Integrins in T Cell Physiology

T cells use focal adhesions to pull themselves through confined environments

Immune cells are highly dynamic and able to migrate through environments with diverse biochemical and mechanical compositions. Their migration has classically been defined as amoeboid under the assumption that it is integrin independent. Here, we show that activated primary Th1 T cells require both confinement and extracellular matrix proteins to migrate efficiently. This migration is mediated through small and dynamic focal adhesions that are composed of the same proteins associated with canonical mesenchymal cell focal adhesions, such as integrins, talin, and vinculin. These focal adhesions, furthermore, localize to sites of contractile traction stresses, enabling T cells to pull themselves through confined spaces. Finally, we show that Th1 T cells preferentially follow tracks of other T cells, suggesting that these adhesions modify the extracellular matrix to provide additional environmental guidance cues. These results demonstrate not only that the boundaries between amoeboid and mesenchymal migration modes are ambiguous, but that integrin-mediated focal adhesions play a key role in T cell motility.

Migration of human T cells can be differentially directed by electric fields depending on the extracellular microenvironment

T cell migration plays an essential role in the immune response and T cell-based therapies. It can be modulated by chemical and physical cues such as electric fields (EFs). The mechanisms underlying electrotaxis (cell migration manipulated by EFs) are not fully understood and systematic studies with immune cells are rare. In this in vitro study, we show that direct current EFs with strengths of physiologically occurring EFs (25-200 mV/mm) can guide the migration of primary human CD4+ and CD8+ T cells on 2D substrates toward the anode and in a 3D environment differentially (CD4+ T cells show cathodal and CD8+ T cells show anodal electrotaxis). Overall, we find that EFs present a potent stimulus to direct T cell migration in different microenvironments in a cell-type-, substrate-, and voltage-dependent manner, while not significantly influencing T cell differentiation or viability.

KMT2D regulates activation, localization, and integrin expression by T-cells

Individuals with Kabuki syndrome present with immunodeficiency; however, how pathogenic variants in the gene encoding the histone-modifying enzyme lysine methyltransferase 2D (KMT2D) lead to immune alterations remain poorly understood. Following up on our prior report of KMT2D-altered integrin expression in B-cells, we performed targeted analyses of KMT2D's influence on integrin expression in T-cells throughout development (thymocytes through peripheral T-cells) in murine cells with constitutive- and conditional-targeted Kmt2d deletion. Using high-throughput RNA-sequencing and flow cytometry, we reveal decreased expression (both at the transcriptional and translational levels) of a cluster of leukocyte-specific integrins, which perturb aspects of T-cell activation, maturation, adhesion/localization, and effector function. H3K4me3 ChIP-PCR suggests that these evolutionary similar integrins are under direct control of KMT2D. KMT2D loss also alters multiple downstream programming/signaling pathways, including integrin-based localization, which can influence T-cell populations. We further demonstrated that KMT2D deficiency is associated with the accumulation of murine CD8+ single-positive (SP) thymocytes and shifts in both human and murine peripheral T-cell populations, including the reduction of the CD4+ recent thymic emigrant (RTE) population. Together, these data show that the targeted loss of Kmt2d in the T-cell lineage recapitulates several distinct features of Kabuki syndrome-associated immune deficiency and implicates epigenetic mechanisms in the regulation of integrin signaling.

Unconventional human CD61 pairing with CD103 promotes TCR signaling and antigen-specific T cell cytotoxicity

Cancer remains one of the leading causes of mortality worldwide, leading to increased interest in utilizing immunotherapy strategies for better cancer treatments. In the past decade, CD103+ T cells have been associated with better clinical prognosis in patients with cancer. However, the specific immune mechanisms contributing toward CD103-mediated protective immunity remain unclear. Here, we show an unexpected and transient CD61 expression, which is paired with CD103 at the synaptic microclusters of T cells. CD61 colocalization with the T cell antigen receptor further modulates downstream T cell antigen receptor signaling, improving antitumor cytotoxicity and promoting physiological control of tumor growth. Clinically, the presence of CD61+ tumor-infiltrating T lymphocytes is associated with improved clinical outcomes, mediated through enhanced effector functions and phenotype with limited evidence of cellular exhaustion. In conclusion, this study identified an unconventional and transient CD61 expression and pairing with CD103 on human immune cells, which potentiates a new target for immune-based cellular therapies.

Induction of a memory-like CD4+ T-cell phenotype by airway smooth muscle cells

In asthma, CD4+ T-cell interaction with airway smooth muscle (ASM) may enhance its contractile properties and promote its proliferation. However, less is known about the effects of this interaction on T cells. To explore the consequences of interaction of CD4+ T cells with ASM we placed the cells in co-culture and analyzed the phenotypic and functional changes in the T cells. Effector status as well as cytokine expression was assessed by flow cytometry. An increase in CD45RA-CD45RO+ memory T cells was observed after co-culture; however, these cells were not more responsive to CD3/28 restimulation. A reduction in mitochondrial coupling and an increase in the production of mitochondrial reactive oxygen species by CD4+ T cells post-restimulation suggested altered mitochondrial metabolism after co-culture. RNA sequencing analysis of the T cells revealed characteristic downregulation of effector T-cell-associated genes, but a lack of upregulation of memory T-cell-associated genes. The results of this study demonstrate that ASM cells can induce a phenotypic shift in CD4+ T cells into memory-like T cells but with reduced capacity for activation.

MAdCAM-1 targeting strategy can prevent colitic cancer carcinogenesis and progression via suppression of immune cell infiltration and inflammatory signals

Chronic inflammation caused by infiltrating immune cells can promote colitis-associated dysplasia/colitic cancer in ulcerative colitis (UC) by activating inflammatory cytokine signalling through the IL-6/p-STAT3 and TNFα/NF-κB pathways. Mucosal addressin cell adhesion molecule-1 (MAdCAM-1) expressed on high endothelial venules promotes the migration of immune cells from the bloodstream to the gut via interaction with α4β7 integrin expressed on the immune cells. MAdCAM-1, has therefore drawn interest as a novel therapeutic target for treating active UC. However, the role of MAdCAM-1-positive endothelial cells in immune cell infiltration in dysplasia/colitic cancers remains unclear. We evaluated the expression of MAdCAM-1, CD31 and immune cell markers (CD8, CD68, CD163 and FOXP3) in samples surgically resected from 11 UC patients with dysplasia/colitic cancer and 17 patients with sporadic colorectal cancer (SCRC), using immunohistochemical staining. We used an azoxymethane/dextran sodium sulphate mouse model (AOM/DSS mouse) to evaluate whether dysplasia/colitic cancer could be suppressed with an anti-MAdCAM-1 blocking antibody by preventing immune cell infiltration. The number of MAdCAM-1-positive vessels and infiltrating CD8+ , CD68+ and CD163+ immune cells was significantly higher in dysplasia/colitic cancer than in normal, SCRC and UC mucosa. In AOM/DSS mice, the anti-MAdCAM-1 antibody reduced the number, mean diameter, depth of tumours, Ki67 positivity, number of CD8+ , CD68+ and CD163+ immune cells and the IL-6/p-STAT3 and TNF-α/NF-κB signalling. Our results indicate that targeting MAdCAM-1 is a promising strategy for controlling not only UC severity but also carcinogenesis and tumour progression by regulating inflammation/immune cell infiltration in patients with UC.

