The role of thymus-expressed chemokine and its receptor CCR9 on lymphocytes in the regional specialization of the mucosal immune system

Spectrum of COVID-19 induced liver injury: A review report

The coronavirus disease 2019 (COVID-19) pandemic has caused changes in the global health system, causing significant setbacks in healthcare systems worldwide. This pandemic has also shown resilience, flexibility, and creativity in reacting to the tragedy. The severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection targets most of the respiratory tract, resulting in a severe sickness called acute respiratory distress syndrome that may be fatal in some individuals. Although the lung is the primary organ targeted by COVID-19 viruses, the clinical aspect of the disease is varied and ranges from asymptomatic to respiratory failure. However, due to an unorganized immune response and several affected mechanisms, the liver may also experience liver cell injury, ischemic liver dysfunction, and drug-induced liver injury, which can result in respiratory failure because of the immune system's disordered response and other compromised processes that can end in multisystem organ failure. Patients with liver cirrhosis or those who have impaired immune systems may be more likely than other groups to experience worse results from the SARS-CoV-2 infection. We thus intend to examine the pathogenesis, current therapy, and consequences of liver damage concerning COVID-19.

Alterations in gene expression and microbiome composition upon calcium-sensing receptor deletion in the mouse esophagus

The calcium-sensing receptor (CaSR), a G protein-coupled receptor, regulates Ca2+ concentration in plasma by regulating parathyroid hormone secretion. In other tissues, it is reported to play roles in cellular differentiation and migration and in secretion and absorption. We reported previously that CaSR can be conditionally deleted in the mouse esophagus. This conditional knockout (KO) (EsoCaSR-/-) model showed a significant reduction in the levels of adherens and tight junction proteins and had a marked buildup of bacteria on the luminal esophageal surface. To further examine the role of CaSR, we used RNA sequencing to determine gene expression profiles in esophageal epithelia of control and EsoCaSR-/-mice RNA Seq data indicated upregulation of gene sets involved in DNA replication and cell cycle in EsoCaSR-/-. This is accompanied by the downregulation of gene sets involved in the innate immune response and protein homeostasis including peptide elongation and protein trafficking. Ingenuity pathway analysis (IPA) demonstrated that these genes are mapped to important biological networks including calcium and Ras homologus A (RhoA) signaling pathways. To further explore the bacterial buildup in EsoCaSR-/- esophageal tissue, 16S sequencing of the mucosal-associated bacterial microbiome was performed. Three bacterial species, g_Rodentibacter, s_Rodentibacter_unclassified, and s_Lactobacillus_hilgardi were significantly increased in EsoCaSR-/-. Furthermore, metagenomic analysis of 16S sequences indicated that pathways related to oxidative phosphorylation and metabolism were downregulated in EsoCaSR-/- tissues. These data demonstrate that CaSR impacts major pathways of cell proliferation, differentiation, cell cycle, and innate immune response in esophageal epithelium. The disruption of these pathways causes inflammation and significant modifications of the microbiome.NEW & NOTEWORTHY Calcium-sensing receptor (CaSR) plays a significant role in maintaining the barrier function of esophageal epithelium. Using RNA sequencing, we show that conditional deletion of CaSR from mouse esophagus causes upregulation of genes involved in DNA replication and cell cycle and downregulation of genes involved in the innate immune response, protein translation, and cellular protein synthesis. Pathway analysis shows disruption of signaling pathways of calcium and actin cytoskeleton. These changes caused inflammation and esophageal dysbiosis.

Downregulation of chemokine receptor 9 facilitates CD4+CD8αα+ intraepithelial lymphocyte development

Intestinal intraepithelial lymphocytes (IELs) reside in the gut epithelial layer, where they help in maintaining intestinal homeostasis. Peripheral CD4+ T cells can develop into CD4+CD8αα+ IELs upon arrival at the gut epithelium via the lamina propria (LP). Although this specific differentiation of T cells is well established, the mechanisms preventing it from occurring in the LP remain unclear. Here, we show that chemokine receptor 9 (CCR9) expression is low in epithelial CD4+CD8αα+ IELs, but CCR9 deficiency results in CD4+CD8αα+ over-differentiation in both the epithelium and the LP. Single-cell RNA sequencing shows an enriched precursor cell cluster for CD4+CD8αα+ IELs in Ccr9-/- mice. CD4+ T cells isolated from the epithelium of Ccr9-/- mice also display increased expression of Cbfβ2, and the genomic occupancy modification of Cbfβ2 expression reveals its important function in CD4+CD8αα+ differentiation. These results implicate a link between CCR9 downregulation and Cbfb2 splicing upregulation to enhance CD4+CD8αα+ IEL differentiation.

Impact of COVID-19 in individuals with and without pre-existent digestive disorders with a particular focus on elderly patients

Coronavirus disease 2019 (COVID-19) has several extrapulmonary symptoms. Gastrointestinal (GI) symptoms are among the most frequent clinical manifestations of COVID-19, with severe consequences reported in elderly patients. Furthermore, the impact of COVID-19 on patients with pre-existing digestive diseases still needs to be fully elucidated, particularly in the older population. This review aimed to investigate the impact of COVID-19 on the GI tract, liver, and pancreas in individuals with and without previous digestive diseases, with a particular focus on the elderly, highlighting the distinctive characteristics observed in this population. Finally, the effectiveness and adverse events of the anti-COVID-19 vaccination in patients with digestive disorders and the peculiarities found in the elderly are discussed.

Mechanisms of gastrointestinal barrier dysfunction in COVID-19 patients

Coronavirus disease 2019 (COVID-19) caused by the novel severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a major global public health event, resulting in a significant social and economic burden. Although COVID-19 was initially characterized as an upper respiratory and pulmonary infection, recent evidence suggests that it is a complex disease including gastrointestinal symptoms, such as diarrhea, nausea, and vomiting. Moreover, it remains unclear whether the gastrointestinal symptoms are caused by direct infection of the gastrointestinal tract by SARS-CoV-2 or are the result of systemic immune activation and subsequent dysregulation of homeostatic mechanisms. This review provides a brief overview of the mechanisms by which SARS-CoV-2 disrupts the integrity of the gastrointestinal barrier including the mechanical barrier, chemical barrier, microbial barrier, and immune barrier.

Determination of the Binding Epitope of an Anti-Mouse CCR9 Monoclonal Antibody (C9Mab-24) Using the 1× Alanine and 2× Alanine-Substitution Method

C-C chemokine receptor 9 (CCR9) is a receptor for C-C-chemokine ligand 25 (CCL25). CCR9 is crucial in the chemotaxis of immune cells and inflammatory responses. Moreover, CCR9 is highly expressed in tumors, including several solid tumors and T-cell acute lymphoblastic leukemia. Several preclinical studies have shown that anti-CCR9 monoclonal antibodies (mAbs) exert antitumor activity. Therefore, CCR9 is an attractive target for tumor therapy. In this study, we conducted the epitope mapping of an anti-mouse CCR9 (mCCR9) mAb, C₉Mab-24 (rat IgG_2a, kappa), using the 1× alanine (1× Ala)- and 2× alanine (2× Ala)-substitution methods via enzyme-linked immunosorbent assay. We first performed the 1× Ala-substitution method using one alanine-substituted peptides of the mCCR9 N-terminus (amino acids 1-19). C₉Mab-24 did not recognize two peptides (F14A and F17A), indicating that Phe14 and Phe17 are critical for C₉Mab-24-binding to mCCR9. Furthermore, we conducted the 2× Ala-substitution method using two consecutive alanine-substituted peptides of the mCCR9 N-terminus, and showed that C₉Mab-24 did not react with four peptides (M13A-F14A, F14A-D15A, D16A-F17A, and F17A-S18A), indicating that _13-MFDDFS_-18 is involved in C₉Mab-24-binding to mCCR9. Overall, combining, the 1× Ala- or 2× Ala-scanning methods could be useful for understanding for target-antibody interaction.

