Jan Marsal

CCL25 mediates the localization of recently activated CD8alphabeta(+) lymphocytes to the small-intestinal mucosa.

The recruitment of antigen-specific T lymphocytes to the intestinal mucosa is central to the development of an effective mucosal immune response, yet the mechanism by which this process occurs remains to be fully defined. Here we show that the CC chemokine receptor 9 (CCR9) is selectively and functionally expressed on murine alpha(E)beta(7)(+) naive CD8alphabeta(+) lymphocytes and a subset of recently activated CD69(+) CD8alphabeta(+) lymphocytes. Using a T cell receptor transgenic transfer model, we demonstrate that CCR9 expression is functionally maintained on CD8alphabeta(+) lymphocytes following activation in mesenteric lymph nodes but rapidly downregulated on CD8alphabeta(+) lymphocytes activated in peripheral lymph nodes. These recently activated CCR9(+) CD8alphabeta(+) lymphocytes selectively localized to the small-intestinal mucosa, and in vivo neutralization of the CCR9 ligand, CCL25, reduced the ability of these cells to populate the small-intestinal epithelium. Together these results demonstrate an important role for chemokines in the localization of T lymphocytes to the small-intestinal mucosa and suggest that targeting CCL25 and/or CCR9 may provide a means to selectively modulate small-intestinal immune responses.

Involvement of CCL25 (TECK) in the generation of the murine small-intestinal CD8alpha alpha+CD3+ intraepithelial lymphocyte compartment.

The CC chemokine CCL25 (TECK) is selectively expressed in the thymus and small intestine, indicating a potential role in T lymphocyte development. In the present study we examined the role of CCL25 in the generation of the small‐intestinal CD8α α+CD3+ intraepithelial lymphocyte (IEL) compartment. CCL25 mRNA expression in the murine small intestine increased at three weeks of age and corresponded with the appearance of CD8α α+CD3+ lymphocytes in the small‐intestinal epithelium. Administration of monoclonal neutralizing anti‐CCL25 antibody to two‐week‐old mice led to a ∼50% reduction in the total number of CD8α α+TCRγ δ+ and CD8α α+TCRα β+ IEL at four weeks of age. Freshly isolated murine CD8α α+CD3+ IEL migrated in response to CCL25 and expressed the CCL25 receptor, CCR9. Analysis of CCR9 expression on putative IEL precursor populations demonstrated the presence of both CCR9– and CCR9+ cells and indicated that up‐regulation of this receptor occurred during IEL precursor differentiation. Finally, data from wild‐type and RAG–/– mice suggested that the reduction in CD8α α+CD3+ IEL in anti‐CCL25 antibody treated mice resulted primarily from defective maintenance and/or development of IEL precursors rather than a direct effect on mature CD8α α+CD3+ IEL.

Targeting T cell migration in inflammatory bowel disease.

Crohns disease and ulcerative colitis are chronic inflammatory disorders of the gastrointestinal tract and are collectively referred to as inflammatory bowel disease (IBD). IBD is a major cause of lifetime morbidity, has a severe impact on quality of life of patients (equivalent to that of rheumatoid arthritis, asthma, migraine or diabetes) and constitutes a substantial economic burden to the healthcare system. The introduction of anti‐tumour necrosis factor (TNF) antibodies has dramatically improved the treatment of IBD, but approximately one‐third of patients are nonresponders and another 30–50% will eventually lose the therapeutic effect or become intolerant to these antibodies. Thus, there is an urgent and unmet need for new therapies. The aetiologies of the different forms of IBD have not been fully elucidated but there is strong evidence implicating T cells and T‐cell migration to the gut in initiating and perpetuating the intestinal inflammatory process and tissue destruction. In recent years, progress in basic science has shed light on the mechanisms regulating T‐cell migration to the gut and new therapeutics targeting these pathways have been developed. It is interesting that some of the factors directing the localization of T cells to the gut have been shown to be relatively organ specific, potentially enabling new T‐cell‐targeted treatments to demonstrate improved safety whilst preserving therapeutic efficacy. Here, fundamental aspects of the gut immune system, the generation of tissue‐tropic effector T cells and the mechanisms of T‐cell trafficking to the gut mucosa will be reviewed. In addition, the role of these processes in IBD and how they have been exploited for the development of novel therapies for IBD will be discussed.

