Role of the Microbiome in Allergic Disease Development

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.

Effect of Mixed Probiotics on Ovalbumin-Induced Atopic Dermatitis in Juvenile Mice

Atopic dermatitis is one of the most common dermatologic problems, especially in children. Given the ability of symbiotic microorganisms in modulating the immune system, probiotics administration has been studied in previous research in the management of atopic dermatitis. However, there are conflicting results between studies. In this study, we aimed to assess the effectiveness of mixed probiotics as a treatment option for atopic dermatitis induced by ovalbumin. BALB/c juvenile mice were classified and divided into the ovalbumin group, mixed probiotic group (ovalbumin + LK), and control group. Except for the control group, all mice were sensitized with ovalbumin to establish a model of atopic dermatitis. The mixed probiotics were given by gavage for 14 days. Mice body weight, skin lesions, skin inflammation, ovalbumin-specific Ig, the number of Treg and CD103+DC, and the expression level of PD-1/PD-L1 were examined. The results showed that mixed probiotics can improve body weight and alleviate skin symptoms. Mixed probiotics reduced serum Th2 inflammatory factors, eosinophils, mast cell degranulation, mast cell count, and the expression of ovalbumin-specific immunoglobulin E/G1 and increased the anti-inflammatory cytokine interleukin-10, Treg cells, CD103+DC cells, and the expression level of PD-1/PD-L1. These findings suggest that mixed probiotics could be a viable treatment option for atopic dermatitis and provide insight into the underlying mechanisms involved.

Circulating microbiome analysis in patients with perioperative anaphylaxis

Background

Perioperative anaphylaxis is a rare and acute systemic manifestation of drug-induced hypersensitivity reactions that occurs following anesthesia induction; the two main classes of drugs responsible for these reactions being neuromuscular blocking agents (NMBA) and antibiotics. The sensitization mechanisms to the drugs are not precisely known, and few risk factors have been described. A growing body of evidence underlines a link between occurrence of allergy and microbiota composition. However, no data exist on microbiota in perioperative anaphylaxis. The aim of this study was to compare circulating microbiota richness and composition between perioperative anaphylaxis patients and matched controls.

Methods

Circulating 16s rDNA was quantified and sequenced in serum samples from 20 individuals with fully characterized IgE-mediated NMBA-related anaphylaxis and 20 controls matched on sex, age, NMBA received, type of surgery and infectious status. Microbiota composition was analyzed with a published bioinformatic pipeline and links with patients clinical and biological data investigated.

Results

Analysis of microbiota diversity showed that anaphylaxis patients seem to have a richer circulating microbiota than controls, but no major differences of composition could be detected with global diversity indexes. Pairwise comparison showed a difference in relative abundance between patients and controls for Saprospiraceae, Enterobacteriaceae, Veillonellaceae, Escherichia-Shigella, Pseudarcicella, Rhodoferax, and Lewinella. Some taxa were associated with concentrations of mast cell tryptase and specific IgE.

Conclusion

We did not find a global difference in terms of microbiota composition between anaphylaxis patient and controls. However, several taxa were associated with anaphylaxis patients and with their biological data. These findings must be further confirmed in different settings to broaden our understanding of drug anaphylaxis pathophysiology and identify predisposition markers.

Allergic Airway Inflammation Emerges from Gut Inflammation and Leakage in Mouse Model of Asthma

Asthma is an allergic airway inflammatory disease characterized by type 2 immune responses. Growing evidence suggests an association between allergic airways and intestinal diseases. However, the primary site of disease origin and initial mechanisms involved in the development of allergic airway inflammation (AAI) is not yet understood. Therefore, the initial contributing organs and mechanisms involved in the development of AAI are investigated using a mouse model of asthma. This study, without a local allergen challenge into the lungs, demonstrates a significant increase in intestinal inflammation with signature type-2 mediators including IL-4, IL-13, STAT6, eosinophils, and Th2 cells. In addition, gut leakage and mRNA expressions of gut leakage markers significantly increase in the intestine. Moreover, reduced mRNA expressions of tight junction proteins are observed in gut and interestingly, in lung tissues. Furthermore, in lung tissues, an increased pulmonary barrier permeability and IL-4 and IL-13 levels associated with significant increase of lipopolysaccharide-binding protein (LBP-gut leakage marker) and eosinophils are observed. However, with local allergen challenges into the lungs, these mechanisms are further enhanced in both gut and lungs. In conclusion, the primary gut originated inflammatory responses translocates into the lungs to orchestrate AAI in a mouse model of asthma.