Gastrointestinal Involvement in SARS-CoV-2 Infection

SARS-CoV-2 has evolved into a virus that primarily results in mild or asymptomatic disease, making its transmission more challenging to control. In addition to the respiratory tract, SARS-CoV-2 also infects the digestive tract. Some gastrointestinal symptoms occur with or before respiratory symptoms in patients with COVID-19. Respiratory infections are known to cause intestinal immune impairment and gastrointestinal symptoms. When the intestine is inflamed, cytokines affect the lung immune response and inflammation through blood circulation. The gastrointestinal microbiome may be a modifiable factor in determining the risk of SARS-CoV-2 infection and disease severity. The development of oral SARS-CoV-2 vaccine candidates and the maintenance of gut microbiota profiles may contribute to the early control of COVID-19 outbreaks. To this end, this review summarizes information on the gastrointestinal complications caused by SARS-CoV-2, SARS-CoV-2 infection, the gastrointestinal–lung axis immune response, potential control strategies for oral vaccine candidates and maintaining intestinal microbiota homeostasis.

COVID-19: Gastrointestinal manifestations, liver injury and recommendations

Coronavirus disease 2019 (COVID-19) has caused a pandemic that affected all countries with nearly 270 million patients and 5 million deaths, as of as of December, 2021. The severe acute respiratory syndrome coronavirus 2 virus targets the receptor, angiotensin-converting enzyme 2, which is frequently found in human intestinal epithelial cells, bile duct epithelial cells, and liver cells, and all gastrointestinal system organs are affected by COVID-19 infection. The aim of this study is to review the gastrointestinal manifestations and liver damage of COVID-19 infection and investigate the severe COVID-19 infection risk in patients that have chronic gastrointestinal disease, along with current treatment guidelines. A literature search was conducted on electronic databases of PubMed, Scopus, and Cochran Library, consisting of COVID-19, liver injury, gastrointestinal system findings, and treatment. Liver and intestinal involvements are the most common manifestations. Diarrhea, anorexia, nausea/vomiting, abdominal pain are the most frequent symptoms seen in intestinal involvement. Mild hepatitis occurs with elevated levels of transaminases. Gastrointestinal involvement is associated with long hospital stay, severity of the disease, and intensive care unit necessity. Treatments and follow-up of patients with inflammatory bowel diseases, cirrhosis, hepatocellular carcinoma, or liver transplant have been negatively affected during the pandemic. Patients with cirrhosis, hepatocellular carcinoma, auto-immune diseases, or liver transplantation may have a greater risk for severe COVID-19. Diagnostic or therapeutic procedures should be restricted with specific conditions. Telemedicine should be used in non-urgent periodic patient follow up. COVID-19 treatment should not be delayed in patients at the risk group. COVID-19 vaccination should be prioritized in this group.

Epitope Mapping of an Anti-Human CCR9 Monoclonal Antibody (C9Mab-1) Using Enzyme-Linked Immunosorbent Assay

One of G protein-coupled receptors, CCR9, is mainly expressed in the thymocytes and the small bowel. The ligand of CCR9 is CCL25 (TECK), and the CCR9-CCL25 axis controls T cell maturation and intestinal immune response. CCR9 is related to graft-versus-host disease and autoimmune diseases. Recent studies have been reported that CCR9 is also associated with tumor proliferation, apoptosis, migration, and drug resistance. Therefore, CCR9-targeting therapy is receiving a lot of attention. Previously, we developed an anti-human CCR9 (hCCR9) monoclonal antibody, C₉Mab-1 (IgG₁, kappa), which can be used for flow cytometry, by immunizing mice with hCCR9-overexpressed Chinese hamster ovary-K1 cells. In this study, we examined the critical epitope of C₉Mab-1, using enzyme-linked immunosorbent assay (ELISA) with synthesized peptides. First, we performed ELISA with deletion mutants, and C₉Mab-1 reacted to the 1-20 amino acids sequence of hCCR9. Next, we analyzed the reaction to 20 point mutants, and C₉Mab-1 did not recognize the alanine-substituted peptides of I10A, P11A, N12A, M13A, A14G, D16A, and Y17A. The results indicate that the binding epitope of C₉Mab-1 includes Ile10, Pro11, Asn12, Met13, Ala14, Asp16, and Tyr17 of hCCR9.

COVID-19 genetic risk variants are associated with expression of multiple genes in diverse immune cell types

Common genetic polymorphisms associated with COVID-19 illness can be utilized for discovering molecular pathways and cell types driving disease pathogenesis. Given the importance of immune cells in the pathogenesis of COVID-19 illness, here we assessed the effects of COVID-19-risk variants on gene expression in a wide range of immune cell types. Transcriptome-wide association study and colocalization analysis revealed putative causal genes and the specific immune cell types where gene expression is most influenced by COVID-19-risk variants. Notable examples include OAS1 in non-classical monocytes, DTX1 in B cells, IL10RB in NK cells, CXCR6 in follicular helper T cells, CCR9 in regulatory T cells and ARL17A in TH2 cells. By analysis of transposase accessible chromatin and H3K27ac-based chromatin-interaction maps of immune cell types, we prioritized potentially functional COVID-19-risk variants. Our study highlights the potential of COVID-19 genetic risk variants to impact the function of diverse immune cell types and influence severe disease manifestations.

Clinical Features and Pathophysiological Mechanisms of COVID-19-associated Gastrointestinal Manifestations

Aim and objective

According to the literature, gastrointestinal (GI) involvement may have a remarkable influence on the course of coronavirus disease-2019 (COVID-19). Our aim with this article is to appraise clinical characteristics and presumptive biological mechanisms of digestive tract involvement of COVID-19.

Background

In this review article, the English language literature was reviewed by using PubMed and MEDLINE databases, up to February 2021.

Review results

The patients with GI involvement are generally presented with diarrhea, nausea/vomiting, anorexia, abdominal pain, and rarely GI bleeding. However, frequencies of these manifestations are diverse in studies published so far, depending on the countries where the studies were conducted, characteristics of the study populations, and methodological differences. Several studies proved that this novel coronavirus gets into the enterocytes by attaching to angiotensin-converting enzyme 2 receptor. Some of them have shown a direct viral invasion and replication of the virus within enterocytes. Along with detection of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) in patients' fecal materials, all these results explicitly indicate that the virus has the capability to invade the GI system. These findings may represent a potential risk indicator for fecal-oral spread of the virus. Although pathophysiology of COVID-19 associated GI manifestations remains elusive, direct viral damage, dysfunction in renin-angiotensin-aldosterone system, effects of gut-lung axis, and GI tract microbiome dysbiosis have been proposed as culprit mechanisms of the GI symptoms and inflammatory response.

Conclusion

The patients with COVID-19 can be presented with diverse clinical manifestations including the GI symptoms. Understanding the actual impact of the virus on the GI tract depends on uncovering the pathophysiology of COVID-19.

Clinical significance

GI involvement of COVID-19 appears to be crucial not only for its clinical consequences but also for its impacts on public health and prevention.

How to cite this article

Aslan AT, Şimşek H. Clinical Features and Pathophysiological Mechanisms of COVID-19-associated Gastrointestinal Manifestations. Euroasian J Hepato-Gastroenterol 2021;11(2):81-86.

