Metabolomic pathways in food allergy.

Food allergy (FA) is a widespread issue, affecting as many as 10% of the population. Over the past two to three decades, the prevalence of FA has been on the rise, particularly in industrialized and westernized countries. FA is a complex, multifactorial disease mediated by type 2 immune responses and involving environmental and genetic factors. However, the precise mechanisms remain inadequately understood. Metabolomics has the potential to identify disease endotypes, which could beneficially promote personalized prevention and treatment. A metabolome approach would facilitate the identification of surrogate metabolite markers reflecting the disease activity and prognosis. Here, we present a literature overview of recent metabolomic studies conducted on children with FA.

Allergic rhinitis phenotypes with distinct transcriptome profiles in children: A birth cohort.

BACKGROUND: Allergic rhinitis (AR) phenotypes in childhood are unclear. OBJECTIVES: This study sought to determine AR phenotypes and investigate their natural course and clinical and transcriptomic characteristics. METHODS: Latent class trajectory analysis was used for phenotyping AR in 1050 children from birth through 12 years using a birth cohort study. Blood transcriptome analyses were performed to define the underlying mechanisms of each phenotype. RESULTS: Five AR phenotypes were identified: early onset (n = 88, 8.4%), intermediate transient (n = 110, 10.5%), late onset (n = 209, 19.9%), very late onset (n=187, 17.8%), and never/infrequent (n = 456, 43.4%). Children with early-onset AR were associated with higher AR severity and sensitizations to foods at age 1 year and inhalants at age 3 years and asthma symptoms, but not with bronchial hyperresponsiveness (BHR). Children with late-onset AR phenotype associated with sensitizations to various foods at age 1 year but not from age 3 years, and to inhalants from age 7 years and with asthma with BHR. Children with very late-onset AR phenotype associated with sensitizations to foods throughout preschool age and to inhalants at ages 7 and 9 years and with asthma with BHR. Transcriptome analysis showed that early-onset AR was associated with viral/bacterial infection-related defense response, whereas late-onset AR was associated with T cell-related immune response. CONCLUSIONS: Early-onset AR phenotype was associated with sensitization to foods and inhalants at an early age and asthma symptoms, but not with BHR, whereas very late- and late-onset AR phenotypes were positively associated with sensitization to inhalants and asthma with BHR. Transcriptomic analyses indicated that early- and late-onset AR phenotypes had distinct underlying mechanisms related to AR as well.

Complete genome assembly of Enterococcus faecalis strain HL1, isolated from an infant fecal sample.

We present the complete genome sequence of Enterococcus faecalis strain HL1, isolated from infant feces. E. faecalis gains significant attention for its therapeutic potential. The genome of E. faecalis HL1 consists of a 2.7 Mb circular chromosome with no plasmids, and it contains a total of 2,546 predicted coding genes.

The alternative bile acid pathway can predict food allergy persistence in early childhood.

BACKGROUND: Mechanisms underlying persistent food allergy (FA) are not well elucidated. The intestinal mucosa is the primary exposure route of food allergens. However, no study has examined intestinal metabolites associated with FA persistence. The goal of this study was to investigate intestinal metabolites and associated microbiomes in early life that aid in determining the development and persistence of FA. METHODS: We identified metabolomic alterations in the stool of infants according to FA by mass spectrometry-based untargeted metabolome profiling. The targeted metabolomic analysis of bile acid metabolites and stool microbiome was performed. Bile acid metabolite composition in infancy was evaluated by characterizing the subjects at the age of 3 into FA remission and persistent FA. RESULTS: In untargeted metabolomics, primary bile acid biosynthesis was significantly different between subjects with FA and healthy controls. In targeted metabolomics for bile acids, intestinal bile acid metabolites synthesized by the alternative pathway were reduced in infants with FA than those in healthy controls. Subjects with persistent FA were also distinguished from healthy controls and those with FA remission by bile acid metabolites of the alternative pathway. These metabolites were negatively correlated with specific IgE levels in egg white. The abundance of intestinal Clostridia was decreased in the FA group and was correlated with ursodeoxycholic acid. CONCLUSION: Intestinal bile acid metabolites of the alternative pathway could be predictive biomarkers for persistent FA in early childhood. These findings require replication in future studies.

Associations of prenatal antibiotic exposure and delivery mode on childhood asthma inception.

