Influence of milk-feeding type and genetic risk of developing coeliac disease on intestinal microbiota of infants: the PROFICEL study

Recent advances in pediatric celiac disease

The incidence of celiac disease (CD) has increased over the last half-century, resulting in rising interest in identifying risk factors for CD. The necessity of duodenal biopsies in the diagnosis of CD has recently been challenged. Areas covered: This review covers the recent literature regarding the role of infant feeding practices, including breastfeeding and timing of gluten introduction, and the microbiota in the development of CD. Additionally, the application of the European Society for Pediatric Gastroenterology, Hepatology, and Nutrition guidelines for a non-biopsy approach to the diagnosis of CD is reviewed. Expert commentary: Recent investigations have not revealed any significant effect of breastfeeding or timing of gluten introduction on the risk of CD in at-risk populations. There are alterations in the microbiota of CD patients. However, the role of the microbiome and whether its manipulation has a clinical effect are unknown. Preliminary data suggests a non-biopsy approach to diagnosis of pediatric CD can be applied to several populations, although additional studies are needed. Prospective investigations are underway to examine the interplay of infant feeding practices and the microbiome and to identify particular CD-specific biomarkers that may aid in the diagnosis and ultimately prevention of CD.

Significantly higher faecal counts of the yeasts candida and saccharomyces identified in people with coeliac disease

Background

Coeliac disease is an autoimmune disorder resulting from an interaction between diet, genome and immunity. The treatment of CoeD is lifelong adherence to a gluten free diet, which is associated with clinical and histological improvements. However, a substantive number of individuals report only partial symptom improvement despite both compliance with a strict gluten free diet and improvements in serological and histological biomarkers of disease activity. The role of the intestinal microbiota is an area of interest in this sub-group.

Aims

To investigate the role of yeasts and parasites in individuals reporting persistent symptoms of Coeliac disease (CoeD).

Methods

Forty-five people who met the ESPGHAN diagnostic criteria for CoeD were recruited via the Australian Coeliac Association. The faecal measures of the DNA of yeasts and parasites from the CoeD group were compared to data obtained from the medical records of non-coeliac controls with gastrointestinal symptoms from other causes.

Results

Candida sp. was detected in 33% of the CoeD group compared 0% of the control group (p = 0.000) and Saccharomyces sp. was detected in 33% of the CoeD group compared to 10% of the control group (p = 0.026). There were no differences in the presence of any of the parasite species measured.

Conclusion

Further research is required to understand the significance of Candida and Saccharomyces species in both the aetiology of CoeD and of persistent symptoms in this sub-group.

Trial Registration Clinical Trial Registration—ANZCTR Number: 12610000630011

A microbiota-centric view of diseases of the upper gastrointestinal tract

The distinctive anatomy and physiology of the upper gastrointestinal tract and the difficulty of obtaining samples led to the theory that it was bacteria free. However, multiomics studies are indicating otherwise. Although influenced by both oral and gastric bacteria, the resident microbial ecosystem in the oesophagus is dominated by Streptococcus. A shift from Gram-positive to Gram-negative bacteria occurs in oesophagitis and Barrett's oesophagus, and this shift might be involved in the pathogenesis of oesophageal adenocarcinoma. The gastric microenvironment is populated by microbial communities mainly of the Firmicutes, Actinobacteria, Bacteroidetes, and Proteobacteria phyla and species of the Lactobacillus, Streptococcus, and Propionibacterium genera. The composition of gastric microbiota is highly dynamic, and is influenced by acid suppression, gastric inflammation, and Helicobacter pylori. Duodenal microbes are also implicated in the onset and outcome of coeliac disease. Bacteria of the genera Bacteroides, Clostridium, and Staphylococcus dominate the duodenal flora in active coeliac disease whereas lactobacilli and bifidobacteria decrease. Although knowledge of the composition of the microbiota of the upper gastrointestinal tract has advanced substantially, this information is far from being translated to the clinical setting. In this Review, we assess the data related to the potential contribution of microbes to the susceptibility for and pathogenesis of upper gastrointestinal diseases.

Dysbiosis a risk factor for celiac disease

Celiac disease remains one of the most challenging pathologies of the small intestine. It involves multiple pathogenic pathways and there are no disease-changing pharmacological agents available against it yet. The term microbiota refers to the community of microorganisms that inhabit a particular region of the body. Normal gut microbiota has a vital role in maintaining the intestinal homeostasis and promoting health. Celiac disease is associated with microbiota alteration, especially with an increase in the number of Gram-negative bacteria and a decrease in the number of Gram-positive bacteria. There is a strong relationship between intestinal dysbiosis and celiac disease, and recent studies are aimed at determining whether the celiac disease is a risk factor for dysbiosis or dysbiosis is for celiac disease. Therefore, the aim of this review was to assess the latest findings regarding the gut microbiota and its impact on the celiac disease, including therapeutic aspects.

Role of the Human Breast Milk-Associated Microbiota on the Newborns' Immune System: A Mini Review

The human milk is fundamental for a correct development of newborns, as it is a source not only of vitamins and nutrients, but also of commensal bacteria. The microbiota associated to the human breast milk contributes to create the "initial" intestinal microbiota of infants, having also a pivotal role in modulating and influencing the newborns' immune system. Indeed, the transient gut microbiota is responsible for the initial change from an intrauterine Th2 prevailing response to a Th1/Th2 balanced one. Bacteria located in both colostrum and mature milk can stimulate the anti-inflammatory response, by stimulating the production of specific cytokines, reducing the risk of developing a broad range of inflammatory diseases and preventing the expression of immune-mediated pathologies, such as asthma and atopic dermatitis. The aim of the present Mini Review is to elucidate the specific immunologic role of the human milk-associated microbiota and its impact on the newborn's health and life, highlighting the importance to properly study the biological interactions in a bacterial population and between the microbiota and the host. The Auto Contractive Map, for instance, is a promising analytical methodology based on artificial neural network that can elucidate the specific role of bacteria contained in the breast milk in modulating the infants' immunological response.