Dissecting the contribution of single nucleotide polymorphisms in CCR9 and CCL25 genomic regions to the celiac disease phenotype

PURPOSE AND OBJECTIVES

Given their role in homing immune cells to the intestine, CC motif chemokine receptor 9 (CCR9) and its specific ligand CC motif chemokine ligand 25 (CCL25) are interesting candidate genes for celiac disease. These genes are located in regions previously shown to be associated with or linked to celiac disease, but no investigations on their association with various celiac disease phenotypes have so far been conducted. Here we studied such associations of both genotyped and imputed single nucleotide polymorphisms (SNPs) with either regulatory function or exonic location of the CCR9 and CCL25 loci.

RESULTS

Exploiting a carefully phenotyped cohort of 625 celiac disease patients and 1817 non-celiac controls, we identified that multiple SNPs with predicted regulatory function (RegulomeDB score ≤3a and/or eQTL effect) located between 100 kB upstream and downstream of CCR9 and CCL25 are associated with celiac disease and/or selected phenotypes. Of the genotyped SNPs in the CCR9 loci, rs213360 with an eQTL effect on CCR9 expression in blood was associated with celiac disease and all investigated phenotypes except high HLA risk. Rs1545985 with an eQTL on CCR9 expression and rs7652331 and rs12493471, both with RegulomeDB score ≤3a, were all associated with gastrointestinal symptoms and malabsorption and the latter additionally with anemia. The genotyped CCL25 SNPs rs952444 and rs882951, with RegulomeDB scores 1d and 1f respectively and eQTL effect on CCL25 expression in small intestine, were associated with gastrointestinal symptoms and malabsorption. The CCL25 SNP rs2303165 identified in sequencing followed by imputation was associated with partial villous atrophy. However, the association did not pass the permutation based multiple testing correction (PEMP2 > 0.05).

CONCLUSIONS

We conclude that SNPs in the region of CCR9 and CCL25 with predicted functional effect or exonic localization likely contribute only modestly to various celiac disease phenotypes.

The Effect of Phenotype and Genotype on the Plasma Proteome in Patients with Inflammatory Bowel Disease

BACKGROUND AND AIMS

Protein profiling in patients with inflammatory bowel diseases [IBD] for diagnostic and therapeutic purposes is underexplored. This study analysed the association between phenotype, genotype, and the plasma proteome in IBD.

METHODS

A total of 92 inflammation-related proteins were quantified in plasma of 1028 patients with IBD (567 Crohn's disease [CD]; 461 ulcerative colitis [UC]) and 148 healthy individuals to assess protein-phenotype associations. Corresponding whole-exome sequencing and global screening array data of 919 patients with IBD were included to analyse the effect of genetics on protein levels (protein quantitative trait loci [pQTL] analysis). Intestinal mucosal RNA sequencing and faecal metagenomic data were used for complementary analyses.

RESULTS

Thirty-two proteins were differentially abundant between IBD and healthy individuals, of which 22 proteins were independent of active inflammation; 69 proteins were associated with 15 demographic and clinical factors. Fibroblast growth factor-19 levels were decreased in CD patients with ileal disease or a history of ileocecal resection. Thirteen novel cis-pQTLs were identified and 10 replicated from previous studies. One trans-pQTL of the fucosyltransferase 2 [FUT2] gene [rs602662] and two independent cis-pQTLs of C-C motif chemokine 25 [CCL25] affected plasma CCL25 levels. Intestinal gene expression data revealed an overlapping cis-expression [e]QTL-variant [rs3745387] of the CCL25 gene. The FUT2 rs602662 trans-pQTL was associated with reduced abundances of faecal butyrate-producing bacteria.

CONCLUSIONS

This study shows that genotype and multiple disease phenotypes strongly associate with the plasma inflammatory proteome in IBD, and identifies disease-associated pathways that may help to improve disease management in the future.

The Roles of CCR9/CCL25 in Inflammation and Inflammation-Associated Diseases

Chemokine is a structure-related protein with a relatively small molecular weight, which can target cells to chemotaxis and promote inflammatory response. Inflammation plays an important role in aging. C-C chemokine receptor 9 (CCR9) and its ligand C-C chemokine ligand 25 (CCL25) are involved in the regulating the occurrence and development of various diseases, which has become a research hotspot. Early research analysis of CCR9-deficient mouse models also confirmed various physiological functions of this chemokine in inflammatory responses. Moreover, CCR9/CCL25 has been shown to play an important role in a variety of inflammation-related diseases, such as cardiovascular disease (CVD), rheumatoid arthritis, hepatitis, inflammatory bowel disease, asthma, etc. Therefore, the purpose of this review gives an overview of the recent advances in understanding the roles of CCR9/CCL25 in inflammation and inflammation-associated diseases, which will contribute to the design of future experimental studies on the potential of CCR9/CCL25 and advance the research of CCR9/CCL25 as pharmacological inflammatory targets.

Gastrointestinal and hepatic diseases during the COVID-19 pandemic: Manifestations, mechanism and management

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is considered the causative pathogen of coronavirus disease 2019 (COVID-19) and has become an international danger to human health. Although respiratory transmission and symptoms are still the essential manifestations of COVID-19, the digestive system could be an unconventional or supplementary route for COVID-19 to be transmitted and manifested, most likely due to the presence of angiotensin-converting enzyme 2 (ACE2) in the gastrointestinal tract. In addition, SARS-CoV-2 can trigger hepatic injury via direct binding to the ACE2 receptor in cholangiocytes, antibody-dependent enhancement of infection, systemic inflammatory response syndrome, inflammatory cytokine storms, ischemia/reperfusion injury, and adverse events of treatment drugs. Gastrointestinal symptoms, including anorexia, nausea, vomiting, and diarrhea, which are unusual in patients with COVID-19, and some digestive signs may occur without other respiratory symptoms. Furthermore, SARS-CoV-2 can be found in infected patients' stool, demonstrating the likelihood of transmission through the fecal-oral route. In addition, liver function should be monitored during COVID-19, particularly in more severe cases. This review summarizes the evidence for extra-pulmonary manifestations, mechanisms, and management of COVID-19, particularly those related to the gastrointestinal tract and liver.

Physiological Functions of Threonine in Animals: Beyond Nutrition Metabolism

Threonine (Thr), an essential amino acid for animals and the limiting amino acid in swine and poultry diets, which plays a vital role in the modulation of nutritional metabolism, macromolecular biosynthesis, and gut homeostasis. Current evidence supports that the supplementation of Thr leads to benefits in terms of energy metabolism. Threonine is not only an important component of gastrointestinal mucin, but also acts as a nutritional modulator that influences the intestinal immune system via complex signaling networks, particularly mitogen-activated protein kinase (MAPK) and the target of the rapamycin (TOR) signal pathway. Threonine is also recognized as an indispensable nutrient for cell growth and proliferation. Hence, optimization of Thr requirement may exert a favorable impact on the factors linked to health and diseases in animals. This review focuses on the latest reports of Thr in metabolic pathways and nutritional regulation, as well as the relationship between Thr and relevant physiological functions.

Transcriptome Analysis of CCR9+ T Helper Cells From Primary Sjögren's Syndrome Patients Identifies CCL5 as a Novel Effector Molecule

Introduction

CCR9+ Tfh-like pathogenic T helper (Th) cells are elevated in patients with primary Sjögren’s syndrome (pSS) and indicated to play a role in pSS immunopathology. Here we delineate the CCR9+ Th cell-specific transcriptome to study the molecular dysregulation of these cells in pSS patients.

Methods

CCR9+, CXCR5+ and CCR9-CXCR5- Th cells from blood of 7 healthy controls (HC) and 7 pSS patients were FACS sorted and RNA sequencing was performed. Computational analysis was used to identify differentially expressed genes (DEGs), coherent gene expression networks and differentially regulated pathways. Target genes were replicated in additional cohorts.

