells without causing iNKT cell anergy or exhaustion, thus enabling repeated administration for effective and nontoxic cancer immunotherapy regimens. SIGNIFICANCE: Covalently stabilized conjugates that engage the antigen receptors of iNKT cells and target a tumor antigen activate potent antitumor immunity without induction of anergy or depletion of the responding iNKT cells.

PD-L1 Checkpoint Inhibition Narrows the Antigen-Specific T Cell Receptor Repertoire in Chronic Lymphocytic Choriomeningitis Virus Infection.

Checkpoint inhibitors are effective in restoring exhausted CD8+ T cell responses in persistent viral infections or tumors. Several compounds are in clinical use for different malignancies, but trials in patients with chronic viral infections have also been conducted. In a mouse model of persistent lymphocytic choriomeningitis virus (LCMV) infection, it was shown that checkpoint inhibitor treatment increased T cell proliferation and functionality, but its influence on the antigen-specific T cell receptor (TCR) repertoire is unknown. NP396-specific CD8+ T cells dominate during acute LCMV infection and are predominantly exhausted during chronic infection. Next-generation sequencing of NP396-specific TCRs showed that exhaustion corresponds with a significantly reduced NP396-specific TCR repertoire diversity: Shannon indices of 4 in immunized mice to 2.6 in persistently infected mice. Anti-PD-L1 treatment during persistent LCMV infection restored NP396-specific T cell responses and reduced viral titers. Nevertheless, anti-PD-L1-treated mice showed an even more narrowed TCR repertoire, with reduced TCR diversity compared to that of persistently infected control mice (Shannon indices of 2.1 and 2.6, respectively). Interestingly, anti-PD-L1 treatment-induced narrowing of the TCR repertoire negatively correlates with functional and physical restoration of the antigen-specific T cell response. Further, we found that private, hyperexpanded TCR clonotypes dominated the T cell response after anti-PD-L1 treatment. Although being private, these top clonotypes from anti-PD-L1-treated mice revealed a more closely related CDR3 motif than those of top clonotypes from persistently infected control mice. In conclusion, although targeting the PD-1/PD-L1 pathway reinvigorates exhausted CD8+ T cells, it fails to restore T cell repertoire diversity.IMPORTANCE Checkpoint inhibitors are effective immunotherapeutics to restore cancer- and virus-induced exhausted CD8+ T cells, by enhancing the quality and survival of immune responses. Although checkpoint inhibitors are already used as therapy against various cancers, not much is known about their multifaceted impact on the exhausted CD8+ T cell receptor (TCR) repertoire. This report describes for the first time the evolvement of an exhausted antigen-specific CD8+ TCR repertoire under checkpoint inhibitor treatment. By using a well-established virus model, we were able to show major shifts toward oligoclonality of the CD8+ TCR repertoire response against a massively exhausted lymphocytic choriomeningitis virus (LCMV) epitope. While supporting viral control in the LCMV model, oligoclonality and more private of TCR repertoires may impact future pathogenic challenges and may promote viral escape. Our results may explain the ongoing problems of viral escapes, unpredictable autoimmunity, and heterogeneous responses appearing as adverse effects of checkpoint inhibitor treatments.

Dead Cells Induce Innate Anergy via Mertk after Acute Viral Infection.

Infections can result in a temporarily restricted unresponsiveness of the innate immune response, thereby limiting pathogen control. Mechanisms of such unresponsiveness are well studied in lipopolysaccharide tolerance; however, whether mechanisms of tolerance limit innate immunity during virus infection remains unknown. Here, we find that infection with the highly cytopathic vesicular stomatitis virus (VSV) leads to innate anergy for several days. Innate anergy is associated with induction of apoptotic cells, which activates the Tyro3, Axl, and Mertk (TAM) receptor Mertk and induces high levels of interleukin-10 (IL-10) and transforming growth factor ß (TGF-ß). Lack of Mertk in Mertk-/- mice prevents induction of IL-10 and TGF-ß, resulting in abrogation of innate anergy. Innate anergy is associated with enhanced VSV replication and poor survival after infection. Mechanistically, Mertk signaling upregulates suppressor of cytokine signaling 1 (SOCS1) and SOCS3. Dexamethasone treatment upregulates Mertk and enhances innate anergy in a Mertk-dependent manner. In conclusion, we identify Mertk as one major regulator of innate tolerance during infection with VSV.

