Atopic phenotypes identified with latent class analyses at age 2 years

Bridging Differences in Cohort Analyses of the Relationship between Secondhand Smoke Exposure during Pregnancy and Birth Weight: The Transportability Framework in the ECHO Program

BACKGROUND

Estimates for the effects of environmental exposures on health outcomes, including secondhand smoke (SHS) exposure, often present considerable variability across studies. Knowledge of the reasons behind these differences can aid our understanding of effects in specific populations as well as inform practices of combining data from multiple studies.

OBJECTIVES

This study aimed to assess the presence of effect modification by measured sociodemographic characteristics on the effect of SHS exposure during pregnancy on birth weights that may drive differences observed across cohorts. We also aimed to quantify the extent to which differences in the cohort mean effects observed across cohorts in the Environmental influences on Child Health Outcomes (ECHO) consortium are due to differing distributions of these characteristics.

METHODS

We assessed the presence of effect modification and transportability of effect estimates across five ECHO cohorts in a total of 6,771 mother-offspring dyads. We assessed the presence of effect modification via gradient boosting of regression trees based on the H-statistic. We estimated individual cohort effects using linear models and targeted maximum likelihood estimation (TMLE). We then estimated transported effects from one cohort to each of the remaining cohorts using a robust nonparametric estimation approach relying on TMLE estimators and compared them to the original effect estimates for these cohorts.

RESULTS

Observed effect estimates varied across the five cohorts, ranging from significantly lower birth weight associated with exposure [- 167.3 g ; 95% confidence interval (CI): - 270.4 , - 64.1 ] to higher birth weight with wide CIs, including the null (42.4 g ; 95% CI: - 15.0 , 99.8). Transported effect estimates only minimally explained differences in the point estimates for two out of the four cohort pairs.

DISCUSSION

Our findings of weak to moderate evidence of effect modification and transportability indicate that unmeasured individual-level and contextual factors and sources of bias may be responsible for differences in the effect estimates observed across ECHO cohorts. https://doi.org/10.1289/EHP13961.

Atopic Dermatitis Across Shades of Skin

Atopic dermatitis (AD) is a chronic, heterogeneous inflammatory skin disease that is associated with immense patient burden globally. There is increasing appreciation of disparities among patients identified as having skin of color (SOC), which often refers to patients of non-White race or non-European ancestry, but can broadly include individuals from a number of different racial, ethnic, ancestral, and skin pigmentation groups based on definition. In this narrative review, we discuss key terminology as it relates to AD across shades of skin, including modern definitions of 'race', 'ethnicity', and 'SOC'. We then synthesize the current literature describing disparities in AD prevalence, disease recognition, and burden alongside current data regarding genetic and immunologic findings across SOC populations. In the context of these findings, we highlight key concomitant social determinants of health, including environmental factors, socioeconomic status, and access to care, for which race often serves as a proxy for true biological and genetic differences. Finally, we discuss future efforts to shift to a more inclusive understanding of AD to encompass all shades of skin, to ensure equitable representation of diverse populations in high impact research, and intensify efforts to address the critical upstream factors driving observed disparities.

Biologics in the treatment of asthma in children and adolescents

Severe asthma in childhood confers substantial patient- and society-level burdens. Although biologics have been available for the management in adults and adolescents for nearly 20 years, research on the efficacy and safety of biologics in children and adolescents has lagged. Fortunately, more recent research specifically in children has provided an evidence base for biologic use in this age group. Most children with severe asthma demonstrate a type 2 inflammatory phenotype, the primary target of currently approved biologics. Three biologics, omalizumab, mepolizumab, and duplilumab, are Food and Drug Administration-approved for children as young as 6 years, whereas benralizumab and tezepelumab are approved for adolescents older than 12 years. All these agents reduce the rates of severe asthma exacerbations, whereas their effects on pulmonary function vary across agents. Safety profiles are reassuring, although additional long-term safety data in children are still needed. The choice of a biologic agent follows a careful assessment of other factors that contribute to uncontrolled asthma and includes biomarkers of blood eosinophils, fractional exhaled nitric oxide, allergic sensitization, and IgE levels. This review focuses on the underlying pathophysiology of childhood asthma, an approach to phenotyping patients, and the efficacy, safety, and use of biologics in children and adolescents with severe asthma.

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.

Adolescent and young adult allergic asthma treatment challenges

The transition from paediatric care to adult care is often difficult, especially in children with chronic diseases like asthma. A significant number of children reach remission throughout puberty; consequently, they are not tracked down for subsequent follow-ups and are not included in transition programmes to adult care. This case report focuses on a young adult with asthma that began in childhood and went into remission during adolescence, only to experience a recurrence when the patient was a young adult. Due to failing to complete the transition process into adult care services, she had poor adherence to therapy and asthma control.Adherence and asthma control significantly improved after a multidisciplinary approach in an adult care setting. In conclusion, appropriate transition and a multidisciplinary approach are critical for the effective management of asthma in young adults.

