High levels of butyrate and propionate in early life are associated with protection against atopy

A Non-Invasive Neonatal Signature Predicts Later Development of Atopic Diseases

Background: Preterm birth is a major cause of morbidity and mortality in infants and children. Non-invasive methods for screening the neonatal immune status are lacking. Archaea, a prokaryotic life domain, comprise methanogenic species that are part of the neonatal human microbiota and contribute to early immune imprinting. However, they have not yet been characterized in preterm neonates. Objective: To characterize the gut immunological and methanogenic Archaeal (MA) signature in preterm neonates, using the presence or absence of atopic conditions at the age of one year as a clinical endpoint. Methods: Meconium and stool were collected from preterm neonates and used to develop a standardized stool preparation method for the assessment of mediators and cytokines and characterize the qPCR kinetics of gut MA. Analysis addressed the relationship between immunological biomarkers, Archaea abundance, and atopic disease at age one. Results: Immunoglobulin E, tryptase, calprotectin, EDN, cytokines, and MA were detectable in the meconium and later samples. Atopic conditions at age of one year were positively associated with neonatal EDN, IL-1β, IL-10, IL-6, and MA abundance. The latter was negatively associated with neonatal EDN, IL-1β, and IL-6. Conclusions: We report a non-invasive method for establishing a gut immunological and Archaeal signature in preterm neonates, predictive of atopic diseases at the age of one year.

Influence of the early-life gut microbiota on the immune responses to an inhaled allergen

Antibiotics, among the most used medications in children, affect gut microbiome communities and metabolic functions. These changes in microbiota structure can impact host immunity. We hypothesized that early-life microbiome alterations would lead to increased susceptibility to allergy and asthma. To test this, mouse pups between postnatal days 5-9 were orally exposed to water (control) or to therapeutic doses of azithromycin or amoxicillin. Later in life, these mice were sensitized and challenged with a model allergen, house dust mite (HDM), or saline. Mice with early-life azithromycin exposure that were challenged with HDM had increased IgE and IL-13 production by CD4⁺ T cells compared to unexposed mice; early-life amoxicillin exposure led to fewer abnormalities. To test that the microbiota contained the immunological cues to alter IgE and cytokine production after HDM challenge, germ-free mice were gavaged with fecal samples of the antibiotic-perturbed microbiota. Gavage of adult germ-free mice did not result in altered HDM responses, however, their offspring, which acquired the antibiotic-perturbed microbiota at birth showed elevated IgE levels and CD4⁺ cytokines in response to HDM, and altered airway reactivity. These studies indicate that early-life microbiota composition can heighten allergen-driven Th2/Th17 immune pathways and airway responses in an age-dependent manner.

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.

Microbiota in health and diseases

The role of microbiota in health and diseases is being highlighted by numerous studies since its discovery. Depending on the localized regions, microbiota can be classified into gut, oral, respiratory, and skin microbiota. The microbial communities are in symbiosis with the host, contributing to homeostasis and regulating immune function. However, microbiota dysbiosis can lead to dysregulation of bodily functions and diseases including cardiovascular diseases (CVDs), cancers, respiratory diseases, etc. In this review, we discuss the current knowledge of how microbiota links to host health or pathogenesis. We first summarize the research of microbiota in healthy conditions, including the gut-brain axis, colonization resistance and immune modulation. Then, we highlight the pathogenesis of microbiota dysbiosis in disease development and progression, primarily associated with dysregulation of community composition, modulation of host immune response, and induction of chronic inflammation. Finally, we introduce the clinical approaches that utilize microbiota for disease treatment, such as microbiota modulation and fecal microbial transplantation.

Nutrition during Pregnancy and Lactation: Epigenetic Effects on Infants’ Immune System in Food Allergy

Food allergies are an increasing health problem worldwide. They are multifactorial diseases, in which the genome alone does not explain the development of the disease, but a genetic predisposition and various environmental factors contribute to their onset. Environmental factors, in particular nutritional factors, in the early stages of life are recognized as key elements in the etiology of food allergies. There is growing evidence advising that nutrition can affect the risk of developing food allergies through epigenetic mechanisms elicited by the nutritional factors themselves or by modulating the gut microbiota and its functional products. Gut microbiota and postbiotics can in turn influence the risk of food allergy development through epigenetic mechanisms. Epigenetic programming accounts not only for the short-term effects on the individual’s health status, but also for those observed in adulthood. The first thousand days of life represent an important window of susceptibility in which environmental factors, including nutritional ones, can influence the risk of developing allergies through epigenetic mechanisms. From this point of view, it represents an interesting window of opportunity and intervention. This review reports the main nutritional factors that in the early stages of life can influence immune oral tolerance through the modulation of epigenetic mechanisms.

Allergic Rhinitis in Childhood and the New EUFOREA Algorithm

Allergic rhinitis in childhood has been often missed, mistreated and misunderstood. It has significant comorbidities, adverse effects upon quality of life and educational performance and can progress to asthma or worsen control of existing asthma. Accurate diagnosis and effective treatment are important. The new EUFOREA algorithm provides a succinct but wide- ranging guide to management at all levels, based on previous guidelines with updated evidence and has been adjusted and approved by experts worldwide.

Evaluation of Stool Short Chain Fatty Acids Profiles in the First Year of Life With Childhood Atopy-Related Outcomes

Introduction

Short chain fatty acids (SCFAs) are the main intestinal intermediate and end products of metabolism of dietary fibers/polyphenols by the gut microbiota. The aim of this study was to evaluate the biological implication of stool SCFA profiles determined in the first year of life on the clinical presentation of allergic outcomes in childhood.

Methods

From the Growing Up in Singapore Toward healthy Outcomes (GUSTO) cohort, a sub-cohort of 75 participants was recruited. Scheduled questionnaire data was collected for cumulative prevalence of physician-diagnosed eczema, wheezing with the use of nebuliser, and allergen sensitization till the age of 8 years. Stool samples collected at week 3 and months 3, 6 and 12 were quantitated for 9 SCFAs using LC/MS/MS. SCFA data were grouped into lower (below the 25th⁾ and higher (above the 75th percentiles) categories. Generalized Linear Mixed Models was employed to analyse longitudinal association between SCFAs and atopy-related outcomes.

Results

Children with lower stool butyric acid levels (≤25th percentile) over the first 3 time points had higher odds ratio (OR) for wheezing (adjOR = 14.6), eczema (adjOR = 13.2), food sensitization (adjOR = 12.3) and combined outcomes of both wheezing and eczema (adjOR = 22.6) till age 8 years, compared to those with higher levels (≥75 percentile). Additionally, lower longitudinal levels of propionic acid (≤25th percentile) over 4 time points in first year of life was associated with recurrent wheezing (≥2 episodes) till 8 years (adjOR = 7.4) (adj p < 0.05).

Conclusion

Our results suggest that relatively low levels of gut SCFAs in early life are associated with increased susceptibility to atopic-related outcomes in childhood.