Anti-TNF treatment negatively regulates human CD4+ T-cell activation and maturation in vitro, but does not confer an anergic or suppressive phenotype.

TNF-blockade has shown clear therapeutic value in rheumatoid arthritis and other immune-mediated inflammatory diseases, however its mechanism of action is not fully elucidated. We investigated the effects of TNF-blockade on CD4+ T cell activation, maturation, and proliferation, and assessed whether TNF-inhibitors confer regulatory potential to CD4+ T cells. CyTOF and flow cytometry analysis revealed that in vitro treatment of human CD4+ T cells with the anti-TNF monoclonal antibody adalimumab promoted IL-10 expression in CD4+ T cells, whilst decreasing cellular activation. In line with this, analysis of gene expression profiling datasets of anti-TNF-treated IL-17 or IFN-γ-producing CD4+ T cells revealed changes in multiple pathways associated with cell cycle and proliferation. Kinetics experiments showed that anti-TNF treatment led to delayed, rather than impaired T-cell activation and maturation. Whilst anti-TNF-treated CD4+ T cells displayed some hyporesponsiveness upon restimulation, they did not acquire enhanced capacity to suppress T-cell responses or modulate monocyte phenotype. These cells however displayed a reduced ability to induce IL-6 and IL-8 production by synovial fibroblasts. Together, these data indicate that anti-TNF treatment delays human CD4+ T-cell activation, maturation, and proliferation, and this reduced activation state may impair their ability to activate stromal cells.

Non-response to rituximab therapy in rheumatoid arthritis is associated with incomplete disruption of the B cell receptor repertoire.

OBJECTIVE: To gain more insight into the dynamics of lymphocyte depletion and develop new predictors of clinical response to rituximab in rheumatoid arthritis (RA). METHODS: RNA-based next-generation sequencing was used to analyse the B cell receptor (BCR) repertoire in peripheral blood and synovial tissue samples collected from 24 seropositive patients with RA treated with rituximab. Clonal expansion, mutation load and clonal overlap were assessed in samples collected before, at week 4 and at week 16 or 24 after treatment and correlated to the patients' clinical response. RESULTS: After 4 weeks of rituximab-induced B cell depletion, the peripheral blood BCR repertoire of treated patients consisted of fewer, more dominant and more mutated BCR clones. No significant changes in the synovial tissue BCR repertoire were detected until week 16 post-treatment, when a reduced clonal overlap with baseline and an increased mutation load were observed. In patients who were non-responders at month 3 (n=5) using the European League Against Rheumatism response criteria, peripheral blood samples taken at week 4 after rituximab treatment showed more dominant clones compared with moderate responders (n=9) (median (IQR): 36 (27-52) vs 18 (16-26); p<0.01) and more clonal overlap with the baseline (median (IQR): 5% (2%-20%) vs 0% (0%-0%); p≤0.01). CONCLUSION: Significant changes in BCR clonality are observed in peripheral blood of patients 4 weeks after rituximab treatment, while changes in synovial tissue were observed at later time points. Incomplete depletion of the dominant baseline peripheral blood BCR repertoire in the first month of treatment might predict clinical non-response at 3 months.

[Hepatic and digestive adverse events of immune checkpoint inhibitors (anti-CTLA-4 and, anti-PD-1/PD-L1): A clinico-pathological review]. / Effets secondaires digestifs et hépatiques des inhibiteurs du checkpoint immunitaire (Immune checkpoint inhibitors : anti-CTLA-4 et anti-PD-1/PD-L1) : aspects anatomocliniques.

Immune checkpoint inhibitors (anti-CTLA-4 and anti-PD-1/PD-L1) have recently revolutionized anti-cancer therapy and are nowadays used in different metastatic cancers. These treatments may induce immune-related adverse events which frequently involve the digestive tract and, to a less extent the liver. The tissular injuries, which are still poorly characterized from a morphological and physiopathological point of view, may lead on one side to the interruption of a life-saving treatment and on the other side to the development of severe complications, if not death. Therefore, it is crucial to diagnose as early as possible and treat these digestive and hepatic adverse effects in an optimal way. This article aims to describe the clinical and pathological presentations of digestive and hepatic adverse events induced by these immunotherapies.

