The enemy within the gut: bacterial pathogens in celiac autoimmunity

Molecular and Structural Parallels between Gluten Pathogenic Peptides and Bacterial-Derived Proteins by Bioinformatics Analysis

Gluten-related disorders (GRDs) are a group of diseases that involve the activation of the immune system triggered by the ingestion of gluten, with a worldwide prevalence of 5%. Among them, Celiac disease (CeD) is a T-cell-mediated autoimmune disease causing a plethora of symptoms from diarrhea and malabsorption to lymphoma. Even though GRDs have been intensively studied, the environmental triggers promoting the diverse reactions to gluten proteins in susceptible individuals remain elusive. It has been proposed that pathogens could act as disease-causing environmental triggers of CeD by molecular mimicry mechanisms. Additionally, it could also be possible that unrecognized molecular, structural, and physical parallels between gluten and pathogens have a relevant role. Herein, we report sequence, structural and physical similarities of the two most relevant gluten peptides, the 33-mer and p31-43 gliadin peptides, with bacterial pathogens using bioinformatics going beyond the molecular mimicry hypothesis. First, a stringent BLASTp search using the two gliadin peptides identified high sequence similarity regions within pathogen-derived proteins, e.g., extracellular proteins from Streptococcus pneumoniae and Granulicatella sp. Second, molecular dynamics calculations of an updated α-2-gliadin model revealed close spatial localization and solvent-exposure of the 33-mer and p31-43 peptide, which was compared with the pathogen-related proteins by homology models and localization predictors. We found putative functions of the identified pathogen-derived sequence by identifying T-cell epitopes and SH3/WW-binding domains. Finally, shape and size parallels between the pathogens and the superstructures of gliadin peptides gave rise to novel hypotheses about activation of innate immunity and dysbiosis. Based on our structural findings and the similarities with the bacterial pathogens, evidence emerges that these pathologically relevant gluten-derived peptides could behave as non-replicating pathogens opening new research questions in the interface of innate immunity, microbiome, and food research.

Age-Dependent Trends in the Celiac Disease: A Tertiary Center Experience

OBJECTIVES

Celiac disease (CD) is a common intestinal autoimmune disorder with diverse presenting features. We aimed to determine age-dependent patterns in CD presentation, diagnosis and management at a large tertiary referral center.

METHODS

A retrospective review of electronic medical records of pediatric patients diagnosed with CD between January 1999 and December 2018 at Schneider Children's Medical Center of Israel. We compared demographics, clinical and laboratory parameters between four age groups at CD presentation.

RESULTS

A cohort of 932 children was divided into four groups by age (in years) at diagnosis: 0-3 (17.9%), 3-6 (31.8%), 6-12 (34.5%), 12-18 (15.8%). The youngest age group presented more frequently with diarrhea, weight loss, abdominal distention, vomiting and lower weight z scores, P < 0.01. Hypoalbuminemia and zinc deficiency were also more frequent in this age group, compared to older patients (P < 0.05, each). Rates of anemia were higher in younger age groups (0-3 and 3-6 years), compared to older age groups, P < 0.05. Patients in the younger age groups (0-3 and 3-6 years) presented more frequently with tissue transglutaminase (TTG) levels above 10 times the upper limit of normal (ULN; P < 0.05), and more often normalized their CD serologies by 24 months of gluten-free diets (GFD) compared to older age groups (P < 0.05).

CONCLUSION

There is an age-dependent variation in CD presentation during childhood. Younger patients present more often with malabsorptive features, and higher TTG levels, yet normalize TTG while on GFD more rapidly than older patients. Clinicians should be aware of the diversity in CD presentation and course at the various presentation age.

The Multiomics Analyses of Fecal Matrix and Its Significance to Coeliac Disease Gut Profiling

Gastrointestinal (GIT) diseases have risen globally in recent years, and early detection of the host’s gut microbiota, typically through fecal material, has become a crucial component for rapid diagnosis of such diseases. Human fecal material is a complex substance composed of undigested macromolecules and particles, and the processing of such matter is a challenge due to the unstable nature of its products and the complexity of the matrix. The identification of these products can be used as an indication for present and future diseases; however, many researchers focus on one variable or marker looking for specific biomarkers of disease. Therefore, the combination of genomics, transcriptomics, proteomics and metabonomics can give a detailed and complete insight into the gut environment. The proper sample collection, sample preparation and accurate analytical methods play a crucial role in generating precise microbial data and hypotheses in gut microbiome research, as well as multivariate data analysis in determining the gut microbiome functionality in regard to diseases. This review summarizes fecal sample protocols involved in profiling coeliac disease.

Health Impact and Therapeutic Manipulation of the Gut Microbiome

Recent advances in microbiome studies have revealed much information about how the gut virome, mycobiome, and gut bacteria influence health and disease. Over the years, many studies have reported associations between the gut microflora under different pathological conditions. However, information about the role of gut metabolites and the mechanisms by which the gut microbiota affect health and disease does not provide enough evidence. Recent advances in next-generation sequencing and metabolomics coupled with large, randomized clinical trials are helping scientists to understand whether gut dysbiosis precedes pathology or gut dysbiosis is secondary to pathology. In this review, we discuss our current knowledge on the impact of gut bacteria, virome, and mycobiome interactions with the host and how they could be manipulated to promote health.