Early-life nasal microbiota dynamics relate to longitudinal respiratory phenotypes in urban children.

BACKGROUND: Five distinct respiratory phenotypes based on latent classes of longitudinal patterns of wheezing, allergic sensitization. and pulmonary function measured in urban children from ages from 0 to 7 years have previously been described. OBJECTIVE: Our aim was to determine whether distinct respiratory phenotypes are associated with early-life upper respiratory microbiota development and environmental microbial exposures. METHODS: Microbiota profiling was performed using 16S ribosomal RNA-based sequencing of nasal samples collected at age 12 months (n = 120) or age 36 months (n = 142) and paired house dust samples collected at 3 months (12-month, n = 73; 36-month, n = 90) from all 4 centers in the Urban Environment and Childhood Asthma (URECA) cohort. RESULTS: In these high-risk urban children, nasal microbiota increased in diversity between ages 12 and 36 months (ß = 2.04; P = .006). Age-related changes in microbiota evenness differed significantly by respiratory phenotypes (interaction P = .0007), increasing most in the transient wheeze group. At age 12 months, respiratory illness (R2 = 0.055; P = .0001) and dominant bacterial genus (R2 = 0.59; P = .0001) explained variance in nasal microbiota composition, and enrichment of Moraxella and Haemophilus members was associated with both transient and high-wheeze respiratory phenotypes. By age 36 months, nasal microbiota was significantly associated with respiratory phenotypes (R2 = 0.019; P = .0376), and Moraxella-dominated microbiota was associated specifically with atopy-associated phenotypes. Analysis of paired house dust and nasal samples indicated that 12 month olds with low wheeze and atopy incidence exhibited the largest number of shared bacterial taxa with their environment. CONCLUSION: Nasal microbiota development over the course of early childhood and composition at age 3 years are associated with longitudinal respiratory phenotypes. These data provide evidence supporting an early-life window of airway microbiota development that is influenced by environmental microbial exposures in infancy and associates with wheeze- and atopy-associated respiratory phenotypes through age 7 years.

Precocious infant fecal microbiome promotes enterocyte barrier dysfuction, altered neuroendocrine signaling and associates with increased childhood obesity risk.

Early life gut microbiome composition has been correlated with childhood obesity, though microbial functional contributions to disease origins remain unclear. Here, using an infant birth cohort (n = 349) we identify a distinct fecal microbiota composition in 1-month-old infants with the lowest rate of exclusive breastfeeding, that relates with higher relative risk for obesity and overweight phenotypes at two years. Higher-risk infant fecal microbiomes exhibited accelerated taxonomic and functional maturation and broad-ranging metabolic reprogramming, including reduced concentrations of neuro-endocrine signals. In vitro, exposure of enterocytes to fecal extracts from higher-risk infants led to upregulation of genes associated with obesity and with expansion of nutrient sensing enteroendocrine progenitor cells. Fecal extracts from higher-risk infants also promoted enterocyte barrier dysfunction. These data implicate dysregulation of infant microbiome functional development, and more specifically promotion of enteroendocrine signaling and epithelial barrier impairment in the early-life developmental origins of childhood obesity.

Heritable vaginal bacteria influence immune tolerance and relate to early-life markers of allergic sensitization in infancy.

Maternal asthma status, prenatal exposures, and infant gut microbiota perturbation are associated with heightened risk of atopy and asthma risk in childhood, observations hypothetically linked by intergenerational microbial transmission. Using maternal vaginal (n = 184) and paired infant stool (n = 172) samples, we identify four compositionally and functionally distinct Lactobacillus-dominated vaginal microbiota clusters (VCs) that relate to prenatal maternal health and exposures and infant serum immunoglobulin E (IgE) status at 1 year. Variance in bacteria shared between mother and infant pairs relate to VCs, maternal allergy/asthma status, and infant IgE levels. Heritable bacterial gene pathways associated with infant IgE include fatty acid synthesis and histamine and tryptophan degradation. In vitro, vertically transmitted Lactobacillus jensenii strains induce immunosuppressive phenotypes on human antigen-presenting cells. Murine supplementation with L. jensenii reduces lung eosinophils, neutrophilic expansion, and the proportion of interleukin-4 (IL-4)+ CD4+ T cells. Thus, bacterial and atopy heritability are intimately linked, suggesting a microbial component of intergenerational disease transmission.

