Immune cell trafficking and retention in inflammatory bowel disease: mechanistic insights and therapeutic advances

Baseline levels of dynamic CD4+ T cell adhesion to MAdCAM-1 correlate with clinical response to vedolizumab treatment in ulcerative colitis: a cohort study

Background

While the number of therapeutic options for treating inflammatory bowel diseases (IBD) is increasing, evidence for rational treatment decisions is scarce in many cases. In particular, appropriate biomarkers to predict the response to the anti-α4β7 integrin antibody vedolizumab are currently lacking.

Methods

We performed a cohort study with 21 patients suffering from ulcerative colitis (UC), in which first-time treatment with vedolizumab was initiated. CD4⁺ T cells were isolated from the peripheral blood and dynamic adhesion to recombinant mucosal vascular addressin cell adhesion molecule (MAdCAM-)1 in vitro as well as the effect of vedolizumab on such adhesion in vitro was determined. The expression of α4β1 integrin on peripheral blood CD4⁺ T cells was quantified by flow cytometry. Electronic patient records were reviewed to determine clinical response to vedolizumab.

Results

Dynamic adhesion of peripheral blood CD4⁺ T cells to MAdCAM-1 and the reduction of adhesion following vedolizumab treatment in vitro were higher and the change in α4β1 expression on CD4⁺ T cells was different in vedolizumab responders and non-responders. Responders could be identified with high specificity and positive-predictive value.

Conclusions

Determining dynamic adhesion of CD4⁺ T cells to MAdCAM-1 and the in vitro response to vedolizumab before treatment initiation or dynamic integrin regulation in the early course of treatment seem to be promising tools to predict the clinical response to vedolizumab therapy. Larger prospective studies are warranted.

Development of Mucosal PNAd+ and MAdCAM-1+ Venules during Disease Course in Ulcerative Colitis

PNAd and MAdCAM-1 addressins on venules are of importance in T-cell homing and potential therapeutic targets in ulcerative colitis (UC). Normally, PNAd⁺ high endothelial venules (HEVs) are only present in lymphoid organs, whereas small numbers of MAdCAM-1⁺ venules can be seen in non-lymphoid tissue. We aimed to study their presence in the intestinal mucosa of UC patients at diagnosis and during follow-up, and their correlation with disease activity. Colonic biopsy specimens of 378 UC patients were analyzed by immunohistochemistry for CD3, CD20, ERG, MECA-79 (PNAd) and MECA-376 (MAdCAM-1) and compared to healthy controls (HC). The proportion of PNAd⁺HEVs in UC at diagnosis was 4.9% (IQR 2.0%-8.3%), while none were detected in HC. During follow-up, PNAd⁺HEVs completely disappeared in remission (n = 93), whereas the proportion in active disease was similar to baseline (n = 285, p = 0.39). The proportion of MAdCAM-1⁺venules in UC at baseline was 5.8% (IQR 2.6-10.0). During follow-up, the proportion in remission was comparable to diagnosis, but upregulated (7.5% (IQR 4.4-10.9), p = 0.001) in active disease. In conclusion, PNAd⁺HEVs appear in UC during active inflammation which could thus serve as a marker for disease activity, whereas MAdCAM-1⁺venules remain present after inflammation is resolved and increase after subsequent flares, reflecting chronicity and potentially serving as a therapeutic target.

Human Intestinal Mononuclear Phagocytes in Health and Inflammatory Bowel Disease

Inflammatory bowel disease (IBD), including Crohn's disease and ulcerative colitis, is a complex immune-mediated disease of the gastrointestinal tract that increases morbidity and negatively influences the quality of life. Intestinal mononuclear phagocytes (MNPs) have a crucial role in maintaining epithelial barrier integrity while controlling pathogen invasion by activating an appropriate immune response. However, in genetically predisposed individuals, uncontrolled immune activation to intestinal flora is thought to underlie the chronic mucosal inflammation that can ultimately result in IBD. Thus, MNPs are involved in fine-tuning mucosal immune system responsiveness and have a critical role in maintaining homeostasis or, potentially, the emergence of IBD. MNPs include monocytes, macrophages and dendritic cells, which are functionally diverse but highly complementary. Despite their crucial role in maintaining intestinal homeostasis, specific functions of human MNP subsets are poorly understood, especially during diseases such as IBD. Here we review the current understanding of MNP ontogeny, as well as the recently identified human intestinal MNP subsets, and discuss their role in health and IBD.

Immune Cell Circuits in Mucosal Wound Healing: Clinical Implications

Background

An intact mucosal barrier is essential for homeostasis in the gastrointestinal tract. Various pathological conditions such as infection or immune-mediated inflammation as well as therapeutic interventions like bowel surgery can result in injury of the intestinal mucosa. To counteract potential negative sequelae and to restore integrity of the tissue, a tightly regulated machinery of mechanisms exists, which crucially depends on the presence and absence of various immune cell subsets in different phases of intestinal wound healing. Cell trafficking is an increasingly acknowledged process that steers the localization of cells in tissues and the circulation. Thus, such cell circuits also crucially impact on the recruitment of immune cells in wound healing.

