Infant gut microbiota and food sensitization: associations in the first year of life

Exploring the Gut Microbiota Landscape in Cow Milk Protein Allergy: Clinical Insights and Diagnostic Implications in Pediatric Patients

Cow milk protein allergy (CMPA) is a significant health concern characterized by adverse immune reactions to cow milk proteins. Biomarkers for the accurate diagnosis and prognosis of CMPA are lacking. This study analyzed the clinical features of CMPA, and 16S RNA sequencing was used to investigate potential biomarkers through fecal microbiota profiling. Children with CMPA exhibit a range of clinical symptoms, including gastrointestinal (83% of patients), skin (53% of patients), and respiratory manifestations (26% of patients), highlighting the complexity of this condition. Laboratory analysis revealed significant differences in red cell distribution width (RDW) and inflammatory markers between the CMPA and control groups, suggesting immune activation and inflammatory responses in CMPA. Microbial diversity analysis revealed higher specific diversity indices in the CMPA group compared with those in control group, with significant differences at the genus and species levels. Bacteroides were more abundant in the CMPA group, whereas Bifidobacterium, Ruminococcus, Faecalibacterium, and Parabacteroides were less abundant. The control group exhibited a balanced microbial profile, with a predominant presence of Bifidobacterium bifidum and Akkermansia muciniphila. The significant abundance of Bifidobacterium in the control group (23.19% vs 9.89% in CMPA) was associated with improved growth metrics such as height and weight, suggesting its potential as a probiotic to prevent CMPA and enhance gut health. Correlation analysis linked specific microbial taxa such as Coprococcus and Bifidobacterium to clinical parameters such as family allergy history, weight and height, providing insights into CMPA pathogenesis. Significant differences in bacterial abundance suggested diagnostic potential, with a panel of 6 bacteria achieving high predictive accuracy (area under curve (AUC) = 0.8708). This study emphasizes the complex relationship between the gut microbiota and CMPA, offering valuable insights into disease mechanisms and diagnostic strategies.

IBD functions as a double-edged sword for food allergy in BALB/c mice model

Inflammatory bowel disease (IBD) and food allergy (FA) increase in tandem, but the potential impact of IBD on FA remains unclear. We sought to determine the role of IBD on FA. We first assessed the changes of FA-related risk factors in dextran sulphate sodium salt (DSS) induced colitis mice model. Then, we evaluated the role of IBD on FA in mice. FA responses were determined using a clinical allergy score, body temperature change, serum antibody levels, cytokines level and mouse mast cell protease 1 (MMCP-1) concentration. Accumulation of regulatory T cells was tested using flow cytometry. Intestinal changes were identified by histology, immunohistochemistry, gene expression and gut microbial community structure. In DSS-induced colitis mice model, we found the intestinal damage, colonic neutrophil infiltration, and downregulation of splenic Th2 cytokines and Tregs in mesenteric lymph nodes (MLN). Moreover, we also found that IBD can alleviate the FA symptoms and lead to the significant downregulation of Th2 cytokines, serum IgE and MMCP-1. However, IBD exacerbates intestinal injury and promotes the gene expression levels of IL-33 and IL-5 in the small intestine, damages the intestinal tissue structure and aggravates intestinal dysbiosis in FA. IBD functions as a double-edged sword in FA. From the perspective of clinical symptoms and humoral immune responses, IBD can reduce FA response by downregulating Th2 cytokines. But from the perspective of the intestinal immune system, IBD potentially disrupts intestinal tolerance to food antigens by damaging intestinal tissue structure and causing intestinal dysbiosis.

Innate lymphoid cells in immunoglobulin E-mediated food allergy

PURPOSE OF REVIEW

Recognition of the importance of innate lymphoid cells (ILCs) in the immune mechanisms of food allergy has grown in recent years. This review summarizes recent findings of ILCs in immunoglobulin E (IgE)-mediated food allergy. New research on ILCs in the context of the microbiome and other atopic diseases are also considered with respect to how they can inform understanding of the role of ILCs in food allergy.

RECENT FINDINGS

ILCs can mediate allergic and tolerogenic responses through multiple pathways. A novel subset of interleukin (IL)-10 producing ILC2s are associated with tolerance following immunotherapy to grass pollen, house dust mite allergy and lipid transfer protein allergy. ILC2s can drive food allergen-specific T cell responses in an antigen-specific manner. A memory subset of ILC2s has been identified through studies of other atopic diseases and is associated with effectiveness of response to therapy.

SUMMARY

The role of ILCs in food allergy and oral tolerance is relatively understudied compared to other diseases. ILCs can modulate immune responses through several mechanisms, and it is likely that these are of importance in the context of food allergy. Better understanding of theses pathways may help to answer fundamental questions regarding the development of food allergy and lead to novel therapeutic targets and treatment.

Risk of Asthma and Allergies in Children Delivered by Cesarean Section: A Comprehensive Systematic Review

BACKGROUND

It is unclear whether cesarean delivery increases the risk of allergic diseases in offspring.

OBJECTIVE

To investigate the association between cesarean delivery and the risk of allergic diseases in offspring.

METHODS

We searched PubMed, Embase, and the Cochrane Library for relevant studies up to October 12, 2023. Observational studies comparing the risk of allergic diseases in offspring delivered by cesarean section versus those delivered vaginally were included. Most-adjusted estimates from individual studies were synthesized by meta-analysis.

RESULTS

A total of 113 studies were included, 70 of which had a low risk of bias. Compared with offspring delivered vaginally, offspring delivered by cesarean section had significantly greater risks of asthma (odds ratio [OR] = 1.20; 95% CI, 1.16-1.25), allergic rhinitis or conjunctivitis (OR = 1.15' CI 1.09-1.22), atopic dermatitis or eczema (OR = 1.08; CI, 1.04-1.13), food allergies (OR = 1.35; CI, 1.18-1.54), and allergic sensitization (OR = 1.19; CI, 1.10-1.28). Cesarean delivery did not significantly increase urticaria risk. Sensitivity analyses including only studies with a low risk of bias, adjusted estimates, prospective data collection, large sample sizes, or outcomes from medical records generally supported these findings. Offspring age, study region latitude, economy type, and cesarean delivery rate accounted for some of the clinical heterogeneity. We found no data on allergic purpura.

CONCLUSIONS

Most-adjusted estimates suggest that cesarean delivery is associated with increased risks of asthma, allergic rhinitis or conjunctivitis, atopic dermatitis or eczema, food allergies, and allergic sensitization in offspring. The impact of cesarean delivery on urticaria and purpura remains uncertain.

Atopic dermatitis and food allergy: More than sensitization

The increased risk of food allergy in infants with atopic dermatitis (AD) has long been recognized; an epidemiologic phenomenon termed "the atopic march." Current literature supports the hypothesis that food antigen exposure through the disrupted skin barrier in AD leads to food antigen-specific immunoglobulin E production and food sensitization. However, there is growing evidence that inflammation in the skin drives intestinal remodeling via circulating inflammatory signals, microbiome alterations, metabolites, and the nervous system. We explore how this skin-gut axis helps to explain the link between AD and food allergy beyond sensitization.