Maternal prenatal immunity, neonatal trained immunity, and early airway microbiota shape childhood asthma development.

BACKGROUND: The path to childhood asthma is thought to initiate in utero and be further promoted by postnatal exposures. However, the underlying mechanisms remain underexplored. We hypothesized that prenatal maternal immune dysfunction associated with increased childhood asthma risk (revealed by low IFN-γ:IL-13 secretion during the third trimester of pregnancy) alters neonatal immune training through epigenetic mechanisms and promotes early-life airway colonization by asthmagenic microbiota. METHODS: We examined epigenetic, immunologic, and microbial features potentially related to maternal prenatal immunity (IFN-γ:IL-13 ratio) and childhood asthma in a birth cohort of mother-child dyads sampled pre-, peri-, and postnatally (N = 155). Epigenome-wide DNA methylation and cytokine production were assessed in cord blood mononuclear cells (CBMC) by array profiling and ELISA, respectively. Nasopharyngeal microbiome composition was characterized at age 2-36 months by 16S rRNA sequencing. RESULTS: Maternal prenatal immune status related to methylome profiles in neonates born to non-asthmatic mothers. A module of differentially methylated CpG sites enriched for microbe-responsive elements was associated with childhood asthma. In vitro responsiveness to microbial products was impaired in CBMCs from neonates born to mothers with the lowest IFN-γ:IL-13 ratio, suggesting defective neonatal innate immunity in those who developed asthma during childhood. These infants exhibited a distinct pattern of upper airway microbiota development characterized by early-life colonization by Haemophilus that transitioned to a Moraxella-dominated microbiota by age 36 months. CONCLUSIONS: Maternal prenatal immune status shapes asthma development in her child by altering the epigenome and trained innate immunity at birth, and is associated with pathologic upper airway microbial colonization in early life.

Infant gut bacterial community composition and food-related manifestation of atopy in early childhood.

BACKGROUND: Immunoglobulin E-mediated food allergy (IgE-FA) has emerged as a global public health concern. Immune dysregulation is an underlying mechanism for IgE-FA, caused by "dysbiosis" of the early intestinal microbiota. We investigated the association between infant gut bacterial composition and food-related atopy at age 3-5 years using a well-characterized birth cohort. METHODS: The study definition of IgE-FA to egg, milk, or peanut was based on physician panel retrospective review of clinical and questionnaire data collected from birth through age 3-5 years. Using 16S rRNA sequencing, we profiled the bacterial gut microbiota present in stool specimens collected at 1 and 6 months of age. RESULTS: Of 447 infants with data for analysis, 44 (9.8%) met physician panel review criteria for IgE-FA to ≥1 of the three allergens. Among children classified as IgE-FA at 3-5 years, infant stool samples showed significantly less diversity of the gut microbiota compared with the samples of children classified as no IgE-FA at age 3-5 years, especially for milk and peanut (all covariate-adjusted p's for alpha metrics <.007). Testing of individual operational taxonomic units (OTUs) revealed 6-month deficiencies in 31 OTUs for IgE-FA compared with no IgE-FA, mostly in the orders Lactobacillales, Bacteroidales, and Clostridiales. CONCLUSIONS: Variations in gut microbial composition in infant stool were associated with a study definition of IgE-FA at 3-5 years of age. This included evidence of a lack of bacterial diversity, deficiencies in specific OTUs, and delayed microbial maturation. Results support dysbiosis in IgE-FA pathogenesis.

Maternal gut microbiome regulates immunity to RSV infection in offspring.

