The role of the intestinal microbiota in the development of atopic disorders

Faecalibacterium prausnitzii subspecies-level dysbiosis in the human gut microbiome underlying atopic dermatitis

BACKGROUND

Atopic dermatitis (AD) is a serious global epidemic associated with a modern lifestyle.

OBJECTIVE

Although aberrant interactions between gut microbes and the intestinal immune system have been implicated in this skin disease, the nature of the microbiome dysfunction underlying the disease remains unclear.

METHODS

The gut microbiome from 132 subjects, including 90 patients with AD, was analyzed by using 16S rRNA gene and metagenome sequence analyses. Reference genomes from the Human Microbiome Project and the KEGG Orthology database were used for metagenome analyses. Short-chain fatty acids in fecal samples were compared by using gas chromatographic-mass spectrometric analyses.

RESULTS

We show that enrichment of a subspecies of the major gut species Faecalibacterium prausnitzii is strongly associated with AD. In addition, the AD microbiome was enriched in genes encoding the use of various nutrients that could be released from damaged gut epithelium, reflecting a bloom of auxotrophic bacteria. Fecal samples from patients with AD showed decreased levels of butyrate and propionate, which have anti-inflammatory effects. This is likely a consequence of an intraspecies compositional change in F prausnitzii that reduces the number of high butyrate and propionate producers, including those related to the strain A2-165, a lack of which has been implicated in patients with Crohn disease.

CONCLUSIONS

The data suggest that feedback interactions between dysbiosis in F prausnitzii and dysregulation of gut epithelial inflammation might underlie the chronic progression of AD by resulting in impairment of the gut epithelial barrier, which ultimately leads to aberrant TH2-type immune responses to allergens in the skin.

Safety of a New Amino Acid Formula in Infants Allergic to Cow's Milk and Intolerant to Hydrolysates

OBJECTIVES

Amino acid-based formulas (AAFs) are recommended for children with cow's-milk allergy (CMA) failing to respond to extensively hydrolysed formulas (eHFs). We evaluated the effects of a new thickened AAF (TAAF, Novalac), containing a pectin-based thickener, and a reference AAF (RAAF, Neocate) on allergy symptoms and safety, through blood biochemistry analysis and growth.

METHODS

Infants (ages < 18 months) with CMA symptoms failing to respond to eHFs were randomised in a double-blind manner to receive TAAF or RAAF for 3 months. All of the infants were then fed TAAF for 3 additional months. Paediatric visits occurred at 1, 3, and 6 months. Blood samples were collected at inclusion and 3 months.

RESULTS

Results at 1 month were previously described. The 75 infants with proven CMA and eHF intolerance tolerated their allocated formula. At 3 months, the dominant allergic symptom had disappeared in 76.2% of the infants with TAAF and in 51.5% of the infants with RAAF (P = 0.026). The Scoring Atopic Dermatitis Index significantly improved more with TAAF than with RAAF (-27.3 ± 2.3 vs -20.8 ± 2.2, P = 0.048). Of the infants, 92.9% had normal stools (soft or formed consistency) with TAAF vs 75.8% with RAAF (P = 0.051). More infants in TAAF group had better quality of nighttime sleep (P = 0.036) and low frequency of irritability signs (P < 0.001). With both formulas, all of the biochemical parameters were within normal ranges. There were no differences between the 2 groups in any of the anthropometric z scores.

CONCLUSIONS

The new TAAF was tolerated by all of the infants with CMA and intolerance to eHFs. Anthropometric and clinical data showed that both formulas were safe.

Maternal group B Streptococcus and the infant gut microbiota

Early patterns of gut colonization may predispose children to adult disease. Exposures in utero and during delivery are associated with the infant gut microbiome. Although ~35% of women carry group B strep (GBS; Streptococcus agalactiae) during pregnancy, it is unknown if GBS presence influences the infant gut microbiome. As part of a population-based, general risk birth cohort, stool specimens were collected from infant's diapers at research visits conducted at ~1 and 6 months of age. Using the Illumina MiSeq (San Diego, CA) platform, the V4 region of the bacterial 16S rRNA gene was sequenced. Infant gut bacterial community compositional differences by maternal GBS status were evaluated using permutational multivariate analysis of variance. Individual operational taxonomic units (OTUs) were tested using a zero-inflated negative binomial model. Data on maternal GBS and infant gut microbiota from either 1 (n=112) or 6-month-old stool (n=150) specimens was available on 262 maternal-child pairs. Eighty women (30.5%) were GBS+, of who 58 (72.5%) were given intrapartum antibiotics. After adjusting for maternal race, prenatal antifungal use and intrapartum antibiotics, maternal GBS status was statistically significantly associated with gut bacterial composition in the 6 month visit specimen (Canberra R 2=0.008, P=0.008; Unweighted UniFrac R 2=0.010, P=0.011). Individual OTU tests revealed that infants of GBS+ mothers were significantly enriched for specific members of the Clostridiaceae, Ruminococcoceae, and Enterococcaceae in the 6 month specimens compared with infants of GBS- mothers. Whether these taxonomic differences in infant gut microbiota at 6 months lead to differential predisposition for adult disease requires additional study.

Selective enrichment of commensal gut bacteria protects against Citrobacter rodentium-induced colitis

The intestinal microbiota plays a key role in shaping the host immune system. Perturbation of gut microbial composition, termed dysbiosis, is associated with an increased susceptibility to intestinal pathogens and is a hallmark of a number of inflammatory, metabolic, and infectious diseases. The prospect of mining the commensal gut microbiota for bacterial strains that can impact immune function represents an attractive strategy to counteract dysbiosis and resulting disease. In this study, we show that selective enrichment of commensal gut lactobacilli protects against the murine pathogen Citrobacter rodentium, a well-characterized model of enteropathogenic and enterohemorrhagic Escherichia coli infection. The lactobacilli-enriched bacterial culture prevented the expansion of Gammaproteobacteria and Actinobacteria and was associated with improved indexes of epithelial barrier function (dextran flux), transmissible crypt hyperplasia, and tissue inflammatory cytokine levels. Moreover, cultivation of gut bacteria from Citrobacter rodentium-infected mice reveals the differential capacity of bacterial subsets to mobilize neutrophil oxidative burst and initiate the formation of weblike neutrophil extracellular traps. Our findings highlight the beneficial effects of a lactobacilli-enriched commensal gut microenvironment and, in the context of an intestinal barrier breach, the ability of neutrophils to immobilize both commensal and pathogenic bacteria.

