Patterns of immune development in urban preschoolers with recurrent wheeze and/or atopy

Farm animal exposure, respiratory illnesses, and nasal cell gene expression

BACKGROUND

Farm exposures in early life reduce the risks for childhood allergic diseases and asthma. There is less information about how farm exposures relate to respiratory illnesses and mucosal immune development.

OBJECTIVE

We hypothesized that children raised in farm environments have a lower incidence of respiratory illnesses over the first 2 years of life than nonfarm children. We also analyzed whether farm exposures or respiratory illnesses were related to patterns of nasal cell gene expression.

METHODS

The Wisconsin Infant Study Cohort included farm (n = 156) and nonfarm (n = 155) families with children followed to age 2 years. Parents reported prenatal farm and other environmental exposures. Illness frequency and severity were assessed using illness diaries and periodic surveys. Nasopharyngeal cell gene expression in a subset of 64 children at age 2 years was compared to farm exposure and respiratory illness history.

RESULTS

Farm versus nonfarm children had nominally lower rates of respiratory illnesses (rate ratio 0.82 [95% CI, 0.69, 0.97]) with a stepwise reduction in illness rates in children exposed to 0, 1, or ≥2 animal species, but these trends were nonsignificant in a multivariable model. Farm exposures and preceding respiratory illnesses were positively related to nasal cell gene signatures for mononuclear cells and innate and antimicrobial responses.

CONCLUSIONS

Maternal and infant exposure to farms and farm animals was associated with nonsignificant trends for reduced respiratory illnesses. Nasal cell gene expression in a subset of children suggests that farm exposures and respiratory illnesses in early life are associated with distinct patterns of mucosal immune expression.

Advancing Understanding of Childhood Asthma: Lessons Learned from Birth Cohort Studies

Asthma and allergies are some of the most common chronic disorders affecting children, the prevalence of which has been increasing in countries and regions undergoing rapid development like China. To curb the rising tide of allergies and safeguard the health of future generations, it is of critical importance to understand how asthma inception is influenced by factors acting at different life stages. Birth cohorts represent a powerful tool to investigate the temporal sequence of exposures along the natural course of asthma. We examined recent evidence on birth cohort studies of asthma and allergic diseases and evaluated their strengths and weaknesses. Essential elements for a successful birth cohort are proposed to further elucidate asthma etiology and pathogenies. Initiating new cohorts in understudied populations with the application of advanced analytical approaches will be needed. Moreover, fostering collaborative networks using standardized methodologies should be prioritized to enable integration of findings across diverse cohorts. There remains an urgent and unmet need to further translate the seminal findings from asthma birth cohort studies into targeted primary prevention strategies to eradicate the disease.

Asthma Management in Children

Asthma is a common, complex heterogeneous disease often beginning in early life and is characterized by reversible airflow obstruction. The phenotypic differences that exist in children with asthma may impact underlying comorbid conditions and pharmacologic treatment choices. Prenatal factors for increased risk of asthma could include maternal diet and the maternal microbiome. Evidence also suggests that postnatal microbial exposures and colonization contribute to the risk of allergic diseases and asthma. After confirming the diagnosis, asthma management in children centers on 3 broad areas: pharmacologic treatment, treatment of underlying comorbidities, and education of the patient and caregivers on the importance of adherence and device technique. Moreover, social determinants of health significantly impact on symptom burden and treatment response.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Pathogens and Pathogenesis in Wheezing Diseases in Children Under 6

