CEACAM1 promotes CD8+ T cell responses and improves control of a chronic viral infection

Hepatic GDP-fucose transporter SLC35C1 attenuates cholestatic liver injury and inflammation by inducing CEACAM1 N153 fucosylation

BACKGROUND AND AIMS

Inflammatory response is crucial for bile acid (BA)-induced cholestatic liver injury, but molecular mechanisms remain to be elucidated. Solute Carrier Family 35 Member C1 (SLC35C1) can transport Guanosine diphosphate-fucose into the Golgi to facilitate protein glycosylation. Its mutation leads to the deficiency of leukocyte adhesion and enhances inflammation in humans. However, little is known about its role in liver diseases.

APPROACH AND RESULTS

Hepatic SLC35C1 mRNA transcripts and protein expression were significantly increased in patients with obstructive cholestasis and mouse models of cholestasis. Immunofluorescence revealed that the upregulated SLC35C1 expression mainly occurred in hepatocytes. Liver-specific ablation of Slc35c1 ( Slc35c1 cKO ) significantly aggravated liver injury in mouse models of cholestasis induced by bile duct ligation and 1% cholic acid-feeding, evidenced by increased liver necrosis, inflammation, fibrosis, and bile ductular proliferation. The Slc35c1 cKO increased hepatic chemokine Ccl2 and Cxcl2 expression and T cell, neutrophil, and F4/80 macrophage infiltration but did not affect the levels of serum and liver BA in mouse models of cholestasis. Liquid chromatography with tandem mass spectrometry analysis revealed that hepatic Slc35c1 deficiency substantially reduced the fucosylation of cell-cell adhesion protein CEACAM1 at N153. Mechanistically, cholestatic levels of conjugated BAs stimulated SLC35C1 expression by activating the STAT3 signaling to facilitate CEACAM1 fucosylation at N153, and deficiency in the fucosylation of CEACAM1 at N135 enhanced the BA-stimulated CCL2 and CXCL2 mRNA expression in primary mouse hepatocytes and Primary Liver Carcinoma/Poliomyelitis Research Foundation/5- ASBT cells.

CONCLUSIONS

Elevated hepatic SLC35C1 expression attenuates cholestatic liver injury by enhancing CEACAM1 fucosylation to suppress CCL2 and CXCL2 expression and liver inflammation.

CEACAM expression in an in-vitro prostatitis model

Background

Prostatitis is an inflammatory disease of the prostate gland, which affects 2-16% of men worldwide and thought to be a cause for prostate cancer (PCa) development. Carcinoembryogenic antigen-related cell adhesion molecules (CEACAMs) are deregulated in inflammation and in PCa. The role of CEACAMs in prostate inflammation and their possible contribution to the malignant transformation of prostate epithelial cells is still elusive. In this study, we investigated the expression of CEACAMs in an in-vitro prostatitis model and their potential role in malignant transformation of prostate epithelial cells.

Methods

Normal prostate epithelial RWPE-1 cells were treated with pro-inflammatory cytokines to achieve an inflammatory state of the cells. The expression of CEACAMs and their related isoforms were analyzed. Additionally, the expression levels of selected CEACAMs were correlated with the expression of malignancy markers and the migratory properties of the cells.

Results

This study demonstrates that the pro-inflammatory cytokines, tumor necrosis factor alpha (TNFα) and interferon-gamma (IFNγ), induce synergistically an up-regulation of CEACAM1 expression in RWPE-1 cells, specifically favoring the CEACAM1-L isoform. Furthermore, overexpressed CEACAM1-L is associated with the deregulated expression of JAK/STAT, NFκB, and epithelial-mesenchymal transition (EMT) genes, as well as an increased cell migration.

Conclusion

We postulate that CEACAM1 isoform CEACAM1-4L may synergistically contribute to inflammation-induced oncogenesis in the prostate.

CEACAMS 1, 5, and 6 in disease and cancer: interactions with pathogens

The CEA family comprises 18 genes and 11 pseudogenes located at chromosome 19q13.2 and is divided into two main groups: cell surface anchored CEA-related cell adhesion molecules (CEACAMs) and the secreted pregnancy-specific glycoproteins (PSGs). CEACAMs are highly glycosylated cell surface anchored, intracellular, and intercellular signaling molecules with diverse functions, from cell differentiation and transformation to modulating immune responses associated with infection, inflammation, and cancer. In this review, we explore current knowledge surrounding CEACAM1, CEACAM5, and CEACAM6, highlight their pathological significance in the areas of cancer biology, immunology, and inflammatory disease, and describe the utility of murine models in exploring questions related to these proteins.

TIM3/CEACAM1 pathway involves in myeloid-derived suppressor cells induced CD8+ T cells exhaustion and bone marrow inflammatory microenvironment in myelodysplastic syndrome

Myeloid-derived suppressor cells (MDSC) induced cellular immune deficiency and bone marrow inflammatory microenvironment play an important role in the pathogenesis and progression of myelodysplastic syndrome (MDS), but the underlying mechanism remains unclear. Here, we revealed that immune checkpoint protein TIM3 and CEACAM1 were highly demonstrated on MDSC and CD8⁺ T cells in MDS patients. CD8⁺ T cells were reduced in number and function and presented a exhaustion state. The levels of pro-inflammatory cytokines (IL-1β, IL-18) and CEACAM1 were raised in bone marrow supernatants and MDSC culture supernatants. Blocking or neutralizing TIM3/CEACAM1 and IL-1β/IL-18 partially reversed exhaustion of CD8⁺ T cells. Moreover, TIM3 correlated with NF-κB /NLRP3 inflammatory pathway. The levels of NF-κB/NLRP3/Caspase-1/IL-1β and IL-18 were all increased in MDSC of MDS. Co-culturing MDSC from MDS patients with rhCEACAM1 enhanced NF-κB/NLRP3/Caspase-1/IL-1β and IL-18 levels, whereas blocking TIM3 could partially reverse the above manifestations. These results indicated that TIM3/CEACAM1 pathway involved in CD8⁺ T cells exhaustion and might activate the NF-κB/NLRP3/Caspase-1 pathway in MDSC, increasing pro-inflammatory cytokines secretion in MDS bone marrow microenvironment. This study provided a basis for applying immune checkpoint inhibitors that could simultaneously modulate pro-inflammatory cytokine secretion and enhance anti-tumour immune function in the treatment of MDS.

