B and T lymphocyte attenuator is highly expressed on CMV-specific T cells during infection and regulates their function

The role of the BTLA-HVEM complex in the pathogenesis of breast cancer

Breast cancer (BC) is widely recognized as a prevalent contributor to cancer mortality and ranks as the second most prevalent form of cancer among women across the globe. Hence, the development of innovative therapeutic strategies is imperative to effectively manage BC. The B- and T-lymphocyte attenuator (BTLA)-Herpesvirus entry mediator (HVEM) complex has garnered significant scientific interest as a crucial regulator in various immune contexts. The interaction between BTLA-HVEM ligand on the surface of T cells results in reduced cellular activation, cytokine synthesis, and proliferation. The BTLA-HVEM complex has been investigated in various cancers, yet its specific mechanisms in BC remain indeterminate. In this study, we aim to examine the function of BTLA-HVEM and provide a comprehensive overview of the existing evidence in relation to BC. The obstruction or augmentation of these pathways may potentially enhance the efficacy of BC treatment.

Mucosal-associated invariant T cells display both pathogenic and protective roles in patients with inflammatory bowel diseases

An important subtype of the innate-like T lymphocytes is mucosal-associated invariant T (MAIT) cells expressing a semi-invariant T cell receptor α (TCR-α) chain. MAIT cells could be activated mainly by TCR engagement or cytokines. They have been found to have essential roles in various immune mediated. There have been growing preclinical and clinical findings that show an association between MAIT cells and the physiopathology of inflammatory bowel diseases (IBD). Of note, published reports demonstrate contradictory findings regarding the role of MAIT cells in IBD patients. A number of reports suggests a protective effect, whereas others show a pathogenic impact. The present review article aimed to explore and discuss the findings of experimental and clinical investigations evaluating the effects of MAIT cells in IBD subjects and animal models. Findings indicate that MAIT cells could exert opposite effects in the course of IBD, including an anti-inflammatory protective effect of blood circulating MAIT cells and an effector pathogenic effect of colonic MAIT cells. Another important finding is that blood levels of MAIT cells can be considered as a potential biomarker in IBD patients.

The kinetics of inhibitory immune checkpoints during and post-COVID-19: the knowns and unknowns

The immune system is tightly regulated to prevent immune reactions to self-antigens and to avoid excessive immune responses during and after challenges from non-self-antigens. Inhibitory immune checkpoints (IICPs), as the major regulators of immune system responses, are extremely important for maintaining the homeostasis of cells and tissues. However, the high and sustained co-expression of IICPs in chronic infections, under persistent antigenic stimulations, results in reduced immune cell functioning and more severe and prolonged disease complications. Furthermore, IICPs-mediated interactions can be hijacked by pathogens in order to evade immune induction or effector mechanisms. Therefore, IICPs can be potential targets for the prognosis and treatment of chronic infectious diseases. This is especially the case with regards to the most challenging infectious disease of recent times, coronavirus disease-2019 (COVID-19), whose long-term complications can persist long after recovery. This article reviews the current knowledge about the kinetics and functioning of the IICPs during and post-COVID-19.

Beyond the anti-PD-1/PD-L1 era: promising role of the BTLA/HVEM axis as a future target for cancer immunotherapy

Recent introduction of monoclonal antibodies targeting immune checkpoints to harness antitumor immunity has revolutionized the cancer treatment landscape. The therapeutic success of immune checkpoint blockade (ICB)-based therapies mainly relies on PD-1/PD-L1 and CTLA-4 blockade. However, the limited overall responses and lack of reliable predictive biomarkers of patient´s response are major pitfalls limiting immunotherapy success. Hence, this reflects the compelling need of unveiling novel targets for immunotherapy that allow to expand the spectrum of ICB-based strategies to achieve optimal therapeutic efficacy and benefit for cancer patients. This review thoroughly dissects current molecular and functional knowledge of BTLA/HVEM axis and the future perspectives to become a target for cancer immunotherapy. BTLA/HVEM dysregulation is commonly found and linked to poor prognosis in solid and hematological malignancies. Moreover, circulating BTLA has been revealed as a blood-based predictive biomarker of immunotherapy response in various cancers. On this basis, BTLA/HVEM axis emerges as a novel promising target for cancer immunotherapy. This prompted rapid development and clinical testing of the anti-BTLA blocking antibody Tifcemalimab/icatolimab as the first BTLA-targeted therapy in various ongoing phase I clinical trials with encouraging results on preliminary efficacy and safety profile as monotherapy and combined with other anti-PD-1/PD-L1 therapies. Nevertheless, it is anticipated that the intricate signaling network constituted by BTLA/HVEM/CD160/LIGHT involved in immune response regulation, tumor development and tumor microenvironment could limit therapeutic success. Therefore, in-depth functional characterization in different cancer settings is highly recommended for adequate design and implementation of BTLA-targeted therapies to guarantee the best clinical outcomes to benefit cancer patients.

The Features of Checkpoint Receptor—Ligand Interaction in Cancer and the Therapeutic Effectiveness of Their Inhibition

To date, certain problems have been identified in cancer immunotherapy using the inhibition of immune checkpoints (ICs). Despite the excellent effect of cancer therapy in some cases when blocking the PD-L1 (programmed death-ligand 1) ligand and the immune cell receptors PD-1 (programmed cell death protein 1) and CTLA4 (cytotoxic T-lymphocyte-associated protein 4) with antibodies, the proportion of patients responding to such therapy is still far from desirable. This situation has stimulated the exploration of additional receptors and ligands as targets for immunotherapy. In our article, based on the analysis of the available data, the TIM-3 (T-cell immunoglobulin and mucin domain-3), LAG-3 (lymphocyte-activation gene 3), TIGIT (T-cell immunoreceptor with Ig and immunoreceptor tyrosine-based inhibitory motif (ITIM) domains), VISTA (V-domain Ig suppressor of T-cell activation), and BTLA (B- and T-lymphocyte attenuator) receptors and their ligands are comprehensively considered. Data on the relationship between receptor expression and the clinical characteristics of tumors are presented and are analyzed together with the results of preclinical and clinical studies on the therapeutic efficacy of their blocking. Such a comprehensive analysis makes it possible to assess the prospects of receptors of this series as targets for anticancer therapy. The expression of the LAG-3 receptor shows the most unambiguous relationship with the clinical characteristics of cancer. Its inhibition is the most effective of the analyzed series in terms of the antitumor response. The expression of TIGIT and BTLA correlates well with clinical characteristics and demonstrates antitumor efficacy in preclinical and clinical studies, which indicates their high promise as targets for anticancer therapy. At the same time, the relationship of VISTA and TIM-3 expression with the clinical characteristics of the tumor is contradictory, and the results on the antitumor effectiveness of their inhibition are inconsistent.

BTLA inhibition has a dominant role in the cis-complex of BTLA and HVEM

The engagement of the herpesvirus entry mediator (HVEM, TNFRSF14) by the B and T lymphocyte attenuator (BTLA) represents a unique interaction between an activating receptor of the TNFR-superfamily and an inhibitory receptor of the Ig-superfamily. BTLA and HVEM have both been implicated in the regulation of human T cell responses, but their role is complex and incompletely understood. Here, we have used T cell reporter systems to dissect the complex interplay of HVEM with BTLA and its additional ligands LIGHT and CD160. Co-expression with LIGHT or CD160, but not with BTLA, induced strong constitutive signaling via HVEM. In line with earlier reports, we observed that in cis interaction of BTLA and HVEM prevented HVEM co-stimulation by ligands on surrounding cells. Intriguingly, our data indicate that BTLA mediated inhibition is not impaired in this heterodimeric complex, suggesting a dominant role of BTLA co-inhibition. Stimulation of primary human T cells in presence of HVEM ligands indicated a weak costimulatory capacity of HVEM potentially owed to its in cis engagement by BTLA. Furthermore, experiments with T cell reporter cells and primary T cells demonstrate that HVEM antibodies can augment T cell responses by concomitantly acting as checkpoint inhibitors and co-stimulation agonists.

