The immunological synapse as a pharmacological target

Changing the location of proteins on the cell surface is a promising strategy for modulating T cell functions

Targeting immune receptors on T cells is a common strategy to treat cancer and autoimmunity. Frequently, this is accomplished through monoclonal antibodies targeting the ligand binding sites of stimulatory or inhibitory co-receptors. Blocking ligand binding prevents downstream signalling and modulates specific T cell functions. Since 1985, the FDA has approved over 100 monoclonal antibodies against immune receptors. This therapeutic approach significantly improved the care of patients with numerous immune-related conditions; however, many patients are unresponsive, and some develop immune-related adverse events. One reason for that is the lack of consideration for the localization of these receptors on the cell surface of the immune cells in the context of the immune synapse. In addition to blocking ligand binding, changing the location of these receptors on the cell surface within the different compartments of the immunological synapse could serve as an alternative, efficient, and safer approach to treating these patients. This review discusses the potential therapeutic advantages of altering proteins' localization within the immune synapse and summarizes published work in this field. It also discusses the novel use of bispecific antibodies to induce the clustering of receptors on the cell surface. It presents the rationale for developing novel antibodies, targeting the organization of signalling receptor complexes on the cell surface. This approach offers an innovative and emerging technology to treat cancer patients resistant to current immunotherapies.

Newer generations of multi-target CAR and STAb-T immunotherapeutics: NEXT CART Consortium as a cooperative effort to overcome current limitations

Adoptive T cellular immunotherapies have emerged as relevant approaches for treating cancer patients who have relapsed or become refractory (R/R) to traditional cancer treatments. Chimeric antigen receptor (CAR) T-cell therapy has improved survival in various hematological malignancies. However, significant limitations still impede the widespread adoption of these therapies in most cancers. To advance in this field, six research groups have created the "NEXT Generation CART MAD Consortium" (NEXT CART) in Madrid's Community, which aims to develop novel cell-based immunotherapies for R/R and poor prognosis cancers. At NEXT CART, various basic and translational research groups and hospitals in Madrid concur to share and synergize their basic expertise in immunotherapy, gene therapy, and immunological synapse, and clinical expertise in pediatric and adult oncology. NEXT CART goal is to develop new cell engineering approaches and treatments for R/R adult and pediatric neoplasms to evaluate in multicenter clinical trials. Here, we discuss the current limitations of T cell-based therapies and introduce our perspective on future developments. Advancement opportunities include developing allogeneic products, optimizing CAR signaling domains, combining cellular immunotherapies, multi-targeting strategies, and improving tumor-infiltrating lymphocytes (TILs)/T cell receptor (TCR) therapy. Furthermore, basic studies aim to identify novel tumor targets, tumor molecules in the tumor microenvironment that impact CAR efficacy, and strategies to enhance the efficiency of the immunological synapse between immune and tumor cells. Our perspective of current cellular immunotherapy underscores the potential of these treatments while acknowledging the existing hurdles that demand innovative solutions to develop their potential for cancer treatment fully.

Cellular and molecular signaling towards T cell immunological self-tolerance

The binding of a cognate antigen to T cell receptor (TCR) complex triggers a series of intracellular events controlling T cell activation, proliferation, and differentiation. Upon TCR engagement, different negative regulatory feedback mechanisms are rapidly activated to counterbalance T cell activation, thus preventing excessive signal propagation and promoting the induction of immunological self-tolerance. Both positive and negative regulatory processes are tightly controlled to ensure the effective elimination of foreign antigens while limiting surrounding tissue damage and autoimmunity. In this context, signals deriving from co-stimulatory molecules (i.e., CD80, CD86), co-inhibitory receptors (PD-1, CTLA-4), the tyrosine phosphatase CD45 and cytokines such as IL-2 synergize with TCR-derived signals to guide T cell fate and differentiation. The balance of these mechanisms is also crucial for the generation of CD4+ Foxp3+ regulatory T cells, a cellular subset involved in the control of immunological self-tolerance. This review provides an overview of the most relevant pathways induced by TCR activation combined with those derived from co-stimulatory and co-inhibitory molecules implicated in the cell-intrinsic modulation of T cell activation. In addition to the latter, we dissected mechanisms responsible for T cell-mediated suppression of immune cell activation through regulatory T cell generation, homeostasis, and effector functions. We also discuss how imbalanced signaling derived from TCR and accessory molecules can contribute to autoimmune disease pathogenesis.