Krüppel-like factor 4 regulates the cytolytic effector function of exhausted CD8 T cells

Exhausted CD8 T cells during chronic inflammatory responses against viral infections and cancer are phenotypically and functionally heterogeneous. In particular, CD8 T cells with cytolytic effector function have been recently identified among the exhausted CD8 T cell subsets. However, the regulation of their differentiation and function remains largely unknown. Here, we report that Krüppel-like factor 4 (KLF4) is a critical regulator of the exhaustion process, promoting the cytolytic effector function of exhausted CD8 T cells. KLF4-expressing CD8 T cells in exhaustion contexts showed the features of transitory effector CD8 T cells. Enforced KLF4 expression increased CD8 T cell differentiation into transitory effector subsets and enhanced their antitumor immunity. We further demonstrated that KLF4 also showed a capacity of reinvigorating exhausted CD8 T cells. Last, high KLF4 expression was positively correlated with a favorable prognosis in human patients with cancer. Our study highlights the potential impacts of KLF4 on CD8 T cell exhaustion and antitumor immune therapy.

Expression changes of Tim-3 as one of supplementary indicators for monitoring prognosis of liver pathological changes in chronic HBV infection

Purpose

This study was designed to analyze the liver tissue changes among the CHB patients who received treatment for at least 6 months and follow-up for at least 1 year, together with the correlation between the different disease condition and serum markers.

Methods

One-hundred and eighty-five CHB patients underwent antiviral therapy for at least 6 months were enrolled. In the 12-month follow-up, ultrasonography-guided biopsy was performed. The patients were grouped based on the serum markers and pathological changes in liver tissues. Then we determined the serum markers, virological tests and Tim-3 expression among these groups.

Results

Antiviral therapy significantly reduced liver inflammation indicators and serum Tim-3 level. However, the fibrosis process of liver tissue was not changed, and there are still disputes on the serum marker and hepatic lesion outcomes. Under normal liver function or negative hepatitis B e antigen (HBeAg) of CHB patients, there might be consensus between Tim-3 change and liver pathological outcome. According to the liver tissue inflammation and fibrosis conditions, Tim-3 was positively correlated with liver function indices. Besides, it was also related to fibrosis stage and inflammation grade.

Conclusion

There were inconsistent changes between serum markers and liver tissue conditions after anti-viral therapy. Tim-3 expression was more suitable to indicate the changes of liver inflammatory and fibrosis response to some extent than ALT and AST. It may serve as a certain indicator to predict the CHB prognosis, which could be used as one of the monitoring indicators in liver pathological changes of chronic HBV infection, especially in monitoring liver tissue inflammation.

The Immunological Synapse: An Emerging Target for Immune Evasion by Bacterial Pathogens

Similar to other pathogens, bacteria have developed during their evolution a variety of mechanisms to overcome both innate and acquired immunity, accounting for their ability to cause disease or chronic infections. The mechanisms exploited for this critical function act by targeting conserved structures or pathways that regulate the host immune response. A strategic potential target is the immunological synapse (IS), a highly specialized structure that forms at the interface between antigen presenting cells (APC) and T lymphocytes and is required for the establishment of an effective T cell response to the infectious agent and for the development of long-lasting T cell memory. While a variety of bacterial pathogens are known to impair or subvert cellular processes essential for antigen processing and presentation, on which IS assembly depends, it is only recently that the possibility that IS may be a direct target of bacterial virulence factors has been considered. Emerging evidence strongly supports this notion, highlighting IS targeting as a powerful, novel means of immune evasion by bacterial pathogens. In this review we will present a brief overview of the mechanisms used by bacteria to affect IS assembly by targeting APCs. We will then summarize what has emerged from the current handful of studies that have addressed the direct impact of bacterial virulence factors on IS assembly in T cells and, based on the strategic cellular processes targeted by these factors in other cell types, highlight potential IS-related vulnerabilities that could be exploited by these pathogens to evade T cell mediated immunity.

CEACAM-1 Induced CSF3-receptor Downregulation in Bone Marrow Associated With Refractory Neutropenia in Advanced Cirrhosis

BACKGROUND AND AIMS

Cirrhosis patients exhibit cytopenia, and, at times refractory neutropenia to granulocyte colony-stimulating factor (G-CSF), which acts through the CSF3-receptor (CSF3R), and changes in CSF3R can affect the response. We conducted this study to assess the CSF3R status and its relevance in cirrhotic patients.

METHODS

Cirrhotic patients (n=127) and controls (n=26) with clinically indicated bone marrow (BM) examination were studied. BM assessment was done by qRT-PCR and immunohistochemistry (IHC) for CSF3R. Circulating G-CSF, CSF3R, and carcinoembryonic antigen cell adhesion molecule-1 (CEACAM1) were measured. BM hematopoietic precursor cells and their alterations were examined by flow cytometry. The findings were validated in liver cirrhosis patients who received G-CSF for severe neutropenia.

RESULTS

The mean age was 48.6±13.4 years, and 80.3% were men. Circulatory CSF3R reduction was noted with the advancement of cirrhosis, and confirmed by qRT-PCR and IHC in BM. CSF3R decline was related to decreased hematopoietic stem cells (HSCs) and downregulation of CSF3R in the remaining HSCs. Cocultures confirmed that CEACAM1 led to CSF3R downregulation in BM cells by possible lysosomal degradation. Baseline low peripheral blood-(PB)-CSF3R also predisposed development of infections on follow-up. Decreased CSF3R was also associated with nonresponse to exogenous G-CSF treatment of neutropenia.

CONCLUSIONS

Advanced liver cirrhosis was associated with low CSF3R and high CEACAM1 levels in the BM and circulation, making patients prone to infection and inadequate response to exogenous G-CSF.

Effects of CEACAM1 in oral keratinocytes on HO-1 expression induced by Candida β-glucan particles

Objective

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a member of the carcinoembryonic antigen family. Although its expression has been found in chronic oral inflammatory epithelium, this study aimed to know whether CEACAM1 in oral keratinocytes participates in host immune response against Candida albicans .

Methodology

We investigated CEACAM1 expression in oral keratinocytes induced by C. albicans as well as by Candida cell wall component β-glucan particles (β-GPs). Furthermore, the effects of CEACAM1 on β-GPs-induced heme oxygenase-1 (HO-1) expression and its related signals were examined.

Results

Fluorescence staining showed CEACAM1 expression in oral keratinocytes (RT7) cells, whereas quantitative reverse transcription (RT)-PCR indicated that both live and heat-killed C. albicans increased CEACAM1 mRNA expression in RT7 cells. Examinations using quantitative RT-PCR and western blotting indicated that CEACAM1 expression was also increased by β-GPs derived from C. albicans . Specific siRNA for CEACAM1 decreased HO-1 expression induced by β-GPs from C. albicans as well as the budding yeast microorganism Saccharomyces cerevisiae . Moreover, knockdown of CEACAM1 decreased β-GPs-induced ROS activity in the early phase and translocation of Nrf2 into the nucleus.