Development of the immune system can be influenced by diverse extrinsic and intrinsic factors that influence the risk of disease. Severe early life respiratory syncytial virus (RSV) infection is associated with persistent immune alterations. Previously, our group had shown that adult mice orally supplemented with Lactobacillus johnsonii exhibited decreased airway immunopathology following RSV infection. Here, we demonstrate that offspring of mice supplemented with L. johnsonii exhibit reduced airway mucus and Th2 cell-mediated response to RSV infection. Maternal supplementation resulted in a consistent gut microbiome in mothers and their offspring. Importantly, supplemented maternal plasma and breastmilk, and offspring plasma, exhibited decreased inflammatory metabolites. Cross-fostering studies showed that prenatal Lactobacillus exposure led to decreased Th2 cytokines and lung inflammation following RSV infection, while postnatal Lactobacillus exposure diminished goblet cell hypertrophy and mucus production in the lung in response to airway infection. These studies demonstrate that Lactobacillus modulation of the maternal microbiome and associated metabolic reprogramming enhance airway protection against RSV in neonates.

Gut microbiome is associated with multiple sclerosis activity in children.

OBJECTIVE: To identify features of the gut microbiome associated with multiple sclerosis activity over time. METHODS: We used 16S ribosomal RNA sequencing from stool of 55 recently diagnosed pediatric-onset multiple sclerosis patients. Microbiome features included the abundance of individual microbes and networks identified from weighted genetic correlation network analyses. Prentice-Williams-Peterson Cox proportional hazards models estimated the associations between features and three disease activity outcomes: clinical relapses and both new/enlarging T2 lesions and new gadolinium-enhancing lesions on brain MRI. Analyses were adjusted for age, sex, and disease-modifying therapies. RESULTS: Participants were followed, on average, 2.1 years. Five microbes were nominally associated with all three disease activity outcomes after multiple testing correction. These included butyrate producers Odoribacter (relapse hazard ratio = 0.46, 95% confidence interval: 0.24, 0.88) and Butyricicoccus (relapse hazard ratio = 0.49, 95% confidence interval: 0.28, 0.88). Two networks of co-occurring gut microbes were significantly associated with a higher hazard of both MRI outcomes (gadolinium-enhancing lesion hazard ratios (95% confidence intervals) for Modules 32 and 33 were 1.29 (1.08, 1.54) and 1.42 (1.18, 1.71), respectively; T2 lesion hazard ratios (95% confidence intervals) for Modules 32 and 33 were 1.34 (1.15, 1.56) and 1.41 (1.21, 1.64), respectively). Metagenomic predictions of these networks demonstrated enrichment for amino acid biosynthesis pathways. INTERPRETATION: Both individual and networks of gut microbes were associated with longitudinal multiple sclerosis activity. Known functions and metagenomic predictions of these microbes suggest the important role of butyrate and amino acid biosynthesis pathways. This provides strong support for future development of personalized microbiome interventions to modify multiple sclerosis disease activity.

Gut microbiome stability and dynamics in healthy donors and patients with non-gastrointestinal cancers.

As microbial therapeutics are increasingly being tested in diverse patient populations, it is essential to understand the host and environmental factors influencing the microbiome. Through analysis of 1,359 gut microbiome samples from 946 healthy donors of the Milieu Intérieur cohort, we detail how microbiome composition is associated with host factors, lifestyle parameters, and disease states. Using a genome-based taxonomy, we found biological sex was the strongest driver of community composition. Additionally, bacterial populations shift across decades of life (age 20-69), with Bacteroidota species consistently increased with age while Actinobacteriota species, including Bifidobacterium, decreased. Longitudinal sampling revealed that short-term stability exceeds interindividual differences. By accounting for these factors, we defined global shifts in the microbiomes of patients with non-gastrointestinal tumors compared with healthy donors. Together, these results demonstrated that the microbiome displays predictable variations as a function of sex, age, and disease state. These variations must be considered when designing microbiome-targeted therapies or interpreting differences thought to be linked to pathophysiology or therapeutic response.

Maternal and cord blood vitamin D level and the infant gut microbiota in a birth cohort study.