Explainable machine learning for profiling the immunological synapse and functional characterization of therapeutic antibodies

Therapeutic antibodies are widely used to treat severe diseases. Most of them alter immune cells and act within the immunological synapse; an essential cell-to-cell interaction to direct the humoral immune response. Although many antibody designs are generated and evaluated, a high-throughput tool for systematic antibody characterization and prediction of function is lacking. Here, we introduce the first comprehensive open-source framework, scifAI (single-cell imaging flow cytometry AI), for preprocessing, feature engineering, and explainable, predictive machine learning on imaging flow cytometry (IFC) data. Additionally, we generate the largest publicly available IFC dataset of the human immunological synapse containing over 2.8 million images. Using scifAI, we analyze class frequency and morphological changes under different immune stimulation. T cell cytokine production across multiple donors and therapeutic antibodies is quantitatively predicted in vitro, linking morphological features with function and demonstrating the potential to significantly impact antibody design. scifAI is universally applicable to IFC data. Given its modular architecture, it is straightforward to incorporate into existing workflows and analysis pipelines, e.g., for rapid antibody screening and functional characterization.

Population dynamics of immunological synapse formation induced by bispecific T cell engagers predict clinical pharmacodynamics and treatment resistance

Effector T cells need to form immunological synapses (IS) with recognized target cells to elicit cytolytic effects. Facilitating IS formation is the principal pharmacological action of most T cell-based cancer immunotherapies. However, the dynamics of IS formation at the cell population level, the primary driver of the pharmacodynamics of many cancer immunotherapies, remains poorly defined. Using classic immunotherapy CD3/CD19 bispecific T cell engager (BiTE) as our model system, we integrate experimental and theoretical approaches to investigate the population dynamics of IS formation and their relevance to clinical pharmacodynamics and treatment resistance. Our models produce experimentally consistent predictions when defining IS formation as a series of spatiotemporally coordinated events driven by molecular and cellular interactions. The models predict tumor-killing pharmacodynamics in patients and reveal trajectories of tumor evolution across anatomical sites under BiTE immunotherapy. Our models highlight the bone marrow as a potential sanctuary site permitting tumor evolution and antigen escape. The models also suggest that optimal dosing regimens are a function of tumor growth, CD19 expression, and patient T cell abundance, which confer adequate tumor control with reduced disease evolution. This work has implications for developing more effective T cell-based cancer immunotherapies.

Vesicular traffic-mediated cell-to-cell signaling at the immune synapse in Ankylosing Spondylitis

The chronic inflammatory disease ankylosing spondylitis (AS) is marked by back discomfort, spinal ankylosis, and extra-articular symptoms. In AS, inflammation is responsible for both pain and spinal ankylosis. However, the processes that sustain chronic inflammation remain unknown. Despite the years of research conducted to decipher the intricacy of AS, little progress has been made in identifying the signaling events that lead to the development of this disease. T cells, an immune cell type that initiates and regulates the body's response to infection, have been established to substantially impact the development of AS. T lymphocytes are regarded as a crucial part of adaptive immunity for the control of the immune system. A highly coordinated interaction involving antigen-presenting cells (APCs) and T cells that regulate T cell activation constitutes an immunological synapse (IS). This first phase leads to the controlled trafficking of receptors and signaling mediators involved in folding endosomes to the cellular interface, which allows the transfer of information from T cells to APCs through IS formation. Discrimination of self and nonself antigen is somatically learned in adaptive immunity. In an autoimmune condition such as AS, there is a disturbance of self/nonself antigen discrimination; available findings imply that the IS plays a preeminent role in the adaptive immune response. In this paper, we provide insights into the genesis of AS by evaluating recent developments in the function of vesicular trafficking in IS formation and the targeted release of exosomes enriched microRNAs (miRNA) at the synaptic region in T cells.

Epigenetic remodeling of the immune landscape in cancer: therapeutic hurdles and opportunities

The tumor immune microenvironment represents a sophisticated ecosystem where various immune cell subtypes communicate with cancer cells and stromal cells. The dynamic cellular composition and functional characteristics of the immune landscape along the trajectory of cancer development greatly impact the therapeutic efficacy and clinical outcome in patients receiving systemic antitumor therapy. Mounting evidence has suggested that epigenetic mechanisms are the underpinning of many aspects of antitumor immunity and facilitate immune state transitions during differentiation, activation, inhibition, or dysfunction. Thus, targeting epigenetic modifiers to remodel the immune microenvironment holds great potential as an integral part of anticancer regimens. In this review, we summarize the epigenetic profiles and key epigenetic modifiers in individual immune cell types that define the functional coordinates of tumor permissive and non-permissive immune landscapes. We discuss the immunomodulatory roles of current and prospective epigenetic therapeutic agents, which may open new opportunities in enhancing cancer immunotherapy or overcoming existing therapeutic challenges in the management of cancer.