Conclusion

CEACAM1 in oral keratinocytes may have a critical role in regulation of HO-1 for host immune defense during Candida infection.

Antibody ligation of CEACAM1, CEACAM3, and CEACAM6, differentially enhance the cytokine release of human neutrophils in responses to Candida albicans

Invasive candidiasis is a healthcare-associated fungal infection with a high mortality rate. Neutrophils, the first line of defense during fungal infections, express the immunoregulatory Candida albicans receptors CEACAM1, CEACAM3, and CEACAM6. We analyzed the effects of specific antibodies on C. albicans-induced neutrophil responses. CEACAM6 ligation by 1H7-4B and to some extent CEACAM1 ligation by B3-17, but not CEACAM3 ligation by 308/3-3, resulted in the immediate release of stored CXCL8 and altered transcriptional responses of the C. albicans-stimulated neutrophils. Integrated network analyses and dynamic simulations of signaling cascades predicted alterations in apoptosis and cytokine secretion. We verified that CEACAM6 ligation enhanced Candida-induced neutrophil apoptosis and increased long-term IL-1β/IL-6 release in responses to C. albicans. CEACAM3 ligation, but not CEACAM1 ligation, increased the long-term release of pro-inflammatory IL-1β/IL-6. Taken together, we demonstrated for the first time that ligation of CEACAM receptors differentially affects the regulation of C. albicans-induced immune functions in human neutrophils.

Roles and mechanisms of circulating CEACAM1 in the cirrhosis-related intestinal hyperpermeability: in vitro approach

BACKGROUND

Cirrhosis-related intestinal hyperpermeability and endotoxemia are characterized by intestinal epithelial cell apoptosis, impaired restitution (proliferation and migration), decreased tight junction protein levels, and subsequent barrier dysfunction. In addition to endotoxin and tumor necrosis factor-α (TNFα), carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) plays crucial roles in the regulation of apoptosis, restitution, tight junction protein-maintained barrier function of intestinal epithelial cells.

METHODS

This study aims to explore the roles and underlying mechanisms of CEACAM1 in cirrhosis-related intestinal hyperpermeability through in vitro approach.

RESULTS

In cirrhotic patients, high serum levels of intestinal hyperpermeability (zonulin and endotoxin) markers were accompanied by elevated serum levels of TNFα and soluble CEACAM1. In in vitro experiments, we evaluated the individual and interacted roles of TNFα and human recombinant CEACAM1 (hrCEACAM1) in LC-sera (sera of cirrhotic patients)-induced intestinal hyperpermeability-related pathogenic signals. In the cell Line human from human colon (Caucasian colon adenocarcinoma) (Caco-2) cell culture, LC-sera, TNFα, and hrCEACAM1 increased apoptosis (measured by Terminal deoxynucleotidyl transferase [TdT] dUTP nick end labeling+/annexin-5+propidium iodide+ cells and caspase-3 activity), decreased restitution capacity (proliferation and migration), and disrupted tight junction protein-maintained barrier function in Caco-2 cells. The pathogenic changes mentioned above were accompanied by an increase in intracellular reactive oxygen species (ROS) levels, lactate dehydrogenase release, and endoplasmic reticulum stress-related signals in the LC-sera or TNFα-pretreated Caco-2 cells. Concomitant incubation of Caco-2 cells with anti-CEACAM1 suppressed these LC-sera or TNFα-induced negative effects on restitution, barrier function, and cell viability.

CONCLUSION

This study demonstrated that sera from cirrhotic patients contain soluble CEACAM1, which is involved in the pathogenesis of intestinal hyperpermeability. Accordingly, it is noteworthy to explore the potential use of anti-CEACAM1 treatment for cirrhosis-related intestinal hyperpermeability and endotoxemia.

The Optimization and Biological Significance of a 29-Host-Immune-mRNA Panel for the Diagnosis of Acute Infections and Sepsis

In response to the unmet need for timely accurate diagnosis and prognosis of acute infections and sepsis, host-immune-response-based tests are being developed to help clinicians make more informed decisions including prescribing antimicrobials, ordering additional diagnostics, and assigning level of care. One such test (InSep™, Inflammatix, Inc.) uses a 29-mRNA panel to determine the likelihood of bacterial infection, the separate likelihood of viral infection, and the risk of physiologic decompensation (severity of illness). The test, being implemented in a rapid point-of-care platform with a turnaround time of 30 min, enables accurate and rapid diagnostic use at the point of impact. In this report, we provide details on how the 29-biomarker signature was chosen and optimized, together with its molecular, immunological, and medical significance to better understand the pathophysiological relevance of altered gene expression in disease. We synthesize key results obtained from gene-level functional annotations, geneset-level enrichment analysis, pathway-level analysis, and gene-network-level upstream regulator analysis. Emerging findings are summarized as hallmarks on immune cell interaction, inflammatory mediators, cellular metabolism and homeostasis, immune receptors, intracellular signaling and antiviral response; and converging themes on neutrophil degranulation and activation involved in immune response, interferon, and other signaling pathways.

Transcriptome analysis following neurotropic virus infection reveals faulty innate immunity and delayed antigen presentation in mice susceptible to virus-induced demyelination

Viral infections of the central nervous system cause acute or delayed neuropathology and clinical consequences ranging from asymptomatic courses to chronic, debilitating diseases. The outcome of viral encephalitis is partially determined by genetically programed immune response patterns of the host. Experimental infection of mice with Theiler's murine encephalomyelitis virus (TMEV) causes diverse neurologic diseases, including TMEV‐induced demyelinating disease (TMEV‐IDD), depending on the used mouse strain. The aim of the present study was to compare initial transcriptomic changes occurring in the brain of TMEV‐infected SJL (TMEV‐IDD susceptible) and C57BL/6 (TMEV‐IDD resistant) mice. Animals were infected with TMEV and sacrificed 4, 7, or 14 days post infection. RNA was isolated from brain tissue and analyzed by whole‐transcriptome sequencing. Selected differences were confirmed on a protein level by immunohistochemistry. In mock‐infected SJL and C57BL/6 mice, >200 differentially expressed genes (DEGs) were detected. Following TMEV‐infection, the number of DEGs increased to >700. Infected C57BL/6 mice showed a higher expression of transcripts related to antigen presentation via major histocompatibility complex (MHC) I, innate antiviral immune responses and cytotoxicity, compared with infected SJL animals. Expression of many of those genes was weaker or delayed in SJL mice, associated with a failure of viral clearance in this mouse strain. SJL mice showed prolonged elevation of MHC II and chemotactic genes compared with C57BL/6 mice, which presumably facilitates the induction of chronic demyelinating disease. In addition, elevated expression of several genes associated with immunomodulatory or –suppressive functions was observed in SJL mice. The exploratory study confirms previous observations in the model and provides an extensive list of new immunologic parameters potentially contributing to different outcomes of viral encephalitis in two mouse strains.

