Dysregulation of Intestinal Microbiota Elicited by Food Allergy Induces IgA-Mediated Oral Dysbiosis

Impact of ovalbumin allergy on oral and gut microbiome dynamics in 6-week-old BALB/c mice

Background

The gut microbiota is known to have a significant impact on the development of food allergy, and several recent studies have suggested that both oral microbiota, which first come into contact with allergenic foods, may have a profound influence on the development of food allergy.

Methods

In this study, we have established an ovalbumin-sensitive mice model by utilizing ovalbumin as a sensitizing agent. Subsequently, we performed a comprehensive analysis of the gut and oral microbiota in ovalbumin-sensitive mice and the control mice using full-length 16S rRNA sequencing analysis.

Results

Interestingly, both the gut and oral microbiota of ovalbumin-sensitized mice exhibited significant dysbiosis. The relative abundance of s__Lactobacillus_intestinalis in the gut microbiota of ovalbumin-sensitive mice exhibited a significant decrease, whereas the abundance of s__Agrobacterium_radiobacter and s__Acinetobacter_sp__CIP_56_2 displayed a significant increase. Furthermore, the relative abundance of s__unclassified_g__Staphylococcus, s__Streptococcus_hyointestinalis, and s__unclassified_g__Dechloromonas in the oral microbiota of ovalbumin-sensitive mice revealed a significant decrease. In contrast, the abundance of 63 other species, including s__Proteiniclasticum_ruminis, s__Guggenheimella_bovis, and s__Romboutsia_timonensis, demonstrated a significant increase. The random forest classifier achieved the best accuracy in predicting the outcome of food allergy using three gut and three oral biomarkers, with accuracies of 94.12 and 100%, respectively. Based on the predictions of the PICRUSt2 analysis, the only consistent finding observed across multiple samples from both the groups of mice was a significant up-regulation of the nucleotide-binding oligomerization domain (NOD)-like receptor signaling pathway in the ovalbumin-sensitized mice.

Conclusion

Our study demonstrates that ovalbumin-sensitized mice experience substantial alterations in both gut and oral microbial composition and structure, and specific strains identified in this study may serve as potential biomarkers for food allergy screening. Moreover, our findings highlight that the oral environment, under the same experimental conditions, exhibited greater precision in detecting a larger number of species. Additionally, it is worth noting that the NOD-like receptor signaling pathway plays a vital role in the pathogenesis of OVA (ovalbumin)-induced allergy. These findings will generate novel concepts and strategies in the realm of food allergy prevention and treatment.

Allergen-specific IgA and IgG antibodies as inhibitors of mast cell function in food allergy

Food allergy, a group of adverse immune responses to normally innocuous food protein antigens, is an increasingly prevalent public health issue. The most common form is IgE-mediated food allergy in which food antigen-induced crosslinking of the high-affinity IgE-receptor, FcεRI, on the surface of mast cells triggers the release of inflammatory mediators that contribute to a wide range of clinical manifestations, including systemic anaphylaxis. Mast cells also play a critical function in adaptive immunity to foods, acting as adjuvants for food-antigen driven Th2 cell responses. While the diagnosis and treatment of food allergy has improved in recent years, no curative treatments are currently available. However, there is emerging evidence to suggest that both allergen-specific IgA and IgG antibodies can counter the activating effects of IgE antibodies on mast cells. Most notably, both antigen-specific IgA and IgG antibodies are induced in the course of oral immunotherapy. In this review, we highlight the role of mast cells in food allergy, both as inducers of immediate hypersensitivity reactions and as adjuvants for type 2 adaptive immune responses. Furthermore, we summarize current understanding of the immunomodulatory effects of antigen-specific IgA and IgG antibodies on IgE-induced mast cell activation and effector function. A more comprehensive understanding of the regulatory role of IgA and IgG in food allergy may provide insights into physiologic regulation of immune responses to ingested antigens and could seed novel strategies to treat allergic disease.

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.