The Interaction Between Celiac Disease and Intestinal Microbiota

Celiac disease (CD) is the most common autoimmune enteropathy, triggered by a deregulated immune response to gliadin. It has been hypothesized that human intestinal microbiota may interfere with the pathogenesis of the disease and in the clinical course of CD. In the present review, we analyzed the microbiota alterations observed in the course of CD, how they may influence the pathogenesis of CD, and the possible applications for a microbiota modulation in CD. In detail, most of the current literature underlined that the dysbiosis in CD is hallmarked by an increase in gram-negative and Bacteroidetes species, and by a decrease in Bifidobacteria and Lactobacilli. As the intestinal microbiota is able to modulate the cytokine environment, an unfavorable microbiota could amplify the immune response to gliadin in individuals with CD, whereas the administration of probiotic species could lead to a decrease in proinflammatory cytokine production. Therefore, dysbiosis could represent an important trigger in CD pathogenesis, along with genetic (HLA-haplotypes) and environmental factors (antibiotic administration, mode of delivery, and breastfeeding). Although data on the modulation of microbiota by GFD are conflicting, current evidence has demonstrated that probiotic administration could be useful to improve symptoms and to reduce molecular mucosal inflammation, by downregulating the cytokines involved in CD pathogenesis. However, studies analyzing this aspect are few in number, thus stimulating the exploration of this field, with the aim of achieving a solid pathophysiological basis for probiotic administration in CD.

Gut Microbiota and Risk of Developing Celiac Disease

Gut microbiota shapes the development of the mucosal immune system and may provide protection against immune-mediated diseases. Celiac disease (CD) is a chronic inflammatory condition triggered by dietary gluten proteins, recently associated with gut microbiota alterations in cross-sectional studies comparing patients and controls. Whether or not these differences are causally related to the disease has yet to be elucidated, but evaluation of specific bacteria isolated from CD patients in experimental models suggests that they can promote an adverse response to dietary gluten, whereas other commensal bacteria can be protective. Genetic and environmental factors associated with increased CD risk have also been linked to shifts in the gut microbiota composition in infants early in life. Epigenetic mechanisms also seem to play an important role in modulating gut microbiota composition and function and, theoretically, could also influence CD risk. Here, we review the current knowledge on how host genetics, environmental factors, and epigenetic modifications could modulate gut microbiota functionality and how this may influence CD risk. Greater understanding of the role of this triad in CD onset and pathogenesis will be valuable in designing proof-of concept interventions in the gut ecosystem, with a view to improving CD management.

Dietary Gluten-Induced Gut Dysbiosis Is Accompanied by Selective Upregulation of microRNAs with Intestinal Tight Junction and Bacteria-Binding Motifs in Rhesus Macaque Model of Celiac Disease

The composition of the gut microbiome reflects the overall health status of the host. In this study, stool samples representing the gut microbiomes from 6 gluten-sensitive (GS) captive juvenile rhesus macaques were compared with those from 6 healthy, age- and diet-matched peers. A total of 48 samples representing both groups were studied using V4 16S rRNA gene DNA analysis. Samples from GS macaques were further characterized based on type of diet administered: conventional monkey chow, i.e., wheat gluten-containing diet (GD), gluten-free diet (GFD), barley gluten-derived diet (BOMI) and reduced gluten barley-derived diet (RGB). It was hypothesized that the GD diet would lower the gut microbial diversity in GS macaques. This is the first report illustrating the reduction of gut microbial alpha-diversity (p < 0.05) following the consumption of dietary gluten in GS macaques. Selected bacterial families (e.g., Streptococcaceae and Lactobacillaceae) were enriched in GS macaques while Coriobacteriaceae was enriched in healthy animals. Within several weeks after the replacement of the GD by the GFD diet, the composition (beta-diversity) of gut microbiome in GS macaques started to change (p = 0.011) towards that of a normal macaque. Significance for alpha-diversity however, was not reached by the day 70 when the feeding experiment ended. Several inflammation-associated microRNAs (miR-203, -204, -23a, -23b and -29b) were upregulated (p < 0.05) in jejunum of 4 biopsied GS macaques fed GD with predicted binding sites on 16S ribosomal RNA of Lactobacillus reuteri (accession number: NR_025911), Prevotella stercorea (NR_041364) and Streptococcus luteciae (AJ297218) that were overrepresented in feces. Additionally, claudin-1, a validated tight junction protein target of miR-29b was significantly downregulated in jejunal epithelium of GS macaques. Taken together, we predict that with the introduction of effective treatments in future studies the diversity of gut microbiomes in GS macaques will approach those of healthy individuals. Further studies are needed to elucidate the regulatory pathways of inflammatory miRNAs in intestinal mucosa of GS macaques and to correlate their expression with gut dysbiosis.

Effect of Bifidobacterium breve on the Intestinal Microbiota of Coeliac Children on a Gluten Free Diet: A Pilot Study

Coeliac disease (CD) is associated with alterations of the intestinal microbiota. Although several Bifidobacterium strains showed anti-inflammatory activity and prevention of toxic gliadin peptides generation in vitro, few data are available on their efficacy when administered to CD subjects. This study evaluated the effect of administration for three months of a food supplement based on two Bifidobacterium breve strains (B632 and BR03) to restore the gut microbial balance in coeliac children on a gluten free diet (GFD). Microbial DNA was extracted from faeces of 40 coeliac children before and after probiotic or placebo administration and 16 healthy children (Control group). Sequencing of the amplified V3-V4 hypervariable region of 16S rRNA gene as well as qPCR of Bidobacterium spp., Lactobacillus spp., Bacteroides fragilis group Clostridiumsensu stricto and enterobacteria were performed. The comparison between CD subjects and Control group revealed an alteration in the intestinal microbial composition of coeliacs mainly characterized by a reduction of the Firmicutes/Bacteroidetes ratio, of Actinobacteria and Euryarchaeota. Regarding the effects of the probiotic, an increase of Actinobacteria was found as well as a re-establishment of the physiological Firmicutes/Bacteroidetes ratio. Therefore, a three-month administration of B. breve strains helps in restoring the healthy percentage of main microbial components.

[Guidelines for complementary feeding in healthy infants]

A proper nutrition during the first two years of life is critical to reach the full potential of every human being; now, this period is recognized as a critical window for promoting optimal growth, development, and good health. Therefore, adequate feeding at this stage of life has an impact on health, nutritional status, growth and development of children; not only in the short term, but in the medium and long term. This paper provides recommendations on complementary feeding (CF) presented as questions or statements that are important for those who take care for children during this stage of life. For example: When to start complementary feedings: 4 or 6 months of age?; Exposure to potentially allergenic foods; Introduction of sweetened beverages; Use of artificial sweeteners and light products; Food introduction sequence; Food consistency changes according to neurological maturation; Number of days to test acceptance and tolerance to new foods; Amounts for each meal; Inadequate complementary feeding practices; Myths and realities of complementary feeding; Developmental milestones; Practice of "Baby Led Weaning" and practice of vegetarianism.