The TGF-β/miR-31/CEACAM1-S axis inhibits CD4+ CD25+ Treg differentiation in systemic lupus erythematosus

Defects causing concomitant loss of CD25 expression in regulatory T cells (Tregs) have been identified in systemic lupus erythematosus (SLE). However, the cause of this deficiency is not fully understood. Carcinoembryonic antigen related cell adhesion molecule 1 (CEACAM1), an immune co-receptor, contributes to general T-cell function and activation. Our previous study revealed that CEACAM1 expression was upregulated in peripheral blood mononuclear cells (PBMCs) from patients with SLE. However, its role remains unclear. Herein, we confirmed CEACAM1, especially CEACAM1-S, was upregulated in PBMCs from patients with SLE. CEACAM1-S over-expression inhibits CD4⁺ CD25⁺ Treg differentiation, whereas knockdown of CEACAM1 had the opposite effect in vitro. CEACAM1-S is the target of miR-31. MiR-31 mimic inhibits CEACAM1 expression and enhances CD4⁺ CD25⁺ Treg differentiation, which was reversed by CEACAM1-S over-expression. Moreover, the circulating TGF-β level was upregulated in SLE patients and TGF-β reduced miR-31 expression via enhancing NF-κB activity. Importantly, CEACAM1 and TGF-β mRNA levels were downregulated, while the miR-31 level and the abundance of CD4⁺ CD25⁺ Tregs were increased in inactive patients compared with that in patients with active SLE. In addition, CEACAM1-S expression was positively correlated with the Systemic Lupus Erythematosus Disease Activity Index (SLEDAI) score, while CD4⁺ CD25⁺ Treg abundance and miR-31 level were negatively correlated with the SLEDAI score. In conclusion, reduced activity of miR-31 by TGF-β, via the inhibition of NF-ᴋB, acted to inhibit the differentiation of CD4⁺ CD25⁺ Tregs by directly targeting CEACAM1-S and to promote autoimmunity.

Bacterial protein domains with a novel Ig-like fold target human CEACAM receptors

Streptococcus agalactiae, also known as group B Streptococcus (GBS), is the major cause of neonatal sepsis in humans. A critical step to infection is adhesion of bacteria to epithelial surfaces. GBS adhesins have been identified to bind extracellular matrix components and cellular receptors. However, several putative adhesins have no host binding partner characterised. We report here that surface-expressed β protein of GBS binds to human CEACAM1 and CEACAM5 receptors. A crystal structure of the complex showed that an IgSF domain in β represents a novel Ig-fold subtype called IgI3, in which unique features allow binding to CEACAM1. Bioinformatic assessment revealed that this newly identified IgI3 fold is not exclusively present in GBS but is predicted to be present in adhesins from other clinically important human pathogens. In agreement with this prediction, we found that CEACAM1 binds to an IgI3 domain found in an adhesin from a different streptococcal species. Overall, our results indicate that the IgI3 fold could provide a broadly applied mechanism for bacteria to target CEACAMs.

One Stone, Two Birds: The Roles of Tim-3 in Acute Myeloid Leukemia

T cell immunoglobulin and mucin protein 3 (Tim-3) is an immune checkpoint and plays a vital role in immune responses during acute myeloid leukemia (AML). Targeting Tim-3 kills two birds with one stone by balancing the immune system and eliminating leukemia stem cells (LSCs) in AML. These functions make Tim-3 a potential target for curing AML. This review mainly discusses the roles of Tim-3 in the immune system in AML and as an AML LSC marker, which sheds new light on the role of Tim-3 in AML immunotherapy.

Enhanced expression of immune checkpoint receptors during SARS-CoV-2 viral infection

The immune system is tightly regulated by the activity of stimulatory and inhibitory immune receptors. This immune homeostasis is usually disturbed during chronic viral infection. Using publicly available transcriptomic datasets, we conducted in silico analyses to evaluate the expression pattern of 38 selected immune inhibitory receptors (IRs) associated with different myeloid and lymphoid immune cells during coronavirus disease 2019 (COVID-19) infection. Our analyses revealed a pattern of overall upregulation of IR mRNA during severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection. A large number of IRs expressed on both lymphoid and myeloid cells were upregulated in nasopharyngeal swabs (NPSs), while lymphoid-associated IRs were specifically upregulated in autopsies, reflecting severe, terminal stage COVID-19 disease. Eight genes (BTLA, LAG3, FCGR2B, PDCD1, CEACAM1, CTLA4, CD72, and SIGLEC7), shared by NPSs and autopsies, were more expressed in autopsies and were directly correlated with viral levels. Single-cell data from blood and bronchoalveolar samples also reflected the observed association between IR upregulation and disease severity. Moreover, compared to SARS-CoV-1, influenza, and respiratory syncytial virus infections, the number and intensities of upregulated IRs were higher in SARS-CoV-2 infections. In conclusion, the immunopathology and severity of COVID-19 could be attributed to dysregulation of different immune inhibitors. Targeting one or more of these immune inhibitors could represent an effective therapeutic approach for the treatment of COVID-19 early and late immune dysregulations.

Immune Checkpoints: Novel Therapeutic Targets to Attenuate Sepsis-Induced Immunosuppression

Sepsis is a leading cause of death in intensive care units and survivors develop prolonged immunosuppression and a high incidence of recurrent infections. No definitive therapy exists to treat sepsis and physicians rely on supportive care including antibiotics, intravenous fluids, and vasopressors. With the rising incidence of antibiotic resistant microbes, it is becoming increasingly critical to discover novel therapeutics. Sepsis-induced leukocyte dysfunction and immunosuppression is recognized as an important contributor towards increased morbidity and mortality. Pre-clinical and clinical studies show that specific cell surface inhibitory immune checkpoint receptors and ligands including PD-1, PD-L1, CTLA4, BTLA, TIM3, OX40, and 2B4 play important roles in the pathophysiology of sepsis by mediating a fine balance between host immune competency and immunosuppression. Pre-clinical studies targeting the inhibitory effects of these immune checkpoints have demonstrated reversal of leukocyte dysfunction and improved host resistance of infection. Measurement of immune checkpoint expression on peripheral blood leukocytes may serve as a means of stratifying patients to direct individualized therapy. This review focuses on advances in our understanding of the role of immune checkpoints in the host response to infections, and the potential clinical application of therapeutics targeting the inhibitory immune checkpoint pathways for the management of septic patients.