Gut microbiome features in pediatric food allergy: a scoping review

Increasing evidence suggests that alterations in the gut microbiome (GM) play a pivotal role in the pathogenesis of pediatric food allergy (FA). This scoping review analyzes the current evidence on GM features associated with pediatric FAs and highlights the importance of the GM as a potential target of intervention for preventing and treating this common condition in the pediatric age. Following the Preferred Reporting Items for Systematic Reviews and Meta-Analysis guidelines, we searched PubMed and Embase using the keywords (gut microbiome OR dysbiosis OR gut microbiota OR microbiome signatures) AND (food allergy OR IgE-mediated food allergy OR food protein-induced allergic proctocolitis OR food protein-induced enterocolitis OR non-IgE food allergy OR cow milk allergy OR hen egg allergy OR peanut allergy OR fish allergy OR shellfish allergy OR tree nut allergy OR soy allergy OR wheat allergy OR rice allergy OR food sensitization). We included 34 studies reporting alterations in the GM in children affected by FA compared with healthy controls. The GM in pediatric FAs is characterized by a higher abundance of harmful microorganisms (e.g., Enterobacteriaceae, Clostridium sensu stricto, Ruminococcus gnavus, and Blautia spp.) and lower abundance of beneficial bacteria (e.g., Bifidobacteriaceae, Lactobacillaceae, some Bacteroides species). Moreover, we provide an overview of the mechanisms of action elicited by these bacterial species in regulating immune tolerance and of the main environmental factors that can modulate the composition and function of the GM in early life. Altogether, these data improve our knowledge of the pathogenesis of FA and can open the way to innovative diagnostic, preventive, and therapeutic strategies for managing these conditions.

The journey toward disease modification in cow milk protein allergy

Cow milk protein allergy (CMPA) is one of the most common food allergies in the pediatric age worldwide. Prevalence, persistence, and severity of this condition are on the rise, with a negative impact on the health-related quality of life of the patients and families and on the costs related to its management. Another relevant issue is that CMPA in early life may be the first stage of the "allergic march," leading to the occurrence of other atopic manifestations later in life, especially asthma, atopic eczema, urticaria, and rhinoconjunctivitis. Thus, "disease modification" options that are able to modulate the disease course of pediatric patients affected by CMPA would be very welcomed by affected families and healthcare systems. In this review, we report the most relevant progress on this topic.

The right educational environment: Oral tolerance in early life

Oral tolerance promotes the suppression of immune responses to innocuous antigen and is primarily mediated by regulatory T cell (Tregs). The development of oral tolerance begins in early life during a "window of tolerance," which occurs around weaning and is mediated by components in breastmilk. Herein, we review the factors dictating this window and how Tregs are uniquely educated in early life. In early life, the translocation of luminal antigen for Treg induction is primarily dictated by goblet cell-associated antigen passages (GAPs). GAPs in the colon are negatively regulated by maternally-derived epidermal growth factor and the microbiota, restricting GAP formation to the "periweaning" period (postnatal day 11-21 in mice, 4-6 months in humans). The induction of solid food also promotes the diversification of the bacteria such that bacterially-derived metabolites known to promote Tregs-short-chain fatty acids, tryptophan metabolites, and bile acids-peak during the periweaning phase. Further, breastmilk immunoglobulins-IgA and IgG-regulate both microbial diversity and the interaction of microbes with the epithelium, further controlling which antigens are presented to T cells. Overall, these elements work in conjunction to induce a long-lived population of Tregs, around weaning, that are crucial for maintaining homeostasis in adults.

Gut microbiome in the first 1000 days and risk for childhood food allergy

OBJECTIVE

To summarize recent data on the association between gut microbiome composition and food allergy (FA) in early childhood and highlight potential host-microbiome interactions that reinforce or abrogate oral tolerance.

DATA SOURCES

PubMed search of English-language articles related to FA, other atopic disease, and the gut microbiome in pregnancy and early childhood.

STUDY SELECTIONS

Human studies published after 2015 assessing the relationship between the gut bacteriome and virome in the first 2 years of life and FA or food sensitization development in early childhood were prioritized. Additional human studies conducted on the prenatal gut microbiome or other atopic diseases and preclinical studies are also discussed.

RESULTS

Children who developed FA harbored lower abundances of Bifidobacterium and Clostridia species and had a less mature microbiome during infancy. The early bacterial microbiome protects against FA through production of anti-inflammatory metabolites and induction of T regulatory cells and may also affect FA risk through a role in trained immunity. Infant enteric phage communities are related to childhood asthma development, though no data are available for FA. Maternal gut microbiome during pregnancy is associated with childhood FA risk, potentially through transplacental delivery of maternal bacterial metabolites, though human studies are lacking.

CONCLUSION

The maternal and infant microbiomes throughout the first 1000 days of life influence FA risk through a number of proposed mechanisms. Further large, longitudinal cohort studies using taxonomic, functional, and metabolomic analysis of the bacterial and viral microbiomes are needed to provide further insight on the host-microbe interactions underlying FA pathogenesis in childhood.

Pathogenic mechanisms in the evolution of food allergy

The early development of the neonatal immune system is profoundly influenced by exposure to dietary and microbial antigens, which shapes mucosal tolerance. Successful oral tolerance induction is crucially dependent on microbially imprinted immune cells, most notably the RORγt+ regulatory T (Treg) and antigen presenting cells and is essential for preventing food allergy (FA). The development of FA can be envisioned to result from disruptions at key checkpoints (CKPTs) that govern oral tolerance induction. These include gut epithelial sensory and effector circuits that when dysregulated promote pro-allergic gut dysbiosis. They also include microbially imprinted immune regulatory circuits that are disrupted by dysbiosis and pro-allergic immune responses unleashed by the dysregulation of the aforementioned cascades. Understanding these checkpoints is essential for developing therapeutic strategies to restore immune homeostasis in FA.

Maternal allergy-preventive diet index, offspring infant diet diversity, and childhood allergic diseases

BACKGROUND

Studies of childhood diet diversity and allergic disease have not examined additional associations with an offspring allergy-linked maternal diet index during pregnancy. We studied both associations in a pre-birth cohort.

METHODS

Offspring allergic disease diagnoses were obtained from electronic medical records. Maternal and infant diet were self-reported. Adjusted parametric Weibull time-to-event models assessed associations between maternal diet index, infant diet diversity and time to development of allergic rhinitis, atopic dermatitis, asthma, wheeze, IgE-mediated food allergy, and a combined outcome of any allergic disease except for wheeze.

RESULTS

Infant diet diversity at 1 year was associated with the risk of the combined outcome between 1 and 4 years of age (p = .002). While both maternal diet index and infant diet diversity at 1 year were associated with the risk of the combined outcome between 1 and 4 years of age (both p < .05), infant diet diversity at 1 year did not modify the association between maternal diet index and the risk of the combined outcome between 1 and 4 years of age (p = .5). The group with the lowest risk of the combined allergy outcome had higher maternal diet index and higher infant diet diversity.

CONCLUSIONS

The novel finding that both maternal diet index during pregnancy and infant diet diversity at 12 months are associated with the risk of a combined allergic disease outcome points to two targets for preventive interventions: maternal diet index scores during pregnancy and offspring diet diversity during infancy.

Association of breast milk-derived arachidonic acid-induced infant gut dysbiosis with the onset of atopic dermatitis

OBJECTIVE

The specific breast milk-derived metabolites that mediate host-microbiota interactions and contribute to the onset of atopic dermatitis (AD) remain unknown and require further investigation.

DESIGN

We enrolled 250 mother-infant pairs and collected 978 longitudinal faecal samples from infants from birth to 6 months of age, along with 243 maternal faecal samples for metagenomics. Concurrently, 239 corresponding breast milk samples were analysed for metabolomics. Animal and cellular experiments were conducted to validate the bioinformatics findings.

RESULTS

The clinical findings suggested that a decrease in daily breastfeeding duration was associated with a reduced incidence of AD. This observation inspired us to investigate the effects of breast milk-derived fatty acids. We found that high concentrations of arachidonic acid (AA), but not eicosapentaenoic acid (EPA) or docosahexaenoic acid, induced gut dysbiosis in infants. Further investigation revealed that four specific bacteria degraded mannan into mannose, consequently enhancing the mannan-dependent biosynthesis of O-antigen and lipopolysaccharide. Correlation analysis confirmed that in infants with AD, the abundance of Escherichia coli under high AA concentrations was positively correlated with some microbial pathways (eg, 'GDP-mannose-derived O-antigen and lipopolysaccharide biosynthesis'). These findings are consistent with those of the animal studies. Additionally, AA, but not EPA, disrupted the ratio of CD4/CD8 cells, increased skin lesion area and enhanced the proportion of peripheral Th2 cells. It also promoted IgE secretion and the biosynthesis of prostaglandins and leukotrienes in BALB/c mice fed AA following ovalbumin immunostimulation. Moreover, AA significantly increased IL-4 secretion in HaCaT cells costimulated with TNF-α and INF-γ.