Results

5131 genes were differentially expressed between CCR9+ and CXCR5+ Th cells; 6493 and 4783 between CCR9+ and CCR9-CXCR5- and between CXCR5+ and CCR9-CXCR5-, respectively. In the CCR9+ Th cell subset 2777 DEGs were identified between HC and pSS patients, 1416 and 1077 in the CXCR5+ and CCR9-CXCR5- subsets, respectively. One gene network was selected based on eigengene expression differences between the Th cell subsets and pathways enriched for genes involved in migration and adhesion, cytokine and chemokine production. Selected DEGs of interest (HOPX, SOX4, ITGAE, ITGA1, NCR3, ABCB1, C3AR1, NT5E, CCR5 and CCL5) from this module were validated and found upregulated in blood CCR9+ Th cells, but were similarly expressed in HC and pSS patients. Increased frequencies of CCR9+ Th cells were shown to express higher levels of CCL5 than CXCR5+ and CCR9-CXCR5- Th cells, with the highest expression confined to effector CCR9+ Th cells. Antigenic triggering and stimulation with IL-7 of the Th cell subsets co-cultured with monocytes strongly induced CCL5 secretion in CCR9+ Th cell cocultures. Additionally, effector CCR9+ Th cells rapidly released CCL5 and secreted the highest CCL5 levels upon stimulation.

Conclusion

Transcriptomic analysis of circulating CCR9+ Th cells reveals CCR9-specific pathways involved in effector T cell function equally expressed in pSS patients and HC. Given the increased numbers of CCR9+ Th cells in the blood and inflamed glands of pSS patients and presence of inflammatory stimuli to activate these cells this suggests that CCR9-specific functions, such as cell recruitment upon CCL5 secretion, could significantly contribute to immunopathology in pSS.

Tissue-Resident T Cells in Chronic Relapsing-Remitting Intestinal Disorders

Tissue-resident memory T (TRM) cells critically contribute to the rapid immunoprotection and efficient immunosurveillance against pathogens, particularly in barrier tissues, but also during anti-tumor responses. However, the involvement of TRM cells also in the induction and exacerbation of immunopathologies, notably in chronically relapsing auto-inflammatory disorders, is becoming increasingly recognized as a critical factor. Thus, TRM cells may also represent an attractive target in the management of chronic (auto-) inflammatory disorders, including multiple sclerosis, rheumatoid arthritis, celiac disease and inflammatory bowel diseases. In this review, we focus on current concepts of TRM cell biology, particularly in the intestine, and discuss recent findings on their involvement in chronic relapsing-remitting inflammatory disorders. Potential therapeutic strategies to interfere with these TRM cell-mediated immunopathologies are discussed.

Global prevalence of prolonged gastrointestinal symptoms in COVID-19 survivors and potential pathogenesis: A systematic review and meta-analysis

Background: This study aimed to determine the cumulative prevalence of prolonged gastrointestinal (GI) symptoms, including nausea, vomiting, diarrhea, lack of appetite, abdominal pain, and dysgeusia, in survivors of both mild and severe COVID-19 worldwide and to discuss the potential pathogenesis.   Methods: Three databases (PubMed, Scopus, and Web of Science) were searched for relevant articles up to January 30, 2021. Data on study characteristics, clinical characteristics during follow-up, the number of patients with prolonged GI symptoms, and total number of COVID-19 survivors were retrieved according to PRISMA guidelines. The quality of eligible studies was assessed using the Newcastle-Ottawa scale. The pooled prevalence of specific prolonged GI symptoms was calculated and the association between COVID-19 severity and the occurrence of prolonged GI symptoms was assessed if appropriate.   Results: The global prevalence of prolonged nausea was 3.23% (95% CI: 0.54%-16.53%) among 527 COVID-19 survivors. Vomiting persisted in 93 of 2,238 COVID-19 survivors (3.19%, 95% CI: 1.62%-6.17%) and prolonged diarrhea was found in 34 of 1,073 survivors (4.12%, 95% CI: 1.07%-14.64%). A total of 156 patients among 2,238 COVID-19 survivors (4.41%, 95% CI: 1.91%-9.94%) complained of persistent decreased or loss of appetite. The cumulative prevalence of prolonged abdominal pain was 1.68% (95% CI: 0.84%-3.32%), whereas persistent dysgeusia was identified in 130 cases among 1,887 COVID-19 survivors (7.04%, 95% CI: 5.96%-8.30%). Data was insufficient to assess the relationship between COVID-19 severity and the occurrence of all prolonged GI symptoms.   Conclusion: Persistent GI symptoms among COVID-19 survivors after discharge or recovery raises a concern regarding the long-term impact of the COVID-19 infection on the quality of life of the survivors. Despite several potential explanations proposed, studies that aim to follow patients after recovery from COVID-19 and determine the pathogenesis of the prolonged symptoms of COVID-19 survivors are warranted.   PROSPERO registration: CRD42021239187.

CCL25 and CCR9 is a unique pathway that potentiates pannus formation by remodeling RA macrophages into mature osteoclasts

This study elucidates the mechanism of CCL25 and CCR9 in rheumatoid arthritis (RA). RA synovial fluid (SF) expresses elevated levels of CCL25 compared to OA SF and plasma from RA and normal. CCL25 was released into RA SF by fibroblasts (FLS) and macrophages (MΦs) stimulated with IL-1β and IL-6. CCR9 is also presented on IL-1β and IL-6 activated RA FLS and differentiated MΦs. Conversely, in RA PBMCs neither CCL25 nor CCR9 are impacted by 3-month longitudinal TNF inhibitor therapy. CCL25 amplifies RA FLS and monocyte infiltration via p38 and ERK phosphorylation. CCL25-stimulated RA FLS secrete potentiated levels of IL-8 which is disrupted by p38 and ERK inhibitors. CCL25 polarizes RA monocytes into nontraditional M1 MΦs that produce IL-8 and CCL2. Activation of p38 and ERK cascades are also responsible for the CCL25-induced M1 MΦ development. Unexpectedly, CCL25 was unable to polarize RA PBMCs into effector Th1/Th17 cells. Consistently, lymphokine like RANKL was uninvolved in CCL25-induced osteoclastogenesis; however, this manifestation was regulated by osteoclastic factors such as RANK, cathepsin K (CTSK), and TNF-α. In short, we reveal that CCL25/CCR9 manipulates RA FLS and MΦ migration and inflammatory phenotype in addition to osteoclast formation via p38 and ERK activation.

Natural Killer Cell Integrins and Their Functions in Tissue Residency

Integrins are transmembrane receptors associated with adhesion and migration and are often highly differentially expressed receptors amongst natural killer cell subsets in microenvironments. Tissue resident natural killer cells are frequently defined by their differential integrin expression compared to other NK cell subsets, and integrins can further localize tissue resident NK cells to tissue microenvironments. As such, integrins play important roles in both the phenotypic and functional identity of NK cell subsets. Here we review the expression of integrin subtypes on NK cells and NK cell subsets with the goal of better understanding how integrin selection can dictate tissue residency and mediate function from the nanoscale to the tissue environment.

Opportunities to Target T Cell Trafficking in Pediatric Inflammatory Bowel Disease

T cell subsets are considered central orchestrators of inflammation and homeostasis in the intestine and are established targets for the treatment of inflammatory bowel disease. While approaches aimed at the neutralization of T cell effector cytokines have provided significant benefits for pediatric and adult patients, more recent strategies aimed at inhibiting the infiltration of pathogenic T cell subsets have also emerged. In this review, we describe current knowledge surrounding the function of T cell subsets in pediatric inflammatory bowel disease and outline approaches aimed at targeting T cell trafficking to the intestine which may represent a new treatment option for pediatric inflammatory bowel disease.