Socioeconomic Determinants of Food Allergy Burden-A clinical introduction

OBJECTIVE

This review characterizes what is currently known about how prevalence, severity, distribution, and management of food allergy (FA) differs across socioeconomic strata and provides guidance for practicing clinicians about how to improve equity in research participation, healthcare delivery, and patient outcomes through a deeper understanding of the socioeconomic determinants of FA.

DATA SOURCES

Epidemiological and biomedical literature published prior to April 2022.

RESULTS

Socioeconomic status (SES) is a complex concept that not only encompasses economic resources (e.g., income, wealth) but also a person's social, economic and political power and standing, each of which can impact health. However, in many studies of individuals and families with FA, assessment of SES has been limited and often a respondent's membership within a racial and ethnic group is utilized as a proxy for low SES. As a whole, findings from US-population-based studies indicate a consistent trend: those who self-identify as non-Hispanic Black, and to a lesser extent other subpopulations who identify as being of non-White race and ethnicity, experience a greater burden of food-allergic sensitization and disease including higher rates of emergency health care utilization and food-induced anaphylactic fatality as compared to those identifying as White.

CONCLUSION

Reports of FA management and outcomes highlight inequities among specific low SES populations in the US. Clinicians can and should act to reduce inequities by engaging more diverse populations in clinical research, equitably implementing FA risk screening and prevention, thoughtfully utilizing emerging technologies to ameliorate disparities based on SES in healthcare delivery and outcomes, and advocating for social change.

Allergic sensitization trajectories to age 8 years in the Singapore GUSTO cohort

Background

Allergic sensitization is linked to allergy development, with early sensitization often associated with worse outcomes. We aimed to identify if distinct allergic sensitization trajectories existed within a diverse and multi-ethnic Asian cohort.

Methods

We administered modified ISAAC questionnaires in the first 8 years and conducted skin prick testing at ages 18 months, 3, 5 and 8 years in the Growing Up in Singapore Towards healthy Outcomes (GUSTO) cohort. We used latent class analysis to derive allergic sensitization trajectories, and adjusted odds ratios (AOR) to evaluate predictive risk factors and associations with allergic comorbidities.

Results

Among 997 children, three trajectories were identified: early food and mite sensitization (16.2%), late mite sensitization (24.2%) and no/low sensitization (59.6%). Early food and mite sensitization was associated with early eczema by 6 months [AOR (95%CI) 4.67 (1.78-12.28)], increased risk of wheeze by 3-8 years (ARR 1.72-1.99) and eczema in the first 8 years of life (ARR 1.87-2.41). Late mite sensitization was associated with female sex [AOR 0.58 (0.35-0.96)], cesarean section [AOR 0.54 (0.30-0.98)], early eczema by 6 months [AOR 3.40 (1.38-8.42)], and increased risk of eczema by 18 months [ARR 1.47 (1.03-2.08)] and 8 years [ARR 1.35 (1.05-1.73)].

Conclusion

Early onset of eczema and early allergic sensitization were strongly associated. Early sensitization, especially to house dust mites, was associated with increased risks of developing wheeze and eczema, pointing to the importance of developing preventive perinatal interventions and effective therapeutics for sensitized toddlers.

Evaluating the Longitudinal Course of Atopic Dermatitis: Implications for Clinical Practice

Atopic dermatitis (AD) is characterized by a heterogenous longitudinal course with varying severity, flares, and persistence. However, AD course is not routinely assessed in clinical practice or controlled trials. Our objective was to review the longitudinal course of AD in children and adults and discuss implications for routine practice and clinical trials. We conducted a focused review of the published literature, including retrospective, prospective, and interventional studies, clinical trials, and consensus guidelines. Estimates of AD persistence varied widely across studies but suggested that AD can indeed persist through childhood and into adulthood. Predictors of persistence are broad and include both disease-intrinsic and disease-extrinsic (i.e., environmental) factors. In real-world practice, most individuals with AD experience fluctuations in the signs and symptoms over time and do not experience persistent clearance of skin lesions. Clinical trials use mainly static measurements that do not take into account fluctuations in course, which may confound treatment effects. The heterogenous temporal pattern of AD can be incorporated into routine practice to better set expectations and offer a realistic prognosis. AD course should be routinely incorporated into clinical decision making. Future studies are needed to develop a standardized approach to AD assessment and treatment that includes longitudinal course.