Immune Regulatory Processes of the Tumor Microenvironment under Malignant Conditions

The tumor microenvironment (TME) is a critical regulator of tumor growth, progression, and metastasis. Since immune cells represent a large fraction of the TME, they play a key role in mediating pro- and anti-tumor immune responses. Immune escape, which suppresses anti-tumor immunity, enables tumor cells to maintain their proliferation and growth. Numerous mechanisms, which have been intensively studied in recent years, are involved in this process and based on these findings, novel immunotherapies have been successfully developed. Here, we review the composition of the TME and the mechanisms by which immune evasive processes are regulated. In detail, we describe membrane-bound and soluble factors, their regulation, and their impact on immune cell activation in the TME. Furthermore, we give an overview of the tumor/antigen presentation and how it is influenced under malignant conditions. Finally, we summarize novel TME-targeting agents, which are already in clinical trials for different tumor entities.

BTLA-HVEM Couple in Health and Diseases: Insights for Immunotherapy in Lung Cancer

Lung cancer is the leading cause of cancer deaths worldwide. Immunotherapies (IT) have been rapidly approved for lung cancer treatment after the spectacular results in melanoma. Responses to the currently used checkpoint inhibitors are strikingly good especially in metastatic diseases. However, durable responses are observed in only 25% of cases. Consequently, there is an urgent need for new immunotherapy targets. Among the multiple checkpoints involved in the tumor immune escape, the BTLA-HVEM couple appears to be a promising target. BTLA (B- and T- Lymphocyte Attenuator) is a co-inhibitory receptor mainly expressed by B and T cells, repressing the activation signal transduction. BTLA shares similarities with other immune checkpoints such as PD-1 and CTLA-4 which are the targets of the currently used immunotherapies. Furthermore, BTLA expression points out terminally exhausted and dysfunctional lymphocytes, and correlates with lung cancer progression. The ligand of BTLA is HVEM (Herpes Virus Entry Mediator) which belongs to the TNF receptor family. Often described as a molecular switch, HVEM is constitutively expressed by many cells, including cells from tumor and healthy tissues. In addition, HVEM seems to be involved in tumor immuno-evasion, especially in lung tumors lacking PD-L1 expression. Here, we propose to review the role of BTLA-HVEM in immuno-escape in order to highlight its potential for designing new immunotherapies.

Interpretable systems biomarkers predict response to immune-checkpoint inhibitors

Cancer cells can leverage several cell-intrinsic and -extrinsic mechanisms to escape immune system recognition. The inherent complexity of the tumor microenvironment, with its multicellular and dynamic nature, poses great challenges for the extraction of biomarkers of immune response and immunotherapy efficacy. Here, we use RNA-sequencing (RNA-seq) data combined with different sources of prior knowledge to derive system-based signatures of the tumor microenvironment, quantifying immune-cell composition and intra- and intercellular communications. We applied multi-task learning to these signatures to predict different hallmarks of immune responses and derive cancer-type-specific models based on interpretable systems biomarkers. By applying our models to independent RNA-seq data from cancer patients treated with PD-1/PD-L1 inhibitors, we demonstrated that our method to Estimate Systems Immune Response (EaSIeR) accurately predicts therapeutic outcome. We anticipate that EaSIeR will be a valuable tool to provide a holistic description of immune responses in complex and dynamic systems such as tumors using available RNA-seq data.

PD-1/PD-L1 Axis as a Potential Therapeutic Target for Multiple Sclerosis: A T Cell Perspective

The programmed cell death protein-1/programmed death ligand-1 (PD-1/PD-L1) axis is a widely studied immune checkpoint that modulates signaling pathways related to T cell activation. The use of PD-1/PD-L1 inhibitors is a promising immune therapy strategy for cancer patients. However, individuals treated with PD-1/PD-L1 inhibitors may develop immune-related adverse events due to excessive immune reactions. Multiple sclerosis (MS) is a chronic demyelinating and neurodegenerative disease of the central nervous system. T cells and the PD-1/PD-L1 axis play vital roles in the pathogenesis of MS. A better understanding of the complex relationship between the PD-1/PD-L1 axis and T cells may extend our knowledge of the molecular mechanisms and therapeutic approaches for MS. In this review, we summarize the most recent findings regarding the role of the PD-1/PD-L1 axis in MS and discuss the potential therapeutic strategies to modulate the expression of PD-1/PD-L1 in MS.

The Role of B and T Lymphocyte Attenuator in Respiratory System Diseases

B and T lymphocyte attenuator (BTLA), an immunomodulatory molecule widely expressed on the surface of immune cells, can influence various signaling pathways and negatively regulate the activation and proliferation of immune cells by binding to its ligand herpes virus entry mediator (HVEM). BTLA plays an important role in immunoregulation and is involved in the pathogenesis of various respiratory diseases, including airway inflammation, asthma, infection, pneumonia, acute respiratory distress syndrome and lung cancer. In recent years, some studies have found that BTLA also has played a positive regulatory effect on immunity system in the occurrence and development of respiratory diseases. Since severe pulmonary infection is a risk factor for sepsis, this review also summarized the new findings on the role of BTLA in sepsis.

Roles of BTLA in Immunity and Immune Disorders

B and T lymphocyte attenuator (BTLA) is one of the most important cosignaling molecules. It belongs to the CD28 superfamily and is similar to programmed cell death-1 (PD-1) and cytotoxic T lymphocyte associated antigen-4 (CTLA-4) in terms of its structure and function. BTLA can be detected in most lymphocytes and induces immunosuppression by inhibiting B and T cell activation and proliferation. The BTLA ligand, herpesvirus entry mediator (HVEM), does not belong to the classic B7 family. Instead, it is a member of the tumor necrosis factor receptor (TNFR) superfamily. The association of BTLA with HVEM directly bridges the CD28 and TNFR families and mediates broad and powerful immune effects. Recently, a large number of studies have found that BTLA participates in numerous physiopathological processes, such as tumor, inflammatory diseases, autoimmune diseases, infectious diseases, and transplantation rejection. Therefore, the present work aimed to review the existing knowledge about BTLA in immunity and summarize the diverse functions of BTLA in various immune disorders.

Expression pattern of co-inhibitory molecules on CMV-specific T-cells in lung transplant patients

OBJECTIVES

Cytomegalovirus infection (CMVi) occurs frequently in transplant patients. Co-inhibitory molecules on CMV-specific T-cells (TCMV) in patients after lung transplantation were investigated.

METHODS

59 lung transplant patients were stratified according to anti-CMV serostatus at time of transplantation. The co-inhibitors Programmed-Death-Receptor-1 (PD1) and B-and-T-Lymphocyte-Attenuator (BTLA) were detected on TCMV by flow cytometry (FACS).

RESULTS

TCMV were detectable in CMV sero-positive patients (R+) and in CMV sero-negative patients with a lung graft of a CMV sero-positive donor (D+/R-); in both cases, the frequency of TCMV was higher than in healthy controls (HC). PD-1 on TCMV was increased in D+/R+ and D+/R- patients as compared to HC. BTLA was significantly enhanced on TCMV of D+/R- patients vs. HC. R+ patients with CMV reactivation in the past had an increased fraction of BTLA+ TCMV.

CONCLUSION

In conclusion, the expression pattern of co-inhibitory molecules on TCMV is altered in patients after lung transplantation.