Automated Extraction of Information From Texts of Scientific Publications: Insights Into HIV Treatment Strategies

Text analysis can help to identify named entities (NEs) of small molecules, proteins, and genes. Such data are very important for the analysis of molecular mechanisms of disease progression and development of new strategies for the treatment of various diseases and pathological conditions. The texts of publications represent a primary source of information, which is especially important to collect the data of the highest quality due to the immediate obtaining information, in comparison with databases. In our study, we aimed at the development and testing of an approach to the named entity recognition in the abstracts of publications. More specifically, we have developed and tested an algorithm based on the conditional random fields, which provides recognition of NEs of (i) genes and proteins and (ii) chemicals. Careful selection of abstracts strictly related to the subject of interest leads to the possibility of extracting the NEs strongly associated with the subject. To test the applicability of our approach, we have applied it for the extraction of (i) potential HIV inhibitors and (ii) a set of proteins and genes potentially responsible for viremic control in HIV-positive patients. The computational experiments performed provide the estimations of evaluating the accuracy of recognition of chemical NEs and proteins (genes). The precision of the chemical NEs recognition is over 0.91; recall is 0.86, and the F1-score (harmonic mean of precision and recall) is 0.89; the precision of recognition of proteins and genes names is over 0.86; recall is 0.83; while F1-score is above 0.85. Evaluation of the algorithm on two case studies related to HIV treatment confirms our suggestion about the possibility of extracting the NEs strongly relevant to (i) HIV inhibitors and (ii) a group of patients i.e., the group of HIV-positive individuals with an ability to maintain an undetectable HIV-1 viral load overtime in the absence of antiretroviral therapy. Analysis of the results obtained provides insights into the function of proteins that can be responsible for viremic control. Our study demonstrated the applicability of the developed approach for the extraction of useful data on HIV treatment.

Evaluation of carcinoembryonic antigen-related cell adhesion molecule 1 blood serum levels in women at high risk for preeclampsia

PROBLEM

The aim of this study was to evaluate the sCEACAM1 concentrations in serum from patients in the first trimester who have a high risk for developing PE during pregnancy.

METHOD OF THE STUDY

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) levels were determined with ELISA. The patients (n = 109) were divided into two groups: patients who have a high risk of developing PE early-onset and a control group. Patients who have a high risk of developing PE were then divided into two subgroups depending on PE development in third trimester of pregnancy: PE in third trimester versus no PE in third trimester.

RESULTS

sCEACAM1 concentrations in patients who were screened as having a high risk for developing PE were significantly higher than in healthy pregnant women in the first trimester (p = .03). The highest sCEACAM1 concentration was found in the high-risk group with PE development compared to the control group (p = .004).

CONCLUSION

Elevated sCEACAM1 blood serum levels in women with PE suggest that there is immune dysregulation in early pregnancy, which may be helpful in PE prediction and therapy.

CEACAM1 regulates CD8+ T cell immunity and protects from severe pathology during Citrobacter rodentium induced colitis

The incidence of gastrointestinal infections continues to increase, and infectious colitis contributes significantly to morbidity and mortality worldwide. Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) has been discovered to be strongly involved in the intestinal homeostasis. However, whether intestinal CEACAM1 expression has an impact on the control of infectious colitis remains elusive. Citrobacter rodentium (C. rodentium) is a gram-negative enteric pathogen that induces colonic inflammation in mice, with a critical role for CD4+ T cell but not CD8+ T cell immunity to primary infection. Here, we show that Ceacam1-/- mice are much more susceptible to C. rodentium infection than wildtype mice, which is mediated by a defect in the intestinal barrier and, surprisingly, by a dysregulated CD8+ T cell but not CD4+ T cell response in the colon. CEACAM1 expression is essential for the control of CD8+ T cell immunity, as CEACAM1 deficiency during C. rodentium infection inhibits CD8+ T cell exhaustion. We conclude that CEACAM1 is an important regulator of CD8+ T cell function in the colon, and blocking CEACAM1 signaling to activate CD8+ T cells may have unforeseen side effects.

Live vaccine infection burden elicits adaptive humoral and cellular immunity required to prevent Zika virus infection

BACKGROUND

The emergence of Zika virus (ZIKV) as an important cause of congenital and childhood developmental disorders presents another challenge to global health. Efforts to develop a Zika vaccine have begun although vaccine development against flaviviruses, of which ZIKV belongs to, has proven to be time-consuming and challenging. Defining the vaccine attributes that elicit adaptive immune response necessary for preventing ZIKV infection could provide an evidence-based guide to Zika vaccine development.

METHODS

We used a previously described attenuated ZIKV DN-2 strain in a type-I interferon receptor deficient mouse model and tested the hypothesis that duration of vaccine burden rather than peak level of infection, is a determinant of immunogenicity. We quantified both humoral and cellular responses against ZIKV using plaque reduction neutralisation test and flow cytometry with ELISPOT assays, respectively. Vaccinated mice were challenged with wild-type ZIKV (H/PF/2013 strain) to determine the level of protection against infection.

FINDINGS

We found that the overall vaccine burden is directly correlated with neutralising antibody titres. Reduced duration of vaccine burden lowered neutralising antibody titres that resulted in subclinical infection, despite unchanged peak vaccine viraemia levels. We also found that sterilising immunity is dependant on both neutralising antibody and CD8⁺T cell responses; depletion of CD8⁺T cells in vaccinated animals led to wild-type ZIKV infection, especially in the male reproductive tract.

INTERPRETATION

Our findings indicate that duration of attenuated virus vaccine burden is a determinant of humoral and cellular immunity and also suggest that vaccines that elicit both arms of the adaptive immune response are needed to fully prevent ZIKV transmission.

FUNDING

This study was supported by the National Medical Research Council through the Clinician-Scientist Award (Senior Investigator) to E.E.O. Salary support for S.W. was from a Competitive Research Programme grant awarded by the National Research Foundation of Singapore.

A perspective on HPK1 as a novel immuno-oncology drug target

In this perspective review, the role Hematopoietic Progenitor Kinase 1 (HPK1) in tumor immunity will be reviewed, with special emphasis on how T cells are negatively-regulated at different junctures of cancer-immunity cycle by this regulatory kinase. The review will highlight the strengths and weaknesses of HPK1 as a candidate target for novel immuno-oncology (IO) drug development that is centered on the use of small molecule kinase inhibitor to modulate the immune response against cancer. Such a therapeutic approach, if proven successful, could supplement the cancer cell-centric standard of care therapies in order to fully meet the therapeutic needs of cancer patients.