Neutralization of the adaptor protein PAG by monoclonal antibody limits murine tumor growth

The transmembrane adaptor phosphoprotein associated with glycosphingolipid-enriched microdomains 1 (PAG) is phosphorylated in T cells downstream of PD-1 signaling and contributes to the resulting functional inhibition of multiple cellular processes. Furthermore, PAG expression is negatively correlated with survival in multiple human tumors and is a driver of murine tumor growth and immune evasion. Here we develop an antibody that targets the extracellular domain of human PAG, with cross-reactivity to murine PAG. We demonstrate that this antibody binds to extracellular PAG on intact cells and affects T cell activation. Finally, we show that administration of anti-PAG monoclonal antibody in combination with anti-PD-1 antibody to mice bearing MC38 tumors limited tumor growth and enhanced T cell infiltration to tumors.

PI3K in T Cell Adhesion and Trafficking

PI3K signalling is required for activation, differentiation, and trafficking of T cells. PI3Kδ, the dominant PI3K isoform in T cells, has been extensively characterised using PI3Kδ mutant mouse models and PI3K inhibitors. Furthermore, characterisation of patients with Activated PI3K Delta Syndrome (APDS) and mouse models with hyperactive PI3Kδ have shed light on how increased PI3Kδ activity affects T cell functions. An important function of PI3Kδ is that it acts downstream of TCR stimulation to activate the major T cell integrin, LFA-1, which controls transendothelial migration of T cells as well as their interaction with antigen-presenting cells. PI3Kδ also suppresses the cell surface expression of CD62L and CCR7 which controls the migration of T cells across high endothelial venules in the lymph nodes and S1PR1 which controls lymph node egress. Therefore, PI3Kδ can control both entry and exit of T cells from lymph nodes as well as the recruitment to and retention of T cells within inflamed tissues. This review will focus on the regulation of adhesion receptors by PI3Kδ and how this contributes to T cell trafficking and localisation. These findings are relevant for our understanding of how PI3Kδ inhibitors may affect T cell redistribution and function.

The Emerging Role of the Innate Immune Response in Idiosyncratic Drug Reactions

Idiosyncratic drug reactions (IDRs) range from relatively common, mild reactions to rarer, potentially life-threatening adverse effects that pose significant risks to both human health and successful drug discovery. Most frequently, IDRs target the liver, skin, and blood or bone marrow. Clinical data indicate that most IDRs are mediated by an adaptive immune response against drug-modified proteins, formed when chemically reactive species of a drug bind to self-proteins, making them appear foreign to the immune system. Although much emphasis has been placed on characterizing the clinical presentation of IDRs and noting implicated drugs, limited research has focused on the mechanisms preceding the manifestations of these severe responses. Therefore, we propose that to address the knowledge gap between drug administration and onset of a severe IDR, more research is required to understand IDR-initiating mechanisms; namely, the role of the innate immune response. In this review, we outline the immune processes involved from neoantigen formation to the result of the formation of the immunologic synapse and suggest that this framework be applied to IDR research. Using four drugs associated with severe IDRs as examples (amoxicillin, amodiaquine, clozapine, and nevirapine), we also summarize clinical and animal model data that are supportive of an early innate immune response. Finally, we discuss how understanding the early steps in innate immune activation in the development of an adaptive IDR will be fundamental in risk assessment during drug development. SIGNIFICANCE STATEMENT: Although there is some understanding that certain adaptive immune mechanisms are involved in the development of idiosyncratic drug reactions, the early phase of these immune responses remains largely uncharacterized. The presented framework refocuses the investigation of IDR pathogenesis from severe clinical manifestations to the initiating innate immune mechanisms that, in contrast, may be quite mild or clinically silent. A comprehensive understanding of these early influences on IDR onset is crucial for accurate risk prediction, IDR prevention, and therapeutic intervention.

A combination of PD‑1/PD‑L1 inhibitors: The prospect of overcoming the weakness of tumor immunotherapy (Review)

Programmed cell death protein-1 (PD-1)/programmed death protein ligand-1 (PD-L1) inhibitors for treatment of a various types of cancers have revolutionized cancer immunotherapy. However, PD-1/PD-L1 inhibitors are associated with a low response rate and are only effective on a small number of patients with cancer. Development of an anti-PD-1/PD-L1 sensitizer for improving response rate and effectiveness of immunotherapy is a challenge. The present study reviews the synergistic effects of PD-1/PD-L1 inhibitor with oncolytic virus, tumor vaccine, molecular targeted drugs, immunotherapy, chemotherapy, radiotherapy, intestinal flora and traditional Chinese medicine, to provide information for development of effective combination therapies.