BACKGROUND: Mounting evidence suggests both vitamin D and the early life gut microbiome influence childhood health outcomes. However, little is known about how these two important exposures are related. We aimed to examine associations between plasma 25-hydroxyvitamin D (25[OH]D) levels during pregnancy or at delivery (cord blood) and infant gut microbiota. METHODS: Maternal and cord blood 25[OH]D levels were assessed in a sample of pregnant women. Compositional analyses adjusted for race were run on the gut microbiota of their offspring at 1 and 6 months of age. RESULTS: Mean prenatal 25(OH)D level was 25.04 ± 11.62 ng/mL and mean cord blood 25(OH)D level was 10.88 ± 6.77 ng/mL. Increasing prenatal 25(OH)D level was significantly associated with decreased richness (p = 0.028) and diversity (p = 0.012) of the gut microbiota at 1 month of age. Both prenatal and cord 25(OH)D were significantly associated with 1 month microbiota composition. A total of 6 operational taxonomic units (OTUs) were significantly associated with prenatal 25(OH)D level (four positively and two negatively) while 11 OTUs were significantly associated with cord 25(OH)D (10 positively and one negatively). Of these, OTU 93 (Acinetobacter) and OTU 210 (Corynebacterium), were consistently positively associated with maternal and cord 25(OH)D; OTU 64 (Ruminococcus gnavus) was positively associated with prenatal 25(OH)D but negatively associated with cord 25(OH)D. CONCLUSIONS: Prenatal maternal and cord blood 25(OH)D levels are associated with the early life gut microbiota. Future studies are needed to understand how vitamin D and the microbiome may interact to influence child health.

Author Correction: Elevated faecal 12,13-diHOME concentration in neonates at high risk for asthma is produced by gut bacteria and impedes immune tolerance.

An amendment to this paper has been published and can be accessed via a link at the top of the paper.

Elevated faecal 12,13-diHOME concentration in neonates at high risk for asthma is produced by gut bacteria and impedes immune tolerance.

Neonates at risk of childhood atopy and asthma exhibit perturbation of the gut microbiome, metabolic dysfunction and increased concentrations of 12,13-diHOME in their faeces. However, the mechanism, source and contribution of this lipid to allergic inflammation remain unknown. Here, we show that intra-abdominal treatment of mice with 12,13-diHOME increased pulmonary inflammation and decreased the number of regulatory T (Treg) cells in the lungs. Treatment of human dendritic cells with 12,13-diHOME altered expression of PPARγ-regulated genes and reduced anti-inflammatory cytokine secretion and the number of Treg cells in vitro. Shotgun metagenomic sequencing of neonatal faeces indicated that bacterial epoxide hydrolase (EH) genes are more abundant in the gut microbiome of neonates who develop atopy and/or asthma during childhood. Three of these bacterial EH genes (3EH) specifically produce 12,13-diHOME, and treatment of mice with bacterial strains expressing 3EH caused a decrease in the number of lung Treg cells in an allergen challenge model. In two small birth cohorts, an increase in the copy number of 3EH or the concentration of 12,13-diHOME in the faeces of neonates was found to be associated with an increased probability of developing atopy, eczema or asthma during childhood. Our data indicate that elevated 12,13-diHOME concentrations impede immune tolerance and may be produced by bacterial EHs in the neonatal gut, offering a mechanistic link between perturbation of the gut microbiome during early life and atopy and asthma during childhood.

A20 in dendritic cells restrains intestinal anti-bacterial peptide expression and preserves commensal homeostasis.

Microbial dysbiosis commonly occurs in patients with inflammatory bowel diseases (IBD). Exogenous causes of dysbiosis such as antibiotics and diet are well described, but host derived causes are understudied. A20 is a potent regulator of signals triggered by microbial pattern molecules, and A20 regulates susceptibility to intestinal inflammation in mice and in humans. We now report that mice lacking A20 expression in dendritic cells, A20FL/FL CD11c-Cre mice (or A20dDC mice), spontaneously develop colitogenic intestinal dysbiosis that is evident upon weaning and precedes the onset of colitis. Intestines from A20dDC mice express increased amounts of Reg3ß and Reg3γ, but not Ang4. A20 deficient DCs promote gut microbiota perturbation in the absence of adaptive lymphocytes. Moreover, A20 deficient DCs directly induce expression of Reg3ß and Reg3γ but not Ang 4 in normal intestinal epithelial cell enteroid cultures in the absence of other cell types. These findings reveal a pathophysiological pathway in which defective expression of an IBD susceptibility gene in DCs drives aberrant expression of anti-bacterial peptides and luminal dysbiosis that in turn confers host susceptibility to intestinal inflammation.