Tyrosine Kinase Inhibitors Play an Antiviral Action in Patients Affected by Chronic Myeloid Leukemia: A Possible Model Supporting Their Use in the Fight Against SARS-CoV-2

SARS-CoV-2 is the viral agent responsible for the pandemic that in the first months of 2020 caused about 400,000 deaths. Among compounds proposed to fight the SARS-CoV-2-related disease (COVID-19), tyrosine kinase inhibitors (TKIs), already effective in Philadelphia-positive acute lymphoblastic leukemia (Ph+ ALL) and chronic myeloid leukemia (CML), have been proposed on the basis of their antiviral action already demonstrated against SARS-CoV-1. Very few cases of COVID-19 have been reported in Ph+ ALL and in CML Italian cohorts; authors suggested that this low rate of infections might depend on the use of TKIs, but the biological causes of this phenomenon remain unknown. In this study, the CML model was used to test if TKIs would sustain or not the viral replication and if they could damage patient immunity. Firstly, the infection and replication rate of torquetenovirus (TTV), whose load is inversely proportional to the host immunological control, have been measured in CML patients receiving nilotinib. A very low percentage of subjects were infected at baseline, and TTV did not replicate or at least showed a low replication rate during the follow-up, with a mean load comparable to the measured one in healthy subjects. Then, after gene expression profiling experiments, we found that several “antiviral” genes, such as CD28 and IFN gamma, were upregulated, while genes with “proviral” action, such as ARG-1, CEACAM1, and FUT4, were less expressed during treatment with imatinib, thus demonstrating that TKIs are not detrimental from the immunological point of view. To sum up, our data could offer some biological explanations to the low COVID-19 occurrence in Ph+ ALL and CML patients and sustain the use of TKIs in COVID-19, as already proposed by several international ongoing studies.

Evaluation of the Anti-Tumor Activity of the Humanized Monoclonal Antibody NEO-201 in Preclinical Models of Ovarian Cancer

Purpose: Despite high initial response rates with cytoreductive surgery, conventional chemotherapy and the incorporation of biologic agents, ovarian cancer patients often relapse and die from their disease. New approaches are needed to improve patient outcomes. This study was designed to evaluate the antitumor activity of NEO-201 monoclonal antibody (mAb) in preclinical models of ovarian cancer where the NEO-201 target is highly expressed.

Experimental Design: Functional analysis of NEO-201 against tumor cell lines was performed by antibody-dependent cellular cytotoxicity (ADCC) assays. Binding of NEO-201 to tumor tissues and cell lines were determined by immunohistochemistry (IHC) and flow cytometry, respectively. Further characterization of the antigen recognized by NEO-201 was performed by mass spectrometry. Ovarian cancer models were used to evaluate the anti-tumor activity of NEO-201 in vivo. NEO-201 at a concentration of 250 g/mouse was injected intraperitoneally (IP) on days 1, 4, and 8. Human PBMCs were injected IP simultaneously as effector cells.

Results: Both IHC and flow cytometry revealed that NEO-201 binds prominently to the colon, pancreatic, and mucinous ovarian cancer tissues and cell lines. Immunoprecipitation of the antigen recognized by NEO-201 was performed in human ovarian, colon, and pancreatic cancer cell lines. From these screening, carcinoembryonic antigen-related cell adhesion molecule 5 (CEACAM5) and CEACAM6 were identified as the most likely targets of NEO-201. Our results confirmed that NEO-201 binds different types of cancers; the binding is highly selective for the tumor cells without cross reactivity with the surrounding healthy tissue. Functional analysis revealed that NEO-201 mediates ADCC killing against human ovarian and colorectal carcinoma cell lines in vitro. In addition, NEO-201 inhibited tumor growth in the presence of activated human PBMCs in orthotopic mouse models of both primary and metastatic ovarian cancer. Importantly, NEO-201 prolonged survival of tumor-bearing mice.

Conclusions: These data suggested that NEO-201 has an antitumor activity against tumor cells expressing its antigen. Targeting an antigen expressed in tumors, but not in normal tissues, allows patient selection for optimal treatment. These findings strongly indicate that NEO-201 warrants clinical testing as both a novel therapeutic and diagnostic agent for treatment of ovarian carcinomas. A first in human clinical trial evaluating NEO-201 in adults with chemo-resistant solid tumors is ongoing at the NIH clinical Center.

Anti-carcinoembryonic antigen-related cell adhesion molecule antibody for fluorescence visualization of primary colon cancer and metastases in patient-derived orthotopic xenograft mouse models

Background: Monoclonal antibody (mAb) 6G5j is a novel anti-CEACAM monoclonal antibody. Our aim was to investigate mAb 6G5j binding characteristics and to validate fluorescence targeting of colorectal tumors and metastases in patient derived orthotopic xenograft (PDOX) models with fluorescently labeled 6G5j.

Materials/Methods: The MAb 6G5j binding profile was analyzed with ELISA, Western blot and immunohistochemistry. MAb 6G5j was conjugated to near-infrared dye IR800CW (LI-COR). Western blotting was performed with various colon cancer cell lysates to determine CEACAM expression. Nude mice received orthotopic implantation of patient-derived primary colon cancer and patient-derived colon cancer metastases. Mice were administered varying doses of 6G5j-IR800CW via tail vein injection and imaged 24 and 48 hours later.

Results: MAb 6G5j bound to human CEACAM1, 3, 5, 6 and 8. Western blotting demonstrated varied expression of CEACAMs in 15 of 16 colon cancer lysates. Dose and time-response imaging demonstrated optimal imaging 48 hours after administration of 50 μg 6G5j-IR800CW (Tumor-to-liver ratio (TLR) 3.17, SEM ± 0.45). Primary cancers and multiple metastases were fluorescently visualized.

Conclusions: Anti-CEACAM antibody 6G5j binds multiple CEACAMs which may lead to improved detection of tumor margins for tumors and metastases that have variable expression of CEA and other CEACAMs. 6G5j mAb may be useful for colon cancer detection for pre-surgical diagnosis and fluorescence-guided surgery.

Mutated CEACAMs Disrupt Transforming Growth Factor Beta Signaling and Alter the Intestinal Microbiome to Promote Colorectal Carcinogenesis

BACKGROUND & AIMS

We studied interactions among proteins of the carcinoembryonic antigen-related cell adhesion molecule (CEACAM) family, which interact with microbes, and transforming growth factor beta (TGFB) signaling pathway, which is often altered in colorectal cancer cells. We investigated mechanisms by which CEACAM proteins inhibit TGFB signaling and alter the intestinal microbiome to promote colorectal carcinogenesis.