BACKGROUND: Prenatal antibiotic exposure and delivery mode may affect the gut microbiome in early life and influence the development of childhood asthma, but the combined effect of these 2 factors is unknown. OBJECTIVE: To identify the individual and combined effects of prenatal antibiotic exposure and delivery mode on the development of asthma in children and the potential mechanisms underlying these associations. METHODS: A total of 789 children from the Cohort for Childhood Origin of Asthma and Allergic Diseases birth cohort study were enrolled. Asthma was defined as a physician-confirmed diagnosis with asthma symptoms in the previous 12 months at age 7 years. Information on prenatal antibiotic exposure was obtained by mothers using a questionnaire. Logistic regression analysis was used. Gut microbiota analysis using 16S rRNA gene sequencing of fecal specimens obtained at 6 months was undertaken for 207 infants. RESULTS: Prenatal antibiotic exposure and cesarean section delivery (adjusted odds ratio [aOR], 95% confidence interval [CI], 5.70 [1.25-22.81] and 1.57 [1.36-6.14], respectively) were associated with childhood asthma, especially synergistically when compared with the vaginal delivery-prenatal antibiotic exposure reference group (aOR, 7.35; 95% CI, 3.46-39.61; Interaction P = .03). Prenatal antibiotic exposure was associated with childhood asthma with aORs 21.79 and 27.03 for 1 and 2 or more exposures, respectively. Considerable small-airway dysfunction (R5-R20 in impulse oscillometry) was observed with prenatal antibiotic exposure and cesarean section delivery, compared with those with spontaneous delivery without prenatal antibiotic exposure. There was no significant difference in the diversity of gut microbiota among the 4 groups. However, the relative abundance of Clostridium was significantly increased in infants with prenatal antibiotic exposure and delivered by means of cesarean section. CONCLUSION: Prenatal antibiotic exposure and delivery mode might modulate asthma development in children and small-airway dysfunction, potentially through early-life gut microbiota alterations.

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.

Accurate diagnosis of atopic dermatitis by combining transcriptome and microbiota data with supervised machine learning.

Atopic dermatitis (AD) is a common skin disease in childhood whose diagnosis requires expertise in dermatology. Recent studies have indicated that host genes-microbial interactions in the gut contribute to human diseases including AD. We sought to develop an accurate and automated pipeline for AD diagnosis based on transcriptome and microbiota data. Using these data of 161 subjects including AD patients and healthy controls, we trained a machine learning classifier to predict the risk of AD. We found that the classifier could accurately differentiate subjects with AD and healthy individuals based on the omics data with an average F1-score of 0.84. With this classifier, we also identified a set of 35 genes and 50 microbiota features that are predictive for AD. Among the selected features, we discovered at least three genes and three microorganisms directly or indirectly associated with AD. Although further replications in other cohorts are needed, our findings suggest that these genes and microbiota features may provide novel biological insights and may be developed into useful biomarkers of AD prediction.

Ruminococcus gnavus ameliorates atopic dermatitis by enhancing Treg cell and metabolites in BALB/c mice.

BACKGROUND: Ruminococcus gnavus (R. gnavus) are mucin-degrading gut bacteria that play a key role in the early colonization of the gut by serving as endogenous sources of nutrients. They can also influence immune development. We had previously reported a lower abundance of R. gnavus in infants with atopic dermatitis (AD) compared with that in healthy subjects. However, the underlying mechanisms remain unclear. In this study, we investigated the effect of orally administered R. gnavus on antibiotic treatment-induced gut dysbiosis (and the underlying mechanism) in a mouse model of AD. METHODS: Four-week-old female BALB/C mice were administered antibiotic cocktails for 2 weeks. R. gnavus was orally administered throughout the study duration. At 6 weeks of age, AD was induced by epidermal sensitization with ovalbumin. AD phenotypes and systemic and gut immune responses were investigated. RESULTS: Orally administered R. gnavus significantly reduced AD-associated parameters (i.e., transepidermal water loss, clinical score, total serum immunoglobulin (Ig) E level, OVA-specific IgE level, and skin inflammation). R. gnavus treatment also resulted in significant downregulation of T helper 2-related cytokine mRNA and upregulation of interleukin (IL)-10 and Foxp3 in the skin. The population of CD4+ FOXP3+ T cells in mesenteric- and skin-draining lymph nodes and butyrate levels in the cecum increased in R. gnavus-administered AD mice. CONCLUSIONS: Immune modulation by orally administered R. gnavus may alleviate AD symptoms through the enhancement of regulatory T-cell counts and short-chain fatty acids production in AD mice.

Host-microbial interactions between PTGR2 and Bifidobacterium in the early life gut of atopic dermatitis children.