CONCLUSIONS

This study demonstrates that AA is intimately linked to the onset of AD via gut dysbiosis.

The Early Appearance of Asthma and Its Relationship with Gut Microbiota: A Narrative Review

Asthma is, worldwide, the most frequent non-communicable disease affecting both children and adults, with high morbidity and relatively low mortality, compared to other chronic diseases. In recent decades, the prevalence of asthma has increased in the pediatric population, and, in general, the risk of developing asthma and asthma-like symptoms is higher in children during the first years of life. The "gut-lung axis" concept explains how the gut microbiota influences lung immune function, acting both directly, by stimulating the innate immune system, and indirectly, through the metabolites it generates. Thus, the process of intestinal microbial colonization of the newborn is crucial for his/her future health, and the alterations that might generate dysbiosis during the first 100 days of life are most influential in promoting hypersensitivity diseases. That is why this period is termed the "critical window". This paper reviews the published evidence on the numerous factors that can act by modifying the profile of the intestinal microbiota of the infant, thereby promoting or inhibiting the risk of asthma later in life. The following factors are specifically addressed in depth here: diet during pregnancy, maternal adherence to a Mediterranean diet, mode of delivery, exposure to antibiotics, and type of infant feeding during the first three months of life.

Development of systemic and mucosal immune responses against gut microbiota in early life and implications for the onset of allergies

The early microbial colonization of human mucosal surfaces is essential for the development of the host immune system. Already during pregnancy, the unborn child is prepared for the postnatal influx of commensals and pathogens via maternal antibodies, and after birth this protection is continued with antibodies in breast milk. During this critical window of time, which extends from pregnancy to the first year of life, each encounter with a microorganism can influence children's immune response and can have a lifelong impact on their life. For example, there are numerous links between the development of allergies and an altered gut microbiome. However, the exact mechanisms behind microbial influences, also extending to how viruses influence host-microbe interactions, are incompletely understood. In this review, we address the impact of infants' first microbial encounters, how the immune system develops to interact with gut microbiota, and summarize how an altered immune response could be implied in allergies.

The effect of cesarean delivery on the neonatal gut microbiome in an under-resourced population in the Bronx, NY, USA

BACKGROUND

Neonatal and early-life gut microbiome changes are associated with altered cardiometabolic and immune development. In this study, we explored Cesarean delivery effects on the gut microbiome in our high-risk, under-resourced Bronx, NY population.

RESULTS

Fecal samples from the Bronx MomBa Health Study (Bronx MomBa Health Study) were categorized by delivery mode (vaginal/Cesarean) and analyzed via 16 S rRNA gene sequencing at four timepoints over the first two years of life. Bacteroidota organisms, which have been linked to decreased risk for obesity and type 2 diabetes, were relatively reduced by Cesarean delivery, while Firmicutes organisms were increased. Organisms belonging to the Enterococcus genus, which have been tied to aberrant immune cell development, were relatively increased in the Cesarean delivery microbiomes.

CONCLUSION

Due to their far-reaching impact on cardiometabolic and immune functions, Cesarean deliveries in high-risk patient populations should be carefully considered.

Children's food allergy: Effects of environmental influences and antibiotic use across critical developmental windows

BACKGROUND

Increasing studies linked outdoor air pollution (OAP), indoor environmental factors (IEFs), and antibiotics use (AU) with the first wave of allergies (i.e., asthma, allergic rhinitis, and eczema), yet the role of their exposures on children's second wave of allergy (i.e., food allergy) are unknown.

OBJECTIVES

To investigate the association between exposure to OAP and IEFs and childhood doctor-diagnosed food allergy (DFA) during the pre-pregnancy, prenatal, early postnatal, and current periods, and to further explore the effect of OAP and IEFs on DFA in children co-exposed to antibiotics.

METHODS

A retrospective cohort study involving 8689 preschoolers was carried out in Changsha, China. Data on the health outcomes, antibiotic use, and home environment of each child were collected through a questionnaire. Temperature and air pollutants data were obtained from 8 and 10 monitoring stations in Changsha, respectively. Exposure levels to temperature and air pollutants at individual home addresses were calculated by the inverse distance weighted (IDW) method. Multiple logistic regression models were employed to assess the associations of childhood DFA with exposure to OAP, IEF, and AU.

RESULTS

Childhood ever doctor-diagnosed food allergy (DFA) was linked to postnatal PM10 exposure with OR (95% CI) of 1.18 (1.03-1.36), especially for CO and O3 exposure during the first year with ORs (95% CI) = 1.08 (1.00-1.16) and 1.07 (1.00-1.14), as well as SO2 exposure during the previous year with OR (95% CI) of 1.13 (1.02-1.25). The role of postnatal air pollution is more important for the risk of egg, milk and other food allergies. Renovation-related IAP (new furniture) and dampness-related indoor allergens exposures throughout all time windows significantly increased the risk of childhood DFA, with ORs ranging from 1.23 (1.03-1.46) to 1.54 (1.29-1.83). Furthermore, smoke-related IAP (environmental tobacco smoke [ETS], parental and grandparental smoking) exposure during pregnancy, first year, and previous year was related to DFA. Additionally, exposure to pet-related indoor allergens (cats) during first year and total plant-related allergens (particularly nonflowering plants) during previous year were associated with DFA. Moreover, exposure to plant-related allergy during first and previous year was specifically associated with milk allergy, while keeping cats during first year increased the risk of fruits/vegetables allergy. Life-time and early-life AU was associated with the increased risk of childhood DFA with ORs (95% CI) = 1.57 (1.32-1.87) and 1.46 (1.27-1.67), including different types food allergies except fruit/vegetable allergy.

CONCLUSIONS

Postnatal OAP, life-time and early-life IEFs and AU exposure played a vital role in the development of DFA, supporting the "fetal origin of childhood FA" hypothesis.

A Next-Generation Bacteria (Akkermansia muciniphila BAA-835) Presents Probiotic Potential Against Ovalbumin-Induced Food Allergy in Mice

Next-generation microorganisms have recently gained prominence in the scientific community, mainly due to their probiotic and postbiotic potentials. However, there are few studies that investigate these potentials in food allergy models. Therefore, the present study was designed to evaluate the probiotic potential of Akkermansia muciniphila BAA-835 in an ovalbumin food allergy (OVA) model and also analyse possible postbiotic potential. To access the probiotic potential, clinical, immunological, microbiological, and histological parameters were evaluated. In addition, the postbiotic potential was also evaluated by immunological parameters. Treatment with viable A. muciniphila was able to mitigate weight loss and serum levels of IgE and IgG1 anti-OVA in allergic mice. In addition, the ability of the bacteria to reduce the injury of the proximal jejunum, the eosinophil and neutrophil influx, and the levels of eotaxin-1, CXCL1/KC, IL4, IL6, IL9, IL13, IL17, and TNF, was clear. Furthermore, A. muciniphila was able to attenuate dysbiotic signs of food allergy by mitigating Staphylococcus levels and yeast frequency in the gut microbiota. In addition, the administration of the inactivated bacteria attenuated the levels of IgE anti-OVA and eosinophils, indicating its postbiotic effect. Our data demonstrate for the first time that the oral administration of viable and inactivated A. muciniphila BAA-835 promotes a systemic immunomodulatory protective effect in an in vivo model of food allergy to ovalbumin, which suggests its probiotic and postbiotic properties.

