Cellular and molecular pathways through which commensal bacteria modulate sensitization to dietary antigens

Gynostemma pentaphyllum saponins shield mice from peanut allergy by modulation of gut microbiota: A novel approach for peanut allergy management

BACKGROUND

Food allergies, particularly peanut (PN) allergies, are a growing concern, with fatal anaphylaxis incidents often reported. While palforzia is the sole FDA-approved drug for managing PN allergies, it is not universally effective.

PURPOSE

This study aimed to investigate the potential of Gynostemma pentaphyllum saponins (GpS) as a novel therapeutic agent for PN allergy through modulation of gut microbiota, addressing the limitations of current treatments.

METHODS

To elucidate the role of GpS on peanut allergy, we first built a PN-sensitized C57BL/6J model mice. Through comprehensive sequencing analysis, we identified Parabacteroides distasonis as a key bacterium triggering PN sensitization. Employing the same mouse model, GpS was evaluated for its effects on anaphylactic symptoms, serum immunoglobulin levels, and allergy-related biomarkers. 16S rRNA sequencing and transcriptomic analysis were applied to investigate the impact of GpS on the host's gut epithelium and microbiome.

RESULTS

GpS treatment effectively reduced anaphylactic symptoms in PN-sensitized mice, as shown by decreased IgG1, total IgE, and PN-specific IgE levels. It also modulated the immune response by suppressing proinflammatory cytokines (IL-1β, IFN-γ, IL-21) and chemokines (CCL5, CCL12, CCL17, CCL22), while enhancing anti-inflammatory cytokines (IL-4, IL-10, IL-12, IL-13). Fecal microbial transplant from GpS-treated Model mice to PN-sensitized mice displayed anti-peanut allergy effects. Additionally, the administration of GpS-enhanced bacteria (Clostridium aldenese or Lactobacillus murinus), alleviated anaphylactic symptoms and reduced serum allergy markers in PN-sensitized mice.

CONCLUSION

To conclude, we revealed the intestinal environment, signaling molecules, mucosal cytokines, and commensal microbial profiles in the peanut-sensitized mouse model. We further presented evidence for the protective effect of GpS against PN allergen sensitization by downregulating a series of food-allergy-associated biomarkers and cytokines via the modulation of gut bacteria. More importantly, supported by both in vitro and in vivo experiments, we demonstrated that the protective effect of GpS against PN-allergy is through the enhancement of two commensal bacteria, Clostridium aldenese, and Lactobacillus murinus.

Crosstalk between the gut microbiota and innate lymphoid cells in intestinal mucosal immunity

The human gastrointestinal mucosa is colonized by thousands of microorganisms, which participate in a variety of physiological functions. Intestinal dysbiosis is closely associated with the pathogenesis of several human diseases. Innate lymphoid cells (ILCs), which include NK cells, ILC1s, ILC2s, ILC3s and LTi cells, are a type of innate immune cells. They are enriched in the mucosal tissues of the body, and have recently received extensive attention. The gut microbiota and its metabolites play important roles in various intestinal mucosal diseases, such as inflammatory bowel disease (IBD), allergic disease, and cancer. Therefore, studies on ILCs and their interaction with the gut microbiota have great clinical significance owing to their potential for identifying pharmacotherapy targets for multiple related diseases. This review expounds on the progress in research on ILCs differentiation and development, the biological functions of the intestinal microbiota, and its interaction with ILCs in disease conditions in order to provide novel ideas for disease treatment in the future.

Gut microbiota: A target for prebiotics and probiotics in the intervention and therapy of food allergy

Food allergy has become a major public health problem all over the world. Evidence showed that allergic reactions induced by food proteins often lead to disturbances in the gut microbiota (symbiotic bacteria). Gut microbiota plays an important role in maintaining the balance between intestinal immune tolerance and allergic reactions. Dietary intervention has gradually become an important method for the prevention and treatment of allergic diseases, and changing the composition of gut microbiota through oral intake of prebiotics and probiotics may serve as a new effective adjuvant treatment measure for allergic diseases. In this paper, the main mechanism of food allergy based on intestinal immunity was described firstly. Then, the clinical and experimental evidence showed that different prebiotics and probiotics affect food allergy by changing the structure and composition of gut microbiota was summarized. Moreover, the molecular mechanism in which the gut microbiota and their metabolites may directly or indirectly regulate the immune system or intestinal epithelial barrier function to affect food immune tolerance of host were also reviewed to help in the development of food allergy prevention and treatment strategies based on prebiotics and probiotics.

Research Progress on the Correlation between the Intestinal Microbiota and Food Allergy

The increasing incidence of food allergy is becoming a substantial public health concern. Increasing evidence suggests that alterations in the composition of the intestinal microbiota play a part in the development of food allergy. Additionally, the application of probiotics to correct gut microbiota imbalances and regulate food allergy has become a research hotspot. However, the mechanism by which the gut microbiota regulates food allergy and the efficacy of probiotics are still in the preliminary exploration stage, and there are no clear and specific conclusions. The aim of this review is to provide information regarding the immune mechanism underlying food allergy, the correlation between the intestinal microbiota and food allergy, a detailed description of causation, and mechanisms by which the intestinal microbiota regulates food allergy. Subsequently, we highlight how probiotics modulate the gut microbiome–immune axis to alleviate food allergy. This study will contribute to the dovetailing of bacterial therapeutics with immune system in allergic individuals to prevent food allergy and ameliorate food allergy symptoms.