Summary

We performed a selective literature research. In our review, we will shortly delineate some basic principles of intestinal immune cell trafficking before discussing the contribution of different immune cells to wound healing. Finally, we will discuss potential clinical implications of immune cell trafficking and wound healing interactions in inflammatory bowel disease (IBD) and bowel surgery.

Key Messages

Intestinal wound healing has immense importance in pathological conditions like IBD, anastomotic healing, and others. Immune cell trafficking is indispensable for the correct temporal and spatial interaction of the cells involved. Further research is required to understand the final consequences of interfering with immune cell trafficking for intestinal wound healing.

Extent of Mucosal Inflammation in Ulcerative Colitis Influences the Clinical Remission Induced by Vedolizumab

Randomized controlled clinical trials and real-life observations indicate that less than 50% of patients with Crohn’s disease (CD) or ulcerative colitis (UC) respond to vedolizumab, a humanized monoclonal antibody that blocks the α4β7 integrin. Since α4β7-expressing lymphocytes mainly infiltrate the left colon, we assessed whether localization of CD and UC influences vedolizumab-induced remission. One hundred and eighty-one patients (74 CD and 107 UC) receiving vedolizumab in 3 referral centers were retrospectively evaluated for clinical remission at week 14. Demographic and clinical characteristics were compared between remitters and non-responders, and multivariable multinomial analysis was performed to identify predictors of remission. Remission was achieved in 17 CD (23%) and 34 UC (32%) patients, respectively. In CD, localization of the lesions did not influence clinical remission. In UC, the remitters had more frequently a distal/left-sided colitis (21/34, 62%) as compared to the non-responders (9/47, 19%), and extensive colitis was more frequent in the non-responders (38/47, 81%) than in the remitters (13/34, 38%). The multivariable multinomial analysis showed that distal/left-sided colitis was associated with a higher probability of clinical remission while extensive colitis was inversely associated with induction of remission. Data indicate that UC patients with distal or left-sided colitis are more likely to achieve remission than patients with extensive colitis following vedolizumab treatment.

Vedolizumab and etrolizumab for ulcerative colitis: twins or simple cousins?

Introduction: Vedolizumab is a monoclonal antibody that selectively blocks α4β7 integrin and has already been approved for use in patients with moderate-to-severe ulcerative colitis both as first and second line. Etrolizumab is a monoclonal antibody still being tested, which acts with a dual mechanism by selectively inhibiting both α4β7 and αEβ7 integrins.Areas covered: This review provides an overview of the literature data of vedolizumab and etrolizumab, in order to define their role in the treatment of patients with moderate-to-severe ulcerative colitis.Expert opinion: Etrolizumab and vedolizumab block the α4β7 integrin with a similar action mechanism. However, the inhibition of αEβ7 integrin by etrolizumab distinguishes the two anti-integrins making them 'cousin' drugs. Phase 3 clinical trials are needed to confirm the promising etrolizumab's efficacy data and to resolve any doubts about its safety, allowing a clearer comparison with vedolizumab.

Anti-MADCAM therapy for ulcerative colitis

Introduction: The mucosal addressin cell adhesion molecule-1 (MAdCAM-1) plays a key role in the endothelial adhesion and migration of lymphocytes to sites of inflammation in inflammatory bowel disease. Therapies that target this pathway appear to be a promising therapeutic approach in the management of ulcerative colitis (UC).Areas covered: This review provides a summary of the preclinical and available clinical data on the safety and efficacy of ontamalimab (SHP647), a fully human monoclonal antibody that binds and inhibits the action of MAdCAM-1.Expert opinion: Intestinal immune cell trafficking is emerging as an important component in the pathogenesis of UC. Ontamalimab (SHP647) inhibits this process by preventing the binding of integrins found on the surface of lymphocytes and the endothelial ligand adhesion molecule MAdCAM-1. This monoclonal antibody has already demonstrated safety and efficacy in phase II clinical trials. Its targeted mechanism of action suggests a superior safety profile as compared with the current systemic immunosuppressive therapies. Results from the phase III trials are awaited to establish ontamalimab (SHP647) as a therapeutic option in the management of UC.

Anti-trafficking agents in the treatment of inflammatory bowel disease

PURPOSE OF REVIEW

To describe the latest developments in the field of anti-trafficking agents (ATAs), a class of therapeutics with growing importance in the field of inflammatory bowel diseases (IBDs) that specifically inhibit steps of immune cell trafficking.

RECENT FINDINGS

Several translational and clinical studies have further shaped the knowledge about the mechanisms and effects of the anti-α4β7 integrin antibody vedolizumab. In parallel, new ATAs like the anti-β7 integrin antibody etrolizumab and the anti-MAdCAM-1 antibody ontamalimab are investigated in phase III clinical trials and might soon increase the therapeutic armamentarium in IBD.

SUMMARY

ATAs have unique mechanisms of action and can meanwhile be considered an indispensable column of IBD therapy. Further efforts are necessary to elucidate complex mechanistic aspects, to exactly define their role in relation to other therapeutic approaches and to identify novel treatment targets as well as biomarkers for personalized medicine.