Soluble antigen arrays disarm antigen-specific B cells to promote lasting immune tolerance in experimental autoimmune encephalomyelitis.

Autoreactive lymphocytes that escape central immune tolerance may be silenced via an endogenous peripheral tolerance mechanism known as anergy. Antigen-specific therapies capable of inducing anergy may restore patients with autoimmune diseases to a healthy phenotype while avoiding deleterious side effects associated with global immunosuppression. Inducing anergy in B cells may be a particularly potent intervention, as B cells can contribute to autoimmune diseases through multiple mechanisms and offer the potential for direct antigen-specific targeting through the B cell receptor (BCR). Our previous results suggested autoreactive B cells may be silenced by multivalent 'soluble antigen arrays' (SAgAs), which are polymer conjugates displaying multiple copies of autoantigen with or without a secondary peptide that blocks intracellular cell-adhesion molecule-1 (ICAM-1). Here, key therapeutic molecular properties of SAgAs were identified and linked to the immunological mechanism through comprehensive cellular and in vivo analyses. We determined non-hydrolyzable 'cSAgAs' displaying multivalent 'click'-conjugated antigen more potently suppressed experimental autoimmune encephalomyelitis (EAE) compared to hydrolyzable SAgAs capable of releasing conjugated antigen. cSAgAs restored a healthy phenotype in disease-specific antigen presenting cells (APCs) by inducing an anergic response in B cells and a subset of B cells called autoimmune-associated B cells (ABCs) that act as potent APCs in autoimmune disease. Accompanied by a cytokine response skewed towards a Th2/regulatory phenotype, this generated an environment of autoantigenic tolerance. By identifying key therapeutic molecular properties and an immunological mechanism that drives SAgA efficacy, this work guides the design of antigen-specific immunotherapies capable of inducing anergy.

Current concepts on immunopathogenesis of hepatitis B virus infection.

Hepatitis B virus (HBV) infection is a leading cause of liver damage and hepatic inflammation. Upon infection, effective antiviral responses by CD8+ T cells, CD4+ T cells, Natural killer (NK) cells, and monocytes can lead to partial or complete eradication of the viral infection. To date, many studies have shown that the production of inhibitory cytokines such as Interleukin 10 (IL-10), Transforming growth factor beta (TGF-ß), along with dysfunction of the dendritic cells (DCs), and the absence of efficient innate immune responses could lead to T cell exhaustion, development of persistent infection, and inability to eradicate the viral infection from liver. Understanding the immunopathogenesis of the virus could be useful in providing further insights toward novel strategies in the eradication of HBV infection.

MAIT cells launch a rapid, robust and distinct hyperinflammatory response to bacterial superantigens and quickly acquire an anergic phenotype that impedes their cognate antimicrobial function: Defining a novel mechanism of superantigen-induced immunopathology and immunosuppression.