Trichosanthin-derived peptide Tk-PQ attenuates immune rejection in mouse tracheal allotransplant model by suppressing PI3K-Akt and inducing type II immune polarization

Obliterative bronchiolitis (OB) is one of the main complications affecting long-term survival of post-lung transplantation patients. In this study, we evaluated the efficacy of Tk-PQ (a peptide derived from trichosanthin) in alleviating OB in a mouse ectopic tracheal transplant model. We found that post-transplantation treatment of Tk-PQ significant ameliorated OB symptoms including luminal occlusion, epithelial cells loss and fibrosis in the allograft. In addition, Tk-PQ promoted immune suppressive environment by inducing Th2 polarization and increasing Treg population which in turn led to elevated levels of anti-inflammatory cytokines IL-4, IL-10, IL-33 and decreased levels of pro-inflammatory IL-1β. Mechanistically, we used transcriptome analysis of splenic T cells from allografted mice to show that Tk-PQ treatment down-regulated the PI3K-Akt signaling pathway. Indeed, the immune suppression phenotypes of Tk-PQ was recapitulated by a PI3K inhibitor LY294002. Taken together, Tk-PQ regulates post-transplantation immuno-rejection by modulating the balance of T cell response via the PI3K-Akt pathway, making it a promising peptide based immune rejection suppressant for patients receiving allotransplant.

Renal tubular epithelial cells are constitutive non-cognate stimulators of resident T cells

Understanding the roles of different cell types in regulating T cell homeostasis in various tissues is critical for understanding adaptive immunity. Here, we show that RTECs (renal tubular epithelial cells) are intrinsically programmed to polyclonally stimulate proliferation of kidney αβ T cells by a cell-cell contact mechanism that is major histocompatibility complex (MHC) independent and regulated by CD155, αVβ3-integrin, and vitronectin. Peripheral CD4 and CD8 are resistant to RTEC-mediated stimulation, while the minor subset of double-negative (DN) T cells are responsive. This functional property of RTEC is discovered by using a coculture system that recapitulates spontaneous in vivo polyclonal proliferation of kidney T cells, which are mainly comprised of central memory T (TCM) and effector memory T (TEM) cells. This robust cell-intrinsic stimulatory role of RTECs could be underlying the steady-state spontaneous proliferation of kidney T cells. The results have conceptual implications for understanding roles of different cell types in regulating systemic and organ-specific T cell homeostasis.

T cells Use Focal Adhesions to Pull Themselves Through Confined Environments

Immune cells are highly dynamic and able to migrate through environments with diverse biochemical and mechanical composition. Their migration has classically been defined as amoeboid under the assumption that it is integrin-independent. Here we show that activated primary Th1 T cells require both confinement and extracellular matrix protein to migrate efficiently. This migration is mediated through small and dynamic focal adhesions that are composed of the same proteins associated with canonical mesenchymal focal adhesions, such as integrins, talin, and vinculin. These focal adhesions, furthermore, localize to sites of contractile traction stresses, enabling T cells to pull themselves through confined spaces. Finally, we show that Th1 T cell preferentially follows tracks of other T cells, suggesting that these adhesions are modifying the extracellular matrix to provide additional environmental guidance cues. These results demonstrate not only that the boundaries between amoeboid and mesenchymal migration modes are ambiguous, but that integrin-mediated adhesions play a key role in T cell motility.

AML/T cell interactomics uncover correlates of patient outcomes and the key role of ICAM1 in T cell killing of AML

T cells are important for the control of acute myeloid leukemia (AML), a common and often deadly malignancy. We observed that some AML patient samples are resistant to killing by human engineered cytotoxic CD4 + T cells. Single-cell RNA-seq of primary AML samples and CD4 + T cells before and after their interaction uncovered transcriptional programs that correlate with AML sensitivity or resistance to CD4 + T cell killing. Resistance-associated AML programs were enriched in AML patients with poor survival, and killing-resistant AML cells did not engage T cells in vitro . Killing-sensitive AML potently activated T cells before being killed, and upregulated ICAM1 , a key component of the immune synapse with T cells. Without ICAM1, killing-sensitive AML became resistant to killing to primary ex vivo -isolated CD8 + T cells in vitro , and engineered CD4 + T cells in vitro and in vivo . Thus, ICAM1 on AML acts as an immune trigger, allowing T cell killing, and could affect AML patient survival in vivo .

SIGNIFICANCE

AML is a common leukemia with sub-optimal outcomes. We show that AML transcriptional programs correlate with susceptibility to T cell killing. Killing resistance-associated AML programs are enriched in patients with poor survival. Killing-sensitive, but not resistant AML activate T cells and upregulate ICAM1 that binds to LFA-1 on T cells, allowing immune synapse formation which is critical for AML elimination.

GRAPHICAL ABSTRACT

A Wrinkle in TIME: How Changes in the Aging ECM Drive the Remodeling of the Tumor Immune Microenvironment

SUMMARY

Cancer is an age-related disease, with the majority of patients receiving their diagnosis after the age of 60 and most mortality from cancer occurring after this age. The tumor microenvironment changes drastically with age, which in turn affects cancer progression and treatment efficacy. Age-related changes to individual components of the microenvironment have received well-deserved attention over the past few decades, but the effects of aging at the interface of two or more microenvironmental components have been vastly understudied. In this perspective, we discuss the relationship between the aging extracellular matrix and the aging immune system, how they affect the tumor microenvironment, and how these multidisciplinary studies may open avenues for new therapeutics. Cancer is a disease of aging. With a rapidly aging population, we need to better understand the age-related changes that drive tumor progression, ranging from secreted changes to biophysical and immune changes.

Collagen VI deposition mediates stromal T cell trapping through inhibition of T cell motility in the prostate tumor microenvironment

The tumor extracellular matrix (ECM) is a barrier to anti-tumor immunity in solid tumors by disrupting T cell-tumor cell interaction underlying the need for elucidating mechanisms by which specific ECM proteins impact T cell motility and activity within the desmoplastic stroma of solid tumors. Here, we show that Collagen VI (Col VI) deposition correlates with stromal T cell density in human prostate cancer specimens. Furthermore, motility of CD4+ T cells is completely ablated on purified Col VI surfaces when compared with Fibronectin and Collagen I. Importantly, T cells adhered to Col VI surfaces displayed reduced cell spreading and fibrillar actin, indicating a reduction in traction force generation accompanied by a decrease in integrin β1 clustering. We found that CD4+ T cells largely lack expression of integrin α1 in the prostate tumor microenvironment and that blockade of α1β1 integrin heterodimers inhibited CD8+ T cell motility on prostate fibroblast-derived matrix, while re-expression of ITGA1 improved motility. Taken together, we show that the Col VI-rich microenvironment in prostate cancer reduces the motility of CD4+ T cells lacking integrin α1, leading to their accumulation in the stroma, thus putatively inhibiting anti-tumor T cell responses.

Engineering Tissue-Scale Properties with Synthetic Cells: Forging One from Many

In metazoans, living cells achieve capabilities beyond individual cell functionality by assembling into multicellular tissue structures. These higher-order structures represent dynamic, heterogeneous, and responsive systems that have evolved to regenerate and coordinate their actions over large distances. Recent advances in constructing micrometer-sized vesicles, or synthetic cells, now point to a future where construction of synthetic tissue can be pursued, a boon to pressing material needs in biomedical implants, drug delivery systems, adhesives, filters, and storage devices, among others. To fully realize the potential of synthetic tissue, inspiration has been and will continue to be drawn from new molecular findings on its natural counterpart. In this review, we describe advances in introducing tissue-scale features into synthetic cell assemblies. Beyond mere complexation, synthetic cells have been fashioned with a variety of natural and engineered molecular components that serve as initial steps toward morphological control and patterning, intercellular communication, replication, and responsiveness in synthetic tissue. Particular attention has been paid to the dynamics, spatial constraints, and mechanical strengths of interactions that drive the synthesis of this next-generation material, describing how multiple synthetic cells can act as one.