Time-Specific Factors Influencing the Development of Asthma in Children

Susceptibility to asthma is complex and heterogeneous, as it involves both genetic and environmental insults (pre- and post-birth) acting in a critical window of development in early life. According to the Developmental Origins of Health and Disease, several factors, both harmful and protective, such as nutrition, diseases, drugs, microbiome, and stressors, interact with genotypic variation to change the capacity of the organism to successfully adapt and grow in later life. In this review, we aim to provide the latest evidence about predictive risk and protective factors for developing asthma in different stages of life, from the fetal period to adolescence, in order to develop strategic preventive and therapeutic interventions to predict and improve health later in life. Our study shows that for some risk factors, such as exposure to cigarette smoke, environmental pollutants, and family history of asthma, the evidence in favor of a strong association of those factors with the development of asthma is solid and widely shared. Similarly, the clear benefits of some protective factors were shown, providing new insights into primary prevention. On the contrary, further longitudinal studies are required, as some points in the literature remain controversial and a source of debate.

Long-Term Respiratory Consequences of Early-Life Respiratory Viral Infections: A Pragmatic Approach to Fundamental Questions

Early-life viral infection can have profound effects on the developing lung and immune systems, both important in asthma development. For decades, research has aimed to establish whether there is a causal link between these viral infections as an exposure and asthma later in childhood. Establishing causality will remain important, but new insights regarding early-life viral infection as an exposure, the recognition of asthma as a heterogeneous outcome, and the shared genetic susceptibility to both suggest a refocus from answering the theoretical question of causality toward additional pragmatic approaches focusing on improving patient outcomes across the spectrum of respiratory disease. This Clinical Commentary reviews the evidence on the consequences of early-life viral infection and aims to look beyond the question of causality, suggesting a research agenda specifically aimed at what matters for human development, and for the quality of life of current and future patients with wheezing disorders.

Deprivation of Dietary Fiber Enhances Susceptibility of Piglets to Lung Immune Stress

Growing evidence suggests that dietary fiber enhances short-chain fatty acid (SCFA) producing gut microbes, improving lung immunity against invading pathogens via the gut–lung axis. This study investigated the effects of dietary fiber on lung immune stress after challenge with complete Freund's adjuvant (CFA) containing killed Mycobacterium tuberculosis. Thirty-six healthy hybrid Duroc, Landrace, and Yorkshire male piglets (9.7 ± 1.07 kg, 35 ± 3 days) were randomly fed a low fiber (LF) diet formulated with semipurified corn starch, soy protein concentrate, and fishmeal or a high fiber (HF) diet composed of 1,000 g LF diet plus 20 g inulin, and 100 g cellulose. Piglets were housed individually in the metabolism cages with eighteen replicates per group, with one pig per cage. All the piglets received similar levels of digestible energy and lysine and had similar weight gain. After dietary treatment for 28 days, nine piglets per group were intravenously administered CFA (0.4 mg/kg) or an equivalent amount of sterile saline in a 2 × 2 factorial arrangement. In piglets fed the LF diet, CFA caused lung damage and elevated serum C-reactive protein and relative mRNA expression of genes related to lung inflammation (NLRP3, Casp1, ASC, IL1β, IL18, Bax). Compared with the LF diet, the HF diet increased bacterial diversity and Deferribacteres (p = 0.01) in the phylum level and unidentified_Ruminococcaceae (p = 0.03) and Catenisphaera (p < 0.01) in the genus level. The HF diet improved increased short-chain fatty acids in feces, blood, cecal, and colonic digesta; reduced lung damage; and promoted lung recovery. Overall, dietary fiber deprivation enhanced the risk of piglets to lung immune stress, demonstrating the importance of dietary fiber in gut–lung health.

Human Microbiome in Children, at the Crossroad of Social Determinants of Health and Personalized Medicine

The evolving field of microbiome research offers an excellent opportunity for biomarker identification, understanding drug metabolization disparities, and improving personalized medicine. However, the complexities of host-microbe ecological interactions hinder clinical transferability. Among other factors, the microbiome is deeply influenced by age and social determinants of health, including environmental factors such as diet and lifestyle conditions. In this article, the bidirectionality of social and host-microorganism interactions in health will be discussed. While the field of microbiome-related personalized medicine evolves, it is clear that social determinants of health should be mitigated. Furthermore, microbiome research exemplifies the need for specific pediatric investigation plans to improve children's health.