Microbiota and IL-33/31 Axis Linkage: Implications and Therapeutic Perspectives in Atopic Dermatitis and Psoriasis

Microbiome dysbiosis and cytokine alternations are key features of atopic dermatitis (AD) and psoriasis (PsO), two of the most prevalent and burdensome pruritic skin conditions worldwide. Interleukin (IL)-33 and IL-31 have been recognized to be major players who act synergistically in the pathogenesis and maintenance of different chronic inflammatory conditions and pruritic skin disorders, including AD and PsO, and their potential role as therapeutic targets is being thoroughly investigated. The bidirectional interplay between dysbiosis and immunological changes has been extensively studied, but there is still debate regarding which of these two factors is the actual causative culprit behind the aetiopathological process that ultimately leads to AD and PsO. We conducted a literature review on the Pubmed database assessing articles of immunology, dermatology, microbiology and allergology with the aim to strengthen the hypothesis that dysbiosis is at the origin of the IL-33/IL-31 dysregulation that contributes to the pathogenesis of AD and PsO. Finally, we discussed the therapeutic options currently in development for the treatment of these skin conditions targeting IL-31, IL-33 and/or the microbiome.

Subgingival Microbiota and Periodontal Clinical Status in Patients with Plaque Psoriasis: A Cross-Sectional Study

Plaque Psoriasis (PP) and periodontitis are inflammatory disorders with a bidirectional association. They both have a qualitatively similar immune-modulatory cascade, cytokine profile, and a recently described dysbiosis. Different oral bacterial species compositions in the periodontal pocket might play a role in the development of PP. To describe the subgingival microbiota of the Mexican population with PP and the periodontal conditions. Subjects were divided into two groups: periodontal health (PH) (PH-non-PP, PH-PP) and periodontitis (PD) (P-non-PP, PD-PP). Following clinical examination, the patients were classified into three groups according to the degree of psoriasis as measured by the Psoriasis Area Severity Index (PASI) and the periodontal status according to the parameters of the American Academy of Periodontology (AAP). Subgingival microbiota samples of each patient were used to determine 40 species of periodontal bacteria by checkerboard DNA-DNA hybridization. IL-2 and IL-6 were measured by ELISA. Of the forty-eight patients with PP, 21 patients had PH and 27 patients had PD. PD-PP group has a significant increase in the percentage of plaque, gingival redness, pocket probing depth, and clinical attachment loss (P<0.001) compared to PH-PP group. Microbiologically PD-PP exhibited significantly higher mean counts for A. georgiae, A. israelii, A. naeslundii from blue complex (P<0.001) than PD-non-PP. Moreover, the counts of these Actinomyces in PD-PP increased according to the severity of index PASI. The concentration of IL-2 and IL-6 were increased in saliva from PH-PP and PD-PP patients compared to PH non-PP. PP individuals harbored a particular sub-gingival microbiota profile different from non-PP. The severity of psoriasis was related to dysbiosis of microbiota -PASI > 5 related to periodontitis with the predominance of Actinomyces periodontal, irrespective of their periodontal condition. Finally, the severity of psoriasis could be unbalanced in subgingival microbiota and increase the risk to develop periodontitis.

Immunomodulatory role of oral microbiota in inflammatory diseases and allergic conditions

In recent years, the interplay between oral microbiota and systemic disease has gained attention as poor oral health is associated with several pathologies. The oral microbiota plays a role in the maintenance of overall health, and its dysbiosis influences chronic inflammation and the pathogenesis of gum diseases. Periodontitis has also been associated with other diseases and health complications such as cancer, neurogenerative and autoimmune disorders, chronic kidney disease, cardiovascular diseases, rheumatic arthritis, respiratory health, and adverse pregnancy outcomes. The host microbiota can influence immune cell development and immune responses, and recent evidence suggests that changes in oral microbiota composition may also contribute to sensitization and the development of allergic reactions, including asthma and peanut allergies. Conversely, there is also evidence that allergic reactions within the gut may contribute to alterations in oral microbiota composition. Here we review the current evidence of the role of the oral microbiota in inflammatory diseases and health complications, as well as its future relevance in improving health and ameliorating allergic disease.

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.

The interplay between oral microbes and immune responses

Oral microbes play a critical role in maintaining oral homeostasis. Microbial dysbiosis promotes disease pathogenesis through several mechanisms. Recent studies have revealed that microbial imbalance and sustained inflammation are involved in disease progression. The adverse interaction triggered by a host immune response to microorganisms can lead to oral and systemic diseases. Here, we reviewed how oral microbes communicate with hosts during the development of local and distant inflammation. Elucidation of these processes may reveal future directions in this field and the potential targets of novel biological therapies for oral and systemic diseases.