Gut Bifidobacteria Populations in Human Health and Aging

The intestinal microbiota has increasingly been shown to have a vital role in various aspects of human health. Indeed, several studies have linked alterations in the gut microbiota with the development of different diseases. Among the vast gut bacterial community, Bifidobacterium is a genus which dominates the intestine of healthy breast-fed infants whereas in adulthood the levels are lower but relatively stable. The presence of different species of bifidobacteria changes with age, from childhood to old age. Bifidobacterium longum, B. breve, and B. bifidum are generally dominant in infants, whereas B. catenulatum, B. adolescentis and, as well as B. longum are more prevalent in adults. Increasingly, evidence is accumulating which shows beneficial effects of supplementation with bifidobacteria for the improvement of human health conditions ranging from protection against infection to different extra- and intra-intestinal positive effects. Moreover, bifidobacteria have been associated with the production of a number of potentially health promoting metabolites including short chain fatty acids, conjugated linoleic acid and bacteriocins. The aim of this mini-review is to describe the bifidobacteria compositional changes associated with different stages in life, highlighting their beneficial role, as well as their presence or absence in many disease states.

Investigating the early metabolic fingerprint of celiac disease - a prospective approach

OBJECTIVES AND STUDY

In the development of Celiac Disease (CD) both genetic and environmental factors play a crucial role. The Human Leukocyte Antigen (HLA)-DQ2 and HLA-DQ8 loci are strongly related to the disease and are necessary but not sufficient for the development of CD. Therefore, increasing interest lies in examining the mechanisms of CD onset from the early beginning. Differences in serum and urine metabolic profiles between healthy individuals and CD patients have been reported previously. We aimed to investigate if the metabolic pathways were already altered in young, 4 month old infants, preceding the CD diagnosis.

METHODS

Serum samples were available for 230 four month old infants of the PreventCD project, a multicenter, randomized, double-blind, dietary intervention study. All children were positive for HLA-DQ2 and/or HLA-DQ8 and had at least one first-degree relative diagnosed with CD. Amino acids were quantified after derivatization with liquid chromatography - tandem mass spectrometry (MS/MS) and polar lipid concentrations (acylcarnitines, lysophosphatidylcholines, phosphatidylcholines, and sphingomyelins) were determined with direct infusion MS/MS. We investigated the association of the metabolic profile with (1) the development of CD up to the age of 8 years (yes/no), (2) with HLA-risk groups, (3) with the age at CD diagnosis, using linear mixed models and cox proportional hazards models. Gender, intervention group, and age at blood withdrawal were included as potential confounder.

RESULTS

By the end of 2014, thirty-three out of the 230 children (14%) were diagnosed with CD according to the ESPGHAN criteria. Median age at diagnosis was 3.4 years (IQR, 2.4-5.2). Testing each metabolite for a difference in the mean between healthy and CD children, we (1) could not identify a discriminant analyte or a pattern pointing towards an altered metabolism (Bonferroni corrected P > 0.05 for all). Metabolite concentrations (2) did not differ across the HLA-risk groups. When investigating the age at diagnosis using (3) survival models, we found no evidence for an association between the metabolic profile and the risk of a later CD diagnosis.

CONCLUSION

The metabolic profile at 4 months of age was not predictive for the development of CD up to the age of 8 years. Our results suggest that metabolic pathways reflected in serum are affected only later in life and that the HLA-genotype does not influence the serum metabolic profile in young infants before introduction of solid food.

Genome Structure of the Symbiont Bifidobacterium pseudocatenulatum CECT 7765 and Gene Expression Profiling in Response to Lactulose-Derived Oligosaccharides

Bifidobacterium pseudocatenulatum CECT 7765 was isolated from stools of a breast-fed infant. Although, this strain is generally considered an adult-type bifidobacterial species, it has also been shown to have pre-clinical efficacy in obesity models. In order to understand the molecular basis of its adaptation to complex carbohydrates and improve its potential functionality, we have analyzed its genome and transcriptome, as well as its metabolic output when growing in galacto-oligosaccharides derived from lactulose (GOS-Lu) as carbon source. B. pseudocatenulatum CECT 7765 shows strain-specific genome regions, including a great diversity of sugar metabolic-related genes. A preliminary and exploratory transcriptome analysis suggests candidate over-expression of several genes coding for sugar transporters and permeases; furthermore, five out of seven beta-galactosidases identified in the genome could be activated in response to GOS-Lu exposure. Here, we also propose that a specific gene cluster is involved in controlling the import and hydrolysis of certain di- and tri-saccharides, which seemed to be those primarily taken-up by the bifidobacterial strain. This was discerned from mass spectrometry-based quantification of different saccharide fractions of culture supernatants. Our results confirm that the expression of genes involved in sugar transport and metabolism and in the synthesis of leucine, an amino acid with a key role in glucose and energy homeostasis, was up-regulated by GOS-Lu. This was done using qPCR in addition to the exploratory information derived from the single-replicated RNAseq approach, together with the functional annotation of genes predicted to be encoded in the B. pseudocatenulatum CETC 7765 genome.

Infant feeding and risk of developing celiac disease: a systematic review

OBJECTIVE

To review the evidence for the association of breast feeding, breastfeeding duration or the timing of gluten introduction and the later development of celiac disease (CD).

DESIGN

Systematic review.

METHODS

We searched MEDLINE, via PubMed, EMBASE and Web of Science, for studies published up to 31 August 2015 investigating the association of breastfeeding duration, breast feeding at the moment of gluten introduction or the timing of gluten introduction and the later development of CD. Prospective studies had to enrol infants/children at high risk of CD. For retrospective studies, participants had to be children or adults with CD. The paper quality was assessed by means of a GRADE score and the bias risk was assessed by the Newcastle-Ottawa Scale (for observational cohort studies) and Cochrane Collaboration's tool (for randomised trials).

RESULTS

Out of 149 retrieved papers, 48 were considered in depth and 16 were included in this review (9 were prospective and 2 were interventional). We found that neither duration of breastfeeding nor breastfeeding at time of gluten introduction nor the delayed introduction of gluten during weaning were effective in preventing later development of CD.

CONCLUSIONS

Currently, there is no evidence on the optimal breastfeeding duration or the effects of avoiding early (<4 months of age) or late (≥ 6 or even at 12 months) gluten introduction in children at risk of CD. Accordingly, no specific general recommendations about gluten introduction or optimal breastfeeding duration can be presently provided on evidence-based criteria in order to prevent CD.

