The Influence of the Microbiome on Allergic Sensitization to Food

Cross-domain microbiomes: the interaction of gut, lung and environmental microbiota in asthma pathogenesis

Recent experimental and epidemiological studies underscore the vital interaction between the intestinal microbiota and the lungs, an interplay known as the "gut-lung axis". The significance of this axis has been further illuminated following the identification of intestinal microbial metabolites, such as short-chain fatty acids (SCFA), as key mediators in setting the tone of the immune system. Through the gut-lung axis, the gut microbiota and its metabolites, or allergens, are directly or indirectly involved in the immunomodulation of pulmonary diseases, thereby increasing susceptibility to allergic airway diseases such as asthma. Asthma is a complex outcome of the interplay between environmental factors and genetic predispositions. The concept of the gut-lung axis may offer new targets for the prevention and treatment of asthma. This review outlines the relationships between asthma and the respiratory microbiome, gut microbiome, and environmental microbiome. It also discusses the current advancements and applications of microbiomics, offering novel perspectives and strategies for the clinical management of chronic respiratory diseases like asthma.

Gut Microbiome-Serum Metabolism Revealed the Allergenicity of Ferulic Acid Combined with Glucose-Modified β-Lactoglobulin

A novel strategy combining ferulic acid and glucose was proposed to reduce β-lactoglobulin (BLG) allergenicity and investigate whether the reduction in allergenicity was associated with gut microbiome and serum metabolism. As a result, the multistructure of BLG changed, and the modified BLG decreased significantly the contents of IgE, IgG, IgG1, and mMCP-1 in serum, improved the diversity and structural composition of gut microbiota, and increased the content of short-chain fatty acids (SCFAs) in allergic mice. Meanwhile, allergic mice induced by BLG affected arachidonic acid, tryptophan, and other metabolic pathways in serum, the modified BLG inhibited the production of metabolites in arachidonic acid metabolism pathway and significantly increased tryptophan metabolites, and this contribution helps in reducing BLG allergenicity. Overall, reduced allergenicity of BLG after ferulic acid was combined with glucose modification by regulating gut microbiota, the metabolic pathways of arachidonic acid and tryptophan. The results may offer new thoughts alleviating the allergy risk of allergenic proteins.

Notch Signaling Inhibition Alleviates Allergies Caused by Antarctic Krill Tropomyosin through Improving Th1/Th2 Imbalance and Modulating Gut Microbiota

Antarctic krill tropomyosin (AkTM) has been shown in mice to cause IgE-mediated food allergy. The objective of this work was to investigate the role of Notch signaling in AkTM-sensitized mice, as well as to determine the changes in gut microbiota composition and short-chain fatty acids (SCFAs) in the allergic mice. An AkTM-induced food allergy mouse model was built and N-[N-(3,5-difluorophenacetyl)-L-alanyl]-S-phenylglycine t-butyl ester (DAPT) was used as an γ-secretase inhibitor to inhibit the activation of Notch signaling. Food allergy indices, some key transcription factors, histologic alterations in the small intestine, and changes in gut microbiota composition were examined. The results showed that DAPT inhibited Notch signaling, which reduced AkTM-specific IgE, suppressed mast cell degranulation, decreased IL-4 but increased IFN-γ production, and alleviated allergic symptoms. Quantitative real-time PCR and Western blotting analyses revealed that expressions of Hes-1, Gata3, and IL-4 were down-regulated after DAPT treatment, accompanied by increases in T-bet and IFN-γ, indicating that Notch signaling was active in AkTM-sensitized mice and blocking it could reverse the Th1/Th2 imbalance. Expressions of key transcription factors revealed that Notch signaling could promote Th2 cell differentiation in sensitized mice. Furthermore, 16S rRNA sequencing results revealed that AkTM could alter the diversity and composition of gut microbiota in mice, leading to increases in inflammation-inducing bacteria such as Enterococcus and Escherichia-Shigella. Correlation analysis indicated that reduced SCFA concentrations in AkTM-allergic mice may be related to decreases in certain SCFA-producing bacteria, such as Clostridia_UCG-014. The changes in gut microbiota and SCFAs could be partially restored by DAPT treatment. Our findings showed that inhibiting Notch signaling could alleviate AkTM-induced food allergy by correcting Th1/Th2 imbalance and modulating the gut microbiota.

Lupus susceptibility gene Pbx1 controls the development, stability, and function of regulatory T cells via Rtkn2 expression

The maintenance of regulatory T (Treg) cells critically prevents autoimmunity. Pre-B cell leukemia transcription factor 1 (Pbx1) variants are associated with lupus susceptibility, particularly through the expression of a dominant negative isoform Pbx1-d in CD4+ T cells. Pbx1-d overexpression impaired Treg cell homeostasis and promoted inflammatory CD4+ T cells. Here, we showed a high expression of Pbx1 in human and murine Treg cells, which is decreased in lupus patients and mice. Pbx1 deficiency or Pbx1-d overexpression reduced the number, stability, and suppressive activity of Treg cells, which increased murine responses to immunization and autoimmune induction. Mechanistically, Pbx1 deficiency altered the expression of genes implicated in cell cycle and apoptosis in Treg cells. Intriguingly, Rtkn2, a Rho-GTPase previously associated with Treg homeostasis, was directly transactivated by Pbx1. Our results suggest that the maintenance of Treg cell homeostasis and stability by Pbx1 through cell cycle progression prevent the expansion of inflammatory T cells that otherwise exacerbates lupus progression in the hosts.

Keratinocyte-derived small extracellular vesicles supply antigens for CD1a-resticted T cells and promote their type 2 bias in the context of filaggrin insufficiency

Introduction

Exosome-enriched small extracellular vesicles (sEVs) are nanosized organelles known to participate in long distance communication between cells, including in the skin. Atopic dermatitis (AD) is a chronic inflammatory skin disease for which filaggrin (FLG) gene mutations are the strongest genetic risk factor. Filaggrin insufficiency affects multiple cellular function, but it is unclear if sEV-mediated cellular communication originating from the affected keratinocytes is also altered, and if this influences peptide and lipid antigen presentation to T cells in the skin.

Methods

Available mRNA and protein expression datasets from filaggrin-insufficient keratinocytes (shFLG), organotypic models and AD skin were used for gene ontology analysis with FunRich tool. sEVs secreted by shFLG and control shC cells were isolated from conditioned media by differential centrifugation. Mass spectrometry was carried out for lipidomic and proteomic profiling of the cells and sEVs. T cell responses to protein, peptide, CD1a lipid antigens, as well as phospholipase A2-digested or intact sEVs were measured by ELISpot and ELISA.

Results

Data analysis revealed extensive remodeling of the sEV compartment in filaggrin insufficient keratinocytes, 3D models and the AD skin. Lipidomic profiles of shFLGsEV showed a reduction in the long chain (LCFAs) and polyunsaturated fatty acids (PUFAs; permissive CD1a ligands) and increased content of the bulky headgroup sphingolipids (non-permissive ligands). This resulted in a reduction of CD1a-mediated interferon-γ T cell responses to the lipids liberated from shFLG-generated sEVs in comparison to those induced by sEVs from control cells, and an increase in interleukin 13 secretion. The altered sEV lipidome reflected a generalized alteration in the cellular lipidome in filaggrin-insufficient cells and the skin of AD patients, resulting from a downregulation of key enzymes implicated in fatty acid elongation and desaturation, i.e., enzymes of the ACSL, ELOVL and FADS family.

Discussion

We determined that sEVs constitute a source of antigens suitable for CD1a-mediated presentation to T cells. Lipids enclosed within the sEVs secreted on the background of filaggrin insufficiency contribute to allergic inflammation by reducing type 1 responses and inducing a type 2 bias from CD1a-restricted T cells, thus likely perpetuating allergic inflammation in the skin.