Financial burden and impact of atopic dermatitis out-of-pocket healthcare expenses among black individuals in the United States

Black race is associated with increased atopic dermatitis (AD) severity and healthcare resource utilization. However, the burden of out-of-pocket (OOP) expenses among black individuals with AD is not well understood. We sought to characterize the categories and impact of OOP healthcare expenses associated with AD management among black individuals. A 25-question voluntary online survey was administered to National Eczema Association members (N = 113,502). Inclusion criteria (US residents age ≥ 18 years; self-report of AD or primary caregivers of individuals with AD) was met by 77.3% (1118/1447) of respondents. Black individuals with AD were younger, had lower household income, Medicaid, urban residence, poor AD control and frequent skin infections (P ≤ 0.02). Blacks vs. non-blacks reported more OOP costs for prescription medications covered (74.2% vs. 63.6%, P = 0.04) and not covered (65.1% vs. 46.5%, P = 0.0004) by insurance, emergency room visits (22.1% vs. 11.8%, P = 0.005), and outpatient laboratory testing (33.3% vs. 21.8%, P = 0.01). Black race was associated with increased household financial impact from OOP expenses (P = 0.0009), and predictors of financial impact included minimally controlled AD (adjusted OR [95% CI] 13.88 [1.63-117.96], P = 0.02), systemic therapy (4.34 [1.63-11.54], 0.003), > $200 monthly OOP expenses (14.28 [3.42-59.60], P = 0.0003), and Medicaid (4.02 [1.15-14.07], P = 0.03). Blacks with Medicaid had higher odds of harmful financial impact (3.32 [1.77-6.24], P = 0.0002) than those of black race (1.81 [1.04-3.15], P = 0.04) or with Medicaid (1.39 [1.02-1.88], P = 0.04) alone. Black race is associated with increased OOP costs for AD and significant household financial impact. Targeted interventions are needed to address financial disparities in AD.

Risk, Mechanisms and Implications of Asthma-Associated Infectious and Inflammatory Multimorbidities (AIMs) among Individuals With Asthma: a Systematic Review and a Case Study

Our prior work and the work of others have demonstrated that asthma increases the risk of a broad range of both respiratory (e.g., pneumonia and pertussis) and non-respiratory (e.g., zoster and appendicitis) infectious diseases as well as inflammatory diseases (e.g., celiac disease and myocardial infarction [MI]), suggesting the systemic disease nature of asthma and its impact beyond the airways. We call these conditions asthma-associated infectious and inflammatory multimorbidities (AIMs). At present, little is known about why some people with asthma are at high-risk of AIMs, and others are not, to the extent to which controlling asthma reduces the risk of AIMs and which specific therapies mitigate the risk of AIMs. These questions represent a significant knowledge gap in asthma research and unmet needs in asthma care, because there are no guidelines addressing the identification and management of AIMs. This is a systematic review on the association of asthma with the risk of AIMs and a case study to highlight that 1) AIMs are relatively under-recognized conditions, but pose major health threats to people with asthma; 2) AIMs provide insights into immunological and clinical features of asthma as a systemic inflammatory disease beyond a solely chronic airway disease; and 3) it is time to recognize AIMs as a distinctive asthma phenotype in order to advance asthma research and improve asthma care. An improved understanding of AIMs and their underlying mechanisms will bring valuable and new perspectives improving the practice, research, and public health related to asthma.

Air pollution-related asthma profiles among children/adolescents: A multi-group latent class analysis

BACKGROUND

This study aimed to investigate the asthma profile among children/adolescents and the relationship of the prevalence of air pollution profiles using latent class analysis (LCA).

OBJECTIVES

In this cross-sectional study, a case rural community was selected in an industrial area, and two rural control communities were selected in unexposed areas.

METHODS

Hourly concentrations of PM₁₀, SO₂, NO_2, and total volatile organic compounds were obtained from the records of a fixed air quality monitoring station, and the concentrations of benzene, toluene, xylenes styrene were measured during six campaigns. Asthma data was collected using the International Study of Asthma and Allergies in Childhood in 7-18 years old children/adolescents. The modeling was conducted using LCA.

RESULTS

A higher amount of air pollution indices were observed in the case than both control communities. LCA divided the participants into three clusters; "healthy" (92.8%), "moderate" (2.8%), and "severe" (4.4%). A higher probability of severe asthma (6.8%) was observed in the case than control communities (2.6% and 1.8%). Additionally, after adjusting for possible confounders, the odds of asthma was lower in the control communities than the case in both moderate and sever classes (Odds Ratios in the range of 0.135-0.697).

CONCLUSIONS

This study indicates asthma profiles of children/adolescents and the higher prevalence of severe class in the area, explaining the possible effect of air pollution.