Propionic acid regulates immune tolerant properties in B Cells

Interleukin 10 (IL‐10)‐producing B cells (B10 cells) are a canonical cell fraction for regulating other activities of immune cells. Posttranscriptional modification of IL‐10 in B10 cells is not yet fully understood. Short‐chain fatty acids play an important role to regulate the functions of immune cells. This study aims to clarify the role of propionic acid (PA), a short‐chain fatty acid, in regulating the expression of IL‐10 in B10 cells. Blood samples were collected from patients with food allergy (FA) and healthy subjects. Serum and cellular components were prepared with the samples, and analysed by enzyme‐linked immunosorbent assay and flow cytometry, respectively. The results showed that serum PA levels were lower in FA patients. PA concentrations were negatively correlated with serum cytokine Th2 concentrations, specific IgE concentrations in serum and skin prick test results. The peripheral frequency of B10 cells and the production of IL‐10 in B cells were also associated with serum PA concentrations. Activation of B cells by CpG induced the production of IL‐10 and tristetretrprolin (TTP), in which TTP caused the spontaneous decay of IL‐10 mRNA. PA was necessary to stabilize the IL‐10 mRNA in B cells by inducing the production of granzyme B, which resulted in the degradation of the IL‐10 mRNA. Administration of PA attenuated FA response in mice by maintaining homeostasis of B10 cells. In conclusion, PA is needed to stabilize the expression of IL‐10 in B10 cells. PA administration can mitigate experimental FA by maintaining B10 cell functions.

Gut microbiota and allergic diseases in children

The gut microbiota resides in the human gastrointestinal tract, where it plays an important role in maintaining host health. The human gut microbiota is established by the age of 3 years. Studies have revealed that an imbalance in the gut microbiota, termed dysbiosis, occurs due to factors such as cesarean delivery and antibiotic use before the age of 3 years and that dysbiosis is associated with a higher risk of future onset of allergic diseases. Recent advancements in next-generation sequencing methods have revealed the presence of dysbiosis in patients with allergic diseases, which increases attention on the relationship between dysbiosis and the development of allergic diseases. However, there is no unified perspective on the characteristics on dysbiosis or the mechanistic link between dysbiosis and the onset of allergic diseases. Here, we introduce the latest studies on the gut microbiota in children with allergic diseases and present the hypothesis that dysbiosis characterized by fewer butyric acid-producing bacteria leads to fewer regulatory T cells, resulting in allergic disease. Further studies on correcting dysbiosis for the prevention and treatment of allergic diseases are warranted.

Effect of Probiotics on Respiratory Tract Allergic Disease and Gut Microbiota

Allergy is a hypersensitivity reaction triggered by specific cell or antibody-mediated immune mechanisms. Allergies have increased in industrialized countries in recent decades. The rise in allergic respiratory diseases such as allergic rhinitis (AR) and allergic asthma (AA) is a potential threat to public health. Searches were conducted using PubMed, Google Scholar and Medline using the following key terms: allergic rhinitis OR asthma AND probiotics, allergic airway inflammation AND immune disorders, probiotics OR gut microbiota AND allergic disease, probiotics AND inflammatory. Studies from all years were included, specifically those published within the last 10 years. Some review articles and their reference lists were searched to identify related articles. The role of microbiota in respiratory allergic diseases has attracted more and more attention. Pieces of evidence suggested that the development of allergic diseases causes a possible imbalance in the composition of the gut microbiota. Compared to colonized mice, germ-free mice exhibit exaggerated allergic airway responses, suggesting that microbial host interactions play an important role in the development of allergic diseases. Probiotics modulate both the innate and adaptive inflammatory immune responses, often used as dietary supplements to provide health benefits in gastrointestinal disorders. Probiotics may serve as immunomodulators and activators of host defense pathways. Besides, oral probiotics can modulate the immune response in the respiratory system. Recently, studies in humans and animals have demonstrated the role of probiotic in RA and AA. To understand the characterization, microbiota, and the potential role of probiotics intervention of AA/AR, this review provides an overview of clinical features of AA and AR, probiotics for the prevention and treatment of AR, AA, changes in gut microbiota, and their mechanisms of action.

The Immune Mechanisms of Severe Equine Asthma-Current Understanding and What Is Missing

Severe equine asthma is a chronic respiratory disease of adult horses, occurring when genetically susceptible individuals are exposed to environmental aeroallergens. This results in airway inflammation, mucus accumulation and bronchial constriction. Although several studies aimed at evaluating the genetic and immune pathways associated with the disease, the results reported are inconsistent. Furthermore, the complexity and heterogeneity of this disease bears great similarity to what is described for human asthma. Currently available studies identified two chromosome regions (ECA13 and ECA15) and several genes associated with the disease. The inflammatory response appears to be mediated by T helper cells (Th1, Th2, Th17) and neutrophilic inflammation significantly contributes to the persistence of airway inflammatory status. This review evaluates the reported findings pertaining to the genetical and immunological background of severe equine asthma and reflects on their implications in the pathophysiology of the disease whilst discussing further areas of research interest aiming at advancing treatment and prognosis of affected individuals.

Effect of single versus multistrain probiotic in extremely preterm infants: a randomised trial

OBJECTIVE

Evidence indicates that multistrain probiotics benefit preterm infants more than single-strain (SS) probiotics. We assessed the effects of SS versus triple-strain (TS) probiotic supplementation (PS) in extremely preterm (EP) infants.

DESIGN

EP infants (gestational age (GA) <28 weeks) were randomly allocated to TS or SS probiotic, assuring blinding. Reference (REF) group was EP infants in the placebo arm of our previous probiotic trial. PS was commenced with feeds and continued until 37 weeks' corrected GA. Primary outcome was time to full feed (TFF: 150 mL/kg/day). Secondary outcomes included short-chain fatty acids and faecal microbiota collected at T1 (first week) and T2 (after 3 weeks of PS) using 16S ribosomal RNA gene sequencing.

RESULTS

173 EP (SS: 86, TS: 87) neonates with similar GA and birth weight (BW) were randomised. Median TFF was comparable (11 (IQR 8-16) vs 10 (IQR 8-16) days, p=0.92). Faecal propionate (SS, p<0.001, and TS, p=0.0009) and butyrate levels (TS, p=0.029) were significantly raised in T2 versus T1 samples. Secondary clinical outcomes were comparable. At T2, alpha diversity was comparable (p>0.05) between groups, whereas beta-diversity analysis revealed significant differences between PS and REF groups (both p=0.001). Actinobacteria were higher (both p<0.01), and Proteobacteria, Firmicutes and Bacteroidetes were lower in PS versus REF. Gammaproteobacteria, Clostridia and Negativicutes were lower in both PS versus REF.

CONCLUSION

TFF in EP infants was similar between SS and TS probiotics. Both probiotics were effective in reducing dysbiosis (higher bifidobacteria and lower Gammaproteobacteria). Long-term significance of increased propionate and butyrate needs further studies.

TRIAL REGISTRATION NUMBER

ACTRN 12615000940572.

Environment-dependent alterations of immune mediators in urban and rural South African children with atopic dermatitis

BACKGROUND

In order to improve targeted therapeutic approaches for children with atopic dermatitis (AD), novel insights into the molecular mechanisms and environmental exposures that differentially contribute to disease phenotypes are required. We wished to identify AD immunological endotypes in South African children from rural and urban environments.

METHODS

We measured immunological, socio-economic and environmental factors in healthy children (n = 74) and children with AD (n = 78), in rural and urban settings from the same ethno-linguistic AmaXhosa background in South Africa.