The influence of modern living conditions on the human microbiome and potential therapeutic opportunities for allergy prevention

Modern living conditions and the recent surge in global urbanization have transformed the human microbiome. This transformation is believed to be a significant factor in the recent spike of common chronic inflammatory diseases like asthma and allergies worldwide, evident in both developed and developing nations. Immigrants from less developed regions who settle in highly urbanized and affluent areas present an ideal demographic for research. Investigating immigrant populations can yield valuable insights, particularly when studying microbiome changes that occur as individuals transition from areas with low asthma prevalence to regions with a high prevalence of the condition. The application of prebiotics and probiotics as potential treatments for asthma and allergies faces challenges. This is due to the complex interplay of numerous factors that contribute to their aetiology. Exploring the interaction between the human microbiome and potential epigenetic changes in specific populations, such as immigrants adapting to new, urbanized environments, may offer crucial insights. Such research could underscore the role of prebiotics and probiotics in preventing allergic conditions. Recognizing the changes in the human microbiome in the context of a Western/modern environment might be essential in addressing the increasing prevalence of allergic diseases. Persistent research in this domain is pivotal for devising effective interventions such as dietary supplementation with prebiotics and probiotics.

OFFSPRING: A SPRING Follow-Up Study Assessing the Efficacy of Maternal Probiotics and Allergic Disease in the Child

INTRODUCTION

There are a variety of factors that contribute to the development of allergic diseases in children, including environmental exposures during the maternal prenatal period. It has been proposed that probiotic supplementation during pregnancy could be used as a possible preventative measure to target childhood allergic disease.

METHODS

Participants from a previously conducted prospective double-blind randomised control trial of probiotics versus placebo study (Study of PRrobiotics IN Gestation) were sent electronic questionnaires to complete about their child, who are now between 3 and 7 years of age. Demographic data and rates of allergic diseases were compared between the two groups.

RESULTS

One hundred and seven women responded to the questionnaires. Between the two groups, there was no difference in the frequency of allergic diseases, with similar rates of eczema, asthma, and hospital presentations seen.

CONCLUSION

In this follow-up study, infants of mothers who were exposed to probiotics during their pregnancy do not appear to have any paediatric health advantages in terms of allergic diseases.

Altered Gut Microbiota Composition Is Associated with Difficulty in Explicit Emotion Regulation in Young Children

Executive function (EF) consists of explicit emotion regulation (EER) and cognitive control (CC). Childhood EER in particular predicts mental and physical health in adulthood. Identifying factors affecting EER development has implications for lifelong physical and mental health. Gut microbiota (GM) has attracted attention as a potential biomarker for risk of physical and mental problems in adulthood. Furthermore, GM is related to brain function/structure, which plays a crucial role in emotional processing. However, little is known about how GM compositions are associated with the development of emotion regulation in early childhood. Therefore, in this study, we examined 257 children aged 3-4 to investigate links between GM and risk to EF. EF was measured using the Mother-Reported Behavior Rating Inventory of Executive Function-Preschool version. GM composition (alpha/beta diversity and genus abundance) was evaluated using 16S rRNA gene sequencing and compared between EF-risk and non-risk groups. Our results show that children with EER-risk (an index of inhibitory self-control) had a higher abundance of the genera Actinomyces and Sutterella. Although we have not established a direct link between GM and CC risk, our findings indicate that GM of preschoolers is closely associated with emotional processing and that EERrisk children have more inflammation-related bacteria.

Dysbiotic lung microbial communities of neonates from allergic mothers confer neonate responsiveness to suboptimal allergen