Genetics of Asthma and Allergic Diseases

Asthma genes have been identified through a range of approaches, from candidate gene association studies and family-based genome-wide linkage analyses to genome-wide association studies (GWAS). The first GWAS of asthma, reported in 2007, identified multiple markers on chromosome 17q21 as associates of the childhood-onset asthma. This remains the best replicated asthma locus to date. However, notwithstanding undeniable successes, genetic studies have produced relatively heterogeneous results with limited replication, and despite considerable promise, genetics of asthma and allergy has, so far, had limited impact on patient care, our understanding of disease mechanisms, and development of novel therapeutic targets. The paucity of precise replication in genetic studies of asthma is partly explained by the existence of numerous gene-environment interactions. Another important issue which is often overlooked is that of time of the assessment of the primary outcome(s) and the relevant environmental exposures. Most large GWASs use the broadest possible definition of asthma to increase the sample size, but the unwanted consequence of this is increased phenotypic heterogeneity, which dilutes effect sizes. One way of addressing this is to precisely define disease subtypes (e.g. by applying novel mathematical approaches to rich phenotypic data) and use these latent subtypes in genetic studies.

Increased risk of asthma at age 10 years for children sensitized to multiple allergens

BACKGROUND

Childhood sensitization patterns have been previously found to be related to variable risk of early life allergic disease in several birth cohorts.

OBJECTIVE

To determine whether these risks persist into later childhood.

METHODS

In the birth cohort of the Wayne County Health, Environment, Allergy and Asthma Longitudinal Study, previous latent class analysis based on sensitization to 10 allergens found the following 4 early life sensitization patterns at age 2 years: "highly sensitized," "milk/egg dominated," "peanut and inhalant(s)," and "low to no sensitization." At an age 10 study-specific visit, children were evaluated by an allergist for current asthma and atopic dermatitis through a physical examination and interviews with the child and parent or guardian. Total and specific immunoglobulin E (IgE), spirometry, and methacholine challenge were also completed.

RESULTS

Compared with children sensitized to none or 1 allergen, children sensitized to 4 or more food and inhalant allergens at age 2 had the highest risk of current asthma (relative risk [RR], 4.42; 95% confidence interval [CI], 2.58-7.59; P < .001) and bronchial hyperresponsiveness (RR, 1.77; 95% CI, 1.29-2.42; P < .001). In addition, they had the highest levels of total IgE (geometric mean, 800 IU/mL; 95% CI, 416-1536) among the 4 groups. Risk of current atopic dermatitis did not depend on pattern of sensitization but remained increased for children with any sensitization (RR, 2.23; 95% CI, 1.40-3.55; P < .001). No differences in spirometry (forced expiratory volume in 1 second, forced expiratory flow between 25% and 75%, and forced expiratory volume in 1 second/forced vital capacity) were identified.

CONCLUSION

The previously reported importance of a specific pattern of sensitization in early life (sensitization to ≥4 inhalant and food allergens) continues to be associated with an increased risk of asthma, bronchial hyperresponsiveness, and high total IgE at age 10 years.

The Phenotype of the Food-Allergic Patient

Food allergy's increasing prevalence across the globe has initiated research into risk factors associated with the disease and coexistence with other allergic diseases. Longitudinal birth cohorts have identified food allergy phenotypes of patients based on genetic background, racial diversity, and environmental factors. Identifying food sensitization patterns and coexistence of other allergic diseases allows physicians to provide appropriate care for food allergy and personalized anticipatory guidance for the appearance of other allergic diseases. The authors seek to detail key findings of 4 longitudinal allergy birth cohorts that investigate food allergy and other allergic diseases to further characterize food allergy phenotypes.

Sensitization to peanut, egg or pets is associated with skin barrier dysfunction in children with atopic dermatitis

BACKGROUND

Children with atopic dermatitis (AD) are often sensitized to food and aeroallergens, but sensitization patterns have not been analysed with biologic measures of disease pathogenicity.

OBJECTIVE

We sought to define allergen sensitization grouping(s) using unbiased machine learning and determine their associations with skin filaggrin (FLG) and transepidermal water loss (TEWL) (assesses skin barrier integrity), S100A8 and S100A9 expression (assesses skin inflammation) and AD severity.

METHODS

We studied 400 children with AD in the Mechanisms of Progression from Atopic Dermatitis to Asthma in Children (MPAACH) cohort to identify groupings of food and aeroallergen sensitizations. MPAACH is a paediatric AD cohort, aged 1-2, recruited through hospital/community settings between 2016 and 2018. We analysed these groupings' associations with AD biomarkers: skin FLG, S100A8 and S100A9 expression, total IgE, TEWL and AD severity.