RESULTS

Circulating eosinophils, monocytes, TARC, MCP-4, IL-16 and allergen-specific IgE levels were elevated, while IL-17A and IL-23 levels were reduced, in children with AD regardless of their location. Independent of AD, children living in a rural environment had the highest levels of TNFα, TNFβ, IL-1α, IL-6, IL-8, IL-21, MCP-1, MIP-1α, MIP-1β, MDC, sICAM1, sVCAM1, VEGFA, VEGFD and Tie2, suggesting a generalized microinflammation or a pattern of trained immunity without any specific T_H polarization. In contrast, IL-15, IL-22, Flt1, PIGF and βFGF were highest in urban children. Rural healthy children had the lowest levels of food allergen-specific IgG4. Early life nutritional factors, medications, animal exposures, indoor environment, sunlight exposure, household size, household income and parental education levels were associated with differences in circulating cytokine levels.

CONCLUSIONS

This study highlights the immunological impact of environmental exposures and socio-economic status in the manifestation of immune endotypes in children with AD living in urban and rural areas, which are important in selecting appropriately matched immunological therapies for treatment of AD.

Lower caprylate and acetate levels in the breast milk is associated with atopic dermatitis in infancy

BACKGROUND

Atopic dermatitis (AD) occurs in exclusively breastfed infants. As fatty acids have some immunomodulatory effect, we aimed to investigate the influence of fatty acid compositions in breast milk (BM) on the development of AD in exclusively breastfed infants.

METHODS

We enrolled two- to four-month-old exclusively breastfed infants. The objective SCORing Atopic Dermatitis (objSCORAD) was evaluated. The lipid layer of BM was analyzed by gas chromatography for fatty acid levels. Medical charts were reviewed.

RESULTS

Forty-seven AD infants and 47 healthy controls were enrolled. The objSCORAD was 20.5 ± 1.7 (shown as mean ± SEM) in the AD group. The age, sex, parental atopy history, and nutrient intake of mothers were not significantly different between two groups. The palmitate and monounsaturated fatty acid (MUFA) levels in BM positively correlated with objSCORAD, while caprylate, acetate, and short-chain fatty acid (SCFA) levels negatively correlated with objSCORAD (p = .031, .019, .039, .013, .022, respectively). However, the butyrate levels in BM were not significantly different. The caprylate and acetate levels in BM were significantly associated with the presence of infantile AD (p = .021 and .015, respectively) after adjusting for age, sex, parental allergy history, MUFA, palmitate, and SCFA levels in BM. ObjSCORAD in infancy was significantly associated with persistent AD (p = .026) after adjusting for age, sex, parental atopy history, caprylate, palmitate, MUFA, acetate, and SCFA levels in BM.

CONCLUSION

Caprylate and acetate levels in BM for exclusively breastfed infants were negatively associated with objSCORAD. Lower caprylate and acetate in BM might be the risk factors for infantile AD, while butyrate in BM was not associated with infantile AD.

Early intervention and prevention of allergic diseases

Food allergy (FA) is now one of the most common chronic diseases of childhood often lasting throughout life and leading to significant worldwide healthcare burden. The precise mechanisms responsible for the development of this inflammatory condition are largely unknown; however, a multifactorial aetiology involving both environmental and genetic contributions is well accepted. A precise understanding of the pathogenesis of FA is an essential first step to developing comprehensive prevention strategies that could mitigate this epidemic. As it is frequently preceded by atopic dermatitis and can be prevented by early antigen introduction, the development of FA is likely facilitated by the improper initial presentation of antigen to the developing immune system. Primary oral exposure of antigens allowing for presentation via a well-developed mucosal immune system, rather than through a disrupted skin epidermal barrier, is essential to prevent FA. In this review, we present the data supporting the necessity of (1) an intact epidermal barrier to prevent epicutaneous antigen presentation, (2) the presence of specific commensal bacteria to maintain an intact mucosal immune system and (3) maternal/infant diet diversity, including vitamins and minerals, and appropriately timed allergenic food introduction to prevent FA.

The effect of short-chain fatty acids on M2 macrophages polarization in vitro and in vivo

Alternatively activated macrophages (M2 polarization) play an important role in asthma. Short-chain fatty acids (SCFAs) possessed immune-regulatory functions, but their effects on M2 polarization of alveolar macrophages and its underlying mechanisms are still unclear. In our study, murine alveolar macrophage MH-S cell line and human monocyte-derived macrophages were used to polarize to M2 subset with interleukin-4 (IL-4) treatment. The underlying mechanisms involved were investigated using molecule inhibitors/agonists. In vivo, female C57BL/6 mice were divided into five groups: CON group, ovalbumin (OVA) asthma group, OVA+Acetate group, OVA+Butyrate group, and OVA+Propionate group. Mice were fed with or without SCFAs (Acetate, Butyrate, Propionate) in drinking water for 20 days before developing OVA-induced asthma model. In MH-S, SCFAs inhibited IL-4-incuced protein or mRNA expressions of M2-associated genes in a dose-dependent manner. G-protein-coupled receptor 43 (GPR43) agonist 4-CMTB and histone deacetylase (HDAC) inhibitor (trichostatin A, TSA), but not GPR41 agonist AR420626 could inhibit the protein or mRNA expressions M2-associated genes. 4-CMTB, but not TSA, had no synergistic role in the inhibitory effect of SCFAs on M2 polarization. In vivo study indicated Butyrate and Propionate, but not Acetate, attenuated OVA-induced M2 polarization in the lung and airway inflammation. We also found the inhibitory effect of SCFAs on M2 polarization in human-derived macrophages. Therefore, SCFAs inhibited M2 polarization in MH-S likely through GPR43 activation and/or HDAC inhibition. Butyrate and Propionate but not Acetate could inhibit M2 polarization and airway inflammation in asthma model. SCFAs also abrogated M2 polarization in human-derived macrophages.

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.

Possible role of gut microbes and host's immune response in gut-lung homeostasis

The vast diversity of microbial communities reside in various locations of the human body, and they are collectively named as the 'Human Microbiota.' The majority of those microbes are found in the gastrointestinal and respiratory tracts. The microorganisms present in the gastrointestinal and the respiratory tracts are called the gut microbiota and the airway microbiota, respectively. These microbial communities are known to affect both the metabolic functions and the immune responses of the host. Among multiple factors determining the composition of gut microbiota, diet has played a pivotal role. The gut microbes possess enzymatic machinery for assimilating dietary fibers and releasing different metabolites, primarily short-chain fatty acids (SCFAs). The SCFAs modulate the immune responses of not only the gut but other distal mucosal sites as well, such as the lungs. Dysbiosis in normal gut flora is one of the factors involved in the development of asthma and other respiratory disorders. Of note, several human and murine studies have indicated significant cross-talk between gut microbiota and lung immunity, known as the gut-lung axis. Here, in this review, we summarize the recent state of the field concerning the effect of dietary metabolites, particularly SCFAs, on the "gut-lung axis" as well as discuss its impact on lung health. Moreover, we have highlighted the role of the "gut-lung axis" in SARS-CoV-2 mediated inflammation. Also, to analyze the global research progress on the gut-lung axis and to identify the knowledge gap in this field, we have also utilized the bibliographic tools Dimension database and VOS viewer analysis software. Through network mapping and visualization analysis, we can predict the present research trend and the possibility to explore new directions.

