Emergence of an adaptive immune paradigm to explain celiac disease: a perspective on new evidence and implications for future interventions and diagnosis

Exploring the association between atrial fibrillation and celiac disease: a comprehensive review

Objective

This paper aims to provide a comprehensive overview of the pathophysiology of atrial fibrillation (AF) and celiac disease (CD) individually while also exploring the emerging evidence of a potential association between the two conditions.

Methods

The pathophysiology of AF, the most prevalent arrhythmia globally, and CD, an autoimmune condition triggered by gluten consumption, is examined. Genetic, structural, electrophysiological, and inflammatory factors contributing to their development are explored.

Results

AF involves irregular atrial activity leading to electrical and structural remodeling of the atrium. CD is characterized by an immune response to gluten, primarily associated with HLA-DQ2 and HLA-DQ8 genetic mutations, resulting in damage to intestinal tissue. Emerging research suggests a link between AF and CD, possibly mediated through inflammation, fibrosis, and electromechanical delays in the atrium.

Conclusion

Understanding the association between AF and CD carries significant clinical implications. Recognition of this relationship can assist in identifying individuals at higher risk for AF and inform proactive management strategies. Additionally, it underscores the importance of comprehensive care for CD patients, considering potential cardiac implications. Further research is warranted to elucidate precise mechanisms and explore potential therapeutic interventions targeting common pathways, opening avenues for enhanced patient care and future investigations.

Gluten-Dependent Activation of CD4+ T Cells by MHC Class II-Expressing Epithelium

BACKGROUND & AIMS

Intestinal epithelial cell (IEC) damage is a hallmark of celiac disease (CeD); however, its role in gluten-dependent T-cell activation is unknown. We investigated IEC-gluten-T-cell interactions in organoid monolayers expressing human major histocompatibility complex class II (HLA-DQ2.5), which facilitates gluten antigen recognition by CD4+ T cells in CeD.

METHODS

Epithelial major histocompatibility complex class II (MHCII) was determined in active and treated CeD, and in nonimmunized and gluten-immunized DR3-DQ2.5 transgenic mice, lacking mouse MHCII molecules. Organoid monolayers from DR3-DQ2.5 mice were treated with or without interferon (IFN)-γ, and MHCII expression was evaluated by flow cytometry. Organoid monolayers and CD4+ T-cell co-cultures were incubated with gluten, predigested, or not by elastase-producing Pseudomonas aeruginosa or its lasB mutant. T-cell function was assessed based on proliferation, expression of activation markers, and cytokine release in the co-culture supernatants.

RESULTS

Patients with active CeD and gluten-immunized DR3-DQ2.5 mice demonstrated epithelial MHCII expression. Organoid monolayers derived from gluten-immunized DR3-DQ2.5 mice expressed MHCII, which was upregulated by IFN-γ. In organoid monolayer T-cell co-cultures, gluten increased the proliferation of CD4+ T cells, expression of T-cell activation markers, and the release of interleukin-2, IFN-γ, and interleukin-15 in co-culture supernatants. Gluten metabolized by P aeruginosa, but not the lasB mutant, enhanced CD4+ T-cell proliferation and activation.

CONCLUSIONS

Gluten antigens are efficiently presented by MHCII-expressing IECs, resulting in the activation of gluten-specific CD4+ T cells, which is enhanced by gluten predigestion with microbial elastase. Therapeutics directed at IECs may offer a novel approach for modulating both adaptive and innate immunity in patients with CeD.

Evolution in coeliac disease diagnosis and management

The traditional gut-centric view of coeliac disease is evolving as immune and genetic insights underscore the central importance of a systemic, T cell immune response to gluten in disease pathogenesis. As the field increasingly recognize the limitations of small intestinal histology as the diagnostic standard, data supporting the accuracy of an immune (serologic) diagnosis of coeliac disease - well demonstrated in children - are growing for adults. Novel biomarkers such as interleukin-2 that identify the gluten-specific T cell demonstrate high sensitivity and specificity for coeliac disease and offer the potential for a diagnostic approach that avoids the need for gluten challenge. Asymptomatic disease and manifestations outside the gut pose considerable challenges for diagnosis using a case-finding strategy and enthusiasm for population screening is growing. The gluten-free diet remains a highly restrictive treatment and there is a paucity of controlled data to inform a safe gluten intake threshold. Ongoing symptoms and enteropathy are common and require systematic evaluation. Slowly-responsive disease is prevalent in the older patient diagnosed with coeliac disease, and super-sensitivity to gluten is an emerging concept that may explain many cases of nonresponsive disease. While there is great interest in developing novel therapies for coeliac disease, no drug has yet been registered. Efficacy studies are generally assessing drugs in patients with treated coeliac disease who undergo gluten challenge or in patients with nonresponsive disease; however, substantial questions remain around specific endpoints relevant for patients, clinicians and regulatory agencies and optimal trial design. Novel immune tools are providing informative readouts for clinical trials and are now shaping their design.