Decrease in lactobacilli in the intestinal microbiota of celiac children with a gluten-free diet, and selection of potentially probiotic strains

The intestinal microbiota would be implicated in pathology associated with celiac disease caused by an abnormal immune system reaction against gluten present in cereal grains. The objectives of this work were to detect through basic methods the changes in the composition of the most common genera of bacteria from the intestinal microbiota of symptom-free celiac disease children with a gluten-free diet compared with healthy children from Tucumán and to select lactobacilli (Lb) strains with probiotic potential from the feces of healthy children. Results demonstrated that the feces of celiac children with a gluten-free diet showed significantly lower counts of Lb (P < 0.05) compared with healthy children, while enterobacteria tended to increase in celiac children. On the basis of these results, isolation of some Lb from the feces of healthy children was carried out. Thus, 5 Lb strains were selected because of their high resistance percentages to gastrointestinal tract conditions. In addition, their autoaggregation and hydrophobicity properties were evaluated: Lactobacillus rhamnosus (LC4) showed the highest percentage of autoaggregation while Lactobacillus paracasei (LC9) showed high hydrophobicity. Based on these results, LC4 and LC9 were selected, and their use as potential probiotic strains to improve signs and symptoms associated with celiac disease is discussed. This is the first study performed in Argentina concerning the relationship between intestinal microbiota and celiac disease in celiac children with a gluten-free diet. In addition, the development of a probiotic food addressed towards celiac patients and designed with Lb isolated from the feces of healthy children from our province represents a promising alternative to improve the quality of life of celiac patients.

[Microbiota and gastrointestinal diseases]

The bacterial colonisation is established immediately after birth, through direct contact with maternal microbiota, and may be influenced during lactation. There is emerging evidence indicating that quantitative and qualitative changes on gut microbiota contribute to alterations in the mucosal activation of the immune system, leading to intra- or extra-intestinal diseases. A balance between pathogenic and beneficial microbiota throughout childhood and adolescence is important to gastrointestinal health, including protection against pathogens, inhibition of pathogens, nutrient processing (synthesis of vitamin K), stimulation of angiogenesis, and regulation of host fat storage. Probiotics can promote an intentional modulation of intestinal microbiota favouring the health of the host. A review is presented on the modulation of intestinal microbiota on prevention, and adjuvant treatment of some paediatric gastrointestinal diseases.

Timing of solid food introduction is associated with urinary F2-isoprostane concentrations in childhood

BACKGROUND

Timing of solid food introduction in infancy has been associated with several chronic diseases. To explore potential mechanisms, we investigated the relationship between timing of solid food introduction and F2-isoprostanes-a marker of oxidative stress.

METHODS

Urinary F2-isoprostanes were assessed in 336 healthy children aged less than 11.5 y with 1,266 clinic visits (mean = 3.8 visits per child) in the Diabetes Autoimmunity Study in the Young. We analyzed the association between F2-isoprostane concentrations and infant diet exposures using linear mixed models adjusted for age, age(2), HLA-DR3/4,DQB1*0302 genotype, first-degree relative with type 1 diabetes, maternal age, maternal education, sex, and exposure to in utero cigarette smoke.

RESULTS

Later solid food introduction was associated with lower F2-isoprostane concentrations in childhood (on average, 0.10 ng/mg per month of age at introduction; estimate: -0.10 (95% confidence interval (CI): -0.18, -0.02) P value = 0.02). Moreover, childhood F2-isoprostane concentrations were, on average, 0.24 ng/mg lower in individuals breastfed at solid food introduction (estimate: -0.24 (95% CI: -0.47, -0.01) P value = 0.04) compared with those who were not. Associations remained significant after limiting analyses to F2-isoprostanes after 2 y of age.

CONCLUSION

Our results suggest a long-term protective effect of later solid food introduction and breastfeeding at solid food introduction against increased F2-isoprostane concentrations throughout childhood.

Novel players in coeliac disease pathogenesis: role of the gut microbiota

Several studies point towards alteration in gut microbiota composition and function in coeliac disease, some of which can precede the onset of disease and/or persist when patients are on a gluten-free diet. Evidence also exists that the gut microbiota might promote or reduce coeliac-disease-associated immunopathology. However, additional studies are required in humans and in mice (using gnotobiotic technology) to determine cause-effect relationships and to identify agents for modulating the gut microbiota as a therapeutic or preventative approach for coeliac disease. In this Review, we summarize the current evidence for altered gut microbiota composition in coeliac disease and discuss how the interplay between host genetics, environmental factors and the intestinal microbiota might contribute to its pathogenesis. Moreover, we highlight the importance of utilizing animal models and long-term clinical studies to gain insight into the mechanisms through which host-microbial interactions can influence host responses to gluten.

Intestinal Microbiota and Celiac Disease: Cause, Consequence or Co-Evolution?

It is widely recognized that the intestinal microbiota plays a role in the initiation and perpetuation of intestinal inflammation in numerous chronic conditions. Most studies report intestinal dysbiosis in celiac disease (CD) patients, untreated and treated with a gluten-free diet (GFD), compared to healthy controls. CD patients with gastrointestinal symptoms are also known to have a different microbiota compared to patients with dermatitis herpetiformis and controls, suggesting that the microbiota is involved in disease manifestation. Furthermore, a dysbiotic microbiota seems to be associated with persistent gastrointestinal symptoms in treated CD patients, suggesting its pathogenic implication in these particular cases. GFD per se influences gut microbiota composition, and thus constitutes an inevitable confounding factor in studies conducted in CD patients. To improve our understanding of whether intestinal dysbiosis is the cause or consequence of disease, prospective studies in healthy infants at family risk of CD are underway. These studies have revealed that the CD host genotype selects for the early colonizers of the infant’s gut, which together with environmental factors (e.g., breast-feeding, antibiotics, etc.) could influence the development of oral tolerance to gluten. Indeed, some CD genes and/or their altered expression play a role in bacterial colonization and sensing. In turn, intestinal dysbiosis could promote an abnormal response to gluten or other environmental CD-promoting factors (e.g., infections) in predisposed individuals. Here, we review the current knowledge of host-microbe interactions and how host genetics/epigenetics and environmental factors shape gut microbiota and may influence disease risk. We also summarize the current knowledge about the potential mechanisms of action of the intestinal microbiota and specific components that affect CD pathogenesis.

