HVEM structures and mutants reveal distinct functions of binding to LIGHT and BTLA/CD160

Proteomic Investigation of Immune Checkpoints and Some of Their Inhibitors

Immune checkpoints are crucial molecules for the maintenance of antitumor immune responses. The activation or inhibition of these molecules is dependent on the interactions between receptors and ligands; such interactions can provide inhibitory or stimulatory signals to the various components of the immune system. Over the last 10 years, the inhibition of immune checkpoints, such as cytotoxic T lymphocyte antigen-4, programmed cell death-1, and programmed cell death ligand-1, has taken a leading role in immune therapy. This relatively recent therapy regime is based on the use of checkpoint inhibitors, which enhance the immune response towards various forms of cancer. For a subset of patients with specific forms of cancer, these inhibitors can induce a durable response to therapy; however, the medium response rate to such therapy remains relatively poor. Recent research activities have demonstrated that the disease response to this highly promising therapy resembles the response of many forms of cancer to chemotherapy, where an encouraging initial response is followed by acquired resistance to treatment and progress of the disease. That said, these inhibitors are now used as single agents or in combination with chemotherapies as first or second lines of treatment for about 50 types of cancer. The prevailing opinion regarding immune therapy suggests that for this approach of therapy to deliver on its promise, a number of challenges have to be circumvented. These challenges include understanding the resistance mechanisms to immune checkpoint blockade, the identification of more efficient inhibitors, extending their therapeutic benefits to a wider audience of cancer patients, better management of immune-related adverse side effects, and, more urgently the identification of biomarkers, which would help treating oncologists in the identification of patients who are likely to respond positively to the immune therapies and, last but not least, the prices of therapy which can be afforded by the highest number of patients. Numerous studies have demonstrated that understanding the interaction between these checkpoints and the immune system is essential for the development of efficient checkpoint inhibitors and improved immune therapies. In the present text, we discuss some of these checkpoints, their inhibitors, and some works in which mass spectrometry-based proteomic analyses were applied.

Pan-cancer analysis of immune checkpoint receptors and ligands in various cells in the tumor immune microenvironment

Drugs that target immune checkpoint have become the most popular weapon in cancer immunotherapy, yet only have practical benefits for a small percentage of patients. Tumor cells constantly interact with their microenvironment, which is made up of a variety of immune cells as well as endothelial cells and fibroblasts. Immune checkpoint expression and blocked signaling of immune cells in the tumor microenvironment (TME) are key to tumor progression. In this study, we perform deliberation convolution on the TCGA database for human lung, breast, and colorectal cancer to infer crosstalk between immune checkpoint receptors (ICRs) and ligands (ICLs) in TME of pan-carcinogenic solid tumor types, validated by flow cytometry. Analysis of immune checkpoints showed that there was little variation between different tumor types. It showed that CD160, LAG3, TIGIT were found to be highly expressed in CD8+ T cells instead of CD4+ T cells, PD-L1, PD-L2, CD86, LGALS9, TNFRSF14, LILRB4 and other ligands were highly expressed on macrophages, FVR, NECTIN2, FGL1 were highly expressed on Epithelial cells, CD200 was highly expressed in Endothelial cells, and CD80 was highly expressed in CD8 High expression on T cells. Overall, our study provides a new resource for the expression of immune checkpoints in TME on various types of cells. Significance: This study provides immune checkpoint expression of immune cells of multiple cancer types to infer immune mechanisms in the tumor microenvironment and provide ideas for the development of new immune checkpoint-blocking drugs.

Multilayered Computational Framework for Designing Peptide Inhibitors of HVEM-LIGHT Interaction