Oral treatment with enrofloxacin early in life promotes Th2-mediated immune response in mice

BACKGROUND

Th2 lymphocytes play a crucial role in the development of allergy. These pathologies are caused by coordinated production of the cytokines IL-4, IL-5 and IL-13 that regulate the activity of eosinophils, basophils and B cells. According to the 'hygiene hypothesis', the reduced exposure to microorganisms favors allergy occurrence. The advances in medicine in the field of infection therapy promoted an increasing application of antibiotics which, apart from eliminating pathogens, also partially eliminate the microbiota.

METHODS

Epicutaneous (EC) immunization with ovalbumin (OVA) followed by OVA challenge was used to study the influence of partial gut flora depletion by oral treatment with enrofloxacin on type-2 immune response.

RESULTS

Current work describes the influence of enrofloxacin application on anti-OVA antibody production and cytokine synthesis in young and adult mice. Immune response in adult mice is less sensitive to modification of natural gut flora. We observed that enrofloxacin treatment of adult mice leads to significant decrease of anti-OVA IgG2a production while synthesis of anti-OVA IgE was not changed. The production of type-1 (IFN-γ), type-2 (IL-4, IL-5, IL-10, IL-13) and Th17-associated (IL-17A) cytokines was inhibited. On the other hand, treatment of young mice with enrofloxacin significantly upregulates the production of anti-OVA IgE and inhibits the secretion of anti-OVA IgG2a antibodies. Additionally, treatment with enrofloxacin early in life prior to OVA immunization results in increased production of type-2 (IL-4, IL-10 and IL-13) cytokines.

CONCLUSION

Our results clearly indicate that the immune system is more vulnerable to decreased bacterial exposure early in life that may promote development of allergy.

Probiotic fermented milk consumption modulates the allergic process induced by ovoalbumin in mice

Orally administered probiotic micro-organisms are able to regulate the exacerbated immune response during the antigenic sensitisation process. The aim of the present study was to evaluate the potential efficacy of probiotic fermented milk (PFM) in preventing or treating allergy in an experimental model, and to investigate its underlying mechanisms. Ovoalbumin (OVA)-sensitised BALB/c mice were fed with PFM before the sensitisation procedure or fed continuously with PFM. At 7 and 15 d post-sensitisation, anti-OVA-specific IgE, IgG, IgG1 and IgG2a concentrations were measured in the serum and broncho-alveolar lavage fluid (BALF). Concentrations of interferon-γ (IFN-γ), IL-4, IL-10 and total secretory IgA (S-IgA) were measured in the supernatants of macerated lungs or in the BALF. The levels of IgA+, CD4+ and CD8+ T lymphocytes and F4/80+ cells were measured in the lungs by immunofluorescence. Inducible CD4+/CD25/Foxp3+ regulatory T (Treg) cells were evaluated in the lungs. PFM shifted the T helper (Th)2 profile response towards a Th1 response that led to the production of IgG instead of IgE, with increasing levels of IL-10 and IFN-γ that play an important role in immunomodulation exerted by PFM administration in sensitised mice. Anti-OVA-specific IgE levels were significantly decreased; however, there was no modification in the levels of anti-OVA-specific IgG and total S-IgA. PFM did not influence Treg cells in treated mice. Consumption of PFM could be a promising strategy in the amelioration of airway allergies, considering that the effect is mediated by the production of IgG through the activation of Th1 instead of the direct activation of Th2 cells to produce IgE.

Differential induction of total IgE by two Salmonella enterica serotypes

The main goal of this study was to establish how the inflammation caused by infection with two different Salmonella enterica serotypes, S. Typhimurium and S. Enteritidis, may lead to the predisposition to allergy as measured by total IgE level in the blood. Infection by S. Typhimurium did not affect the systemic IgE concentration while in S. Enteritidis-infected patients there was a significant 3.5-fold increase. This effect was especially profound in patients >4 years old, with up to the 8-fold increase above the norm. The degree of dysbiosis in these two infections measured with the comparative counts of cultivated bacteria showed an inverse relationship with the IgE concentration. Earlier we reported the elevated level of IL-17 in patients infected by S. Enteritidis. In the current study a significant correlation was found between the concentrations of IL-17 and IgE suggesting a possible role played by this cytokine in triggering the production of IgE in response to S. Enteritidis infection.

Microbiota in allergy and asthma and the emerging relationship with the gut microbiome

Asthma and atopy, classically associated with hyper-activation of the T helper 2 (Th2) arm of adaptive immunity, are among the most common chronic illnesses worldwide. Emerging evidence relates atopy and asthma to the composition and function of the human microbiome, the collection of microbes that reside in and on and interact with the human body. The ability to interrogate microbial ecology of the human host is due in large part to recent technological developments that permit identification of microbes and their products using culture-independent molecular detection techniques. In this review we explore the roles of respiratory, gut, and environmental microbiomes in asthma and allergic disease development, manifestation, and attenuation. Though still a relatively nascent field of research, evidence to date suggests that the airway and/or gut microbiome may represent fertile targets for prevention or management of allergic asthma and other diseases in which adaptive immune dysfunction is a prominent feature.

Histamine and Skin Barrier: Are Histamine Antagonists Useful for the Prevention or Treatment of Atopic Dermatitis?

Atopic Dermatitis (AD), the most common chronic inflammatory skin disease, is characterized by an overactive immune response to a host of environmental allergens and dry, itchy skin. Over the past decade important discoveries have demonstrated that AD develops in part from genetic and/or acquired defects in the skin barrier. Histamine is an aminergic neurotransmitter involved in physiologic and pathologic processes such as pruritus, inflammation, and vascular leak. Enhanced histamine release has been observed in the skin of patients with AD and antihistamines are often prescribed for their sedating and anti-itch properties. Recent evidence suggests that histamine also inhibits the terminal differentiation of keratinocytes and impairs the skin barrier, raising the question whether histamine might play a role in AD barrier impairment. This, coupled with the notion that histamine’s effects mediated through the recently identified histamine receptor H4R, may be important in allergic inflammation, has renewed interest in this mediator in allergic diseases. In this paper we summarize the current knowledge on histamine and histamine receptor antagonists in AD and skin barrier function.

Why is initial bacterial colonization of the intestine important to infants' and children's health?

Microbial colonization of the infant occurs during a critical time window for immune and gastrointestinal development. Infant colonization sets the stage for the adult microbiome. This review is a broad survey of the factors affecting infant colonization and the downstream effects on gastrointestinal health and disease. Major topics affecting colonization include initial inoculation dependent on birth mode, the impact of breast-feeding, and inside-out modulation of the developing microbiome by the immune system. Major outcomes of colonization include the timing-dependent education of the neonatal immune system, which is interconnected with barrier function and metabolism. These all engage in further continuing cross-talk with the microbiome, genetics, and nutrition. This review also briefly examines mechanisms of disease resulting from disrupted colonization as well as nutritional and microbial therapies.