Understanding food allergy through neuroimmune interactions in the gastrointestinal tract

Food allergies are adverse immune reactions to food proteins in the absence of oral tolerance, and the incidence of allergies to food, including peanut, cow's milk, and shellfish, has been increasing globally. Although advancements have been made toward understanding the contributions of the type 2 immune response to allergic sensitization, crosstalk between these immune cells and neurons of the enteric nervous system is an area of emerging interest in the pathophysiology of food allergy, given the close proximity of neuronal cells of the enteric nervous system and type 2 effector cells, including eosinophils and mast cells. At mucosal sites, such as the gastrointestinal tract, neuroimmune interactions contribute to the sensing and response to danger signals from the epithelial barrier. This communication is bidirectional, as immune cells express receptors for neuropeptides and transmitters, and neurons express cytokine receptors, allowing for the detection of and response to inflammatory insults. In addition, it seems that neuromodulation of immune cells including mast cells, eosinophils, and innate lymphoid cells is critical for amplification of the type 2 allergic immune response. As such, neuroimmune interactions may be critical targets for future food allergy therapies. This review evaluates the contributions of local enteric neuroimmune interactions to the underlying immune response in food allergy and discusses considerations for future investigations into targeting neuroimmune pathways for treatment of food allergies.

Akkermansia muciniphila exacerbates food allergy in fibre-deprived mice

Alterations in the gut microbiome, including diet-driven changes, are linked to the rising prevalence of food allergy. However, little is known about how specific gut bacteria trigger the breakdown of oral tolerance. Here we show that depriving specific-pathogen-free mice of dietary fibre leads to a gut microbiota signature with increases in the mucin-degrading bacterium Akkermansia muciniphila. This signature is associated with intestinal barrier dysfunction, increased expression of type 1 and 2 cytokines and IgE-coated commensals in the colon, which result in an exacerbated allergic reaction to food allergens, ovalbumin and peanut. To demonstrate the causal role of A. muciniphila, we employed a tractable synthetic human gut microbiota in gnotobiotic mice. The presence of A. muciniphila within the microbiota, combined with fibre deprivation, resulted in stronger anti-commensal IgE coating and innate type-2 immune responses, which worsened symptoms of food allergy. Our study provides important insights into how gut microbes can regulate immune pathways of food allergy in a diet-dependent manner.

Bifidobacteria modulate immune response in pediatric patients with cow's milk protein allergy

BACKGROUND

In children with an allergy to cow's milk proteins (CMA), the altered composition of intestinal microbiota influences the immune tolerance to milk proteins (CMP). This study aims to investigate the effect of probiotics on the phenotype and activation status of peripheral basophils and lymphocytes in a pediatric CMA cohort.

METHODS

CMA children underwent 45 days of treatment with Bifidobacteria. The basophil degranulation and the immune phenotype of B cells, T helper cells, and regulatory T cells were analyzed in peripheral blood at diagnosis (T0), after a 45-day probiotic treatment (T1), and 45 days after the probiotic wash-out (T2).

RESULTS

We observed in probiotic-treated CMA patients a decrease in naive T lymphocytes. Among the CD3+ cell subsets, both naive and activated CD4+ cells resulted markedly reduced after taking probiotics, with the lowest percentages at T2. A decreased basophil degranulation was observed in response to all analyzed CMP at T1 compared to T0.

CONCLUSIONS

The probiotic treatment resulted in a decrease of circulating naive and activated CD4+ T cells, as well as degranulating basophils. These data suggest that the Bifidobacteria could have a beneficial effect in the modulation of oral tolerance to CMP.

TRIAL REGISTRATION

ISRCTN69069358. URL of registration: https://www.isrctn.com/ISRCTN69069358 .

IMPACT

Probiotic treatment with Bifidobacteria induces a reduction of both naive and activated circulating CD4+ T cells in pediatric patients with cow's milk allergy (CMA). The probiotic supplementation induces a decreased basophil degranulation. The immunological tolerance persists even after 45 days of the probiotic wash-out. Bifidobacteria in vivo supplementation down-modulates the activation of innate and adaptive immunity in pediatric patients with cow's milk allergy. Bifidobacteria contribute to the development of immune tolerance in CMA patients.

Impact of local human microbiota on the allergic diseases: Organ-organ interaction

The homogeneous impact of local dysbiosis on the development of allergic diseases in the same organ has been thoroughly studied. However, much less is known about the heterogeneous influence of dysbiosis within one organ on allergic diseases in other organs. A comprehensive analysis of the current scientific literature revealed that most of the relevant publications focus on only three organs: gut, airways, and skin. Moreover, the interactions appear to be mainly unidirectional, that is, dysbiotic conditions of the gut being associated with allergic diseases of the airways and the skin. Similar to homogeneous interactions, early life appears to be not only a crucial period for the formation of the microbiota in one organ but also for the later development of allergic diseases in other organs. In particular, we were able to identify a number of specific bacterial and fungal species/genera in the intestine that were repeatedly associated in the literature with either increased or decreased allergic diseases of the skin, like atopic dermatitis, or the airways, like allergic rhinitis and asthma. The reported studies indicate that in addition to the composition of the microbiome, also the relative abundance of certain microbial species and the overall diversity are associated with allergic diseases of the corresponding organs. As anticipated for human association studies, the underlying mechanisms of the organ-organ crosstalk could not be clearly resolved yet. Thus, further work, in particular experimental animal studies are required to elucidate the mechanisms linking dysbiotic conditions of one organ to allergic diseases in other organs.

Human Gut Microbiota Plasticity throughout the Life Course

The role of the gut microbiota in human health and disease has garnered heightened attention over the past decade. A thorough understanding of microbial variation over the life course and possible ways to influence and optimize the microbial pattern is essential to capitalize on the microbiota's potential to influence human health. Here, we review our current understanding of the concept of plasticity of the human gut microbiota throughout the life course. Characterization of the plasticity of the microbiota has emerged through recent research and suggests that the plasticity in the microbiota signature is largest at birth when the microbial colonization of the gut is initiated and mode of birth imprints its mark, then decreases postnatally continuously and becomes less malleable and largely stabilized with advancing age. This continuing loss of plasticity has important implication for the impact of the exposome on the microbiota and health throughout the life course and the identification of susceptible 'windows of opportunity' and methods for interventions.

Effect of early postnatal supplementation of newborns with probiotic strain E. coli O83:K24:H31 on allergy incidence, dendritic cells, and microbiota

Introduction

Probiotic administration seems to be a rational approach to promote maturation of the neonatal immune system. Mutual interaction of the microbiota with the host immune system is critical for the setting of appropriate immune responses including a tolerogenic one and thevmaintenance of homeostasis. On the other hand, our knowledge on the modes of actions of probiotics is still scarce.

Methods

In our study, probiotic strain Escherichia coli O83:K24:H31 (EcO83) was administered to neonates of allergic mothers (AMs; neonates with increased risk for allergy development) within 48 h after the delivery, and the impact of this early postnatal supplementation on allergy incidence and selected immune markers has been analyzed 10 years after the primary EcO83 administration.

Results

We have observed decreased allergy incidence in 10-year-old children supplemented with EcO83 (13 of 52 children were allergic) in comparison with non-supplemented children of AMs (16 of 42 children were allergic). The early postnatal EcO83 supplementation appeared to limit the allergy in the high-risk group (children of AMs) compared to that in the low-risk group (children of healthy mothers). Dendritic cells (DCs) in the peripheral blood of EcO83-supplemented children do not differ significantly in cell surface presence of CD83. The immunomodulatory capacity of EcO83 on DCs was tested in vitro as well. Both directly isolated myeloid and in vitro monocyte-derived DCs from cord blood increased CD83 expression together with interleukin (IL)-10 secretion after EcO83 stimulation. The effect of early postnatal EcO83 supplementation on the microbiota composition of 10-year-old children was characterized by next-generation sequencing, and we have not observed significant changes in the microbiota composition of EcO83-supplemented and non-supplemented children at the age of 10 years.

Conclusions

Early postnatal EcO83 supplementation appears to lower allergy incidence in children of AMs. It seems that the beneficial effect of EcO83 is mediated via modulation of DC functional capacities without impacting the microbiota composition. Larger-scale studies will be necessary to confirm these preliminary findings.