BTLA/HVEM Signaling: Milestones in Research and Role in Chronic Hepatitis B Virus Infection

B- and T-lymphocyte attenuator (BTLA) is an immune-regulatory receptor, similar to CTLA-4 and PD-1, and is mainly expressed on B-, T-, and all mature lymphocyte cells. Herpes virus entry mediator (HVEM)-BTLA plays a critical role in immune tolerance and immune responses which are areas of intense research. However, the mechanisms of the BTLA and the BTLA/HVEM signaling pathway in human diseases remain unclear. This review describes the research milestones of BTLA and HVEM in chronological order and their role in chronic HBV infection.

Not All Immune Checkpoints Are Created Equal

Antibodies that block T cell inhibition via the immune checkpoints CTLA-4 and PD-1 have revolutionized cancer therapy during the last 15 years. T cells express additional inhibitory surface receptors that are considered to have potential as targets in cancer immunotherapy. Antibodies against LAG-3 and TIM-3 are currently clinically tested to evaluate their effectiveness in patients suffering from advanced solid tumors or hematologic malignancies. In addition, blockade of the inhibitory BTLA receptors on human T cells may have potential to unleash T cells to effectively combat cancer cells. Much research on these immune checkpoints has focused on mouse models. The analysis of animals that lack individual inhibitory receptors has shed some light on the role of these molecules in regulating T cells, but also immune responses in general. There are current intensive efforts to gauge the efficacy of antibodies targeting these molecules called immune checkpoint inhibitors alone or in different combinations in preclinical models of cancer. Differences between mouse and human immunology warrant studies on human immune cells to appreciate the potential of individual pathways in enhancing T cell responses. Results from clinical studies are not only highlighting the great benefit of immune checkpoint inhibitors for treating cancer but also yield precious information on their role in regulating T cells and other cells of the immune system. However, despite the clinical relevance of CTLA-4 and PD-1 and the high potential of the emerging immune checkpoints, there are still substantial gaps in our understanding of the biology of these molecules, which might prevent the full realization of their therapeutic potential. This review addresses PD-1, CTLA-4, BTLA, LAG-3, and TIM-3, which are considered major inhibitory immune checkpoints expressed on T cells. It provides summaries of our current conception of the role of these molecules in regulating T cell responses, and discussions about major ambiguities and gaps in our knowledge. We emphasize that each of these molecules harbors unique properties that set it apart from the others. Their distinct functional profiles should be taken into account in therapeutic strategies that aim to exploit these pathways to enhance immune responses to combat cancer.

Defective BTLA functionality is rescued by restoring lipid metabolism in lupus CD4+ T cells

Coinhibitory receptors play an important role in the prevention of autoimmune diseases, such as systemic lupus erythematosus (SLE), by limiting T cell activation. B and T lymphocyte attenuator (BTLA) is an inhibitory receptor, similar to cytotoxic T lymphocyte-associated protein 4 (CTLA-4) and programmed death 1 (PD1), that negatively regulates the immune response. The role of BTLA in the pathogenesis of autoimmune diseases in humans and, more specifically, in SLE is largely unknown. We investigated BTLA expression on various T cell subsets, and we did not observe significant variations of BTLA expression between lupus patients and healthy controls. However, the enhancement of BTLA expression after activation was significantly lower in SLE patients compared with that in healthy controls. Furthermore, we found an impaired capacity of BTLA to inhibit T cell activation in SLE due to a poor BTLA recruitment to the immunological synapse following T cell stimulation. Finally, we demonstrated that defective BTLA function can be corrected by restoring intracellular trafficking and by normalizing the lipid metabolism in lupus CD4+ T cells. Collectively, our results evidence that the BTLA signaling pathway is altered in SLE T cells and highlight the potential of targeting this pathway for the development of new therapeutic strategies in lupus.

The Biology of Aging and Cancer: Frailty, Inflammation, and Immunity

The majority of patients with common malignancies are older adults. Intrinsic complex biological changes of aging along with inflammation, immunosenescence, age-associated chronic diseases, and extrinsic environmental and psychosocial factors have significant impact on not only development and behavior of individual malignancies, but also physiologic reserve and vulnerability of older patients who suffer from them. As a result, clinical practice of geriatric oncology demands integration of careful geriatric assessment and management. This article provides an overview of basic biology of aging and its relationship with cancer. After a brief introduction about the definition and mechanisms of aging, as well as age-related biological and physiological changes, the discussion mainly focuses on recent development and insights into the relationship of frailty, inflammation, and immunity with cancer, highlighting how the new knowledge can help further improve assessment and treatment of older patients with malignancies and promote cancer research.

Antibodies targeting BTLA or TIM-3 enhance HIV-1 specific T cell responses in combination with PD-1 blockade

Persistent stimulation with antigens derived from viruses that establish chronic infections or tumour antigens results in the exhaustion of T cells. Coinhibitory receptors like PD-1 and CTLA-4 function as immune checkpoints on exhausted T cells. Blocking these molecules with antibodies improve immunity to cancer cells. Immune checkpoint inhibitors targeting other coinhibitory receptors might have a similar role in improving T cell function and thus also utility in cancer therapy. Using HIV-specific T cells as a model for exhaustion we have evaluated the capacity of antibodies targeting TIM-3, BTLA, CD160, LAG-3 and CTLA-4 alone or in combination with a PD-1 antibody to enhance proliferation and cytokine production in response to Gag and Nef peptides. Antibodies targeting BTLA and TIM-3 enhanced CD8 T cell proliferation. Moreover, our results indicate that blocking BTLA and TIM-3 in combination with PD-1 might be especially effective in enhancing responses of exhausted human T cells.

PD-1 Blockade Promotes Emerging Checkpoint Inhibitors in Enhancing T Cell Responses to Allogeneic Dendritic Cells

Immune checkpoint inhibitors, which target coinhibitory T cell molecules to promote anticancer immune responses, are on the rise to become a new pillar of cancer therapy. However, current immune checkpoint-based therapies are successful only in a subset of patients and acquired resistances pose additional challenges. Finding new targets and combining checkpoint inhibitors might help to overcome these limitations. In this study, human T cells stimulated with allogeneic dendritic cells (DCs) were used to compare immune checkpoint inhibitors targeting TIM-3, BTLA, LAG-3, CTLA-4, and TIGIT alone or in combination with a PD-1 antibody. We found that PD-1 blockade bears a unique potency to enhance T cell proliferation and cytokine production. Other checkpoint inhibitors failed to significantly augment T cell responses when used alone. However, antibodies to TIM-3, BTLA, LAG-3, and CTLA-4 enhanced T cell proliferation in presence of a PD-1 antibody. Upregulation of coinhibitory T cell receptors upon PD-1 blockade was identified as a potential mechanism for synergistic effects between checkpoint inhibitors. Donor-specific variation in response to immune checkpoint inhibitors was attributed to the T cells rather than DCs. Additionally, we analyzed the regulation of checkpoint molecules and their ligands on T cells and allogeneic DCs in coculture, which suggested a PD-1 blockade-dependent crosstalk between T cells and APC. Our results indicate that several immune checkpoint inhibitors have the capacity to enhance T cell responses when combined with PD-1 blockade. Additional in vitro studies on human T cells will be useful to identify antibody combinations with the potential to augment T cell responses in cancer patients.