Long-lasting effects of early-life antibiotic treatment and routine animal handling on gut microbiota composition and immune system in pigs

BACKGROUND

In intensive pig husbandry systems, antibiotics are frequently administrated during early life stages to prevent respiratory and gastro-intestinal tract infections, often in combination with stressful handlings. The immediate effects of these treatments on microbial colonization and immune development have been described recently. Here we studied whether the early life administration of antibiotics has long-lasting effects on the pig's intestinal microbial community and on gut functionality.

METHODOLOGY/PRINCIPAL FINDINGS

To investigate the long-lasting effect of early-life treatment, piglets were divided into three different groups receiving the following treatments: 1) no antibiotics and no stress, 2) antibiotics and no stress, and 3) antibiotics and stress. All treatments were applied at day four after birth. Sampling of jejunal content for community scale microbiota analysis, and jejunal and ileal tissue for genome-wide transcription profiling, was performed at day 55 (~8 weeks) and day 176 (~25 weeks) after birth. Antibiotic treatment in combination with or without exposure to stress was found to have long-lasting effects on host intestinal gene expression involved in a multitude of processes, including immune related processes.

CONCLUSIONS/SIGNIFICANCE

The results obtained in this study indicate that early life (day 4 after birth) perturbations have long-lasting effects on the gut system, both in gene expression (day 55) as well as on microbiota composition (day 176). At day 55 high variance was observed in the microbiota data, but no significant differences between treatment groups, which is most probably due to the newly acquired microbiota during and right after weaning (day 28). Based on the observed difference in gene expression at day 55, it is hypothesized that due to the difference in immune programming during early life, the systems respond differently to the post-weaning newly acquired microbiota. As a consequence, the gut systems of the treatment groups develop into different homeostasis.

The role of the early-life environment in the development of allergic disease

A consensus has been reached that the development of allergic disorders is strongly influenced by early life exposures. An overview of several prenatal and early life factors that have been investigated for their associations with development of childhood allergy is presented. Delivery mode, the gut microbiome, vitamin D, folate, breastfeeding, pets, antibiotics, environmental tobacco smoke, and airborne traffic pollutants are discussed. Although many studies suggest an effect, overall, no risk factors clearly increase or reduce the risk of allergic outcomes.

The intestinal microbiota: its role in health and disease

The intestinal microbiota (previously referred to as "intestinal flora") has entered the focus of research interest not only in microbiology but also in medicine. Huge progress has been made with respect to the analysis of composition and functions of the human microbiota. An "imbalance" of the microbiota, frequently also called a "dysbiosis," has been associated with different diseases in recent years. Crohn's disease and ulcerative colitis as two major forms of inflammatory bowel disease, irritable bowel syndrome (IBS) and some infectious intestinal diseases such as Clostridium difficile colitis feature a dysbiosis of the intestinal flora. Whereas this is somehow expected or less surprising, an imbalance of the microbiota or an enrichment of specific bacterial strains in the flora has been associated with an increasing number of other diseases such as diabetes, metabolic syndrome, non-alcoholic fatty liver disease or steatohepatitis and even psychiatric disorders such as depression or multiple sclerosis. It is important to understand the different aspects of potential contributions of the microbiota to pathophysiology of the mentioned diseases.

CONCLUSION

With the present manuscript, we aim to summarize the current knowledge and provide an overview of the different concepts on how bacteria contribute to health and disease in animal models and-more importantly-humans. In addition, it has to be borne in mind that we are only at the very beginning to understand the complex mechanisms of host-microbial interactions.

Understanding host-adherent-invasive Escherichia coli interaction in Crohn's disease: opening up new therapeutic strategies

A trillion of microorganisms colonize the mammalian intestine. Most of them have coevolved with the host in a symbiotic relationship and some of them have developed strategies to promote their replication in the presence of competing microbiota. Recent evidence suggests that perturbation of the microbial community favors the emergence of opportunistic pathogens, in particular adherent-invasive Escherichia coli (AIEC) that can increase incidence and severity of gut inflammation in the context of Crohn's disease (CD). This review will report the importance of AIEC as triggers of intestinal inflammation, focusing on their impact on epithelial barrier function and stimulation of mucosal inflammation. Beyond manipulation of immune response, restoration of gut microbiota as a new treatment option for CD patients will be discussed.

Early development of the gut microbiota and immune health

In recent years, the increase in human microbiome research brought about by the rapidly evolving “omic” technologies has established that the balance among the microbial groups present in the human gut, and their multipronged interactions with the host, are crucial for health. On the other hand, epidemiological and experimental support has also grown for the ‘early programming hypothesis’, according to which factors that act in utero and early in life program the risks for adverse health outcomes later on. The microbiota of the gut develops during infancy, in close interaction with immune development, and with extensive variability across individuals. It follows that the specific process of gut colonization and the microbe-host interactions established in an individual during this period have the potential to represent main determinants of life-long propensity to immune disease. Although much remains to be learnt on the progression of events by which the gut microbiota becomes established and initiates its intimate relationships with the host, and on the long-term repercussions of this process, recent works have advanced significatively in this direction.

The intestinal microbiome in early life: health and disease

Human microbial colonization begins at birth and continues to develop and modulate in species abundance for about 3 years, until the microbiota becomes adult-like. During the same time period, children experience significant developmental changes that influence their health status as well as their immune system. An ever-expanding number of articles associate several diseases with early-life imbalances of the gut microbiota, also referred to as gut microbial dysbiosis. Whether early-life dysbiosis precedes and plays a role in disease pathogenesis, or simply originates from the disease process itself is a question that is beginning to be answered in a few diseases, including IBD, obesity, and asthma. This review describes the gut microbiome structure and function during the formative first years of life, as well as the environmental factors that determine its composition. It also aims to discuss the recent advances in understanding the role of the early-life gut microbiota in the development of immune-mediated, metabolic, and neurological diseases. A greater understanding of how the early-life gut microbiota impacts our immune development could potentially lead to novel microbial-derived therapies that target disease prevention at an early age.

The first thousand days - intestinal microbiology of early life: establishing a symbiosis

The development of the intestinal microbiota in the first years of life is a dynamic process significantly influenced by early-life nutrition. Pioneer bacteria colonizing the infant intestinal tract and the gradual diversification to a stable climax ecosystem plays a crucial role in establishing host-microbe interactions essential for optimal symbiosis. This colonization process and establishment of symbiosis may profoundly influence health throughout life. Recent developments in microbiologic cultivation-independent methods allow a detailed view of the key players and factors involved in this process and may further elucidate their roles in a healthy gut and immune maturation. Aberrant patterns may lead to identifying key microbial signatures involved in developing immunologic diseases into adulthood, such as asthma and atopic diseases. The central role of early-life nutrition in the developmental human microbiota, immunity, and metabolism offers promising strategies for prevention and treatment of such diseases. This review provides an overview of the development of the intestinal microbiota, its bidirectional relationship with the immune system, and its role in impacting health and disease, with emphasis on allergy, in early life.