BACKGROUND: Gut microbiota dysbiosis is linked to the development and responses of the immune system and can play an important role in the onset of allergic diseases including atopic dermatitis (AD). This study investigated the association between host genetics and the gut microbiota in AD. METHODS: A global gene expression profiling of the gut epithelial colonocytes, genetic variations analysis, and the gut microbial composition analysis were performed. RESULTS: This study identified the upregulation of PTGR2 (p = .028), a gene involved in prostaglandin catalysis and inflammatory responses, as a potential risk factor for AD. In subsequent fine mapping analysis using 17 single nucleotide polymorphisms (SNPs) of PTGR2 in 864 Korean subjects (420 AD patients and 444 unaffected controls), several SNPs and haplotypes showed significant associations with AD and its SCORing AD (SCORAD) values (p = .002). To investigate host-microbial interactions, further gut microbiota data and genotypes were obtained from an independent cohort of 176 subjects (91 AD patients and 85 controls). From correlation analysis, a significantly negative association between SNP and Bifidobacterium abundance was observed in AD patients (p = .005). In additional observations of PTGR2-associated downstream molecules, NRF2 (p = .004) and several antioxidant genes (GSTT1, GCLC, GPX1; p < .05) showed significantly reduced expression in AD patients. CONCLUSIONS: Our current findings suggest that the interaction between PTGR2 dysregulated expression and a Bifidobacterium abundance affects a higher risk of AD and a more severe onset.

Interactions Between IL-17 Variants and Streptococcus in the Gut Contribute to the Development of Atopic Dermatitis in Infancy.

PURPOSE: Interleukin (IL)-17 variants and perturbations in the gut microbiota may influence the development of atopic dermatitis (AD). However, unifying principles for variants of host and microbe interaction remains unclear. We sought to investigate whether IL-17 variants and gut microbiota affect the development of AD in infancy. METHODS: Composition of the gut microbiota was analyzed in fecal samples from 99 normal healthy and 61 AD infants at 6 months of age. The associations between total immunoglobulin E (IgE), the scoring atopic dermatitis (SCORAD), short-chain fatty acids, transcriptome and functional profile of the gut measured in these subjects and Streptococcus were analyzed. IL-6 and IL-8 in the human intestinal epithelial cell line (HIEC-6) were measured after stimulation of IL-17 and Streptococcus mitis. RESULTS: In this study, Streptococcus was enriched in infants with AD and was higher in those with the GA + AA of IL-17 (rs2275913) variant. Streptococcus was positively correlated with IgE and SCORAD in infants with AD and GA + AA of IL-17. Butyrate and valerate were negatively correlated with Streptococcus and were decreased in infants with AD and GA + AA. Bacterial genes for oxidative phosphorylation induced by reduced colonization of Clostridium were decreased compared with normal and GG. In transcriptome analysis, lactate dehydrogenase A-like 6B was higher in infants with AD compared with healthy infants. IL-6 and IL-8 were increased in IL-17 and/or S. mitis-stimulated HIEC-6 cells. CONCLUSIONS: These findings suggest that increased Streptococcus and A allele of IL-17 (rs2275913) may contribute to the pathogenesis of AD via modulation of the immune system in infancy.

Association of IL13 genetic polymorphisms with atopic dermatitis: Fine mapping and haplotype analysis.

BACKGROUND: Although previous studies had reported an important role of interleukin 13 (IL13) and its genetic polymorphisms in atopic dermatitis (AD), many of these previous reports focused on the missense variant rs20541 (Gln144Arg) without fine mapping of the gene region. OBJECTIVE: To analyze the potential associations of other IL13 variants and their haplotypes with AD and assess total serum immunoglobulin E (IgE) levels. METHODS: We performed fine mapping of single-nucleotide polymorphisms (SNPs) within the IL13 gene in a pilot study of 495 children with AD and 444 healthy controls. Then, we conducted a replication study of 757 children with AD and 1620 healthy controls to evaluate the association between the rs20541 variant of IL13 and AD. RESULTS: In the pilot study, the rs20541 and rs1295685 SNPs in the 3'-untranslated region of IL13 had significant associations with AD (P < .001 and .01, respectively). In addition, 2 haplotypes (BL2_ht1 and BL2_ht2), which harbored the significant rs20541 and rs1295685 SNPs, had an association with AD (minimum P = .006). BL2_ht1 and BL2_ht2 had nominal signals associated with the total serum IgE levels (P < .05) but not with the severity of AD (P > .05). In the replication study, rs20541 was associated with the total serum IgE levels but not with the severity of AD. CONCLUSION: An additional IL13 gene SNP, rs1295685, has a strong linkage disequilibrium with rs20541, and its haplotypes are associated with AD and the total serum IgE levels.