Tolerance-inducing therapies in coeliac disease - mechanisms, progress and future directions

Coeliac disease is an autoinflammatory condition caused by immune reactions to cereal gluten proteins. Currently, the only available treatment for the condition is a lifelong avoidance of gluten proteins in the diet. There is an unmet need for alternative therapies. Coeliac disease has a strong association with certain HLA-DQ allotypes (DQ2.5, DQ2.2 and DQ8), and these disease-associated HLA-DQ molecules present deamidated gluten peptides to gluten-specific CD4+ T cells. The gluten-specific CD4+ T cells are the drivers of the immune reactions leading to coeliac disease. Once established, the clonotypes of gluten-specific CD4+ T cells persist for decades, explaining why patients must adhere to a gluten-free diet for life. Given the key pathogenic role of gluten-specific CD4+ T cells, tolerance-inducing therapies that target these T cells are attractive for treatment of the disorder. Lessons learned from coeliac disease might provide clues for treatment of other HLA-associated diseases for which the disease-driving antigens are unknown. Thus, intensive efforts have been and are currently implemented to bring an effective tolerance-inducing therapy for coeliac disease. This Review discusses mechanisms of the various approaches taken, summarizing the progress made, and highlights future directions in this field.

Efficacy and safety of gluten peptide-based antigen-specific immunotherapy (Nexvax2) in adults with coeliac disease after bolus exposure to gluten (RESET CeD): an interim analysis of a terminated randomised, double-blind, placebo-controlled phase 2 study

BACKGROUND

A gluten-free diet is insufficient to treat coeliac disease because intestinal injury persists and acute reactions with cytokine release follow gluten exposure. Nexvax2 is a specific immunotherapy using immunodominant peptides recognised by gluten-specific CD4⁺ T cells that might modify gluten-induced disease in coeliac disease. We aimed to assess the effects of Nexvax2 on gluten-induced symptoms and immune activation in patients with coeliac disease.

METHODS

This was a randomised, double-blind, placebo-controlled phase 2 trial done at 41 sites (29 community, one secondary, and 11 tertiary centres) in the USA, Australia, and New Zealand. Patients with coeliac disease aged 18-70 years who had excluded gluten for at least 1 year, were HLA-DQ2.5 positive, and had a worsening of symptoms after an unmasked 10 g vital gluten challenge were eligible for inclusion. Patients were stratified by HLA-DQ2.5 status (HLA-DQ2.5 non-homozygous vs homozygous). Patients who were non-homozygous were centrally (ICON; Dublin, Ireland) randomly assigned (1:1) to receive subcutaneous Nexvax2 (non-homozygous Nexvax2 group) or saline (0·9% sodium chloride; non-homozygous placebo group) twice a week escalating from 1 μg to 750 μg during the first 5 weeks followed by 11 weeks of maintenance therapy at 900 μg per dose. The exploratory homozygous group was centrally randomly assigned (2:1) to receive Nexvax2 (homozygous Nexvax2 group) or placebo (homozygous placebo group); patients who were homozygous received the same doseage as those who were non-homozygous. The primary endpoint was change in coeliac disease patient reported outcomes (total gastrointestinal domain) from pretreatment baseline to the day of masked bolus 10 g vital gluten challenge given in week 14 analysed in the non-homozygous intention-to-treat population. The trial is registered with ClinicalTrials.gov, NCT03644069.

FINDINGS

Between Sept 21, 2018, and April 24, 2019, 383 volunteers were screened for inclusion, of whom 179 (47%; 133 [74%] women, 46 [26%] men; median age 41 years [IQR 33-55]) were randomly assigned. One (1%) of 179 patients was excluded from analysis due to misassignment of genotype. The non-homozygous Nexvax2 group included 76 patients, the non-homozygous placebo group included 78 patients, the homozygous Nexvax2 group included 16 patients, and the homozygous placebo group included eight patients. The study was discontinued after planned interim analysis of 66 patients who were non-homozygous. We report an unmasked post-hoc analysis of all available data for the primary endpoint and secondary symptom-based endpoints combining data from 67 (66 were assessed in the planned interim analysis for the primary endpoint). Mean change from baseline to day of first masked gluten challenge in total gastrointestinal score for the non-homozygous Nexvax2 group was 2·86 (SD 2·28) compared with 2·63 (2·07) for the non-homozygous placebo group (p=0·43). Adverse events were similar between all patients who received Nexvax2 and those who received placebo. Serious adverse events were reported in five (3%) of 178 patients (two [2%] of 92 who received Nexvax2 and three [4%] of 82 who received placebo). One patient in the non-homozygous Nexvax2 group had a serious adverse event that occurred during gluten challenge (left-sided mid-back muscle strain with imaging suggestive of partial left kidney infarction). Serious adverse events were reported for three (4%) of 78 patients in the non-homozygous placebo group (one each with exacerbation of asthma and appendicitis, and one who had forehead abscess, conjunctivitis, and folliculitis) and one (1%) patient in the non-homozygous Nexvax2 group developed a pulmonary embolism. The most frequent adverse events in all 92 patients who received Nexvax2 compared with all 86 patients who received placebo were nausea (44 [48%] of 92 patients who received Nexvax2 vs 29 (34%) of 86 patients who received placebo), diarrhoea (32 [35%] vs 25 [29%]), abdominal pain (31 [34%] vs 27 [31%]), headache 32 [35%] vs 20 [23%]), and fatigue (24 [26%] vs 31 [36%]).