Novel antibody assessment method for microbial compositional alteration in the oral cavity

Recently, it has been demonstrated that dysbiosis, an alteration in commensal microflora composition, is intimately involved in the onset of a variety of diseases. It is becoming increasingly evident that the composition of commensal microflora in the oral cavity is closely connected to oral diseases, such as periodontal disease, and systemic diseases, such as inflammatory bowel disease. Next-generation sequencing techniques are used as a method to examine changes in bacterial flora, but additional analytical methods to assess bacterial flora are needed to understand bacterial activity in more detail. In addition, the oral environment is unique because of the role of secretory antibodies contained in saliva in the formation of bacterial flora. The present study aimed to develop a new method for evaluating the compositional change of microbiota using flow cytometry (FCM) with specific antibodies against the bacterial surface antigen, as well as salivary antibodies. Using specific antibodies against Streptococcus mutans, a causative agent of dental caries, and human IgA, bacterial samples from human saliva were analyzed via FCM. The results showed that different profiles could be obtained depending on the oral hygiene status of the subjects. These results suggest that changes in the amount and type of antibodies that bind to oral bacteria may be an indicator for evaluating abnormalities in the oral flora. Therefore, the protocol established in this report could be applied as an evaluation method for alterations in the oral microbiota.

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We aimed to develop a new method for evaluating dysbiosis using flow cytometry.

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We used bacterial surface antigen-specific antibodies and salivary antibodies.

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Different profiles could be obtained depending on oral hygiene status.

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Changes in antibodies bound to oral bacteria may indicate oral flora abnormalities.

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Our method can be used to evaluate alterations in the oral microbiota.

Contribution of Gut Microbiota to Immune Tolerance in Infants

The prevalence of food allergy has increased in recent years, especially among the pediatric population. Differences in the gut microbiota composition between children with FA and healthy children have brought this topic into the spotlight as a possible explanation for the increase in FA. The gut microbiota characteristics are acquired through environmental interactions starting early in life, such as type of delivery during birth and breastfeeding. The microbiota features may be shaped by a plethora of immunomodulatory mechanisms, including a predominant role of Tregs and the transcription factor FOXP3. Additionally, a pivotal role has been given to vitamin A and butyrate, the main anti-inflammatory metabolite. These observations have led to the study and development of therapies oriented to modifying the microbiota and metabolite profiles, such as the use of pre- and probiotics and the determination of their capacity to induce tolerance to allergens that are relevant to FA. To date, evidence supporting these approaches in humans is scarce and inconclusive. Larger cohorts and dose-titration studies are mandatory to evaluate whether the observed changes in gut microbiota composition reflect medical recovery and increased tolerance in pediatric patients with FA. In this article, we discuss the establishment of the microbiota, the immunological mechanisms that regulate the microbiota of children with food allergies, and the evidence in research focused on its regulation as a means to achieve tolerance to food allergens.

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.

Rewiring of Microbiota Networks in Erosive Inflammation of the Stomach and Small Bowel

The development of non-invasive, inexpensive, and effective early diagnosis tests for gastric and small-bowel lesions is an urgent requirement. The introduction of magnetically guided capsule endoscopy (MGCE) has aided examination of the small bowel for diagnoses. However, the distribution of the fecal microbiome in abnormal erosions of the stomach and small bowel remains unclear. Herein, alternations in the fecal microbiome in three groups [normal, small-bowel inflammation, and chronic gastritis (CG)] were analyzed by metagenomics and our well-developed method [individual-specific edge-network analysis (iENA)]. In addition to the dominant microbiota identified by the conventional differential analysis, iENA could recognize novel network biomarkers of microbiome communities, such as the genus Bacteroide in CG and small-bowel inflammation. Combined with differential network analysis, the network-hub microbiota within rewired microbiota networks revealed high-ranked iENA microbiota markers, which were disease specific and had particular pathogenic functions. Our findings illuminate the components of the fecal microbiome and the importance of specific bacteria in CG and small-bowel erosions, and could be employed to develop preventive and non-invasive therapeutic strategies.