Transmission and Persistence of Infant Gut-Associated Bifidobacteria

Bifidobacterium infantis are the primary colonizers of the infant gut, yet scientific research addressing the transmission of the genus Bifidobacterium to infants remains incomplete. This review examines microbial reservoirs of infant-type Bifidobacterium that potentially contribute to infant gut colonization. Accordingly, strain inheritance from mother to infant via the fecal-oral route is likely contingent on the bifidobacterial strain and phenotype, whereas transmission via the vaginal microbiota may be restricted to Bifidobacterium breve. Additional reservoirs include breastmilk, horizontal transfer from the environment, and potentially in utero transfer. Given that diet is a strong predictor of Bifidobacterium colonization in early life and the absence of Bifidobacterium is observed regardless of breastfeeding, it is likely that additional factors are responsible for bifidobacterial colonization early in life.

Probiotics supplementation during pregnancy or infancy on multiple food allergies and gut microbiota: a systematic review and meta-analysis

CONTEXT

Probiotics show promise in preventing and managing food allergies, but the impact of supplementation during pregnancy or infancy on children's allergies and gut microbiota remains unclear.

OBJECTIVE

This study aimed to assess the effects of maternal or infant probiotic supplementation on food allergy risk and explore the role of gut microbiota.

DATA SOURCES

A systematic search of databases (PubMed, Cochrane Library, Embase, and Medline) identified 37 relevant studies until May 20, 2023.

DATA EXTRACTION

Two independent reviewers extracted data, including probiotics intervention details, gut microbiota analysis, and food allergy information.

DATA ANALYSIS

Probiotics supplementation during pregnancy and infancy reduced the risk of total food allergy (relative risk [RR], 0.79; 95% CI, 0.63-0.99), cow-milk allergy (RR, 0.51; 95% CI, 0.29-0.88), and egg allergy (RR, 0.57; 95% CI, 0.39-0.84). Infancy-only supplementation lowered cow-milk allergy risk (RR, 0.69; 95% CI, 0.49-0.96), while pregnancy-only had no discernible effect. Benefits were observed with over 2 probiotic species, and a daily increase of 1.8 × 109 colony-forming units during pregnancy and infancy correlated with a 4% reduction in food allergy risk. Children with food allergies had distinct gut microbiota profiles, evolving with age.

CONCLUSIONS

Probiotics supplementation during pregnancy and infancy reduces food allergy risk and correlates with age-related changes in gut microbial composition in children.

SYSTEMATIC REVIEW REGISTRATION

PROSPERO registration no. CRD42023425988.

[Specific changes in gut microbiota and short-chain fatty acid levels in infants with cow's milk protein allergy]

OBJECTIVES

To explore the changes in gut microbiota and levels of short-chain fatty acids (SCFA) in infants with cow's milk protein allergy (CMPA), and to clarify their role in CMPA.

METHODS

A total of 25 infants diagnosed with CMPA at Children's Hospital Affiliated to Zhengzhou University from August 2019 to August 2020 were enrolled as the CMPA group, and 25 healthy infants were selected as the control group. Fecal samples (200 mg) were collected from both groups and subjected to 16S rDNA high-throughput sequencing technology and liquid chromatography-mass spectrometry to analyze the changes in gut microbial composition and metabolites. Microbial diversity was analyzed in conjunction with metabolites.

RESULTS

Compared to the control group, the CMPA group showed altered gut microbial structure and significantly increased α-diversity (P<0.001). The abundance of Firmicutes, Clostridiales and Bacteroidetes was significantly decreased, while the abundance of Sphingomonadaceae, Clostridiaceae_1 and Mycoplasmataceae was significantly increased in the CMPA group compared to the control group (P<0.001). Metabolomic analysis revealed reduced levels of acetic acid, butyric acid, and isovaleric acid in the CMPA group compared to the control group, and the levels of the metabolites were positively correlated with the abundance of SCFA-producing bacteria such as Faecalibacterium and Roseburia (P<0.05).

CONCLUSIONS

CMPA infants have alterations in gut microbial structure, increased microbial diversity, and decreased levels of SCFA, which may contribute to increased intestinal inflammation.

Postpartum Maternal Anxiety Affects the Development of Food Allergy Through Dietary and Gut Microbial Diversity During Early Infancy

PURPOSE

We aimed to investigate the mediating factors between maternal anxiety and the development of food allergy (FA) in children until 2 years from birth.

METHODS

In this longitudinal cohort of 122 mother-child dyads from pregnancy to 24 months of age, we regularly surveyed maternal psychological states, infant feeding data, and allergic symptoms and collected stool samples at 6 months of age for microbiome analysis. Considering the temporal order of data collection, we investigated serial mediating effects and indirect effects among maternal anxiety, dietary diversity (DD), gut microbial diversity, and FA using structural equation modeling.

RESULTS

Among the 122 infants, 15 (12.3%) were diagnosed with FA. Increased maternal anxiety between 3 and 6 months after delivery was associated with a lower DD score. Infants with low DD at 4 months showed low gut microbial richness, which was associated with FA development. When the infants were grouped into 4 subtypes, using consensus clustering of 13 gut bacteria significantly associated with maternal anxiety and DD, Prevotella, Eubacterium, Clostridiales and Lachnospiraceae were more abundant in the group with lower FA occurrence.

CONCLUSIONS

Postpartum maternal anxiety, mediated by reduced DD and gut microbial diversity, may be a risk factor for the development of FA in infants during the first 2 years of life.

Involvement and repair of epithelial barrier dysfunction in allergic diseases

The epithelial barrier serves as a critical defense mechanism separating the human body from the external environment, fulfilling both physical and immune functions. This barrier plays a pivotal role in shielding the body from environmental risk factors such as allergens, pathogens, and pollutants. However, since the 19th century, the escalating threats posed by environmental pollution, global warming, heightened usage of industrial chemical products, and alterations in biodiversity have contributed to a noteworthy surge in allergic disease incidences. Notably, allergic diseases frequently exhibit dysfunction in the epithelial barrier. The proposed epithelial barrier hypothesis introduces a novel avenue for the prevention and treatment of allergic diseases. Despite increased attention to the role of barrier dysfunction in allergic disease development, numerous questions persist regarding the mechanisms underlying the disruption of normal barrier function. Consequently, this review aims to provide a comprehensive overview of the epithelial barrier's role in allergic diseases, encompassing influencing factors, assessment techniques, and repair methodologies. By doing so, it seeks to present innovative strategies for the prevention and treatment of allergic diseases.

Long-term exposure from perinatal life to food-grade TiO2 alters intestinal homeostasis and predisposes to food allergy in young mice

BACKGROUND

Food allergy (FA) is an inappropriate immunological response to food proteins resulting from an impaired induction of oral tolerance. Various early environmental factors can affect the establishment of intestinal homeostasis, predisposing to FA in early life. In this context, we aimed to assess the effect of chronic perinatal exposure to food-grade titanium dioxide (fg-TiO2 ), a common food additive.

METHODS

Dams were fed a control versus fg-TiO2 -enriched diet from preconception to weaning, and their progeny received the same diet at weaning. A comprehensive analysis of baseline intestinal and systemic homeostasis was performed in offspring 1 week after weaning by assessing gut barrier maturation and microbiota composition, and local and systemic immune system and metabolome. The effect of fg-TiO2 on the susceptibility of progeny to develop oral tolerance versus FA to cow's milk proteins (CMP) was performed starting at the same baseline time-point, using established models. Sensitization to CMP was investigated by measuring β-lactoglobulin and casein-specific IgG1 and IgE antibodies, and elicitation of the allergic reaction by measuring mouse mast cell protease (mMCP1) in plasma collected after an oral food challenge.

RESULTS

Perinatal exposure to fg-TiO2 at realistic human doses led to an increased propensity to develop FA and an impaired induction of oral tolerance only in young males, which could be related to global baseline alterations in intestinal barrier, gut microbiota composition, local and systemic immunity, and metabolism.

CONCLUSIONS

Long-term perinatal exposure to fg-TiO2 alters intestinal homeostasis establishment and predisposes to food allergy, with a clear gender effect.