Integrins and the Metastasis-like Dissemination of Acute Lymphoblastic Leukemia to the Central Nervous System

Acute lymphoblastic leukemia (ALL) disseminates with high prevalence to the central nervous system (CNS) in a process resembling aspects of the CNS surveillance of normal immune cells as well as aspects of brain metastasis from solid cancers. Importantly, inside the CNS, the ALL blasts are typically confined within the cerebrospinal fluid (CSF)-filled cavities of the subarachnoid space, which they use as a sanctuary protected from both chemotherapy and immune cells. At present, high cumulative doses of intrathecal chemotherapy are administered to patients, but this is associated with neurotoxicity and CNS relapse still occurs. Thus, it is imperative to identify markers and novel therapy targets specific to CNS ALL. Integrins represent a family of adhesion molecules involved in cell-cell and cell-matrix interactions, implicated in the adhesion and migration of metastatic cancer cells, normal immune cells, and leukemic blasts. The ability of integrins to also facilitate cell-adhesion mediated drug resistance, combined with recent discoveries of integrin-dependent routes of leukemic cells into the CNS, have sparked a renewed interest in integrins as markers and therapeutic targets in CNS leukemia. Here, we review the roles of integrins in CNS surveillance by normal lymphocytes, dissemination to the CNS by ALL cells, and brain metastasis from solid cancers. Furthermore, we discuss whether ALL dissemination to the CNS abides by known hallmarks of metastasis, and the potential roles of integrins in this context.

Anti-Inflammatories in the Treatment of Dry Eye Disease: A Review

Inflammation is an important driver of dry eye disease (DED) pathogenesis. An initial insult that results in the loss of tear film homeostasis can initiate a nonspecific innate immune response that leads to a chronic and self-sustaining inflammation of the ocular surface, which results in classic symptoms of dry eye. This initial response is followed by a more prolonged adaptive immune response, which can perpetuate and aggravate inflammation and result in a vicious cycle of chronic inflammatory DED. Effective anti-inflammatory therapies can help patients exit this cycle, and effective diagnosis of inflammatory DED and selection of the most appropriate treatment are therefore key to successful DED management and treatment. This review explores the cellular and molecular mechanisms of the immune and inflammatory components of DED, and examines the evidence base for the use of currently available topical treatment options. These agents include topical steroid therapy, calcineurin inhibitors, T cell integrin antagonists, antibiotics, autologous serum/plasma therapy, and omega-3 fatty acid dietary supplements.

Polymer- and lipid-based gene delivery technology for CAR T cell therapy

Chimeric antigen receptor T cell (CAR T cell) therapy is a revolutionary approach approved by the FDA and EMA to treat B cell malignancies and multiple myeloma. The production of these T cells has been done through viral vectors, which come with safety concerns, high cost and production challenges, and more recently also through electroporation, which can be extremely cytotoxic. In this context, nanosystems can constitute an alternative to overcome the challenges associated with current methods, resulting in a safe and cost-effective platform. However, the barriers associated with T cells transfection show that the design and engineering of novel approaches in this field are highly imperative. Here, we present an overview from CAR constitution to transfection technologies used in T cells, highlighting the lipid- and polymer-based nanoparticles as a potential delivery platform. Specifically, we provide examples, strengths and weaknesses of nanosystem formulations, and advances in nanoparticle design to improve transfection of T cells. This review will guide the researchers in the design and development of novel nanosystems for next-generation CAR T therapeutics.

Integrins are double-edged swords in pulmonary infectious diseases

Integrins are an important family of adhesion molecules that are widely distributed on immune cells in the lungs. Of note, accumulating evidences have shown that integrins are double-edged swords in pulmonary infectious diseases. On one hand, integrins promote the migration of immune cells to remove the invaded pathogens in the infected lungs. However, on the other hand, integrins also act as the targets for pathogens to escape from host immune system, which is a potential factor leading to further tissue damage. Thus, the innovative therapeutic strategies based on integrins has inspired well-founded hopes to treat pulmonary infectious diseases. In this review, we illustrate the involvement of integrins in pulmonary infectious diseases, and further discuss the innovative therapeutic targets based on integrins.

The complex relationship between integrins and oncolytic herpes Simplex Virus 1 in high-grade glioma therapeutics

High-grade gliomas (HGGs) are lethal central nervous system tumors that spread quickly through the brain, making treatment challenging. Integrins are transmembrane receptors that mediate cell-extracellular matrix (ECM) interactions, cellular adhesion, migration, growth, and survival. Their upregulation and inverse correlation in HGG malignancy make targeting integrins a viable therapeutic option. Integrins also play a role in herpes simplex virus 1 (HSV-1) entry. Oncolytic HSV-1 (oHSV) is the most clinically advanced oncolytic virotherapy, showing a superior safety and efficacy profile over standard cancer treatment of solid cancers, including HGG. With the FDA-approval of oHSV for melanoma and the recent conditional approval of oHSV for malignant glioma in Japan, usage of oHSV for HGG has become of great interest. In this review, we provide a systematic overview of the role of integrins in relation to oHSV, with a special focus on its therapeutic potential against HGG. We discuss the pros and cons of targeting integrins during oHSV therapy: while integrins play a pro-therapeutic role by acting as a gateway for oHSV entry, they also mediate the innate antiviral immune responses that hinder oHSV therapeutic efficacy. We further discuss alternative strategies to regulate the dual functionality of integrins in the context of oHSV therapy.

Characterising Distinct Migratory Profiles of Infiltrating T-Cell Subsets in Human Glioblastoma

Glioblastoma is the most common and aggressive form of primary brain cancer, with no improvements in the 5-year survival rate of 4.6% over the past three decades. T-cell-based immunotherapies such as immune-checkpoint inhibitors and chimeric antigen receptor T-cell therapy have prolonged the survival of patients with other cancers and have undergone early-phase clinical evaluation in glioblastoma patients. However, a major challenge for T-cell-based immunotherapy of glioblastoma and other solid cancers is T-cell infiltration into tumours. This process is mediated by chemokine-chemokine receptor and integrin-adhesion molecule interactions, yet the specific nature of the molecules that may facilitate T-cell homing into glioblastoma are unknown. Here, we have characterised chemokine receptor and integrin expression profiles of endogenous glioblastoma-infiltrating T cells, and the chemokine expression profile of glioblastoma-associated cells, by single-cell RNA-sequencing. Subsequently, chemokine receptors and integrins were validated at the protein level to reveal enrichment of receptors CCR2, CCR5, CXCR3, CXCR4, CXCR6, CD49a, and CD49d in glioblastoma-infiltrating T-cell populations relative to T cells in matched patient peripheral blood. Complementary chemokine ligand expression was then validated in glioblastoma biopsies and glioblastoma-derived primary cell cultures. Together, enriched expression of homing receptor-ligand pairs identified in this study implicate a potential role in mediating T-cell infiltration into glioblastoma. Importantly, our data characterising the migratory receptors on endogenous tumour-infiltrating T cells could be exploited to enhance the tumour-homing properties of future T-cell immunotherapies for glioblastoma.