The herpesvirus entry mediator (HVEM) and its ligand LIGHT play crucial roles in immune system regulation, including T-cell proliferation, B-cell differentiation, and immunoglobulin secretion. However, excessive T-cell activation can lead to chronic inflammation and autoimmune diseases. Thus, inhibiting the HVEM-LIGHT interaction emerges as a promising therapeutic strategy for these conditions and in preventing adverse reactions in organ transplantation. This study focused on designing peptide inhibitors, targeting the HVEM-LIGHT interaction, using molecular dynamics (MD) simulations of 65 peptides derived from HVEM. These peptides varied in length and disulfide-bond configurations, crucial for their interaction with the LIGHT trimer. By simulating 31 HVEM domain variants, including the full-length protein, we assessed conformational changes upon LIGHT binding to understand the influence of HVEM segments and disulfide bonds on the binding mechanism. Employing multitrajectory microsecond-scale, all-atom MD simulations and molecular mechanics with generalized Born and surface area (MM-GBSA) binding energy estimation, we identified promising CRD2 domain variants with high LIGHT affinity. Notably, point mutations in these variants led to a peptide with a single disulfide bond (C58-C73) and a K54E substitution, exhibiting the highest binding affinity. The importance of the CRD2 domain and Cys58-Cys73 disulfide bond for interrupting HVEM-LIGHT interaction was further supported by analyzing truncated CRD2 variants, demonstrating similar binding strengths and mechanisms. Further investigations into the binding mechanism utilized steered MD simulations at various pulling speeds and umbrella sampling to estimate the energy profile of HVEM-based inhibitors with LIGHT. These comprehensive analyses revealed key interactions and different binding mechanisms, highlighting the increased binding affinity of selected peptide variants. Experimental circular dichroism techniques confirmed the structural properties of these variants. This study not only advances our understanding of the molecular basis of HVEM-LIGHT interactions but also provides a foundation for developing novel therapeutic strategies for immune-related disorders. Furthermore, it sets a gold standard for peptide inhibitor design in drug development due to its systematic approach.

The BTLA-HVEM axis restricts CAR T cell efficacy in cancer

The efficacy of T cell-based immunotherapies is limited by immunosuppressive pressures in the tumor microenvironment. Here we show a predominant role for the interaction between BTLA on effector T cells and HVEM (TNFRSF14) on immunosuppressive tumor microenvironment cells, namely regulatory T cells. High BTLA expression in chimeric antigen receptor (CAR) T cells correlated with poor clinical response to treatment. Therefore, we deleted BTLA in CAR T cells and show improved tumor control and persistence in models of lymphoma and solid malignancies. Mechanistically, BTLA inhibits CAR T cells via recruitment of tyrosine phosphatases SHP-1 and SHP-2, upon trans engagement with HVEM. BTLA knockout thus promotes CAR signaling and subsequently enhances effector function. Overall, these data indicate that the BTLA-HVEM axis is a crucial immune checkpoint in CAR T cell immunotherapy and warrants the use of strategies to overcome this barrier.

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.

The BTLA-HVEM complex - The future of cancer immunotherapy

The BTLA-HVEM complex plays a pivotal role in cancer and cancer immunotherapy by regulating immune responses. Dysregulation of BTLA and HVEM expression contributes to immunosuppression and tumor progression across various cancer types. Targeting the interaction between BTLA and HVEM holds promise for enhancing anti-tumor immune responses. Disruption of this complex presents a valuable avenue for advancing cancer immunotherapy strategies. Aberrant expression of BTLA and HVEM adversely affects immune cell function, particularly T cells, exacerbating tumor evasion mechanisms. Understanding and modulating the BTLA-HVEM axis represents a crucial aspect of designing effective immunotherapeutic interventions against cancer. Here, we summarize the current knowledge regarding the structure and function of BTLA and HVEM, along with their interaction with each other and various immune partners. Moreover, the expression of soluble and transmembrane forms of BTLA and HVEM in different types of cancer and their impact on the prognosis of patients is also discussed. Additionally, inhibitors of the proteins binding that might be used to block BTLA-HVEM interaction are reviewed. All the presented data highlight the plausible clinical application of BTLA-HVEM targeted therapies in cancer and autoimmune disease management. However, further studies are required to confirm the practical use of this concept. Despite the increasing number of reports on the BTLA-HVEM complex, many aspects of its biology and function still need to be elucidated. This review can be regarded as an encouragement and a guide to follow the path of BTLA-HVEM research.

Causal effects and immune cell mediators between prescription analgesic use and risk of infectious diseases: a Mendelian randomization study

Introduction

Clinical observations have found that prolonged use of analgesics increases the incidence of infection. However, the direct causal relationship between prescription analgesic use (PAU) and risk of infection (ROI) remains unclear.