Superantigens (SAgs) are potent exotoxins secreted by Staphylococcus aureus and Streptococcus pyogenes. They target a large fraction of T cell pools to set in motion a "cytokine storm" with severe and sometimes life-threatening consequences typically encountered in toxic shock syndrome (TSS). Given the rapidity with which TSS develops, designing timely and truly targeted therapies for this syndrome requires identification of key mediators of the cytokine storm's initial wave. Equally important, early host responses to SAgs can be accompanied or followed by a state of immunosuppression, which in turn jeopardizes the host's ability to combat and clear infections. Unlike in mouse models, the mechanisms underlying SAg-associated immunosuppression in humans are ill-defined. In this work, we have identified a population of innate-like T cells, called mucosa-associated invariant T (MAIT) cells, as the most powerful source of pro-inflammatory cytokines after exposure to SAgs. We have utilized primary human peripheral blood and hepatic mononuclear cells, mouse MAIT hybridoma lines, HLA-DR4-transgenic mice, MAIThighHLA-DR4+ bone marrow chimeras, and humanized NOD-scid IL-2Rγnull mice to demonstrate for the first time that: i) mouse and human MAIT cells are hyperresponsive to SAgs, typified by staphylococcal enterotoxin B (SEB); ii) the human MAIT cell response to SEB is rapid and far greater in magnitude than that launched by unfractionated conventional T, invariant natural killer T (iNKT) or γδ T cells, and is characterized by production of interferon (IFN)-γ, tumor necrosis factor (TNF)-α and interleukin (IL)-2, but not IL-17A; iii) high-affinity MHC class II interaction with SAgs, but not MHC-related protein 1 (MR1) participation, is required for MAIT cell activation; iv) MAIT cell responses to SEB can occur in a T cell receptor (TCR) Vß-specific manner but are largely contributed by IL-12 and IL-18; v) as MAIT cells are primed by SAgs, they also begin to develop a molecular signature consistent with exhaustion and failure to participate in antimicrobial defense. Accordingly, they upregulate lymphocyte-activation gene 3 (LAG-3), T cell immunoglobulin and mucin-3 (TIM-3), and/or programmed cell death-1 (PD-1), and acquire an anergic phenotype that interferes with their cognate function against Klebsiella pneumoniae and Escherichia coli; vi) MAIT cell hyperactivation and anergy co-utilize a signaling pathway that is governed by p38 and MEK1/2. Collectively, our findings demonstrate a pathogenic, rather than protective, role for MAIT cells during infection. Furthermore, we propose a novel mechanism of SAg-associated immunosuppression in humans. MAIT cells may therefore provide an attractive therapeutic target for the management of both early and late phases of severe SAg-mediated illnesses.

Dysregulation of anergy-related factors involved in regulatory T cells defects in Systemic Lupus Erythematosus patients: Rapamycin and Vitamin D efficacy in restoring regulatory T cells.

AIM: Systemic Lupus Erythematosus (SLE) patients display dysfunctions in T cell activation and anergy. Therefore the aims of our study were to explore the expression of anergy-related factors in CD4+ T cells in relationship with regulatory T cells (Tregs) frequency in SLE patients and to identify strategies to redress these defects. METHOD: Casitas B-cell lymphoma b (Cbl-b) and 'gene related to anergy in lymphocytes' (GRAIL) proteins were analyzed in peripheral blood mononuclear cells (PBMCs) from SLE patients and healthy donors (HD) by immunoblotting. cbl-b, grail, growth response factors (egr)2 and egr3 messenger RNAs (mRNAs) were evaluated by real-time polymerase chain reaction in SLE and HD PBMCs and CD4+ T cells. Phenotypic and functional characterization of CD4+ T cells was performed by flow cytometry. Tregs expansion protocol consisted in culturing CD4+ T cells for 14 or 21 days of experimental activation with anti-CD3 and anti-CD28 monoclonal antibodies, human recombinant interleukin (hrIL)-2, in the absence or presence of rapamycin (Rapa) or 1,25-(OH)2D3 (vitamin D: VitD). RESULTS: SLE PBMCs expressed low levels of Cbl-b and GRAIL proteins. Both SLE PBMCs and CD4+ T cells expressed low levels of egr2/3 mRNAs. SLE patients had a reduced number of Tregs with impaired suppressive activity. An association between egr2 mRNA level in CD4+ T cells and Tregs percentage was identified. Experimental activation of CD4+ T cells in the presence of hrIL-2 and Rapa or VitD induced the expansion of SLE Tregs. However, on long-term, only Rapa exposure of SLE CD4+ T cells yielded high numbers of Tregs with sustained suppressive activity. CONCLUSION: Our results suggest a new strategy to correct defects in CD4+ T cell tolerance mechanisms that may prove beneficial in SLE.

The transcription factor NFAT promotes exhaustion of activated CD8⁺ T cells.