The Influence of the Autoimmunity-Associated Ancestral HLA Haplotype AH8.1 on the Human Gut Microbiota: A Cross-Sectional Study

Multiple immune-related genes are encoded in the HLA complex on chromosome 6p21. The 8.1 ancestral haplotype (AH8.1) include the classical HLA alleles HLA-B*08:01 and HLA-DRB1*03:01, and has been associated with a large number of autoimmune diseases, but the underlying mechanisms for this association are largely unknown. Given the recently established links between the gut microbiota and inflammatory diseases, we hypothesized that the AH8.1 influences the host gut microbial community composition. To study this further, healthy individuals were selected from the Norwegian Bone Marrow Donor Registry and categorized as either I. AH8.1 homozygote (n=34), II. AH8.1 heterozygote (n=38), III. Non AH8.1 heterozygote or IV. HLA-DRB1 homozygote but non AH8.1 (n=15). Bacterial DNA from stool samples were subjected to sequencing of the V3–V5 region of the 16S rRNA gene on the 454 Life Sciences platform and data analyzed using Mothur and QIIME. The results showed that the abundances of different taxa were highly variable within all pre-defined AH8.1 genotype groups. Using univariate non-parametric statistics, there were no differences regarding alpha or beta diversity between AH8.1 carriers (categories I and II) and non-carriers (categories III and IV), however four different taxa (Prevotellaceae, Clostridium XVIII, Coprococcus, Enterorhabdus) had nominally significant lower abundances in AH8.1 carriers than non-carriers. After including possible confounders in a multivariate linear regression, only the two latter genera remained significantly associated. In conclusion, the overall contribution of the AH8.1 haplotype to the variation in gut microbiota profile of stool in the present study was small.

Immunogenetic control of the intestinal microbiota

All vertebrates contain a diverse collection of commensal, symbiotic and pathogenic microorganisms, such as bacteria, viruses and fungi, on their various body surfaces, and the ecological community of these microorganisms is referred to as the microbiota. Mucosal sites, such as the intestine, harbour the majority of microorganisms, and the human intestine contains the largest community of commensal and symbiotic bacteria. This intestinal community of bacteria is diverse, and there is a significant variability among individuals with respect to the composition of the intestinal microbiome. Both genetic and environmental factors can influence the diversity and composition of the intestinal bacteria with the predominant environmental factor being diet. So far, studies have shown that diet-dependent differences in the composition of intestinal bacteria can be classified into three groups, called enterotypes. Other environmental factors that can influence the composition include antibiotics, probiotics, smoking and drugs. Studies of monozygotic and dizygotic twins have proven that genetics plays a role. Recently, MHC II genes have been associated with specific microbial compositions in human infants and transgenic mice that express different HLA alleles. There is a growing list of genes/molecules that are involved with the sensing and monitoring of the intestinal lumen by the intestinal immune system that, when genetically altered, will significantly alter the composition of the intestinal microflora. The focus of this review will be on the genetic factors that influence the composition of the intestinal microflora.

An integrative view of microbiome-host interactions in inflammatory bowel diseases

The intestinal microbiota, which is composed of bacteria, viruses, and micro-eukaryotes, acts as an accessory organ system with distinct functions along the intestinal tract that are critical for health. This review focuses on how the microbiota drives intestinal disease through alterations in microbial community architecture, disruption of the mucosal barrier, modulation of innate and adaptive immunity, and dysfunction of the enteric nervous system. Inflammatory bowel disease is used as a model system to understand these microbial-driven pathologies, but the knowledge gained in this space is extended to less-well-studied intestinal diseases that may also have an important microbial component, including environmental enteropathy and chronic colitis-associated colorectal cancer.

The HLA-DQ2 genotype selects for early intestinal microbiota composition in infants at high risk of developing coeliac disease

OBJECTIVE

Intestinal dysbiosis has been associated with coeliac disease (CD), but whether the alterations are cause or consequence of the disease is unknown. This study investigated whether the human leukocyte antigen (HLA)-DQ2 genotype is an independent factor influencing the early gut microbiota composition of healthy infants at family risk of CD.

DESIGN

As part of a larger prospective study, a subset (n=22) of exclusively breastfed and vaginally delivered infants with either high genetic risk (HLA-DQ2 carriers) or low genetic risk (non-HLA-DQ2/8 carriers) of developing CD were selected from a cohort of healthy infants with at least one first-degree relative with CD. Infant faecal microbiota was analysed by 16S rRNA gene pyrosequencing and real time quantitative PCR.

RESULTS

Infants with a high genetic risk had significantly higher proportions of Firmicutes and Proteobacteria and lower proportions of Actinobacteria compared with low-risk infants. At genus level, high-risk infants had significantly less Bifidobacterium and unclassified Bifidobacteriaceae proportions and more Corynebacterium, Gemella, Clostridium sensu stricto, unclassified Clostridiaceae, unclassified Enterobacteriaceae and Raoultella proportions. Quantitative real time PCR also revealed lower numbers of Bifidobacterium species in infants with high genetic risk than in those with low genetic risk. In high-risk infants negative correlations were identified between Bifidobacterium species and several genera of Proteobacteria (Escherichia/Shigella) and Firmicutes (Clostridium).

CONCLUSIONS

The genotype of infants at family risk of developing CD, carrying the HLA-DQ2 haplotypes, influences the early gut microbiota composition. This finding suggests that a specific disease-biased host genotype may also select for the first gut colonisers and could contribute to determining disease risk.

Understanding the role of gut microbiome in metabolic disease risk

The gut microbiota structure, dynamics, and function result from interactions with environmental and host factors, which jointly influence the communication between the gut and peripheral tissues, thereby contributing to health programming and disease risk. Incidence of both type-1 and type-2 diabetes has increased during the past decades, suggesting that there have been changes in the interactions between predisposing genetic and environmental factors. Animal studies show that gut microbiota and its genome (microbiome) influence alterations in energy balance (increased energy harvest) and immunity (inflammation and autoimmunity), leading to metabolic dysfunction (e.g., insulin resistance and deficiency). Thus, although they have different origins, both disorders are linked by the association of the gut microbiota with the immune-metabolic axis. Human studies have also revealed shifts in microbiome signatures in diseased subjects as compared with controls, and a few of them precede the development of these disorders. These studies contribute to pinpointing specific microbiome components and functions (e.g., butyrate-producing bacteria) that can protect against both disorders. These could exert protective roles by strengthening gut barrier function and regulating inflammation, as alterations in these are a pathophysiological feature of both disorders, constituting common targets for future preventive approaches.