Vitronectin-derived bioactive peptide prevents spondyloarthritis by modulating Th17/Treg imbalance in mice with curdlan-induced spondyloarthritis

Purpose

Spondyloarthritis (SpA) is a systemic inflammatory arthritis mediated mainly by interleukin (IL)-17. The vitronectin-derived bioactive peptide, VnP-16, exerts an anti-osteoporotic effect via β1 and αvβ3 integrin signaling. SpA is associated with an increased risk of osteoporosis, and we investigated the effect of VnP-16 in mice with SpA.

Methods

SpA was induced by curdlan in SKG ZAP-70^W163C mice, which were treated with vehicle, celecoxib, VnP-16, or VnP-16+celecoxib. The clinical score, arthritis score, spondylitis score, and proinflammatory cytokine expression of the spine were evaluated by immunohistochemical staining. Type 17 helper T cell (Th17) and regulatory T cell (Treg) differentiation in the spleen was evaluated by flow cytometry and in the spine by confocal staining. Splenocyte expression of signal transducer and activator of transcription (STAT) 3 and pSTAT3 was evaluated by in vitro Western blotting.

Results

The clinical score was significantly reduced in the VnP16+celecoxib group. The arthritis and spondylitis scores were significantly lower in the VnP-16 and VnP16+celecoxib groups than the vehicle group. In the spine, the levels of IL-1β, IL-6, tumor necrosis factor-α, and IL-17 expression were reduced and Th17/Treg imbalance was regulated in the VnP-16 alone and VnP-16+celecoxib groups. Flow cytometry of splenocytes showed increased polarization of Tregs in the VnP-16+celecoxib group. In vitro, VnP-16 suppressed pSTAT3.

Conclusions

VnP-16 plus celecoxib prevented SpA progression in a mouse model by regulating the Th17/Treg imbalance and suppressing the expression of proinflammatory cytokines.

Potential therapies for immune-related adverse events associated with immune checkpoint inhibition: from monoclonal antibodies to kinase inhibition

The therapeutic benefits of immune checkpoint inhibitors (ICIs), which enable antitumor immune responses, can be tempered by unwanted immune-related adverse events (irAEs). Treatment recommendations stratified by irAE phenotype and immunohistopathological findings have only recently been proposed and are often based on those used in primary autoimmune diseases, including targeting of specific proinflammatory cytokines with monoclonal antibodies. Increasing evidence supports the use of such antibody-based strategies as effective steroid-sparing treatments, although the therapies themselves may be associated with additional drug toxicities and reduced ICI efficacy. Kinases are key contributors to the adaptive and innate responses that drive primary autoimmune diseases and irAEs. The janus kinase/signal transducer and activator of transcription, Bruton’s tyrosine kinase, and mitogen-activated protein kinase-interacting serine/threonine protein kinases 1 and 2 pathways are also critical to tumor progression and have important roles in cells of the tumor microenvironment. Herein, we review the histopathological, biological, and clinical evidence to support specific monoclonal antibodies and kinase inhibition as management strategies for irAEs.

The endothelial diapedesis synapse regulates transcellular migration of human T lymphocytes in a CX3CL1- and SNAP23-dependent manner

Understanding how cytotoxic T lymphocytes (CTLs) efficiently leave the circulation to target cancer cells or contribute to inflammation is of high medical interest. Here, we demonstrate that human central memory CTLs cross the endothelium in a predominantly paracellular fashion, whereas effector and effector memory CTLs cross the endothelium preferably in a transcellular fashion. We find that effector CTLs show a round morphology upon adhesion and induce a synapse-like interaction with the endothelium where ICAM-1 is distributed at the periphery. Moreover, the interaction of ICAM-1:β2integrin and endothelial-derived CX3CL1:CX3CR1 enables transcellular migration. Mechanistically, we find that ICAM-1 clustering recruits the SNARE-family protein SNAP23, as well as syntaxin-3 and -4, for the local release of endothelial-derived chemokines like CXCL1/8/10. In line, silencing of endothelial SNAP23 drives CTLs across the endothelium in a paracellular fashion. In conclusion, our data suggest that CTLs trigger local chemokine release from the endothelium through ICAM-1-driven signals driving transcellular migration.

Current Advances in Mechanisms and Treatment of Dry Eye Disease: Toward Anti-inflammatory and Immunomodulatory Therapy and Traditional Chinese Medicine

Dry eye is currently one of the most common ocular surface disease. It can lead to ocular discomfort and even cause visual impairment, which greatly affects the work and quality of life of patients. With the increasing incidence of dry eye disease (DED) in recent years, the disease is receiving more and more attention, and has become one of the hot research fields in ophthalmology research. Recently, with the in-depth research on the etiology, pathogenesis and treatment of DED, it has been shown that defects in immune regulation is one of the main pathological mechanisms of DED. Since the non-specific and specific immune response of the ocular surface are jointly regulated, a variety of immune cells and inflammatory factors are involved in the development of DED. The conventional treatment of DED is the application of artificial tears for lubricating the ocular surface. However, for moderate-to-severe DED, treatment with anti-inflammatory drugs is necessary. In this review, the immunomodulatory mechanisms of DED and the latest research progress of its related treatments including Chinese medicine will be discussed.

Autoimmune regulator act in synergism with thymocyte adhesion in the control of lncRNAs in medullary thymic epithelial cells

The autoimmune regulator (Aire) gene in medullary thymic epithelial cells (mTECs) encodes the AIRE protein, which interacts with its partners within the nucleus. This "Aire complex" induces stalled RNA Pol II on chromatin to proceed with transcription elongation of a large set of messenger RNAs and microRNAs. Considering that RNA Pol II also transcribes long noncoding RNAs (lncRNAs), we hypothesized that Aire might be implicated in the upstream control of this RNA species. To test this, we employed a loss-of-function approach in which Aire knockout mTECs were compared to Aire wild-type mTECs for lncRNA transcriptional profiling both in vitro and in vivo model systems. RNA sequencing enables the differential expression profiling of lncRNAs when these cells adhere in vitro to thymocytes or do not adhere to them as a way to test the effect of cell adhesion. Sets of lncRNAs that are unique and that are shared in vitro and in vivo were identified. Among these, we found the Aire-dependent lncRNAs as for example, Platr28, Ifi30, Morrbid, Malat1, and Xist. This finding represents the first evidence that Aire mediates the transcription of lncRNAs in mTECs. Microarray hybridizations enabled us to observe that temporal thymocyte adhesion modulates the expression levels of such lncRNAs as Morrbid, Xist, and Fbxl12o after 36 h of adhesion. This finding shows the existence of a synergistic mechanism involving a link between thymocyte adhesion, Aire, and lncRNAs in mTECs that might be important for immune self-representation.

Use of a small molecule integrin activator as a systemically administered vaccine adjuvant in controlling Chagas disease

The development of suitable safe adjuvants to enhance appropriate antigen-driven immune responses remains a challenge. Here we describe the adjuvant properties of a small molecule activator of the integrins αLβ2 and α4β1, named 7HP349, which can be safely delivered systemically independent of antigen. 7HP349 directly activates integrin cell adhesion receptors crucial for the generation of an immune response. When delivered systemically in a model of Chagas disease following immunization with a DNA subunit vaccine encoding candidate T. cruzi antigens, TcG2 and TcG4, 7HP349 enhanced the vaccine efficacy in both prophylactic and therapeutic settings. In a prophylactic setting, mice immunized with 7HP349 adjuvanted vaccine exhibited significantly improved control of acute parasite burden in cardiac and skeletal muscle as compared to vaccination alone. When administered with vaccine therapeutically, parasite burden was again decreased, with the greatest adjuvant effect of 7HP349 being noted in skeletal muscle. In both settings, adjuvantation with 7HP349 was effective in decreasing pathological inflammatory infiltrate, improving the integrity of tissue, and controlling tissue fibrosis in the heart and skeletal muscle of acutely and chronically infected Chagas mice. The positive effects correlated with increased splenic frequencies of CD8⁺T effector cells and an increase in the production of IFN-γ and cytolytic molecules (perforin and granzyme) by the CD4⁺ and CD8⁺ effector and central memory subsets in response to challenge infection. This demonstrates that 7HP349 can serve as a systemically administered adjuvant to enhance T cell-mediated immune responses to vaccines. This approach could be applied to numerous vaccines with no reformulation of existing stockpiles.

