Food allergy and the microbiome: Current understandings and future directions

The Role of the Microbiome in Allergy, Asthma, and Occupational Lung Disease

PURPOSE OF REVIEW

The human commensal microbiota is now widely accepted as a key regulator of human health and disease. The composition of the mucosal associated microbiota has been shown to play a critical role in the lung health. The role of the mucosal microbiota in the development and severity of allergy, asthma, and occupational lung disease is only beginning to take shape. However, advances in our understanding of these links have tremendous potential to led to new clinical interventions to reduce allergy, asthma, and occupational lung disease morbidity.

RECENT FINDINGS

We review recent work describing the relationship and role of the commensal microbiota in the development of allergy, asthma, and occupational lung disease. Our review primarily focuses on occupational exposures and the effects of the microbiome, both in composition and function. Data generated from these studies may lead to the development of interventions targeted at establishing and maintaining a healthy microbiota. We also highlight the role of environmental exposures and the effects on the commensal microbial community and their potential association with occupational lung disease. This review explores the current research describing the role of the human microbiome in the regulation of pulmonary health and disease, with a specific focus on the role of the mucosal microbiota in the development of allergy, asthma, and occupational lung disease.

Gender Differences in the Interplay between Vitamin D and Microbiota in Allergic and Autoimmune Diseases

The synergic role of vitamin D and the intestinal microbiota in the regulation of the immune system has been thoroughly described in the literature. Vitamin D deficiency and intestinal dysbiosis have shown a pathogenetic role in the development of numerous immune-mediated and allergic diseases. The physiological processes underlying aging and sex have proven to be capable of having a negative influence both on vitamin D values and the biodiversity of the microbiome. This leads to a global increase in levels of systemic inflammatory markers, with potential implications for all immune-mediated diseases and allergic conditions. Our review aims to collect and analyze the relationship between vitamin D and the intestinal microbiome with the immune system and the diseases associated with it, emphasizing the effect mediated by sexual hormones and aging.

Next generation probiotics: Engineering live biotherapeutics

The population dynamics of the human microbiome have been associated with inflammatory bowel disease, cancer, obesity, autoimmune diseases, and many other human disease states. An emerging paradigm in treatment is the administration of live engineered organisms, also called next-generation probiotics. However, the efficacy of these microbial therapies can be limited by the organism's overall performance in the harsh and nutrient-limited environment of the gut. In this review, we summarize the current state of the art use of bacterial and yeast strains as probiotics, highlight the recent development of genetic tools for engineering new therapeutic functions in these organisms, and report on the latest therapeutic applications of engineered probiotics, including recent clinical trials. We also discuss the supplementation of prebiotics as a method of manipulating the microbiome and improving the overall performance of engineered live biotherapeutics.

The age-specific microbiome of children with milk, egg, and peanut allergy

BACKGROUND

Immune regulation by gut microbiota is affected by dysbiosis and may precede food allergy onset. Prior studies lacked comparisons stratified by age and clinical phenotype.

OBJECTIVE

To assess the microbiome of children with food allergy (<3 years, 3-18 years) compared with similar aged children without food allergy.

METHODS

A real-world prospective cross-sectional study performed from 2014 to 2019 recruited children highly likely to have milk, egg, or peanut allergy defined by history and serum IgE or confirmed by food challenge. 16S ribosomal RNA sequencing identified stool microbial DNA. Alpha and beta diversity was compared between groups with food allergy and healthy controls stratified by age. Differential abundance for non a priori taxa was accepted at absolute fold-change greater than 2 and q value less than 0.05.

RESULTS

A total of 70 patients were included (56 with food allergy and 14 healthy controls). Groups were not significantly different in age, gender at birth, race, mode of delivery, breastfeeding duration, or antibiotic exposure. Younger children with food allergy had similar alpha diversity compared with controls. Beta diversity was significantly different by age (P = .001). There was differential abundance of several a priori (P < .05) taxa (including Clostridia) only in younger children. Both a priori (including Coprococcus and Clostridia) and non a priori (q < 0.05) Acidobacteria_Gp15, Aestuariispira, Tindallia, and Desulfitispora were significant in older children with food allergy, especially with peanut allergy.

CONCLUSION

Dysbiosis associates with food allergy, most prominent in older children with peanut allergy. Younger children with and without food allergy have fewer differences in gut microbiota. This correlates with clinical observations of persistence of peanut allergy and improved efficacy and safety of oral immunotherapy in younger children. Age younger than 3 years should be considered when initiating therapeutic interventions.

Differences in the Course, Diagnosis, and Treatment of Food Allergies Depending on Age-Comparison of Children and Adults

Food allergy (FA) has become a common global public health issue, with a growing prevalence in the modern world and a significant impact on the lives of patients, their families, and caregivers. It affects every area of life and is associated with elevated costs. Food allergy is an adverse immune reaction that occurs in response to a given food. The symptoms vary from mild to severe and can lead to anaphylaxis. This is why it is important to focus on the factors influencing the occurrence of food allergies, specific diagnostic methods, effective therapies, and especially prevention. Recently, many guidelines have emphasized the impact of introducing specific foods into a child's diet at an early age in order to prevent food allergies. Childhood allergies vary with age. In infants, the most common allergy is to cow's milk. Later in life, peanut allergy is more frequently diagnosed. Numerous common childhood allergies can be outgrown by adulthood. Adults can also develop new IgE-mediated FA. The gold standard for diagnosis is the oral provocation test. Skin prick tests, specific IgE measurements, and component-resolved diagnostic techniques are helpful in the diagnosis. Multiple different approaches are being tried as possible treatments, such as immunotherapy or monoclonal antibodies. This article focuses on the prevention and quality of life of allergic patients. This article aims to systematize the latest knowledge and highlight the differences between food allergies in pediatric and adult populations.

Gut microbiota and inflammatory mediators differentiate IgE mediated and non-IgE mediated cases of cow's milk protein at diagnosis

OBJECTIVE

Analyze fecal and blood samples at point of diagnosis in IgE mediated cow's milk protein allergy (CMPA) and non-IgE mediated (NIM)-CMPA patients to look for potential new biomarkers.

PATIENTS AND METHODS

Fourteen patients with IgE mediated CMPA and 13 with NIM-CMPA were recruited in three hospitals in the north of Spain, and were compared with 25 infants from a control group of the same age range. To characterize intestinal microbiota, 16S rDNA gene and internal transcribed spacer amplicons of bifidobacteria were sequenced with Illumina technology. Fatty acids were analyzed by gas chromatography, meanwhile intestinal inflammation markers were quantified by enzyme-linked immunosorbent assay and a multiplex system. Immunological analysis of blood was performed by flow cytometry.