CD8+ T cells of chronic HCV-infected patients express multiple negative immune checkpoints following stimulation with HCV peptides

Hepatitis C virus (HCV)-specific CD4+ and CD8+ T cells are key to successful viral clearance in HCV disease. Accumulation of exhausted HCV-specific T cells during chronic infection results in considerable loss of protective functional immune responses. The role of T-cell exhaustion in chronic HCV disease remains poorly understood. Here, we studied the frequency of HCV peptide-stimulated T cells expressing negative immune checkpoints (PD-1, CTLA-4, TRAIL, TIM-3 and BTLA) by flow cytometry, and measured the levels of Th1/Th2/Th17 cytokines secreted by T cells by a commercial Multi-Analyte ELISArray™ following in vitro stimulation of T cells using HCV peptides and phytohemagglutinin (PHA). HCV peptide-stimulated CD4+ and CD8+ T cells of chronic HCV (CHC) patients showed significant increase of CTLA-4. Furthermore, HCV peptide-stimulated CD4+ T cells of CHC patients also displayed relatively higher levels of PD-1 and TRAIL, whereas TIM-3 was up-regulated on HCV peptide-stimulated CD8+ T cells. Whereas the levels of IL-10 and TGF-β1 were significantly increased, the levels of pro-inflammatory cytokines IL-2, TNF-α, IL-17A and IL-6 were markedly decreased in the T cell cultures of CHC patients. Chronic HCV infection results in functional exhaustion of CD4+ and CD8+ T cells likely contributing to viral persistence.

Hepatic expansion of virus-specific CD8+BTLA+ T cells with regulatory properties in chronic hepatitis B virus infection

Similar to programmed death-1 (PD-1), B and T lymphocyte attenuator (BTLA) is a co-inhibitory molecule of the CD28 family. PD-1 is involved in T cell exhaustion during chronic viral infection. However, the role of BTLA in virus-specific T cells is poorly defined. Here we investigated the expression and function of BTLA in T cells from patients with chronic hepatitis B virus (HBV) infection. The phenotype of peripheral and intrahepatic HBV-specific T cells from 43 patients with chronic HBV infection was assessed by flow cytometry. Functional evaluation was analyzed by T cell expansion and cytokine secretion after different treatments. In chronic HBV patients, a subset of inefficient interferon-γ producing antigen-specific CD8⁺ T cells recruited to the liver expressed high BTLA levels. The BTLA⁺ HBV-specific CD8⁺ T cell suppressive function was antigen-specific, at least in the induction phase, because they were only activated by a pool of HBV peptides but not with a pool of unrelated peptides. Suppression of T cell responses was restored by a BTLA signaling blockade and neutralizing IL-10, indicating that BTLA signaling-mediated IL-10 secretion plays a key role in suppression. This study provides important evidence that there is a subset of liver infiltrated virus-specific CD8⁺BTLA⁺ regulatory T cells in patients with chronic HBV infection. This subset of cells plays a pivotal role in controlling hepatic effector CD8⁺ T cell responses through BTLA signaling mediated regulatory factor IL-10 production.

Effects of clostridium butyricum and bifidobacterium on BTLA expression on CD4+ T cells and lymphocyte differentiation in late preterm infants

BACKGROUND & AIMS

Probiotics is recognized to promote growth performance and immune function via balancing the intestinal microflora. Live clostridium butyricum and bifidobacterium combined powder (LCBBCP) has been widely to treat intestinal dysbacteriosis in newborns in China. This study was undertaken to investigate the effects of the combined probiotics on the expression of B and T lymphocyte attenuator (BTLA) on CD4⁺ T cells and the differentiation of lymphocyte subsets in late preterm infants.

METHODS

Eighty eligible late preterm infants were equally randomized into LCBBCP therapy group (oral LCBBCP dissolved in formula milk before intake) and control group (treated with simple formula milk for preterm infants) by random digit table. Flow cytometry was used to determine the expression level of BTLA on CD4⁺ T cells and the percentage of individual subpopulation of lymphocytes in peripheral-blood mononuclear cells (PBMCs) obtained from the late preterm infants in both groups.

RESULTS

BTLA protein expression on CD4⁺ T cells showed no significant change in LCBBCP therapy group before and after intervention, yet was rapidly and significantly down-regulated in the controls. The percentage of increased CD4⁺ T cells, decreased CD8⁺ T cells and increased ratio of CD4⁺/CD8⁺ T cell proportion were seen in both groups after treatment, yet the increasing or decreasing extent in LCBBCP therapy group was more obvious than in control group. The proportion of NK cells and B lymphocytes remained no significant difference between the two groups before and after therapy.

CONCLUSIONS

LCBBCP appears capable of facilitating the activation, proliferation and differentiation of T lymphocytes, which is beneficial to improving immunity in late preterm infants. The continuous high expression of BTLA on CD4⁺ T cells in LCBBCP therapy group may be involved in the inhibiting of excessive activation of T lymphocytes. Our findings may lay a basis for further clinical evaluation of the efficacies and wider clinical recommendation of probiotics containing live clostridium butyricum and bifidobacterium for late preterm infants.

Cytomegalovirus driven immunosenescence-An immune phenotype with or without clinical impact?

The continuous emerging increase in life span has led to vulnerability to a number of different diseases in the elderly. Some of these risks may be attributed to specific changes in the immune system referred to as immunoscenescence. This term aims to describe decreased immune functions among elderly individuals, and is characterized to be harmful age-associated changes in the immune system that lead to its gradual immune dysfunction. An impaired function of the immune system may increase susceptibility to various diseases in the elderly population such as infections, cardiovascular diseases and cancer. Although it is unclear how this immune phenotype develops, emerging evidence suggest that it may reflect an exhaustion of the immune system, possibly caused by one or several chronic infections. The main candidate is human cytomegalovirus (CMV), which can induce immune dysfunctions observed in immunoscenescence. Although the immune system is currently considered to be exhausted in CMV positive elderly individuals, it is not known whether such dysfunction of the immune system is a main reason for increased susceptibility to other diseases, or if direct effects of the virus in disease pathogenesis reflect the increased vulnerability to them. These aspects will be discussed in this review.

TNFRSF14 aberrations in follicular lymphoma increase clinically significant allogeneic T-cell responses

Donor T-cell immune responses can eradicate lymphomas after allogeneic hematopoietic stem cell transplantation (AHSCT), but can also damage healthy tissues resulting in harmful graft-versus-host disease (GVHD). Next-generation sequencing has recently identified many new genetic lesions in follicular lymphoma (FL). One such gene, tumor necrosis factor receptor superfamily 14 (TNFRSF14), abnormal in 40% of FL patients, encodes the herpes virus entry mediator (HVEM) which limits T-cell activation via ligation of the B- and T-lymphocyte attenuator. As lymphoma B cells can act as antigen-presenting cells, we hypothesized that TNFRSF14 aberrations that reduce HVEM expression could alter the capacity of FL B cells to stimulate allogeneic T-cell responses and impact the outcome of AHSCT. In an in vitro model of alloreactivity, human lymphoma B cells with TNFRSF14 aberrations had reduced HVEM expression and greater alloantigen-presenting capacity than wild-type lymphoma B cells. The increased immune-stimulatory capacity of lymphoma B cells with TNFRSF14 aberrations had clinical relevance, associating with higher incidence of acute GVHD in patients undergoing AHSCT. FL patients with TNFRSF14 aberrations may benefit from more aggressive immunosuppression to reduce harmful GVHD after transplantation. Importantly, this study is the first to demonstrate the impact of an acquired genetic lesion on the capacity of tumor cells to stimulate allogeneic T-cell immune responses which may have wider consequences for adoptive immunotherapy strategies.