Distinct nasal airway bacterial microbiotas differentially relate to exacerbation in pediatric patients with asthma.

BACKGROUND: In infants, distinct nasopharyngeal bacterial microbiotas differentially associate with the incidence and severity of acute respiratory tract infection and childhood asthma development. OBJECTIVE: We hypothesized that distinct nasal airway microbiota structures also exist in children with asthma and relate to clinical outcomes. METHODS: Nasal secretion samples (n = 3122) collected after randomization during the fall season from children with asthma (6-17 years, n = 413) enrolled in a trial of omalizumab (anti-IgE) underwent 16S rRNA profiling. Statistical analyses with exacerbation as the primary outcome and rhinovirus infection and respiratory illnesses as secondary outcomes were performed. Using A549 epithelial cells, we assessed nasal isolates of Moraxella, Staphylococcus, and Corynebacterium species for their capacity to induce epithelial damage and inflammatory responses. RESULTS: Six nasal airway microbiota assemblages, each dominated by Moraxella, Staphylococcus, Corynebacterium, Streptococcus, Alloiococcus, or Haemophilus species, were observed. Moraxella and Staphylococcus species-dominated microbiotas were most frequently detected and exhibited temporal stability. Nasal microbiotas dominated by Moraxella species were associated with increased exacerbation risk and eosinophil activation. Staphylococcus or Corynebacterium species-dominated microbiotas were associated with reduced respiratory illness and exacerbation events, whereas Streptococcus species-dominated assemblages increased the risk of rhinovirus infection. Nasal microbiota composition remained relatively stable despite viral infection or exacerbation; only a few taxa belonging to the dominant genera exhibited relative abundance fluctuations during these events. In vitro, Moraxella catarrhalis induced significantly greater epithelial damage and inflammatory cytokine expression (IL-33 and IL-8) compared with other dominant nasal bacterial isolates tested. CONCLUSION: Distinct nasal airway microbiotas of children with asthma relate to the likelihood of exacerbation, rhinovirus infection, and respiratory illnesses during the fall season.

Longitudinal Phenotypes of Respiratory Health in a High-Risk Urban Birth Cohort.

RATIONALE: Characterization of patterns of wheezing and allergic sensitization in early life may allow for identification of specific environmental exposures impacting asthma development. OBJECTIVES: To define respiratory phenotypes in inner-city children and their associations with early-life environmental exposures. METHODS: Data were collected prospectively from 442 children in the URECA (Urban Environment and Childhood Asthma) birth cohort through age 7 years, reflecting symptoms (wheezing), aeroallergen sensitization, pulmonary function, and body mass index. Latent class mixed models identified trajectories of wheezing, allergic sensitization, and pulmonary function. Cluster analysis defined nonoverlapping groups (termed phenotypes). Potential associations between phenotypes and early-life environmental exposures were examined. MEASUREMENTS AND MAIN RESULTS: Five phenotypes were identified and mainly differentiated by patterns of wheezing and allergic sensitization (low wheeze/low atopy; low wheeze/high atopy; transient wheeze/low atopy; high wheeze/low atopy; high wheeze/high atopy). Asthma was most often present in the high-wheeze phenotypes, with greatest respiratory morbidity among children with frequent wheezing and allergic sensitization. These phenotypes differentially related to early-life exposures, including maternal stress and depression, antenatal environmental tobacco smoke, house dust microbiome, and allergen content (all P < 0.05). Prenatal smoke exposure, maternal stress, and depression were highest in the high-wheeze/low-atopy phenotype. The high-wheeze/high-atopy phenotype was associated with low household microbial richness and diversity. Early-life aeroallergen exposure was low in high-wheeze phenotypes. CONCLUSIONS: Patterns of wheezing, allergic sensitization, and lung function identified five respiratory phenotypes among inner-city children. Early-life environmental exposure to stress, depression, tobacco smoke, and indoor allergens and microbes differentially associate with specific phenotypes.

Early-life home environment and risk of asthma among inner-city children.