In humans and animals, offspring of allergic mothers have increased responsiveness to allergens. This is blocked in mice by maternal supplementation with α-tocopherol (αT). Also, adults and children with allergic asthma have airway microbiome dysbiosis with increased Proteobacteria and may have decreased Bacteroidota. It is not known whether αT alters neonate development of lung microbiome dysbiosis or whether neonate lung dysbiosis modifies development of allergy. To address this, the bronchoalveolar lavage was analyzed by 16S rRNA gene analysis (bacterial microbiome) from pups of allergic and non-allergic mothers with a basal diet or αT-supplemented diet. Before and after allergen challenge, pups of allergic mothers had dysbiosis in lung microbial composition with increased Proteobacteria and decreased Bacteroidota and this was blocked by αT supplementation. We determined whether intratracheal transfer of pup lung dysbiotic microbial communities modifies the development of allergy in recipient pups early in life. Interestingly, transfer of dysbiotic lung microbial communities from neonates of allergic mothers to neonates of non-allergic mothers was sufficient to confer responsiveness to allergen in the recipient pups. In contrast, neonates of allergic mothers were not protected from development of allergy by transfer of donor lung microbial communities from either neonates of non-allergic mothers or neonates of αT-supplemented allergic mothers. These data suggest that the dysbiotic lung microbiota is dominant and sufficient for enhanced neonate responsiveness to allergen. Importantly, infants within the INHANCE cohort with an anti-inflammatory profile of tocopherol isoforms had an altered microbiome composition compared to infants with a pro-inflammatory profile of tocopherol isoforms. These data may inform design of future studies for approaches in the prevention or intervention in asthma and allergic disease early in life.

Knowledge mapping of the links between the microbiota and allergic diseases: A bibliometric analysis (2002-2021)

BACKGROUND

In recent decades, dramatic changes in modern environmental exposures and lifestyles have resulted in a steep rise in the prevalence of allergic diseases such as asthma, allergic rhinitis, atopic dermatitis and food allergies. Evidence is mounting that the microbiota plays a crucial role in allergic disorder development and evolution. Therefore, a better understanding of allergic diseases within the context of the microbiota is urgently needed. This work aimed to comprehensively outline general characteristics, research hotspots, evolution routes, and emerging trends in this area.

METHODS

Relevant publications from January 2002 to December 2021 were obtained from the Web of Science Core Collection on 5 August 2022. Bibliometric and visual analyses were performed using CiteSpace; VOSviewer; an online bibliometric platform; and Microsoft Excel 2019.

RESULTS

In total, 2535 documents met the requirements. The annual number of publications has shown rapid growth in the last two decades. The USA, University of California System, and Isolauri E of the University of Turku were the most productive and influential country, institution, and author, respectively. The Journal of Allergy and Clinical Immunology was the most prolific and most cocited journal. High-frequency keywords included "gut microbiota", "asthma", "atopic dermatitis", "children", and "probiotics". Recent studies have focused on "atopic dermatitis", "skin", "asthma", and "probiotics", according to the cocitation analysis of references. Burst detection analysis of keywords showed that "community", "skin microbiome", "microbiome", "Staphylococcus aureus", and "chain fatty acid" were emerging research frontiers, which currently have ongoing bursts.

CONCLUSION

In the last 20 years, studies of the microbiota in allergic diseases have been flourishing, and the themes have been increasing in depth. These findings provide valuable references on the current research hotspots and gaps and development trends in the link between the microbiota and allergic diseases.

Investigation of nasopharyngeal microbiota in children with asthma and allergic rhinitis comorbidity

Aim: The goal of this study was to compare the nasopharyngeal bacterial microbiota of healthy children with asthma and allergic rhinitis, identify potential microbial dysbiosis in patients. Materials and Methods: The study included a total of 15 patients. There were five patients with asthma, five with allergic rhinitis, and five healthy controls. The upper respiratory tract microbiota were identified using 16S metagenomics analysis of nasal lavage samples. Results: Firmucutes was the most prevalent phylum in the upper respiratory tract microbiota of asthma patients, while Proteobacteria were found in the healthy control and allergic rhinitis groups. Dolosigranulum was identified as the most dominant genus in the upper respiratory tract microbiota of asthma patients. Moraxella was the most prevalent genera in the upper respiratory tract microbiota of the healthy control group. When asthma patients were compared to the control group, the ratio of the Moraxella genus decreased while the ratios of Staphylococcus, Streptococcus, and Corynebacterium species increased. Conclusion: In conclusion, it has not been determined that upper respiratory tract microbiota has a role in determining the pathogenesis of allergic rhinitis and asthma in childhood. The fact that there is a proportional difference between groups’ supports that there may be a possible difference if the entire airway microbiome is studied.