Few studies have comprehensively assessed the roles of cytokine production in wheezing pathogenesis. Therefore, we undertook this study to determine the association between wheezing episodes and cytokines, and to provide further information on this topic. Firstly, we retrospectively collected I176 children, including 122 subjects with first wheezing and 54 subjects with recurrent wheezing, to analyze the etiology and clinical characteristics of children with wheezing diseases. Then, we collected 52 children with wheezing diseases and 25 normal controls to detect the expression of interferon-γ (IFN-γ), interleukin-4 (IL-4), IFN-γ/IL-4, IL-17A, IL-17E, IgE, matrix metalloproteinase-3 (MMP-3), and MMP-9 in serum or plasma. The results showed that boys under 3 years old with history of allergies were more likely to develop wheezing diseases. In our cohort, M. pneumoniae caused a greater proportion of wheezing in children than expected. The expression of IgE [18.80 (13.65-31.00) vs. 17.9 (10.15-21.60)], IL-4 [24.00 (24.00-48.00) vs. 23.00 (9.50-27.00)], IFN-γ [70.59 (41.63-116.46) vs. 49.83 (29.58-81.74)], MMP3 [53.40 (20.02-128.2) vs. 30.90 (13.80-50.95)], MMP9 [148.10 (99.30-276.10) vs. 122.10 (82.20-162.35)], IL-17A [80.55 (54.46-113.08) vs. 61.11 (29.43-93.87)], and IL-17E [1.75 (0.66-2.77) vs. 1.19 (0.488-2.1615)] were significantly increased in the wheezing group (p<0.05) compared to normal controls, while the level of IFN-γ/IL-4 had no significant difference between the two groups (1.24 ± 1.88 vs 0.68 ± 0.74, p>0.05). There was altered cytokine production in children with wheezing diseases which was quite similar to asthma pathogenesis. Sex, age, pathogen infection, and inflammation in our study were also risk factors for wheezing diseases.

Cord blood group 2 innate lymphoid cells are associated with lung function at 6 weeks of age

Objective

Offspring born to mothers with asthma in pregnancy are known to have lower lung function which tracks with age. Human group 2 innate lymphoid cells (ILC2) accumulate in foetal lungs, at 10‐fold higher levels compared to adult lungs. However, there are no data on foetal ILC2 numbers and the association with respiratory health outcomes such as lung function in early life. We aimed to investigate cord blood immune cell populations from babies born to mothers with asthma in pregnancy.

Methods

Cord blood from babies born to asthmatic mothers was collected, and cells were stained in whole cord blood. Analyses were done using traditional gating approaches and computational methodologies (t‐distributed stochastic neighbour embedding and PhenoGraph algorithms). At 6 weeks of age, the time to peak tidal expiratory flow as a percentage of total expiratory flow time (tPTEF/tE%) was determined as well as Lung Clearance Index (LCI), during quiet natural sleep.

Results

Of 110 eligible infants (March 2017 to November 2019), 91 were successfully immunophenotyped (82.7%). Lung function was attempted in 61 infants (67.0%), and 43 of those infants (70.5% of attempted) had technically acceptable tPTEF/tE% measurements. Thirty‐four infants (55.7% of attempted) had acceptable LCI measurements. Foetal ILC2 numbers with increased expression of chemoattractant receptor‐homologous molecule (CRTh2), characterised by two distinct analysis methodologies, were associated with poorer infant lung function at 6 weeks of age.”

Conclusion

Foetal immune responses may be a surrogate variable for or directly influence lung function outcomes in early life.

Environmental Air Pollutants Inhaled during Pregnancy Are Associated with Altered Cord Blood Immune Cell Profiles

Air pollution exposure during pregnancy may be a risk factor for altered immune maturation in the offspring. We investigated the association between ambient air pollutants during pregnancy and cell populations in cord blood from babies born to mothers with asthma enrolled in the Breathing for Life Trial. For each patient (n = 91), daily mean ambient air pollutant levels were extracted during their entire pregnancy for sulfur dioxide (SO₂), nitric oxide, nitrogen dioxide, carbon monoxide, ozone, particulate matter <10 μm (PM₁₀) or <2.5 μm (PM_2.5), humidity, and temperature. Ninety-one cord blood samples were collected, stained, and assessed using fluorescence-activated cell sorting (FACS). Principal Component (PC) analyses of both air pollutants and cell types with linear regression were employed to define associations. Considering risk factors and correlations between PCs, only one PC from air pollutants and two from cell types were statistically significant. PCs from air pollutants were characterized by higher PM_2.5 and lower SO₂ levels. PCs from cell types were characterized by high numbers of CD8 T cells, low numbers of CD4 T cells, and by high numbers of plasmacytoid dendritic cells (pDC) and low numbers of myeloid DCs (mDCs). PM_2.5 levels during pregnancy were significantly associated with high numbers of pDCs (p = 0.006), and SO₂ with high numbers of CD8 T cells (p = 0.002) and low numbers of CD4 T cells (p = 0.011) and mDCs (p = 4.43 × 10⁻⁶) in cord blood. These data suggest that ambient SO₂ and PM_2.5 exposure are associated with shifts in cord blood cell types that are known to play significant roles in inflammatory respiratory disease in childhood.