RESULTS

The fecal results obtained in the NIM-CMPA group stand out. Among them, a significant reduction in the abundance of Bifidobacteriaceae and Bifidobacterium sequences with respect to controls was observed. Bifidobacterial species were also different, highlighting the lower abundance of Bifidobacterium breve sequences. Fecal calprotectin levels were found to be significantly elevated in relation to IgE mediated patients. Also, a higher excretion of IL-10 and a lower excretion of IL-1ra and platelet derived growth factor-BB was found in NIM-CMPA patients.

CONCLUSIONS

The differential fecal parameters found in NIM-CMPA patients could be useful in the diagnosis of NIM food allergy to CM proteins.

Gut microbiome in the first 1000 days and risk for childhood food allergy

OBJECTIVE

To summarize recent data on the association between gut microbiome composition and food allergy (FA) in early childhood and highlight potential host-microbiome interactions that reinforce or abrogate oral tolerance.

DATA SOURCES

PubMed search of English-language articles related to FA, other atopic disease, and the gut microbiome in pregnancy and early childhood.

STUDY SELECTIONS

Human studies published after 2015 assessing the relationship between the gut bacteriome and virome in the first 2 years of life and FA or food sensitization development in early childhood were prioritized. Additional human studies conducted on the prenatal gut microbiome or other atopic diseases and preclinical studies are also discussed.

RESULTS

Children who developed FA harbored lower abundances of Bifidobacterium and Clostridia species and had a less mature microbiome during infancy. The early bacterial microbiome protects against FA through production of anti-inflammatory metabolites and induction of T regulatory cells and may also affect FA risk through a role in trained immunity. Infant enteric phage communities are related to childhood asthma development, though no data are available for FA. Maternal gut microbiome during pregnancy is associated with childhood FA risk, potentially through transplacental delivery of maternal bacterial metabolites, though human studies are lacking.

CONCLUSION

The maternal and infant microbiomes throughout the first 1000 days of life influence FA risk through a number of proposed mechanisms. Further large, longitudinal cohort studies using taxonomic, functional, and metabolomic analysis of the bacterial and viral microbiomes are needed to provide further insight on the host-microbe interactions underlying FA pathogenesis in childhood.

Postpartum Maternal Anxiety Affects the Development of Food Allergy Through Dietary and Gut Microbial Diversity During Early Infancy

PURPOSE

We aimed to investigate the mediating factors between maternal anxiety and the development of food allergy (FA) in children until 2 years from birth.

METHODS

In this longitudinal cohort of 122 mother-child dyads from pregnancy to 24 months of age, we regularly surveyed maternal psychological states, infant feeding data, and allergic symptoms and collected stool samples at 6 months of age for microbiome analysis. Considering the temporal order of data collection, we investigated serial mediating effects and indirect effects among maternal anxiety, dietary diversity (DD), gut microbial diversity, and FA using structural equation modeling.

RESULTS

Among the 122 infants, 15 (12.3%) were diagnosed with FA. Increased maternal anxiety between 3 and 6 months after delivery was associated with a lower DD score. Infants with low DD at 4 months showed low gut microbial richness, which was associated with FA development. When the infants were grouped into 4 subtypes, using consensus clustering of 13 gut bacteria significantly associated with maternal anxiety and DD, Prevotella, Eubacterium, Clostridiales and Lachnospiraceae were more abundant in the group with lower FA occurrence.

CONCLUSIONS

Postpartum maternal anxiety, mediated by reduced DD and gut microbial diversity, may be a risk factor for the development of FA in infants during the first 2 years of life.

Potential of Lactobacillus plantarum A56 in relieving food allergy through immunoregulation, antioxidation, and reshaping intestinal microbiota

Food allergy is an abnormal immune reaction triggered by food protein antigens. Relevant studies have suggested that probiotic supplementation was with the potential to alleviate food allergy. This study aimed to explore the effects of Lactobacillus plantarum A56 on the alleviation of ovalbumin (OVA)-induced food allergy via immunomodulatory function, antioxidation, and modification of intestinal microbiota. Balb/c mice were sensitized with OVA (20 µg/mouse) by intraperitoneal injection for 3 weeks and accompanied by oral administration of L. plantarum A56 (109 CFU/mL), subsequently with orally challenged twice by OVA at 50 mg/mL for 1 week. The results showed that oral supplementation of L. plantarum A56 could effectively relieve allergic symptoms of mice, and decreased OVA-specific IgE and IgG1 concentrations. It also declined interleukin (IL)-4 level, raised interferon-γ (IFN-γ) in serum, and splenocyte supernatant, and the qPCR results were consistent with above results. Moreover, L. plantarum A56 treatment also fortified superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) levels, and reduced malondialdehyde (MDA) level in serum. The increased nuclear factor (erythroid-derived 2)-like 2 (Nrf2) and forkhead box O1 (Foxo1) expression indicated that L. plantarum A56 exerted antioxidation through Nrf2-Foxo1 pathway. In addition, L. plantarum A56 treatment elevated Bacteroidetes richness, ASV/OTU number, species diversity, etc. Notably, Spearman correlation analysis indicated that Bacteroidetes displayed obviously negative correlation with IgE and IgG1, but Actinobacteria and Acidobacteria exhibited significantly positive correlation with IgG1 and IgE. Collectively, these results suggested that L. plantarum A56 could alleviate OVA-induced food allergy by regulating Th1/Th2 imbalance, antioxidation, and modulating intestinal microbiota.

Addressing knowledge gaps in allergies among Syrian hospital patients: a cross-sectional study

Allergies have a significant impact on health and quality of life worldwide, yet there is limited research on the awareness and knowledge of allergies. This study aimed to explore the level of awareness and knowledge of allergies among visitors in Syrian hospitals. A cross-sectional study was conducted between May and September 2022, and a standardized international questionnaire was administered to 504 visitors in three hospitals in Syria. Data analysis was performed using the Statistical Package for Social Sciences (SPSS Inc., Chicago, IL, USA) version 23. The final sample comprised 504 questionnaires with 61.7% of participants achieving an average score. Statistical analysis revealed a significant difference in knowledge of allergy scores between the group with only elementary education (M = 3.76, SD = 1.67, p = 0.011), the group with no education (M = 3.65, SD = 1.65, p = 0.006), and the group with a university education (M = 4.44, SD = 1.25). Notably, no significant differences were found between the other educational groups. A one-way ANOVA was employed to assess the effect of place of living on knowledge of allergy, but no significant differences were observed between the groups (p = 0.462). Lastly, a significant negative correlation was detected between participant age and knowledge of allergy scores (r(502) = - 0.102, p = 0.022). Allergies represent a substantial global health concern that demands attention from healthcare providers, policymakers, and the public. This study emphasizes the importance of investing in health education and awareness campaigns to enhance knowledge and comprehension of allergies, particularly individuals with lower levels of education levels. By equipping individuals with the requisite information to effectively manage their allergies, their overall health and wellbeing can be improved.