Gut microbes and adverse food reactions: Focus on gluten related disorders

Immediately following birth, the gastrointestinal tract is colonized with a complex community of bacteria, which helps shape the immune system. Under conditions of health, the immune system is able to differentiate between innocuous antigens, including food protein and commensals, and harmful antigens such as pathogens. However, patients with celiac disease (CD) develop an intolerance to gluten proteins which results in a pro-inflammatory T-cell mediated immune response with production of anti-gluten and anti-tissue transglutaminase antibodies. This adaptive immune response, in conjunction with activation of innate inflammatory cells, lead to destruction of the small intestinal mucosa. Overall 30% of the global population has genetic risk to develop CD. However, only a small proportion develop CD, suggesting that additional environmental factors must play a role in disease pathogenesis. Alterations in small intestinal microbial composition have recently been associated with active CD, indicating a possible role for the microbiota in CD. However, studies demonstrating causality are lacking. This review will highlight the recent data on the potential role of the microbiota in CD pathogenesis, the potential mechanisms, and discuss future research directions.

Regional specialization within the intestinal immune system

The intestine represents the largest compartment of the immune system. It is continually exposed to antigens and immunomodulatory agents from the diet and the commensal microbiota, and it is the port of entry for many clinically important pathogens. Intestinal immune processes are also increasingly implicated in controlling disease development elsewhere in the body. In this Review, we detail the anatomical and physiological distinctions that are observed in the small and large intestines, and we suggest how these may account for the diversity in the immune apparatus that is seen throughout the intestine. We describe how the distribution of innate, adaptive and innate-like immune cells varies in different segments of the intestine and discuss the environmental factors that may influence this. Finally, we consider the implications of regional immune specialization for inflammatory disease in the intestine.

Exploring the influence of the gut microbiota and probiotics on health: a symposium report

The present report describes the presentations delivered at the 7th International Yakult Symposium, ‘The Intestinal Microbiota and Probiotics: Exploiting Their Influence on Health’, in London on 22–23 April 2013. The following two themes associated with health risks were covered: (1) the impact of age and diet on the gut microbiota and (2) the gut microbiota's interaction with the host. The strong influence of the maternal gut microbiota on neonatal colonisation was reported, as well as rapid changes in the gut microbiome of older people who move from community living to residential care. The effects of dietary changes on gut metabolism were described and the potential influence of inter-individual microbiota differences was noted, in particular the presence/absence of keystone species involved in butyrate metabolism. Several speakers highlighted the association between certain metabolic disorders and imbalanced or less diverse microbiota. Data from metagenomic analyses and novel techniques (including an ex vivo human mucosa model) provided new insights into the microbiota's influence on coeliac, obesity-related and inflammatory diseases, as well as the potential of probiotics. Akkermansia muciniphila and Faecalibacterium prausnitzii were suggested as targets for intervention. Host–microbiota interactions were explored in the context of gut barrier function, pathogenic bacteria recognition, and the ability of the immune system to induce either tolerogenic or inflammatory responses. There was speculation that the gut microbiota should be considered a separate organ, and whether analysis of an individual's microbiota could be useful in identifying their disease risk and/or therapy; however, more research is needed into specific diseases, different population groups and microbial interventions including probiotics.

Intestinal microbiota during early life - impact on health and disease

In the first years after birth, the intestinal microbiota develops rapidly both in diversity and complexity while being relatively stable in healthy adults. Different life-style-related factors as well as medical practices have an influence on the early-life intestinal colonisation. We address the impact of some of these factors on the consecutive microbiota development and later health. An overview is presented of the microbial colonisation steps and the role of the host in that process. Moreover, new early biomarkers are discussed with examples that include the association of microbiota and atopic diseases, the correlation of colic and early development and the impact of the use of antibiotics in early life. Our understanding of the development and function of the intestinal microbiota is constantly improving but the long-term influence of early-life microbiota on later life health deserves careful clinical studies.

Intestinal stem cells and celiac disease

Stem cells (SCs) are the key to tissue genesis and regeneration. Given their central role in homeostasis, dysfunctions of the SC compartment play a pivotal role in the development of cancers, degenerative disorders, chronic inflammatory pathologies and organ failure. The gastrointestinal tract is constantly exposed to harsh mechanical and chemical conditions and most of the epithelial cells are replaced every 3 to 5 d. According to the so-called Unitarian hypothesis, this renewal is driven by a common intestinal stem cell (ISC) residing within the crypt base at the origin of the crypt-to-villus hierarchical migratory pattern. Celiac disease (CD) can be defined as a chronic immune-mediated disease that is triggered and maintained by dietary proteins (gluten) in genetically predisposed individuals. Many advances have been achieved over the last years in understanding of the pathogenic interactions among genetic, immunological and environmental factors in CD, with a particular emphasis on intestinal barrier and gut microbiota. Conversely, little is known about ISC modulation and deregulation in active celiac disease and upon a gluten-free diet. Nonetheless, bone marrow-derived SC transplantation has become an option for celiac patients with complicated or refractory disease. This manuscript summarizes the “state of the art” regarding CD and ISCs, their niche and potential role in the development and treatment of the disease.

Antibiotic exposure in pregnancy and risk of coeliac disease in offspring: a cohort study

Background

The infant microbiota may play a pathogenic role in coeliac disease (CD). Antibiotic treatment in pregnancy is common and could significantly impact the infant microbiota. In this study, we aimed to investigate the association between antibiotic exposure during pregnancy and CD in offspring.

Methods

Prospective questionnaire data on antibiotic exposure in pregnancy were available in 8729 children participating in the All Babies in Southeast Sweden (ABIS) cohort study, and of these 46 developed CD until December 2006. Cox regression estimated hazard ratios (HRs) for CD in the offspring among mothers exposed to antibiotics during pregnancy, with adjustment for parent-reported diary data on breastfeeding, age at gluten introduction and number of infections in the child’s first year of life.

Results

Of the 1836 children exposed to antibiotics during pregnancy, 12 (0.7%) children developed CD as compared with 34/6893 (0.5%) unexposed children (HR = 1.33; 95% CI = 0.69-2.56). Risk estimates remained unchanged after adjustment for breastfeeding, age at gluten introduction and infection load in the child’s first year of life (HR = 1.28; 95% CI = 0.66-2.48).

Conclusions

We found no statistically significant association between antibiotic exposure during pregnancy and CD in offspring. This lack of association may either be true or the result of limited statistical power.

US perspective on gluten-related diseases

The incidence of allergy and autoimmune disease in the US and other industrialized nations is increasing, and gluten-related disorders are no exception. The US has documented a profound rise in celiac disease that cannot be fully explained by improved serological techniques or better recognition by physicians. Non-celiac gluten sensitivity, a condition only recently recognized by the medical community, has become a commonly diagnosed entity. Proteins, including gluten are increasingly being identified as a source of wheat allergy. Although the gluten free diet represents a safe and effective treatment for these conditions, there is still much to be learned about the development of gluten-related disorders and the apparent increase in incidence within the US. In this article, we present a review of current knowledge on the epidemiology of gluten-related disorders within a global context, with a focus on diagnostic trends and the evaluation of potential risk factors.