Manipulating the microbiome to enhance oral tolerance in food allergy

Loss of oral tolerance (OT) to food antigens results in food allergies. One component of achieving OT is the symbiotic microorganisms living in the gut (microbiota). The composition of the microbiota can drive either pro-tolerogenic or pro-inflammatory responses against dietary antigens though interactions with the local immune cells within the gut. Products from bacterial fermentation, such as butyrate, are one of the main communication molecules involved in this interaction, however, this is released by a subset of bacterial species. Thus, strategies to specifically expand these bacteria with protolerogenic properties have been explored to complement oral immunotherapy in food allergy. These approaches either provide digestible biomolecules to induce beneficial bacteria species (prebiotics) or the direct administration of live bacteria species (probiotics). While this combined therapy has shown positive outcomes in clinical trials for cow's milk allergy, more research is needed to determine if this therapy can be extended to other food allergens.

Multi-Omic Profiles in Infants at Risk for Food Reactions

Food reactions (FR) are multifactorial and impacted by medical, demographic, environmental, and immunologic factors. We hypothesized that multi-omic analyses of host-microbial factors in saliva would enhance our understanding of FR development. This longitudinal cohort study included 164 infants followed from birth through two years. The infants were identified as FR (n = 34) or non-FR (n = 130) using the Infant Feeding Practice II survey and medical record confirmation. Saliva was collected at six months for the multi-omic assessment of cytokines, mRNAs, microRNAs, and the microbiome/virome. The levels of one miRNA (miR-203b-3p, adj. p = 0.043, V = 2913) and one viral phage (Proteus virus PM135, adj. p = 0.027, V = 2955) were lower among infants that developed FRs. The levels of one bacterial phylum (Cyanobacteria, adj. p = 0.048, V = 1515) were higher among infants that developed FR. Logistical regression models revealed that the addition of multi-omic features (miR-203b-3p, Cyanobacteria, and Proteus virus PM135) improved predictiveness for future FRs in infants (p = 0.005, X2 = 12.9), predicting FRs with 72% accuracy (AUC = 0.81, sensitivity = 72%, specificity = 72%). The multi-omic analysis of saliva may enhance the accurate identification of infants at risk of FRs and provide insights into the host/microbiome interactions that predispose certain infants to FRs.

Postnatal probiotic supplementation can prevent and optimize treatment of childhood asthma and atopic disorders: A systematic review of randomized controlled trials

Background

Although several randomized controlled trials (RCTs) published over the past 5 years show that prenatal or postnatal probiotics may prevent or optimize the treatment of childhood asthma and atopic disorders, findings from the systematic reviews and meta-analyses of these studies appear inconsistent. More recent RCTs have focused on postnatal probiotics, and linked specific probiotic strains to better disease outcomes.

Objective

This systematic review aimed to determine if postnatal probiotics are as effective as prenatal probiotics in preventing or treating childhood asthma and atopic disorders.

Methods

We searched the PubMed, Medline, Google Scholar, and EMBASE databases for RCTs published within the past 5 years (from 2017 to 2022). We included only full-text RCTs on human subjects published in or translated into the English language. We retrieved relevant data items with a preconceived data-extraction form and assessed the methodological quality of the selected RCTs using the Cochrane Collaboration's tool for assessing the risk of bias in randomized trials. We qualitatively synthesized the retrieved data to determine any significant differences in study endpoints of the probiotic and placebo groups.

Results

A total of 1,320 participants (688 and 632 in the probiotic and placebo groups) from six RCTs were investigated. One RCT showed that early Lactobacillus rhamnosus GG (LGG) led to a reduction in the cumulative incidence rate of asthma. Another study demonstrated that mixed strains of Lactobacillus paracasei and Lactobacillus fermentum could support clinical improvement in children with asthma while one trial reported a significant reduction in the frequency of asthma exacerbations using a mixture of Ligilactobacillus salivarius and Bifidobacterium breve. Three trials showed that a combination of LGG and Bifidobacterium animalis subsp lactis, Lactobacillus rhamnosus alone, and a probiotic mixture of Lactobacillus ŁOCK strains improved clinical outcomes in children with atopic dermatitis and cow-milk protein allergy.

Conclusions

Postnatal strain-specific probiotics (in single or mixed forms) are beneficial in preventing and treating atopic dermatitis and other allergies. Similarly, specific strains are more effective in preventing asthma or improving asthma outcomes. We recommend more interventional studies to establish the most useful probiotic strain in these allergic diseases.

Insights into Microbiome and Metabolic Signatures of Children Undergoing Peanut Oral Immunotherapy

Background: Peanut oral immunotherapy has emerged as a novel, active management approach for peanut-allergic sufferers, but limited data exist currently on the role of the microbiome in successful desensitization. Objective: We examined the oral and gut microbiome in a cohort of 17 children undergoing peanut oral immunotherapy with the aim to identify the microbiome signatures associated with successful desensitization. We also set out to characterize their fecal metabolic profiles after successful therapy. Methods: Participants gradually built up their daily dose from 2 mg (starting dose) to 300 mg (maintenance dose) within approximately 40 weeks. We collected a buccal and stool specimen from each subject at two different time points: at baseline and post-therapy (1 month after reaching maintenance). The oral (buccal) and gut (fecal) microbiome was characterized based on sequencing of 16S rRNA gene amplicons with Illumina MiSeq. Fecal short chain fatty acid levels were measured using liquid chromatography-tandem mass spectrometry. Results: We report increased alpha diversity of the oral microbiome post-therapy and have also identified a significant increase in the relative abundance of oral Actinobacteria, associated with the desensitized state. However, the baseline gut microbiome did not differ from the post-therapy. Additionally, fecal short chain fatty acids increased after therapy, but not significantly. Conclusion: Our research adds to the limited current knowledge on microbiome and metabolic signatures in pediatric patients completing oral immunotherapy. Post-therapy increased trends of fecal fatty acid levels support a role in modulating the allergic response and potentially exerting protective and anti-inflammatory effects alongside successful desensitization. A better understanding of the microbiome-related mechanisms underlying desensitization may allow development of smarter therapeutic approaches in the near future. Clinical implication: The oral microbiome composition is altered following successful peanut oral immunotherapy, with a significant increase in alpha diversity and the relative abundance of phylum Actinobacteria. Capsule summary: Significant microbiome changes in children completing peanut immunotherapy include increase in alpha-diversity and overrepresentation of Actinobacteria in the oral microbiome, and increased trends for fecal short chain fatty acids, suggesting a protective effect against the allergic response.

Proinflammatory mucosal-associated invariant CD8+ T cells react to gut flora yeasts and infiltrate multiple sclerosis brain

The composition of the intestinal microbiota plays a critical role in shaping the immune system. Modern lifestyle, the inappropriate use of antibiotics, and exposure to pollution have significantly affected the composition of commensal microorganisms. The intestinal microbiota has been shown to sustain inappropriate autoimmune responses at distant sites in animal models of disease, and may also have a role in immune-mediated central nervous system (CNS) diseases such as multiple sclerosis (MS). We studied the composition of the gut mycobiota in fecal samples from 27 persons with MS (pwMS) and in 18 healthy donors (HD), including 5 pairs of homozygous twins discordant for MS. We found a tendency towards higher fungal abundance and richness in the MS group, and we observed that MS twins showed a higher rate of food-associated strains, such as Saccharomyces cerevisiae. We then found that in pwMS, a distinct population of cells with antibacterial and antifungal activity is expanded during the remitting phase and markedly decreases during clinically and/or radiologically active disease. These cells, named MAIT (mucosal-associated invariant T cells) lymphocytes, were significantly more activated in pwMS compared to HD in response to S. cerevisiae and Candida albicans strains isolated from fecal samples. This activation was also mediated by fungal-induced IL-23 secretion by innate immune cells. Finally, immunofluorescent stainings of MS post-mortem brain tissues from persons with the secondary progressive form of the disease showed that MAIT cells cross the blood–brain barrier (BBB) and produce pro-inflammatory cytokines in the brain. These results were in agreement with the hypothesis that dysbiosis of the gut microbiota might determine the inappropriate response of a subset of pathogenic mucosal T cells and favor the development of systemic inflammatory and autoimmune diseases.