Additive or Interactive Associations of Food Allergies with Glutathione S-Transferase Genes in Relation to ASD and ASD Severity in Jamaican Children

To investigate additive and interactive associations of food allergies with three glutathione S-transferase (GST) genes in relation to ASD and ASD severity in Jamaican children. Using data from 344 1:1 age- and sex-matched ASD cases and typically developing controls, we assessed additive and interactive associations of food allergies with polymorphisms in GST genes (GSTM1, GSTP1 and GSTT1) in relation to ASD by applying conditional logistic regression models, and in relation to ASD severity in ASD cases as measured by the Autism Diagnostic Observation Schedule-2nd Edition (ADOS-2) total and domains specific comparison scores (CSs) by fitting general linear models. Although food allergies and GST genes were not associated with ASD, ASD cases allergic to non-dairy food had higher mean ADOS-2 Restricted and Repetitive Behaviors (RRB) CS (8.8 vs. 8.0, P = 0.04). In addition, allergy to dairy was associated with higher mean RRB CS only among ASD cases with GSTT1 DD genotype (9.9 vs. 7.8, P < 0.01, interaction P = 0.01), and GSTP1 Val/Val genotype under a recessive genetic model (9.8 vs. 7.8, P = 0.02, interaction P = 0.06). Our findings are consistent with the role for GST genes in ASD and food allergies, though require replication in other populations.

Current insights into cow's milk allergy in children: Microbiome, metabolome, and immune response-A systematic review

The increasing prevalence of IgE-mediated cow's milk allergy (CMA) in childhood is a worldwide health concern. There is a growing awareness that the gut microbiome (GM) might play an important role in CMA development. Therefore, treatment with probiotics and prebiotics has gained popularity. This systematic review provides an overview of the alterations of the GM, metabolome, and immune response in CMA children and animal models, including post-treatment modifications. MEDLINE, PubMed, Scopus, and Web of Science were searched for studies on GM in CMA-diagnosed children, published before 1 March 2023. A total of 21 articles (13 on children and 8 on animal models) were included. The studies suggest that the GM, characterized by an enrichment of the Clostridia class and reductions in the Lactobacillales order and Bifidobacterium genus, is associated with CMA in early life. Additionally, reduced levels of short-chain fatty acids (SCFAs) and altered amino acid metabolism were reported in CMA children. Commonly used probiotic strains belong to the Bifidobacterium and Lactobacillus genera. However, only Bifidobacterium levels were consistently upregulated after the intervention, while alterations of other bacteria taxa remain inconclusive. These interventions appear to contribute to the restoration of SCFAs and amino acid metabolism balance. Mouse models indicate that these interventions tend to restore the Th 2/Th 1 balance, increase the Treg response, and/or silence the overall pro- and anti-inflammatory cytokine response. Overall, this systematic review highlights the need for multi-omics-related research in CMA children to gain a mechanistic understanding of this disease and to develop effective treatments and preventive strategies.

Glycosylation-modified antigens as a tolerance-inducing vaccine platform prevent anaphylaxis in a pre-clinical model of food allergy

The only FDA-approved oral immunotherapy for a food allergy provides protection against accidental exposure to peanuts. However, this therapy often causes discomfort or side effects and requires long-term commitment. Better preventive and therapeutic solutions are urgently needed. We develop a tolerance-inducing vaccine technology that utilizes glycosylation-modified antigens to induce antigen-specific non-responsiveness. The glycosylation-modified antigens are administered intravenously (i.v.) or subcutaneously (s.c.) and traffic to the liver or lymph nodes, respectively, leading to preferential internalization by antigen-presenting cells, educating the immune system to respond in an innocuous way. In a mouse model of cow's milk allergy, treatment with glycosylation-modified β-lactoglobulin (BLG) is effective in preventing the onset of allergy. In addition, s.c. administration of glycosylation-modified BLG shows superior safety and potential in treating existing allergies in combination with anti-CD20 co-therapy. This platform provides an antigen-specific immunomodulatory strategy to prevent and treat food allergies.

Comparing single versus multiple virus detection in pediatric acute gastroenteritis postimplementation of routine multiplex RT-PCR diagnostic testing

Utilizing multiplex real time polymerase chain reaction (RT-PCR) for rapid diagnosis of gastroenteritis, enables simultaneous detection of multiple pathogens. A comparative analysis of disease characteristics was conducted between cases with single and multiple viruses. Rotavirus vaccine was introduced in 2010, reaching a 70% coverage in 2 years. All rectal swabs collected from diarrheic children (<5 years) between December 2017 and March 2022 were included. Detection of the same viruses within 2 months was considered a single episode. Episodes with positive stool bacterial PCR were excluded. A total of 5879 samples were collected, revealing 86.9% (1509) with single virus detection and 13.1% (227) with multiple viruses. The most frequent combination was rotavirus and norovirus (27.8%), these infections followed a winter-spring seasonality akin to rotavirus. Children with multivirus infections exhibited higher immunodeficiency (OR 2.06) rates, but lower food allergy (OR 0.45) and prematurity rates (OR 0.55) compared to single infections. Greater disease severity, evaluated by the Vesikari score, was observed in multivirus episodes (p < 0.001, OR 1.12). Multivirus infections accounted for 13.1% of symptomatic cases in hospitalized young children. Despite vaccination efforts, rotavirus remained prominent, frequently in co-infections with norovirus. Overall, multivirus infections were linked to more severe diseases than single virus cases.

The Role of Gut Microbiota and Leaky Gut in the Pathogenesis of Food Allergy

Food allergy (FA) is a growing public health concern, with an increasing prevalence in Western countries. Increasing evidence suggests that the balance of human gut microbiota and the integrity of our intestinal barrier may play roles in the development of FA. Environmental factors, including industrialization and consumption of highly processed food, can contribute to altering the gut microbiota and the intestinal barrier, increasing the susceptibility to allergic sensitization. Compositional and functional alterations to the gut microbiome have also been associated with FA. In addition, increased permeability of the gut barrier allows the translocation of allergenic molecules, triggering Th2 immune responses. Preclinical and clinical studies have highlighted the potential of probiotics, prebiotics, and postbiotics in the prevention and treatment of FA through enhancing gut barrier function and promoting the restoration of healthy gut microbiota. Finally, fecal microbiota transplantation (FMT) is now being explored as a promising therapeutic strategy to prevent FA in both experimental and clinical studies. In this review article, we aim to explore the complex interplay between intestinal permeability and gut microbiota in the development of FA, as well as depict potential therapeutic strategies.

The mycobiome in atopic diseases: Inducers and triggers

Atopic diseases are characterized by type 2 inflammation, with high levels of allergen-specific TH2 cell immune responses and elevated production of IgE. These common disorders have increased in incidence around the world, which is partly explained by detrimental disturbances to the early-life intestinal microbiome. Although most studies have focused exclusively on bacterial members of the microbiome, intestinal fungi have started to be recognized for their impact on host immune development and atopy pathogenesis. From this perspective, we review recent findings demonstrating the strong interactions between members of the mycobiome and the host immune system early in life, leading to immune tolerance during eubiosis or inducing sensitization and overt TH2 cell responses during dysbiosis. Current evidence places intestinal fungi as central players in the development of allergic diseases and potential targets for atopy prevention and treatments.