Methods

This study used Mendelian randomization (MR) design to estimate the causal effect of PAU on ROI, as well as their mediating factors. Genetic data on prescription analgesics use and immune cells were obtained from published GWAS. Additionally, data on ROI were extracted from the FinnGen database. Two-sample MR analysis and multivariate MR (MVMR) analysis were performed using inverse variance weighting (IVW) to ascertain the causal association between PAU and ROI. Finally, 731 immune cell phenotypes were analyzed for their mediating role between analgesics and infection.

Results

Using two-sample MR, IVW modeling showed that genetically predicted opioid use was associated with increased risk of pulmonary infection (PI) (OR = 1.13, 95% CI: 1.05-1.21, p< 0.001) and upper respiratory infection (URI) (OR = 1.18, 95% CI: 1.08-1.30, p< 0.001); non-steroidal anti-inflammatory drugs (NSAIDs) were related to increased risk of skin and subcutaneous tissue infection (OR = 1.21, 95% CI: 1.05-1.39, p = 0.007), and antimigraine preparations were linked to a reduced risk of virus hepatitis (OR = 0.79, 95% CI: 0.69-0.91, p< 0.001). In MVMR, the association of opioids with URI and PI remained after accounting for cancer conditions. Even with a stricter threshold (p< 0.05/30), we found a significant causal association between opioids and respiratory infections (URI/PI). Finally, mediation analyses found that analgesics influence the ROI through different phenotypes of immune cells as mediators.

Conclusion

This MR study provides new genetic evidence for the causal relationship between PAU and ROI, and the mediating role of immune cells was demonstrated.

Immune activation of the p75 neurotrophin receptor: implications in neuroinflammation

Despite structural similarity with other tumor necrosis factor receptor superfamily (TNFRSF) members, the p75 neurotrophin receptor (p75NTR, TNFR16) mediates pleiotropic biological functions not shared with other TNFRs. The high level of p75NTR expression in the nervous system instead of immune cells, its utilization of co-receptors, and its interaction with soluble dimeric, rather than soluble or cell-tethered trimeric ligands are all characteristics which distinguish it from most other TNFRs. Here, we compare these attributes to other members of the TNFR superfamily. In addition, we describe the recent evolutionary adaptation in B7-1 (CD80), an immunoglobulin (Ig) superfamily member, which allows engagement to neuronally-expressed p75NTR. B7-1-mediated binding to p75NTR occurs in humans and other primates, but not lower mammals due to specific sequence changes that evolved recently in primate B7-1. This discovery highlights an additional mechanism by which p75NTR can respond to inflammatory cues and trigger synaptic elimination in the brain through engagement of B7-1, which was considered to be immune-restricted. These observations suggest p75NTR does share commonality with other immune co-modulatory TNFR family members, by responding to immunoregulatory cues. The evolution of primate B7-1 to bind and elicit p75NTR-mediated effects on neuronal morphology and function are discussed in relationship to immune-driven modulation of synaptic actions during injury or inflammation.

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.

Investigation of LGALS2 expression in the TCGA database reveals its clinical relevance in breast cancer immunotherapy and drug resistance

Breast cancer (BRCA) is known as the leading cause of death in women worldwide and has a poor prognosis. Traditional therapeutic strategies such as surgical resection, radiotherapy and chemotherapy can cause adverse reactions such as drug resistance. Immunotherapy, a new treatment approach with fewer side effects and stronger universality, can prolong the survival of BRCA patients and even achieve clinical cure. However, due to population heterogeneity and other reasons, there are still certain factors that limit the efficacy of immunotherapy. Therefore, the importance of finding new tumor immune biomarker cannot be emphasized enough. Studies have reported that LGALS2 was closely related to immunotherapy efficacy, however, it is unclear whether it can act as an immune checkpoint for BRCA immunotherapy. In the current study, changes in LGALS2 expression were analyzed in public datasets such as TCGA-BRCA. We found that LGALS2 expression was associated with immune infiltration, drug resistance and other characteristics of BRCA. Moreover, high LGALS2 expression was closely related to immunotherapy response, and was associated with methylation modifications and clinical resistance for the first time. These findings may help to elucidate the role of LGALS2 in BRCA for the development and clinical application of future immunotherapy strategies against BRCA.