Imbalance of Gut Streptococcus, Clostridium, and Akkermansia Determines the Natural Course of Atopic Dermatitis in Infant.

PURPOSE: The roles of gut microbiota on the natural course of atopic dermatitis (AD) are not yet fully understood. We investigated whether the composition and function of gut microbiota and short-chain fatty acids (SCFAs) at 6 months of age could affect the natural course of AD up to 24 months in early childhood. METHODS: Fecal samples from 132 infants were analyzed using pyrosequencing, including 84 healthy controls, 22 transient AD and 26 persistent AD subjects from the Cohort for Childhood Origin of Asthma and Allergic Diseases (COCOA) birth cohort. The functional profile of the gut microbiome was analyzed by whole-metagenome sequencing. SCFAs were measured using gas chromatography-mass spectrometry. RESULTS: Low levels of Streptococcus and high amounts of Akkermansia were evident in transient AD cases, and low Clostridium, Akkermansia and high Streptococcus were found in children with persistent AD. The relative abundance of Streptococcus positively correlated with scoring of AD (SCORAD) score, whereas that of Clostridium negatively correlated with SCORAD score. The persistent AD group showed decreased gut microbial functional genes related to oxidative phosphorylation compared with healthy controls. Butyrate and valerate levels were lower in transient AD infants compared with healthy and persistent AD infants. CONCLUSIONS: Compositions, functions and metabolites of the early gut microbiome are related to natural courses of AD in infants.

The Small Protein CydX Is Required for Cytochrome bd Quinol Oxidase Stability and Function in Salmonella enterica Serovar Typhimurium: a Phenotypic Study.

Cytochrome bd quinol oxidases, which have a greater affinity for oxygen than heme-copper cytochrome oxidases (HCOs), promote bacterial respiration and fitness in low-oxygen environments, such as host tissues. Here, we show that, in addition to the CydA and CydB subunits, the small protein CydX is required for the assembly and function of the cytochrome bd complex in the enteric pathogen Salmonella enterica serovar Typhimurium. Mutant S Typhimurium lacking CydX showed a loss of proper heme arrangement and impaired oxidase activity comparable to that of a ΔcydABX mutant lacking all cytochrome bd subunits. Moreover, both the ΔcydX mutant and the ΔcydABX mutant showed increased sensitivity to ß-mercaptoethanol and nitric oxide (NO). Cytochrome bd-mediated protection from ß-mercaptoethanol was not a result of resistance to reducing damage but, rather, was due to cytochrome bd oxidase managing Salmonella respiration, while ß-mercaptoethanol interacted with the copper ions necessary for the HCO activity of the cytochrome bo-type quinol oxidase. Interactions between NO and hemes in cytochrome bd and cytochrome bd-dependent respiration during nitrosative stress indicated a direct role for cytochrome bd in mediating Salmonella resistance to NO. Additionally, CydX was required for S Typhimurium proliferation inside macrophages. Mutants deficient in cytochrome bd, however, showed a significant increase in resistance to antibiotics, including aminoglycosides, d-cycloserine, and ampicillin. The essential role of CydX in cytochrome bd assembly and function suggests that targeting this small protein could be a useful antimicrobial strategy, but potential drug tolerance responses should also be considered.IMPORTANCE Cytochrome bd quinol oxidases, which are found only in bacteria, govern the fitness of many facultative anaerobic pathogens by promoting respiration in low-oxygen environments and by conferring resistance to antimicrobial radicals. Thus, cytochrome bd complex assembly and activity are considered potential therapeutic targets. Here we report that the small protein CydX is required for the assembly and function of the cytochrome bd complex in S Typhimurium under stress conditions, including exposure to ß-mercaptoethanol, nitric oxide, or the phagocytic intracellular environment, demonstrating its crucial function for Salmonella fitness. However, cytochrome bd inactivation also leads to increased resistance to some antibiotics, so considerable caution should be taken when developing therapeutic strategies targeting the CydX-dependent cytochrome bd.

The risk of preschool asthma at 2-4 years is not associated with leukocyte telomere length at birth or at 1 year of age.