Association between air pollution and the prevalence of allergic rhinitis in Chinese children: A systematic review and meta-analysis

Background: Allergic rhinitis (AR) is a common chronic inflammatory disease with bothersome symptoms. However, the effect of air pollution on the prevalence of AR in children is controversial. Objective: This study aimed to investigate the association between air pollution and the prevalence of AR in Chinese children. Methods: This study, in China, included 160,356 students ages 0-18 years who completed a questionnaire about the accuracy of the International Study of Asthma and Allergies in Childhood (ISAAC). The effect of different air pollutants on the prevalence rate were evaluated by meta-analysis. Also, it evaluated the effect of different air pollutants on the prevalence rate. Results: The differences in the effects of sulfur dioxide (SO₂) exposure (combined odds ratio [OR_combined] 1.03 [95% confidence interval {CI}, 1.01-1.05]; p = 0.010) and nitrogen dioxide (NO₂) exposure (OR_combined 1.11 [95% CI, 1.05-1.18]; p = 0.0006) on the risk of childhood AR was statistically significant. The effect of particulate matter with aerodynamic diameter of <10 μm (PM₁₀) exposure on the risk of childhood AR was statistically significant (OR_combined 1.02 [95% CI, 1.01-1.03]; p < 0.001), the effect of particulate matter with aerodynamic diameter of <2.5 μm (PM_2.5) exposure on the risk of childhood AR was statistically significant (OR_combined 1.15 [95% CI, 1.03-1.29]; p = 0.02), and the effect of ozone exposure on the risk of childhood AR was not statistically significant (OR_combined 0.98 [95% CI, 0.67-1.41]; p = 0.13). Conclusion: NO₂, SO₂, PM_2.5, and PM₁₀ were associated with the prevalence of AR in Chinese children. PM_2.5 had the highest correlation with AR prevalence.

Cyano-Phycocyanin: Mechanisms of Action on Human Skin and Future Perspectives in Medicine

Cyano-phycocyanin is one of the active pigments of the blue-green algae and is usually isolated from the filamentous cyanobacteria Arthrospira platensis Gomont (Spirulina). Due to its multiple physiological functions and non-toxicity, cyano-phycocyanin may be a potential substance for the topical treatment of various skin diseases. Considering that the conventional medicine faces drug resistance, insufficient efficacy and side effects, the plant origin compounds can act as an alternative option. Thus, the aim of this paper was to review the wound healing, antimicrobial, antioxidative, anti-inflammatory, antimelanogenic and anticancer properties and mechanisms of cyano-phycocyanin topical activities on human skin. Moreover, possible applications and biotechnological requirements for pharmaceutical forms of cyano-phycocyanin for the treatment of various skin diseases are discussed in this review.

Lower airway microbiome of children with recurrent wheezing: a clinical cohort study

BACKGROUND

Wheezing is one of the most common respiratory symptoms in childhood especially in infants. In recent years, the incidence of recurrent wheezing is on the rise worldwide. To investigate the lower airway microbiota in patients with recurrent wheezing and provide insights into clinical diagnosis and treatment.

METHODS

This study initially enrolled 45 hospitalised children with recurrent wheezing symptoms awaiting complete fiberoptic bronchoscopy. Of these, 13 children with tracheobronchomalacia were excluded. The final population included 32 participants (group A). The control group comprised 23 children who inhaled a foreign body and were admitted to the hospital for fiberoptic bronchoscopy within 24 hours (group B). Deoxyribonucleic acid (DNA) was extracted from the bronchoalveolar lavage fluid (BALF) and amplified for the 16S ribosomal Ribonucleic Acid (rRNA) gene, and sequencing of the microbiome was performed using the Illumina Nova Seq 6000 system.

RESULTS

There were significant differences in the gestational duration (P=0.0458), mode of delivery (P=0.0261), and allergy status (P=0.0000) between groups A and B, but they had similar richness (P=0.8574). There was also a marked difference in the diversity of flora composition between the two groups (P=0.0095). The three most common phyla of microbiota in the two groups were Proteobacteria, Firmicutes, and Bacteroidetes. Species with notably different phyla included Proteobacteria, Bacteroidota, Fusobacteriota, and Acidobacteriota. There was a significant enrichment in the of Proteobacteria and lower levels of Bacteroidota, Fusobacteriota, and Acidobacteriota in group A compared to that in group B.

CONCLUSIONS

Significant changes occur in the lower airway microbiota during recurrent wheezing in children. The discovery of beneficial airway bacteria may facilitate the prevention and treatment of recurrent wheezing or asthma in children.