Expression of HPV-16 E6 and E7 oncoproteins alters Chlamydia trachomatis developmental cycle and induces increased levels of immune regulatory molecules

Introduction

Infection with Human Papillomavirus (HPV) is a recognized risk factor for Chlamydia trachomatis (CT) infection and vice versa. Coinfection of HPV and CT in women is a very common and usually asymptomatic finding that has been linked to increased risk of cervical cancer. It has been demonstrated that CT facilitates the entry of multiple high risk HPV genotypes, leading to damage of the mucosal barrier and interfering with immune responses and viral clearance, which ultimately favours viral persistence and malignant transformation. Although the facilitating effects elicited by CT infection on viral persistence have been reported, little is known about the consequences of HPV infection on CT development.

Methods

Herein, we took advantage of a genetically modified human cervical cell line co-expressing HPV-16 major oncogenic proteins E6 and E7, as an experimental model allowing to investigate the possible effects that HPV infection would have on CT development.

Results and discussion

Our results show that CT infection of HPV-16 E6E7 expressing cells induced an upregulation of the expression of E6E7 oncoproteins and host cell inhibitory molecules PD-L1, HVEM and CD160. Additionally, smaller chlamydial inclusions and reduced infectious progeny generation was observed in E6E7 cells. Ultrastructural analysis showed that expression of E6 and E7 did not alter total bacterial counts within inclusions but resulted in increased numbers of reticulate bodies (RB) and decreased production of infectious elementary bodies (EB). Our results indicate that during CT and HPV coinfection, E6 and E7 oncoproteins impair RB to EB transition and infectious progeny generation. On the other hand, higher expression of immune inhibitory molecules and HPV-16 E6E7 are cooperatively enhanced in CT-infected cells, which would favour both oncogenesis and immunosuppression. Our findings pose important implications for clinical management of patients with HPV and CT coinfection, suggesting that screening for the mutual infection could represent an opportunity to intervene and prevent severe reproductive health outcomes, such as cervical cancer and infertility.

T cell co-stimulatory and co-inhibitory pathways in atopic dermatitis

The use of immune checkpoint inhibitors (ICIs) targeting the T cell inhibitory pathways has revolutionized cancer treatment. However, ICIs might induce progressive atopic dermatitis (AD) by affecting T cell reactivation. The critical role of T cells in AD pathogenesis is widely known. T cell co-signaling pathways regulate T cell activation, where co-signaling molecules are essential for determining the magnitude of the T cell response to antigens. Given the increasing use of ICIs in cancer treatment, a timely overview of the role of T cell co-signaling molecules in AD is required. In this review, we emphasize the importance of these molecules involved in AD pathogenesis. We also discuss the potential of targeting T cell co-signaling pathways to treat AD and present the unresolved issues and existing limitations. A better understanding of the T cell co-signaling pathways would aid investigation of the mechanism, prognosis evaluation, and treatment of AD.

MicroRNAs with Multiple Targets of Immune Checkpoints, as a Potential Sensitizer for Immune Checkpoint Inhibitors in Breast Cancer Treatment

Breast cancer is the most common cancer type and the leading cause of cancer-associated mortality in women worldwide. In recent years, immune checkpoint inhibitors (ICIs) have made significant progress in the treatment of breast cancer, yet there are still a considerable number of patients who are unable to gain lasting and ideal clinical benefits by immunotherapy alone, which leads to the development of a combination regimen as a novel research hotspot. Furthermore, one miRNA can target several checkpoint molecules, mimicking the therapeutic effect of a combined immune checkpoint blockade (ICB), which means that the miRNA therapy has been considered to increase the efficiency of ICIs. In this review, we summarized potential miRNA therapeutics candidates which can affect multiple targets of immune checkpoints in breast cancer with more therapeutic potential, and the obstacles to applying miRNA therapeutically through the analyses of the resources available from a drug target perspective. We also included the content of "too many targets for miRNA effect" (TMTME), combined with applying TargetScan database, to discuss adverse events. This review aims to ignite enthusiasm to explore the application of miRNAs with multiple targets of immune checkpoint molecules, in combination with ICIs for treating breast cancer.