Longitudinal dynamics of the gut microbiome and metabolome in peanut allergy development

BACKGROUND

Rising rates of peanut allergy (PA) motivate investigations of its development to inform prevention and therapy. Microbiota and the metabolites they produce shape food allergy risk.

OBJECTIVE

We sought to gain insight into gut microbiome and metabolome dynamics in the development of PA.

METHODS

We performed a longitudinal, integrative study of the gut microbiome and metabolome of infants with allergy risk factors but no PA from a multicenter cohort followed through mid-childhood. We performed 16S rRNA sequencing, short chain fatty acid measurements, and global metabolome profiling of fecal samples at infancy and at mid-childhood.

RESULTS

In this longitudinal, multicenter sample (n = 122), 28.7% of infants developed PA by mid-childhood (mean age 9 years). Lower infant gut microbiome diversity was associated with PA development (P = .014). Temporal changes in the relative abundance of specific microbiota and gut metabolite levels significantly differed in children who developed PA. PA-bound children had different abundance trajectories of Clostridium sensu stricto 1 sp (false discovery rate (FDR) = 0.015) and Bifidobacterium sp (FDR = 0.033), with butyrate (FDR = 0.045) and isovalerate (FDR = 0.036) decreasing over time. Metabolites associated with PA development clustered within the histidine metabolism pathway. Positive correlations between microbiota, butyrate, and isovalerate and negative correlations with histamine marked the PA-free network.

CONCLUSION

The temporal dynamics of the gut microbiome and metabolome in early childhood are distinct for children who develop PA. These findings inform our thinking on the mechanisms underlying and strategies for potentially preventing PA.

Immunomodulatory effect of marine lipids on food allergy

Seafood is highly enriched in n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFAs), particularly eicosapentaenoic acid (EPA, 20:5 n-3) and docosahexaenoic acid (DHA, 22:6 n-3), in contrast to the ultra-processed foods included in the modern Western diet that have high levels of n-6 linoleic acid (LA, 18:2 n-6), precursor for the pro-inflammatory n-6 arachidonic acid (ARA, 20:4 n-6). The capacity of marine lipids to reduce plasmatic triglycerides and blood pressure have been well-described. Moreover, recent studies have also raised evidence of a potential regulatory action of marine lipids on inflammation, the immune system, and food allergy (FA). FA is considered one of the main concerns to become life threatening in food safety. The prevalence of this emerging global problem has been increasing during the last two decades, especially in industrialized countries. About a 6-8% of young children and 2-4% of adults is estimated to be affected by FA. The main objective of the current study is to update the existing knowledge, but also the limitations, on the potential impact of marine lipids and their lipid mediators in regulating immunity, inflammation, and ultimately, food allergies. In particular, the focus is on the effect of marine lipids in modulating the key factors that control the sensitization and effector phases of FA, including gut microbiota (GM), inflammation, and immune system response. Results in animal models highlight the positive effect that consuming marine lipids, whether as a supplement or through seafood consumption, may have a relevant role in improving gut dysbiosis and inflammation, and preventing or reducing the severity of FA. However, more systematic studies in humans are needed to optimize such beneficial actions to each particular FA, age, and medical condition to reach an effective clinical application of marine lipids to improve FAs and their outcomes.

Early-life risk factors for food allergy: Dietary and environmental factors revisited

There appears a steep increase in the prevalence of food allergy worldwide in the past few decades. It is believed that, rather than genetic factors, the recently altered dietary and environmental factors are the driving forces behind the rapid increase of this disease. Accumulating evidence has implied that external exposures that occurred in prenatal and postnatal periods could affect the development of oral tolerance in later life. Understanding the potential risk factors for food allergy would greatly benefit the progress of intervention and therapy. In this review, we present updated knowledge on the dietary and environmental risk factors in early life that have been shown to impact the development of food allergy. These predominantly include dietary habits, microbial exposures, allergen exposure routes, environmental pollutants, and so on. The key evidence, conflicts, and potential research topics of each theory are discussed, and associated interventional strategies to prevent the disease development and ameliorate treatment burden are included. Accumulating evidence has supported the causative role of certain dietary and environmental factors in the establishment of oral tolerance in early life, especially the time of introducing allergenic foods, skin barrier function, and microbial exposures. In addition to certain immunomodulatory factors, increasing interest is raised toward modern dietary patterns, where adequately powered studies are required to identify contributions of those modifiable risk factors. This review broadens our understanding of the connections between diet, environment, and early-life immunity, thus benefiting the progress of intervention and therapy of food allergy.

Oral exposure to Staphylococcus aureus enterotoxin B could promote the Ovalbumin-induced food allergy by enhancing the activation of DCs and T cells

Introduction

Recent work highlighted the importance of environmental contaminants in the development of allergic diseases.

Methods

The intestinal mucosal barrier, Th (helper T) cells, DCs (dendritic cells), and intestinal flora were analyzed with flow cytometry, RNA-seq, and 16s sequencing in the present study to demonstrate whether the exposure of enterotoxins like Staphylococcus aureus enterotoxin B (SEB) in allergens could promote the development of food allergy.

Results and discussion

We found that co-exposure to SEB and Ovalbumin (OVA) could impair the intestinal barrier, imbalance the intestinal Th immune, and cause the decline of intestinal flora diversity in OVA-sensitized mice. Moreover, with the co-stimulation of SEB, the transport of OVA was enhanced in the Caco-2 cell monolayer, the uptake and presentation of OVA were promoted in the bone marrow dendritic cells (BMDCs), and Th cell differentiation was also enhanced. In summary, co-exposure to SEB in allergens should be considered a food allergy risk factor.

The Role of IgA in the Manifestation and Prevention of Allergic Immune Responses

PURPOSE OF REVIEW

Immunoglobulin A (IgA) mediates immune exclusion of antigens in the gut. Notably, IgA plays also a role in the prevention of IgE-mediated allergies and induction of immune tolerance. The present review addresses the role of IgA in the manifestation of IgE-mediated allergies, including allergen-specific immunotherapy (AIT), the regulation of IgA production, and the mechanism of IgA in immune cell activation.

RECENT FINDINGS

The majority of studies report an association of IgA with the induction of immune tolerance in IgE-mediated allergies. However, reports on the involvement of humoral and mucosal IgA, IgA subtypes, monomeric and polymeric IgA, and the mechanism of IgA-mediated immune cell activation are confounding. Effects by IgA are likely mediated by alteration of microbiota, IgE-blocking capacity, or activation of inhibitory signaling pathways. However, the precise mechanism of IgA-regulation, the contribution of serum and/or mucosal IgA, and IgA1/2 subtypes, on the manifestation of IgE-mediated allergies, and the underlying immune modulatory mechanism are still elusive.