Bifidobacteria: their impact on gut microbiota composition and their applications as probiotics in infants

This review is aimed at describing the most recent advances in the gut microbiota composition of newborns and infants with a particular emphasis on bifidobacteria. The newborn gut microbiota is quite unstable, whereas after weaning, it becomes more stable and gets closer to the typical adult microbiota. The newborn and infant gut microbiota composition is impaired in several enteric and non-enteric pathologies. The core of this review is the description of the most recent documented applications of bifidobacteria to newborns and infants for their prevention and treatment. Acute diarrhea is the most studied disease for which bifidobacteria are applied with great success, Bifidobacterium longum and Bifidobacterium breve being the most applied species. Moreover, the most recent updates in the use of bifidobacteria for the prevention and treatment of pathologies typical of newborns, such as necrotizing enterocolitis, colics, and streptococcal infections, are presented. In addition, a number of not strictly enteric pathologies have in recent years evidenced a strict correlation with an aberrant gut microbiota in infants, in particular showing a reduced level of bifidobacteria. These diseases represent new potential opportunities for probiotic applications. Among them, allergic diseases, celiac disease, obesity, and neurologic diseases are described in this review. The preliminary use of bifidobacteria in in vitro systems and animal models is summarized as well as preliminary in vivo studies. Only after validation of the results via human clinical trials will the potentiality of bifidobacteria in the prevention and cure of these pathologies be definitely assessed.

The human microbiome and probiotics: implications for pediatrics

Steady advances in our knowledge of the composition and function of the human microbiome at multiple body sites including the gut, skin and airways will likely contribute to our understanding of mechanisms of probiotic action by beneficial microbes. Microbe:microbe and microbe:human interactions are important considerations as we select probiotics for pediatric patients in the future. Although our knowledge about the composition of the microbiome is progressing rapidly, many gaps exist about the functional capacity and metabolic machinery of the human microbiome. Based on a limited amount of data, probiotics appear capable of altering the composition and function of the microbiome. Probiotics may be part of dietary strategies that combine ways to enhance microbiome function with nutrients that may be converted to active compounds promoting human health. Probiotics have yielded beneficial effects in numerous studies in the context of different diseases in pediatric gastroenterology. These disease states include necrotizing enterocolitis, antibiotic-associated diarrhea and colitis, acute gastroenteritis and irritable bowel syndrome. In the skin and airways, it is unclear if probiotics can affect the function of the microbiome to reduce the impact of diseases such as asthma and atopic dermatitis. An enhanced understanding of the effects of probiotics on the microbiome should facilitate selection of optimal probiotic strains for specific diseases in the future.

Microbial contamination of human milk purchased via the Internet

OBJECTIVE

To quantify microbial contamination of human milk purchased via the Internet as an indicator of disease risk to recipient infants.

METHODS

Cross-sectional sample of human milk purchased via a popular US milk-sharing Web site (2012). Individuals advertising milk were contacted to arrange purchase, and milk was shipped to a rented mailbox in Ohio. The Internet milk samples (n = 101) were compared with unpasteurized samples of milk donated to a milk bank (n = 20).

RESULTS

Most (74%) Internet milk samples were colonized with Gram-negative bacteria or had >10(4) colony-forming units/mL total aerobic count. They exhibited higher mean total aerobic, total Gram-negative, coliform, and Staphylococcus sp counts than milk bank samples. Growth of most species was positively associated with days in transit (total aerobic count [log10 colony-forming units/mL] β = 0.71 [95% confidence interval: 0.38-1.05]), and negatively associated with number of months since the milk was expressed (β = -0.36 [95% confidence interval: -0.55 to -0.16]), per simple linear regression. No samples were HIV type 1 RNA-positive; 21% of Internet samples were cytomegalovirus DNA-positive.

CONCLUSIONS

Human milk purchased via the Internet exhibited high overall bacterial growth and frequent contamination with pathogenic bacteria, reflecting poor collection, storage, or shipping practices. Infants consuming this milk are at risk for negative outcomes, particularly if born preterm or are medically compromised. Increased use of lactation support services may begin to address the milk supply gap for women who want to feed their child human milk but cannot meet his or her needs.

Breast milk: proactive immunomodulation and mucosal protection against viruses and other pathogens

The majority of microorganisms infecting humans cross through the mucosal barrier. This is particularly true in infants who explore the world with their mouths while their immune system is still developing. Human milk not only supplies the nutritional needs of the newborn and protects the baby against infection by confering trophic protection to the intestinal mucosa, but additionally shapes the infant’s gut microbiota and instructs immunomodulation. Reflecting maternal environmental exposition and in virtue of its multiple mechanism of action, secretory IgA in milk exerts a decisive role in direct and cross-protection against a variety of pathogens. Its active role in priming the infant’s immune system is an intriguing hypothesis. From this perspective, breast milk antibodies produced by means of maternal immunization might represent protective and proactive factors able to shape and enhance the infant’s immune responses. Strategies to optimize the benefits of maternal immunization include novel vaccine formulations and mucosal route of delivery.

Human milk hyaluronan enhances innate defense of the intestinal epithelium

Breast-feeding is associated with enhanced protection from gastrointestinal disease in infants, mediated in part by an array of bioactive glycan components in milk that act through molecular mechanisms to inhibit enteric pathogen infection. Human milk contains hyaluronan (HA), a glycosaminoglycan polymer found in virtually all mammalian tissues. We have shown that synthetic HA of a specific size range promotes expression of antimicrobial peptides in intestinal epithelium. We hypothesize that hyaluronan from human milk also enhances innate antimicrobial defense. Here we define the concentration of HA in human milk during the first 6 months postpartum. Importantly, HA isolated from milk has a biological function. Treatment of HT-29 colonic epithelial cells with human milk HA at physiologic concentrations results in time- and dose-dependent induction of the antimicrobial peptide human β-defensin 2 and is abrogated by digestion of milk HA with a specific hyaluronidase. Milk HA induction of human β-defensin 2 expression is also reduced in the presence of a CD44-blocking antibody and is associated with a specific increase in ERK1/2 phosphorylation, suggesting a role for the HA receptor CD44. Furthermore, oral administration of human milk-derived HA to adult, wild-type mice results in induction of the murine Hβ D2 ortholog in intestinal mucosa and is dependent upon both TLR4 and CD44 in vivo. Finally, treatment of cultured colonic epithelial cells with human milk HA enhances resistance to infection by the enteric pathogen Salmonella typhimurium. Together, our observations suggest that maternally provided HA stimulates protective antimicrobial defense in the newborn.