BACKGROUND: Environmental exposures in early life appear to play an important role in the pathogenesis of childhood asthma, but the potentially modifiable exposures that lead to asthma remain uncertain. OBJECTIVE: We sought to identify early-life environmental risk factors for childhood asthma in a birth cohort of high-risk inner-city children. METHODS: We examined the relationship of prenatal and early-life environmental factors to the occurrence of asthma at 7 years of age among 442 children. RESULTS: Higher house dust concentrations of cockroach, mouse, and cat allergens in the first 3 years of life were associated with lower risk of asthma (for cockroach allergen: odds ratio per interquartile range increase in concentration, 0.55; 95% CI, 0.36-0.86; P < .01). House dust microbiome analysis using 16S ribosomal RNA sequencing identified 202 and 171 bacterial taxa that were significantly (false discovery rate < 0.05) more or less abundant, respectively, in the homes of children with asthma. A majority of these bacteria were significantly correlated with 1 of more allergen concentrations. Other factors associated significantly positively with asthma included umbilical cord plasma cotinine concentration (odds ratio per geometric SD increase in concentration, 1.76; 95% CI, 1.00-3.09; P = .048) and maternal stress and depression scores. CONCLUSION: Among high-risk inner-city children, higher indoor levels of pet or pest allergens in infancy were associated with lower risk of asthma. The abundance of a number of bacterial taxa in house dust was associated with increased or decreased asthma risk. Prenatal tobacco smoke exposure and higher maternal stress and depression scores in early life were associated with increased asthma risk.

Breast Milk Transforming Growth Factor ß Is Associated With Neonatal Gut Microbial Composition.

BACKGROUND AND OBJECTIVES: Breast milk is a complex bioactive fluid that varies across numerous maternal and environmental conditions. Although breast-feeding is known to affect neonatal gut microbiome, the milk components responsible for this effect are not well-characterized. Given the wide range of immunological activity breast milk cytokines engage in, we investigated 3 essential breast milk cytokines and their association with early life gut microbiota. METHODS: A total of 52 maternal-child pairs were drawn from a racially diverse birth cohort based in Detroit, Michigan. Breast milk and neonatal stool specimens were collected at 1-month postpartum. Breast milk transforming growth factor (TGF)ß1, TGFß2, and IL-10 were assayed using enzyme-linked immunosorbent assays, whereas neonatal gut microbiome was profiled using 16S rRNA sequencing. RESULTS: Individually, immunomodulators TGFß1 and TGFß2 were significantly associated with neonatal gut microbial composition (R = 0.024, P = 0.041; R = 0.026, P = 0.012, respectively) and increased richness, evenness, and diversity, but IL-10 was not. The effects of TGFß1 and TGFß2, however, were not independent of one another, and the effect of TGFß2 was stronger than that of TGFß1. Higher levels of TGFß2 were associated with the increased relative abundance of several bacteria, including members of Streptococcaceae and Ruminococcaceae, and lower relative abundance of distinct Staphylococcaceae taxa. CONCLUSIONS: Breast milk TGFß concentration explains a portion of variability in gut bacterial microbiota composition among breast-fed neonates. Whether TGFß acts in isolation or jointly with other bioactive components to alter bacterial composition requires further investigation. These findings contribute to an increased understanding of how breast-feeding affects the gut microbiome-and potentially immune development-in early life.

Neonatal gut microbiota associates with childhood multisensitized atopy and T cell differentiation.

Gut microbiota bacterial depletions and altered metabolic activity at 3 months are implicated in childhood atopy and asthma. We hypothesized that compositionally distinct human neonatal gut microbiota (NGM) exist, and are differentially related to relative risk (RR) of childhood atopy and asthma. Using stool samples (n = 298; aged 1-11 months) from a US birth cohort and 16S rRNA sequencing, neonates (median age, 35 d) were divisible into three microbiota composition states (NGM1-3). Each incurred a substantially different RR for multisensitized atopy at age 2 years and doctor-diagnosed asthma at age 4 years. The highest risk group, labeled NGM3, showed lower relative abundance of certain bacteria (for example, Bifidobacterium, Akkermansia and Faecalibacterium), higher relative abundance of particular fungi (Candida and Rhodotorula) and a distinct fecal metabolome enriched for pro-inflammatory metabolites. Ex vivo culture of human adult peripheral T cells with sterile fecal water from NGM3 subjects increased the proportion of CD4+ cells producing interleukin (IL)-4 and reduced the relative abundance of CD4+CD25+FOXP3+ cells. 12,13-DiHOME, enriched in NGM3 versus lower-risk NGM states, recapitulated the effect of NGM3 fecal water on relative CD4+CD25+FOXP3+ cell abundance. These findings suggest that neonatal gut microbiome dysbiosis might promote CD4+ T cell dysfunction associated with childhood atopy.