METHODS

We collected data on DNA sequences, messenger RNA expression levels, and patient survival times from 456 colorectal adenocarcinoma cases, and a separate set of 594 samples of colorectal adenocarcinomas, in The Cancer Genome Atlas. We performed shotgun metagenomic sequencing analyses of feces from wild-type mice and mice with defects in TGFB signaling (Sptbn1+/- and Smad4+/-/Sptbn1+/-) to identify changes in microbiota composition before development of colon tumors. CEACAM protein and its mutants were overexpressed in SW480 and HCT116 colorectal cancer cell lines, which were analyzed by immunoblotting and proliferation and colony formation assays.

RESULTS

In colorectal adenocarcinomas, high expression levels of genes encoding CEACAM proteins, especially CEACAM5, were associated with reduced survival times of patients. There was an inverse correlation between expression of CEACAM genes and expression of TGFB pathway genes (TGFBR1, TGFBR2, and SMAD3). In colorectal adenocarcinomas, we also found an inverse correlation between expression of genes in the TGFB signaling pathway and genes that regulate stem cell features of cells. We found mutations encoding L640I and A643T in the B3 domain of human CEACAM5 in colorectal adenocarcinomas; structural studies indicated that these mutations would alter the interaction between CEACAM5 and TGFBR1. Overexpression of these mutants in SW480 and HCT116 colorectal cancer cell lines increased their anchorage-independent growth and inhibited TGFB signaling to a greater extent than overexpression of wild-type CEACAM5, indicating that they are gain-of-function mutations. Compared with feces from wild-type mice, feces from mice with defects in TGFB signaling had increased abundance of bacterial species that have been associated with the development of colon tumors, including Clostridium septicum, and decreased amounts of beneficial bacteria, such as Bacteroides vulgatus and Parabacteroides distasonis.

CONCLUSION

We found expression of CEACAMs and genes that regulate stem cell features of cells to be increased in colorectal adenocarcinomas and inversely correlated with expression of TGFB pathway genes. We found colorectal adenocarcinomas to express mutant forms of CEACAM5 that inhibit TGFB signaling and increase proliferation and colony formation. We propose that CEACAM proteins disrupt TGFB signaling, which alters the composition of the intestinal microbiome to promote colorectal carcinogenesis.

Unaltered Fungal Burden and Lethality in Human CEACAM1-Transgenic Mice During Candida albicans Dissemination and Systemic Infection

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1, CD66a) is a receptor for Candida albicans. It is crucial for the immune response of intestinal epithelial cells to this opportunistic pathogen. Moreover, CEACAM1 is of importance for the mucosal colonization by different bacterial pathogens. We therefore studied the influence of the human CEACAM1 receptor in human CEACAM1-transgenic mice on the C. albicans colonization and infection utilizing a colonization/dissemination and a systemic infection mouse model. Our results showed no alterations in the host response between the transgenic mice and the wild-type littermates to the C. albicans infections. Both mouse strains showed comparable C. albicans colonization and mycobiota, similar fungal burdens in various organs, and a similar survival in the systemic infection model. Interestingly, some of the mice treated with anti-bacterial antibiotics (to prepare them for C. albicans colonization via oral infection) also showed a strong reduction in endogenous fungi instead of the normally observed increase in fungal numbers. This was independent of the expression of human CEACAM1. In the systemic infection model, the human CEACAM1 expression was differentially regulated in the kidneys and livers of Candida-infected transgenic mice. Notably, in the kidneys, a total loss of the largest human CEACAM1 isoform was observed. However, the overwhelming immune response induced in the systemic infection model likely covered any CEACAM1-specific effects in the transgenic animals. In vitro studies using bone marrow-derived neutrophils from both mouse strains also revealed no differences in their reaction to C. albicans. In conclusion, in contrast to bacterial pathogens interacting with CEACAM1 on different mucosal surfaces, the human CEACAM1-transgenic mice did not reveal a role of human CEACAM1 in the in vivo candidiasis models used here. Further studies and different approaches will be needed to reveal a putative role of CEACAM1 in the host response to C. albicans.

TIM3 comes of age as an inhibitory receptor

T cell immunoglobulin and mucin domain-containing protein 3 (TIM3), a member of the TIM family, was originally identified as a receptor expressed on interferon-γ-producing CD4⁺ and CD8⁺ T cells. Initial data indicated that TIM3 functioned as a 'co-inhibitory' or 'checkpoint' receptor, but due to the lack of a definable inhibitory signalling motif, it was also suggested that TIM3 might act as a co-stimulatory receptor. Recent studies have shown that TIM3 is part of a module that contains multiple co-inhibitory receptors (checkpoint receptors), which are co-expressed and co-regulated on dysfunctional or 'exhausted' T cells in chronic viral infections and cancer. Furthermore, co-blockade of TIM3 and programmed cell death 1 (PD1) can result in tumour regression in preclinical models and can improve anticancer T cell responses in patients with advanced cancers. Here, we highlight the developments in understanding TIM3 biology, including novel ligand identification and the discovery of loss-of-function mutations associated with human disease. In addition, we summarize emerging data from human clinical trials showing that TIM3 indeed acts as a 'checkpoint' receptor and that inhibition of TIM3 enhances the antitumour effect of PD1 blockade.

New therapeutic targets for the prevention of infectious acute exacerbations of COPD: role of epithelial adhesion molecules and inflammatory pathways

Chronic respiratory diseases are among the leading causes of mortality worldwide, with the major contributor, chronic obstructive pulmonary disease (COPD) accounting for approximately 3 million deaths annually. Frequent acute exacerbations (AEs) of COPD (AECOPD) drive clinical and functional decline in COPD and are associated with accelerated loss of lung function, increased mortality, decreased health-related quality of life and significant economic costs. Infections with a small subgroup of pathogens precipitate the majority of AEs and consequently constitute a significant comorbidity in COPD. However, current pharmacological interventions are ineffective in preventing infectious exacerbations and their treatment is compromised by the rapid development of antibiotic resistance. Thus, alternative preventative therapies need to be considered. Pathogen adherence to the pulmonary epithelium through host receptors is the prerequisite step for invasion and subsequent infection of surrounding structures. Thus, disruption of bacterial-host cell interactions with receptor antagonists or modulation of the ensuing inflammatory profile present attractive avenues for therapeutic development. This review explores key mediators of pathogen-host interactions that may offer new therapeutic targets with the potential to prevent viral/bacterial-mediated AECOPD. There are several conceptual and methodological hurdles hampering the development of new therapies that require further research and resolution.

CEACAM-1 promotes myocardial injury following coxsackievirus infection by regulating the coxsackievirus-adenovirus receptor

OBJECTIVE

To determine the effects and mechanism of carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM-1, CC1)-mediated regulation of the Coxsackie and Adenovirus Receptor (CAR) after Coxsackievirus B3 (CVB3) infection.