Emerging Treatment Options in Inflammatory Bowel Disease: Janus Kinases, Stem Cells, and More

BACKGROUND

Treatment of inflammatory bowel diseases (IBD) has tremendously improved during the last 20 years; however, a substantial fraction of patients does not respond to available therapies or lose response, and new strategies are needed.

SUMMARY

Two pharmacological principles have been successfully used for IBD treatment: inhibition of cellular signaling and interference with leukocyte trafficking. Besides tumor necrosis factor, interleukin (IL)-23 is a promising drug target, and antibodies for the combined inhibition of IL-23 and IL-12 (ustekinumab and briakinumab) or selective IL-23 inhibition (brazikumab, risankizumab, and mirikizumab) seem to be effective in Crohn's disease (CD) with emerging evidence also for ulcerative colitis (UC). Janus kinase (JAK) mediates intracellular signaling of a large number of cytokines. Tofacitinib is the first JAK inhibitor approved for UC, and the JAK inhibitors filgotinib and upadacitinib showed potential in CD. Leukocyte trafficking can be inhibited by interference with lymphocyte integrin-α4β7 or endothelial MadCAM-1. The α4β7 integrin inhibitor vedolizumab is an established treatment in IBD, and long-term data of pivotal studies are now available. Additional molecules with therapeutic potential are α4β7-specific abrilumab, β7-specific etrolizumab, and the α4-specific small molecule AJM300. PF-00547659, an antibody against endothelial MadCAM-1, also showed therapeutic potential in UC. Modulation of sphingosine-1-phosphate receptor (S1PR) activity is necessary for the egress of lymphocytes into the circulation, and S1PR modulation results in lymphocyte trapping in lymphatic organs. Ozanimod, an S1PR1 and S1PR5 inhibitor, has been successfully tested in initial studies in UC. Mesenchymal stem cell therapy has been approved for the treatment of complex, active CD fistula, and mesenchymal stem cell therapy might be a paradigm shift for this condition. Autologous stem cell transplantation (ASCT) has been successfully used in CD case series; however, in a randomized trial, a highly stringent endpoint was not met. However, considering positive effects in secondary endpoints, ASCT might be a future treatment of last resort in severe, refractory CD cases, provided that safer protocols can be provided. Key messages: New IBD treatments are successful for a significant fraction of patients. However, new strategies for patient selection, treatment combinations, and/or additional therapies must be developed to serve the need of all IBD patients.

Repurposing a novel anti-cancer RXR agonist to attenuate murine acute GVHD and maintain graft-versus-leukemia responses

The nuclear receptor (NR) subclass, retinoid X receptors (RXRs), exert immunomodulatory functions that control inflammation and metabolism via homodimers and heterodimers, with several other NRs, including retinoic acid receptors. IRX4204 is a novel, highly specific RXR agonist in clinical trials that potently and selectively activates RXR homodimers, but not heterodimers. In this study, in vivo IRX4204 compared favorably with FK506 in abrogating acute graft-versus-host disease (GVHD), which was associated with inhibiting allogeneic donor T-cell proliferation, reducing T-helper 1 differentiation, and promoting regulatory T-cell (Treg) generation. Recipient IRX4204 treatment reduced intestinal injury and decreased IFN-γ and TNF-α serum levels. Transcriptional analysis of donor T cells isolated from intestines of GVHD mice treated with IRX4204 revealed significant decreases in transcripts regulating proinflammatory pathways. In vitro, inducible Treg differentiation from naive CD4+ T cells was enhanced by IRX4204. In vivo, IRX4204 increased the conversion of donor Foxp3- T cells into peripheral Foxp3+ Tregs in GVHD mice. Using Foxp3 lineage-tracer mice in which both the origin and current FoxP3 expression of Tregs can be tracked, we demonstrated that IRX4204 supports Treg stability. Despite favoring Tregs and reducing Th1 differentiation, IRX4204-treated recipients maintained graft-versus-leukemia responses against both leukemia and lymphoma cells. Notably, IRX4204 reduced in vitro human T-cell proliferation and enhanced Treg generation in mixed lymphocyte reaction cultures. Collectively, these beneficial effects indicate that targeting RXRs with IRX4204 could be a novel approach to preventing acute GVHD in the clinic.

Three-Dimensional Culture Models to Study Innate Anti-Tumor Immune Response: Advantages and Disadvantages

Several approaches have shown that the immune response against tumors strongly affects patients' clinical outcome. Thus, the study of anti-tumor immunity is critical to understand and potentiate the mechanisms underlying the elimination of tumor cells. Natural killer (NK) cells are members of innate immunity and represent powerful anti-tumor effectors, able to eliminate tumor cells without a previous sensitization. Thus, the study of their involvement in anti-tumor responses is critical for clinical translation. This analysis has been performed in vitro, co-incubating NK with tumor cells and quantifying the cytotoxic activity of NK cells. In vivo confirmation has been applied to overcome the limits of in vitro testing, however, the innate immunity of mice and humans is different, leading to discrepancies. Different activating receptors on NK cells and counter-ligands on tumor cells are involved in the antitumor response, and innate immunity is strictly dependent on the specific microenvironment where it takes place. Thus, three-dimensional (3D) culture systems, where NK and tumor cells can interact in a tissue-like architecture, have been created. For example, tumor cell spheroids and primary organoids derived from several tumor types, have been used so far to analyze innate immune response, replacing animal models. Herein, we briefly introduce NK cells and analyze and discuss in detail the properties of 3D tumor culture systems and their use for the study of tumor cell interactions with NK cells.

Acquisition of New Migratory Properties by Highly Differentiated CD4+CD28null T Lymphocytes in Rheumatoid Arthritis Disease

Expanded CD4+CD28^null T lymphocytes are found in the tissues and peripheral blood of patients with many autoimmune diseases, such as rheumatoid arthritis (RA). These highly differentiated cells present potent inflammatory activity and capability to induce tissue destruction, which has been suggested to predispose to the development of more aggressive disease. In fact, preferential migration to inflammatory sites has been proposed to be a contributing factor in the progression of autoimmune and cardiovascular diseases frequently found in these patients. The functional activity of CD4+CD28^null T lymphocytes is largely dependent on interleukin 15 (IL-15), and this cytokine may also act as a selective attractor of these cells to local inflammatory infiltrates in damaged tissues. We have analysed, in RA patients, the migratory properties and transcriptional motility profile of CD4+CD28^null T lymphocytes compared to their counterparts CD28+ T lymphocytes and the enhancing role of IL-15. Identification of the pathways involved in this process will allow us to design strategies directed to block effector functions that CD4+CD28^null T lymphocytes have in the target tissue, which may represent therapeutic approaches in this immune disorder.