Epithelial barrier hypothesis: Effect of the external exposome on the microbiome and epithelial barriers in allergic disease

Environmental exposure plays a major role in the development of allergic diseases. The exposome can be classified into internal (e.g., aging, hormones, and metabolic processes), specific external (e.g., chemical pollutants or lifestyle factors), and general external (e.g., broader socioeconomic and psychological contexts) domains, all of which are interrelated. All the factors we are exposed to, from the moment of conception to death, are part of the external exposome. Several hundreds of thousands of new chemicals have been introduced in modern life without our having a full understanding of their toxic health effects and ways to mitigate these effects. Climate change, air pollution, microplastics, tobacco smoke, changes and loss of biodiversity, alterations in dietary habits, and the microbiome due to modernization, urbanization, and globalization constitute our surrounding environment and external exposome. Some of these factors disrupt the epithelial barriers of the skin and mucosal surfaces, and these disruptions have been linked in the last few decades to the increasing prevalence and severity of allergic and inflammatory diseases such as atopic dermatitis, food allergy, allergic rhinitis, chronic rhinosinusitis, eosinophilic esophagitis, and asthma. The epithelial barrier hypothesis provides a mechanistic explanation of how these factors can explain the rapid increase in allergic and autoimmune diseases. In this review, we discuss factors affecting the planet's health in the context of the 'epithelial barrier hypothesis,' including climate change, pollution, changes and loss of biodiversity, and emphasize the changes in the external exposome in the last few decades and their effects on allergic diseases. In addition, the roles of increased dietary fatty acid consumption and environmental substances (detergents, airborne pollen, ozone, microplastics, nanoparticles, and tobacco) affecting epithelial barriers are discussed. Considering the emerging data from recent studies, we suggest stringent governmental regulations, global policy adjustments, patient education, and the establishment of individualized control measures to mitigate environmental threats and decrease allergic disease.

Food Allergy-Induced Autism-Like Behavior is Associated with Gut Microbiota and Brain mTOR Signaling

Purpose

Food allergy-induced autism-like behavior has been increasing for decades, but the causal drivers of this association are unclear. We sought to test the association of gut microbiota and mammalian/mechanistic target of rapamycin (mTOR) signaling with cow’s milk allergy (CMA)-induced autism pathogenesis.

Methods

Mice were sensitized intragastrically with whey protein containing cholera toxin before sensitization on intraperitoneal injection with whey-containing alum, followed by intragastric allergen challenge to induce experimental CMA. The food allergic immune responses, ASD-like behavioral tests and changes in the mTOR signaling pathway and gut microbial community structure were performed.

Results

CMA mice showed autism-like behavioral abnormalities and several distinct biomarkers. These include increased levels of 5-hydroxymethylcytosine (5-hmC) in the hypothalamus; c-Fos were predominantly located in the region of the lateral orbital prefrontal cortex (PFC), but not ventral; decreased serotonin 1A in amygdala and PFC. CMA mice exhibited a specific microbiota signature characterized by coordinate changes in the abundance of taxa of several bacterial genera, including the Lactobacillus. Interestingly, the changes were accompanied by promoted mTOR signaling in the brain of CMA mice.

Conclusion

We found that disease-associated microbiota and mTOR activation may thus play a pathogenic role in the intestinal, immunological, and psychiatric Autism Spectrum Disorder (ASD)-like symptoms seen in CAM associated autism. However, this is only a preliminary study, and their mechanisms require further investigation.

Strategies to Develop a Suitable Formulation for Inflammatory Skin Disease Treatment

Skin barrier functions, environmental insults, and genetic backgrounds are intricately linked and form the basis of common inflammatory skin disorders, such as atopic dermatitis, psoriasis, and seborrheic dermatitis, which may seriously affect one’s quality of life. Topical therapy is usually the first line of management. It is believed that successful topical treatment requires pharmaceutical formulation from a sufficient dosage to exert therapeutic effects by penetrating the stratum corneum and then diffusing to the target area. However, many factors can affect this process including the physicochemical properties of the active compound, the composition of the formulation base, and the limitations and conditions of the skin barrier, especially in inflammatory skin. This article briefly reviews the available data on these issues and provides opinions on strategies to develop a suitable formulation for inflammatory skin disease treatment.

