Individual variability in patterns and dynamics of fecal gluten immunogenic peptides excretion after low gluten intake

Purpose Determination of Gluten Immunogenic Peptides (GIP) in feces is a direct tool for gluten exposure detection. The sensitivity of GIP detection methods for cases of unintentional low gluten intakes is unknown. We studied the interindividual variability in the kinetic of excretion under homogeneously controlled dietary conditions, and the sensitivity of fecal GIP tests after low amounts of punctual gluten ingestions. Methods Participants (n = 20) followed the same gluten-free menu for 12 days in which two separated doses of gluten (50 mg and 2 g) were ingested and all the depositions were collected. GIP from stool samples were analyzed by ELISA and lateral flow immunoassay (LFIA) tests. Results Most participants had detectable GIP after 50 mg and 2 g gluten ingestions using ELISA test (72.2% and 95%, respectively), whereas the LFIA test showed less sensitivity (22.2% and 80%, respectively). GIP were detected at higher either frequency or concentration in the range of 12–36 h after 50 mg intake, and 12–84 h after 2 g consumption. Considering this period, diagnostic sensitivity of GIP detection after a single 50 mg ingestion may be significatively increased analyzing three stool samples per individual. High variability among participants was found in the time and amount of GIP excretion; however, some individuals showed common patterns for both gluten intakes. Conclusion Sporadic gluten exposure detection may require several fecal samples to achieve level of sensitivity above 90%. Interindividual variability in the dynamic of GIP excretion may suggest patterns of gluten metabolism.

Gluten-related immunogenic peptides in stool as means to monitor compliance with gluten-free diet in children with newly dia gnosed coeliac disease

Objectives and study: To compare the values of gluten-related immunogenic peptides (GIP) in stool and anti-tissue transglutaminase IgA antibodies (anti-tTG IgA) in blood in children newly diagnosed with coeliac disease (CD). Methods: All children (2–15 y) newly diagnosed with CD between May 2018 and May 2020 at our clinic who complied with the inclusion criteria were invited to join the prospective study. During workup for CD, a stool sample to measure GIP was taken together with a blood sample to measure anti-tTG IgA. All newly diagnosed children were invited 4 months later for a check-up. Children and their caregivers were asked about known non-compliance with the gluten-free diet (GFD), a blood sample was taken to measure the anti-tTG IgA, and a stool sample was collected to measure GIP. Blood was evaluated for anti-tTG IgA by ELISA, and the stool was tested by quantitative Sandwich ELISA designed to detect and quantify GIP using the G12 antibody. Values of GIP and anti-tTG IgA were compared in terms of their relation to the upper limit of normal (ULN) of the particular method. Results: 29 children (18 girls) were enrolled in the study. The values of GIP in stool at the time of diagnosis were above the ULN (0.15 µg/g) in all children. Average 4.21, median 3.29, standard deviation (SD) 3.7. After the four months, all but three (89.7%) had values of GIP in the reference range. Average 0.29, median 0.12, SD 0.73. Similarly, anti-tTG IgA values were above the ULN (9.9 U/mL) at the time of diagnosis in all children. Average 164, median 195, SD 49. Although the anti-tTG IgA levels were lower at check-up in all but one child, only 10 (34.5%) showed values within the normal range, with an average of 27.9, median 12.0, and SD 38.9. All children declared strict adherence to GFD. Discussion: Using the GIP concentration in stool, adherence to GFD in our cohort of children is very good, better than that described in literature. Conclusion: Measuring GIP in stool could prove a more sensitive indicator of adherence to GFD in the early months after the diagnosis of CD when anti-tTG IgA are still elevated above the ULN due to their well-described gradual decrease after GFD initiation.

T Cell Receptor Non-Equilibrium Kinetics

An atomic-scale mechanism describing the role of mechanosensing in T Cell Receptor (TCR) recognition of peptides in the binding groove of the peptide-major histocompatibility complex (pMHC) may inform the design of novel TCRs for immunotherapies. Using steered molecular dynamic simulations, our study demonstrates that mutations to peptides in the binding groove of the pMHC -- which are known to discretely alter the T cell response to an antigen -- influence MHC conformation and thus the overall strength of the TCR-pMHC bond including duration and length under constant load. Moreover, physiochemical features of the TCR-pMHC dynamic bond strength, such as hydrogen bonds and Lennard-Jones contacts, correlate with the immunogenic response elicited by the specific peptide in the MHC groove. Thus, formation of transient TCR-pMHC bonds is a characteristic of immunogenic peptides and is mediated by stabilized interactions.