The maternal diet index in pregnancy is associated with offspring allergic diseases: the Healthy Start study

BACKGROUND

A systematic review showed limited associations between pregnancy diet and offspring allergy. We developed a maternal diet index during pregnancy that was associated with offspring allergy outcomes.

METHODS

Data came from Healthy Start, a Colorado pre-birth cohort of mother/offspring dyads. Food propensity questionnaires were completed during pregnancy. Offspring allergic rhinitis, atopic dermatitis, asthma, wheeze, and food allergy diagnosis up to age four were verified from electronic medical records. Data were randomized into test and replication sets. The index included the weighted combination of variables that best predicted a combined outcome of any allergy in the test set. Index utility was verified in the replication set. Separate adjusted and unadjusted logistic models estimated associations between the index and each offspring allergy diagnosis in the full sample.

RESULTS

The index included weighted measures of intake of vegetables, yogurt, fried potatoes, rice/grains, red meats, pure fruit juice, and cold cereals. Vegetables and yogurt were associated with the prevention of any allergy, while other components were associated with increased disease. In adjusted models, a one-unit increase in the index was significantly associated with reduced odds of offspring allergic rhinitis (odds ratio (CI) 0.82 [0.72-0.94]), atopic dermatitis (0.77 [0.69-0.86]), asthma (0.84 [0.74-0.96]), and wheeze (0.80 [0.71-0.90]), but not food allergy (0.84 [0.66-1.08]).

CONCLUSIONS

This is the first study that has shown associations between an index of maternal dietary intake during pregnancy and multiple offspring allergic diseases. The results give hope for prevention of allergic diseases in utero.

Disordered development of gut microbiome interferes with the establishment of the gut ecosystem during early childhood with atopic dermatitis

The gut microbiome influences the development of allergic diseases during early childhood. However, there is a lack of comprehensive understanding of microbiome-host crosstalk. Here, we analyzed the influence of gut microbiome dynamics in early childhood on atopic dermatitis (AD) and the potential interactions between host and microbiome that control this homeostasis. We analyzed the gut microbiome in 346 fecal samples (6-36 months; 112 non-AD, 110 mild AD, and 124 moderate to severe AD) from the Longitudinal Cohort for Childhood Origin of Asthma and Allergic Disease birth cohort. The microbiome-host interactions were analyzed in animal and in vitro cell assays. Although the gut microbiome maturated with age in both AD and non-AD groups, its development was disordered in the AD group. Disordered colonization of short-chain fatty acids (SCFA) producers along with age led to abnormal SCFA production and increased IgE levels. A butyrate deficiency and downregulation of GPR109A and PPAR-γ genes were detected in AD-induced mice. Insufficient butyrate decreases the oxygen consumption rate of host cells, which can release oxygen to the gut and perturb the gut microbiome. The disordered gut microbiome development could aggravate balanced microbiome-host interactions, including immune responses during early childhood with AD.

Environmental Influences and Allergic Diseases in the Asia-Pacific Region: What Will Happen in Next 30 Years?

Asia-Pacific is a populous region with remarkable variations in socioeconomic development and environmental exposure among countries. The prevalence rates of asthma and allergic rhinitis appear to have recently reached a plateau in Western countries, whereas they are still increasing in many Asian countries. Given the large population in Asia, even a slight increase in the prevalence rate will translate into an overwhelming number of patients. To reduce the magnitude of the increase in allergic diseases in next few decades in Asia, we must understand the potential factors leading to the occurrence of these disorders and the development of potential preventive strategies. The etiology of allergic disorders is likely due to complex interactions among genetic, epigenetic, and environmental factors for the manifestations of inappropriate immune responses. As urbanization and industrialization inevitably progress in Asia, there is an urgent need to curtail the upcoming waves of the allergy epidemic. Potentially modifiable risk exposure, such as air pollution, should be minimized through timely implementation of effective legislations. Meanwhile, re-introduction of protective factors that were once part of the traditional farming lifestyle might give new insight into primary prevention of allergy.

A New Formulation of Probiotics Attenuates Calcipotriol-Induced Dermatitis by Inducing Regulatory Dendritic Cells

Atopic dermatitis (AD) is a recurrent chronic inflammatory skin disease affecting up to 30% of the children population, and immuno-regulatory therapy that could modify the course of disease is urgently needed. Probiotics have demonstrated therapeutic effects on AD and could potentially regulate the disease process. However, the efficacy of probiotics for AD is inconsistent among different studies, which is mainly due to the elusive mechanism and different species and (or) strains used. In this study, we designed a mixture of five strains of probiotics (named IW5) and analyzed the effect and mechanism of IW5 on calcipotriol (MC903)-induced AD-like dermatitis. We found that IW5 significantly alleviated skin inflammation of the MC903-induced AD in mice. Administration with IW5 induced increased production of regulatory T cells and regulatory dendritic cells (DCregs) in the mesenteric lymph nodes. We also found that the diversity of the gut microbiota in the mice with MC903-induced dermatitis was increased after IW5 administration, and the level of butyrate in the gut was elevated. In cell culture, butyrate induced the production of DCregs. Our study revealed the therapeutic effects of a newly designed probiotics mixture and uncovered a possible mechanism, providing a foundation for future clinical studies.

Microbiome Research and Multi-Omics Integration for Personalized Medicine in Asthma

Asthma is a multifactorial inflammatory disorder of the respiratory system characterized by high diversity in clinical manifestations, underlying pathological mechanisms and response to treatment. It is generally established that human microbiota plays an essential role in shaping a healthy immune response, while its perturbation can cause chronic inflammation related to a wide range of diseases, including asthma. Systems biology approaches encompassing microbiome analysis can offer valuable platforms towards a global understanding of asthma complexity and improving patients' classification, status monitoring and therapeutic choices. In the present review, we summarize recent studies exploring the contribution of microbiota dysbiosis to asthma pathogenesis and heterogeneity in the context of asthma phenotypes-endotypes and administered medication. We subsequently focus on emerging efforts to gain deeper insights into microbiota-host interactions driving asthma complexity by integrating microbiome and host multi-omics data. One of the most prominent achievements of these research efforts is the association of refractory neutrophilic asthma with certain microbial signatures, including predominant pathogenic bacterial taxa (such as Proteobacteria phyla, Gammaproteobacteria class, especially species from Haemophilus and Moraxella genera). Overall, despite existing challenges, large-scale multi-omics endeavors may provide promising biomarkers and therapeutic targets for future development of novel microbe-based personalized strategies for diagnosis, prevention and/or treatment of uncontrollable asthma.

Allergic diseases in infancy: I - Epidemiology and current interpretation

Objective

Among non-communicable diseases, the prevalence of allergic diseases has increased significantly in the new millennium. The increase of allergic diseases is linked to the changing environment of infants.

Methods

This narrative review summarizes the discussions and conclusions from the 8^th Human Milk Workshop. Information from the fields of pediatrics, epidemiology, biology, microbiology, and immunology are summarized to establish a framework describing potential avenues for the prevention of allergic diseases in the future.