INTERPRETATION

Nexvax2 did not reduce acute gluten-induced symptoms. Masked bolus vital gluten challenge provides an alternative to extended gluten challenge in efficacy studies for coeliac disease.

FUNDING

ImmusanT.

Review article: Follow-up of coeliac disease

Coeliac disease is a lifelong immune-mediated enteropathy with systemic features associated with increased morbidity and modestly increased mortality. Treatment with a strict gluten-free diet improves symptoms and mucosal damage but is not curative and low-level gluten intake is common despite strict attempts at adherence. Regular follow-up after diagnosis is considered best-practice however this is executed poorly in the community with the problem compounded by the paucity of data informing optimal approaches. The aim of dietary treatment is to resolve symptoms, reduce complication risk and improve quality of life. It follows that the goals of monitoring are to assess dietary adherence, monitor disease activity, assess symptoms and screen for complications. Mucosal disease remission is regarded a key measure of treatment success as healing is associated with positive health outcomes. However, persistent villous atrophy is common, even after many years of a gluten-free diet. As the clinical significance of asymptomatic enteropathy is uncertain the role for routine follow-up biopsies remains contentious. Symptomatic non-responsive coeliac disease is common and with systematic follow-up a cause is usually found. Effective models of care involving the gastroenterologist, dietitian and primary care doctor will improve the consistency of long-term management and likely translate into better patient outcomes. Identifying suitable treatment targets linked to long-term health is an important goal.

Review article: Diagnosis of coeliac disease: a perspective on current and future approaches

Diagnostics will play a central role in addressing the ongoing dramatic rise in global prevalence of coeliac disease, and in deploying new non-dietary therapeutics. Clearer understanding of the immunopathogenesis of coeliac disease and the utility of serology has led to partial acceptance of non-biopsy diagnosis in selected cases. Non-biopsy diagnosis may expand further because research methods for measuring gluten-specific CD4+ T cells and the acute recall response to gluten ingestion in patients is now relatively straightforward. This perspective on diagnosis in the context of the immunopathogenesis of coeliac disease sets out to highlight current consensus, limitations of current practices, gluten food challenge for diagnosis and the potential for diagnostics that measure the underlying cause for coeliac disease, gluten-specific immunity.

Reduced frequency of circulating regulatory T cells and their related immunosuppressive mediators in treated celiac patients

BACKGROUND

Regulatory T cells (Tregs) have an important role in the control of the immune responses. This study aimed to compare the frequency of peripheral blood (PB) CD4+ CD25+ FoxP3+ Treg cells and PB and duodenal expression levels of pro- and anti-inflammatory mediators in treated celiac disease (CD) patients and healthy controls.

METHODS AND RESULTS

Duodenal biopsy specimens and PB samples were collected from 60 treated CD patients and 60 controls. Flow cytometry analysis was conducted on peripheral blood mononuclear cell (PBMC) specimens and relative PB and duodenal mRNA expression levels of CD25, forkhead box P3 (Foxp3), interleukin (IL)-10 and granzyme B (GrzB) were evaluated using quantitative real-time PCR. The levels of serum IL-10 and IL-6 were tested with sandwich enzyme-linked immunosorbent assay kits. p values < 0.05 were considered significant. Flow cytometry analysis showed a significant decrease in the number of Tregs in CD patients' PBMC specimens (p = 0.012). CD25 and Foxp3 PB mRNA expressions were also lower in CD patients without reaching the significance level (p > 0.05). IL-10 PB mRNA and protein expression did not differ between the groups (p > 0.05), and GrzB PB expression was significantly reduced in CD patients (p = 0.001). In duodenal specimens of CD patients, while significantly increased CD25, Foxp3 mRNA expression (p = 0.01 and 0.001, respectively) and decreased IL-10 mRNA expression (p = 0.02) were observed, GrzB mRNA expression did not differ between groups (p > 0.05). Moreover, a high serum level of IL-6 was observed in CD patients (p = 0.001).

CONCLUSIONS

Despite following the gluten free diet, there may still be residual inflammation in the intestine of CD patients. Accordingly, finding a therapeutic approach based on strengthening the function of Treg cells in CD might be helpful.