Thymic Stromal Lymphopoietin (TSLP), Its Isoforms and the Interplay with the Epithelium in Allergy and Asthma

Thymic stromal lymphopoietin (TSLP) is a pleiotropic cytokine that has emerged as a critical player in the development and progression of allergy and asthma. It is primarily produced by epithelial cells and functions as a potent immune system activator. TSLP acts through interaction with its receptor complex, composed of the TSLP receptor (TSLPR) and interleukin-7 receptor alpha chain (IL-7Rα), activating downstream complex signalling pathways. The TSLP major isoform, known as long-form TSLP (lfTSLP), is upregulated in the airway epithelium of patients with allergic diseases. More research is warranted to explore the precise mechanisms by which short-form TSLP (sfTSLP) regulates immune responses. Understanding the dynamic interplay between TSLP and the dysfunctional epithelium provides insights into the mechanisms underlying allergy and asthma pathogenesis. Targeting TSLP represents an important therapeutic strategy, as it may upstream disrupt the inflammatory cascade and alleviate symptoms associated with allergic inflammation.

Sugar-Sweetened Beverages and Allergy Traits at Second Year of Life: BRISA Cohort Study

Sugar-Sweetened Beverage (SSBs) consumption has risen in early life and it is plausible that it might increase children's risk of allergies. In this paper, we analyzed the association of SSB consumption with allergies in children's second year of life. This study analyzed data from a São Luís BRISA prenatal cohort in the follow-up of children (n = 1144) in their second year of life. Allergy Traits were a latent variable deduced from medical diagnoses of allergic rhinitis, atopic dermatitis, and food allergies. SSBs were investigated as a percentage of daily calories based on 24 h recalls, including industrialized fruit juices, soft drinks, and ready-made chocolate milk. Other variables analyzed were socioeconomic status, age, body mass index z-score, episodes of diarrhea, and breastfeeding. Our finds were that higher consumption of daily calories from SSBs was associated with higher Allergy Trait values (SC = 0.174; p = 0.025); older age (SC = -0.181; p = 0.030) was associated with lower Allergy Trait values; and episodes of diarrhea were correlated with Allergy Traits (SC = 0.287; p = 0.015). SSB exposure was associated with Allergy Traits in children's second year of life; thus, abstaining from these beverages may also confer additional advantages in curtailing allergic diseases during early childhood.

Using the collaborative cross to identify the role of host genetics in defining the murine gut microbiome

BACKGROUND

The human gut microbiota is a complex community comprised of trillions of bacteria and is critical for the digestion and absorption of nutrients. Bacterial communities of the intestinal microbiota influence the development of several conditions and diseases. We studied the effect of host genetics on gut microbial composition using Collaborative Cross (CC) mice. CC mice are a panel of mice that are genetically diverse across strains, but genetically identical within a given strain allowing repetition and deeper analysis than is possible with other collections of genetically diverse mice.

RESULTS

16S rRNA from the feces of 167 mice from 28 different CC strains was sequenced and analyzed using the Qiime2 pipeline. We observed a large variance in the bacterial composition across CC strains starting at the phylum level. Using bacterial composition data, we identified 17 significant Quantitative Trait Loci (QTL) linked to 14 genera on 9 different mouse chromosomes. Genes within these intervals were analyzed for significant association with pathways and the previously known human GWAS database using Enrichr analysis and Genecards database. Multiple host genes involved in obesity, glucose homeostasis, immunity, neurological diseases, and many other protein-coding genes located in these regions may play roles in determining the composition of the gut microbiota. A subset of these CC mice was infected with Salmonella Typhimurium. Using infection outcome data, an increase in abundance of genus Lachnospiraceae and decrease in genus Parasutterella correlated with positive health outcomes after infection. Machine learning classifiers accurately predicted the CC strain and the infection outcome using pre-infection bacterial composition data from the feces.

CONCLUSION

Our study supports the hypothesis that multiple host genes influence the gut microbiome composition and homeostasis, and that certain organisms may influence health outcomes after S. Typhimurium infection. Video Abstract.

Intestinal microenvironment-mediated allergic dynamic phenotypes and endotypes in the development of gluten allergy

This study aimed to investigate the dynamic changes in intestinal microenvironment factors in the development of gluten-induced allergy (GA). Our results showed that GA provoked increasingly severe allergic phenotypes such as allergic and diarrheal symptoms with the gluten sensitization frequency, which was accompanied by dynamically rising levels of gluten-specific immunoglobulin (Ig) E, IgG2a and IgA, serum histamine, T cell-related inflammatory cytokines, and intestinal indexes. An increase in luminal pH was more significant in the large intestine versus the small intestine, which was due to a dynamic decline in colonic short-chain fatty acid levels. Both antioxidant capacity and intestinal permeability in the large intestine varied with the GA severity, as evidenced by a dynamic increase in the malondialdehyde content and a decrease in the superoxide dismutase activity and total antioxidant capacity. Moreover, we demonstrated that intestinal microenvironment dysbiosis occurred before a true allergy reaction began. Spearman correlation analysis suggested that the characteristic bacterial cluster, namely Alistipes, Desulfovibrio, Ileibacterium, Parabacteroides, and Ruminococcus torques group, are essential in the association between GA and intestinal microenvironment homeostasis.

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.

Peanut thresholds in peanut-allergic children are related to dietary composition

BACKGROUND

There is no clear explanation for the large variation in threshold levels among peanut-allergic children. We hypothesized that diet composition can partly explain this variation in thresholds, as nutrients and foods influence the intestinal barrier function and microbiota.

AIM

to explore the relationship between the threshold levels for peanut and nutritional intake and gut microbial composition in peanut-allergic children.

METHODS

In this explorative cross-sectional study the cumulative threshold levels for peanut were determined by oral food challenge tests. Data on nutrients and foods consumed were obtained from 3-day food diaries. Microbial composition of faeces and saliva were determined by molecular microbiota detection technique. Multivariable linear regression analysis and multiple logistic regression were used to explore the associations, adjusted for energy and senitization.

RESULTS

Sixty-five children were included, of whom 32 (49%) (median age 50 months, IQR 28.0-96.5) had a positive oral food challenge. Significant positive associations were found between the intake of total carbohydrates, vitamin A and cumulative threshold levels for peanut, while significant negative associations were found for long-chain polyunsaturated fatty acids, linoleic acid and omega-6 fatty acids. No associations were found between threshold levels and microbial composition of faeces and saliva. However, a significant higher abundance of Proteobacteria and Bacteroidetes in saliva (p = 0.011 and 0.04, respectively) and of Proteobacteria in faeces (p = 0.003) were found in children with a positive peanut challenge compared to children with a negative peanut challenge.

CONCLUSION

As a novel concept, this study showed that dietary composition is related to threshold levels for peanut.