Immunotherapies in the treatment of immunoglobulin E‑mediated allergy: Challenges and scope for innovation (Review)

Immunoglobulin E (IgE)‑mediated allergy or hypersensitivity reactions are generally defined as an unwanted severe symptomatic immunological reaction that occurs due to shattered or untrained peripheral tolerance of the immune system. Allergen‑specific immunotherapy (AIT) is the only therapeutic strategy that can provide a longer‑lasting symptomatic and clinical break from medications in IgE‑mediated allergy. Immunotherapies against allergic diseases comprise a successive increasing dose of allergen, which helps in developing the immune tolerance against the allergen. AITs exerttheirspecial effectiveness directly or indirectly by modulating the regulator and effector components of the immune system. The number of success stories of AIT is still limited and it canoccasionallyhave a severe treatment‑associated adverse effect on patients. Therefore, the formulation used for AIT should be appropriate and effective. The present review describes the chronological evolution of AIT, and provides a comparative account of the merits and demerits of different AITs by keeping in focus the critical guiding factors, such as sustained allergen tolerance, duration of AIT, probability of mild to severe allergic reactions and dose of allergen required to effectuate an effective AIT. The mechanisms by which regulatory T cells suppress allergen‑specific effector T cells and how loss of natural tolerance against innocuous proteins induces allergy are reviewed. The present review highlights the major AIT bottlenecks and the importantregulatory requirements for standardized AIT formulations. Furthermore, the present reviewcalls attention to the problem of 'polyallergy', which is still a major challenge for AIT and the emerging concept of 'component‑resolved diagnosis' (CRD) to address the issue. Finally, a prospective strategy for upgrading CRD to the next dimension is provided, and a potential technology for delivering thoroughly standardized AIT with minimal risk is discussed.

Effects of delivery mode and labor duration on the development of food sensitization in infancy

BACKGROUND

The effects of delivery mode and labor duration on the development of food sensitization (FS) in infancy remain unclear.

OBJECTIVE

To elucidate the potential effects of delivery mode and labor duration on FS development by 6 months of age.

METHODS

Using data from a randomized controlled trial of a birth cohort from 4 Japanese hospitals that assessed cow's milk allergy development by 6 months of age, we performed a nested case-control trial of 462 participants who had undergone the final assessment at 6 months of age. FS was defined as positive skin prick test reactions to hen's egg, cow's milk, wheat, or soy. For the primary outcome, we calculated the adjusted odds ratio of vaginal delivery (VD) relative to cesarean delivery for FS development by 6 months of age using a multivariable logistic regression analysis. For the secondary outcome, we compared labor durations between participants with and without FS using the Mann-Whitney U test.

RESULTS

The adjusted odds ratio of VD for FS development was 2.54 (95% confidence interval, 1.32-4.87; P = .005). The median labor duration was significantly longer in participants with FS (5.7 hours, interquartile range, 2.7-10.1) than in participants without FS (4.5 hours, 1.1-8.2) (P = .01).

CONCLUSION

VD was considerably associated with an increased risk of FS in infancy, and longer labor durations may promote FS development.

Intermittent antibiotic treatment accelerated the development of colitis in IL-10 knockout mice

BACKGROUND AND AIMS

Many epidemiological studies suggest an association between antibiotic exposure and the development of inflammatory bowel disease [IBD]. However, the majority of these studies are observational and still the question remains, "Does the specific antibiotic administration regimen play a role in the development of colitis?" This study aimed to compare the possible effects of continuous and intermittent antibiotic exposure on the development of colitis using a colitis-susceptible IL-10 knockout [IL-10-/-] mouse model.

METHODS

IL-10-/- mice [C57BL/6] were randomly assigned to a non-antibiotic group, continuous antibiotic group and intermittent antibiotic group, and observed for 30 weeks. The antibiotic cocktail was given via the drinking water. The differential response to antibiotics was assessed.

RESULTS

Intermittent antibiotic treatment resulted in severe colitis with early disease onset in IL-10-/- mice. Higher unit colon weight and spleen weight were observed in intermittent antibiotic-treated mice but not in the continuous antibiotic group. Moreover, intermittent antibiotic treatment aggravated epithelial damage and colonic inflammation, mucosal barrier dysfunction and colonic allergic sensitization in IL-10-/- mice, whereas continuous antibiotic treatment ameliorated these symptoms. Male IL-10-/- mice with intermittent antibiotic exposure were more susceptible to colonic inflammation and allergic response than females.

CONCLUSIONS

In summary, intermittent antibiotic exposure accelerated the development of severe colitis more than continuous antibiotic exposure in IL-10-/- male mice. In addition to the colonic damage and impaired barrier function, stimulation of allergic response may play a role in accelerating the development of colitis in genetically susceptible mice.

The First 1000 Days: Assembly of the Neonatal Microbiome and Its Impact on Health Outcomes

Early life microbial colonization is critical for the development of the immune system, postnatal growth, and long-term health and disease. The dynamic and nascent microbiomes of children are highly individualized and are characterized by low bacterial diversity. Any disruptions in microbial colonization can contribute to shifts in normal microbial colonization that persist past the first 1000 days of life and result in intestinal dysbiosis. Here, we focus on microbiome-host interactions during fetal, newborn, and infant microbiome development. We summarize the roles of bacterial communities in fetal development and adverse health outcomes due to dysbiosis. We also discuss how internal and external factors program the microbiome's metabolic machinery as it evolves into an adult-like microbiome. Finally, we discuss the limits of current studies and future directions. Studies on the early-life microbiome will be critical for a better understanding of childhood health and diseases, as well as restorative methods for the prevention and treatment of diseases in adulthood.

Frequency of signs of chronic gastrointestinal disease in dogs after an episode of acute hemorrhagic diarrhea

BACKGROUND

Acute enteropathy is a trigger of chronic gastrointestinal (GI) disease in humans.

OBJECTIVE

To report the prevalence of and explore possible risk factors for signs of chronic GI disease in dogs after an episode of acute hemorrhagic diarrhea (AHD).

ANIMALS

One hundred and fifty-one dogs, 80 dogs with a historical diagnosis of AHD, 71 control dogs with no history of AHD.

METHODS

In this retrospective longitudinal study, data were collected from dogs with a historical diagnosis of AHD and healthy controls matched by breed, age and sex, aged between 1 year and 15 years of age, for which a follow-up of at least 12 months after enrolment was available. Dog owners responded to a questionnaire to determine the history of signs of chronic GI disease.

RESULTS

There was a higher prevalence of signs of chronic GI disease in the dogs with a previous episode of AHD compared to control dogs (AHD 28%; controls 13%; P = .03; odds ratio = 2.57; confidence interval [CI] 95% 1.12-6.31) over a similar observation time (median 4 years; range, 1-12 years).

CONCLUSIONS AND CLINICAL IMPORTANCE

Severe intestinal mucosal damage and associated barrier dysfunction might trigger chronic GI disease later in life.

Behavioral Economics and Ambulatory Antibiotic Stewardship: A Narrative Review

PURPOSE

Behavioral economics recognizes that contextual, psychological, social, and emotional factors powerfully influence decision-making. Behavioral economics has the potential to provide a better understanding of, and, through subtle environmental changes, or "nudges," improve persistent quality-of-care challenges, like ambulatory antibiotic overprescribing. Despite decades of admonitions and educational initiatives, in the United States, up to 50% of ambulatory antibiotic prescriptions remain inappropriate or not associated with a diagnosis.

METHODS

We conducted a Medline search and performed a narrative review that examined the use of behavioral economics to understand the rationale for, and improvement of, ambulatory antibiotic prescribing.