Dysbiosis revisited: Understanding the role of the oral microbiome in the pathogenesis of gingivitis and periodontitis: A critical assessment

This commentary provides background, historical context, and a critical assessment of the concept that microbial dysbiosis drives the pathogenesis of periodontal diseases. It is long known that periodontal pathogenesis is dependent on tooth-borne microbial biofilms (dental plaque) that trigger host inflammation resulting in periodontal destruction and tooth loss in some patients. Ecological principles governing plaque biofilm development, along with localized host responses, are both rooted in evolution. Interpretation of available evidence suggests that, in most patients, alveolar bone loss results from interactions of a highly diverse commensal microbiota with the host, and not from "overgrowth" of a few "pathobionts" that results in a "dysbiosis." Most previously described dysbiotic chronic diseases, for example, inflammatory bowel diseases and dermatitis, are characterized by decreased microbial diversity (likely due to frank overgrowth of one or a few microbial taxa). Most common forms of periodontitis do not appear to conform to this general principle, and the associated microbiome in fact almost always shows increased bacterial diversity compared with periodontal health. This diversity is driven by interactions of genetic and environmental factors working in concert within specific windows of time. Periodontal pathogenesis is likely the result of "personalized pathology," insofar as each patient likely has a variable constellation of microbes and host risk factors influencing specific tissue sites where disease activity occurs, and during a limited window of time (a tissue-destructive "burst"). The concept of cooperative virulence of higher abundance commensals in periodontal pathogenesis, which does not conform to the model of dysbiosis observed for other diseases, is discussed.

Hygiene hypothesis and autoimmune diseases: A narrative review of clinical evidences and mechanisms

Since the start of the "modern era", characterized by the increase in urbanization, a progressive attention to hygiene and autoimmune conditions has considerably grown. Although these diseases are often multifactorial, it was demonstrated that environment factors such as pollution, diet and lifestyles may play a crucial role together with genetic signature. Our research, based on the newest and most significant literature of this topic, highlights that the progressive depletion of microbes and parasites due to increased socioeconomic improvement, may lead to a derangement of immunoregulatory mechanisms. Moreover, special attention was given to the complex interplay between microbial agents, as gut microbiome, diet and vitamin D supplementation with the aim of identifying promising future therapeutic options. In conclusion, autoimmunity cannot be limited to hygiene-hypothesis, but from the point of view of precision medicine, this theory represents a fundamental element together with the study of genomics, the microbiome and proteomics, in order to understand the complex functioning of the immune system.

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.

Dynamic Interplay Between Microbiota and Mucosal Immunity in Early Shaping of Asthma and its Implication for the COVID-19 Pandemic

The crosstalk between host immunity and the external environment in the mucous membranes of the gastrointestinal and respiratory tracts in bronchial asthma has recently been scrutinized. There is compelling evidence that the microbiota at these sites may play an important role in the pathogenesis of this chronic airway disease. The appearance of bacteria early in life in the gut before dissemination to the airways plays a pivotal role in shaping mucosal immunity. Loss of microbial diversity or dysbiosis can result in aberrant immune-mediated inflammation and mucosal barrier disruption, which coincides clinically with the successive development of the "allergic march" in asthma. Microbial manipulation may be effective in curbing asthma development by indirectly preserving homeostatic epithelial barrier functions. The protective effects and mechanisms of immunity-microbiome crosstalk at mucosal sites require further investigation to identify therapeutic and preventive measures in asthma. This topical review aims to highlight new evidence that compromised epithelial barrier function, which results in deregulated crosstalk between the microbiome and host mucosal immune system, is an important disease mechanism in asthma. In the light of current COVID-19 pandemic, the collective findings on the impact of mucosal microbiota on the suceptibility to SARS-CoV-2 infection and severity of COVID-19 is explored. The possible therapeutic implications to target these abnormalities are further discussed.

Gut Microbiota between Environment and Genetic Background in Familial Mediterranean Fever (FMF)

The gastrointestinal tract hosts the natural reservoir of microbiota since birth. The microbiota includes various bacteria that establish a progressively mutual relationship with the host. Of note, the composition of gut microbiota is rather individual-specific and, normally, depends on both the host genotype and environmental factors. The study of the bacterial profile in the gut demonstrates that dominant and minor phyla are present in the gastrointestinal tract with bacterial density gradually increasing in oro-aboral direction. The cross-talk between bacteria and host within the gut strongly contributes to the host metabolism, to structural and protective functions. Dysbiosis can develop following aging, diseases, inflammatory status, and antibiotic therapy. Growing evidences show a possible link between the microbiota and Familial Mediterranean Fever (FMF), through a shift of the relative abundance in microbial species. To which extent such perturbations of the microbiota are relevant in driving the phenotypic manifestations of FMF with respect to genetic background, remains to be further investigated.