Results

Several environmental circumstances are linked to the development of allergic diseases. While cesarean section is increasing the risk of allergies, early childhood exposure to a farm environment has a protective effect. From their analysis, nutritive and non-nutritive factors influencing the allergy risk in later life have been identified. The effect of breastfeeding on food allergy development is non-univocal. Human milk components including immunoglobulins, cytokines, and prebiotics have been indicated as important for allergy prevention.

Conclusion

Many factors linked to the western lifestyle have been associated with the development of allergic diseases. This suggests several theories that may serve as a basis for new protective interventions. While it is indubitable that mother's milk protects from infectious diseases, its role in the prevention of allergic diseases is to be elucidated.

Dangerous liaisons: Bacteria, antimicrobial therapies, and allergic diseases

Microbiota composition and associated metabolic activities are essential for the education and development of a healthy immune system. Microbial dysbiosis, caused by risk factors such as diet, birth mode, or early infant antimicrobial therapy, is associated with the inception of allergic diseases. In turn, allergic diseases increase the risk for irrational use of antimicrobial therapy. Microbial therapies, such as probiotics, have been studied in the prevention and treatment of allergic diseases, but evidence remains limited due to studies with high heterogeneity, strain-dependent effectiveness, and variable outcome measures. In this review, we sketch the relation of microbiota with allergic diseases, the overuse and rationale for the use of antimicrobial agents in allergic diseases, and current knowledge concerning the use of bacterial products in allergic diseases. We urgently recommend 1) limiting antibiotic therapy in pregnancy and early childhood as a method contributing to the reduction of the allergy epidemic in children and 2) restricting antibiotic therapy in exacerbations and chronic treatment of allergic diseases, mainly concerning asthma and atopic dermatitis. Future research should be aimed at antibiotic stewardship implementation strategies and biomarker-guided therapy, discerning those patients that might benefit from antibiotic therapy.

Role of the gut-skin axis in IgE-mediated food allergy and atopic diseases

PURPOSE OF REVIEW

In recent years, landmark clinical trials investigating the role of early oral exposure to food antigens for food allergy (FA) prevention have highlighted the importance of immunoregulatory pathways in the 'gut-skin axis'. This review highlights recent literature on the mechanisms of the immune system and microbiome involved in the gut-skin axis, contributing to the development of atopic dermatitis (AD), FA, allergic rhinitis (AR) and asthma. Therapeutic interventions harnessing the gut-skin axis are also discussed.

RECENT FINDINGS

Epicutaneous sensitization in the presence of AD is capable of inducing Th2 allergic inflammation in the intestinal tract and lower respiratory airways, predisposing one to the development of AR and asthma. Probiotics have demonstrated positive effects in preventing and treating AD, though there is no evident relationship of its beneficial effects on other allergic diseases. Prophylactic skin emollients use has not shown consistent protection against AD, whereas there is some evidence for the role of dietary changes in alleviating AD and airway inflammation. More randomized controlled trials are needed to clarify the potential of epicutaneous immunotherapy as a therapeutic strategy for patients with FA.

SUMMARY

The growing understanding of the gut-skin interactions on allergic disease pathogenesis presents novel avenues for therapeutic interventions which target modulation of the gut and/or skin.

Advances and highlights in allergic rhinitis

Allergic rhinitis (AR) is a growing public health, medical and economic problem worldwide. The current review describes the major discoveries related to AR during the past 2 years, including risk factors for the prevalence of AR, the corresponding diagnostic strategy, precise underlying immunological mechanisms, and efficient therapies for AR during the ongoing global "coronavirus disease 2019" (COVID-19) pandemic. The review further attempts to highlight future research perspectives. Increasing evidence suggests that environmental exposures, climate changes, and lifestyle are important risk factors for AR. Consequently, detailed investigation of the exposome and the connection between environmental exposures and health in the future should provide better risk profiles instead of single predictors, and also help mitigate adverse health outcomes in allergic diseases. Although patients with dual AR, a newly defined AR phenotype, display perennial and seasonal allergens-related nasal symptoms, they are only allergic to seasonal allergens, indicating the importance of measuring inflammation at the local sites. Herein, we suggest that a combination of precise diagnosis in local sites and traditional diagnostic methods may enhance the precision medicine-based approach for management of AR; however, this awaits further investigations. Apart from traditional treatments, social distancing, washing hands, and disinfection are also required to better manage AR patients in the ongoing global COVID-19 pandemic. Despite recent advances in understanding the immune mechanisms underlying the effects of allergen immunotherapy (AIT), further understanding changes of cell profiles after AIT and accurately evaluate the efficacy of AIT are required.

Adjunctive Probiotics Alleviates Asthmatic Symptoms via Modulating the Gut Microbiome and Serum Metabolome

Asthma is a multifactorial disorder, and microbial dysbiosis enhances lung inflammation and asthma-related symptoms. Probiotics have shown anti-inflammatory effects and could regulate the gut-lung axis. Thus, a 3-month randomized, double-blind, and placebo-controlled human trial was performed to investigate the adjunctive efficacy of probiotics in managing asthma. Fifty-five asthmatic patients were randomly assigned to a probiotic group (n = 29; received Bifidobacterium lactis Probio-M8 powder and Symbicort Turbuhaler) and a placebo group (n = 26; received placebo and Symbicort Turbuhaler), and all 55 subjects provided details of their clinical history and demographic data. However, only 31 patients donated a complete set of fecal and blood samples at all three time points for further analysis. Compared with those of the placebo group, co-administering Probio-M8 with Symbicort Turbuhaler significantly decreased the fractional exhaled nitric oxide level at day 30 (P = 0.049) and improved the asthma control test score at the end of the intervention (P = 0.023). More importantly, the level of alveolar nitric oxide concentration decreased significantly among the probiotic receivers at day 30 (P = 0.038), and the symptom relief effect was even more obvious at day 90 (P = 0.001). Probiotic co-administration increased the resilience of the gut microbiome, which was reflected by only minor fluctuations in the gut microbiome diversity (P > 0.05, probiotic receivers; P < 0.05, placebo receivers). Additionally, the probiotic receivers showed significantly changes in some species-level genome bins (SGBs), namely, increases in potentially beneficial species Bifidobacterium animalis, Bifidobacterium longum, and Prevotella sp. CAG and decreases in Parabacteroides distasonis and Clostridiales bacterium (P < 0.05). Compared with that of the placebo group, the gut metabolic potential of probiotic receivers exhibited increased levels of predicted microbial bioactive metabolites (linoleoyl ethanolamide, adrenergic acid, erythronic acid) and serum metabolites (5-dodecenoic acid, tryptophan, sphingomyelin) during/after intervention. Collectively, our results suggested that co-administering Probio-M8 synergized with conventional therapy to alleviate diseases associated with the gut-lung axis, like asthma, possibly via activating multiple anti-inflammatory pathways. IMPORTANCE The human gut microbiota has a potential effect on the pathogenesis of asthma and is closely related to the disease phenotype. Our trial has demonstrated that co-administering Probio-M8 synergized with conventional therapy to alleviate asthma symptoms. The findings of the present study provide new insights into the pathogenesis and treatment of asthma, mechanisms of novel therapeutic strategies, and application of probiotics-based therapy.