During persistent antigen stimulation, CD8(+) T cells show a gradual decrease in effector function, referred to as exhaustion, which impairs responses in the setting of tumors and infections. Here we demonstrate that the transcription factor NFAT controls the program of T cell exhaustion. When expressed in cells, an engineered form of NFAT1 unable to interact with AP-1 transcription factors diminished T cell receptor (TCR) signaling, increased the expression of inhibitory cell surface receptors, and interfered with the ability of CD8(+) T cells to protect against Listeria infection and attenuate tumor growth in vivo. We defined the genomic regions occupied by endogenous and engineered NFAT1 in primary CD8(+) T cells and showed that genes directly induced by the engineered NFAT1 overlapped with genes expressed in exhausted CD8(+) T cells in vivo. Our data show that NFAT promotes T cell anergy and exhaustion by binding at sites that do not require cooperation with AP-1.

Sequential transcriptional changes dictate safe and effective antigen-specific immunotherapy.

Antigen-specific immunotherapy combats autoimmunity or allergy by reinstating immunological tolerance to target antigens without compromising immune function. Optimization of dosing strategy is critical for effective modulation of pathogenic CD4(+) T-cell activity. Here we report that dose escalation is imperative for safe, subcutaneous delivery of the high self-antigen doses required for effective tolerance induction and elicits anergic, interleukin (IL)-10-secreting regulatory CD4(+) T cells. Analysis of the CD4(+) T-cell transcriptome, at consecutive stages of escalating dose immunotherapy, reveals progressive suppression of transcripts positively regulating inflammatory effector function and repression of cell cycle pathways. We identify transcription factors, c-Maf and NFIL3, and negative co-stimulatory molecules, LAG-3, TIGIT, PD-1 and TIM-3, which characterize this regulatory CD4(+) T-cell population and whose expression correlates with the immunoregulatory cytokine IL-10. These results provide a rationale for dose escalation in T-cell-directed immunotherapy and reveal novel immunological and transcriptional signatures as surrogate markers of successful immunotherapy.

Dendritic cells and anergic type I NKT cells play a crucial role in sulfatide-mediated immune regulation in experimental autoimmune encephalomyelitis.

CD1d-restricted NKT cells can be divided into two groups: type I NKT cells use a semi-invariant TCR, whereas type II express a relatively diverse set of TCRs. A major subset of type II NKT cells recognizes myelin-derived sulfatides and is selectively enriched in the CNS tissue during experimental autoimmune encephalomyelitis (EAE). We have shown that activation of sulfatide-reactive type II NKT cells by sulfatide prevents induction of EAE. In this article, we have addressed the mechanism of regulation, as well as whether a single immunodominant form of synthetic sulfatide can treat ongoing chronic and relapsing EAE in SJL/J mice. We have shown that the activation of sulfatide-reactive type II NKT cells leads to a significant reduction in the frequency and effector function of myelin proteolipid proteins 139-151/I-A(s)-tetramer(+) cells in lymphoid and CNS tissues. In addition, type I NKT cells and dendritic cells (DCs) in the periphery, as well as CNS-resident microglia, are inactivated after sulfatide administration, and mice deficient in type I NKT cells are not protected from disease. Moreover, tolerized DCs from sulfatide-treated animals can adoptively transfer protection into naive mice. Treatment of SJL/J mice with a synthetic cis-tetracosenoyl sulfatide, but not α-galactosylceramide, reverses ongoing chronic and relapsing EAE. Our data highlight a novel immune-regulatory pathway involving NKT subset interactions leading to inactivation of type I NKT cells, DCs, and microglial cells in suppression of autoimmunity. Because CD1 molecules are nonpolymorphic, the sulfatide-mediated immune-regulatory pathway can be targeted for development of non-HLA-dependent therapeutic approaches to T cell-mediated autoimmune diseases.

Novel CD3-specific antibody induces immunosuppression via impaired phosphorylation of LAT and PLCγ1 following T-cell stimulation.