Immune Checkpoint Blockade to Improve Tumor Infiltrating Lymphocytes for Adoptive Cell Therapy

Tumor-infiltrating lymphocytes (TIL) has been associated with improved survival in cancer patients. Within the tumor microenvironment, regulatory cells and expression of co-inhibitory immune checkpoint molecules can lead to the inactivation of TIL. Hence, there is a need to develop strategies that disrupt these negative regulators to achieve robust anti-tumor immune responses. We evaluated the blockade of immune checkpoints and their effect on T cell infiltration and function. We examined the ability of TIL to induce tumor-specific immune responses in vitro and in vivo. TIL isolated from tumor bearing mice were tumor-specific and expressed co-inhibitory immune checkpoint molecules. Administration of monoclonal antibodies against immune checkpoints led to a significant delay in tumor growth. However, anti-PD-L1 antibody treated mice had a significant increase in T cell infiltration and IFN-γ production compared to other groups. Adoptive transfer of in vitro expanded TIL from tumors of anti-PD-L1 antibody treated mice led to a significant delay in tumor growth. Blockade of co-inhibitory immune checkpoints could be an effective strategy to improve TIL infiltration and function.

Decreased B and T lymphocyte attenuator in Behcet's disease may trigger abnormal Th17 and Th1 immune responses

Behcet's disease (BD) is a chronic, systemic and recurrent inflammatory disease associated with hyperactive Th17 and Th1 immune responses. Recent studies have shown that B and T lymphocyte attenuator (BTLA) negatively regulates the immune response. In this study, we investigated whether BTLA activation could be exploited to inhibit the development of abnormal immune responses in BD patients. BTLA expression in PBMCs and CD4(+) T cells was significantly decreased in active BD patients. Decreased BTLA level was associated with increased Th17 and Th1 responses. Activation of BTLA inhibited the abnormal Th17 and Th1 responses and IL-22 expression in both patients and controls. Addition of an agonistic anti-BTLA antibody remarkably inhibited DC-induced Th17 and Th1 cell responses, resulted in decreased production of the Th17 and Th1-related cytokines IL-1beta, IL-6, IL-23 and IL-12p70 and reduced CD40 expression in DCs. In conclusion, decreased BTLA expression in ocular BD may lead to inappropriate control of the Th17 and Th1 immune responses and DC functions. Therefore, BTLA may be involved in the development and recurrence of this disease. Agonistic agents of BTLA may represent a potential therapeutic approach for the treatment of BD and other inflammatory diseases mediated by abnormal Th17 and Th1 immune responses.

BTLA marks a less-differentiated tumor-infiltrating lymphocyte subset in melanoma with enhanced survival properties

In a recent adoptive cell therapy (ACT) clinical trial using autologous tumor-infiltrating lymphocytes (TILs) in patients with metastatic melanoma, we found an association between CD8⁺ T cells expressing the inhibitory receptor B- and T-lymphocyte attenuator (BTLA) and clinical response. Here, we further characterized this CD8⁺BTLA⁺ TIL subset and their CD8⁺BTLA⁻ counterparts. We found that the CD8⁺ BTLA⁺ TILs had an increased response to IL-2, were less-differentiated effector-memory (T_EM) cells, and persisted longer in vivo after infusion. In contrast, CD8⁺BTLA⁻ TILs failed to proliferate and expressed genes associated with T-cell deletion/tolerance. Paradoxically, activation of BTLA signaling by its ligand, herpes virus entry mediator (HVEM), inhibited T-cell division and cytokine production, but also activated the Akt/PKB pathway thus protecting CD8⁺BTLA⁺ TILs from apoptosis. Our results point to a new role of BTLA as a useful T-cell differentiation marker in ACT and a dual signaling molecule that curtails T-cell activation while also conferring a survival advantage for CD8⁺ T cells. These attributes may explain our previous observation that BTLA expression on CD8⁺ TILs correlates with clinical response to adoptive T-cell therapy in metastatic melanoma.

Tumor necrosis factor superfamily in innate immunity and inflammation

The tumor necrosis factor superfamily (TNFSF) and its corresponding receptor superfamily (TNFRSF) form communication pathways required for developmental, homeostatic, and stimulus-responsive processes in vivo. Although this receptor-ligand system operates between many different cell types and organ systems, many of these proteins play specific roles in immune system function. The TNFSF and TNFRSF proteins lymphotoxins, LIGHT (homologous to lymphotoxins, exhibits inducible expression, and competes with HSV glycoprotein D for herpes virus entry mediator [HVEM], a receptor expressed by T lymphocytes), lymphotoxin-β receptor (LT-βR), and HVEM are used by embryonic and adult innate lymphocytes to promote the development and homeostasis of lymphoid organs. Lymphotoxin-expressing innate-acting B cells construct microenvironments in lymphoid organs that restrict pathogen spread and initiate interferon defenses. Recent results illustrate how the communication networks formed among these cytokines and the coreceptors B and T lymphocyte attenuator (BTLA) and CD160 both inhibit and activate innate lymphoid cells (ILCs), innate γδ T cells, and natural killer (NK) cells. Understanding the role of TNFSF/TNFRSF and interacting proteins in innate cells will likely reveal avenues for future therapeutics for human disease.

Multicenter validation study of anti-programmed cell death-1 antibody as a serological marker for type 1 autoimmune hepatitis

AIM

Recently, serum levels of anti-programmed cell death-1 (anti-PD-1) antibodies have been reported to be useful for the discrimination of type 1 autoimmune hepatitis (AIH) from drug-induced liver injury (DILI) and to be associated with clinical features of type 1 AIH. This multicenter study aimed to validate the usefulness of serum anti-PD-1 antibody as a serological marker for type 1 AIH.

METHODS

Serum samples before the initiation of corticosteroid treatment were obtained from 71 type 1 AIH patients and 37 DILI patients. Serum levels of anti-PD-1 antibodies were measured by indirect enzyme-linked immunosorbent assay.

RESULTS

Serum levels of anti-PD-1 antibodies were higher in type 1 AIH patients than in DILI patients (P < 0.001). The receiver-operator curve analysis showed that serum levels of anti-PD-1 antibodies were useful for the discrimination of type 1 AIH from DILI (area under the curve, 0.80). On the other hand, the multivariate Cox proportional hazard model showed that positivity for serum anti-PD-1 antibody, probable diagnosis based on the revised scoring system proposed by the International Autoimmune Hepatitis Group, and prothrombin activity of less than 60% were associated with the later normalization of serum transaminase levels. During the clinical course, the disease relapsed more frequently in patients positive for serum anti-PD-1 antibody (36% vs 11%).

CONCLUSION

This study suggests that serum anti-PD-1 antibody is useful for the diagnosis of type 1 AIH as an auxiliary diagnostic marker, and that serum levels of anti-PD-1 antibodies reflect clinical features of type 1 AIH.

Innate mucosal-associated invariant T (MAIT) cells are activated in inflammatory bowel diseases

Inflammatory bowel diseases are characterized by a deregulated immune response targeting the gut bacterial flora. Mucosal-associated invariant T (MAIT) cells are major histocompatibility complex (MHC) class Ib-restricted innate-like lymphocytes with anti-bacterial functions. They display an effector/memory phenotype and are found in large numbers in the blood, mucosae and liver. They have also been implicated in inflammatory diseases such as multiple sclerosis. Therefore, we aimed to analyse the possible involvement of MAIT cells in Crohn's disease (CD) and ulcerative colitis (UC). To this end, a phenotypical and functional analysis of MAIT cells isolated from the blood of healthy subjects, CD and UC patients was undertaken. MAIT cells were also quantified in ileal biopsies of CD patients. The frequency of blood MAIT cells was specifically reduced in IBD patients compared with healthy donors, whereas it was dramatically greater in the inflamed versus healthy tissue. MAIT cells were activated as they expressed significantly more the Ki67 antigen, and this was accompanied by phenotypical changes such as increased expression of natural killer (NK)G2D and B and T lymphocyte attenuator (BTLA). Finally, in-vitro-activated MAIT cells from CD and UC patients secreted significantly more interleukin (IL)-17, together with a decreased interferon (IFN)-γ in CD but an increased IL-22 in UC. These data show that MAIT cells are activated in IBD, which results in an increased recruitment towards the inflamed tissues, an altered phenotype and a switch in the pattern of cytokine secretion. This is the first demonstration that MAIT cells are immune players in IBD, whose precise functions in this context need to be addressed.