Alterations in the gut microbiota of toddlers with cow milk protein allergy treated with a partially hydrolyzed formula containing synbiotics: A nonrandomized controlled interventional study

Formulas containing intact cow milk protein are appropriate alternatives when human milk (HM) is not feasible. However, for babies with a physician-diagnosed cow milk protein allergy (CMPA), hydrolyzed formulas are needed. We conducted a 3-month, open-label, nonrandomized concurrent controlled trial (ChiCTR2100046909) between June 2021 and October 2022 in Qingdao City, China. In this study, CMPA toddlers were fed with a partially hydrolyzed formula containing synbiotics (pHF, n = 43) and compared with healthy toddlers fed a regular intact protein formula (IF, n = 45) or HM (n = 21). The primary endpoint was weight gain; the secondary endpoints were changes in body length and head circumference of both CMPA and healthy toddlers after 3-month feeding; and the exploratory outcomes were changes in gut microbiota composition. After 3 months, there were no significant group differences for length-for-age, weight-for-age, or head circumference-for-age Z scores. In the gut microbiota, pHF feeding increased its richness and diversity, similar to those of IF-fed and HM-fed healthy toddlers. Compared with healthy toddlers, the toddlers with CMPA showed an increased abundance of phylum Bacteroidota, Firmicutes, class Clostridia, and Bacteroidia, and a decreased abundance of class Negativicutes, while pHF feeding partly eliminated these original differences. Moreover, pHF feeding increased the abundance of short-chain fatty acid producers. Our data suggested that this pHF partly simulated the beneficial effects of HM and shifted the gut microbiota of toddlers with CMPA toward that of healthy individuals. In conclusion, this synbiotic-containing pHF might be an appropriate alternative for toddlers with CMPA.

Probiotics in Infancy and Childhood for Food Allergy Prevention and Treatment

Food allergy represents a failure of oral tolerance mechanisms to dietary antigens. Over the past few years, food allergies have become a growing public health problem worldwide. Gut microbiota is believed to have a significant impact on oral tolerance to food antigens and in initiation and maintenance of food allergies. Therefore, probiotics have also been proposed in this field as a possible strategy for modulating both the gut microbiota and the immune system. In recent years, results from preclinical and clinical studies suggest a promising role for probiotics in food allergy prevention and treatment. However, future studies are needed to better understand the mechanisms of action of probiotics in food allergies and to design comparable study protocols using specific probiotic strains, defined doses and exposure times, and longer follow-up periods.

Circulating microbiome analysis in patients with perioperative anaphylaxis

Background

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

Methods

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

Results

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

Conclusion

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

The Role of Gut Microbiota and Leaky Gut in the Pathogenesis of Food Allergy

Food allergy (FA) is a growing public health concern, with an increasing prevalence in Western countries. Increasing evidence suggests that the balance of human gut microbiota and the integrity of our intestinal barrier may play roles in the development of FA. Environmental factors, including industrialization and consumption of highly processed food, can contribute to altering the gut microbiota and the intestinal barrier, increasing the susceptibility to allergic sensitization. Compositional and functional alterations to the gut microbiome have also been associated with FA. In addition, increased permeability of the gut barrier allows the translocation of allergenic molecules, triggering Th2 immune responses. Preclinical and clinical studies have highlighted the potential of probiotics, prebiotics, and postbiotics in the prevention and treatment of FA through enhancing gut barrier function and promoting the restoration of healthy gut microbiota. Finally, fecal microbiota transplantation (FMT) is now being explored as a promising therapeutic strategy to prevent FA in both experimental and clinical studies. In this review article, we aim to explore the complex interplay between intestinal permeability and gut microbiota in the development of FA, as well as depict potential therapeutic strategies.

Factors by which global warming worsens allergic disease

Increased use of fossil fuels has led to global warming with concomitant increases in the severity and frequency of extreme weather events such as wildfires and sand and dust storms. These changes have led to increases in air pollutants such as particulate matter and greenhouse gases. Global warming is also associated with increases in pollen season length and pollen concentration. Particulate matter, greenhouse gases, and pollen synergistically increase the incidence and severity of allergic diseases. Other indirect factors such as droughts, flooding, thunderstorms, heat waves, water pollution, human migration, deforestation, loss of green space, and decreasing biodiversity (including microbial diversity) also affect the incidence and severity of allergic disease. Global warming and extreme weather events are expected to increase in the coming decades, and further increases in allergic diseases are expected, exacerbating the already high health care burden associated with these diseases. There is an urgent need to mitigate and adapt to the effects of climate change to improve human health. Human health and planetary health are connected and the concept of One Health, which is an integrated, unifying approach to balance and optimize the health of people, animals, and the environment needs to be emphasized. Clinicians are trusted members of the community, and they need to take a strong leadership role in educating patients on climate change and its adverse effects on human health. They also need to advocate for policy changes that decrease the use of fossil fuels and increase biodiversity and green space to enable a healthier and more sustainable future.

Early-life gut microbiota in food allergic children and its impact on the development of allergic disease

BACKGROUND

The prevalence of food allergies (FA) has been steadily increasing over 2 to 3 decades, showing diverse symptoms and rising severity. These long-term outcomes affect children's growth and development, possibly linking to inflammatory bowel disease. However, the cause remains unclear. Previous studies reveal that early infancy significantly impacts FA development through gut microbiota. Yet, a consistent view on dysbiosis characteristics and its connection to future allergies is lacking. We explored how early-life gut microbiota composition relates to long-term clinical signs in children with FA through longitudinal research.

METHODS

We employed high-throughput 16S rDNA gene sequencing to assess gut microbiota composition in early-life FA children in southern Zhejiang. Follow-up of clinical manifestations over 2 years allowed us to analyze the impact of early-life gut microbiota dysbiosis on later outcomes.

RESULTS

While the diversity of gut microbiota in FA children remained stable, there were shifts in microbiota abundance. Abundant Akkermansia, Parabacteroides, Blautia, and Escherichia-Shigella increased, while Bifidobacterium and Clostridium decreased. After 2 years, two of ten FA children still showed symptoms. These two cases exhibited increased Escherichia-Shigella and reduced Bifidobacterium during early childhood. The other eight cases experienced symptom remission.

CONCLUSIONS

Our study suggests that FA and its prognosis might not correlate with early-life gut microbiota diversity. Further experiments are needed due to the small sample size, to confirm these findings.

Short-chain fatty acid - A critical interfering factor for allergic diseases

Allergy is a growing global public health problem with a high socio-economic impact. The incidence of allergic diseases is increasing year by year, which has attracted more and more attention. In recent years, a number of epidemiological investigations and gut microbiota studies have shown that gut microbiota dysbiosis is associated with an increased prevalence of various allergic diseases, such as food allergy, asthma, allergic rhinitis, and atopic dermatitis. However, the underlying mechanisms are complex and have not been fully clarified. Metabolites are one of the main ways in which the gut microbiota functions. Short-chain fatty acids (SCFAs) are the main metabolites of intestinal flora fermentation and are beneficial to human health. Studies have shown that SCFAs play an important role in maintaining intestinal homeostasis and regulating immune responses by recognizing receptors and inhibiting histone deacetylases, and are key molecules involved in the occurrence and development of allergic diseases. In addition, research on the regulation of gut microbiota and the application of SCFAs in the treatment of allergic diseases is also emerging. This article reviews the clinical and experimental evidence on the correlation between SCFAs and allergic diseases and the potential mechanisms by which SCFAs regulate allergic diseases. Furthermore, SCFAs as therapeutic targets for allergic diseases are also summarized and prospected.