Role of innate immunity and myeloid cells in susceptibility to allergic disease

Allergic diseases, including asthma, food allergy, eczema, and allergic rhinitis, are common diseases increasing in prevalence. Allergy, a failure of immune tolerance to innocuous environmental allergens, is characterized by allergen-specific immune responses, including IgE antibodies and T helper and T follicular helper cells producing type 2 cytokines. Despite the central role of adaptive immunity in pathophysiology of allergy, there is a growing body of evidence indicating an important role for the innate immune system in allergic disease. In this review, we focus on epithelial-mononuclear phagocyte communication in the control of allergy and tolerance. We discuss studies on early life environmental exposures and allergy susceptibility, and the evidence for innate training of mononuclear phagocytes as the mechanistic link between exposure and health or disease.

The intersect of genetics, environment, and microbiota in asthma-perspectives and challenges

In asthma, a significant portion of the interaction between genetics and environment occurs through microbiota. The proposed mechanisms behind this interaction are complex and at times contradictory. This review covers recent developments in our understanding of this interaction: the "microbial hypothesis" and the "farm effect"; the role of endotoxin and genetic variation in pattern recognition systems; the interaction with allergen exposure; the additional involvement of host gut and airway microbiota; the role of viral respiratory infections in interaction with the 17q21 and CDHR3 genetic loci; and the importance of in utero and early-life timing of exposures. We propose a unified framework for understanding how all these phenomena interact to drive asthma pathogenesis. Finally, we point out some future challenges for continued research in this field, in particular the need for multiomic integration, as well as the potential utility of asthma endotyping.

The Role of the Microbiome in Food Allergy: A Review

Food allergies are common and estimated to affect 8% of children and 11% of adults in the United States. They pose a significant burden—physical, economic and social—to those affected. There is currently no available cure for food allergies. Emerging evidence suggests that the microbiome contributes to the development and manifestations of atopic disease. According to the hygiene hypothesis, children growing up with older siblings have a lower incidence of allergic disease compared with children from smaller families, due to their early exposure to microbes in the home. Research has also demonstrated that certain environmental exposures, such as a farming environment, during early life are associated with a diverse bacterial experience and reduced risk of allergic sensitization. Dysregulation in the homeostatic interaction between the host and the microbiome or gut dysbiosis appears to precede the development of food allergy, and the timing of such dysbiosis is critical. The microbiome affects food tolerance via the secretion of microbial metabolites (e.g., short chain fatty acids) and the expression of microbial cellular components. Understanding the biology of the microbiome and how it interacts with the host to maintain gut homeostasis is helpful in developing smarter therapeutic approaches. There are ongoing trials evaluating the benefits of probiotics and prebiotics, for the prevention and treatment of atopic diseases to correct the dysbiosis. However, the routine use of probiotics as an intervention for preventing allergic disease is not currently recommended. A new approach in microbial intervention is to attempt a more general modification of the gut microbiome, such as with fecal microbiota transplantation. Developing targeted bacterial therapies for food allergy may be promising for both the treatment and prevention of food allergy. Similarly, fecal microbiota transplantation is being explored as a potentially beneficial interventional approach. Overall, targeted bacterial therapies for food allergy may be promising for both the treatment and prevention of food allergy.

Evolving concepts in how viruses impact asthma: A Work Group Report of the Microbes in Allergy Committee of the American Academy of Allergy, Asthma & Immunology

Over the past decade, there have been substantial advances in our understanding about how viral infections regulate asthma. Important lessons have been learned from birth cohort studies examining viral infections and subsequent asthma and from understanding the relationships between host genetics and viral infections, the contributions of respiratory viral infections to patterns of immune development, the impact of environmental exposure on the severity of viral infections, and how the viral genome influences host immune responses to viral infections. Further, there has been major progress in our knowledge about how bacteria regulate host immune responses in asthma pathogenesis. In this article, we also examine the dynamics of bacterial colonization of the respiratory tract during viral upper respiratory tract infection, in addition to the relationship of the gut and respiratory microbiomes with respiratory viral infections. Finally, we focus on potential interventions that could decrease virus-induced wheezing and asthma. There are emerging therapeutic options to decrease the severity of wheezing exacerbations caused by respiratory viral infections. Primary prevention is a major goal, and a strategy toward this end is considered.