Anti-programmed cell death-1 antibody as a new serological marker for type 1 autoimmune hepatitis

BACKGROUND AND AIM

Recently, the association of the dysfunction of programmed cell death (PD)-1 expressed on activated lymphocytes with the pathogenesis of autoimmune hepatitis (AIH) has been speculated. This study aimed to investigate the association of serum anti-PD-1 antibodies with clinical characteristics of type 1 AIH.

METHODS

Serum samples before the initiation of prednisolone treatment were obtained from 52 type 1 AIH patients, 24 patients with drug-induced liver injury (DILI), 30 patients with acute viral hepatitis (AVH), 11 patients with primary sclerosing cholangitis (PSC), and 62 healthy volunteers. Titers of serum anti-PD-1 antibodies were measured by indirect enzyme-linked immunosorbent assay. The cutoff level was represented by a mean absorbance + 2 standard deviations in healthy volunteers.

RESULTS

Prevalence of serum anti-PD-1 antibodies was 63% in type 1 AIH patients, 8% in DILI patients, 13% in AVH patients, 18% in PSC patients, and 3% in healthy volunteers. In type 1 AIH patients, titers of serum anti-PD-1 antibodies were correlated with serum levels of bilirubin (r = 0.31, P = 0.030) and alanine aminotransferase (r = 0.31, P = 0.027) but not serum immunoglobulin G levels. Positivity for serum anti-PD-1 antibodies was associated with the later normalization of serum alanine aminotransferase levels after the initiation of prednisolone and the disease relapse.

CONCLUSIONS

Serum anti-PD-1 antibodies would be useful for the discrimination of type 1 AIH from DILI, AVH, and PSC as an auxiliary diagnostic marker. Furthermore, anti-PD-1 antibodies may be associated with clinical characteristics of type 1 AIH.

B and T lymphocyte attenuator is highly expressed on intrahepatic T cells during chronic HBV infection and regulates their function

BACKGROUND

T cell antiviral function is impaired during chronic hepatitis B (CHB). Programmed death-1 (PD-1) impairs antiviral T cell responses, but dysfunction is not always reversed by blockade of PD-1 pathway. Whether distinct T cell populations expressing different sets of inhibitory molecules exist has not been determined.

METHODS

We studied the expression of the B and T lymphocyte attenuator (BTLA) on both peripheral blood mononuclear cells (PBMC) and intrahepatic lymphocytes, and the effects of blocking BTLA on circulating and intrahepatic T cells in CHB patients. Sixty-three CHB patients who underwent liver biopsy were enrolled. The expression of BTLA and PD-1 on PBMC and intrahepatic T cells was assessed by flow cytometry with antibodies to T cell differentiation molecules. Functional recovery was evaluated by analyzing production of interferon (IFN)-γ and interleukin (IL)-2 after incubation of T cells with anti-CD3 and irradiated mature dendritic cells in the presence of anti-BTLA, anti-PD-1, or both.

RESULTS

Intrahepatic T cells expressed higher levels of BTLA than their peripheral counterparts. A significant fraction of intrahepatic T cells coexpressed BTLA and PD-1 and showed deep exhaustion of T cell responses. Blockade of the BTLA pathway enhanced both intrahepatic and PBMC T cell proliferation and cytokine secretion, and exhibited an additive effect upon blockage of PD-1.

CONCLUSIONS

Upregulation of inhibitory receptor BTLA restricts T cell responses in CHB. T cell exhaustion by high antigen concentrations exacerbates dysfunction of peripheral and intrahepatic T cells. Blockage of BTLA is a potential therapeutic approach for chronic HBV infection that may act by restoring antiviral T cell responses.

B and T lymphocyte attenuator expression on CD4+ T-cells associates with sepsis and subsequent infections in ICU patients

Introduction

Sepsis is a deadly inflammatory condition that often leads to an immune suppressed state; however, the events leading to this state remain poorly understood. B and T lymphocyte attenuator (BTLA) is an immune-regulatory receptor shown to effectively inhibit CD4+ T-cell function. Therefore, our objectives were to determine: 1) if lymphocyte BTLA expression was altered in critically ill patients and experimentally induced septic mice, 2) whether augmented CD4+ T-cell BTLA expression was associated with poor septic patient outcomes, and 3) if BTLA expression affected the CD4+ T-cell apoptotic cell loss observed in the lymphoid organs of septic mice.

Methods

Changes in CD4+ lymphocyte BTLA expression were compared with morbid event development in critically ill ICU patients (11 septic and 28 systemic inflammatory response syndrome subjects). Wild type and BTLA gene deficient mice were utilized to evaluate the expression and role of BTLA in septic lymphocyte apoptotic cell loss.

Results

The observed septic ICU patients had a significantly higher percentage of peripheral blood BTLA+ CD4+ lymphocytes compared with critically ill non-septic individuals. Moreover, the non-septic patients with CD4+ T-cells that were greater than 80% BTLA+ were more susceptible to developing nosocomial infections. Additionally, in general, critically ill patients with CD4+ T-cells that were greater than 80% BTLA+ had longer hospital stays. Comparatively, circulating CD4+ T-cell and B-cell BTLA expression increased in septic mice, which associated with the increased septic loss of these cells. Finally, the loss of these cells and cellular apoptosis induction in primary and secondary lymphoid organs were reversed in BTLA deficient mice.

Conclusions

An increased BTLA+ CD4+ lymphocyte frequency in the observed critically ill non-septic patients was associated with a subsequent infection; therefore, BTLA may act as a biomarker to help determine nosocomial infection development. Additionally, BTLA expression contributed to primary and secondary lymphoid organ apoptotic cell loss in experimentally septic mice; thus, BTLA-induced apoptotic lymphocyte loss may be a mechanism for increased nosocomial infection risk in critically ill patients. This study had a relatively small human subject cohort; therefore, we feel these findings warrant future studies evaluating the use of BTLA as a critically ill patient nosocomial infection biomarker.

CMV-specific CD8+ T-cell function is not impaired in chronic lymphocytic leukemia

In chronic lymphocytic leukemia (CLL), CD8(+) T cells exhibit features of exhaustion and impaired functionality. Yet, reactivations of latent viruses such as cytomegalovirus (CMV) are uncommon in untreated CLL, suggesting that antiviral responses are uncompromised. We analyzed phenotypical and functional characteristics of CMV-specific CD8(+) T cells in CLL patients in comparison with age-matched healthy controls (HCs). Despite increased expression of the inhibitory receptors PD1, CD160, and CD244 on total CD8(+) T cells in CLL, expression levels of these markers were decreased on CMV-tetramer(+)CD8(+) T cells. Second, cytokine production upon stimulation with both phorbol 12-myristate 13-acetate/ionomycin and CMV-peptide-loaded antigen-presenting cells was intact in CMV-tetramer(+)CD8(+) T cells. Third, CMV-tetramer(+)CD8(+) T cells of CLL patients and HCs were equally effective in killing CMV-peptide-loaded target cells. Finally, quantitative imaging flow cytometry revealed that the proportion of CD8(+) T cells forming immunologic synapses with CMV-peptide-loaded B cells was intact. In conclusion, despite evidence for global T-cell dysfunction in CLL, we show here that CLL-derived CMV-specific CD8(+) T cells display lower expression of exhaustion markers and are functionally intact. These data indicate that the changes in the T-cell compartment in CLL may be more heterogeneous than presently assumed.