Joint effects of pregnancy, sociocultural, and environmental factors on early life gut microbiome structure and diversity.

The joint impact of pregnancy, environmental, and sociocultural exposures on early life gut microbiome is not yet well-characterized, especially in racially and socioeconomically diverse populations. Gut microbiota of 298 children from a Detroit-based birth cohort were profiled using 16S rRNA sequencing: 130 neonates (median age = 1.2 months) and 168 infants (median age = 6.6 months). Multiple factors were associated with neonatal gut microbiome composition in both single- and multi-factor models, with independent contributions of maternal race-ethnicity, breastfeeding, mode of delivery, marital status, exposure to environmental tobacco smoke, and indoor pets. These findings were consistent in the infants, and networks demonstrating the shared impact of factors on gut microbial composition also showed notable topological similarity between neonates and infants. Further, latent groups defined by these factors explained additional variation, highlighting the importance of combinatorial effects. Our findings also have implications for studies investigating the impact of the early life gut microbiota on disease.

Microbiota in allergy and asthma and the emerging relationship with the gut microbiome.

Asthma and atopy, classically associated with hyper-activation of the T helper 2 (Th2) arm of adaptive immunity, are among the most common chronic illnesses worldwide. Emerging evidence relates atopy and asthma to the composition and function of the human microbiome, the collection of microbes that reside in and on and interact with the human body. The ability to interrogate microbial ecology of the human host is due in large part to recent technological developments that permit identification of microbes and their products using culture-independent molecular detection techniques. In this review we explore the roles of respiratory, gut, and environmental microbiomes in asthma and allergic disease development, manifestation, and attenuation. Though still a relatively nascent field of research, evidence to date suggests that the airway and/or gut microbiome may represent fertile targets for prevention or management of allergic asthma and other diseases in which adaptive immune dysfunction is a prominent feature.

Effects of early-life exposure to allergens and bacteria on recurrent wheeze and atopy in urban children.

BACKGROUND: Wheezing illnesses cause major morbidity in infants and are frequent precursors to asthma. OBJECTIVE: We sought to examine environmental factors associated with recurrent wheezing in inner-city environments. METHODS: The Urban Environment and Childhood Asthma study examined a birth cohort at high risk for asthma (n = 560) in Baltimore, Boston, New York, and St Louis. Environmental assessments included allergen exposure and, in a nested case-control study of 104 children, the bacterial content of house dust collected in the first year of life. Associations were determined among environmental factors, aeroallergen sensitization, and recurrent wheezing at age 3 years. RESULTS: Cumulative allergen exposure over the first 3 years was associated with allergic sensitization, and sensitization at age 3 years was related to recurrent wheeze. In contrast, first-year exposure to cockroach, mouse, and cat allergens was negatively associated with recurrent wheeze (odds ratio, 0.60, 0.65, and 0.75, respectively; P ≤ .01). Differences in house dust bacterial content in the first year, especially reduced exposure to specific Firmicutes and Bacteriodetes, was associated with atopy and atopic wheeze. Exposure to high levels of both allergens and this subset of bacteria in the first year of life was most common among children without atopy or wheeze. CONCLUSIONS: In inner-city environments children with the highest exposure to specific allergens and bacteria during their first year were least likely to have recurrent wheeze and allergic sensitization. These findings suggest that concomitant exposure to high levels of certain allergens and bacteria in early life might be beneficial and suggest new preventive strategies for wheezing and allergic diseases.