Indoor ozone and particulate matter modify the association between airborne endotoxin and schoolchildren's lung function

BACKGROUND

To date, the effect of household airborne pollutants on the association between airborne endotoxin and lung function of schoolchildren is unknown.

OBJECTIVES

The objective of this study is to evaluate whether indoor air pollutants such as carbon monoxide (CO), carbon dioxide (CO₂), nitrogen dioxide (NO₂), sulfur dioxide (SO₂), ozone (O₃), particulate matter with aerodynamic diameter <10 and 2.5 μm (PM₁₀, PM_2.5) can modify the association between airborne endotoxin and school children's lung function in a heavy industrial city in Taiwan.

METHODS

We recruited 120 elementary school-age children in Kaohsiung City, Taiwan. Aerosol samples were collected on a filter membrane for 24 h period and then analyzed for endotoxin. Air pollutants were measured for 24 h in living rooms while school children's lung function was measured. The modification of air pollutants on the relationship between airborne endotoxin and children's lung function was estimated after adjusting the gender, age, height, weight, and case-control status.

RESULTS

We found that both O₃ and PM₁₀ concentrations significantly modified the relationships between airborne endotoxin and school children's lung function. Among children living in homes with O₃ ≥ 0.01 ppm or PM₁₀ ≥ 62 μg/m³, airborne endotoxin was negatively associated with lung functions, whereas among those living in homes with O₃ < 0.01 ppm or PM₁₀ < 62 μg/m³, airborne endotoxin was positively associated with lung functions.

CONCLUSIONS

The indoor air pollutant concentration of O₃ and PM₁₀ modifies the association between airborne endotoxin and school children's lung function.

Cytokine Responses to Rhinovirus and Development of Asthma, Allergic Sensitization, and Respiratory Infections during Childhood

RATIONALE

Immunophenotypes of antiviral responses, and their relationship with asthma, allergy, and lower respiratory tract infections, are poorly understood.

OBJECTIVES

We characterized multiple cytokine responses of peripheral blood mononuclear cells to rhinovirus stimulation, and their relationship with clinical outcomes.

METHODS

In a population-based birth cohort, we measured 28 cytokines after stimulation with rhinovirus-16 in 307 children aged 11 years. We used machine learning to identify patterns of cytokine responses, and related these patterns to clinical outcomes, using longitudinal models. We also ascertained phytohemagglutinin-induced T-helper cell type 2 (Th2)-cytokine responses (PHA-Th2).

MEASUREMENTS AND MAIN RESULTS

We identified six clusters of children based on their rhinovirus-16 responses, which were differentiated by the expression of four cytokine/chemokine groups: interferon-related (IFN), proinflammatory (Inflam), Th2-chemokine (Th2-chem), and regulatory (Reg). Clusters differed in their clinical characteristics. Children with an IFN^modInflam^highestTh2-chem^highestReg^highest rhinovirus-16-induced pattern had a PHA-Th2^low response, and a very low asthma risk (odds ratio [OR], 0.08; 95% confidence interval [CI], 0.01-0.81; P = 0.03). Two clusters had a high risk of asthma and allergic sensitization, but with different trajectories from infancy to adolescence. The IFN^lowestInflam^highTh2-chem^lowReg^mod cluster exhibited a PHA-Th2^lowest response and was associated with early-onset asthma and sensitization, and the highest risk of asthma exacerbations (OR, 1.37; 95% CI, 1.07-1.76; P = 0.014) and lower respiratory tract infection hospitalizations (OR, 2.40; 95% CI, 1.26-4.58; P = 0.008) throughout childhood. In contrast, the IFN^highestInflam^modTh2-chem^modReg^high cluster with a rhinovirus-16-cytokine pattern was characterized by a PHA-Th2^highest response, and a low prevalence of asthma/sensitization in infancy that increased sharply to become the highest among all clusters by adolescence (but with a low risk of asthma exacerbations).

CONCLUSIONS

Early-onset troublesome asthma with early-life sensitization, later-onset milder allergic asthma, and disease protection are each associated with different patterns of rhinovirus-induced immune responses.

Asthma in inner city children: recent insights: United States

PURPOSE OF REVIEW

Children living in US inner cities experience disparate burdens of asthma, especially in severity, impairment, exacerbations, and morbidity. Investigations seeking to better understand the factors and mechanisms underlying asthma prevalence, severity, and exacerbation in children living in these communities can lead to interventions that can narrow asthma disparities and potentially benefit all children with asthma. This update will focus on recent (i.e. late 2016-2017) advances in the understanding of asthma in US inner city children.