Blowing on embers: commensal microbiota and our immune system

Vertebrates have co-evolved with microorganisms resulting in a symbiotic relationship, which plays an important role in health and disease. Skin and mucosal surfaces are colonized with a diverse population of commensal microbiota, over 1000 species, outnumbering the host cells by 10-fold. In the past 40 years, studies have built on the idea that commensal microbiota is in constant contact with the host immune system and thus influence immune function. Recent studies, focusing on mutualism in the gut, have shown that commensal microbiota seems to play a critical role in the development and homeostasis of the host immune system. In particular, the gut microbiota appears to direct the organization and maturation of lymphoid tissues and acts both locally and systemically to regulate the recruitment, differentiation, and function of innate and adaptive immune cells. While the pace of research in the area of the mucosal–immune interface has certainly intensified over the last 10 years, we are still in the early days of this field. Illuminating the mechanisms of how gut microbes shape host immunity will enhance our understanding of the causes of immune-mediated pathologies and improve the design of next-generation vaccines. This review discusses the recent advances in this field, focusing on the close relationship between the adaptive immune system and commensal microbiota, a constant and abundant source of foreign antigens.

Microbiome manipulation modifies sex-specific risk for autoimmunity

Despite growing evidence for a causal role of environmental factors in autoimmune diseases including the rise in disease frequencies over the past several decades we lack an understanding of how particular environmental exposures modify disease risk. In addition, many autoimmune diseases display sex-biased incidence, with females being disproportionately affected but the mechanisms underlying this sex bias remain elusive. Emerging evidence suggests that both host metabolism and immune function is crucially regulated by the intestinal microbiome. Recently, we showed that in the non-obese diabetic (NOD) mouse model of Type 1 Diabetes (T1D), the gut commensal microbial community strongly impacts the pronounced sex bias in T1D risk by controlling serum testosterone and metabolic phenotypes (1). Here we present new data in the NOD model that explores the correlations between microbial phylogeny, testosterone levels, and metabolic phenotypes, and discuss the future of microbiome-centered analysis and microbe-based therapeutic approaches in autoimmune diseases.

Toll-like receptor 2 activation by β2→1-fructans protects barrier function of T84 human intestinal epithelial cells in a chain length-dependent manner

Dietary fiber intake is associated with lower incidence and mortality from disease, but the underlying mechanisms of these protective effects are unclear. We hypothesized that β2→1-fructan dietary fibers confer protection on intestinal epithelial cell barrier function via Toll-like receptor 2 (TLR2), and we studied whether β2→1-fructan chain-length differences affect this process. T84 human intestinal epithelial cell monolayers were incubated with 4 β2→1-fructan formulations of different chain-length compositions and were stimulated with the proinflammatory phorbol 12-myristate 13-acetate (PMA). Transepithelial electrical resistance (TEER) was analyzed by electric cell substrate impedance sensing (ECIS) as a measure for tight junction-mediated barrier function. To confirm TLR2 involvement in barrier modulation by β2→1-fructans, ECIS experiments were repeated using TLR2 blocking antibody. After preincubation of T84 cells with short-chain β2→1-fructans, the decrease in TEER as induced by PMA (62.3 ± 5.2%, P < 0.001) was strongly attenuated (15.2 ± 8.8%, P < 0.01). However, when PMA was applied first, no effect on recovery was observed during addition of the fructans. By blocking TLR2 on the T84 cells, the protective effect of short-chain β2→1-fructans was substantially inhibited. Stimulation of human embryonic kidney human TLR2 reporter cells with β2→1-fructans induced activation of nuclear factor kappa-light-chain-enhancer of activated B cells, confirming that β2→1-fructans are specific ligands for TLR2. To conclude, β2→1-fructans exert time-dependent and chain length-dependent protective effects on the T84 intestinal epithelial cell barrier mediated via TLR2. These results suggest that TLR2 located on intestinal epithelial cells could be a target of β2→1-fructan-mediated health effects.

Effect of antibiotic use and mold exposure in infancy on allergic rhinitis in susceptible adolescents

BACKGROUND

Antibiotic use in infancy induces alteration in intestinal microbiota and is associated with the development of allergic diseases. Mold exposure is also associated with allergic diseases. Genetic susceptibility may interact with specific environmental factors in allergic disease development.

OBJECTIVE

To investigate independent and combined effects of antibiotic use and mold exposure in infancy on the risk of allergic rhinitis (AR) in adolescents.

METHODS

Data on AR and environmental factors were collected using the International Study of Asthma and Allergies in Childhood questionnaire from 7,389 adolescents from Seoul, Korea. TaqMan genotyping was performed for interleukin 13 (IL-13) (rs20541) and Toll-like receptor 4 (rs1927911) polymorphisms in 1,395 adolescents.

RESULTS

Age, parental history of AR, antibiotic use in infancy, and pet ownership during pregnancy or infancy were associated with an increased risk of current AR (diagnosis of AR and symptoms of AR within the preceding 12 months). Having older siblings was a protective effect. The adjusted odds ratio (aOR) for current AR for combined antibiotic use and mold exposure in infancy was 1.45 (95% confidence interval [CI], 1.01-2.09). For each factor separately, aORs were 1.25 (95% CI, 1.04-1.50) and 0.99 (95% CI, 0.75-1.31), respectively. Antibiotic and mold exposure in infancy, GA or AA genotypes of IL-13 (rs20541) (aOR 4.53; 95% CI, 1.66-12.38; P for interaction = .05), and CT+TT genotype of Toll-like receptor 4 (rs1927911) (aOR, 3.20; 95% CI, 1.24-8.26; P for interaction = .18) increased the risk of current AR.

CONCLUSION

Antibiotic use and mold exposure in infancy have additive effects on the risk of current AR in genetically susceptible adolescents. Gene-environment interactions between IL-13 (rs20541) and antibiotics or mold may play a role in AR.

Early-life environmental variation affects intestinal microbiota and immune development in new-born piglets

Background

Early-life environmental variation affects gut microbial colonization and immune competence development; however, the timing and additional specifics of these processes are unknown. The impact of early-life environmental variations, as experienced under real life circumstances, on gut microbial colonization and immune development has not been studied extensively so far. We designed a study to investigate environmental variation, experienced early after birth, to gut microbial colonization and intestinal immune development.