Alteration of taste perception, food neophobia and oral microbiota composition in children with food allergy

Currently, the mechanisms underlying sensory perception and sensory performance in children with food allergies are far from being understood. As well, only recently, single research afforded the oral host-commensal milieu, addressing oral microbial communities in children with peanut allergies. To bridge the current gaps in knowledge both in the sensory and microbial fields, a psychophysiological case-control study was performed in allergic children (n = 29) and a healthy sex-age-matched control group (n = 30). Taste perception, food neophobia, and liking were compared in allergic and non-allergic children. The same subjects were characterized for their oral microbiota composition by addressing saliva to assess whether specific profiles were associated with the loss of oral tolerance in children with food allergies. Our study evidenced an impaired ability to correctly identify taste qualities in the allergic group compared to controls. These results were also consistent with anatomical data related to the fungiform papillae on the tongue, which are lower in number in the allergic group. Furthermore, distinct oral microbial profiles were associated with allergic disease, with significant down-representations of the phylum Firmicutes and of the genera Veillonella spp., Streptococcus spp., Prevotella spp., and Neisseria spp. For the first time, this study emphasizes the link between sensory perception and food allergy, which is a novel and whole-organism view of this pathology. Our data indicated that an impaired taste perception, as regards both functionality and physiologically, was associated with food allergy, which marginally influences the food neophobia attitude. It is also accompanied by compositional shifts in oral microbiota, which is, in turn, another actor of this complex interplay and is deeply interconnected with mucosal immunity. This multidisciplinary research will likely open exciting new approaches to therapeutic interventions.

Diet-microbiota crosstalk and immunity to helminth infection

Helminths are large multicellular parasites responsible for widespread chronic disease in humans and animals. Intestinal helminths live in close proximity with the host gut microbiota and mucosal immune network, resulting in reciprocal interactions that closely influence the course of infections. Diet composition may strongly regulate gut microbiota composition and intestinal immune function and therefore may play a key role in modulating anti-helminth immune responses. Characterizing the multitude of interactions that exist between different dietary components (e.g., dietary fibres), immune cells, and the microbiota, may shed new light on regulation of helminth-specific immunity. This review focuses on the current knowledge of how metabolism of dietary components shapes immune response during helminth infection, and how this information may be potentially harnessed to design new therapeutics to manage parasitic infections and associated diseases.

The Role of Gluten in Gastrointestinal Disorders: A Review

Gluten is only partially digested by intestinal enzymes and can generate peptides that can alter intestinal permeability, facilitating bacterial translocation, thus affecting the immune system. Few studies addressed the role of diet with gluten in the development of intestinal inflammation and in other gastrointestinal disorders. The aim of this narrative review was to analyse the role of gluten in several gastrointestinal diseases so as to give a useful overview of its effectiveness in the prevention and management of these disorders.

Biomaterial Strategies for Selective Immune Tolerance: Advances and Gaps

Autoimmunity and allergies affect a large number of people across the globe. Current approaches to these diseases target cell types and pathways that drive disease, but these approaches are not cures and cannot differentiate between healthy cells and disease-causing cells. New immunotherapies that induce potent and selective antigen-specific tolerance is a transformative goal of emerging treatments for autoimmunity and serious allergies. These approaches offer the potential of halting-or even reversing-disease, without immunosuppressive side effects. However, translating successful induction of tolerance to patients is unsuccessful. Biomaterials offer strategies to direct and maximize immunological mechanisms of tolerance through unique capabilities such as codelivery of small molecules or signaling molecules, controlling signal density in key immune tissues, and targeting. While a growing body of work in this area demonstrates success in preclinical animal models, these therapies are only recently being evaluated in human trials. This review will highlight the most recent advances in the use of materials to achieve antigen-specific tolerance and provide commentary on the current state of the clinical development of these technologies.

The high dose of inulin exacerbated food allergy through the excess accumulation of short-chain fatty acids in a BABL/c mouse model

Inulin dietary supplement is conventionally beneficial to gut health and can potentially prevent food allergy (FA). This study aimed to determine how dietary inulin interventions at different doses affect the OVA-induced FA in a BALB/c mouse model. Although the middle dose of inulin (50 mg per mouse) showed the best therapeutic effect on FA, high-inulin supplementation (80 mg per mouse) provoked severe allergic and intestinal inflammatory responses, which were characterized by elevated serum allergic inflammation-related factor levels, dysfunctional gut barrier, unbalanced luminal pH value, decrease in intestinal antioxidant capacity, and disordered gut microecology. Moreover, profiling of SCFAs indicated that the high-inulin-induced excess accumulation of SCFAs in the colon was responsible for the gut immune disorders. Spearman correlation analysis unraveled that the featured bacterial taxa in the high-inulin-treated mice were Ruminococcaceae and Bifidobacterium, of which the relative abundance was negatively correlated with expression of tight junction proteins and improvement of T cell homeostasis, and positively correlated with levels of allergic inflammation-related indexes. Our work suggested that high-inulin dietary supplementation can be detrimental to allergic individuals and highlighted the importance for personalized use of inulin-type dietary supplements to safely improve human health.

Allergic sensitization to foods in India and other Low-Middle-income countries

Food allergy is an important cause of morbidity, significantly affecting the quality of life of the sufferer. Most food allergy research has been undertaken in high-income countries. Here, we summarize literature regarding food allergy in India and other low-middle-income countries (LMIC). We provide summaries of self-reported adverse food reactions and food sensitization in these regions by reviewing published community-based studies of prevalence, burden, and risk factors. We identified 2 community-based studies of food allergy prevalence in Karnataka, India, which estimate that food allergy affects just 0.14% of children and 1.2% of adults. The overall prevalence of allergic sensitization to 'any' food was 26.5% in adults and 19.1% in children by serum-specific IgE; but only 4.48% in children by skin prick test. We identified a further 28 studies in other LMICs, mainly from China but also Turkey, South Africa, Ghana, Mexico, Brazil, Thailand, Philippines, and Korea. The overall prevalence of allergic sensitization to 'any' food ranged from 0.11% to 16.8% in children using serum-specific IgE and 0.14% to 9.6% in children by skin prick test. The questionnaires and skin prick testing materials used and number of allergens tested varied significantly between studies. Other than Karnataka, there is no information on prevalence of food sensitization and probable food allergy in the community in India. Similar lack of information is noted among the majority of the 136 LMICs. Where community-based studies have been undertaken, there is wide variation in the prevalence and patterns of food sensitization across different LMICs, at least partly due to variations in study methodology. International collaboration is required in order to formally assess food allergy prevalence and burden across representative samples from multiple LMICs.