Childhood asthma- pathogenesis and phenotypes

In the pathogenesis of asthma in children there is a pivotal role for a type 2 inflammatory response to early life exposures or events. Interactions between infections, atopy, genetic susceptibility, and environmental exposures (such as farmyard environment, air pollution, tobacco smoke exposure) influence the development of wheezing illness and the risk for progression to asthma. The immune system, lung function and the microbiome in gut and airways develop in parallel and dysbiosis of the microbiome may be a critical factor in asthma development. Increased infant weight gain and preterm birth are other risk factors for development of asthma and reduced lung function. The complex interplay between these factors explains the heterogeneity of asthma in children. Subgroups of patients can be identified as phenotypes based on clinical parameters, or endotypes, based on a specific pathophysiological mechanism. Paediatric asthma phenotypes and endotypes may ultimately help to improve diagnosis of asthma, prediction of asthma development and treatment of individual children, based on clinical, temporal, developmental or inflammatory characteristics. Unbiased, data-driven clustering, using a multidimensional or systems biology approach may be needed to better define phenotypes. The present knowledge on inflammatory phenotypes of childhood asthma has now been successfully applied in the treatment with biologicals of children with severe therapy resistant asthma, and it is to be expected that more personalized treatment options may become available.

Building Robust Assemblages of Bacteria in the Human Gut in Early Life

The neonatal body provides a range of potential habitats, such as the gut, for microbes. These sites eventually harbor microbial communities (microbiotas). A "complete" (adult) gut microbiota is not acquired by the neonate immediately after birth. Rather, the exclusive, milk-based nutrition of the infant encourages the assemblage of a gut microbiota of low diversity, usually dominated by bifidobacterial species. The maternal fecal microbiota is an important source of bacterial species that colonize the gut of infants, at least in the short-term. However, development of the microbiota is influenced by the use of human milk (breast feeding), infant formula, preterm delivery of infants, caesarean delivery, antibiotic administration, family details and other environmental factors. Following the introduction of weaning (complementary) foods, the gut microbiota develops in complexity due to the availability of a diversity of plant glycans in fruits and vegetables. These glycans provide growth substrates for the bacterial families (such as members of the Ruminococcaceae and Lachnospiraceae) that, in due course, will dominate the gut microbiota of the adult. Although current data are often fragmentary and observational, it can be concluded that the nutrition that a child receives in early life is likely to impinge not only on the development of the microbiota at that time but also on the subsequent lifelong, functional relationships between the microbiota and the human host. The purpose of this review, therefore, is to discuss the importance of promoting the assemblage of functionally robust gut microbiotas at appropriate times in early life.

Early-Life Respiratory Infections in Infants with Cow's Milk Allergy: An Expert Opinion on the Available Evidence and Recommendations for Future Research

Acute respiratory infections are a common cause of morbidity in infants and young children. This high rate of respiratory infections in early life has a major impact on healthcare resources and antibiotic use, with the associated risk of increasing antibiotic resistance, changes in intestinal microbiota composition and activity and, consequently, on the future health of children. An international group of clinicians and researchers working in infant nutrition and cow's milk allergy (CMA) met to review the available evidence on the prevalence of infections in healthy infants and in those with allergies, particularly CMA; the factors that influence susceptibility to infection in early life; links between infant feeding, CMA and infection risk; and potential strategies to modulate the gut microbiota and infection outcomes. The increased susceptibility of infants with CMA to infections, and the reported potential benefits with prebiotics, probiotics and synbiotics with regard to improving infection outcomes and reducing antibiotic usage in infants with CMA, makes this a clinically important issue that merits further research.

Pharmacological Modulation of Immune Responses by Nutritional Components

The incidence of noncommunicable diseases (NCDs) has increased over the last few decades, and one of the major contributors to this is lifestyle, especially diet. High intake of saturated fatty acids and low intake of dietary fiber is linked to an increase in NCDs. Conversely, a low intake of saturated fatty acids and a high intake of dietary fiber seem to have a protective effect on general health. Several mechanisms have been identified that underlie this phenomenon. In this review, we focus on pharmacological receptors, including the aryl hydrocarbon receptor, binding partners of the retinoid X receptor, G-coupled protein receptors, and toll-like receptors, which can be activated by nutritional components and their metabolites. Depending on the nutritional component and the receptors involved, both proinflammatory and anti-inflammatory effects occur, leading to an altered immune response. These insights may provide opportunities for the prevention and treatment of NCDs and their inherent (sub)chronic inflammation. SIGNIFICANCE STATEMENT: This review summarizes the reported effects of nutritional components and their metabolites on the immune system through manipulation of specific (pharmacological) receptors, including the aryl hydrocarbon receptor, binding partners of the retinoid X receptor, G-coupled protein receptors, and toll-like receptors. Nutritional components, such as vitamins, fibers, and unsaturated fatty acids are able to resolve inflammation, whereas saturated fatty acids tend to exhibit proinflammatory effects. This may aid decision makers and scientists in developing strategies to decrease the incidence of noncommunicable diseases.

A Systematic Review of Metabolic Alterations Underlying IgE-Mediated Food Allergy in Children

SCOPE

Immunoglobulin E-mediated food allergies (IgE-FA) are characterized by an ever-increasing prevalence, currently reaching up to 10.4% of children in the European Union. Metabolomics has the potential to provide a deeper understanding of the pathogenic mechanisms behind IgE-FA.

METHODS AND RESULTS

In this work, literature is systematically searched using Web of Science, PubMed, Scopus, and Embase, from January 2010 until May 2021, including human and animal metabolomic studies on multiple biofluids (urine, blood, feces). In total, 15 studies on IgE-FA are retained and a dataset of 277 potential biomarkers is compiled for in-depth pathway mapping. Decreased indoleamine 2,3-dioxygenase-1 (IDO- 1) activity is hypothesized due to altered plasma levels of tryptophan and its metabolites in IgE-FA children. In feces of children prior to IgE-FA, aberrant metabolization of sphingolipids and histidine is noted. Decreased fecal levels of (branched) short chain fatty acids ((B)SCFAs) compel a shift towards aerobic glycolysis and suggest dysbiosis, associated with an immune system shift towards T-helper 2 (Th2) responses. During animal anaphylaxis, a similar switch towards glycolysis is observed, combined with increased ketogenic pathways. Additionally, altered histidine, purine, pyrimidine, and lipid pathways are observed.

CONCLUSION

To conclude, this work confirms the unprecedented opportunities of metabolomics and supports the in-depth pathophysiological qualification in the quest towards improved diagnostic and prognostic biomarkers for IgE-FA.

Dietary Fibre Intake in Relation to Asthma, Rhinitis and Lung Function Impairment-A Systematic Review of Observational Studies

A high intake of dietary fibre has been associated with a reduced risk of several chronic diseases. This study aimed to review the current evidence on dietary fibre in relation to asthma, rhinitis and lung function impairment. Electronic databases were searched in June 2021 for studies on the association between dietary fibre and asthma, rhinitis, chronic obstructive pulmonary disease (COPD) and lung function. Observational studies with cross-sectional, case–control or prospective designs were included. Studies on animals, case studies and intervention studies were excluded. The quality of the evidence from individual studies was evaluated using the RoB-NObs tool. The World Cancer Research Fund criteria were used to grade the strength of the evidence. Twenty studies were included in this systematic review, of which ten were cohort studies, eight cross-sectional and two case–control studies. Fibre intake during pregnancy or childhood was examined in three studies, while seventeen studies examined the intake during adulthood. There was probable evidence for an inverse association between dietary fibre and COPD and suggestive evidence for a positive association with lung function. However, the evidence regarding asthma and rhinitis was limited and inconsistent. Further research is needed on dietary fibre intake and asthma, rhinitis and lung function among adults and children.