BACKGROUND: Exposure to prenatal stress is associated with offspring allergic-disease development, and oxidative stress may mediate this relationship. OBJECTIVE: We aimed to evaluate whether leukocyte telomere length (LTL) shortening, a marker for exposure to oxidative stress, in early life is associated with increased risk of asthma development during the preschool period. METHODS: We assessed the follow-up clinical data of a subgroup from a birth cohort whose LTLs had been measured from cord-blood and 1-year peripheral-blood samples. We examined whether the LTLs would be associated with asthma development at the age of 2-4 years. RESULTS: The data of 84 subjects were analyzed. LTLs were measured from the cord-blood and 1-year peripheral blood of 75 and 79 subjects, respectively. Among them, 14 subjects (16.7%) developed bronchial asthma between 2-4 years old. Prenatally stressed subjects had marginally increased odds of developing asthma (p = 0.097). There was no significant difference in the odds of preschool-asthma development between the groups with shorter and longer cord-blood LTLs (odds ratio [OR], 0.651; 95% confidence interval [CI], 0.184-2.306) or in the odds between the groups with shorter and longer 1-year peripheral-blood LTLs (OR, 0.448; 95% CI, 0.135-1.483). Finally, subjects with both higher prenatal stress and shorter LTLs did not have significantly higher odds of preschool-asthma development (for cord-blood: OR, 1.242; 95% CI, 0.353-4.368; for 1-year peripheral-blood: OR, 1.451; 95% CI, 0.428-4.919). CONCLUSION: There was no significant association between early life LTLs and higher risk of bronchial-asthma development during the preschool years.

Leukocyte Telomere Length Reflects Prenatal Stress Exposure, But Does Not Predict Atopic Dermatitis Development at 1 Year.

PURPOSE: Prenatal maternal stress affects offspring's atopic dermatitis (AD) development, which is thought to be mediated by the oxidative stress. We aimed to evaluate the difference in leukocyte telomere length (LTL), a marker for exposure to oxidative stress, according to the prenatal stress exposure and the later AD development. METHODS: From a birth cohort (the COhort for Childhood Origin of Asthma and allergic diseases) that had displayed a good epidemiologic association between the exposure to prenatal stress and AD development in the offspring, we selected 68 pairs of samples from 4 subject groups based on the level of prenatal maternal stress and later AD development. The LTL was measured from both cord blood and 1-year peripheral blood, and their LTLs were compared between subject groups. Finally, the proportion of AD development was examined in the subject groups that are reclassified based on subjects' exposure to prenatal stress and there LTL. RESULTS: Cord-blood LTL was shorter in prenatally stressed infants than in unstressed ones (P = 0.026), which difference was still significant when subjects became 1 year old (P = 0.008). LTL of cord blood, as well as one of the 1-year peripheral blood, was not different according to later AD development at 1 year (P = 0.915 and 0.174, respectively). Shorter LTL made no increase in the proportion of later AD development in either prenatally high-stressed or low-stressed groups (P = 1.000 and 0.473, respectively). CONCLUSIONS: Cord-blood LTL may reflect subjects' exposure to maternal prenatal stress. However, the LTL shortening is not a risk factor of increasing AD development until the age of 1, and a longer investigation may be necessary for validation. Currently, the results doubt the role of LTL shortening as a marker for risk assessment tool for the prenatal stress associated with AD development in the offspring.

Microbiome in the Gut-Skin Axis in Atopic Dermatitis.

The microbiome is vital for immune system development and homeostasis. Changes in microbial composition and function, termed dysbiosis, in the skin and the gut have recently been linked to alterations in immune responses and to the development of skin diseases, such as atopic dermatitis (AD). In this review, we summarize the recent findings on the gut and skin microbiome, highlighting the roles of major commensals in modulating skin and systemic immunity in AD. Although our understanding of the gut-skin axis is only beginning, emerging evidence indicates that the gut and skin microbiome could be manipulated to treat AD.

Inducible spy Transcription Acts as a Sensor for Envelope Stress of Salmonella typhimurium.

Salmonella enterica infects a broad range of host animals, and zoonostic infection threatens both public health and the livestock and meat processing industries. Many antimicrobials have been developed to target Salmonella envelope that performs essential bacterial functions; however, there are very few analytical methods that can be used to validate the efficacy of these antimicrobials. In this study, to develop a potential biosensor for Salmonella envelope stress, we examined the transcription of the S. enterica serovar typhimurium spy gene, the ortholog of which in Escherichia coli encodes Spy (spheroplast protein y). Spy is a chaperone protein expressed and localized in the periplasm of E. coli during spheroplast formation, or by exposure to protein denaturing conditions. spy expression in S. typhimurium was examined by constructing a spy-gfp transcriptional fusion. S. typhimurium spy transcription was strongly induced during spheroplast formation, and also when exposed to membrane-disrupting agents, including ethanol and the antimicrobial peptide polymyxin B. Moreover, spy induction required the activity of regulator proteins BaeR and CpxR, which are part of the major envelope stress response systems BaeS/BaeR and CpxA/CpxR, respectively. Results suggest that monitoring spy transcription may be useful to determine whether a molecule particularly cause envelope stress in Salmonella.