Duodenal microbiota composition and mucosal homeostasis in pediatric celiac disease

BACKGROUND

Celiac disease (CD) is an autoimmune disorder of the small intestine which is triggered by dietary gluten in genetically predisposed (HLA-DQ2/DQ8 positive) individuals. Only a fraction of HLA-DQ2/DQ8 positive individuals develop CD indicating that other factors have a role in the disorder. Several studies have addressed intestinal microbiota aberrancies in pediatric CD, but the results are inconsistent. Previously, we demonstrated that pediatric CD patients have lower duodenal expression of TLR2 and higher expression of TLR9 as compared to healthy controls (HC) indicating that microbiota may have a role in CD.

METHODS

We used bacterial phylogenetic microarray to comprehensively profile the microbiota in duodenal biopsies of CD (n = 10) and HC (n = 9) children. The expression of selected mucosa-associated genes was assessed by qRT-PCR in CD and HC children and in treated CD adults (T-CD, n = 6) on gluten free diet.

RESULTS

The overall composition, diversity and the estimated microbe associated molecular pattern (MAMP) content of microbiota were comparable between CD and HC, but a sub-population profile comprising eight genus-like bacterial groups was found to differ significantly between HC and CD. In HC, increased TLR2 expression was positively correlated with the expression of tight junction protein ZO-1. In CD and T-CD, the expression of IL-10, IFN-g and CXCR6 were higher as compared to HC.

CONCLUSIONS

The results suggest that microbiota and altered expression of mucosal receptors have a role in CD. In CD subjects, the increased expression of IL-10 and IFN-g may have partly resulted from the increased TLR9 expression and signaling.

Host genotype, intestinal microbiota and inflammatory disorders

Intestinal microbiota may influence human physiology and disease risk due to the role it plays in mediating appropriate immune responses to harmful and innocuous antigens. Colonisation of the intestine in early life seems particularly important as it is the main environmental stimulus for immune system maturation. This is a dynamic process, which depends on both environmental and genetic factors. The pathogenesis of inflammatory bowel disease, such as Crohn's disease, involves genetic polymorphisms (e.g. CARD15/nucleotide-binding oligomerisation domain 2) related to an excessive inflammatory response to commensal microbiota and to its unbalanced composition. Atopic diseases have also been linked to imbalances in microbiota and to related genetic factors (e.g. TLR4 and CD14 genes), although these associations are still controversial. Research into the relationship between the genetic risk of developing celiac disease (human leukocyte antigen (HLA)-DQ2/DQ8) and the early colonisation process in infants at family risk of the disease has also reported that the HLA-DQ genotype could influence staphylococcal colonisation. Future observational studies considering both host genetics and microbiota could be critical in defining the complex host-microbe interactions and the respective role each plays in inflammatory disorders.

Intestinal T-cell responses in celiac disease - impact of celiac disease associated bacteria

A hallmark of active celiac disease (CD), an inflammatory small-bowel enteropathy caused by permanent intolerance to gluten, is cytokine production by intestinal T lymphocytes. Prerequisites for contracting CD are that the individual carries the MHC class II alleles HLA-DQ2 and/or HLA-DQ8 and is exposed to gluten in the diet. Dysbiosis in the resident microbiota has been suggested to be another risk factor for CD. In fact, rod shaped bacteria adhering to the small intestinal mucosa were frequently seen in patients with CD during the “Swedish CD epidemic” and bacterial candidates could later be isolated from patients born during the epidemic suggesting long-lasting changes in the gut microbiota. Interleukin-17A (IL-17A) plays a role in both inflammation and anti-bacterial responses. In active CD IL-17A was produced by both CD8⁺ T cells (Tc17) and CD4⁺ T cells (Th17), with intraepithelial Tc17 cells being the dominant producers. Gluten peptides as well as CD associated bacteria induced IL-17A responses in ex vivo challenged biopsies from patients with inactive CD. The IL-17A response was suppressed in patients born during the epidemic when a mixture of CD associated bacteria was added to gluten, while the reverse was the case in patients born after the epidemic. Under these conditions Th17 cells were the dominant producers. Thus Tc17 and Th17 responses to gluten and bacteria seem to pave the way for the chronic disease with interferon-γ-production by intraepithelial Tc1 cells and lamina propria Th1 cells. The CD associated bacteria and the dysbiosis they might cause in the resident microbiota may be a risk factor for CD either by directly influencing the immune responses in the mucosa or by enhancing inflammatory responses to gluten.

Gastrointestinal microbiota and some children diseases: a review

The bacterial colonization is defined immediately after birth, through direct contact with maternal microbiota and may be influenced during lactation. There is emerging evidence indicating that quantitative and qualitative changes on gut microbiota contribute to alterations in the mucosal activation of immune system leading to intra- or extra-intestinal diseases. A balance between pathogenic and beneficial microbiota throughout childhood and adolescence is important to gastrointestinal health, including protection against pathogens, inhibition of pathogens, nutrient processing (synthesis of vitamin K), stimulation of angiogenesis, and regulation of host fat storage. Probiotics can promote an intentional modulation of intestinal microbiota favoring the health of the host. This paper is a review about modulation of intestinal microbiota on prevention and adjuvant treatment of pediatric gastrointestinal diseases.

HLA-DQA1 and HLA-DQB1 in Celiac disease predisposition: practical implications of the HLA molecular typing

Celiac disease (CD) is a multifactorial disorder with an estimated prevalence in Europe and USA of 1:100 and a female:male ratio of approximately 2:1. The disorder has a multifactorial etiology in which the triggering environmental factor, the gluten, and the main genetic factors, Human Leukocyte Antigen (HLA)-DQA1 and HLA-DQB1 loci, are well known. About 90-95% of CD patients carry DQ2.5 heterodimers, encoded by DQA1*05 and DQB1*02 alleles both in cis or in trans configuration, and DQ8 molecules, encoded by DQB1*03:02 generally in combination with DQA1*03 variant. Less frequently, CD occurs in individuals positive for the DQ2.x heterodimers (DQA1≠*05 and DQB1*02) and very rarely in patients negative for these DQ predisposing markers. HLA molecular typing for Celiac disease is, therefore, a genetic test with a negative predictive value. Nevertheless, it is an important tool able to discriminate individuals genetically susceptible to CD, especially in at-risk groups such as first-degree relatives (parents, siblings and offspring) of patients and in presence of autoimmune conditions (type 1 diabetes, thyroiditis, multiple sclerosis) or specific genetic disorders (Down, Turner or Williams syndromes).