The intriguing possibility of using probiotics in allergen-specific immunotherapy

Allergen immunotherapy (AIT) can be considered the etiological therapy for allergic rhinitis and hymenoptera venom allergy. Its role is increasingly emerging in the context of IgE mediated food allergy, where the achievement of tolerance, or the permanent resolution of an allergy, represents the optimal goal of AIT. AIT treatment, indicated in adults and children with allergic rhinitis, has a preventative effect on the development of asthma and can also be used when asthma is associated to rhinitis; however, it is not the first choice for treatment of isolated asthma. While knowledge on immunological mechanisms, efficacy, and safety of AIT is known, an intriguing line of investigation has arisen on how the action of AIT is modulated by the use of probiotics, starting from awareness that the microbiome is altered in allergic conditions: the use of probiotics in inducing the stimulation of innate immunity via toll-like receptor activation, thus acting as adjuvants in AIT, is hereby examined. Therefore, by analyzing literature on AIT and probiotics, we intend to draw attention to how the role and use of AIT are emerging as being increasingly important for both the short- and long-term management of allergic diseases and how recourse probiotics may represent an additional therapeutic strategy to modulate the effectiveness of AIT. However, further investigations are needed to better identify which probiotics to use, the dosage, and the optimal duration to obtain correct immunomodulation, and how to best customize their use, including a "AIT + probiotics" strategy in the field of precision medicine.

Gut Microbiome Proteomics in Food Allergies

Food allergies (FA) have dramatically increased in recent years, particularly in developed countries. It is currently well-established that food tolerance requires the strict maintenance of a specific microbial consortium in the gastrointestinal (GI) tract microbiome as alterations in the gut microbiota can lead to dysbiosis, causing inflammation and pathogenic intestinal conditions that result in the development of FA. Although there is currently not enough knowledge to fully understand how the interactions between gut microbiota, host responses and the environment cause food allergies, recent advances in '-omics' technologies (i.e., proteomics, genomics, metabolomics) and in approaches involving systems biology suggest future headways that would finally allow the scientific understanding of the relationship between gut microbiome and FA. This review summarizes the current knowledge in the field of FA and insights into the future advances that will be achieved by applying proteomic techniques to study the GI tract microbiome in the field of FA and their medical treatment. Metaproteomics, a proteomics experimental approach of great interest in the study of GI tract microbiota, aims to analyze and identify all the proteins in complex environmental microbial communities; with shotgun proteomics, which uses liquid chromatography (LC) for separation and tandem mass spectrometry (MS/MS) for analysis, as it is the most promising technique in this field.

Management of Adult Patients with Gastrointestinal Symptoms from Food Hypersensitivity-Narrative Review

The incidence of food hypersensitivity has increased dramatically over the years not only among children but also in adults. Adult patients are usually less suspected of food hypersensitivity symptoms since food allergies are more typical for small children, with a tendency to outgrow the condition. The aim of this article is to increase awareness of hypersensitivity to food symptoms and their diagnosis and treatment possibilities among gastroenterologists and other health care professionals dealing with this type of patient. Symptoms of many gastrointestinal disorders, especially functional, may be driven by different types of mechanisms, and food intolerance or allergy should be considered as a potential cause. This article presents the current understanding of the epidemiology, diagnosis and treatment of immune- and non-immune-mediated food-induced diseases. Diagnosis of food hypersensitivity is based mainly on medical history, different types of sensitivity tests, e.g., hydrogen breath test, specific IgE (sIgE) serum concentration, tissue eosinophil count, skin tests and oral food challenges considered as a "gold standard" for food allergy. Elimination diet and pharmacologic treatment for allergy symptoms are first-line therapies. Eosinophilic gastrointestinal diseases are often caused by non-IgE-mediated food allergies, require endoscopic biopsy samples to confirm diagnosis and proper elimination diet often combined with steroids or proton pump inhibitor agents for treatment. Mast cell activation syndrome (MCAS) derives from pathologic reaction of mast cells with increased tryptase serum level as a marker. Symptoms may occur in the digestive, respiratory, skin, neurologic and cardiovascular system. Treatment is based on histamine type 1, type 2 (H1, H2) receptor antagonists and other mast cell stabilizing agents. Carbohydrate intolerances are the most common type of food hypersensitivity in adult patients, and an elimination diet is effective for reducing symptoms. Food additives hypersensitivity remains difficult to diagnose, but use of a diet low in chemical substances alleviates symptoms and helps to diagnose the triggering factors.

Microbiome Therapeutics for Food Allergy

The prevalence of food allergies continues to rise, and with limited existing therapeutic options there is a growing need for new and innovative treatments. Food allergies are, in a large part, related to environmental influences on immune tolerance in early life, and represent a significant therapeutic challenge. An expanding body of evidence on molecular mechanisms in murine models and microbiome associations in humans have highlighted the critical role of gut dysbiosis in the pathogenesis of food allergies. As such, the gut microbiome is a rational target for novel strategies aimed at preventing and treating food allergies, and new methods of modifying the gastrointestinal microbiome to combat immune dysregulation represent promising avenues for translation to future clinical practice. In this review, we discuss the intersection between the gut microbiome and the development of food allergies, with particular focus on microbiome therapeutic strategies. These emerging microbiome approaches to food allergies are subject to continued investigation and include dietary interventions, pre- and probiotics, microbiota metabolism-based interventions, and targeted live biotherapeutics. This exciting frontier may reveal disease-modifying food allergy treatments, and deserves careful study through ongoing clinical trials.

Gut Microbiota and Fecal Microbiota Transplantation in Patients with Food Allergies: A Systematic Review

The prevalence of food allergies (FAs) has increased considerably in recent decades, with the only available treatment being the avoidance of the specific food items causing the allergy. FAs may have a major impact on quality of life, and it is of great interest to explore new strategies to prevent and treat FAs. Some studies show an altered gut microbiota profile in individuals with FAs, and the modulation of gut microbiota is therefore proposed as a potential strategy for prevention and treatment. This systematic review aimed to investigate: (1) the gut microbiota profile in individuals with FAs compared to healthy individuals and (2) the effect of fecal microbiota transplantation (FMT) on gut microbiota profiles and/or allergy symptoms. A literature search was conducted in PubMed (Medline) on 5 April 2022. Of the 236 publications identified, 12 studies were included based on inclusion and exclusion criteria. Eleven of these studies reported results on the gut microbiota in children with FAs compared to healthy controls (HCs). The majority of studies (six studies) observed no difference in alpha diversity when comparing children with FAs to HCs; however, a difference in beta diversity was observed in five studies. At the phylum level, we observed a high abundance of Firmicutes (six studies) and Proteobacteria (five studies), whereas a low abundance of Bacteroidetes (5 studies) was observed in children with FAs compared to HCs. Of the 12 included studies, four explored the effect of FMT on gut microbiota and/or allergy symptoms. Three studies reported that transferring gut microbiota from children without FAs to germ-free mice, protected the mice against allergic reactions, whereas one study did not report findings on the allergic symptoms. The results on gut microbiota after FMT varied and were too divergent to draw any conclusions. Overall, our results suggest that there are differences in the gut microbiota profile in individuals with FAs compared to individuals without FAs. FMT seems to be a promising strategy to prevent allergic symptoms but needs to be further explored in animal and human models. As the findings in this review are based on a small number of studies (12 studies), further studies are warranted before any clear conclusions can be drawn regarding gut microbiota profiles and the effect of FMT on individuals with FAs.