Methodology/Principal Findings

To investigate effects of early-life environmental changes, the piglets of 16 piglet litters were divided into 3 groups per litter and experimentally treated on day 4 after birth. During the course of the experiment, the piglets were kept with their mother sow. Group 1 was not treated, group 2 was treated with an antibiotic, and group 3 was treated with an antibiotic and simultaneously exposed to several routine, but stressful management procedures, including docking, clipping and weighing. Thereafter, treatment effects were measured at day 8 after birth in 16 piglets per treatment group by community-scale analysis of gut microbiota and genome-wide intestinal transcriptome profiling. We observed that the applied antibiotic treatment affected the composition and diversity of gut microbiota and reduced the expression of a large number of immune-related processes. The effect of management procedures on top of the use of an antibiotic was limited.

Conclusions/Significance

We provide direct evidence that different early-life conditions, specifically focusing on antibiotic treatment and exposure to stress, affect gut microbial colonization and intestinal immune development. This reinforces the notion that the early phase of life is critical for intestinal immune development, also under regular production circumstances.

Microbial succession in the gut: directional trends of taxonomic and functional change in a birth cohort of Spanish infants

In spite of its major impact on life-long health, the process of microbial succession in the gut of infants remains poorly understood. Here, we analyze the patterns of taxonomic and functional change in the gut microbiota during the first year of life for a birth cohort of 13 infants. We detect that individual instances of gut colonization vary in the temporal dynamics of microbiota richness, diversity, and composition at both functional and taxonomic levels. Nevertheless, trends discernible in a majority of infants indicate that gut colonization occurs in two distinct phases of succession, separated by the introduction of solid foods to the diet. This change in resource availability causes a sharp decrease in the taxonomic richness of the microbiota due to the loss of rare taxa (p = 2.06e-9), although the number of core genera shared by all infants increases substantially. Moreover, although the gut microbial succession is not strictly deterministic, we detect an overarching directionality of change through time towards the taxonomic and functional composition of the maternal microbiota. Succession is however not complete by the one year mark, as significant differences remain between one-year-olds and their mothers in terms of taxonomic (p = 0.009) and functional (p = 0.004) microbiota composition, and in taxonomic richness (p = 2.76e-37) and diversity (p = 0.016). Our results also indicate that the taxonomic composition of the microbiota shapes its functional capacities. Therefore, the observed inter-individual variability in taxonomic composition during succession is not fully compensated by functional equivalence among bacterial genera and may have important physiological consequences. Finally, network analyses suggest that positive interactions among core genera during community assembly contribute to ensure their permanence within the gut, and highlight an expansion of complexity in the interactions network as the core of taxa shared by all infants grows following the introduction of solid foods.

Although knowledge of the complex community of microbes that inhabits the human gut is constantly increasing, the successional process through which it develops during infancy remains poorly understood. Particularly, although gut microbiota composition is known to vary through time among infants, the effect of this variability on the functional capacities of the community has not been previously explored. We simultaneously analyze the taxonomic and functional development of the gut microbiota in a birth cohort of healthy infants during the first year of life, showing that individual instances of gut colonization vary in their temporal dynamics and that clear parallelisms exist between functional and taxonomic change. Therefore, taxonomic composition shapes the functional capacities of the microbiota, and, consequently, successional variability may affect host physiology, metabolism and immunity. Nevertheless, we detect some overarching trends in microbiota development, such as the existence of two distinct phases of succession, separated by the introduction of solid foods, and a strong directionality of change towards the taxonomic and functional composition of the maternal microbiota. Understanding the commonalities and differences among individual patterns of gut colonization in healthy infants will enable a better definition of the deviations in this process that result in microbiota imbalances and disease.

Oral application of bacterial lysate in infancy diminishes the prevalence of atopic dermatitis in children at risk for atopy

Numerous interventions such as avoidance of food allergens, prolonged breast feeding and supplementation of pro-and/or prebiotics have been tried as primary prevention of atopic dermatitis. Recent data suggest that prevention of infantile eczema is possible in a subgroup of children by feeding bacterial lysates early in life. Bacterial lysates of Escherichia coli and Enterococcus faecalis were found to impair allergic immune responses in rats. An interventional trial in 606 infants at risk for atopy showed a reduction of atopic dermatitis at the end of the treatment phase (month 2 until month 7) of 50% in a subgroup of children with single heredity for atopy. This was even more pronounced in the group of children with paternal heredity for atopy. This effect was still seen at age 1 year. There was no effect on food sensitisation. In conclusion, an immune modulation in terms of prevention of atopic dermatitis in infancy if single atopic family history is present seems to be possible by feeding bacterial lysates early in life.

Aerosol Mycobacterium tuberculosis infection causes rapid loss of diversity in gut microbiota

Mycobacterium tuberculosis is an important human pathogen, and yet diagnosis remains challenging. Little research has focused on the impact of M. tuberculosis on the gut microbiota, despite the significant immunological and homeostatic functions of the gastrointestinal tract. To determine the effect of M. tuberculosis infection on the gut microbiota, we followed mice from M. tuberculosis aerosol infection until death, using 16S rRNA sequencing. We saw a rapid change in the gut microbiota in response to infection, with all mice showing a loss and then recovery of microbial community diversity, and found that pre-infection samples clustered separately from post-infection samples, using ecological beta-diversity measures. The effect on the fecal microbiota was observed as rapidly as six days following lung infection. Analysis of additional mice infected by a different M. tuberculosis strain corroborated these results, together demonstrating that the mouse gut microbiota significantly changes with M. tuberculosis infection.

rBet v 1 immunotherapy of sensitized mice with Streptococcus thermophilus as vehicle and adjuvant

Lactobacilli are able to induce upregulation of co-stimulatory molecules in DCs with Th1 cytokines production and increase in Treg activity. This could explain the observed effectiveness of the prolonged administration of lactobacilli in the prevention of allergic disorders in infants and envisage the possible use of bacteria expressing the allergen for the specific immunotherapy of allergic diseases. Hence, we evaluated Streptococcus thermophilus (ST) expressing rBet v 1 as allergen delivery tool and adjuvant factor for immunotherapy in Betv1-sensitized mice. rBet v 1 gene was introduced and expressed in ST (ST[rBet v 1]). BALB/c mice were sensitized with rBet v 1 and then treated with either ST alone, ST[rBet v 1], or the combination of ST and rBet v 1, for 20 days. After 2 aerosol challenges, Treg frequency, in vitro allergen-induced cytokines, rBet v 1-specific IgE and IgG2a, and bronchial histology were made in harvested spleen, sera, and lung. Results were compared with those obtained from not-treated/sensitized mice. ST[rBet v 1] induced immunological and histological changes typical of successful SIT: increased frequency of Tregs and expression of Foxp3; decreased allergen-specific IgE/IgG2a ratio; decrease of in vitro rBet v 1-induced IL-4 from spleen cells; increased allergen-induced IL-10 and IFN-γ; drop of bronchial eosinophilia. ST and ST+rBet v 1 combination, even though induced a slight increase in the frequency of Tregs and moderate allergen-induced IL-10, were ineffective in reducing bronchial eosinophilia, allergen induced IL-4 and rBet v 1-specific IgE/IgG2a ratio. ST[rBet v 1] has tolerogenic and Th-1 skewing properties and efficiently delivers the allergen to the gut immune-system restraining and readdressing the established specific Th2 response toward the allergen in mice.