FINDINGS

Clinicians prescribe antibiotics inappropriately because of perceived patient demand, to maintain patient satisfaction, diagnostic uncertainty, or time pressure, among other reasons. Behavioral economics-informed approaches offer additional improvements in antibiotic prescribing beyond clinician education and communication training. Precommitment, in which clinicians publicize their intent to prescribe antibiotics "only when they are absolutely necessary," leverages clinicians' self-conception and a desire to act in a manner consistent with public statements. Precommitment was associated with a 20% absolute reduction in the inappropriate antibiotic prescribing for acute respiratory infections. Justification alerts, in which clinicians must provide a brief written rationale for prescribing antibiotics, leverages social accountability, redefines the status quo as an active choice, and helps clinicians to shift from fast to slow, careful thinking. With justification alerts, the absolute rate of inappropriate antibiotic prescribing decreased from 23% to 5%. Peer comparison, in which clinicians receive feedback comparing their performance to their top-performing peers, provides evidence of improved performance and leverages peoples' desire to conform to social norms. Peer comparison decreased absolute inappropriate antibiotic prescribing rates from 20% to 4%, a decrease that persisted for 12 months after the end of the intervention. Also, a one-time peer-comparison letter from a high-profile messenger to primary care practices with high rates of prescribing antibiotics, there was a 6-month, 3% decrease inantibiotic prescribing. Future directions in applying behavioral economics to the inappropriate antibiotic prescribing include paying careful attention to design details; improving intervention effectiveness and durability; making harms salient; participants' involvement in the development of interventions (the "Ikea effect"); factoring in patient satisfaction; and patient-facing nudges about antibiotic use and care-seeking. In addition, the COVID pandemic could aid in ambulatory antibiotic prescribing improvements due to changing cognitive frames around respiratory symptom evaluation and antibiotic prescribing.

IMPLICATIONS

To improve ambulatory antibiotic prescribing, several behavioral economics-informed approaches-especially precommitment, justification alerts, and peer comparison-have reduced the rates of inappropriate prescribing of antibiotics to low levels.

Viral Inactivation Impacts Microbiome Estimates in a Tissue-Specific Manner

The global emergence of novel pathogenic viruses presents an important challenge for research, as high biosafety levels are required to process samples. While inactivation of infectious agents facilitates the use of less stringent safety conditions, its effect on other biological entities of interest present in the sample is generally unknown. Here, we analyzed the effect of five inactivation methods (heat, ethanol, formaldehyde, psoralen, and TRIzol) on microbiome composition and diversity in samples collected from four different body sites (gut, nasal, oral, and skin) and compared them against untreated samples from the same tissues. We performed 16S rRNA gene sequencing and estimated abundance and diversity of bacterial taxa present in all samples. Nasal and skin samples were the most affected by inactivation, with ethanol and TRIzol inducing the largest changes in composition, and heat, formaldehyde, TRIzol, and psoralen inducing the largest changes in diversity. Oral and stool microbiomes were more robust to inactivation, with no significant changes in diversity and only moderate changes in composition. Firmicutes was the taxonomic group least affected by inactivation, while Bacteroidetes had a notable enrichment in nasal samples and moderate enrichment in fecal and oral samples. Actinobacteria were more notably depleted in fecal and skin samples, and Proteobacteria exhibited a more variable behavior depending on sample type and inactivation method. Overall, our results demonstrate that inactivation methods can alter the microbiome in a tissue-specific manner and that careful consideration should be given to the choice of method based on the sample type under study. IMPORTANCE Understanding how viral infections impact and are modulated by the microbiome is an important problem in basic research but is also of high clinical relevance under the current pandemic. To facilitate the study of interactions between microbial communities and pathogenic viruses under safe conditions, the infectious agent is generally inactivated prior to processing samples. The effect of this inactivation process in the microbiome is, however, unknown. Further, it is unclear whether biases introduced by inactivation methods are dependent on the sample type under study. Estimating the magnitude and nature of the changes induced by different methods in samples collected from various body sites thus provides important information for current and future studies that require inactivation of pathogenic agents.

Potential utility of nano-based treatment approaches to address the risk of Helicobacter pylori

INTRODUCTION

Helicobacter pylori (H. pylori) has occupied a significant place among infectious pathogens and it has been documented as a leading challenge due to its higher resistance to the commonly used drugs, higher adaptability, and lower targeting specificity of the available drugs.

AREAS COVERED

New treatment strategies are urgently needed in order to improve the current advancement in modern medicine. Nanocarriers have gained an advantage of drug encapsulation and high retention time in the stomach with a prolonged drug release rate at the targeted site. This article aims to highlight the recent advances in nanotechnology with special emphasis on metallic, polymeric, lipid, membrane coated, and target-specific nanoparticles (NPs), as well as, natural products for treating H. pylori infection. We discussed a comprehensive approach to understand H. pylori infection and elicits to rethink about the increasing threat posed by H. pylori and its treatment strategies.

EXPERT OPINION

To address these issues, nanotechnology has got huge potential to combat H. pylori infection and has made great progress in the field of biomedicine. Moreover, combinatory studies of natural products and probiotics in conjugation with NPs have proven efficiency against H. pylori infection, with an advantage of lower cytotoxicity, minimal side effects, and stronger antibacterial potential.[Figure: see text].

Specific gut microbiome signatures and the associated pro-inflamatory functions are linked to pediatric allergy and acquisition of immune tolerance

Understanding the functional potential of the gut microbiome is of primary importance for the design of innovative strategies for allergy treatment and prevention. Here we report the gut microbiome features of 90 children affected by food (FA) or respiratory (RA) allergies and 30 age-matched, healthy controls (CT). We identify specific microbial signatures in the gut microbiome of allergic children, such as higher abundance of Ruminococcus gnavus and Faecalibacterium prausnitzii, and a depletion of Bifidobacterium longum, Bacteroides dorei, B. vulgatus and fiber-degrading taxa. The metagenome of allergic children shows a pro-inflammatory potential, with an enrichment of genes involved in the production of bacterial lipo-polysaccharides and urease. We demonstrate that specific gut microbiome signatures at baseline can be predictable of immune tolerance acquisition. Finally, a strain-level selection occurring in the gut microbiome of allergic subjects is identified. R. gnavus strains enriched in FA and RA showed lower ability to degrade fiber, and genes involved in the production of a pro-inflammatory polysaccharide. We demonstrate that a gut microbiome dysbiosis occurs in allergic children, with R. gnavus emerging as a main player in pediatric allergy. These findings may open new strategies in the development of innovative preventive and therapeutic approaches. Trial: NCT04750980.

Here, the authors profile the taxonomic composition and genetic potential of the gut microbiome of children with food or respiratory allergies and find that the gut metagenome of these patients is characterized by higher proinflammatory potential and reduced capacity of degrading complex polysaccharides, with Ruminococcus gnavus playing a central role.

Bioderived materials that disarm the gut mucosal immune system: Potential lessons from commensal microbiota

Over the course of evolution, mammals and gut commensal microbes have adapted to coexist with each other. This homeostatic coexistence is dependent on an intricate balance between tolerogenic and inflammatory responses directed towards beneficial, commensal microbes and pathogenic intruders, respectively. Immune tolerance towards the gut microflora is largely sustained by immunomodulatory molecules produced by the commensals, which protect the bacteria from immune advances and maintain the gut's unique tolerogenic microenvironment, as well as systemic homeostasis. The identification and characterization of commensal-derived, tolerogenic molecules could lead to their utilization in biomaterials-inspired delivery schemes involving nano/microparticles or hydrogels, and potentially lead to the next generation of commensal-derived therapeutics. Moreover, gut-on-chip technologies could augment the discovery and characterization of influential commensals by providing realistic in vitro models conducive to finicky microbes. In this review, we provide an overview of the gut immune system, describe its intricate relationships with the microflora and identify major genera involved in maintaining tolerogenic responses and peripheral homeostasis. More relevant to biomaterials, we discuss commensal-derived molecules that are known to interface with immune cells and discuss potential strategies for their incorporation into biomaterial-based strategies aimed at culling inflammatory diseases. We hope this review will bridge the current findings in gut immunology, microbiology and biomaterials and spark further investigation into this emerging field. STATEMENT OF SIGNIFICANCE: Despite its tremendous potential to culminate into revolutionary therapeutics, the synergy between immunology, microbiology, and biomaterials has only been explored at a superficial level. Strategic incorporation of biomaterial-based technologies may be necessary to fully characterize and capitalize on the rapidly growing repertoire of immunomodulatory molecules derived from commensal microbes. Bioengineers may be able to combine state-of-the-art delivery platforms with immunomodulatory cues from commensals to provide a more holistic approach to combating inflammatory disease. This interdisciplinary approach could potentiate a neoteric field of research - "commensal-inspired" therapeutics with the promise of revolutionizing the treatment of inflammatory disease.