Epithelial HVEM maintains intraepithelial T cell survival and contributes to host protection

Intraepithelial T cells (IETs) are in close contact with intestinal epithelial cells and the underlying basement membrane, and they detect invasive pathogens. How intestinal epithelial cells and basement membrane influence IET survival and function, at steady state or after infection, is unclear. The herpes virus entry mediator (HVEM), a member of the TNF receptor superfamily, is constitutively expressed by intestinal epithelial cells and is important for protection from pathogenic bacteria. Here, we showed that at steady-state LIGHT, an HVEM ligand, binding to epithelial HVEM promoted the survival of small intestine IETs. RNA-seq and addition of HVEM ligands to epithelial organoids indicated that HVEM increased epithelial synthesis of basement membrane proteins, including collagen IV, which bound to β₁ integrins expressed by IETs. Therefore, we proposed that IET survival depended on β₁ integrin binding to collagen IV and showed that β₁ integrin-collagen IV interactions supported IET survival in vitro. Moreover, the absence of β₁ integrin expression by T lymphocytes decreased TCR αβ⁺ IETs in vivo. Intravital microscopy showed that the patrolling movement of IETs was reduced without epithelial HVEM. As likely consequences of decreased number and movement, protective responses to Salmonella enterica were reduced in mice lacking either epithelial HVEM, HVEM ligands, or β₁ integrins. Therefore, IETs, at steady state and after infection, depended on HVEM expressed by epithelial cells for the synthesis of collagen IV by epithelial cells. Collagen IV engaged β₁ integrins on IETs that were important for their maintenance and for their protective function in mucosal immunity.

Realigning the LIGHT signaling network to control dysregulated inflammation

Advances in understanding the physiologic functions of the tumor necrosis factor superfamily (TNFSF) of ligands, receptors, and signaling networks are providing deeper insight into pathogenesis of infectious and autoimmune diseases and cancer. LIGHT (TNFSF14) has emerged as an important modulator of critical innate and adaptive immune responses. LIGHT and its signaling receptors, herpesvirus entry mediator (TNFRSF14), and lymphotoxin β receptor, form an immune regulatory network with two co-receptors of herpesvirus entry mediator, checkpoint inhibitor B and T lymphocyte attenuator, and CD160. Deciphering the fundamental features of this network reveals new understanding to guide therapeutic development. Accumulating evidence from infectious diseases points to the dysregulation of the LIGHT network as a disease-driving mechanism in autoimmune and inflammatory reactions in barrier organs, including coronavirus disease 2019 pneumonia and inflammatory bowel diseases. Recent clinical results warrant further investigation of the LIGHT regulatory network and application of target-modifying therapeutics for disease intervention.

The Neonatal Innate Immune Response to Sepsis: Checkpoint Proteins as Novel Mediators of This Response and as Possible Therapeutic/Diagnostic Levers

Sepsis, a dysfunctional immune response to infection leading to life-threatening organ injury, represents a significant global health issue. Neonatal sepsis is disproportionately prevalent and has a cost burden of 2-3 times that of adult patients. Despite this, no widely accepted definition for neonatal sepsis or recommendations for management exist and those created for pediatric patients are significantly limited in their applicability to this unique population. This is in part due to neonates' reliance on an innate immune response (which is developmentally more prominent in the neonate than the immature adaptive immune response) carried out by dysfunctional immune cells, including neutrophils, antigen-presenting cells such as macrophages/monocytes, dendritic cells, etc., natural killer cells, and innate lymphoid regulatory cell sub-sets like iNKT cells, γδ T-cells, etc. Immune checkpoint inhibitors are a family of proteins with primarily suppressive/inhibitory effects on immune and tumor cells and allow for the maintenance of self-tolerance. During sepsis, these proteins are often upregulated and are thought to contribute to the long-term immunosuppression seen in adult patients. Several drugs targeting checkpoint inhibitors, including PD-1 and PD-L1, have been developed and approved for the treatment of various cancers, but no such therapeutics have been approved for the management of sepsis. In this review, we will comparatively discuss the role of several checkpoint inhibitor proteins, including PD-1, PD-L1, VISTA, and HVEM, in the immune response to sepsis in both adults and neonates, as well as posit how they may uniquely propagate their actions through the neonatal innate immune response. We will also consider the possibility of leveraging these proteins in the clinical setting as potential therapeutics/diagnostics that might aid in mitigating neonatal septic morbidity/mortality.