Natural immunomodulating substances used for alleviating food allergy

Food allergy is a serious health problem affecting more than 10% of the human population worldwide. Medical treatments for food allergy remain limited because immune therapy is risky and costly, and anti-allergic drugs have many harmful side effects and can cause drug dependence. In this paper, we review natural bioactive substances capable of alleviating food allergy. The sources of the anti-allergic substances reviewed include plants, animals, and microbes, and the types of substances include polysaccharides, oligosaccharides, polyphenols, phycocyanin, polyunsaturated fatty acids, flavonoids, terpenoids, quinones, alkaloids, phenylpropanoids, and probiotics. We describe five mechanisms involved in anti-allergic activities, including binding with epitopes located in allergens, affecting the gut microbiota, influencing intestinal epithelial cells, altering antigen presentation and T cell differentiation, and inhibiting the degranulation of effector cells. In the discussion, we present the limitations of existing researches as well as promising advances in the development of anti-allergic foods and/or immunomodulating food ingredients that can effectively prevent or alleviate food allergy. This review provides a reference for further research on anti-allergic materials and their hyposensitizing mechanisms.

The microbiome and its impact on food allergy and atopic dermatitis in children

Food allergy (FA) affects 4-10% of children, especially children with atopic dermatitis (AD). During infancy the gut microbiome may determine both the course of FA and tolerance to food allergens. Analogically, the skin microbiome changes in the course of AD. Most studies have associated FA with a lower abundance and diversity of Lactobacillales and Clostridiales, but greater numbers of Enterobacterales, while AD in children has been associated with lower numbers of Staphylococcus epidermidis and S. hominis but an abundance of S. aureus and Streptococcus species. An understanding of the impact of the microbiome on the clinical course of FA and AD may allow for the development of new models of allergy treatment and prevention.

Microbially competent 3D skin: a test system that reveals insight into host-microbe interactions and their potential toxicological impact

The skin`s microbiome is predominantly commensalic, harbouring a metabolic potential far exceeding that of its host. While there is clear evidence that bacteria-dependent metabolism of pollutants modulates the toxicity for the host there is still a lack of models for investigating causality of microbiome-associated pathophysiology or toxicity. We now report on a biologically characterised microbial-skin tissue co-culture that allows studying microbe-host interactions for extended periods of time in situ. The system is based on a commercially available 3D skin model. In a proof-of-concept, this model was colonised with single and mixed cultures of two selected skin commensals. Two different methods were used to quantify the bacteria on the surface of the skin models. While Micrococcus luteus established a stable microbial-skin tissue co-culture, Pseudomonas oleovorans maintained slow continuous growth over the 8-day cultivation period. A detailed skin transcriptome analysis showed bacterial colonisation leading to up to 3318 significant changes. Additionally, FACS, ELISA and Western blot analyses were carried out to analyse secretion of cytokines and growth factors. Changes found in colonised skin varied depending on the bacterial species used and comprised immunomodulatory functions, such as secretion of IL-1α/β, Il-6, antimicrobial peptides and increased gene transcription of IL-10 and TLR2. The colonisation also influenced the secretion of growth factors such as VFGFA and FGF2. Notably, many of these changes have already previously been associated with the presence of skin commensals. Concomitantly, the model gained first insights on the microbiome's influence on skin xenobiotic metabolism (i.e., CYP1A1, CYP1B1 and CYP2D6) and olfactory receptor expression. The system provides urgently needed experimental access for assessing the toxicological impact of microbiome-associated xenobiotic metabolism in situ.

[Immunological background and pathomechanisms of food allergies]

Recent advances in immunology have greatly improved our understanding of the pathomechanisms of food allergies. Food allergies are caused and maintained by complex interactions of the innate and adaptive immune system involving antigen-presenting cells (APC), T cells, group 2 innate lymphoid cells (ILC2), epithelial cells (EC) and effectors cells. Additionally, epigenetic factors, the intestinal microbiome and nutritional factors modulating the gastrointestinal lymphatic tissue probably have a significant impact on allergy development. However, why certain individuals develop tolerance while others mount allergic responses, the factors defining the allergenicity of food proteins, as well as the immunological mechanisms triggering allergy development have yet to be analyzed in detail.

Influence of microbiome and diet on immune responses in food allergy models

The intestinal immune system is intimately connected with the vast array of microbes present within the gut and the diversity of food components that are consumed daily. The discovery of novel molecular mechanisms, which mediate host-microbe-nutrient communication, have highlighted the important roles played by microbes and dietary factors in influencing mucosal inflammatory and allergic responses. In this review, we summarize the recent important findings in this field, which are important for food allergy and particularly relevant to animal models of food allergy.