Involvement of CCR9 at multiple stages of adult T lymphopoiesis

The chemokine CCL25 is constitutively expressed in the thymus, and its receptor CCR9 is expressed on subsets of developing thymocytes. Nevertheless, the function of CCL25/CCR9 in adult thymopoiesis remains unclear. Here, we demonstrate that purified CCR9−/− hematopoietic stem cells are deficient in their ability to generate all major thymocyte subsets including double‐negative 1 (DN1) cells in competitive transfers. CCR9−/− bone marrow contained normal numbers of lineage− Sca‐1+c‐kit+, common lymphoid progenitors, and lymphoid‐primed multipotent progenitors (LMPP), and CCR9−/− LMPP showed similar T cell potential as their wild‐type (WT) counterparts when cultured on OP9–δ‐like 1 stromal cells. In contrast, early thymic progenitor and DN2 thymocyte numbers were reduced in the thymus of adult CCR9−/− mice. In fetal thymic organ cultures (FTOC), CCR9−/− DN1 cells were as efficient as WT DN1 cells in generating double‐positive (DP) thymocytes; however, under competitive FTOC, CCR9−/− DP cell numbers were reduced significantly. Similarly, following intrathymic injection into sublethally irradiated recipients, CCR9−/− DN cells were out‐competed by WT DN cells in generating DP thymocytes. Finally, in competitive reaggregation thymic organ cultures, CCR9−/− preselection DP thymocytes were disadvantaged significantly in their ability to generate CD4 single‐positive (SP) thymocytes, a finding that correlated with a reduced ability to form TCR‐MHC‐dependent conjugates with thymic epithelial cells. Together, these results highlight a role for CCR9 at several stages of adult thymopoiesis: in hematopoietic progenitor seeding of the thymus, in the DN‐DP thymocyte transition, and in the generation of CD4 SP thymocytes.

Vedolizumab treatment for immune checkpoint inhibitor-induced enterocolitis

Immune checkpoint inhibitors (ICPI), such as ipilimumab [anti-cytotoxic T-lymphocyte antigen-4 (CTLA-4) antibody] and nivolumab or pembrolizumab [anti-programmed cell death protein-1 (PD-1) antibodies], improve survival in several cancer types. Since inhibition of CTLA-4 or PD-1 leads to non-selective activation of the immune system, immune-related adverse events (irAEs) are frequent. Enterocolitis is a common irAE, currently managed with corticosteroids and, if necessary, anti-tumor necrosis factor-α therapy. Such a regimen carries a risk of serious side-effects including infections, and may potentially imply impaired antitumor effects. Vedolizumab is an anti-integrin α4β7 antibody with gut-specific immunosuppressive effects, approved for Crohn’s disease and ulcerative colitis. We report a case series of seven patients with metastatic melanoma or lung cancer, treated with vedolizumab off-label for ipilimumab- or nivolumab-induced enterocolitis, from June 2014 through October 2016. Clinical, laboratory, endoscopic, and histologic data were analyzed. Patients initially received corticosteroids but were steroid-dependent and/or partially refractory. One patient was administered infliximab but was refractory. The median time from onset of enterocolitis to start of vedolizumab therapy was 79 days. Following vedolizumab therapy, all patients but one experienced steroid-free enterocolitis remission, with normalized fecal calprotectin. This was achieved after a median of 56 days from vedolizumab start, without any vedolizumab-related side-effects noted. The patient in whom vedolizumab was not successful, due to active ulcerative colitis, received vedolizumab prophylactically. This is the first case series to suggest that vedolizumab is an effective and well-tolerated therapeutic for steroid-dependent or partially refractory ICPI-induced enterocolitis. A larger prospective study to evaluate vedolizumab in this indication is warranted.

Long-term effectiveness of vedolizumab in inflammatory bowel disease : a national study based on the Swedish National Quality Registry for Inflammatory Bowel Disease (SWIBREG)

Abstract Objectives: Clinical trials have demonstrated the efficacy of vedolizumab in inflammatory bowel disease (IBD). However, these findings may not reflect the clinical practice. Therefore, we aimed to describe a vedolizumab-treated patient population and assess long-term effectiveness. Materials and methods: Patients initiating vedolizumab between 1 June 2014 and 30 May 2015 were identified through the Swedish National Quality Registry for IBD. Prospectively collected data on treatment and disease activity were extracted. Clinical remission was defined as Patient Harvey Bradshaw index <5 in Crohn’s disease (CD) and Patient Simple Clinical Colitis Activity index <3 in ulcerative colitis (UC). Results: Two-hundred forty-six patients (147 CD, 92 UC and 7 IBD-Unclassified) were included. On study entry, 86% had failed TNF-antagonist and 48% of the CD patients had undergone ≥1 surgical resection. After a median follow-up of 17 (IQR: 14–20) months, 142 (58%) patients remained on vedolizumab. In total, 54% of the CD- and 64% of the UC patients were in clinical remission at the end of follow-up, with the clinical activity decreasing (p < .0001 in both groups). Faecal-calprotectin decreased in CD (p < .0001) and in UC (p = .001), whereas CRP decreased in CD (p = .002) but not in UC (p = .11). Previous anti-TNF exposure (adjusted HR: 4.03; 95% CI: 0.96–16.75) and elevated CRP at baseline (adjusted HR: 2.22; 95% CI: 1.10–4.35) seemed to be associated with discontinuation because of lack of response. Female sex was associated with termination because of intolerance (adjusted HR: 2.75; 95% CI: 1.16–6.48). Conclusion: Vedolizumab-treated patients represent a treatment-refractory group. A long-term effect can be achieved, even beyond 1 year of treatment.