Recent advances upper gastrointestinal lymphomas: molecular updates and diagnostic implications

Approximately one-third of extranodal non-Hodgkin lymphomas involve the gastrointestinal (GI) tract, with the vast majority being diagnosed in the stomach, duodenum, or proximal small intestine. A few entities, especially diffuse large B-cell lymphoma and extranodal marginal zone lymphoma of mucosa-associated lymphoid tissue, represent the majority of cases. In addition, there are diseases specific to or characteristic of the GI tract, and any type of systemic lymphoma can present in or disseminate to these organs. The recent advances in the genetic and molecular characterisation of lymphoid neoplasms have translated into notable changes in the classification of primary GI T-cell neoplasms and the recommended diagnostic approach to aggressive B-cell tumours. In many instances, diagnoses rely on morphology and immunophenotype, but there is an increasing need to incorporate molecular genetic markers. Moreover, it is also important to take into consideration the endoscopic and clinical presentations. This review gives an update on the most recent developments in the pathology and molecular pathology of upper GI lymphoproliferative diseases.

Advances in Oral Subunit Vaccine Design

Many pathogens invade the host at the intestinal surface. To protect against these enteropathogens, the induction of intestinal secretory IgA (SIgA) responses is paramount. While systemic vaccination provides strong systemic immune responses, oral vaccination is the most efficient way to trigger protective SIgA responses. However, the development of oral vaccines, especially oral subunit vaccines, is challenging due to mechanisms inherent to the gut. Oral vaccines need to survive the harsh environment in the gastrointestinal tract, characterized by low pH and intestinal proteases and need to reach the gut-associated lymphoid tissues, which are protected by chemical and physical barriers that prevent efficient uptake. Furthermore, they need to surmount default tolerogenic responses present in the gut, resulting in suppression of immunity or tolerance. Several strategies have been developed to tackle these hurdles, such as delivery systems that protect vaccine antigens from degradation, strong mucosal adjuvants that induce robust immune responses and targeting approaches that aim to selectively deliver vaccine antigens towards specific immune cell populations. In this review, we discuss recent advances in oral vaccine design to enable the induction of robust gut immunity and highlight that the development of next generation oral subunit vaccines will require approaches that combines these solutions.

Probabilistic Estimation of Identity by Descent Segment Endpoints and Detection of Recent Selection

Most methods for fast detection of identity by descent (IBD) segments report identity by state segments without any quantification of the uncertainty in the endpoints and lengths of the IBD segments. We present a method for determining the posterior probability distribution of IBD segment endpoints. Our approach accounts for genotype errors, recent mutations, and gene conversions which disrupt DNA sequence identity within IBD segments, and it can be applied to large cohorts with whole-genome sequence or SNP array data. We find that our method's estimates of uncertainty are well calibrated for homogeneous samples. We quantify endpoint uncertainty for 77.7 billion IBD segments from 408,883 individuals of white British ancestry in the UK Biobank, and we use these IBD segments to find regions showing evidence of recent natural selection. We show that many spurious selection signals are eliminated by the use of unbiased estimates of IBD segment endpoints and a pedigree-based genetic map. Eleven of the twelve regions with the greatest evidence for recent selection in our scan have been identified as selected in previous analyses using different approaches. Our computationally efficient method for quantifying IBD segment endpoint uncertainty is implemented in the open source ibd-ends software package.

Recent advances in roles of G-protein coupled receptors in intestinal intraepithelial lymphocytes

Intestinal intraepithelial lymphocytes (IELs) potentially provide the first line of immune defense against enteric pathogens. In addition, there is growing evidence supporting the involvement of IELs in the pathogenesis of gut disorders such as inflammatory bowel diseases. Various kinds of molecules are involved in the dynamics of IELs, such as homing to the intestinal epithelium and retention in the intestinal mucosa. G protein-coupled receptors (GPCRs) comprise the largest family of cell surface receptors and regulate many biological responses. Although some GPCRs, like CCR9, have been implicated to have roles in IEL homing, little is still known regarding the functional roles of GPCRs in IEL biology. In this review, we provide a concise overview of recent advances in the roles of novel GPCRs like GPR55 and GPR18 in the dynamics of IELs.

The mechanism and treatment of gastrointestinal symptoms in patients with COVID-19

In addition to the typical respiratory response, new coronavirus disease 2019 (COVID-19) is also associated with very common gastrointestinal symptoms. Cases with gastrointestinal symptoms are more likely to be complicated by liver injury and acute respiratory distress syndrome (ARDS). If not treated in time, coma and circulatory failure may ensue. As severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infects the human body through the combination of angiotensin-converting enzyme 2 (ACE2) in the gastrointestinal tract, the mechanism underlying the gastrointestinal symptoms may involve damage to the intestinal mucosal barrier and promotion of the production of inflammatory factors. Indeed, after cells in the lungs become infected by SARS-CoV-2, effector CD4+ T cells reach the small intestine through the gut-lung axis, causing intestinal immune damage and diarrhea; early extensive use of antibacterial and antiviral drugs can also lead to diarrhea in patients. Thus, treatment options for COVID-19 patients should be promptly adjusted when they have gastrointestinal symptoms. As SARS-CoV-2 has been detected in the feces of COVID-19 patients, future prevention and control efforts must consider the possibility of fecal-oral transmission of the virus.

Immune Cell Trafficking to the Liver

The human liver is an organ with a diverse array of immunologic functions. Its unique anatomic position that leads to it receiving all the mesenteric venous blood, combined with its unique micro anatomy, allows it to serve as a sentinel for the body's immune system. Hepatocytes, biliary epithelial cells, Kupffer cells, stellate cells, and liver sinusoidal endothelial cells express key molecules that recruit and activate innate and adaptive immunity. Additionally, a diverse array of lymphoid and myeloid immune cells resides within and traffics to the liver in specific circumstances. Derangement of these trafficking mechanisms underlies the pathophysiology of autoimmune liver diseases, nonalcoholic steatohepatitis, and liver transplantation. Here, we review these pathways and interactions along with potential targets that have been identified to be exploited for therapeutic purposes.

Transcriptomic analysis of Nibea albiflora skin in response to infection by Cryptocaryon irritans

Massive infection caused by Cryptocaryon irritans is detrimental to the development of marine aquaculture. Recently, our lab found that Nibea albiflora has low sensitivity and low mortality to C. irritans infection. The present study was designed to investigate the mechanisms of the N. albiflora response to C. irritans infection by analyzing transcriptome changes in the skin. Skin samples of control and experimental groups with C. irritans infection were collected at 24 and 72 h (24 h control, 24 h post-infection, 72 h control, and 72 h post-infection). Three parallels were set for each group and sample time, and a total of 12 skin samples were collected for sequencing. Overall, 297,489,843 valid paired-end reads and 48,817 unigenes were obtained with an overall length of 59,010,494 nt. In pairwise comparisons, changes in expression occurred in 1621 (764 upregulated and 857 downregulated), 285 (180 upregulated and 105 downregulated), 993 (489 upregulated and 504 downregulated), and 37 (8 upregulated and 29 downregulated) genes at 24 h control vs 24 h post-infection, 72 h control vs 72 h post-infection, 24 h post-infection vs 72 h post-infection, and 24 h control vs 72 h control, respectively. Gene Ontology (GO) analysis of differentially expressed genes (DEGs) indicated that the number of genes enriched in GO sub-categories were ordered 24 h control vs 24 h post-infection > 24 h post-infection vs 72 h post-infection >72 h control vs 72 h post-infection > 24 h control vs 72 h control. Further analysis showed that immune-related GO terms (including immune system process, complement activation, and humoral immunity) were significantly enriched at both 72 h control vs 72 h post-infection and 24 h post-infection vs 72 h post-infection, but no immune-related GO terms were significantly enriched in the 24 h control vs 72 h control and at 24 h control vs 24 h post-infection, indicating that C. irritans infection mainly affected the physiological metabolism of N. albiflora at an early stage (24 h), and immune-related genes play an important role at a later stage (72 h) of infection. In KEGG pathway analysis, the complement and coagulation cascade pathway are involved in early infection. Hematopoietic cell lineage, natural killer (NK) cell-mediated cytotoxicity, and the intestinal immune network for IgA production are involved in later infection. Further analysis showed that the alternative pathway of complement and coagulation cascades plays an important role in the resistance of N. albiflora to early C. irritans infection. During late infection, CD34, IgM, and IgD were significantly upregulated in the hematopoietic cell lineage pathway. CCR9 was significantly downregulated, and IGH and PIGR were significantly upregulated in the intestinal immune network for IgA production. GZMB and IGH were significantly downregulated in NK cell-mediated cytotoxicity. These findings indicate that acquired immunity at the mRNA level was initiated during later infection. In addition, the IL-17 signaling pathway was enriched by downregulated DEGs at 24 h post-infection vs 72 h post-infection, suggesting the inflammatory response at 24 h was stronger than at 72 h and the invasion of the parasite has a greater impact on the host.