The activation of T cells is known to be accompanied by the temporary downmodulation of the TCR/CD3 complex on the cell surface. Here, we established a novel monoclonal antibody, Dow2, that temporarily induces downmodulation of the TCR/CD3 complex in mouse CD4(+) T cells without activating T cells. Dow2 recognized the determinant on CD3ε; however, differences were observed in the binding mode between Dow2 and the agonistic anti-CD3ε Ab, 145-2C11. An injection of Dow2 in vivo resulted in T-cell anergy, and prolonged the survival of cardiac allografts without a marked increase in cytokine release. The phosphorylated forms of the signaling proteins PLC-γ1 and LAT in Dow2-induced anergic T cells were markedly decreased upon stimulation. However, the levels of phosphorylated LAT and PLCγ1 in Dow2-induced anergic T cells could be rescued in the presence of the proteasome inhibitor MG-132. These results suggest that proteasome-mediated degradation is involved in hypophosphorylated LAT and PLCγ1 in Dow2-induced anergic T cells. The novel CD3-specific Ab, Dow2, may provide us with a unique tool for inducing immunosuppression.

Antigen-dependent integration of opposing proximal TCR-signaling cascades determines the functional fate of T lymphocytes.

T cell anergy is a key tolerance mechanism to mitigate unwanted T cell activation against self by rendering lymphocytes functionally inactive following Ag encounter. Ag plays an important role in anergy induction where high supraoptimal doses lead to the unresponsive phenotype. How T cells "measure" Ag dose and how this determines functional output to a given antigenic dose remain unclear. Using multiparametric phospho-flow and mass cytometry, we measured the intracellular phosphorylation-dependent signaling events at a single-cell resolution and studied the phosphorylation levels of key proximal human TCR activation- and inhibition-signaling molecules. We show that the intracellular balance and signal integration between these opposing signaling cascades serve as the molecular switch gauging Ag dose. An Ag density of 100 peptide-MHC complexes/cell was found to be the transition point between dominant activation and inhibition cascades, whereas higher Ag doses induced an anergic functional state. Finally, the neutralization of key inhibitory molecules reversed T cell unresponsiveness and enabled maximal T cell functions, even in the presence of very high Ag doses. This mechanism permits T cells to make integrated "measurements" of Ag dose that determine subsequent functional outcomes.

Intravenous immunoglobulin induces a functional silencing program similar to anergy in human B cells.

BACKGROUND: Chronic inflammatory and autoimmune diseases are largely due to inappropriate response of hyperactive or autoreactive B cells. These autoreactive B cells can evade central tolerance checkpoints and migrate to the periphery, where they would be silenced by anergy. Such anergic cells are characterized by B-cell receptor (BCR) desensitization and altered downstream signaling. OBJECTIVE: We sought to determine whether intravenous immunoglobulin (IVIg) induces a nonresponsive state of B cells and to address the similarities of this mechanism to those described in anergy. METHODS: Human B cells were stimulated with anti-IgM antibody, and effects of IVIg on several parameters, such as calcium release, tyrosine phosphorylation, BCR aggregation, BCR internalization, or transcriptional activity, were studied by using flow cytometry, confocal microscopy, Western blotting, and a quantitative PCR array. RESULTS: IVIg-treated B cells show defects in activating coreceptor expression, calcium signaling, and BCR aggregation on engagement by antigen. IVIg also induces suppression of phosphoinositide 3-kinase signaling, which plays a central role in determining B-cell fate. All these events ultimately lead to profound modifications in gene expression, resulting in long-term functional but reversible silencing of IVIg-treated B cells. CONCLUSION: Our findings provide insights into the effectiveness of IVIg in treating autoimmune or inflammatory pathologies associated with the loss of B-cell tolerance. Furthermore, these data provide a model to explore the complexity of positive versus negative selection in B cells.

Programmed death 1-mediated T cell exhaustion during visceral leishmaniasis impairs phagocyte function.