A major population of mucosal memory CD4(+) T cells, coexpressing IL-18Rα and DR3, display innate lymphocyte functionality.

Mucosal tissues contain large numbers of memory CD4+ T cells that, through T-cell receptor-dependent interactions with antigen-presenting cells, are believed to have a key role in barrier defense and maintenance of tissue integrity. Here we identify a major subset of memory CD4+ T cells at barrier surfaces that coexpress interleukin-18 receptor alpha (IL-18Rα) and death receptor-3 (DR3), and display innate lymphocyte functionality. The cytokines IL-15 or the DR3 ligand tumor necrosis factor (TNF)-like cytokine 1A (TL1a) induced memory IL-18Rα+DR3+CD4+ T cells to produce interferon-γ, TNF-α, IL-6, IL-5, IL-13, granulocyte–macrophage colony-stimulating factor (GM-CSF), and IL-22 in the presence of IL-12/IL-18. TL1a synergized with IL-15 to enhance this response, while suppressing IL-15-induced IL-10 production. TL1a- and IL-15-mediated cytokine induction required the presence of IL-18, whereas induction of IL-5, IL-13, GM-CSF, and IL-22 was IL-12 independent. IL-18Rα+DR3+CD4+ T cells with similar functionality were present in human skin, nasal polyps, and, in particular, the intestine, where in chronic inflammation they localized with IL-18-producing cells in lymphoid aggregates. Collectively, these results suggest that human memory IL-18Rα+DR3+ CD4+ T cells may contribute to antigen-independent innate responses at barrier surfaces.

Multi-locus sequence analysis (MLSA) of clinical “CandidatusNeoehrlichia mikurensis” strains from Europe

ABSTRACT “Candidatus Neoehrlichia mikurensis” is the tick-borne agent of neoehrlichiosis, an infectious disease that primarily affects immunocompromised patients. So far, the genetic variability of “Ca. Neoehrlichia” has been studied only by comparing 16S rRNA genes and groEL operon sequences. We describe the development and use of a multilocus sequence analysis (MLSA) protocol to characterize the genetic diversity of clinical “Ca. Neoehrlichia” strains in Europe and their relatedness to other species within the Anaplasmataceae family. Six genes were selected: ftsZ, clpB, gatB, lipA, groEL, and 16S rRNA. Each MLSA locus was amplified by real-time PCR, and the PCR products were sequenced. Phylogenetic trees of MLSA locus relatedness were constructed from aligned sequences. Blood samples from 12 patients with confirmed “Ca. Neoehrlichia” infection from Sweden (n = 9), the Czech Republic (n = 2), and Germany (n = 1) were analyzed with the MLSA protocol. Three of the Swedish strains exhibited identical lipA sequences, while the lipA sequences of the strains from the other nine patients were identical to each other. One of the Czech strains had one differing nucleotide in the clpB sequence from the sequences of the other 11 strains. All 12 strains had identical sequences for the genes 16S rRNA, ftsZ, gatB, and groEL. According to the MLSA, among the Anaplasmataceae, “Ca. Neoehrlichia” is most closely related to Ehrlichia ruminantium, less so to Anaplasma phagocytophilum, and least to Wolbachia endosymbionts. To conclude, three sequence types of infectious “Ca. Neoehrlichia” were identified: one in the west of Sweden, one in the Czech Republic, and one spread throughout Europe.

CD8αβ + γδ T cells : A novel T cell subset with a potential role in inflammatory bowel disease

γδ T cells have been attributed a wide variety of functions, which in some cases may appear as contradictory. To better understand the enigmatic biology of γδ T cells it is crucial to define the constituting subpopulations. γδ T cells have previously been categorized into two subpopulations: CD8αα+ and CD8− cells. In this study we have defined and characterized a novel subset of human γδ T-cells expressing CD8αβ. These CD8αβ+ γδ T cells differed from the previously described γδ T cell subsets in several aspects, including the degree of enrichment within the gut mucosa, the activation status in blood, the type of TCRδ variant used in blood, and small but significant differences in their response to IL-2 stimulation. Furthermore, the novel subset expressed cytotoxic mediators and CD69, and produced IFN-γ and TNF-α. In patients with active inflammatory bowel disease the mucosal frequencies of CD8αβ+ γδ T cells were significantly lower as compared with healthy controls, correlated negatively with the degree of disease activity, and increased to normal levels as a result of anti–TNF-α therapy. In conclusion, our results demonstrate that CD8αβ+ γδ T cells constitute a novel lymphocyte subset, which is strongly enriched within the gut and may play an important role in gut homeostasis and mucosal healing in inflammatory bowel disease.

Long-term outcome of infliximab treatment in chronic active ulcerative colitis : a Swedish multicentre study of 250 patients

Real‐life long‐term data on infliximab treatment in ulcerative colitis are limited.