The Relationship Between Lower Respiratory Tract Microbiome and Allergic Respiratory Tract Diseases in Children

Similar to those in the upper respiratory tract, there are microbes present in the healthy human lower respiratory tract (LRT), including the lungs and bronchus. To evaluate the relationship between LRT microbiome and allergic respiratory diseases in children, we enrolled 68 children who underwent bronchoscopy from January 2018 to December 2018 in the affiliated hospital of the Capital Institute of Pediatrics. Using the total IgE (TIgE) values, children were divided into two groups: allergy sensitivity (AS) group and non-allergy sensitivity (NAS) group. Nucleic acid was extracted from samples of bronchoalveolar lavage fluid (BALF) from the two groups of children taken during bronchoscopy treatment and the 16S rDNA gene was sequenced and analyzed. The results showed that Haemophilus, Moraxella, Streptococcus, Prevotella, Neisseria, and Rothia were detected in all patients. There was a statistically significant difference in the composition and distribution of microbiota between the AS and NAS groups (p < 0.01). Analysis of the correlation of clinical indices and microbiome showed that TIgE was positively correlated with Bacteroidetes and negatively correlated with Streptococcus. Absolute lymphocyte count showed a relationship with Streptococcus, and the absolute neutrophil count or percentage of neutrophils showed a relationship with Cardiobacterium. The LRT microbiome functioned similarly to the intestinal microbiome. That is, the decrease in microbial diversity and the change in composition could lead to an increase in allergic symptoms. The microbiome of the LRT in children, especially that of Bacteriodetes and Streptococcus, showed a correlation with respiratory allergic diseases.

Anti-Allergic Diarrhea Effect of Diosgenin Occurs via Improving Gut Dysbiosis in a Murine Model of Food Allergy

Although the anti-allergic and prebiotic activities of diosgenin have been reported, the influence of diosgenin on intestinal immune and epithelial cells remains unclear. As the gut microbiota plays an important role in allergic disorders, this study aimed to investigate whether the anti-allergic diarrhea effect of diosgenin occurs via improving gut dysbiosis. In a murine food allergy model, the density of fecal bacterial growth on de Man, Rogossa and Sharpe (MRS) plates was diminished, and growth on reinforced clostridial medium (RCM) and lysogeny broth (LB) agar plates was elevated. However, the oral administration of diosgenin reduced the density of fecal bacteria and ameliorated diarrhea severity. Concordantly, reshaped diversity and an abundance of fecal microbes were observed in some of the diosgenin-treated mice, which showed a milder severity of diarrhea. The relevant fecal strains from the diosgenin-treated mice were defined and cultured with Caco-2 cells and allergen-primed mesenteric lymph node (MLN) cells. These strains exhibited protective effects against the cytokine/chemokine network and allergen-induced T-cell responses to varying degrees. By contrast, diosgenin limitedly regulated cytokine production and even reduced cell viability. Taken together, these findings show that diosgenin per se could not directly modulate the functionality of intestinal epithelial cells and immune cells, and its anti-allergic effect is most likely exerted via improving gut dysbiosis.

Regulation of oral antigen delivery early in life: Implications for oral tolerance and food allergy

The increasing incidence of food allergy remains a significant public health concern. Food allergy is partially due to a lack, or loss of tolerance to food allergens. Clinical outcomes surrounding early life practices, such as breastfeeding, antibiotic use and food allergen exposure, indicate the first year of life in children represents a unique time for shaping the immune system to reduce allergic outcomes. Animal models have identified distinctive aspects of when and where dietary antigens are delivered within the intestinal tract to promote oral tolerance prior to weaning. Additionally, animal models have identified contributions from maternal proteins from breast milk and bacterial products from the gut microbiota in regulating dietary antigen exposure and promoting oral tolerance, thus connecting decades of clinical observations on the benefits of breastfeeding, early food allergen introduction and antibiotic avoidance in the first year of life in reducing allergic outcomes. Here, we discuss how exposure to gut luminal antigens, including food allergens, is regulated in early life to generate protective tolerance and the implications of this process for preventing and treating food allergies.

Citrobacter koseri stimulates dendritic cells to induce IL-33 expression via abundant ATP production

Introduction. Food allergies (FAs) occur due to intestinal immune dysfunction elicited by dysbiotic conditions. It was previously determined by us that Citrobacter species propagate in the faeces of mice with FAs and worsen allergic symptoms by inducing the allergenic cytokine IL-33. Dendritic cells can play important roles in regulation of FA responses.Hypothesis. Citrobacter species propagating in intestines of mice worsen allergic symptoms by stimulating dendritic cells to induce IL-33 expression.Aim. The aim of the present study was to analyse whether C. koseri stimulates dendritic cells to induce IL-33 expression.Methodology. IL-33 expression was evaluated in a DC2.4 mouse dendritic cell line stimulated by live or heat-inactivated C. koseri JCM1658, ATP, LPS extracted from C. koseri JCM1658 or other enterobacteria by real-time PCR. The ATP concentration and number of live bacteria in the culture supernatant were measured simultaneously.Results. Live C. koseri JCM1658 induced higher levels of IL-33 expression than other enterobacteria tested, but such a response was not elicited by heat-inactivated C. koseri JCM1658. LPS extracted from C. koseri JCM1658 did not induce IL-33 expression and suppressed live C. koseri JCM1658-induced IL-33 expression via the activation of Toll-like receptor 4 signalling. Furthermore, ATP produced by C. koseri JCM1658 stimulated dendritic cells to induce IL-33 expression by stimulating the P2X₇ receptor, and LPS attenuated extracellular ATP-induced IL-33 expression. C. koseri JCM1658 was observed to proliferate more vigorously and produce more ATP than other enterobacteria.Conclusion. C. koseri acts as an allergenic bacterium through ATP production, stimulating dendritic cells to induce IL-33 expression, while LPS released from inactivated C. koseri JCM1658 attenuates this allergenicity.

Applications of Mouse Models to the Study of Food Allergy

Mouse models of allergic disease offer numerous advantages when compared to the models of other animals. However, selection of appropriate mouse models is critical to advance the field of food allergy by revealing mechanisms of allergy and for testing novel therapeutic approaches. All current mouse models for food allergy have weaknesses that may limit their applicability to human disease. Aspects such as the genetic predisposition to allergy or tolerance from the strain of mouse used, allergen dose, route of exposure (oral, intranasal, intraperitoneal, or epicutaneous), damage of the epithelial barrier, use of adjuvants, food matrix effects, or composition of the microbiota should be considered prior to the selection of a specific murine model and contemplated according to the intended purpose of the study. This chapter reviews our current knowledge on the application of mouse models to food allergy research and the variables that may influence the successful development of each type of model.

Perturbations to Homeostasis in Experimental Models Revealed Innate Pathways Driving Food Allergy

While type 2 immunity has been conventionally viewed as beneficial against helminths, venoms, and poisons, and harmful in allergy, contemporary research has uncovered its critical role in the maintenance of homeostasis. The initiation of a type 2 immune response involves an intricate crosstalk between structural and immune cells. Structural cells react to physical and chemical tissue perturbations by secreting alarmins, which signal the innate immune system to restore homeostasis. This pathway acts autonomously in the context of sterile injury and in the presence of foreign antigen initiates an adaptive Th2 response that is beneficial in the context of venoms, toxins, and helminths, but not food allergens. The investigation of the triggers and mechanisms underlying food allergic sensitization in humans is elusive because sensitization is a silent process. Therefore, the central construct driving food allergy modeling is based on introducing perturbations of tissue homeostasis along with an allergen which will result in an immunological and clinical phenotype that is consistent with that observed in humans. The collective evidence from multiple models has revealed the pre-eminent role of innate cells and molecules in the elicitation of allergic sensitization. We posit that, with the expanding use of technologies capable of producing formidable datasets, models of food allergy will continue to have an indispensable role to delineate mechanisms and establish causal relationships.