Control of Leishmania infantum infection is dependent upon Th1 CD4(+) T cells to promote macrophage intracellular clearance of parasites. Deficient CD4(+) T cell effector responses during clinical visceral leishmaniasis (VL) are associated with elevated production of IL-10. In the primary domestic reservoir of VL, dogs, we define occurrence of both CD4(+) and CD8(+) T cell exhaustion as a significant stepwise loss of Ag-specific proliferation and IFN-γ production, corresponding to increasing VL symptoms. Exhaustion was associated with a 4-fold increase in the population of T cells with surface expression of programmed death 1 (PD-1) between control and symptomatic populations. Importantly, exhausted populations of CD8(+) T cells and to a lesser extent CD4(+) T cells were present prior to onset of clinical VL. VL-exhausted T cells did not undergo significant apoptosis ex vivo after Ag stimulation. Ab block of PD-1 ligand, B7.H1, promoted return of CD4(+) and CD8(+) T cell function and dramatically increased reactive oxygen species production in cocultured monocyte-derived phagocytes. As a result, these phagocytes had decreased parasite load. To our knowledge, we demonstrate for the first time that pan-T cell, PD-1-mediated, exhaustion during VL influenced macrophage-reactive oxygen intermediate production. Blockade of the PD-1 pathway improved the ability of phagocytes isolated from dogs presenting with clinical VL to clear intracellular parasites. T cell exhaustion during symptomatic canine leishmaniasis has implications for the response to vaccination and therapeutic strategies for control of Leishmania infantum in this important reservoir species.

ß-mannosylceramide activates type I natural killer t cells to induce tumor immunity without inducing long-term functional anergy.

PURPOSE: Most studies characterizing antitumor properties of invariant natural killer T (iNKT) cells have used the agonist, α-galactosylceramide (α-GalCer). However, α-GalCer induces strong, long-lasting anergy of iNKT cells, which could be a major detriment for clinical therapy. A novel iNKT cell agonist, ß-mannosylceramide (ß-ManCer), induces strong antitumor immunity through a mechanism distinct from that of α-GalCer. The objective of this study was to determine whether ß-ManCer induces anergy of iNKT cells. EXPERIMENTAL DESIGN: Induction of anergy was determined by ex vivo analysis of splenocytes from mice pretreated with iNKT cell agonists as well as in the CT26 lung metastasis in vivo tumor model. RESULTS: ß-ManCer activated iNKT cells without inducing long-term anergy. The transience of anergy induction correlated with a shortened duration of PD-1 upregulation on iNKT cells activated with ß-ManCer, compared with α-GalCer. Moreover, whereas mice pretreated with α-GalCer were unable to respond to a second glycolipid stimulation to induce tumor protection for up to 2 months, mice pretreated with ß-ManCer were protected from tumors by a second stimulation equivalently to vehicle-treated mice. CONCLUSIONS: The lack of long-term functional anergy induced by ß-ManCer, which allows for a second dose to still give therapeutic benefit, suggests the strong potential for this iNKT cell agonist to succeed in settings where α-GalCer has failed.

In vivo interferon-alpha/ribavirin treatment modulates Vγ9Vδ2 T-cell function during chronic HCV infection.

In chronic hepatitis C virus (HCV) infection, treatment failure and defective host immune response highly demand improved therapy strategies. Vγ9Vδ2 T-cells represent a good target for HCV immunotherapy, since phosphoantigen (PhAg)-activated Vγ9Vδ2 T-lymphocytes are able to inhibit subgenomic HCV replication by interferon (IFN)-γ release. A profound impairment of IFN-γ production by Vγ9Vδ2 T-cells during chronic HCV infection was previously shown. Interestingly, in vitro IFN-α partially restored Vγ9Vδ2 T-cells responsiveness to PhAg, by stabilizing IFN-γ-mRNA. To verify how in vivo IFN-α/ribavirin (RBV) treatment could affect Vγ9Vδ2 T-cells phenotype and responsiveness to PhAg in HCV-infected patients, 10 subjects underwent a longitudinal study before and after treatment. IFN-α/RBV therapy did not significantly modify Vγ9Vδ2 T-cell numbers and differentiation profile. Interestingly, Vγ9Vδ2 T-cell responsiveness remained unmodified until 3 weeks of therapy, but dropped after 1 month, suggesting that repeated in vivo IFN-α administration in the absence of T-cell receptor (TCR)-mediated signals results in Vγ9Vδ2 T-cell anergy. The present work defines the window of possible application of combined strategies targeting Vγ9Vδ2 T-cells during chronic HCV infection; specifically, the first 3 weeks from the beginning of treatment may represent the optimal time to target Vγ9Vδ2 T-cells in vivo, since their function in terms of IFN-γ production is preserved.