The molecular basis and cellular effects of distinct CD103 expression on CD4 and CD8 T cells

Integrin CD103 mediates the adhesion and tissue retention of T cells by binding to E-cadherin which is abundant on epithelial cells. Notably, CD103 is highly expressed on CD8 T cells but conspicuously absent on most CD4 T cells. The mechanism controlling such lineage-specific expression of CD103 remains unclear. Using a series of genetically engineered mouse models, here, we demonstrate that the regulatory mechanism of CD103 expression is distinct between CD4 and CD8 T cells, and that the transcription factor Runx3 plays an important but not an essential role in this process. We further found that the availability of integrin β7 which heterodimerizes with CD103 was necessary but also constrained the surface expression of CD103. Notably, the forced surface expression of CD103 did not significantly alter the thymic development of conventional T cells but severely impaired the generation of MHC-II-restricted TCR transgenic T cells, revealing previously unappreciated aspects of CD103 in the selection and maturation of CD4 T cells. Unlike its effect on CD4 T cell development, however, CD103 overexpression did not significantly affect CD4 T cells in peripheral tissues. Moreover, the frequency and number of CD4 T cells in the small intestine epithelium did not increase even though E-cadherin is highly expressed in this tissue. Collectively, these results suggest that most mature CD4 T cells are refractory to the effects of CD103 expression, and that they presumably utilize CD103-independent pathways to control their tissue retention and residency.

Interactions via α2β1 Cell Integrin May Protect against the Progression of Airway Structural Changes in Asthma

Increased airway wall thickness and remodeling of bronchial mucosa are characteristic of asthma and may arise from altered integrin signaling on airway cells. Here, we analyzed the expression of β₁-subfamily integrins on blood and airway cells (flow cytometry), inflammatory biomarkers in serum and bronchoalveolar lavage, reticular basement membrane (RBM) thickness and collagen deposits in the mucosa (histology), and airway geometry (CT-imaging) in 92 asthma patients (persistent airflow limitation subtype: n = 47) and 36 controls. Persistent airflow limitation was associated with type-2 inflammation, elevated soluble α₂ integrin chain, and changes in the bronchial wall geometry. Both subtypes of asthma showed thicker RBM than control, but collagen deposition and epithelial α₁ and α₂ integrins staining were similar. Type-I collagen accumulation and RBM thickness were inversely related to the epithelial expression of the α₂ integrin chain. Expression of α₂β₁ integrin on T-cells and eosinophils was not altered in asthma. Collagen I deposits were, however, more abundant in patients with lower α₂β₁ integrin on blood and airway CD8⁺ T-cells. Thicker airway walls in CT were associated with lower α₂ integrin chain on blood CD4⁺ T-cells and airway eosinophils. Our data suggest that α₂β₁ integrin on inflammatory and epithelial cells may protect against airway remodeling advancement in asthma.

Differentiation syndrome with lower-intensity treatments for acute myeloid leukemia

Differentiation Syndrome (DS) has been identified in a subset of patients undergoing treatment with novel classes of differentiating therapies for acute myeloid leukemia (AML) such as IDH and FLT3 inhibitors. While DS is a well-known treatment-related complication in acute promyelocytic leukemia (APL), efforts are still ongoing to standardize diagnostic and treatment parameters for DS in AML. Though the rates of incidence vary, many of the signs and symptoms of DS are common between APL and AML. So, DS can lead to fatal complications in AML, but prompt management is usually effective and rarely necessitates interruption or discontinuation of AML therapy.

Understanding T cell phenotype for the design of effective chimeric antigen receptor T cell therapies

Rapid advances in immunotherapy have identified adoptive cell transfer as one of the most promising approaches for the treatment of cancers. Large numbers of cancer reactive T lymphocytes can be generated ex vivo from patient blood by genetic modification to express chimeric antigen receptors (CAR) specific for tumor-associated antigens. CAR T cells can respond strongly against cancer cells, and adoptive transferred CAR T cells can induce dramatic responses against certain types of cancers. The ability of T cells to respond against disease depends on their ability to localize to sites, persist and exert functions, often in an immunosuppressive microenvironment, and these abilities are reflected in their phenotypes. There is currently intense interest in generating CAR T cells possessing the ideal phenotypes to confer optimal antitumor activity. In this article, we review T cell phenotypes for trafficking, persistence and function, and discuss how culture conditions and genetic makeups can be manipulated to achieve the ideal phenotypes for antitumor activities.

Dysregulation of leukocyte trafficking in ageing: Causal factors and possible corrective therapies

Ageing is a universal biological phenomenon that is accompanied by the development of chronic, low-grade inflammation and remodelling of the immune system resulting in compromised immune function. In this review, we explore how the trafficking of innate and adaptive immune cells under homeostatic and inflammatory conditions is dysregulated in ageing. We particularly highlight the age-related changes in the expression of adhesion molecules and chemokine receptor/ligands, and the accumulation of senescent cells that drive modulated leukocyte trafficking. These age-related changes to leukocyte trafficking are multifactorial and specific to leukocyte subset, tissue, type of vascular bed, and inflammatory status. However, dysregulated leukocyte trafficking ultimately affects immune responses in older adults. We therefore go on to discuss approved drugs, including anti-integrins, anti-chemokines and statins, as well as novel therapeutics that may be used to target dysregulated leukocyte trafficking in ageing, improve immune responses and delay the onset of age-related diseases.

CD40/CD40L and Related Signaling Pathways in Cardiovascular Health and Disease-The Pros and Cons for Cardioprotection

The CD40-CD40 ligand (CD40L) dyad represents a scientific and clinical field that has raised many controversies in the past and cannot be clearly defined as being an either beneficial or harmful pathway. Being crucially involved in physiological immunological processes as well as pathological inflammatory reactions, the signaling pathway has been recognized as a key player in the development of both autoimmune and cardiovascular disease. Even though the possibilities of a therapeutic approach to the dyad were recognized decades ago, due to unfortunate events, detailed in this review, pharmacological treatment targeting the dyad, especially in patients suffering from atherosclerosis, is not available. Despite the recent advances in the treatment of classical cardiovascular risk factors, such as arterial hypertension and diabetes mellitus, the treatment of the associated low-grade inflammation that accounts for the progression of atherosclerosis is still challenging. Low-grade inflammation can be detected in a significant portion of patients that suffer from cardiovascular disease and it is therefore imperative to develop new therapeutic strategies in order to combat this driver of atherosclerosis. Of note, established cardiovascular drugs such as angiotensin-converting enzyme inhibitors or statins have proven beneficial cardiovascular effects that are also related to their pleiotropic immunomodulatory properties. In this review, we will discuss the setbacks encountered as well as new avenues discovered on the path to a different, inflammation-centered approach for the treatment of cardiovascular disease with the CD40-CD40L axis as a central therapeutic target.

Nicotine Changes the microRNA Profile to Regulate the FOXO Memory Program of CD8+ T Cells in Rheumatoid Arthritis

Objective: Smoking suppresses PD-1 expression in patients with rheumatoid arthritis (RA). In this study, we assess if smoking changed the epigenetic control over CD8⁺ T cell memory formation through a microRNA (miR) dependent mechanism.

Methods: Phenotypes of CD8⁺ T cells from smokers and non-smokers, RA and healthy, were analyzed by flow cytometry. A microarray analysis was used to screen for differences in miR expression. Sorted CD8⁺ cells were in vitro stimulated with nicotine and analyzed for transcription of miRs and genes related to memory programming by qPCR.