Early-life interactions between the microbiota and immune system: impact on immune system development and atopic disease

Prenatal and early postnatal life represent key periods of immune system development. In addition to genetics and host biology, environment has a large and irreversible role in the immune maturation and health of an infant. One key player in this process is the gut microbiota, a diverse community of microorganisms that colonizes the human intestine. The diet, environment and medical interventions experienced by an infant determine the establishment and progression of the intestinal microbiota, which interacts with and trains the developing immune system. Several chronic immune-mediated diseases have been linked to an altered gut microbiota during early infancy. The recent rise in allergic disease incidence has been explained by the 'hygiene hypothesis', which states that societal changes in developed countries have led to reduced early-life microbial exposures, negatively impacting immunity. Although human cohort studies across the globe have established a correlation between early-life microbiota composition and atopy, mechanistic links and specific host-microorganism interactions are still being uncovered. Here, we detail the progression of immune system and microbiota maturation in early life, highlight the mechanistic links between microbes and the immune system, and summarize the role of early-life host-microorganism interactions in allergic disease development.

The First 1000 Days of Life: How Changes in the Microbiota Can Influence Food Allergy Onset in Children

BACKGROUND

Allergic disease, including food allergies (FA)s, has been identified as a major global disease. The first 1000 days of life can be a "window of opportunity" or a "window of susceptibility", during which several factors can predispose children to FA development. Changes in the composition of the gut microbiota from pregnancy to infancy may play a pivotal role in this regard: some bacterial genera, such as Lactobacillus and Bifidobacterium, seem to be protective against FA development. On the contrary, Clostridium and Staphylococcus appear to be unprotective.

METHODS

We conducted research on the most recent literature (2013-2023) using the PubMed and Scopus databases. We included original papers, clinical trials, meta-analyses, and reviews in English. Case reports, series, and letters were excluded.

RESULTS

During pregnancy, the maternal diet can play a fundamental role in influencing the gut microbiota composition of newborns. After birth, human milk can promote the development of protective microbial species via human milk oligosaccharides (HMOs), which play a prebiotic role. Moreover, complementary feeding can modify the gut microbiota's composition.

CONCLUSIONS

The first two years of life are a critical period, during which several factors can increase the risk of FA development in genetically predisposed children.

Food Allergens: When Friends Become Foes-Caveats and Opportunities for Oral Immunotherapy Based on Deactivation Methods

Food allergies represent a serious health concern and, since the 1990s, they have risen gradually in high-income countries. Unfortunately, the problem is complex because genetic, epigenetic, and environmental factors may be collectively involved. Prevention and diagnoses have not yet evolved into efficacious therapies. Identification and control of allergens present in edible substances hold promise for multi-purpose biomedical approaches, including oral immunotherapy. This review highlights recent studies and methods to modify the otherwise innocuous native proteins in most subjects, and how oral treatments targeting immune responses could help cancel out the potential risks in hypersensitive individuals, especially children. We have focused on some physical methods that can easily be conducted, along with chemo-enzymatic modifications of allergens by means of peptides and phytochemicals in particular. The latter, accessible from naturally-occurring substances, provide an added value to hypoallergenic matrices employing vegetal wastes, a point where food chemistry meets sustainable goals as well.

Sea cucumber chondroitin sulfate polysaccharides attenuate OVA-induced food allergy in BALB/c mice associated with gut microbiota metabolism and Treg cell differentiation

Previous research studies have shown that sulfated polysaccharides can inhibit food allergy, but the detailed mechanism remains largely unknown. In this study, RBL-2H3 cells were used to compare the anti-allergic activities of four sulfated polysaccharides, and an ovalbumin (OVA)-sensitized allergic mouse experiment was used to explore their desensitization effect, with regard to the alteration in gut microbiota and immune cell differentiation. Compared with the shark, bovine and porcine chondroitin sulfate, sea cucumber chondroitin sulfate (SCCS) significantly inhibited the degranulation of RBL-2H3 cells. SCCS reduced allergic symptoms and protected the jejunum from injury in mice. Furthermore, SCCS increased the relative abundance of Lachnospiraceae NK4A136, decreased the relative proportion of Prevotellaceae NK3B31, and up-regulated the secretion of short chain fatty acids such as butyric acid in the feces, resulting in an increase in the mucin 2 (MUC2) secretion by goblet cells HT-29. Meanwhile, SCCS induced the differentiation of regulatory T cells in the mesenteric lymph nodes of mice. This study provides a deeper understanding of the functioning mechanism of SCCS in alleviating food allergy and may guide the development and production of anti-allergy active ingredients.

Assessment of infant outgrowth of cow's milk allergy in relation to the faecal microbiome and metaproteome

Previous studies provide evidence for an association between modifications of the gut microbiota in early life and the development of food allergies. We studied the faecal microbiota composition (16S rRNA gene amplicon sequencing) and faecal microbiome functionality (metaproteomics) in a cohort of 40 infants diagnosed with cow's milk allergy (CMA) when entering the study. Some of the infants showed outgrowth of CMA after 12 months, while others did not. Faecal microbiota composition of infants was analysed directly after CMA diagnosis (baseline) as well as 6 and 12 months after entering the study. The aim was to gain insight on gut microbiome parameters in relation to outgrowth of CMA. The results of this study show that microbiome differences related to outgrowth of CMA can be mainly identified at the taxonomic level of the 16S rRNA gene, and to a lesser extent at the protein-based microbial taxonomy and functional protein level. At the 16S rRNA gene level outgrowth of CMA is characterized by lower relative abundance of Lachnospiraceae at baseline and lower Bacteroidaceae at visit 12 months.

The future of food allergy: Challenging existing paradigms of clinical practice

The field of food allergy has seen tremendous change over the past 5-10 years with seminal studies redefining our approach to prevention and management and novel testing modalities in the horizon. Early introduction of allergenic foods is now recommended, challenging the previous paradigm of restrictive avoidance. The management of food allergy has shifted from a passive avoidance approach to active interventions that aim to provide protection from accidental exposures, decrease allergic reaction severity and improve the quality of life of food-allergic patients and their families. Additionally, novel diagnostic tools are making their way into clinical practice with the goal to reduce the need for food challenges and assist physicians in the-often complex-diagnostic process. With all the new developments and available choices for diagnosis, prevention and therapy, shared decision-making has become a key part of medical consultation, enabling patients to make the right choice for them, based on their values and preferences. Communication with patients has also become more complex over time, as patients are seeking advice online and through social media, but the information found online may be outdated, incorrect, or lacking in context. The role of the allergist has evolved to embrace all the above exciting developments and provide patients with the optimal care that fits their needs. In this review, we discuss recent developments as well as the evolution of the field of food allergy in the next decade.

Recent advances in cellular and molecular mechanisms of IgE-mediated food allergy

Food allergy is a public health issue the prevalence of which is steadily increasing. New discoveries have contributed to the understanding of the molecular and cellular mechanisms that lead to IgE-mediated food allergy. Novel scientific findings have defined roles for specific cell types, such as T follicular helper cells, in induction of high-affinity IgE by B cells. Also, not only mast cells and basophils contribute to food anaphylaxis, but also other cell types, such as neutrophils and macrophages. Elucidation of mechanisms involved in sensitization to food allergens through organs including the skin is key to deepening our understanding of the "dual exposure" hypothesis, which suggests that allergic sensitization is mainly acquired through inflamed skin while the oral route induces tolerance. This review considers the latest scientific knowledge about the molecular and cellular mechanisms of IgE-mediated food allergy. It reveals crucial components involved in the sensitization and elicitation phases and emerging approaches in anaphylaxis pathophysiology.