Chemokine-Adjuvanted Plasmid DNA Induces Homing of Antigen-Specific and Non-Antigen-Specific B and T Cells to the Intestinal and Genital Mucosae

Plasmid DNA is a promising vaccine platform that together with electroporation can elicit significant systemic Ab responses; however, immunity at mucosal sites remains low. In this study, we sought to program T and B cells to home to the gastrointestinal and vaginal mucosae using genetic chemokine adjuvants and assessed their impact on immune homeostasis in various distinct immune compartments. BALB/c mice were immunized i.m. with plasmid DNA encoding a model Ag HIV-1 Env gp140 and selected chemokines/cytokine and boosted intravaginally with gp140 recombinant protein. Isolated splenocytes, intestinal lymphocytes, and genital lymphocytes as well as serum and intestinal luminal contents were assessed for Ag-specific reactivity. In addition, flow cytometric analysis was performed to determine the impact on immune homeostasis at these sites. Different molecular chemokine/cytokine adjuvants effected significant alterations to the recruitment of B and T cells to the spleen, vaginal and intestinal mucosae, for example CCL25 enhanced splenic and vaginal Ag-specific T cell responses whereas CCL28 increased the levels of specific T cells only in the vaginal mucosa. The levels of Ab could be modulated in the systemic circulation, as well as the vaginal vault and intestinal lumen, with CCL20 playing a central role. Our data demonstrate that the CCL20, CCL25, and CCL28 genetic chemokine adjuvants enhance the vaccine Ag-specific humoral and cellular responses and induce homing to the intestinal and female genital mucosae.

Dissecting the Heterogeneity in T-Cell Mediated Inflammation in IBD

Infiltration of the lamina propria by inflammatory CD4⁺ T-cell populations is a key characteristic of chronic intestinal inflammation. Memory-phenotype CD4⁺ T-cell frequencies are increased in inflamed intestinal tissue of IBD patients compared to tissue of healthy controls and are associated with disease flares and a more complicated disease course. Therefore, a tightly controlled balance between regulatory and inflammatory CD4⁺ T-cell populations is crucial to prevent uncontrolled CD4⁺ T-cell responses and subsequent intestinal tissue damage. While at steady state, T-cells display mainly a regulatory phenotype, increased in Th1, Th2, Th9, Th17, and Th17.1 responses, and reduced Treg and Tr1 responses have all been suggested to play a role in IBD pathophysiology. However, it is highly unlikely that all these responses are altered in each individual patient. With the rapidly expanding plethora of therapeutic options to inhibit inflammatory T-cell responses and stimulate regulatory T-cell responses, a crucial need is emerging for a robust set of immunological assays to predict and monitor therapeutic success at an individual level. Consequently, it is crucial to differentiate dominant inflammatory and regulatory CD4⁺ T helper responses in patients and relate these to disease course and therapy response. In this review, we provide an overview of how intestinal CD4⁺ T-cell responses arise, discuss the main phenotypes of CD4⁺ T helper responses, and review how they are implicated in IBD.

Intratumoral delivery of CCL25 enhances immunotherapy against triple-negative breast cancer by recruiting CCR9+ T cells

CCR9⁺ T cells have an increased potential to be activated and therefore may mediate strong antitumor responses. Here, we found, however, that CCL25, the only chemokine for CCR9⁺ cells, is not expressed in human or murine triple-negative breast cancers (TNBCs), raising a hypothesis that intratumoral delivery of CCL25 may enhance antitumor immunotherapy in TNBCs. We first determined whether this approach can enhance CD47-targeted immunotherapy using a tumor acidity-responsive nanoparticle delivery system (NP-siCD47/CCL25) to sequentially release CCL25 protein and CD47 small interfering RNA in tumor. NP-siCD47/CCL25 significantly increased infiltration of CCR9⁺CD8⁺ T cells and down-regulated CD47 expression in tumor, resulting in inhibition of tumor growth and metastasis through a T cell-dependent immunity. Furthermore, the antitumor effect of NP-siCD47/CCL25 was synergistically enhanced when used in combination with programmed cell death protein-1/programmed death ligand-1 blockades. This study offers a strategy to enhance immunotherapy by promoting CCR9⁺CD8⁺ T cell tumor infiltration.

Preferential Small Intestine Homing and Persistence of CD8 T Cells in Rhesus Macaques Achieved by Molecularly Engineered Expression of CCR9 and Reduced Ex Vivo Manipulation

Adoptive cell transfer (ACT) is a powerful experimental approach to directly study T-cell-mediated immunity in vivo In the rhesus macaque AIDS virus model, infusing simian immunodeficiency virus (SIV)-infected animals with CD8 T cells engineered to express anti-SIV T-cell receptor specificities enables direct experimentation to better understand antiviral T-cell immunity in vivo Limiting factors in ACT experiments include suboptimal trafficking to, and poor persistence in, the secondary lymphoid tissues targeted by AIDS viruses. Previously, we redirected CD8 T cells to B-cell follicles by ectopic expression of the CXCR5 homing protein. Here, we modify peripheral blood mononuclear cell (PBMC)-derived CD8 T cells to express the CCR9 chemokine receptor, which induces preferential homing of the engineered cells to the small intestine, a site of intense early AIDS virus replication and pathology in rhesus macaques. Additionally, we increase in vivo persistence and overall systemic distribution of infused CD8 T cells, especially in secondary lymphoid tissues, by minimizing ex vivo culture/manipulation, thereby avoiding the loss of CD28+/CD95+ central memory T cells by differentiation in culture. These proof-of-principle results establish the feasibility of preferentially localizing PBMC-derived CD8 T cells to the small intestine and enables the direct experimental ACT-based assessment of the potential role of the quality and timing of effective antiviral CD8 T-cell responses to inhibit viral infection and subsequent replication in small intestine CD4 T cells. More broadly, these results support the engineered expression of homing proteins to direct CD8 T cells to target tissues as a means for both experimental and potential therapeutic advances in T-cell immunotherapies, including cancer.IMPORTANCEAdoptive cell transfer (ACT) of T cells engineered with antigen-specific effector properties can deliver targeted immune responses against malignancies and infectious diseases. Current T-cell-based therapeutic ACT relies on circulatory distribution to deliver engineered T cells to their targets, an approach which has proven effective for some leukemias but provided only limited efficacy against solid tumors. Here, engineered expression of the CCR9 homing receptor redirected CD8 T cells to the small intestine in rhesus macaque ACT experiments. Targeted homing of engineered T-cell immunotherapies holds promise to increase the effectiveness of adoptively transferred cells in both experimental and clinical settings.