Results: CD27⁺CD107a⁻CD8⁺ T cells, defining a naïve-memory population, had low expression of PD-1. Additionally, the CD27⁺ population was more frequent in smokers (p = 0.0089). Smokers were recognized by differential expression of eight miRs. Let-7c-5p, let-7d-5p and let-7e-5p, miR-92a-3p, miR-150-5p, and miR-181-5p were up regulated, while miR-3196 and miR-4723-5p were down regulated. These miRs were predicted to target proteins within the FOXO-signaling pathway involved in CD8⁺ memory programming. Furthermore, miR-92a-3p was differentially expressed in CD8⁺ cells with naïve-memory predominance. Nicotine exposure of CD8⁺ cells induced the expression of miR-150-5p and miR-181a-5p in the naïve-memory cells in vitro. Additionally, nicotine exposure inverted the ratio between mRNAs of proteins in the FOXO pathway and their targeting miRs.

Conclusions: Smokers have a high prevalence of CD8⁺ T cells with a naïve-memory phenotype. These cells express a miR profile that interacts with the memory programming conducted through the FOXO pathway.

Anti-αLβ2 antibodies reveal novel endocytotic cross-modulatory functionality

BACKGROUND AND PURPOSE

Antibodies targeting cell surface receptors are considered to enable highly selective therapeutic interventions for immune disorders and cancer. Their biological profiles are found, generally, to represent the net effects of antibody-target interactions. The former therapeutic anti-integrin αLβ2 antibody efalizumab seems to defeat this paradigm by eliciting, via mechanisms currently unknown, much broader effects than would be predicted based on its target specificity.

EXPERIMENTAL APPROACH

To elucidate the mechanisms behind these broad effects, we investigated in primary human lymphocytes in vitro the effects of anti-αLβ2 antibodies on the expression of αLβ2 as well as unrelated α4 integrins, in comparison to Fab fragments and small-molecule inhibitors.

KEY RESULTS

We demonstrate that anti-αLβ2 mAbs directly induce the internalization of α4 integrins. The endocytotic phenomenon is a direct consequence of their antibody nature. It is inhibited when monovalent Fab fragments or small-molecule inhibitors are used. It is independent of crosslinking via anti-Fc mAbs and of αLβ2 activation. The cross-modulatory effect is unidirectional and not observed in a similar fashion with the α4 integrin antibody natalizumab.

CONCLUSION AND IMPLICATIONS

The present study identifies endocytotic cross-modulation as a hitherto unknown non-canonical functionality of anti-αLβ2 antibodies. This cross-modulation has the potential to fundamentally alter an antibody's benefit risk profile, as evident with efalizumab. The newly described phenomenon may be of relevance to other therapeutic antibodies targeting cluster-forming receptors. Thus, pharmacologists should be cognizant of this action when investigating such antibodies.

Integrin-Mediated Adhesion and Chemoresistance of Acute Lymphoblastic Leukemia Cells Residing in the Bone Marrow or the Central Nervous System

Acute Lymphoblastic Leukemia (ALL) is the most common cancer in childhood. Despite a significantly improved prognosis over the last decade with a 5-years survival rate of ~90%, treatment-related morbidity remains substantial and relapse occurs in 10–15% of patients (1). The most common site of relapse is the bone marrow, but early colonization and subsequent reoccurrence of the disease in the central nervous system (CNS) also occurs. Integrins are a family of cell surface molecules with a longstanding history in cancer cell adherence, migration and metastasis. In chronic lymphoblastic leukemia (CLL), the VLA-4 integrin has been acknowledged as a prognostic marker and mounting evidence indicates that this and other integrins may also play a role in acute leukemia, including ALL. Importantly, integrins engage in anti-apoptotic signaling when binding extracellular molecules that are enriched in the bone marrow and CNS microenvironments. Here, we review the current evidence for a role of integrins in the adherence of ALL cells within the bone marrow and their colonization of the CNS, with particular emphasis on mechanisms adding to cancer cell survival and chemoresistance.

Can gut microbiota of men who have sex with men influence HIV transmission?

Gaining a complete understanding of transmission risk factors will assist in efforts to reduce new HIV infections, especially within the disproportionally affected population of men who have sex with men (MSM). We recently reported that the fecal microbiota of MSM elevates immune activation in gnotobiotic mice and enhances HIV infection in vitro over that of fecal microbiota from men who have sex with women. We also demonstrated elevation of the gut homing marker CD103 (integrin αE) on CD4⁺ T cells by MSM-microbiota. Here we provide additional evidence that the gut microbiota is a risk factor for HIV transmission in MSM by showing elevated frequencies of the HIV co-receptor CCR5 on CD4⁺ T cells in human rectosigmoid colon biopsies. We discuss our interest in specific MSM-associated bacteria and propose the influx of CD103⁺ and CCR5⁺ CD4⁺ T cells into the colon as a potential link between the MSM microbiota and HIV transmission.

The Immunological Basis of Dry Eye Disease and Current Topical Treatment Options

Homeostasis of the lacrimal functional unit is needed to ensure a well-regulated ocular immune response comprising innate and adaptive phases. When the ocular immune system is excessively stimulated and/or immunoregulatory mechanisms are disrupted, the balance between innate and adaptive phases is dysregulated and chronic ocular surface inflammation can result, leading to chronic dry eye disease (DED). According to the Tear Film and Ocular Surface Society Dry Eye Workshop II definition, DED is a multifactorial disorder of the ocular surface characterized by impairment and loss of tear homeostasis (hyperosmolarity), ocular discomfort or pain, and neurosensory abnormalities. Dysregulated ocular immune responses result in ocular surface damage, which is a further contributing factor to DED pathology. Several therapeutics are available to break the vicious circle of DED and prevent chronic disease and progression, including immunosuppressive agents (steroids) and immunomodulators (cyclosporine and lifitegrast). Given the chronic inflammatory nature of DED, each of these agents is commonly used in clinical practice. In this study, we review the immunopathology of DED and the molecular and cellular actions of current topical DED therapeutics to inform clinical decision making.

VLA-4 Expression and Activation in B Cell Malignancies: Functional and Clinical Aspects

Lineage commitment and differentiation of hematopoietic cells takes place in well-defined microenvironmental surroundings. Communication with other cell types is a vital prerequisite for the normal functions of the immune system, while disturbances in this communication support the development and progression of neoplastic disease. Integrins such as the integrin very late antigen-4 (VLA-4; CD49d/CD29) control the localization of healthy as well as malignant B cells within the tissue, and thus determine the patterns of organ infiltration. Malignant B cells retain some key characteristics of their normal counterparts, with B cell receptor (BCR) signaling and integrin-mediated adhesion being essential mediators of tumor cell homing, survival and proliferation. It is thus not surprising that targeting the BCR pathway using small molecule inhibitors has proved highly effective in the treatment of B cell malignancies. Attenuation of BCR-dependent lymphoma–microenvironment interactions was, in this regard, described as a main mechanism critically contributing to the efficacy of these agents. Here, we review the contribution of VLA-4 to normal B cell differentiation on the one hand, and to the pathophysiology of B cell malignancies on the other hand. We describe its impact as a prognostic marker, its interplay with BCR signaling and its predictive role for novel BCR-targeting therapies, in chronic lymphocytic leukemia and beyond.

Zika virus targets the human thymic epithelium

Previous work showed that the thymus can be infected by RNA viruses as HIV and HTLV-1. We thus hypothesized that the thymus might also be infected by the Zika virus (ZIKV). Herein we provide compelling evidence that ZIKV targets human thymic epithelial cells (TEC) in vivo and in vitro. ZIKV-infection enhances keratinization of TEC, with a decrease in proliferation and increase in cell death. Moreover, ZIKV modulates a high amount of coding RNAs with upregulation of genes related to cell adhesion and migration, as well as non-coding genes including miRNAs, circRNAs and lncRNAs. Moreover, we observed enhanced attachment of lymphoblastic T-cells to infected TEC, as well as virus transfer to those cells. Lastly, alterations in thymuses from babies congenitally infected were seen, with the presence of viral envelope protein in TEC. Taken together, our data reveals that the thymus, particularly the thymic epithelium, is a target for the ZIKV with changes in the expression of molecules that are relevant for interactions with developing thymocytes.