Impact of local human microbiota on the allergic diseases: Organ-organ interaction

The homogeneous impact of local dysbiosis on the development of allergic diseases in the same organ has been thoroughly studied. However, much less is known about the heterogeneous influence of dysbiosis within one organ on allergic diseases in other organs. A comprehensive analysis of the current scientific literature revealed that most of the relevant publications focus on only three organs: gut, airways, and skin. Moreover, the interactions appear to be mainly unidirectional, that is, dysbiotic conditions of the gut being associated with allergic diseases of the airways and the skin. Similar to homogeneous interactions, early life appears to be not only a crucial period for the formation of the microbiota in one organ but also for the later development of allergic diseases in other organs. In particular, we were able to identify a number of specific bacterial and fungal species/genera in the intestine that were repeatedly associated in the literature with either increased or decreased allergic diseases of the skin, like atopic dermatitis, or the airways, like allergic rhinitis and asthma. The reported studies indicate that in addition to the composition of the microbiome, also the relative abundance of certain microbial species and the overall diversity are associated with allergic diseases of the corresponding organs. As anticipated for human association studies, the underlying mechanisms of the organ-organ crosstalk could not be clearly resolved yet. Thus, further work, in particular experimental animal studies are required to elucidate the mechanisms linking dysbiotic conditions of one organ to allergic diseases in other organs.

Alteration of taste perception, food neophobia and oral microbiota composition in children with food allergy

Currently, the mechanisms underlying sensory perception and sensory performance in children with food allergies are far from being understood. As well, only recently, single research afforded the oral host-commensal milieu, addressing oral microbial communities in children with peanut allergies. To bridge the current gaps in knowledge both in the sensory and microbial fields, a psychophysiological case-control study was performed in allergic children (n = 29) and a healthy sex-age-matched control group (n = 30). Taste perception, food neophobia, and liking were compared in allergic and non-allergic children. The same subjects were characterized for their oral microbiota composition by addressing saliva to assess whether specific profiles were associated with the loss of oral tolerance in children with food allergies. Our study evidenced an impaired ability to correctly identify taste qualities in the allergic group compared to controls. These results were also consistent with anatomical data related to the fungiform papillae on the tongue, which are lower in number in the allergic group. Furthermore, distinct oral microbial profiles were associated with allergic disease, with significant down-representations of the phylum Firmicutes and of the genera Veillonella spp., Streptococcus spp., Prevotella spp., and Neisseria spp. For the first time, this study emphasizes the link between sensory perception and food allergy, which is a novel and whole-organism view of this pathology. Our data indicated that an impaired taste perception, as regards both functionality and physiologically, was associated with food allergy, which marginally influences the food neophobia attitude. It is also accompanied by compositional shifts in oral microbiota, which is, in turn, another actor of this complex interplay and is deeply interconnected with mucosal immunity. This multidisciplinary research will likely open exciting new approaches to therapeutic interventions.

Microbial transmission, colonisation and succession: from pregnancy to infancy

The microbiome has been proven to be associated with many diseases and has been used as a biomarker and target in disease prevention and intervention. Currently, the vital role of the microbiome in pregnant women and newborns is increasingly emphasised. In this review, we discuss the interplay of the microbiome and the corresponding immune mechanism between mothers and their offspring during the perinatal period. We aim to present a comprehensive picture of microbial transmission and potential immune imprinting before and after delivery. In addition, we discuss the possibility of in utero microbial colonisation during pregnancy, which has been highly debated in recent studies, and highlight the importance of the microbiome in infant development during the first 3 years of life. This holistic view of the role of the microbial interplay between mothers and infants will refine our current understanding of pregnancy complications as well as diseases in early life and will greatly facilitate the microbiome-based prenatal diagnosis and treatment of mother-infant-related diseases.

Food allergy prevention: Where are we in 2023?

Food allergy prevention involves recommendations to the maternal diet during pregnancy and breast feeding, early life feeding and introduction of solid foods. Pregnant and breastfeeding women are not recommended to exclude any food allergens from their diet, but data are lacking to support active consumption of food allergens for prevention of food allergy. Breastfeeding is recommended for the many health benefits to the mother and child but has not shown any association with reduction in childhood food allergies. There is currently no recommendation regarding the use of any infant formula for allergy prevention, including the use of partially or extensively hydrolyzed formulas. Once the introduction of solid food commences, based on randomized controlled trials, it is advised to actively introduce peanuts and egg early into the infant diet and continue with consumption of these. Although there are limited data with respect to other major food allergens and whether early introduction may prevent allergy development, there is no need to delay the introduction of these allergens into the infant diet. Interpreting food allergen consumption in the context of cultural food practices has not been studied, but it makes sense to introduce the infant to family foods by 1 year of age. Consumption of foods typical of the Western diet and foods high in advanced glycation end products may be associated with an increase in food allergies. Similarly, intake of micronutrients, such as vitamin D and omega-3 fatty acids in both the maternal and infant diet, needs further clarification in the context of food allergy prevention.

25 Years of translational research in the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC)

The Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) mother-child cohorts have provided a foundation of 25 years of research on the origins, prevention, and natural history of childhood asthma and related disorders. COPSAC's approach is characterized by clinical translational research with longitudinal deep phenotyping and exposure assessments from pregnancy, in combination with multi-omic data layers and embedded randomized controlled trials. One trial showed that fish oil supplementation during pregnancy prevented childhood asthma and identified pregnant women with the highest benefits from supplementation, thereby creating the potential for personalized prevention. COPSAC revealed that airway colonization with pathogenic bacteria in early life is associated with an increased risk of asthma. Further, airway bacteria were shown to be a trigger of acute asthma-like symptoms, with benefit from antibiotic treatment. COPSAC identified an immature gut microbiome in early life as a risk factor for asthma and allergy and further demonstrated that asthma can be predicted by infant lung function. At a molecular level, COPSAC has identified novel susceptibility genes, early immune deviations, and metabolomic alterations associated with childhood asthma. Thus, the COPSAC research program has enhanced our understanding of the processes causing childhood asthma and has suggested means of personalized prevention and treatment.

Natural Green Spaces, Sensitization to Allergens, and the Role of Gut Microbiota during Infancy

The environment plays an instrumental role in the developmental origins of health and disease. Protective features of the environment in the development of asthma and atopy have been insufficiently studied. We used data from the CHILD (Canadian Healthy Infant Longitudinal Development) Cohort Study to examine relationships between living near natural green spaces in early infancy in Edmonton, AB, Canada and the development of atopic sensitization at 1 year and 3 years of age in a cohort of 699 infants, and whether these associations were mediated by infant gut microbiota (measured using 16s V4 amplicon sequencing) at 4 months. The Urban Planning Land Vegetation Index (uPLVI) map of the City of Edmonton was used to assess infants' exposure to natural spaces based on their home postal codes, and atopic sensitization was assessed using skin prink testing (SPTs) for common food and inhalant allergens. Our findings suggest there is a protective effect of natural green space proximity on the development of multiple inhalant atopic sensitizations at 3 years (odds ratio = 0.28 [95% CI 0.09, 0.90]). This relationship was mediated by changes to Actinobacteria diversity in infant fecal samples taken at 4 months. We also found a positive association between nature proximity and sensitization to at least one food or inhaled allergen; this association was not mediated by gut microbiota. Together, these findings underscore the importance of promoting natural urban greenspace preservation to improve child health by reducing atopic disease susceptibility. IMPORTANCE Our findings highlight the importance of preserving natural green space in urban settings to prevent sensitization to environmental allergens and promote early-life gut microbiota pathways to this health benefit. These findings support a mediating role of gut microbiome compositions in health and disease susceptibility. This study used unique, accurate, and comprehensive methodology to classify natural space exposure via a high-resolution topographical map of foliage subtypes within the City of Edmonton limits. These methods are improvements from other methods previously used to classify natural space exposure, such as the normalized density vegetation index from satellite imagery, which is not able to distinguish anthropogenic from green space. The use of these methods and the associations found between natural green space exposure and atopic sensitization outcomes support their use in future studies. Our findings also provide many avenues for future research including longer term follow up of this cohort and investigation of a causal role of reduced Actinobacteria diversity on atopic sensitization development.