Short-Chain Fatty Acids Calibrate RARα Activity Regulating Food Sensitization

Gut-microbiota dysbiosis links to allergic diseases. The mechanism of the exacerbation of food allergy caused by gut-microbiota dysbiosis remains unknown. Regulation of retinoic acid receptor alpha (RARα) signaling is critical for gut immune homeostasis. Here we clarified that RARα in dendritic cells (DCs) promotes Th2 cell differentiation. Antibiotics treatment stimulates retinoic acid signaling in mucosal DCs. We found microbiota metabolites short-chain fatty acids (SCFAs) maintain IGF-1 levels in serum and mesenteric lymph nodes. The IGF-1/Akt pathway is essential for regulating the transcription of genes targeted by RARα. And RARα in DCs affects type I interferon (IFN-I) responses through regulating transcription of IFN-α. Our study identifies SCFAs crosstalk with RARα in dendritic cells as a critical modulator that plays a core role in promoting Th2 cells differentiation at a state of modified/disturbed microbiome.

Inverse associations between food diversity in the second year of life and allergic diseases

BACKGROUND

The influence of diet in early childhood on later allergic diseases is currently a highly debated research topic. We and others have suggested that an increased diet diversity in the first year of life has a protective effect on the development of allergic diseases.

OBJECTIVE

This follow-up study aimed to investigate associations between diet in the second year of life and later allergic diseases.

METHODS

A total of 1014 children from rural areas in 5 European countries (the Protection against Allergy: Study in Rural Environments or PASTURE birth cohort) were included. Information on feeding practices in their second year of life and allergic diseases were collected up to age 6 years. Multivariate logistic regressions were performed with different models considering reverse causality, such as excluding children with a positive sensitization to egg and those with a positive sensitization to cow's milk at the age of 1 year.

RESULTS

An increased food diversity score during the second year of life was negatively associated with the development of asthma. Consumption of dairy products and eggs in the second year of life found an inverse association with reported allergic outcomes. Consumption of butter was strongly associated with protection against asthma and food sensitization. Egg was inversely associated with atopic dermatitis (odds ratio [OR], 0.17; 95% confidence interval [CI], 0.04-0.77). Yogurt and cow's milk were inversely associated with food allergy (OR for yogurt, 0.05; 95% CI, 0.01-0.55; OR for cow's milk, 0.31; 95% CI, 0.11-0.89).

CONCLUSION

Increased food diversity in the second year of life is inversely associated with the development of asthma, and consumption of dairy products might have a protective effect on allergic diseases.

Nurturing the Early Life Gut Microbiome and Immune Maturation for Long Term Health

Early life is characterized by developmental milestones such as holding up the head, turning over, sitting up and walking that are typically achieved sequentially in specific time windows. Similarly, the early gut microbiome maturation can be characterized by specific temporal microorganism acquisition, colonization and selection with differential functional features over time. This orchestrated microbial sequence occurs from birth during the first years of age before the microbiome reaches an adult-like composition and function between 3 and 5 years of age. Increasingly, these different steps of microbiome development are recognized as crucial windows of opportunity for long term health, primarily linked to appropriate immune and metabolic development. For instance, microbiome disruptors such as preterm and Cesarean-section birth, malnutrition and antibiotic use are associated with increased risk to negatively affect long-term immune and metabolic health. Different age discriminant microbiome taxa and functionalities are used to describe age-appropriate microbiome development, and advanced modelling techniques enable an understanding and visualization of an optimal microbiome maturation trajectory. Specific microbiome features can be related to later health conditions, however, whether such features have a causal relationship is the topic of intense research. Early life nutrition is an important microbiome modulator, and 'Mother Nature' provides the model with breast milk as the sole source of nutrition for the early postnatal period, while dietary choices during the prenatal and weaning period are to a large extent guided by tradition and culture. Increasing evidence suggests prenatal maternal diet and infant and child nutrition impact the infant microbiome trajectory and immune competence development. The lack of a universal feeding reference for such phases represents a knowledge gap, but also a great opportunity to provide adequate nutritional guidance to maintain an age-appropriate microbiome for long term health. Here, we provide a narrative review and perspective on our current understanding of age-appropriate microbiome maturation, its relation to long term health and how nutrition shapes and influences this relationship.

Immunomodulatory Role of Nutrients: How Can Pulmonary Dysfunctions Improve?

Nutrition is an important tool that can be used to modulate the immune response during infectious diseases. In addition, through diet, important substrates are acquired for the biosynthesis of regulatory molecules in the immune response, influencing the progression and treatment of chronic lung diseases, such as asthma and chronic obstructive pulmonary disease (COPD). In this way, nutrition can promote lung health status. A range of nutrients, such as vitamins (A, C, D, and E), minerals (zinc, selenium, iron, and magnesium), flavonoids and fatty acids, play important roles in reducing the risk of pulmonary chronic diseases and viral infections. Through their antioxidant and anti-inflammatory effects, nutrients are associated with better lung function and a lower risk of complications since they can decrease the harmful effects from the immune system during the inflammatory response. In addition, bioactive compounds can even contribute to epigenetic changes, including histone deacetylase (HDAC) modifications that inhibit the transcription of proinflammatory cytokines, which can contribute to the maintenance of homeostasis in the context of infections and chronic inflammatory diseases. These nutrients also play an important role in activating immune responses against pathogens, which can help the immune system during infections. Here, we provide an updated overview of the roles played by dietary factors and how they can affect respiratory health. Therefore, we will show the anti-inflammatory role of flavonoids, fatty acids, vitamins and microbiota, important for the control of chronic inflammatory diseases and allergies, in addition to the antiviral role of vitamins, flavonoids, and minerals during pulmonary viral infections, addressing the mechanisms involved in each function. These mechanisms are interesting in the discussion of perspectives associated with severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) infection and its pulmonary complications since patients with severe disease have vitamins deficiency, especially vitamin D. In addition, researches with the use of flavonoids have been shown to decrease viral replication in vitro. This way, a full understanding of dietary influences can improve the lung health of patients.

The Dietary Fiber Pectin: Health Benefits and Potential for the Treatment of Allergies by Modulation of Gut Microbiota

Purpose of Review

The incidence of allergies is increasing and has been associated with several environmental factors including westernized diets. Changes in environment and nutrition can result in dysbiosis of the skin, gut, and lung microbiota altering the production of microbial metabolites, which may in turn generate epigenetic modifications. The present review addresses studies on pectin-mediated effects on allergies, including the immune modulating mechanisms by bacterial metabolites.

Recent Findings

Recently, microbiota have gained attention as target for allergy intervention, especially with prebiotics, that are able to stimulate the growth and activity of certain microorganisms. Dietary fibers, which cannot be digested in the gastrointestinal tract, can alter the gut microbiota and lead to increased local and systemic concentrations of gut microbiota-derived short chain fatty acids (SCFAs). These can promote the generation of peripheral regulatory T cells (T_reg) by epigenetic modulation and suppress the inflammatory function of dendritic cells (DCs) by transcriptional modulation.