Association of the costimulatory molecule gene polymorphisms and active cytomegalovirus infection in hematopoietic stem cell transplant patients

Determinative associations may exist between costimulatory molecule gene polymorphisms with a variety of post hematopoietic stem cell transplantation (HSCT) viral related clinical outcomes especially acute graft versus host disease (aGVHD). Therefore in this study the associations between costimulatory molecule gene polymorphisms including: cytotoxic T-lymphocyte antigen-4 (CTLA4), programmed cell death-1 (PD-1), inducible T cell costimulator (ICOS), and cluster differentiation 28 (CD28) with active cytomegalovirus (CMV) infection were evaluated in HSCT patients. The 72 allogeneic HSCT patients with and without aGVHD were enrolled in this cross sectional study between years: 2004-2011. The single nucleotide polymorphisms in loci of the costimulatory molecules including: CTLA4 gene (-318 C/T, 1722 T/C, 1661 A/G, +49 A/G), PD-1 gene (PD-1.3 A/G, PD-1.9 C/T), ICOS gene (1720 C/T), and CD28 gene (+17 C/T) were analyzed in studied HSCT patients by PCR-RFLP methods. The active CMV infection was evaluated in fresh EDTA-treated blood samples of each allogeneic HSCT patients by CMV antigenemia kit according to manufacturer's instruction. Active CMV infection was found in 11 of 72 (15.27 %) of allogeneic HSCT patients. The T allele and TT genotype of the CD28 +17 C/T were significantly higher frequency in active CMV infected allogeneic HSCT patients experienced aGVHD. The G allele and GG genotype of the CTLA4 -1661 A/G were significantly higher frequent in active CMV infected allogeneic HSCT patients experienced low grade of aGVHD. Finally, finding of significant associations between CD28 +17 C/T and CTLA4 -1661 A/G genotypes with CMV active infection in allogeneic HSCT patients experienced aGVHD emphasize on the importance of the genetic pattern of costimulatory genes in outcomes of active CMV infection in HSCT patients needs completed studies.

Association of the costimulatory molecule gene polymorphisms and active cytomegalovirus infection in hematopoietic stem cell transplant patients

Determinative associations may exist between costimulatory molecule gene polymorphisms with a variety of post hematopoietic stem cell transplantation (HSCT) viral related clinical outcomes especially acute graft versus host disease (aGVHD). Therefore in this study the associations between costimulatory molecule gene polymorphisms including: cytotoxic T-lymphocyte antigen-4 (CTLA4), programmed cell death-1 (PD-1), inducible T cell costimulator (ICOS), and cluster differentiation 28 (CD28) with active cytomegalovirus (CMV) infection were evaluated in HSCT patients. The 72 allogeneic HSCT patients with and without aGVHD were enrolled in this cross sectional study between years: 2004-2011. The single nucleotide polymorphisms in loci of the costimulatory molecules including: CTLA4 gene (-318 C/T, 1722 T/C, 1661 A/G, +49 A/G), PD-1 gene (PD-1.3 A/G, PD-1.9 C/T), ICOS gene (1720 C/T), and CD28 gene (+17 C/T) were analyzed in studied HSCT patients by PCR-RFLP methods. The active CMV infection was evaluated in fresh EDTA-treated blood samples of each allogeneic HSCT patients by CMV antigenemia kit according to manufacturer's instruction. Active CMV infection was found in 11 of 72 (15.27 %) of allogeneic HSCT patients. The T allele and TT genotype of the CD28 +17 C/T were significantly higher frequency in active CMV infected allogeneic HSCT patients experienced aGVHD. The G allele and GG genotype of the CTLA4 -1661 A/G were significantly higher frequent in active CMV infected allogeneic HSCT patients experienced low grade of aGVHD. Finally, finding of significant associations between CD28 +17 C/T and CTLA4 -1661 A/G genotypes with CMV active infection in allogeneic HSCT patients experienced aGVHD emphasize on the importance of the genetic pattern of costimulatory genes in outcomes of active CMV infection in HSCT patients needs completed studies.

Expression of B and T lymphocyte attenuator (BTLA) in macrophages contributes to the fulminant hepatitis caused by murine hepatitis virus strain-3

OBJECTIVES

Fulminant viral hepatitis (FH) remains a serious clinical problem for which the underlying pathogenesis remains unclear. The B and T lymphocyte attenuator (BTLA) is an immunoglobulin-domain-containing protein that has the capacity to maintain peripheral tolerance and limit immunopathological damage during immune responses. However, its precise role in FH has yet to be investigated.

DESIGN

BTLA-deficient (BTLA-/-) mice and their wild-type littermates were infected with murine hepatitis virus strain-3 (MHV-3), and the levels of tissue damage, cell apoptosis, serum liver enzymes, fibrinogen-like protein 2 (FGL2) and cytokine production were measured and compared. Survival rate was studied after MHV-3 infection with or without adoptive transferring macrophages.

RESULTS

FGL2 production, liver and spleen damage, and mortality were significantly reduced in BTLA-/- mice infected with MHV-3. This effect is due to rapid, TRAIL (TNF-related apoptosis-inducing ligand)-dependent apoptosis of MHV-3-infected macrophages in BTLA-/- mice. The early loss of macrophages resulted in reduced pathogenic tumour necrosis factor α (TNFα) and FGL2 levels and lower viral titres. The importance of TNFα in MHV-3-induced pathology was demonstrated by increased mortality in TNFα-treated MHV-3-infected BTLA-/- mice, whereas TNFα-/- mice were resistant to the infection. Moreover, adoptively transferring macrophages to BTLA-/- mice caused sensitisation, whereas blocking BTLA protected wild-type mice from virus-induced FH mortality.

CONCLUSIONS

BTLA promotes the pathogenesis of virus-induced FH by enhancing macrophage viability and function. Targeting BTLA may be a novel strategy for the treatment of FH.

The co-receptor BTLA negatively regulates human Vγ9Vδ2 T-cell proliferation: a potential way of immune escape for lymphoma cells

Vγ9Vδ2 cells, the major γδ T-cell subset in human peripheral blood, represent a T-cell subset that displays reactivity against microbial agents and tumors. The biology of Vγ9Vδ2 T cells remains poorly understood. We show herein that the interaction between B- and T-lymphocyte attenuator (BTLA) and herpesvirus entry mediator (HVEM) is a major regulator of Vγ9Vδ2 T-cell proliferation control. BTLA was strongly expressed at the surface of resting Vγ9Vδ2 T cells and inversely correlated with T-cell differentiation. BTLA-HVEM blockade by monoclonal antibodies resulted in the enhancement of Vγ9Vδ2 T-cell receptor-mediated signaling, whereas BTLA-HVEM interaction led to a decrease in phosphoantigen-mediated proliferation by inducing a partial S-phase arrest. Our data also suggested that BTLA-HVEM might participate in the control of γδ T-cell differentiation. In addition, the proliferation of autologous γδ T cells after exposition to lymphoma cells was dramatically reduced through BTLA-HVEM interaction. These data suggest that HVEM interaction with BTLA may play a role in lymphomagenesis by interfering with Vγ9Vδ2 T-cell proliferation. Moreover, BTLA stimulation of Vγ9Vδ2 T cells appears as a new possible mechanism of immune escape by lymphoma cells.