Atopy and the gastrointestinal tract--a review of a common association in unexplained gastrointestinal disease

In addition to diseases conventionally associated with atopy there is increasing recognition that atopy is also linked to a spectrum of gastrointestinal (GI) manifestations, including food allergy, primary eosinophilic GI disease, functional gastrointestinal disorders, gluten interactions, gastroesophageal reflux disease and inflammatory bowel disease. These associations may be underpinned by shared genetic susceptibilities, initiation of related immune pathways and common patterns of exposure to environmental cues, including allergen/pathogen encounters and variations in the composition of the intestinal microbiota. Further scrutiny of GI diseases with prominent allergic-type immune responses may yet redefine treatment paradigms for these common and important atopy-associated diseases. Looking forward, interventions by manipulation of the microbiota or host immune responses hold promise, but there is still room for further exploration of this novel field of host susceptibility, host-microbe interactions and atopy-associated GI diseases.

Febrile and gynecological infections during pregnancy are associated with a greater risk of childhood eczema

BACKGROUND

Mounting evidence suggests that fetal exposures may exert long-term effects on the function of the skin and of the immune system. This study aimed at assessing whether maternal complications during pregnancy are associated with an increased risk of eczema during childhood.

METHODS

The associations between hypertension/preeclampsia, febrile infections, or gynecological infections during pregnancy and the occurrence of childhood eczema were studied in a population (n = 3907) of children, aged 3-14 yrs, living in Italy. Their parents filled in a standardized questionnaire about the presence of children's eczema and the events that occurred during pregnancy, birth, and the first year of the child's life.

RESULTS

7.7%, 3.8%, and 6.1% of the pregnancies were complicated by hypertension/preeclampsia, febrile infections, and gynecological infections, respectively. The prevalence of eczema was significantly higher in children born to mothers who had experienced febrile (35.5% vs. 22.0%; p < 0.001) or gynecological infections (35.3% vs. 21.6%; p < 0.001) compared with those born to mothers who had not suffered from that specific pregnancy complication, while hypertension/preeclampsia was not significantly associated with childhood eczema. After adjusting for potential confounders, the risk of eczema was significantly higher in children born to mothers who reported febrile infections during the 1st trimester (OR: 2.32; 95% CI: 1.11-4.82) and gynecological infections during the 3rd trimester of pregnancy (OR: 2.73; 95% CI:1.73-4.31).

CONCLUSIONS

Fetal exposure to febrile and gynecological infections might enhance the risk of eczema in the offspring, especially when occurring in specific trimesters of pregnancy. These findings suggest that febrile and gynecological infections might interfere with fetal and perinatal programming of the immune function and skin through different mechanisms.

Regulation of Intestinal Immune Responses through TLR Activation: Implications for Pro- and Prebiotics

The intestinal mucosa is constantly facing a high load of antigens including bacterial antigens derived from the microbiota and food. Despite this, the immune cells present in the gastrointestinal tract do not initiate a pro-inflammatory immune response. Toll-like receptors (TLRs) are pattern recognition receptors expressed by various cells in the gastrointestinal tract, including intestinal epithelial cells (IEC) and resident immune cells in the lamina propria. Many diseases, including chronic intestinal inflammation (e.g., inflammatory bowel disease), irritable bowel syndrome (IBS), allergic gastroenteritis (e.g., eosinophilic gastroenteritis and allergic IBS), and infections are nowadays associated with a deregulated microbiota. The microbiota may directly interact with TLR. In addition, differences in intestinal TLR expression in health and disease may suggest that TLRs play an essential role in disease pathogenesis and may be novel targets for therapy. TLR signaling in the gut is involved in either maintaining intestinal homeostasis or the induction of an inflammatory response. This mini review provides an overview of the current knowledge regarding the contribution of intestinal epithelial TLR signaling in both tolerance induction or promoting intestinal inflammation, with a focus on food allergy. We will also highlight a potential role of the microbiota in regulating gut immune responses, especially through TLR activation.

Food diversity in infancy and the risk of childhood asthma and allergies

BACKGROUND

Recently, the bacterial diversity of the intestinal flora and the diversity of various environmental factors during infancy have been linked to the development of allergies in childhood. Food is an important environmental exposure, but the role of food diversity in the development of asthma and allergies in childhood is poorly defined.

OBJECTIVE

We studied the associations between food diversity during the first year of life and the development of asthma and allergies by age 5 years.

METHODS

In a Finnish birth cohort we analyzed data on 3142 consecutively born children. We studied food diversity at 3, 4, 6, and 12 months of age. Asthma, wheeze, atopic eczema, and allergic rhinitis were measured by using the International Study of Asthma and Allergies in Childhood questionnaire at age 5 years.

RESULTS

By 3 and 4 months of age, food diversity was not associated with any of the allergic end points. By 6 months of age, less food diversity was associated with increased risk of allergic rhinitis but not with the other end points. By 12 months of age, less food diversity was associated with increased risk of any asthma, atopic asthma, wheeze, and allergic rhinitis.

CONCLUSION

Less food diversity during the first year of life might increase the risk of asthma and allergies in childhood. The mechanisms for this association are unclear, but increased dietary antigen exposure might contribute to this link.

Modulation of gut microbiota downregulates the development of food allergy in infancy

In humans, microbial colonisation of the intestine begins just after birth. However, development of the normal flora is a gradual process, which is initially determined by factors such as genetic aspects, the maternal-foetal interaction, place and mode of delivery, early feedings strategies, and the use of antibiotics. Current knowledge on the significance and impact of the gut microflora on the development of the gut immune system indicates that a close relationship between allergic sensitisation and the development of the intestinal microflora may occur in infancy. Intestinal micro-organisms could downregulate the allergic inflammation by counterbalancing type 2 T-helper cell responses and by enhancing allergen exclusion through an immunological response.

The murine lung microbiome in relation to the intestinal and vaginal bacterial communities

Background

This work provides the first description of the bacterial population of the lung microbiota in mice. The aim of this study was to examine the lung microbiome in mice, the most used animal model for inflammatory lung diseases such as COPD, cystic fibrosis and asthma.