METHODS

A mouse CC1 overexpression recombinant virus was constructed, followed by insertion of a pLVX-CEACAM 1-zsgreen-puro (rLV-CEACAM 1) plasmid into the recombinant retrovirus. Cardiac myocytes were assigned into different groups according to various treatments. The apoptosis rate and cell activity in each group were observed. Further, CAR expression and SYK, IL-1β, and p-SYK levels were measured.

RESULTS

The recombinant retrovirus titer was measured as 1.5 × 10 TUs/ml. The apoptosis rate of cardiac myocytes in the CC1 overexpression plus CVB3 group was significantly elevated, and the relative expression of the CAR gene was the highest in the CC1 overexpression plus CVB3 group. TNF-α and IL-1β levels increased due to CC1 overexpression and further increased after CVB3 infection. CAR protein expression also changed along with the levels of CC1, SYK, and TNF-α after infection.

CONCLUSION

CC1 may promote CAR expression after CVB3 infection and regulate CAR protein expression by activating the CC1-SYK-TNF-α signaling axis during the infection process.

CEACAM1 structure and function in immunity and its therapeutic implications

The type I membrane protein receptor carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) distinctively exhibits significant alternative splicing that allows for tunable functions upon homophilic binding. CEACAM1 is highly expressed in the tumor environment and is strictly regulated on lymphocytes such that its expression is restricted to activated cells where it is now recognized to function in tolerance pathways. CEACAM1 is also an important target for microbes which have co-opted these attributes of CEACAM1 for the purposes of invading the host and evading the immune system. These properties, among others, have focused attention on CEACAM1 as a unique target for immunotherapy in autoimmunity and cancer. This review examines recent structural information derived from the characterization of CEACAM1:CEACAM1 interactions and heterophilic modes of binding especially to microbes and how this relates to CEACAM1 function. Through this, we aim to provide insights into targeting CEACAM1 for therapeutic intervention.

Fusobacterium nucleatum supresses anti-tumor immunity by activating CEACAM1

Fusobacterium nucleatum (F. nucleatum) is an oral anaerobe found to be enriched in colorectal cancer (CRC). Presence of F. nucleatum in CRC has been correlated with resistance to chemotherapy and poor prognosis. We previously demonstrated that the Fap2 outer-surface protein of F. nucleatum binds and activates the human inhibitory receptor TIGIT which is expressed by T and Natural Killer (NK) cells, and inhibits anti-tumor immunity. Here we show that F. nucleatum also binds and activates the human inhibitory receptor CEACAM1 leading to inhibition of T and NK cells activities. Our results suggest that using CEACAM1 and TIGIT inhibitors and specific targeting of fusobacteria should be considered for treating fusobacteria-colonized tumors.

Size Matters: The Functional Role of the CEACAM1 Isoform Signature and Its Impact for NK Cell-Mediated Killing in Melanoma

Malignant melanoma is the most aggressive and treatment resistant type of skin cancer. It is characterized by continuously rising incidence and high mortality rate due to its high metastatic potential. Various types of cell adhesion molecules have been implicated in tumor progression in melanoma. One of these, the carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1), is a multi-functional receptor protein potentially expressed in epithelia, endothelia, and leukocytes. CEACAM1 often appears in four isoforms differing in the length of their extracellular and intracellular domains. Both the CEACAM1 expression in general, and the ratio of the expressed CEACAM1 splice variants appear very dynamic. They depend on both the cell activation stage and the cell growth phase. Interestingly, normal melanocytes are negative for CEACAM1, while melanomas often show high expression. As a cell–cell communication molecule, CEACAM1 mediates the direct interaction between tumor and immune cells. In the tumor cell this interaction leads to functional inhibitions, and indirectly to decreased cancer cell immunogenicity by down-regulation of ligands of the NKG2D receptor. On natural killer (NK) cells it inhibits NKG2D-mediated cytolysis and signaling. This review focuses on novel mechanistic insights into CEACAM1 isoforms for NK cell-mediated immune escape mechanisms in melanoma, and their clinical relevance in patients suffering from malignant melanoma.

Expression and characterization of soluble epitope-defined major histocompatibility complex (MHC) from stable eukaryotic cell lines

MHC class I-specific reagents such as fluorescently-labeled multimers (e.g., tetramers) have greatly advanced the understanding of CD8+ T cells under normal and diseased states. However, recombinant MHC class I components (comprising MHC class I heavy chain and β2 microglobulin) are usually produced in bacteria following a lengthy purification protocol that requires additional non-covalent folding steps with exogenous peptide for complete molecular assembly. We have provided an alternative and rapid approach to generating soluble and fully-folded MHC class I molecules in eukaryotic cell lines (such as CHO cells) using a Sleeping Beauty transposon system. Importantly, this method culminates in generating stable cell lines that reliably secrete epitope-defined MHC class I molecules into the tissue media for convenient purification and eventual biotinylation/multimerization. Additionally, MHC class I components are covalently linked, providing the opportunity to produce a diverse set of CD8+ T cell-specific reagents bearing peptides with various affinities to MHC class I.

CEACAM1 in Liver Injury, Metabolic and Immune Regulation

Carcinoembryonic antigen-related cell adhesion molecule 1 (CEACAM1) is a transmembrane glycoprotein that is expressed on epithelial, endothelial and immune cells. CEACAM1 is a differentiation antigen involved in the maintenance of epithelial polarity that is induced during hepatocyte differentiation and liver regeneration. CEACAM1 regulates insulin sensitivity by promoting hepatic insulin clearance, and controls liver tolerance and mucosal immunity. Obese insulin-resistant humans with non-alcoholic fatty liver disease manifest loss of hepatic CEACAM1. In mice, deletion or functional inactivation of CEACAM1 impairs insulin clearance and compromises metabolic homeostasis which initiates the development of obesity and hepatic steatosis and fibrosis with other features of non-alcoholic steatohepatitis, and adipogenesis in white adipose depot. This is followed by inflammation and endothelial and cardiovascular dysfunctions. In obstructive and inflammatory liver diseases, soluble CEACAM1 is shed into human bile where it can serve as an indicator of liver disease. On immune cells, CEACAM1 acts as an immune checkpoint regulator, and deletion of Ceacam1 gene in mice causes exacerbation of inflammation and hyperactivation of myeloid cells and lymphocytes. Hence, hepatic CEACAM1 resides at the central hub of immune and metabolic homeostasis in both humans and mice. This review focuses on the regulatory role of CEACAM1 in liver and biliary tract architecture in health and disease, and on its metabolic role and function as an immune checkpoint regulator of hepatic inflammation.