The role of gene-environment interactions in the development of food allergy

The rates of IgE-mediated food allergy have increased globally, particularly in developed countries. The rising incidence is occurring more rapidly than changes to the genome sequence would allow, suggesting that environmental exposures that alter the immune response play an important role. Genetic factors may also be used to predict an increased predisposition to these environmental risk factors, giving rise to the concept of gene-environment interactions, whereby differential risk of environmental exposures is mediated through the genome. Increasing evidence also suggests a role for epigenetic mechanisms, which are sensitive to environmental exposures, in the development of food allergy. This paper discusses the current state of knowledge regarding the environmental and genetic risk factors for food allergy and how environmental exposures may interact with immune genes to modify disease risk or outcome.

Eosinophilic esophagitis: published evidences for disease subtypes, indications for patient subpopulations, and how to translate patient observations to murine experimental models

Eosinophilic esophagitis (EoE) is a chronic inflammatory disorder of the esophagus and commonly classified as a Th2-type allergy. Major advances in our understanding of the EoE pathophysiology have recently been made, but clinicians struggle with highly unpredictable therapy responses indicative of phenotypic diversity within the patient population. Here, we summarize evidences for the existence of EoE subpopulations based on diverse inflammatory characteristics of the esophageal tissue in EoE. Additionally, clinical characteristics of EoE patients support the concept of disease subtypes. We conclude that clinical and experimental evidences indicate that EoE is an umbrella term for conditions that are unified by esophageal eosinophilia but that several disease subgroups with various inflammatory esophageal patterns and/or different clinical features exist. We further discuss strategies to study the pathophysiologic differences as observed in EoE patients in murine experimental EoE. Going forward, models of EoE that faithfully mimic EoE subentities as defined in humans will be essential because mechanistic studies on triggers which regulate the onset of diverse EoE subpopulations are not feasible in patients. Understanding how and why different EoE phenotypes develop will be a first and fundamental step to establish strategies that integrate individual variations of the EoE pathology into personalized therapy.

Epigenetic modifications: mechanisms of disease and biomarkers of food allergy

The rise in IgE-mediated food allergy in recent times is the likely result of gene-environment interactions mediated via epigenetic pathways. As epigenetic modifications, including DNA methylation, are at the interface between the environment and the genome, they may be ideal biomarkers of modifiable disease pathways. High-throughput methylation profiling of immune cell subtypes or whole blood from patients allows the identification of disease specific epigenetic variants. If faithfully tracking with disease parameters, these 'signatures' may have clinical applications as biomarkers of disease or therapeutic response. Development of such tools will depend on a number of factors, including determining the most appropriate experimental approach, analysis methodology, patient groups, and informative target cells/tissues. Here we discuss these potential applications and their implications for food allergy practise.

Recent advances in food allergy

Summary Food allergy is a public health issue that has significantly increased worldwide in the past decade, affecting consumers’ quality of life and making increasing demands on health service resources. Despite recent advances in many areas of diagnosis and treatment, our general knowledge of the basic mechanisms of the disease remain limited i.e., not at pace with the exponential number of new cases and the explosion of new technologies. Many important key questions remain: What defines a major allergen? Why do some individuals develop food allergies and others do not? Which are the environmental factors? Could the environmental factors be monitored through epigenetics or modified by changes in the microbiome? Can tolerance to food be induced? Why are some foods more likely to trigger allergies than others? Does the route and timing of exposure have any role on sensitization? These and many other related questions remain unanswered. In this short review some of these topics are addressed in the light of recent advances in the area.

Recent research advances in eosinophilic esophagitis

PURPOSE OF REVIEW

Eosinophilic esophagitis (EoE) is a chronic allergic disease triggered by food allergens with an increasing prevalence. This review highlights recent research advances in EoE with a focus on the literature of the past 18 months.

RECENT FINDINGS

The incidence of EoE in the black population is higher than previously suggested. A novel locus spanning CAPN14 is associated with EoE. Diagnostic tests utilizing an analysis of EoE-specific transcriptome have been improved. Standardized EoE symptom score systems have been established. Treatment trials show the promise and limitations of allergen avoidance, antiinflammatory reagents, and anti-interleukin-13 antibodies. Insights into disease mechanisms highlight the role of invariant natural killer T cells and group 2 innate immune cells. Epithelial barrier protein desmoglein 1, bone morphogenetic protein antagonist follistatin, neurotrophic tyrosine kinase receptor type 1, and CAPN14 have been defined as new potential therapeutic targets in EoE as regulators of the inflammatory interleukin-13-axis. The role of IgG4 in the disease mechanisms has been suggested.

SUMMARY

Genetic predisposition influenced by environmental factors increases EoE susceptibility. Research identifying the critical events leading to allergen sensitization and the esophagus-specific responses that drive EoE is evolving, and will lead to a better understanding of EoE and new therapeutic approaches for the disease.