Therapeutic potential of B and T lymphocyte attenuator expressed on CD8+ T cells for contact hypersensitivity

In the past decade, mechanisms underlying allergic contact dermatitis have been intensively investigated by using contact hypersensitivity (CHS) models in mice. However, the regulatory mechanisms, which could be applicable for the treatment of allergic contact dermatitis, are still largely unknown. To determine the roles of B and T lymphocyte attenuator (BTLA), a CD28 family coinhibitory receptor, in hapten-induced CHS, BTLA-deficient (BTLA(-/-)) mice and littermate wild-type (WT) mice were subjected to DNFB-induced CHS, severe combined immunodeficient (SCID) mice were injected with CD4(+) T cells, and CD8(+) T cells from either WT mice or BTLA(-/-) mice were subjected to CHS. BTLA(-/-) mice showed enhanced DNFB-induced CHS and proliferation and IFN-γ production of CD8(+) T cells as compared with WT mice. SCID mice injected with WT CD4(+) T cells and BTLA(-/-) CD8(+) T cells exhibited more severe CHS as compared with those injected with WT CD4(+) T cells and WT CD8(+) T cells. On the other hand, SCID mice injected with BTLA(-/-) CD4(+) T cells and WT CD8(+) T cells exhibited similar CHS to those injected with WT CD4(+) T cells and WT CD8(+) T cells. Finally, to evaluate the therapeutic potential of an agonistic agent for BTLA on CHS, the effects of an agonistic anti-BTLA antibody (6A6) on CHS were examined. In vivo injection of 6A6 suppressed DNFB-induced CHS and IFN-γ production of CD8(+) T cells. Taken together, these results suggest that stimulation of BTLA with agonistic agents has therapeutic potential in CHS.

The intrahepatic expression and distribution of BTLA and its ligand HVEM in patients with HBV-related acute-on-chronic liver failure

Objective

It has been demonstrated that signals from the inhibitory receptor B and T lymphocyte attenuator (BTLA) are involved in regulating the pathogenesis of infectious diseases. However, the expression and anatomical distribution of BTLA and its ligand, the herpes virus entry mediator (HVEM), have not yet been determined in cases of HBV-related acute-on-chronic liver failure (HBV-ACLF) patients.

Methods

In this study, the expression of BTLA and HVEM in liver tissues from HBV-ACLF, chronic hepatitis B (CHB) patients and healthy individuals was analyzed by immunohistochemistry.

Results

The results of this analysis demonstrated that both molecules were observed in the HBV-ACLF samples and that their expression was chiefly in the infiltrating inflammatory cells and the damaged bile ducts. However, they were absent in liver sections from CHB patients and healthy controls. Immunofluorescence double-staining indicated that BTLA was found on CK-18⁺ epithelial cells, CD31⁺ endothelial cells, CD68⁺ macrophages, CD56⁺ NK cells, CD16⁺ monocytes, CD3⁺ , CD8⁺ T cells, and Foxp3⁺ regulatory T cells (Treg). By contrast, HVEM expression was restricted to CK18⁺ epithelial cells and CD68⁺ macrophages. Moreover, the expression of several members of the B7 superfamily, including PD-L1, PD-L2, B7-H3 and B7-H4, was also detected in these liver tissues, and these proteins were co-expressed with HVEM. Interestingly, the expression of fibrinogen-like protein 2 (FGL2), a virus-induced procoagulant molecule, was also found in liver sections from HBV-ACLF, this molecule also co-expresses with BTLA and HVEM.

Conclusions

These results suggest that BTLA-HVEM signaling is likely to affect the pathogenesis of HBV-ACLF, a clear understanding of the functional roles of these proteins should further elucidate the disease process.

Virtual slides

The virtual slide(s) for this article can be found here: http://www.diagnosticpathology.diagnomx.eu/vs/8080806838149123

CpG-ODN-induced sustained expression of BTLA mediating selective inhibition of human B cells

BTLA (B- and T-lymphocyte attenuator) is a prominent co-receptor that is structurally and functionally related to CTLA-4 and PD-1. In T cells, BTLA inhibits TCR-mediated activation. In B cells, roles and functions of BTLA are still poorly understood and have never been studied in the context of B cells activated by CpG via TLR9. In this study, we evaluated the expression of BTLA depending on activation and differentiation of human B cell subsets in peripheral blood and lymph nodes. Stimulation with CpG upregulated BTLA, but not its ligand: herpes virus entry mediator (HVEM), on B cells in vitro and sustained its expression in vivo in melanoma patients after vaccination. Upon ligation with HVEM, BTLA inhibited CpG-mediated B cell functions (proliferation, cytokine production, and upregulation of co-stimulatory molecules), which was reversed by blocking BTLA/HVEM interactions. Interestingly, chemokine secretion (IL-8 and MIP1β) was not affected by BTLA/HVEM ligation, suggesting that BTLA-mediated inhibition is selective for some but not all B cell functions. We conclude that BTLA is an important immune checkpoint for B cells, as similarly known for T cells.

Functional exhaustion of CD4+ T lymphocytes during primary cytomegalovirus infection

Human CMV establishes lifelong persistence after primary infection. Chronic CMV infection is associated with intermittent viral reactivation inducing high frequencies of CD4+ T lymphocytes with potent antiviral and helper properties. Primary CMV infection is characterized by an intense viral replication lasting for several months. The impact of this prolonged exposure to high Ag loads on the functionality of CD4+ T cells remains incompletely understood. In pregnant women with primary CMV infection, we observed that CMV-specific CD4+ T lymphocytes had a decreased capacity to proliferate and to produce IL-2. A very large proportion of CMV-specific CD4+ T cells had downregulated the expression of CD28, a costimulatory molecule centrally involved in the production of IL-2. Unexpectedly, both CD28+ and CD28+ CD4+ T cells produced low levels of IL-2. This defective production of IL-2 was part of a larger downregulation of cytokine production. Indeed, CMV-specific CD4+ T cells produced lower amounts of IFN-γ and TNF-α and showed lower functional avidity during primary as compared with chronic infection. Increased programmed death-1 expression was observed in CD28+ CMV-specific CD4+ T cells, and programmed death-1 inhibition increased proliferative responses. These results indicate that primary CMV infection is associated with the exhaustion of CMV-specific CD4+ T cells displaying low functional avidity for viral Ags.

Herpesvirus exploitation of host immune inhibitory pathways

Herpesviruses employ a plethora of mechanisms to circumvent clearance by host immune responses. A key feature of mammalian immune systems is the employment of regulatory pathways that limit immune responsiveness. The primary functions of these mechanisms are to control autoimmunity and limit exuberant responses to harmless antigen in mucosal surfaces. However, such pathways can be exploited by viral pathogens to enable acute infection, persistence and dissemination. Herein, we outline the current understanding of inhibitory pathways in modulating antiviral immunity during herpesvirus infections in vivo and discuss strategies employed by herpesviruses to exploit these pathways to limit host antiviral immunity.

Coinhibitory molecules in hematologic malignancies: targets for therapeutic intervention

The adaptive immune system can be a potent defense mechanism against cancer; however, it is often hampered by immune suppressive mechanisms in the tumor microenvironment. Coinhibitory molecules expressed by tumor cells, immune cells, and stromal cells in the tumor milieu can dominantly attenuate T-cell responses against cancer cells. Today, a variety of coinhibitory molecules, including cytotoxic T lymphocyte–associated antigen-4, programmed death-1, B and T lymphocyte attenuator, LAG3, T-cell immunoglobulin and mucin domain 3, and CD200 receptor, have been implicated in immune escape of cancer cells. Sustained signaling via these coinhibitory molecules results in functional exhaustion of T cells, during which the ability to proliferate, secrete cytokines, and mediate lysis of tumor cells is sequentially lost. In this review, we discuss the influence of coinhibitory pathways in suppressing autologous and allogeneic T cell–mediated immunity against hematologic malignancies. In addition, promising preclinical and clinical data of immunotherapeutic approaches interfering with negative cosignaling, either as monotherapy or in conjunction with vaccination strategies, are reviewed. Numerous studies indicate that coinhibitory signaling hampers the clinical benefit of current immunotherapies. Therefore, manipulation of coinhibitory networks is an attractive adjuvant immunotherapeutic intervention for hematologic cancers after standard treatment with chemotherapy and hematopoietic stem cell transplantation.