Immunogenic potential of neopeptides depends on parent protein subcellular location

Antigen presentation via the major histocompatibility complex (MHC) is essential for anti-tumor immunity, however the rules that determine what tumor-derived peptides will be immunogenic are still incompletely understood. Here we investigate whether protein subcellular location driven constraints on accessibility of peptides to the MHC associate with potential for peptide immunogenicity. Analyzing over 380,000 of peptides from studies of MHC presentation and peptide immunogenicity, we find clear spatial biases in both eluted and immunogenic peptides. We find that including parent protein location improves prediction of peptide immunogenicity in multiple datasets. In human immunotherapy cohorts, location was associated with response to a neoantigen vaccine, and immune checkpoint blockade responders generally had a higher burden of neopeptides from accessible locations. We conclude that protein subcellular location adds important information for optimizing immunotherapies.

Metataxonomic Review To Elucidate The Role of The Microbiome In Celiac Disease Across The Gastrointestinal Tract.

Background: Dysbiosis of the microbiome has been related to the Celiac disease (CeD) progress, an autoimmune disease characterised by gluten intolerance developed in genetically susceptible individuals under certain environmental factors. The microbiome contributes to CeD pathophysiology modulating the immune response by the action of short-chain fatty acids (SCFA), affecting gut barrier integrity allowing the entrance of gluten derived proteins, and degrading immunogenic peptides of gluten through endoprolyl peptidase enzymes. Results: We reviewed state of the art in taxonomic composition for CeD and compiled the larger dataset of 16S prokaryotic ribosomal RNA (rRNA) gene high-throughput sequencing for consensus profiling. We present for the first time an integrative analysis of metataxonomic data from CeD patients, including samples from different body sites (saliva, pharynx, duodenum, and stool). We found the presence of coordinated changes through the gastrointestinal tract characterised by an increase in Actinobacteria species in the upper tract (pharynx and duodenum), and an increase in Proteobacteria in the lower tract (duodenum and stool), as well as site-specific changes evidencing a dysbiosis in CeD patients' microbiota. Moreover, we described the effect of adherence to a gluten-free diet (GFD) evidenced by an increase in beneficial bacteria and a decrease in some Betaproteobacteriales but not fully restoring CeD-related dysbiosis. Conclusions: We illustrate that the gut microbiota acts as an enhancer of immune response in CeD through the production of lipopolysaccharides and other bacterial components that activate the immune response and by decrease SCFA producers bacteria. Furthermore, microbial changes observed through the gastrointestinal tract of CeD patients may help manage the disease and follow-up GFD treatment.

Effective Degradation of Gluten and Its Fragments by Gluten-Specific Peptidases: A Review on Application for the Treatment of Patients with Gluten Sensitivity

To date, there is no effective treatment for celiac disease (CD, gluten enteropathy), an autoimmune disease caused by gluten-containing food. Celiac patients are supported by a strict gluten-free diet (GFD). However, in some cases GFD does not negate gluten-induced symptoms. Many patients with CD, despite following such a diet, retain symptoms of active disease due to high sensitivity even to traces of gluten. In addition, strict adherence to GFD reduces the quality of life of patients, as often it is difficult to maintain in a professional or social environment. Various pharmacological treatments are being developed to complement GFD. One promising treatment is enzyme therapy, involving the intake of peptidases with food to digest immunogenic gluten peptides that are resistant to hydrolysis due to a high prevalence of proline and glutamine amino acids. This narrative review considers the features of the main proline/glutamine-rich proteins of cereals and the conditions that cause the symptoms of CD. In addition, we evaluate information about peptidases from various sources that can effectively break down these proteins and their immunogenic peptides, and analyze data on their activity and preliminary clinical trials. Thus far, the data suggest that enzyme therapy alone is not sufficient for the treatment of CD but can be used as a pharmacological supplement to GFD.