Microbiological, Physicochemical, and Immunological Analysis of a Commercial Cashew Nut-Based Yogurt

Nut-based milks and yogurts are gaining popularity, but may not offer the same benefits as dairy yogurts to consumers. Cashew nuts often cause severe allergic reactions, and cashew nut allergens are stable to several types of processing. To compare its characteristics to dairy yogurt and characterize the effects of fermentation on the Ana o 1-3 cashew nut allergens, a commercial yogurt made from cashew nuts (Cashewgurt) was evaluated for microbiological, physiochemical, and immunological properties. Average counts for lactobacilli and Streptococcus thermophilus were greater than 10 million colony forming units per milliliter, indicating the capacity to provide a health benefit. Cashewgurt pH and viscosity values were comparable to cow milk yogurts, and it was off white in color. SDS-PAGE analysis indicated a clear reduction in Ana o 1 and 2, and immuno-assay with polyclonal anti-cashew IgG antibody and cashew-allergic IgE indicated an overall reduction in allergen content. In contrast, SDS-PAGE, mass spectrometry, immunoblot, and ELISA all revealed that Ana o 3 was relatively unaffected by the fermentation process. In conclusion, Ana o 1 and Ana o 2 are sensitive to degradation, while Ana o 3 survives lactic acid bacterial fermentation during yogurt production. The analysis presented here indicates that cashew nut yogurt is not suitable for those with cashew nut allergy.

Acute Hemorrhagic Diarrhea Syndrome in Dogs

Acute hemorrhagic diarrhea syndrome is defined as sudden onset of severe bloody diarrhea frequently associated with vomiting, which results in severe, sometimes life-threatening dehydration. Although there is strong evidence that clostridial overgrowth and toxin release is responsible for the pathogenesis of the disease, the diagnosis is still based on exclusion of other causes for acute hemorrhagic diarrhea. With early and appropriate treatment, mainly based on fluid therapy, the prognosis is good and complications such as sepsis or severe hypoalbuminemia rarely occur.

Distinct Animal Food Allergens Form IgE-Binding Amyloids

Several animal food allergens assemble into amyloids under gastric-like environments. These aggregated structures provide Gad m 1 with an enhanced immunoglobulin E (IgE) interaction due to the fibrillation of the epitope regions. However, whether these properties are unique to Gad m 1 or shared by other food allergens has not yet been addressed. Using Bos d 5, Bos d 12 and Gal d 2 as allergen models and Gad m 1 as the control, aggregation reactions and the sera of milk, egg and fish allergic patients have been analyzed, assessing the IgE interactions of their amyloids. We found that amyloids formed by Bos d 12 and Gal d 2 full-length and truncated chains are recognized by the IgEs of milk and egg allergic patient sera. As with Gad m 1, in most cases amyloid recognition is higher than that of the native structure. Bos d 5 was not recognized under any fold by the IgE of the sera studied. These results suggest that the formation of IgE-binding amyloids could be a common feature to animal food allergens.

Recent advances in mechanisms of food allergy and anaphylaxis

Food allergens are innocuous proteins that promote tolerogenic adaptive immune responses in healthy individuals yet in other individuals induce an allergic adaptive immune response characterized by the presence of antigen-specific immunoglobulin E and type-2 immune cells. The cellular and molecular processes that determine a tolerogenic versus non-tolerogenic immune response to dietary antigens are not fully elucidated. Recently, there have been advances in the identification of roles for microbial communities and anatomical sites of dietary antigen exposure and presentation that have provided new insights into the key regulatory steps in the tolerogenic versus non-tolerogenic decision-making processes. Herein, we will review and discuss recent findings in cellular and molecular processes underlying food sensitization and tolerance, immunological processes underlying severity of food-induced anaphylaxis, and insights obtained from immunotherapy trials.

Human gut-derived commensal suppresses generation of T-cell response to gliadin in humanized mice by modulating gut microbiota

The human intestinal tract is colonized by a large number of diverse microorganisms that play various important physiologic functions. In inflammatory gut diseases including celiac disease (CeD), a dysbiotic state of microbiome has been observed. Interestingly, this perturbed microbiome is normalized towards eubiosis in patients showing recovery after treatment. The treatment has been observed to increase the abundance of beneficial microbes in comparison to non-treated patients. In this study, we investigated the effect of Prevotella histicola or Prevotella melaninogenica, isolated from the duodenum of a treated CeD patient, on the induction and maintenance of oral tolerance to gliadin, a CeD associated subgroup of gluten proteins, in NOD.DQ8.ABo transgenic mice. Conventionally raised mice on a gluten free diet were orally gavaged with bacteria before and after injection with pepsin trypsin digested gliadin (PTD-gliadin). P. histicola suppressed the cellular response to gliadin, whereas P. melaninogenica failed to suppress an immune response against gliadin. Interestingly, tolerance to gliadin in NOD.DQ8.ABo mice may be associated with gut microbiota as mice gavaged with P melaninogenica harbored a different microbial diversity as compared to P. histicola treated mice. This study provides experimental evidence that gut microbes like P. histicola from treated patients can suppress the immune response against gliadin epitopes.

Pediatric Allergic Diseases, Food Allergy, and Oral Tolerance

Pediatric allergic disease is a significant health concern worldwide, and the prevalence of childhood eczema, asthma, allergic rhinitis, and food allergy continues to increase. Evidence to support specific interventions for the prevention of eczema, asthma, and allergic rhinitis is limited, and no consensus on prevention strategies has been reached. Randomized controlled trials investigating the prevention of food allergy via oral tolerance induction and the early introduction of allergenic foods have been successful in reducing peanut and egg allergy prevalence. Infant weaning guidelines in the United Sates were recently amended to actively encourage the introduction of peanut for prevention of peanut allergy.

Increasing allergy: are antibiotics the elephant in the room?

Antibiotics cause dramatic changes to the human microbiome. The composition of the microbiome has been associated with changes in the immune system and these changes are beginning to be linked to immune diseases. Thus, antibiotics have been implicated as a significant contributor to the continual rise of allergies and autoimmune disease in developed countries. This recognition will hopefully result in the development of post-antibiotic therapies that restore a healthy microbiome and reduce immune system disorders.

An individualized mosaic of maternal microbial strains is transmitted to the infant gut microbial community

To understand the origins of the infant gut microbial community, we have used a published metagenomic dataset of the faecal microbiome of mothers and their related infants at early (4, 7 and 21 days) and late times (6-15 months) following birth. Using strain-tracking analysis, individual-specific patterns of microbial strain sharing were found between mothers and infants following vaginal birth. Overall, three mother-infant pairs showed only related strains, while 12 infants of mother-infant pairs contained a mosaic of maternal-related and unrelated microbes. Analysis of a second dataset from nine women taken at different times of pregnancy revealed individual-specific faecal microbial strain variation that occurred in seven women. To model transmission in the absence of environmental microbes, we analysed the microbial strain transmission to F1 progenies of human faecal transplanted gnotobiotic mice bred with gnotobiotic males. Strain-tracking analysis of five different dams and their F1 progeny revealed both related and unrelated microbial strains in the mother's faeces. The results of our analysis demonstrate that multiple strains of maternal microbes, some that are not abundant in the maternal faecal community, can be transmitted during birth to establish a diverse infant gut microbial community.

Recent developments and advances in atopic dermatitis and food allergy

This review highlights recent advances in atopic dermatitis (AD) and food allergy (FA), particularly on molecular mechanisms and disease endotypes, recent developments in global strategies for the management of patients, pipeline for future treatments, primary and secondary prevention and psychosocial aspects. During the recent years, there has been major advances in personalized/precision medicine linked to better understanding of disease pathophysiology and precision treatment options of AD. A greater understanding of the molecular and cellular mechanisms of AD through substantial progress in epidemiology, genetics, skin immunology and psychological aspects resulted in advancements in the precision management of AD. However, the implementation of precision medicine in the management of AD still requires the validation of reliable biomarkers, which will provide more tailored management, starting from prevention strategies towards targeted therapies for more severe diseases. Cutaneous exposure to food via defective barriers is an important route of sensitization to food allergens. Studies on the role of the skin barrier genes demonstrated their association with the development of IgE-mediated FA, and suggest novel prevention and treatment strategies for type 2 diseases in general because of their link to barrier defects not only in AD and FA, but also in asthma, chronic rhinosinusitis, allergic rhinitis and inflammatory bowel disease. The development of more accurate diagnostic tools, biomarkers for early prediction, and innovative solutions require a better understanding of molecular mechanisms and the pathophysiology of FA. Based on these developments, this review provides an overview of novel developments and advances in AD and FA, which are reported particularly during the last two years.