Bacterial communities from broncho-alveolar lavage fluids and lung tissue were compared to samples taken from fecal matter (caecum) and vaginal lavage fluid from female BALB/cJ mice.

Results

Using a customized 16S rRNA sequencing protocol amplifying the V3-V4 region our study shows that the mice have a lung microbiome that cluster separately from mouse intestinal microbiome (caecum). The mouse lung microbiome is dominated by Proteobacteria, Firmicutes, Actinobacteria, Bacteroidetes and Cyanobacteria overlapping the vaginal microbiome. We also show that removal of host tissue or cells from lung fluid during the DNA extraction step has an impact on the resulting bacterial community profile. Sample preparation needs to be considered when choosing an extraction method and interpreting data.

Conclusions

We have consistently amplified bacterial DNA from mouse lungs that is distinct from the intestinal microbiome in these mice. The gut microbiome has been extensively studied for its links to development of disease. Here we suggest that also the lung microbiome could be important in relation to inflammatory lung diseases. Further research is needed to understand the contribution of the lung microbiome and the gut-lung axis to the development of lung diseases such as COPD and asthma.

Oral delivery of a probiotic induced changes at the nasal mucosa of seasonal allergic rhinitis subjects after local allergen challenge: a randomised clinical trial

Objective

To determine effects of probiotic consumption on clinical and immunological parameters of seasonal allergic rhinitis (SAR) in an out-of-season single nasal allergen challenge.

Methods

In a study registered at ClinicalTrials.Gov (NCT01123252), a 16-week dietary intervention was undertaken in 60 patients with allergic rhinitis (>16 years old). Using a double-blinded, placebo-controlled anonymised design, the patients were divided equally into two groups. One group was given a dairy drink containing Lactobacillus casei Shirota to ingest daily while the other consumed a similar drink without bacteria. Participants attended the clinic on two consecutive days before the intervention and then again at the end of the study period. On the first day of each 2-day visit, following clinical examination, assessments were made of total nasal symptoms scores and peak nasal inspiratory flow. Nasal scrapings, nasal lavage and blood were collected for laboratory analyses of cellular phenotypes, soluble mediator release and in vitro responses to pollen allergen. These procedures were repeated 24 hours following nasal allergen challenge.

Results

Prior to and following intervention there were no detectable differences between study groups in measured clinical outcome. After intervention, there were differences between groups in their percentages of CD86+ epithelial cells (p = 0.0148), CD86+CD252+ non-epithelial cells (p = 0.0347), sIL-1RII release (p = 0.0289) and IL-1β (p = 0.0224) levels at the nasal mucosa. Delivery of probiotic also suppressed production of sCD23 (p = 0.0081), TGF-β (p = 0.0283) and induced increased production of IFN-γ (p = 0.0351) in supernatants of cultured peripheral blood.

Conclusions & Clinical Relevance

This study did not show significant probiotic-associated changes with respect to the primary clinical endpoint. An absence of overt clinical benefit may be due to an inability of single nasal challenges to accurately represent natural allergen exposure. Nevertheless, oral delivery of probiotics produced changes of the immunological microenvironment at the nasal mucosa in individuals affected by SAR.

Trial Registration

ClinicalTrials.Gov NCT01123252

Hydrolysates of glycated and heat-treated peanut 7S globulin (Ara h 1) modulate human gut microbial proliferation, survival and adhesion

AIMS

Evaluation of an effect of glycation of Ara h 1 on proliferation and survival rate and adhesion of intestinal Enterococcus faecalis, Escherichia coli and Lactobacillus acidophilus.

METHODS AND RESULTS

Pure Ara h 1 heated at three different temperature conditions (G37, G60 and C145°C) in the presence or absence of glucose was subjected to enzymatic hydrolysis. Impacts of Ara h 1 hydrolysates on the bacterial proliferation, survival rate and adhesion to Caco-2 cells in mono and heterogeneous cultures were studied with fluorescent techniques: DAPI, LIVE/DEAD staining and FISH. Examined hydrolysates hindered proliferation of E. coli and Ent. faecalis with simultaneous decrease in their survival. Maillard reaction (MR, glycation) of Ara h 1 did not alter the effect of hydrolysates on bacterial proliferation rate. Hydrolysates modified at 60 and 145°C with glucose altered the profile of immobilized bacteria, mostly by lowering the number of adhering E. coli and promoting the adhesion of bacteria from genera Lactobacillus and Enterococcus.

CONCLUSIONS

Ara h1 hydrolysates processed in various ways demonstrated their strong modulatory effect on bacterial proliferation, survival rate and adhesion.

SIGNIFICANCE AND IMPACT OF THE STUDY

Reducing the adhesion of opportunistic bacteria by hydrolysates of Ara h 1 glycated at 60 and 145°C, together with modulation of immobilization of beneficial lactobacilli and enterococci, may be of relevance in terms of the physiological status of the intestinal barrier.

Overview of evidence in prevention and aetiology of food allergy: a review of systematic reviews

The worldwide prevalence of food allergy appears to be increasing. Early life environmental factors are implicated in the aetiology of this global epidemic. The largest burden of disease is in early childhood, where research efforts aimed at prevention have been focused. Evidence synthesis from good quality systematic reviews is needed. We performed an overview of systematic reviews concerning the prevention and aetiology of food allergy, retrieving 14 systematic reviews, which covered three broad topics: formula (hydrolysed or soy) for the prevention of food allergy or food sensitization; maternal and infant diet and dietary supplements for the prevention of food allergy or food sensitization and hygiene hypothesis-related interventions. Using the AMSTAR criteria for assessment of methodological quality, we found five reviews to be of high quality, seven of medium quality and two of low quality. Overall we found no compelling evidence that any of the interventions that had been systematically reviewed were related to the risk of food allergy. Updating of existing reviews, and production of new systematic reviews, are needed in areas where evidence is emerging for interventions and environmental associations. Furthermore, additional primary studies, with greater numbers of participants and objective food allergy definitions are urgently required.