RESULTS

An unbiased machine learning approach revealed five allergen clusters. The most common cluster (N = 131), SPT_PEP, had sensitization to peanut, egg and/or pets. Three low prevalence clusters, which included children with allergen sensitization other than peanut, egg or pets, were combined into SPT_Other . SPT_NEG included children with no sensitization(s). SPT_PEP children had higher median non-lesional TEWL (16.9 g/m² /h) and IgE (90 kU/L) compared with SPT_OTHER (8.8 g/m² /h and 24 kU/L; p = .01 and p < .001) and SPT_NEG (9 g/m² /h and 26 kU/L; p = .003 and p < .001). SPT_PEP children had lower median lesional (0.70) and non-lesional (1.09) FLG expression compared with SPT_OTHER (lesional: 0.9; p = .047, non-lesional: 1.78; p = .01) and SPT_NEG (lesional: 1.47; p < .001, non-lesional: 2.21; p < .001). There were no differences among groupings in S100A8 or S100A9 expression.

CONCLUSIONS AND CLINICAL RELEVANCE

In this largely clinic-based cohort of young children with AD, allergic sensitization to peanut, egg, cat or dog was associated with more severe disease and skin barrier function but not markers of cutaneous inflammation. These data need replicating in a population-based cohort but may have important implications for understanding the interaction between AD and allergic sensitization.

Endotype of allergic asthma with airway obstruction in urban children

BACKGROUND

Black and Hispanic children growing up in disadvantaged urban neighborhoods have the highest rates of asthma and related morbidity in the United States.

OBJECTIVES

This study sought to identify specific respiratory phenotypes of health and disease in this population, associations with early life exposures, and molecular patterns of gene expression in nasal epithelial cells that underlie clinical disease.

METHODS

The study population consisted of 442 high-risk urban children who had repeated assessments of wheezing, allergen-specific IgE, and lung function through 10 years of age. Phenotypes were identified by developing temporal trajectories for these data, and then compared to early life exposures and patterns of nasal epithelial gene expression at 11 years of age.

RESULTS

Of the 6 identified respiratory phenotypes, a high wheeze, high atopy, low lung function group had the greatest respiratory morbidity. In early life, this group had low exposure to common allergens and high exposure to ergosterol in house dust. While all high-atopy groups were associated with increased expression of a type-2 inflammation gene module in nasal epithelial samples, an epithelium IL-13 response module tracked closely with impaired lung function, and a MUC5AC hypersecretion module was uniquely upregulated in the high wheeze, high atopy, low lung function group. In contrast, a medium wheeze, low atopy group showed altered expression of modules of epithelial integrity, epithelial injury, and antioxidant pathways.

CONCLUSIONS

In the first decade of life, high-risk urban children develop distinct phenotypes of respiratory health versus disease that link early life environmental exposures to childhood allergic sensitization and asthma. Moreover, unique patterns of airway gene expression demonstrate how specific molecular pathways underlie distinct respiratory phenotypes, including allergic and nonallergic asthma.

A systematic review of asthma case definitions in 67 birth cohort studies

BACKGROUND

Birth cohort studies are a valuable source of information about potential risk factors for childhood asthma. To better understand similarities and variations in findings between birth cohort studies, the methodologies used to measure asthma require consideration.

OBJECTIVE

To review and appraise the definitions of "asthma" used in birth cohort studies.

METHODS

A literature search, conducted in December 2017 in the MEDLINE database and birth cohort repositories, identified 1721 citations published since 1990. Information extracted included: study name, year of publication, sample size, sample age, prevalence of asthma (%), study region, source of information about asthma, measured outcome, and asthma case definition. A meta-analysis evaluated whether asthma prevalence in cohorts from Europe and North America varied by the studies' definition of asthma and by their data sources.

RESULTS

The final review included 67 birth cohorts, of which 48 (72%) were from Europe, 14 (21%) from North America, 3 (5%) from Oceania, 1 (1%) from Asia and 1 (1%) from South America. We identified three measured outcomes: "asthma ever", "current asthma", and "asthma" without further specification. Definitions of "asthma ever" were primarily based upon an affirmative parental response to the question whether the child had ever been diagnosed with asthma by a physician. The most frequently used definition of "current asthma" was "asthma ever" and either asthma symptoms or asthma medications in the last 12 months. This definition of "current asthma" was used in 16 cohorts. There was no statistically significant difference in the pooled asthma prevalence in European and North American cohorts that used questionnaire alone versus other data sources to classify asthma.

CONCLUSION

There is substantial heterogeneity in childhood asthma definitions in birth cohort studies. Standardisation of asthma case definitions will improve the comparability and utility of future cohort studies and enable meta-analyses.

Artificial Intelligence and Machine Learning in Chronic Airway Diseases: Focus on Asthma and Chronic Obstructive Pulmonary Disease

Chronic airway diseases are characterized by airway inflammation, obstruction, and remodeling and show high prevalence, especially in developing countries. Among them, asthma and chronic obstructive pulmonary disease (COPD) show the highest morbidity and socioeconomic burden worldwide. Although there are extensive guidelines for the prevention, early diagnosis, and rational treatment of these lifelong diseases, their value in precision medicine is very limited. Artificial intelligence (AI) and machine learning (ML) techniques have emerged as effective methods for mining and integrating large-scale, heterogeneous medical data for clinical practice, and several AI and ML methods have recently been applied to asthma and COPD. However, very few methods have significantly contributed to clinical practice. Here, we review four aspects of AI and ML implementation in asthma and COPD to summarize existing knowledge and indicate future steps required for the safe and effective application of AI and ML tools by clinicians.