Return to sender: Lymphocyte trafficking mechanisms as contributors to primary sclerosing cholangitis

Primary sclerosing cholangitis (PSC) is an inflammatory disease of the biliary tree, characterised by stricturing bile duct disease and progression to liver fibrosis. The pathophysiology of PSC is still unknown. The concurrence with inflammatory bowel disease (IBD) in about 70% of cases has led to the hypothesis that gut-homing lymphocytes aberrantly traffic to the liver, contributing to disease pathogenesis in patients with both PSC and IBD (PSC-IBD). The discovery of mutual trafficking pathways of lymphocytes to target tissues, and expression of gut-specific adhesion molecules and chemokines in the liver has pointed in this direction. There is now increasing interest in using drugs that intervene with these trafficking pathways (e.g. vedolizumab, etrolizumab) for the treatment of PSC-IBD. In this review we discuss what is currently known about the immunological interactions between the gut and the liver in concomitant PSC and IBD, as well as potential therapeutic options for intervening in these mechanisms.

Comparison of the integrin α4β7 expression pattern of memory T cell subsets in HIV infection and ulcerative colitis

Anti-α4β7 therapy with vedolizumab (VDZ) has been suggested as possible immune intervention in HIV. Relatively little is known about the α4β7-integrin (α4β7) expression of different T-cell subsets in different anatomical compartments of healthy individuals, patients with HIV or inflammatory bowel disease (IBD). Surface expression of α4β7 as well as the frequency of activation, homing and exhaustion markers of T cells were assessed by multicolour flow cytometry in healthy volunteers (n = 15) compared to HIV infected patients (n = 52) or patients diagnosed with ulcerative colitis (UC) (n = 14), 6 of whom treated with vedolizumab. In addition, lymph nodal cells (n = 6), gut-derived cells of healthy volunteers (n = 5) and patients with UC (n = 6) were analysed. Additionally, we studied longitudinal PBMC samples of an HIV patient who was treated with vedolizumab for concomitant UC. Overall, only minor variations of the frequency of α4β7 on total CD4⁺ T cells were detectable regardless of the disease status or (VDZ) treatment status in peripheral blood and the studied tissues. Peripheral α4β7⁺ CD4⁺ T cells of healthy individuals and patients with UC showed a higher activation status and were more frequently CCR5⁺ than their α4β7^- counterparts. Also, the frequency of α4β7⁺ cells was significantly lower in peripheral blood CD4⁺ effector memory T cells of HIV-infected compared to healthy individuals and this reduced frequency did not recover in HIV patients on ART. Conversely, the frequency of peripheral blood naïve α4β7⁺ CD4⁺ T cells was significantly reduced under VDZ treatment. The results of the current study will contribute to the understanding of the dynamics of α4β7 expression pattern on T cells in HIV and UC and will be useful for future studies investigating VDZ as possible HIV cure strategy.

The role of integrins in the pathogenesis of inflammatory bowel disease: Approved and investigational anti-integrin therapies

Inflammatory bowel disease (IBD) is characterized by uncontrolled inflammation in the gastrointestinal tract. The underlying pathobiology of IBD includes an increase in infiltrating gut-homing lymphocytes. Although lymphocyte homing is typically a tightly regulated and stepwise process involving multiple integrins and adhesion molecules expressed on endothelial cells, the distinct roles of integrin-expressing immune cells is not fully understood in the pathology of IBD. In this review, we detail the involvement of integrins expressed on specific lymphocyte subsets in the pathogenesis of IBD and discuss the current status of approved and investigational integrin-targeted therapies.

Function and dysfunction of plasma cells in intestine

As the main player in humoral immunity, antibodies play indispensable roles in the body’s immune system. Plasma cells (PCs), as antibody factories, are important contributors to humoral immunity. PCs, recognized by their unique marker CD138, are always discovered in the medullary cords of spleen and lymph nodes and in bone marrow and mucosal lymphoid tissue. This article will review the origin and differentiation of PCs, characteristics of short- and long-lived PCs, and the secretion of antibodies, such as IgA, IgM, and IgG. PCs play a crucial role in the maintenance of intestinal homeostasis using immunomodulation though complex mechanisms. Clearly, PCs play functional roles in maintaining intestinal health, but more details are needed to fully understand all the other effects of intestinal PCs.

The Use of Biologics in Patients with Inflammatory Bowel Disease and Primary Sclerosing Cholangitis

Purpose of Review

Biologics are well established in the treatment of many immuno-inflammatory diseases including inflammatory bowel disease (IBD). However, although primary sclerosing cholangitis (PSC) is closely associated with IBD, the role of biologics in PSC remains uncertain. Many new biologics are becoming available to treat IBD, and this review aims to use the experience of biologics in PSC so far to guide more effective evaluation of emerging therapies in the future.

Recent Findings

Antibodies to TNF-α were the first biologics used in IBD, and retrospective analysis suggests that they may have some benefit in PSC, even though an early randomised controlled trial (RCT) showed no effect. Mechanistic studies suggest that TNF-α may have a pathogenic role in PSC. An antibody to integrin α4β7 is effective in IBD, and there are emerging data on its effects in PSC, although no RCT data are available. Mechanistic studies suggest that interrupting the migration of lymphocytes is relevant in PSC. Two biologics, targeting vascular adhesion protein-1 (VAP-1), and lysyl oxidase-like 2 (LOXL2) have been tested in RCTs. The trial of anti-VAP1 is ongoing, whilst the anti-LOXL2 trial was negative.

Summary

Anti-TNF antibodies may benefit PSC when used to treat concomitant IBD, and this may be a direct effect on the liver in a subgroup of patients, or may be an indirect effect of treating IBD. Similarly, anti-integrin therapy may benefit a subset of patients with IBD and PSC. RCTs could decide the role of emerging biologics in PSC, although future trials should be guided by biomarkers that could predict response to the pathway being targeted.

Emerging roles for chemokines and cytokines as orchestrators of immunopathology in Sjögren's syndrome

In primary SS (pSS), chemokines and cytokines orchestrate immunopathology driven by a complex network of interacting inflammatory cells. In recent years, the importance of chemotactic and non-chemotactic cytokines that control function, movement and placing of all cells within the inflamed exocrine glands and directing immunopathology has become increasingly clear. This paper reviews the current knowledge on chemokines and focuses on the emerging roles of novel chemotactic and non-chemotactic mediators in pSS. It highlights their contribution to pathogenic processes such as B cell hyperactivity and the formation of ectopic lymphoid structures. To this end, the role of acquired (CXCR5/CCR9 Th-cell-mediated) and innate (inflammasome/IL-1/IL-18-mediated) pathways in steering immunopathology is discussed.

A Subset of CCL25-Induced Gut-Homing T Cells Affects Intestinal Immunity to Infection and Cancer

Protective immunity relies upon differentiation of T cells into the appropriate subtype required to clear infections and efficient effector T cell localization to antigen-rich tissue. Recent studies have highlighted the role played by subpopulations of tissue-resident memory (T_RM) T lymphocytes in the protection from invading pathogens. The intestinal mucosa and associated lymphoid tissue are densely populated by a variety of resident lymphocyte populations, including αβ and γδ CD8⁺ intraepithelial T lymphocytes (IELs) and CD4⁺ T cells. While the development of intestinal γδ CD8⁺ IELs has been extensively investigated, the origin and function of intestinal CD4⁺ T cells have not been clarified. We report that CCR9 signals delivered during naïve T cell priming promote the differentiation of a population of α4β7+ IFN-γ-producing memory CD4⁺ T cells, which displays a T_RM molecular signature, preferentially localizes to the gastrointestinal (GI) tract and associated lymphoid tissue and cannot be mobilized by remote antigenic challenge. We further show that this population shapes the immune microenvironment of GI tissue, thus affecting effector immunity in infection and cancer.