RECENT FINDINGS

Studies published in the past year expand understanding of asthma prevalence, severity, exacerbation, and the outcomes of guidelines-based management of these at-risk children, including: asthma phenotypes in US inner city children that are severe and difficult-to-control; key environmental determinants and mechanisms underlying asthma severity and exacerbations (e.g. allergy-mediated exacerbation susceptibility to rhinovirus); the importance of schools as a place for provocative exposures (e.g. mouse allergen, nitrogen dioxide) as well as a place where asthma care and outcomes can be improved; and the development and validation of clinically useful indices for gauging asthma severity and predicting exacerbations.

SUMMARY

These recent studies provide a trove of actionable findings that can improve asthma care and outcomes for these at-risk children.

Report from the National Institute of Allergy and Infectious Diseases workshop on "Atopic dermatitis and the atopic march: Mechanisms and interventions"

Atopic dermatitis (AD) affects up to 20% of children worldwide and is an increasing public health problem, particularly in developed countries. Although AD in infants and young children can resolve, there is a well-recognized increased risk of sequential progression from AD to other atopic diseases, including food allergy (FA), allergic rhinitis, allergic asthma, and allergic rhinoconjunctivitis, a process referred to as the atopic march. The mechanisms underlying the development of AD and subsequent progression to other atopic comorbidities, particularly FA, are incompletely understood and the subject of intense investigation. Other major research objectives are the development of effective strategies to prevent AD and FA, as well as therapeutic interventions to inhibit the atopic march. In 2017, the Division of Allergy, Immunology, and Transplantation of the National Institute of Allergy and Infectious Diseases sponsored a workshop to discuss current understanding and important advances in these research areas and to identify gaps in knowledge and future research directions. International and national experts in the field were joined by representatives from several National Institutes of Health institutes. Summaries of workshop presentations, key conclusions, and recommendations are presented herein.

Advances in asthma in 2017: Mechanisms, biologics, and genetics

This review summarizes some of the most significant advances in asthma research over the past year. We first focus on novel discoveries in the mechanism of asthma development and exacerbation. This is followed by a discussion of potential new biomarkers, including the use of radiographic markers of disease. Several new biologics have become available to the clinician in the past year, and we summarize these advances and how they can influence the clinical delivery of asthma care. After this, important findings in the genetics of asthma and heterogeneity in phenotypes of the disease are explored, as is the role the environment plays in shaping the development and exacerbation of asthma. Finally, we conclude with a discussion of advances in health literacy and how they will affect asthma care.

Development of allergic immunity in early life

The growth and maturity of the peripheral immune system and subsequent development of pulmonary immunity in early life is dictated by host, environmental and microbial factors. Dysregulation during the critical window of immune development in the postnatal years results in disease which impacts on lifelong lung health. Asthma is a common disease in childhood and is often preceded by wheezing illnesses during the preschool years. However, the mechanisms underlying development of wheeze and how and why only some children progress to asthma is unknown. Human studies to date have generally focused on peripheral immune development, with little assessment of local tissue pathology in young children. Moreover, mechanisms underlying the interactions between inflammation and tissue repair at mucosal surfaces in early life remain unknown. Disappointingly, mechanistic studies in mice have predominantly used adult models. This review will consider the aspects of the neonatal immune system which might contribute to the development of early life wheezing disorders and asthma, and discuss the external environmental factors which may influence this process.

Lessons learned from birth cohort studies conducted in diverse environments

Childhood asthma develops from a complex interaction among host and environmental factors in early life. Birth cohort studies have provided valuable insight into asthma risk factors and the natural history of wheezing and asthma through childhood and beyond. Early life aeroallergen sensitization and wheezing illnesses associated with virus and bacterial infections have been identified as pivotal risk factors for asthma inception. Recently, focus has turned toward protective factors that promote lung health in children. Studies in a variety of environments, including farms and urban communities, suggest that diverse exposures to microbes in early life lead to a lower risk of allergy and asthma in childhood. The mechanisms underlying how these exposures and the gut and airway microbiomes alter the host response to allergens and viruses are of interest and an area of ongoing study. Longitudinal follow up of birth cohorts in diverse environments worldwide will continue to provide critical knowledge about the factors that impact the natural history of asthma.