Preventing asthma in high risk kids (PARK) with omalizumab: Design, rationale, methods, lessons learned and adaptation

Asthma remains one of the most important challenges to pediatric public health in the US. A large majority of children with persistent and chronic asthma demonstrate aeroallergen sensitization, which remains a pivotal risk factor associated with the development of persistent, progressive asthma throughout life. In individuals with a tendency toward Type 2 inflammation, sensitization and exposure to high concentrations of offending allergens is associated with increased risk for development of, and impairment from, asthma. The cascade of biological responses to allergens is primarily mediated through IgE antibodies and their production is further stimulated by IgE responses to antigen exposure. In addition, circulating IgE impairs innate anti-viral immune responses. The latter effect could magnify the effects of another early life exposure associated with increased risk of the development of asthma - viral infections. Omalizumab binds to circulating IgE and thus ablates antigen signaling through IgE-related mechanisms. Further, it has been shown restore IFN-α response to rhinovirus and to reduce asthma exacerbations during the viral season. We therefore hypothesized that early blockade of IgE and IgE mediated responses with omalizumab would prevent the development and reduce the severity of asthma in those at high risk for developing asthma. Herein, we describe a double-blind, placebo-controlled trial of omalizumab in 2-3 year old children at high risk for development of asthma to prevent the development and reduce the severity of asthma. We describe the rationale, methods, and lessons learned in implementing this potentially transformative trial aimed at prevention of asthma.

Infant Feeding Practices and Subsequent Dietary Patterns of School-Aged Children in a US Birth Cohort

BACKGROUND

Infant feeding practices are thought to shape food acceptance and preferences. However, few studies have evaluated whether these affect child diet later in life.

OBJECTIVE

The study objective was to examine the association between infant feeding practices and dietary patterns (DPs) in school-aged children.

DESIGN

A secondary analysis of data from a diverse prospective birth cohort with 10 years of follow-up (WHEALS [Wayne County Health Environment Allergy and Asthma Longitudinal Study]) was conducted.

PARTICIPANTS/SETTING

Children from the WHEALS (Detroit, MI, born 2003 through 2007) who completed a food screener at age 10 years were included (471 of 1,258 original participants).

MAIN OUTCOME MEASURES

The main outcome was DPs at age 10 years, identified using the Block Kids Food Screener.

STATISTICAL ANALYSIS PERFORMED

Latent class analysis was applied for DP identification. Breastfeeding and age at solid food introduction were associated with DPs using a 3-step approach for latent class modeling based on multinomial logistic regression models.

RESULTS

The following childhood DPs were identified: processed/energy-dense food (35%), variety plus high intake (41%), and healthy (24%). After weighting for loss to follow-up and covariate adjustment, compared with formula-fed children at 1 month, breastfed children had 0.41 times lower odds of the processed/energy-dense food DP vs the healthy DP (95% CI 0.14 to 1.25) and 0.53 times lower odds of the variety plus high intake DP (95% CI 0.17 to 1.61), neither of which were statistically significant. Results were similar, but more imprecise, for breastfeeding at 6 months. In addition, the association between age at solid food introduction and DP was nonsignificant, with each 1-month increase in age at solid food introduction associated with 0.81 times lower odds of the processed/energy-dense food DP relative to the healthy DP (95% CI 0.64 to 1.02).

CONCLUSIONS

A significant association between early life feeding practices and dietary patterns at school age was not detected. Large studies with follow-up beyond early childhood that can also adjust for the multitude of potential confounders associated with breastfeeding are needed.

Association between cesarean delivery types and obesity in preadolescence

Background/Objectives:

The association between mode of delivery and childhood obesity remains inconclusive. Because few studies have separated C-section types (planned or unplanned C-section), our objective was to assess how these subtypes relate to pre-adolescent obesity.

Subjects/Methods:

The study consisted of 570 maternal-child pairs drawn from the WHEALS birth cohort based in Detroit, Michigan. Children were followed-up at 10 years of age where a variety of anthropometric measurements were collected. Obesity was defined based on BMI percentile (≥95th percentile), as well as through gaussian finite mixture modeling on the anthropometric measurements. Risk ratios (RRs) and 95% confidence intervals (CIs) for obesity comparing planned and unplanned C-sections to vaginal deliveries were computed, which utilized inverse probability weights to account for loss to follow-up and multiple imputation for covariate missingness. Mediation models were fit to examine the mediation role of breastfeeding.