Microbial Regulation of Enteric Eosinophils and Its Impact on Tissue Remodeling and Th2 Immunity

Eosinophils have emerged as multifaceted cells that contribute to tissue homeostasis. However, the impact of the microbiota on their frequency and function at mucosal sites remains unclear. Here, we investigated the role of the microbiota in the regulation of enteric eosinophils. We found that small intestinal (SI) eosinophilia was significantly greater in germ-free (GF) mice compared to specific pathogen free (SPF) controls. This was associated with changes in the production of enteric signals that regulate eosinophil attraction and survival, and was fully reversed by complex colonization. Additionally, SI eosinophils of GF mice exhibited more cytoplasmic protrusions and less granule content than SPF controls. Lastly, we generated a novel strain of eosinophil-deficient GF mice. These mice displayed intestinal fibrosis and were less prone to allergic sensitization as compared to GF controls. Overall, our study demonstrates that commensal microbes regulate intestinal eosinophil frequency and function, which impacts tissue repair and allergic sensitization to food antigens. These data support a critical interplay between the commensal microbiota and intestinal eosinophils in shaping homeostatic, innate, and adaptive immune processes in health and disease.

Pursuing Human-Relevant Gut Microbiota-Immune Interactions

The gut microbiota is a complex and plastic network of diverse organisms intricately connected with human physiology. Recent advances in profiling approaches of both the microbiota and the immune system now enable a deeper exploration of immunity-microbiota connections. An important next step is to elucidate a human-relevant "map" of microbial-immune wiring while focusing on animal studies to probe a prioritized subset of interactions. Here, we provide an overview of this field's current status and discuss two approaches for establishing priorities for detailed investigation: (1) longitudinal intervention studies in humans probing the dynamics of both the microbiota and the immune system and (2) the study of traditional populations to assess lost features of human microbial identity whose absence may be contributing to the rise of immunological disorders. These human-centered approaches offer a judicious path forward to understand the impact of the microbiota in immune development and function.

Vancomycin-induced gut dysbiosis during Pseudomonas aeruginosa pulmonary infection in a mice model

Pseudomonas aeruginosa is one of the most common opportunistic pathogens causing respiratory infections in hospitals. Vancomycin, the antimicrobial agent usually used to treat bacterial nosocomial infections, is associated with gut dysbiosis. As a lung-gut immunologic axis has been described, this study aimed to evaluate both the immunologic and histopathologic effects on the lungs and the large intestine resulting from vancomycin-induced gut dysbiosis in the P. aeruginosa pneumonia murine model. Metagenomic analysis demonstrated that vancomycin-induced gut dysbiosis resulted in higher Proteobacteria and lower Bacteroidetes populations in feces. Given that gut dysbiosis could augment the proinflammatory status of the intestines leading to a variety of acute inflammatory diseases, bone marrow-derived macrophages were stimulated with cecal content from dysbiotic mice showing a higher expression of proinflammatory cytokines and lower expression of IL-10. Dysbiotic mice showed higher levels of viable bacteria in the lungs and spleen when acutely infected with P. aeruginosa, with more lung and cecal damage and increased IL-10 expression in bronchoalveolar lavage. The susceptible and tissue damage phenotype was reversed when dysbiotic mice received fecal microbiota transplantation. In spite of higher recruitment of CD11b+ cells in the lungs, there was no higher CD80+ expression, DC+ cell amounts or proinflammatory cytokine expression. Taken together, our results indicate that the bacterial community found in vancomycin-induced dysbiosis dysregulates the gut inflammatory status, influencing the lung-gut immunologic axis to favor increased opportunistic infections, for example, by P. aeruginosa.

A Benzenoid 4,7-Dimethoxy-5-Methyl-L, 3-Benzodioxole from Antrodia cinnamomea Attenuates Dendritic Cell-Mediated Th2 Allergic Responses

Dendritic cells (DCs) play a critical role in initiating immune responses; however, DCs also induce Th2-related allergic sensitivities. Thus, DCs become a target for therapeutic design in allergic diseases. In this study, we aim to investigate the anti-allergic effect of pure compounds from a medicinal mushroom Antrodia cinnamomea (Ac) on DC-induced allergic responses. We identified a benzenoid compound 4,7-dimethoxy-5-methyl-l,3-benzodioxole (DMB) which may modulate Th2 polarization in bone marrow-derived DCs (BMDCs) and in a murine food allergy model. DMB effectively reduced the Th2 adjuvant cholera toxin (CT)-induced BMDC maturation and cytokine production. In studying the mechanism, DMB blocked the molecular processes involved in Th2 induction, including cAMP activation, IL-33 production, and IRF4/Tim4 upregulation, in CT-activated BMDCs. Furthermore, DMB treatment attenuated the symptoms, clinical scores, and Th2 responses of CT-induced ovalbumin (OVA)-specific food allergy in mice at sensitization stage. These results indicated that DMB could suppress DC function for Th2 polarization and mitigate allergic responses. Thus, DMB may have potential to be a novel agent for preventing or treating food allergy.

Mechanisms of food allergy

Although oral tolerance is the normal physiologic response to ingested antigens, a breakdown in this process appears to have occurred in the past 2 decades, leading to an increasing prevalence of sensitization to food allergens. Over the past decade, basic research has intensified in an attempt to better understand the mechanisms leading to sensitization and disease versus desensitization and short- and long-term tolerance. In this review we assess various factors that can influence tissue and immune responses to food antigens, the current understanding of immune tolerance development, the role of the gastrointestinal microbiota, and current knowledge regarding immunologic mechanisms involved in desensitization and sustained unresponsiveness, although perhaps the latter is more appropriately termed remission.

Cow's Milk Allergy: Immunomodulation by Dietary Intervention

Cow’s milk proteins cause allergic symptoms in 2% to 3% of all infants. In these individuals, the physiological mechanism of tolerance is broken with subsequent possible sensitization to antigens, which can lead eventually to allergic responses. The present review aims to provide an overview of different aspects of immune modulation by dietary intervention in cow’s milk allergy (CMA). It focuses on pathogenetic mechanisms of different CMA related disorders, e.g., gastroesophageal reflux and eosinophilic esophagitis, highlighting the role of dietary management on innate and adaptive immune systems. The traditional dietary management of CMA has greatly changed in the last years, moving from a passive approach, consisting of an elimination diet to relieve symptoms, to a “proactive” one, meaning the possibility to actively modulate the immune system. Thus, new insights into the role of hydrolysates and baked milk in immunomodulation are addressed here. Additionally, nutritional components, such as pre- and probiotics, may target the immune system via microbiota, offering a possible road map for new CMA prevention and treatment strategies.

In Vitro and In Vivo Activities of Zinc Linolenate, a Selective Antibacterial Agent against Helicobacter pylori

Helicobacter pylori is a major global pathogen, and its infection represents a key factor in the etiology of various gastric diseases, including gastritis, peptic ulcers, and gastric carcinoma. The efficacy of current standard treatment for H. pylori infection including two broad-spectrum antibiotics is compromised by toxicity toward the gut microbiota and the development of drug resistance, which will likely only be resolved through novel and selective antibacterial strategies. Here, we synthesized a small molecule, zinc linolenate (ZnLla), and investigated its therapeutic potential for the treatment of H. pylori infection. ZnLla showed effective antibacterial activity against standard strains and drug-resistant clinical isolates of H. pyloriin vitro with no development of resistance during continuous serial passaging. The mechanisms of ZnLla action against H. pylori involved the disruption of bacterial cell membranes and generation of reactive oxygen species. In mouse models of multidrug-resistant H. pylori infection, ZnLla showed in vivo killing efficacy comparable and superior to the triple therapy approach when use as a monotherapy and a combined therapy with omeprazole, respectively. Moreover, ZnLla treatment induces negligible toxicity against normal tissues and causes minimal effects on both the diversity and composition of the murine gut microbiota. Thus, the high degree of selectivity of ZnLla for H. pylori provides an attractive candidate for novel targeted anti-H. pylori treatment.