Disrupted tight junctions in the small intestine of cystic fibrosis mice

The tight junction (TJ) is the major determinant of paracellular permeability, which in the gut protects the body from entry of harmful substances such as microbial components. In cystic fibrosis (CF), there is increased permeability of the small intestine both in humans and in CF mice. To gain insight into the mechanisms of increased intestinal permeability in CF, I analyze the composition of the TJ in a cystic fibrosis transmembrane conductance regulator (Cftr) knockout mouse model. Significant changes in TJ gene expression in the CF intestine were found for Cldn1, Cldn7, Cldn8 and Pmp22, which were expressed at lower levels and Cldn2 that was expressed at a higher level. Protein levels of claudin-2 were increased in the CF intestine as compared to wild-type, while other TJ proteins were not significantly different. In the villus epithelium of the CF intestine, all TJ components analyzed were mislocalized to the basal cytoplasm and showed varying degrees of loss from the TJ and apico-lateral surfaces. The pore-forming claudin-2 in the CF intestine showed more intense staining but was correctly localized to the TJ, principally in the crypts that are enlarged in CF. The cytokine TNFα, known to affect TJ, was elevated to 160% of wild-type in the CF intestine. In summary, there is a dramatic redistribution of claudin proteins from the TJ/lateral membrane to the basal cytoplasm of the villus epithelium in the CF intestine. These changes in TJ protein localization in CF are likely to be involved in the increased permeability of the CF small intestine to macromolecules and TNFα may be a causative factor.

Effect of salmon consumption during pregnancy on maternal and infant faecal microbiota, secretory IgA and calprotectin

The gut microbiota plays an important role in the development of the immune and gastrointestinal systems of infants. In the present study, we investigated whether increased salmon consumption during pregnancy, maternal weight gain during pregnancy or mode of infant feeding alter the markers of gut immune defence and inflammation. Women (n 123) who rarely ate oily fish were randomly assigned to continue consuming their habitual diet or to consume two 150 g portions of farmed salmon per week from 20 weeks of pregnancy to delivery. Faecal samples were collected from the mothers (n 75) at 38 weeks of gestation and from their infants (n 38) on days 7, 14, 28 and 84 post-partum. Fluorescence in situ hybridisation was used to determine faecal microbiota composition and ELISA to measure faecal secretory IgA (sIgA) and calprotectin concentrations. There was no effect of salmon consumption on maternal faecal microbiota or on maternal or infant faecal sIgA and calprotectin concentrations. The degree of weight gain influenced maternal faecal microbiota, and the mode of infant feeding influenced infant faecal microbiota. Faecal samples collected from infants in the salmon group tended to have lower bacterial counts of the Atopobium cluster compared with those collected from infants in the control group (P=0·097). This difference was significant in the formula-fed infants (P< 0·05), but not in the exclusively breast-fed infants. In conclusion, the impact of oily fish consumption during pregnancy on maternal and infant gut microbiota composition is limited, but significant differences are associated with maternal weight gain during pregnancy and mode of infant feeding.

Probiotic administration in early life, atopy, and asthma: a meta-analysis of clinical trials

BACKGROUND AND OBJECTIVE

Probiotics may reduce the risk of atopy and asthma in children. However, results from clinical trials have been conflicting, and several of them may have been underpowered. We performed a meta-analysis of randomized, placebo-controlled trials to assess the effects of probiotic supplementation on atopic sensitization and asthma/wheeze prevention in children.

METHODS

Random-effects models were used to calculate pooled risk estimates. Meta-regression was conducted to examine the effect of potential factors on probiotics efficacy.

RESULTS

Probiotics were effective in reducing total immunoglobulin E (IgE) (mean reduction: -7.59 U/mL [95% confidence interval (CI): -14.96 to -0.22]; P = .044). Meta-regression showed that the reduction in IgE was more pronounced with longer follow-up. Probiotics significantly reduced the risk of atopic sensitization when administered prenatally (relative risk: 0.88 [95% CI: 0.78 to 0.99]; P = .035 for positive result on the skin prick test and/or elevated specific IgE to common allergens) and postnatally (relative risk: 0.86 [95% CI: 0.75 to 0.98]; P = .027 for positive result on skin prick test). Administration of Lactobacillus acidophilus, compared with other strains, was associated with an increased risk of atopic sensitization (P = .002). Probiotics did not significantly reduce asthma/wheeze (relative risk: 0.96 [95% CI: 0.85 to 1.07]).

CONCLUSIONS

Prenatal and/or early-life probiotic administration reduces the risk of atopic sensitization and decreases the total IgE level in children but may not reduce the risk of asthma/wheeze. Follow-up duration and strain significantly modified these effects. Future trials for asthma prevention should carefully select probiotic strain and consider longer follow-up.

Stress and food allergy: mechanistic considerations

Recent years have seen a marked increase in food allergy prevalence among children, particularly in Western countries, that cannot be explained by genetic factors alone. This has resulted in an increased effort to identify environmental risk factors underlying food allergies and to understand how these factors may be modified through interventions. Food allergy is an immune-mediated adverse reaction to food. Consequently, considerations of candidate risk factors have begun to focus on environmental influences that perturb the healthy development of the emerging immune system during critical periods of development (eg, prenatally and during early childhood), particularly in the gut. Given that psychosocial stress is known to play an important role in other allergic and inflammatory diseases, such as asthma, its potential role in food allergy is a growing area of research. However, research to date has largely focused on animal studies. This review synthesizes relevant animal research and epidemiological data, providing proof of concept for moderating influences of psychological stress on food allergy outcomes in humans. Pathways that may underlie associations between psychosocial stress and the expression of food allergy are discussed.

Establishment of the intestinal microbiota and its role for atopic dermatitis in early childhood

BACKGROUND

Perturbations in the intestinal microbiota may disrupt mechanisms involved in the development of immunologic tolerance. The present study aimed to examine the establishment of the infant microbiota and its association to the development of atopic dermatitis (AD).

METHODS

Within a randomized, placebo-controlled trial on the prevention of AD by oral supplementation of a bacterial lysate between week 5 and the end of month 7, feces was collected at the ages of 5 weeks (n = 571), 13 weeks (n = 332), and 31 weeks (n = 499) and subjected to quantitative PCRs to detect bifidobacteria, bacteroides, lactobacilli, Escherichia coli, Clostridium difficile, and Clostridium cluster I.

RESULTS

Birth mode, breast-feeding but also birth order had a strong effect on the microbiota composition. With increasing number of older siblings the colonization rates at age 5 weeks of lactobacilli (P < .001) and bacteroides (P = .02) increased, whereas rates of clostridia decreased (P < .001). Colonization with clostridia, at the age of 5 and 13 weeks was also associated with an increased risk of developing AD in the subsequent 6 months of life (odds ratioadjusted = 2.35; 95% CI, 1.36-3.94 and 2.51; 1.30-4.86, respectively). Mediation analyses demonstrated that there was a statistically significant indirect effect via Clostridium cluster I colonization for both birth mode and birth order in association to AD.

CONCLUSION

The results of this study are supportive for a role of the microbiota in the development of AD. Moreover, the "beneficial" influence of older siblings on the microbiota composition suggests that this microbiota may be one of the biological mechanisms underlying the sibling effect.