The dietary fiber pectin (a plant-derived polysaccharide commonly used as gelling agent and dietary supplement) can alter the ratio of Firmicutes to Bacteroidetes in gut and lung microbiota, increasing the concentrations of SCFAs in feces and sera, and reducing the development of airway inflammation by suppressing DC function.

Summary

Pectin has shown immunomodulatory effects on allergies, although the underlying mechanisms still need to be elucidated. It has been suggested that the different types of pectin may exert direct and/or indirect immunomodulatory effects through different mechanisms. However, little is known about the relation of certain pectin structures to allergies.

Improved diet quality is associated with decreased concentrations of inflammatory markers in adults with uncontrolled asthma

BACKGROUND

Asthma has become one of the major public health challenges, and recent studies show promising clinical benefits of dietary interventions, such as the Dietary Approaches to Stop Hypertension (DASH) diet.

OBJECTIVE

The objective of this study was to examine whether changes in diet quality are associated with changes in inflammatory markers important in asthma pathophysiology.

METHODS

In this exploratory study in patients with poorly controlled asthma participating in a randomized controlled trial of a DASH intervention study, changes in concentrations of a broad panel of serum proteins (51-plex Luminex assay, Affymetrix) were determined, and their relation to diet quality (DASH score) assessed by combining data of both intervention and usual-care control groups. Second, the relation between the serum proteins, other biomarkers of inflammation and nutrition, and Asthma Control Questionnaire (ACQ) was assessed.

RESULTS

During the first 3 mo, diet quality (DASH scores) were inversely associated (P < 0.05, false discovery rate P < 0.09) with serum concentrations of a large number serum proteins, reflecting not only general proinflammatory markers such as IL-1β, transforming growth factor α (TGF-α), and IL-6 (r = -0.31 to -0.39) but also a number of proteins associated with asthmatic conditions, specifically several T-helper (Th) 2 (Th2; r = -0.29 to -0.34) and Th17 (r = -0.4) associated cytokines and growth factors. Monokine induced by gamma/chemokine (C-X-C motif) ligand 9 (CXCL9) (MIG/CXCL9), a T-cell attractant induced by IFN-γ previously linked to asthma exacerbations, appeared to be the marker most consistently associated with DASH diet quality for the entire 6-mo study period (r = -0.40 and -0.30 for 0-3 and 3-6 mo, respectively, and standardized coefficient loadings -0.13 in the partial least squares analyses). Decreases in 19 serum protein concentrations were also correlated with improved asthma control during the 6-mo study period.

CONCLUSIONS

Our data in adult patients with poorly controlled asthma suggest that dietary changes, like the introduction of DASH, may have beneficial effects on reducing inflammatory status. This trial was registered at http://www.clinicaltrials.gov as NCT01725945.

Protection against allergies: Microbes, immunity, and the farming effect

The prevalence of asthma and other allergic diseases has rapidly increased in "Westernized" countries over recent decades. This rapid increase suggests the involvement of environmental factors, behavioral changes or lifestyle, rather than genetic drift. It has become increasingly clear that the microbiome plays a key role in educating the host immune system and, thus, regulation of disease susceptibility. This review will focus on recent advances uncovering immunological and microbial mechanisms that protect against allergies, in particular, within the context of a farming environment. A whole body of epidemiological data disclosed the nature of the protective exposures in a farm. Current evidence points toward an important role of the host microbiome in setting an immunological equilibrium that determines progression toward, or protection against allergic diseases. Conclusive mechanistic insights on how microbial exposures prevent from developing allergic diseases in humans are still lacking but findings from experimental models reveal plausible immunological mechanisms. Gathering further knowledge on these mechanisms and confirming their relevance in humans is of great importance to develop preventive strategies for children at risk of developing allergies.

Dietary Bioactive Lipids: A Review on Absorption, Metabolism, and Health Properties

Dietary lipids are an indispensable source of energy and nutrition in human life. Numerous studies have shown that dietary bioactive lipids have many health benefits, including prevention or treatment of chronic diseases. The different chemical compositions and structural characteristics of bioactive lipids not only affect their digestion, absorption, and metabolism but also affect their health properties. In this review, the major dietary bioactive lipids (fatty acids, carotenoids, phytosterols, phenolic lipids, fat-soluble vitamins, and sphingomyelins) in foods are systematically summarized, from the aspects of composition, digestion, absorption, metabolism, source, structural characteristics, and their health properties. In particular, the relationship between the compositional and structural changes of bioactive lipids and their absorption and metabolism is discussed as well as their effect on health properties. This review provides a comprehensive summary toward health properties of dietary bioactive lipids.

The power and potential of BIOMAP to elucidate host-microbiome interplay in skin inflammatory diseases

The two most common chronic inflammatory skin diseases are atopic dermatitis (AD) and psoriasis. The underpinnings of the remarkable degree of clinical heterogeneity of AD and psoriasis are poorly understood and, as a consequence, disease onset and progression are unpredictable and the optimal type and time-point for intervention are as yet unknown. The BIOMAP project is the first IMI (Innovative Medicines Initiative) project dedicated to investigating the causes and mechanisms of AD and psoriasis and to identify potential biomarkers responsible for the variation in disease outcome. The consortium includes 7 large pharmaceutical companies and 25 non-industry partners including academia. Since there is mounting evidence supporting an important role for microbial exposures and our microbiota as factors mediating immune polarization and AD and psoriasis pathogenesis, an entire work package is dedicated to the investigation of skin and gut microbiome linked to AD or psoriasis. The large collaborative BIOMAP project will enable the integration of patient cohorts, data and knowledge in unprecedented proportions. The project has a unique opportunity with a potential to bridge and fill the gaps between current problems and solutions. This review highlights the power and potential of BIOMAP project in the investigation of microbe-host interplay in AD and psoriasis.

Cellular and molecular mechanisms of allergic asthma

Asthma is a chronic disease of the airways, which affects more than 350 million people worldwide. It is the most common chronic disease in children, affecting at least 30 million children and young adults in Europe. Asthma is a complex, partially heritable disease with a marked heterogeneity. Its development is influenced both by genetic and environmental factors. The most common, as well as the most well characterized subtype of asthma is allergic eosinophilic asthma, which is characterized by a type 2 airway inflammation. The prevalence of asthma has substantially increased in industrialized countries during the last 60 years. The mechanisms underpinning this phenomenon are incompletely understood, however increased exposure to various environmental pollutants probably plays a role. Disease inception is thought to be enabled by a disadvantageous shift in the balance between protective and harmful lifestyle and environmental factors, including exposure to protective commensal microbes versus infection with pathogens, collectively leading to airway epithelial cell damage and disrupted barrier integrity. Epithelial cell-derived cytokines are one of the main drivers of the type 2 immune response against innocuous allergens, ultimately leading to infiltration of lung tissue with type 2 T helper (T_H2) cells, type 2 innate lymphoid cells (ILC2s), M2 macrophages and eosinophils. This review outlines the mechanisms responsible for the orchestration of type 2 inflammation and summarizes the novel findings, including but not limited to dysregulated epithelial barrier integrity, alarmin release and innate lymphoid cell stimulation.