Adaptive Immunity and the Tumor Microenvironment

The adaptive immune response is a 500-million-year-old (the "Big Bang" of Immunology) collective set of rearranged and/or selected receptors capable of recognizing soluble and cell surface molecules or shape (B cells, antibody), endogenous and extracellular peptides presented by Major Histocompatibility (MHC) molecules including Class I and Class II (conventional αβ T cells), lipid in the context of MHC-like molecules of the CD1 family (NKT cells), metabolites and B7 family molecules/butyrophilins with stress factors (γδT cells), and stress ligands and absence of MHC molecules (natural killer, NK cells). What makes tumor immunogenic is the recruitment of initially innate immune cells to sites of stress or tissue damage with release of Damage-Associated Molecular Pattern (DAMP) molecules. Subsequent maintenance of a chronic inflammatory state, representing a balance between mature, normalized blood vessels, innate and adaptive immune cells and the tumor provides a complex tumor microenvironment serving as the backdrop for Darwinian selection, tumor elimination, tumor equilibrium, and ultimately tumor escape. Effective immunotherapies are still limited, given the complexities of this highly evolved and selected tumor microenvironment. Cytokine therapies and Immune Checkpoint Blockade (ICB) enable immune effector function and are largely dependent on the shape and size of the B and T cell repertoires (the "adaptome"), now accessible by Next-Generation Sequencing (NGS) and dimer-avoidance multiplexed PCR. How immune effectors access the tumor (infiltrated, immune sequestered, and immune desserts), egress and are organized within the tumor are of contemporary interest and substantial investigation.

Genetic lines respond uniquely within the chicken thymic transcriptome to acute heat stress and low dose lipopolysaccharide

Exposure to high temperatures is known to impair immune functions and disease resistance of poultry. Characterizing changes in the transcriptome can help identify mechanisms by which immune tissues, such as the thymus, respond to heat stress. In this study, 22-day-old chickens from two genetic lines (a relatively resistant Fayoumi line and a more susceptible broiler line) were exposed to acute heat stress (35 °C) and/or immune simulation with lipopolysaccharide (LPS; 100 µg/kg). Transcriptome responses in the thymus were identified by RNA-sequencing (RNA-seq). Expression of most genes was unaffected by heat and/or LPS in the Fayoumi line, whereas these treatments had more impact in the broiler line. Comparisons between the broiler and Fayoumi transcriptomes identified a large number of significant genes both at homeostasis and in response to treatment. Functional analyses predicted that gene expression changes impact immune responses, apoptosis, cell activation, migration, and adhesion. In broilers, acute heat stress changed thymic expression responses to LPS and could impact thymocyte survival and trafficking, and thereby contribute to the negative effects of high temperatures on immune responses. Identification of these genes and pathways provides a foundation for testing targets to improve disease resistance in heat-stressed chickens.

Human T-Cell Leukemia Virus Type 1 (HTLV-1) bZIP Factor Upregulates the Expression of ICAM-1 To Facilitate HTLV-1 Infection

Human T-cell leukemia virus type 1 (HTLV-1) causes multiple pathological effects, ranging from a form of leukemia to a spectrum of inflammation-mediated diseases. These diseases arise from one or several infected CD4⁺ T cells among thousands acquiring proliferation and survival advantages and ultimately becoming pathogenic. Given the low incidence of HTLV-1-associated diseases among carriers, such cellular evolutionary processes appear to occur rarely. Therefore, infectious spread of HTLV-1 within the T-cell population may be one underlying factor influencing disease development. Free HTLV-1 virions are poorly infectious, so infection of T cells relies on direct contact between infected and target cells. Following contact, virions pass to target cells through a virological synapse or cellular conduits or are transferred to target cells within an extracellular matrix. Lymphocyte functioning antigen 1 (LFA-1) on the surface of the target cell engaging with its ligand, ICAM-1, on the surface of the infected cell (effector cell) initiates and stabilizes cell-cell contact for infection. We found that stable expression of an HTLV-1 accessory protein, HTLV-1 bZIP factor (HBZ), in Jurkat T cells increases homotypic aggregation. This phenotype was attributed to elevated ICAM-1 expression in the presence of HBZ. Using a single-cycle replication-dependent luciferase assay, we found that HBZ expression in Jurkat cells (used as effector cells) increases HTLV-1 infection. Despite this effect, HBZ could not replace the critical infection-related functions of the HTLV-1 regulatory protein Tax. However, in HTLV-1-infected T cells, knockdown of HBZ expression did lead to a decrease in infection efficiency. These overall results suggest that HBZ contributes to HTLV-1 infectivity.IMPORTANCE Human T-cell leukemia virus type 1 (HTLV-1) causes a variety of diseases, ranging from a fatal form of leukemia to immune-mediated inflammatory diseases. These diseases occur rarely, arising from one or a small subset of virally infected cells infrequently evolving into a pathogenic state. Thus, the process of HTLV-1 cell-to-cell transmission within the host helps influence the probability of disease development. HTLV-1 primarily infects T cells and initially spreads within this cell population when virally infected T cells dock to uninfected target T cells and then transfer HTLV-1 virus particles to the target cells. Here we found that the viral protein HTLV-1 bZIP factor (HBZ) promotes infectivity. HBZ accomplishes this task by increasing the surface abundance of a cellular adhesion protein known as intercellular adhesion molecule 1 (ICAM-1), which helps initiate and stabilize contact (docking) between infected and target T cells. These results define a novel and unexpected function of HBZ, diverging from its defined functions in cellular survival and proliferation.

DC Subsets Regulate Humoral Immune Responses by Supporting the Differentiation of Distinct Tfh Cells

To determine the contribution of skin DC subsets in the regulation of humoral immunity, we used a well-characterized antigen targeting system to limit antigen availability and presentation to certain skin-derived DC subsets. Here we show that delivery of foreign antigen to steady state Langerhans cells (LCs) and cDC1s through the same receptor (Langerin) led to, respectively, robust vs. minimal-to-null humoral immune response. LCs, unlike cDC1s, supported the formation of germinal center T follicular helper cells (GC-Tfh) antigen dose-dependently and then, likely licensed by these T cells, some of the LCs migrated to the B cell area to initiate B cell responses. Furthermore, we found that the cDC1s, probably through their superior T cell activation capacity, prevented the LCs from inducing GC-Tfh cells and humoral immune responses. We further show that targeted delivery of cytokines to DCs can be used to modulate DC-induced humoral immune responses, which has important therapeutic potential. Finally, we show that human LCs, unlike monocyte-derived DCs, can support GC Tfh generation in an in vitro autologous system; and in agreement with mouse data, we provide evidence in NHP studies that targeting LCs without adjuvants is an effective way to induce antibody responses, but does not trigger CD8⁺ T cell responses. Our findings suggest that the major limitations of some relatively ineffective vaccines currently in use or in development might be that (1) they are not formulated to specifically target a certain subset of DCs and/or (2) the antigen dose is not tailored to maximize the intrinsic/pre-programmed capabilities of the specific DC subset. This new and substantial departure from the status quo is expected to overcome problems that have hindered our ability to generate effective vaccines against some key pathogens.