Longitudinal profiles of the fecal metabolome during the first 2 years of life

During the first 2 years of life, the infant gut microbiome is rapidly developing, and gut bacteria may impact host health through the production of metabolites that can have systemic effects. Thus, the fecal metabolome represents a functional readout of gut bacteria. Despite the important role that fecal metabolites may play in infant health, the development of the infant fecal metabolome has not yet been thoroughly characterized using frequent, repeated sampling during the first 2 years of life. Here, we described the development of the fecal metabolome in a cohort of 101 Latino infants with data collected at 1-, 6-, 12-, 18-, and 24-months of age. We showed that the fecal metabolome is highly conserved across time and highly personalized, with metabolic profiles being largely driven by intra-individual variability. Finally, we also identified several novel metabolites and metabolic pathways that changed significantly with infant age, such as valerobetaine and amino acid metabolism, among others.

Continuous Rather Than Solely Early Farm Exposure Protects From Hay Fever Development

BACKGROUND

An important window of opportunity for early-life exposures has been proposed for the development of atopic eczema and asthma.

OBJECTIVE

However, it is unknown whether hay fever with a peak incidence around late school age to adolescence is similarly determined very early in life.

METHODS

In the Protection against Allergy-Study in Rural Environments (PASTURE) birth cohort potentially relevant exposures such as farm milk consumption and exposure to animal sheds were assessed at multiple time points from infancy to age 10.5 years and classified by repeated measure latent class analyses (n = 769). Fecal samples at ages 2 and 12 months were sequenced by 16S rRNA. Hay fever was defined by parent-reported symptoms and/or physician's diagnosis of hay fever in the last 12 months using questionnaires at 10.5 years.

RESULTS

Farm children had half the risk of hay fever at 10.5 years (adjusted odds ratio [aOR] 0.50; 95% CI 0.31-0.79) than that of nonfarm children. Whereas early life events such as gut microbiome richness at 12 months (aOR 0.66; 95% CI 0.46-0.96) and exposure to animal sheds in the first 3 years of life (aOR 0.26; 95% CI 0.06-1.15) were determinants of hay fever, the continuous consumption of farm milk from infancy up to school age was necessary to exert the protective effect (aOR 0.35; 95% CI 0.17-0.72).

CONCLUSIONS

While early life events determine the risk of subsequent hay fever, continuous exposure is necessary to achieve protection. These findings argue against the notion that only early life exposures set long-lasting trajectories.

The maternal prenatal and offspring early-life gut microbiome of childhood asthma phenotypes

BACKGROUND

The infant fecal microbiome is known to impact subsequent asthma risk, but the environmental exposures impacting this association, the role of the maternal microbiome, and how the microbiome impacts different childhood asthma phenotypes are unknown.

METHODS

Our objective was to identify associations between features of the prenatal and early-life fecal microbiomes and child asthma phenotypes. We analyzed fecal 16 s rRNA microbiome profiling and fecal metabolomic profiling from stool samples collected from mothers during the third trimester of pregnancy (n = 120) and offspring at ages 3-6 months (n = 265), 1 (n = 436) and 3 years (n = 506) in a total of 657 mother-child pairs participating in the Vitamin D Antenatal Asthma Reduction Trial. We used clinical data from birth to age 6 years to characterize subjects with asthma as having early, transient or active asthma phenotypes. In addition to identifying specific genera that were robustly associated with asthma phenotypes in multiple covariate-adjusted models, we clustered subjects by their longitudinal microbiome composition and sought associations between fecal metabolites and relevant microbiome and clinical features.

RESULTS

Seven maternal and two infant fecal microbial taxa were robustly associated with at least one asthma phenotype, and a longitudinal gut microenvironment profile was associated with early asthma (Fisher exact test p = .03). Though mode of delivery was not directly associated with asthma, we found substantial evidence for a pathway whereby cesarean section reduces fecal Bacteroides and microbial sphingolipids, increasing susceptibility to early asthma.

CONCLUSION

Overall, our results suggest that the early-life, including prenatal, fecal microbiome modifies risk of asthma, especially asthma with onset by age 3 years.

Gut Microbiome Proteomics in Food Allergies

Food allergies (FA) have dramatically increased in recent years, particularly in developed countries. It is currently well-established that food tolerance requires the strict maintenance of a specific microbial consortium in the gastrointestinal (GI) tract microbiome as alterations in the gut microbiota can lead to dysbiosis, causing inflammation and pathogenic intestinal conditions that result in the development of FA. Although there is currently not enough knowledge to fully understand how the interactions between gut microbiota, host responses and the environment cause food allergies, recent advances in '-omics' technologies (i.e., proteomics, genomics, metabolomics) and in approaches involving systems biology suggest future headways that would finally allow the scientific understanding of the relationship between gut microbiome and FA. This review summarizes the current knowledge in the field of FA and insights into the future advances that will be achieved by applying proteomic techniques to study the GI tract microbiome in the field of FA and their medical treatment. Metaproteomics, a proteomics experimental approach of great interest in the study of GI tract microbiota, aims to analyze and identify all the proteins in complex environmental microbial communities; with shotgun proteomics, which uses liquid chromatography (LC) for separation and tandem mass spectrometry (MS/MS) for analysis, as it is the most promising technique in this field.

Impact of Cesarean Delivery and Breastfeeding on Secretory Immunoglobulin A in the Infant Gut Is Mediated by Gut Microbiota and Metabolites

How gut immunity in early life is shaped by birth in relation to delivery mode, intrapartum antibiotic prophylaxis (IAP) and labor remains undetermined. We aimed to address this gap with a study of secretory Immunoglobulin A (SIgA) in the infant gut that also tested SIgA-stimulating pathways mediated by gut microbiota and metabolites. Among 1017 Canadian full-term infants, gut microbiota of fecal samples collected at 3 and 12 months were profiled using 16S rRNA sequencing; C. difficile was quantified by qPCR; fecal metabolites and SIgA levels were measured by NMR and SIgA enzyme-linked immunosorbent assay, respectively. We assessed the putative causal relationships from birth events to gut microbiota and metabolites, and ultimately to SIgA, in statistical sequential mediation models, adjusted for maternal gravida status in 551 infants. As birth mode influences the ability to breastfeed, the statistical mediating role of breastfeeding status and milk metabolites was also evaluated. Relative to vaginal birth without maternal IAP, cesarean section (CS) after labor was associated with reduced infant gut SIgA levels at 3 months (6.27 vs. 4.85 mg/g feces, p < 0.05); this association was sequentially mediated through gut microbiota and metabolites of microbial or milk origin. Mediating gut microbiota included Enterobacteriaceae, C. difficile, and Streptococcus. The milk or microbial metabolites in CS-SIgA mediating pathways were galactose, fucose, GABA, choline, lactate, pyruvate and 1,2-propanediol. This cohort study documented the impact of birth on infant gut mucosal SIgA. It is the first to characterize gut microbe-metabolite mediated pathways for early-life SIgA maturation, pathways that require experimental verification.

The role of breastfeeding as a protective factor against the development of the immune-mediated diseases: A systematic review

INTRODUCTION

Breast milk is rich in nutrients and immunological factors capable of protecting infants against various immunological diseases and disorders. The current systematic review has been framed with the objective of studying the role of breastfeeding as a protective factor against the development of immune-mediated diseases.

METHODS

The database and website searches were performed using PubMed, PubMed Central, Nature, Springer, Nature, Web of Science, and Elsevier. The studies were scrutinized based on the nature of participants and the nature of disease considered. The search was restricted to infants with immune-mediated diseases such as diabetes mellitus, allergic conditions, diarrhoea, and rheumatoid arthritis.

RESULTS

We have included 28 studies, out of which seven deal with diabetes mellitus, two rheumatoid arthritis, five studies about Celiac Disease, twelve studies about allergic/ asthma/wheezing conditions and one study on each of the following diseases: neonatal lupus erythematosus and colitis.

DISCUSSION

Based on our analysis, breastfeeding in association with the considered diseases was found to be positive. Breastfeeding is involved as protective factor against various diseases. The role of breastfeeding in the prevention of diabetes mellitus has been found to be significantly higher than for other diseases.