Dose-Dependent Effect of Mesenchymal Stromal Cell Recruiting Chemokine CCL25 on Porcine Tissue-Engineered Healthy and Osteoarthritic Cartilage

Thymus-expressed chemokine (CCL25) is a potent cell attractant for mesenchymal stromal cells, and therefore it is a candidate for in situ cartilage repair approaches focusing on the recruitment of endogenous repair cells. However, the influence of CCL25 on cartilage is unknown. Accordingly, in this study, we investigated the effect of CCL25 on tissue-engineered healthy and osteoarthritic cartilage. Porcine chondrocytes were cultured in a three-dimensional (3D) micromass model that has been proven to mimic key-aspects of human cartilage and osteoarthritic alterations upon stimulation with tumor necrosis factor-α (TNF-α). Micromass cultures were stimulated with CCL25 (0, 0.05, 0.5, 5, 50, 500 nmol/L) alone or in combination with 0.6 nmol/L TNF-α for seven days. Effects were evaluated by life/dead staining, safranin O staining, histomorphometrical analysis of glycosaminoglycans (GAGs), collagen type II (COL2A1) real-time RT-PCR and Porcine Genome Array analysis. 500 nmol/L CCL25 led to a significant reduction of GAGs and COL2A1 expression and induced the expression of matrix metallopeptidases (MMP) 1, MMP3, early growth response protein 1 (EGR1), and superoxide dismutase 2 (SOD2). In concentrations lower than 500 nmol/L, CCL25 seems to be a candidate for in situ cartilage repair therapy approaches.

CCL25 chemokine-guided stem cell attraction: an assessment of possible benefits and risks

Due to its chemoattraction potential on mesenchymal stromal cells of the CCL25/CCR9 axis, local application of CCL25 to severely damaged tissues may be a promising approach for regenerative therapies. Analysis of the given data revealed that CCL25/CCR9 signaling has a crucial role in regulation of an adult immune homeostasis. CCR9 expression variations resulted in dysfunctional immune response in colitis, rheumatoid arthritis and endometriosis. Regarding oncology, different neoplastic tissues exploit CCL25-dependent CCR9 signaling for either local proliferation or migration processes. The CCR9 pathway likely can trigger crosstalk between the Akt and NOTCH pathway and thus participate in the regulation of the neoplastic behavior. In conclusion, the designated application-tissue requires precise molecular analysis of possible CCR9 expression due to its proto-oncogenic characteristics.

T Cells That Help B Cells in Chronically Inflamed Tissues

Chronically inflamed tissues commonly accrue lymphocyte aggregates that facilitate local T cell-B cell interactions. These aggregates can range from small, loosely arranged lymphocyte clusters to large, organized ectopic lymphoid structures. In some cases, ectopic lymphoid structures develop germinal centers that house prototypical T follicular helper (Tfh) cells with high expression of Bcl6, CXCR5, PD-1, and ICOS. However, in many chronically inflamed tissues, the T cells that interact with B cells show substantial differences from Tfh cells in their surface phenotypes, migratory capacity, and transcriptional regulation. This review discusses observations from multiple diseases and models in which tissue-infiltrating T cells produce factors associated with B cell help, including IL-21 and the B cell chemoattractant CXCL13, yet vary dramatically in their resemblance to Tfh cells. Particular attention is given to the PD-1^hi CXCR5⁻ Bcl6^low T peripheral helper (Tph) cell population in rheumatoid arthritis, which infiltrates inflamed synovium through expression of chemokine receptors such as CCR2 and augments synovial B cell responses via CXCL13 and IL-21. The factors that regulate CD4⁺ T cell production of CXCL13 and IL-21 in these settings are also discussed. Understanding the range of T cell populations that can provide help to B cells within chronically inflamed tissues is essential to recognize these cells in diverse inflammatory conditions and to optimize either broad or selective therapeutic targeting of B cell-helper T cells.

Chemokines and Chemokine Receptors as Therapeutic Targets in Inflammatory Bowel Disease; Pitfalls and Promise

The principal targets for anti-chemokine therapy in inflammatory bowel disease (IBD) have been the receptors CCR9 and CXCR3 and their respective ligands CCL25 and CXCL10. More recently CCR6 and its ligand CCL20 have also received attention, the expression of the latter in enterocytes being manipulated through Smad7 signalling. These pathways, selected based on their fundamental role in regulating mucosal immunity, have led to the development of several therapeutic candidates that have been tested in early phase clinical trials with variable clinical efficacy. In this article, we appraise the status of chemokine-directed therapy in IBD, review recent developments, and nominate future areas for therapeutic focus.

Analysis of Human Sequence Data Reveals Two Pulses of Archaic Denisovan Admixture

Anatomically modern humans interbred with Neanderthals and with a related archaic population known as Denisovans. Genomes of several Neanderthals and one Denisovan have been sequenced, and these reference genomes have been used to detect introgressed genetic material in present-day human genomes. Segments of introgression also can be detected without use of reference genomes, and doing so can be advantageous for finding introgressed segments that are less closely related to the sequenced archaic genomes. We apply a new reference-free method for detecting archaic introgression to 5,639 whole-genome sequences from Eurasia and Oceania. We find Denisovan ancestry in populations from East and South Asia and Papuans. Denisovan ancestry comprises two components with differing similarity to the sequenced Altai Denisovan individual. This indicates that at least two distinct instances of Denisovan admixture into modern humans occurred, involving Denisovan populations that had different levels of relatedness to the sequenced Altai Denisovan. VIDEO ABSTRACT.

Chemokines and receptors in intestinal B lymphocytes

Recent studies indicate that chemoattractant cytokines (chemokines) and their receptors modulate intestinal B lymphocytes in different ways, including regulating their maturity and differentiation in the bone marrow and homing to intestinal target tissues. Here, we review several important chemokine/chemokine receptor axes that guide intestinal B cells, focusing on the homing and migration of IgA antibody-secreting cells (IgA-ASCs) to intestinal-associated lymphoid tissues. We describe the selective regulation of these chemokine axes in coordinating the IgA-ASC trafficking in intestinal diseases. Finally, we discuss the role of B cells as chemokine producers serving dual roles in regulating the mucosal immune microenvironment.

Mucosal Chemokines

Several chemokines have important functions in mucosal immunity. While there are many chemokines, 4 of them (CCL25, CCL28, CXCL14, and CXCL17) are especially important in mucosal immunity because they are homeostatically expressed in mucosal tissues. Of these, only CCL25 and CCL28 have been widely recognized as mucosal chemokines. In this study, we review the physiology of these chemokines with specific emphasis on their function in mucosal immunity. CCL25 recruits certain important subsets of T cells that express CCR9 to the small intestine. These CCR9⁺ T cells also express the integrin α4β7 and have been shown to play important roles in the control of intestinal inflammation. CCL28 recruits CCR10⁺ IgA plasmablasts to the lactating mammary gland. The role of CXCL14 in mucosal immunity is less well defined, but a Cxcl14^-/- mouse exhibits significant metabolic abnormalities. Finally, CXCL17 was the last chemokine to be described and signals through a new chemokine receptor (GPR35/CXCR8), which is expressed in a subset of macrophages that are recruited to mucosal tissues by this chemokine. We conclude that these 4 chemokines play very important roles in mucosal immunity and their continued functional characterization will likely identify novel therapeutic targets.