The Environmental Microbiome, Allergic Disease, and Asthma

The environmental microbiome represents the entirety of the microbes and their metabolites that we encounter in our environments. A growing body of evidence supports the role of the environmental microbiome in risk for and severity of allergic diseases and asthma. The environmental microbiome represents a ubiquitous, lifelong exposure to non-self antigens. During the critical window between birth and 1 year of life, interactions between our early immune system and the environmental microbiome have 2 consequences: our individual microbiome is populated by environmental microbes, and our immune system is trained regarding which antigens to tolerate. During this time, a diversity of exposures appears largely protective, dramatically decreasing the risk of developing allergic diseases and asthma. As we grow older, our interactions with the environmental microbiome change. While it continues to exert influence over the composition of the human microbiome, the environmental microbiome becomes increasingly a source for antigenic stimulation and infection. The same microbial exposure protective against disease development may exacerbate disease severity. Although much has been learned about the importance of the environmental microbiome in allergic disease, much more remains to be understood about these complicated interactions between our environment, our microbiome, our immune system, and disease.

Current Use of Probiotics and Prebiotics in Allergy

The microbiome plays an important role in the pathogenesis of allergic diseases. This review updates the reader on studies aimed at influencing allergic diseases through modulation of the gut microflora. A nonsystematic review of the literature was performed, focusing on relevant trials evaluating the effect of probiotics/prebiotics/symbiotics in the prevention and treatment of allergic disease. For each allergic disease, we were able to find not only a substantial number of clinical trials but also systematic reviews. Specific guidelines, based on systematic reviews and meta-analyses, are available for the prevention of allergic disease and for the treatment of food allergy. In each of the areas examined-allergic rhinitis, allergic asthma, atopic dermatitis, food allergy, and gastrointestinal allergies-there are substantial uncertainties in the efficacy of gut microflora modulation in prevention and treatment. At present, practicing clinicians can avail themselves of intestinal flora modulators as an adjunct in the prevention of atopic dermatitis but not of other forms of allergic diseases. Their effects on the treatment of allergic diseases remain controversial.

Predictors and biomarkers of food allergy and sensitization in early childhood

OBJECTIVE

To review existing literature on the early risk factors for and biomarkers of food allergy (FA) and food sensitization (FS) and highlight opportunities for future research that will further the understanding of FA pathogenesis in infancy and toddlerhood.

DATA SOURCES

PubMed search of English-language articles related to FA and atopic disease.

STUDY SELECTIONS

Human studies with outcomes related to FA, FS, and other atopic disease in childhood were selected and reviewed. Studies published after 2015 were prioritized.

RESULTS

The prevalence of FA has greatly increased in recent decades and is now a global public health concern. A complex network of early life risk factors has been associated with development of FA and FS in childhood. Food allergy has a genetic component, but recent evidence suggests that interactions between risk alleles and other environmental exposures are important for disease pathogenesis, potentially through epigenetic mechanisms. Lifestyle factors, such as delivery mode, antibiotic use, and pet exposure also influence FA risk, which may be through their effect on the early life gut microbiome. How these early life risk factors, along with route and timing of antigen exposure, collectively target the developing immune system remains an ongoing and important area of study.

CONCLUSION

The current body of evidence emphasizes the first 1000 days of life as a critical period for FA development. More observational studies and adequately powered clinical trials spanning early pregnancy through childhood are needed to identify novel biomarkers and risk factors that can predict susceptibility toward or protection against FA.

Extremely small and incredibly close: Gut microbes as modulators of inflammation and targets for therapeutic intervention

Chronic inflammation is a hallmark for a variety of disorders and is at least partially responsible for disease progression and poor patient health. In recent years, the microbiota inhabiting the human gut has been associated with not only intestinal inflammatory diseases but also those that affect the brain, liver, lungs, and joints. Despite a strong correlation between specific microbial signatures and inflammation, whether or not these microbes are disease markers or disease drivers is still a matter of debate. In this review, we discuss what is known about the molecular mechanisms by which the gut microbiota can modulate inflammation, both in the intestine and beyond. We identify the current gaps in our knowledge of biological mechanisms, discuss how these gaps have likely contributed to the uncertain outcome of fecal microbiota transplantation and probiotic clinical trials, and suggest how both mechanistic insight and -omics-based approaches can better inform study design and therapeutic intervention.

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.

Novel perspective on the regulation of food allergy by probiotic: The potential of its structural components

Food allergy (FA) is a global public health issue with growing prevalence. Increasing evidence supports the strong correlation between intestinal microbiota dysbiosis and food allergies. Probiotic intervention as a microbiota-based therapy could alleviate FA effectively. In addition to improving the intestinal microbiota disturbance and affecting microbial metabolites to regulate immune system, immune responses induced by the recognition of pattern recognition receptors to probiotic components may also be one of the mechanisms of probiotics protecting against FA. In this review, it is highlighted in detail about the regulatory effects on the immune system and anti-allergic potential of probiotic components including the flagellin, pili, peptidoglycan, lipoteichoic acid, exopolysaccharides, surface (S)-layer proteins and DNA. Probiotic components could enhance the function of intestinal epithelial barrier as well as regulate the balance of cytokines and T helper (Th) 1/Th2/regulatory T cell (Treg) responses. These evidences suggest that probiotic components could be used as nutritional or therapeutic agents for maintaining immune homeostasis to prevent FA, which will contribute to providing new insights into the resolution of FA and better guidance for the development of probiotic products.

How primary care providers can help prevent food allergies

PURPOSE OF REVIEW

IgE-mediated food allergy rates have increased in recent decades, yet treatment options remain limited. Prevention strategies are thus essential. We will review recent research and consensus guidelines for food allergy prevention.

RECENT FINDINGS

Research has continued to support that early introduction of allergens via the gastrointestinal tract induces tolerance and prevents development of food allergy. In contrast, allergen sensitization may occur via transcutaneous allergen exposure. This is supported by research that shows a decreased risk of food allergy with aggressive treatment of atopic dermatitis. More recent research suggests that transcutaneous sensitization could also be facilitated by frequent emollient use in the absence of atopic dermatitis but definitive research is lacking. Murine models have shown a likely role of dysbiosis, or disruption of the body's normal healthy microbiome, in development of food allergy, yet human studies have yet to show a conclusive benefit of probiotics in the prevention of food allergy.

SUMMARY

Important approaches for food allergy prevention are: introduction of peanut and cooked egg at 4-6 months, early introduction of other allergenic foods, and early diagnosis and treatment of atopic dermatitis (because of a predisposition to food sensitization through the damaged skin barrier). More research is needed to clarify the role, if any, of emollient use and probiotics.