Results:

After adjusting for marital status, maternal race, prenatal tobacco smoke exposure, maternal age, maternal BMI, any hypertensive disorders during pregnancy, gestational diabetes, prenatal antibiotic use, child sex, parity, and birthweight z-score, children born via planned C-section had 1.77 times higher risk of obesity (≥95th percentile), relative to those delivered vaginally ((95% CI)=(1.16,2.72); p=0.009). No association was found comparing unplanned C-section to vaginal delivery (RR (95% CI)=0.75 (0.45, 1.23); p=0.25). Results were similar but slightly stronger when obesity was defined by anthropometric class (RR (95% CI)=2.78 (1.47, 5.26); p=0.002). Breastfeeding did not mediate the association between mode of delivery and obesity.

Conclusions:

These findings indicate that children delivered via planned C-section—but not unplanned C-section—have a higher risk of pre-adolescent obesity, suggesting that partial labor or membrane rupture (typically experienced during unplanned C-section delivery) may offer protection. Additional research is needed to understand the biological mechanisms behind this effect, including whether microbiological differences fully or partially account for the association.

Health Impact and Therapeutic Manipulation of the Gut Microbiome

Recent advances in microbiome studies have revealed much information about how the gut virome, mycobiome, and gut bacteria influence health and disease. Over the years, many studies have reported associations between the gut microflora under different pathological conditions. However, information about the role of gut metabolites and the mechanisms by which the gut microbiota affect health and disease does not provide enough evidence. Recent advances in next-generation sequencing and metabolomics coupled with large, randomized clinical trials are helping scientists to understand whether gut dysbiosis precedes pathology or gut dysbiosis is secondary to pathology. In this review, we discuss our current knowledge on the impact of gut bacteria, virome, and mycobiome interactions with the host and how they could be manipulated to promote health.

Resolving Clinical Phenotypes into Endotypes in Allergy: Molecular and Omics Approaches

Allergic diseases are highly complex with respect to pathogenesis, inflammation, and response to treatment. Current efforts for allergic disease diagnosis have focused on clinical evidence as a binary outcome. Although outcome status based on clinical phenotypes (observable characteristics) is convenient and inexpensive to measure in large studies, it does not adequately provide insight into the complex molecular determinants of allergic disease. Individuals with similar clinical diagnoses do not necessarily have similar disease etiologies, natural histories, or responses to treatment. This heterogeneity contributes to the ineffective response to treatment leading to an annual estimated cost of $350 billion in the USA alone. There has been a recent focus to deconvolute the clinical heterogeneity of allergic diseases into specific endotypes using molecular and omics approaches. Endotypes are a means to classify patients based on the underlying pathophysiological mechanisms involving distinct functions or treatment response. The advent of high-throughput molecular omics, immunophenotyping, and bioinformatics methods including machine learning algorithms is facilitating the development of endotype-based diagnosis. As we move to the next decade, we should truly start treating clinical endotypes not clinical phenotype. This review highlights current efforts taking place to improve allergic disease endotyping via molecular omics profiling, immunophenotyping, and machine learning approaches in the context of precision diagnostics in allergic diseases. Graphical Abstract.

Phenotypes of wheezing and asthma in preschool children

PURPOSE OF REVIEW

The purpose of this review is to provide an overview of the identified phenotypes of preschool wheezing.

RECENT FINDINGS

Early life wheezing patterns have been described in multiple populations, with several commonalities found between cohorts. Early life environmental exposures have been found to be differentially associated with preschool wheezing phenotypes and their future trajectories. These include allergen and microbe exposure, environmental tobacco smoke exposure, and maternal stress and depression. Elevated IgE in early life may also influence future asthma risk.

SUMMARY

Preschool wheezing phenotypes are heterogeneous and complex, with trajectories that are related to factors including environmental exposures. More research is needed to characterize these relationships, hopefully leading to targeted prevention strategies.

The Evolving Microbiome from Pregnancy to Early Infancy: A Comprehensive Review

Pregnancy induces a number of immunological, hormonal, and metabolic changes that are necessary for the mother to adapt her body to this new physiological situation. The microbiome of the mother, the placenta and the fetus influence the fetus growth and undoubtedly plays a major role in the adequate development of the newborn infant. Hence, the microbiome modulates the inflammatory mechanisms related to physiological and pathological processes that are involved in the perinatal progress through different mechanisms. The present review summarizes the actual knowledge related to physiological changes in the microbiota occurring in the mother, the fetus, and the child, both during neonatal period and beyond. In addition, we approach some specific pathological situations during the perinatal periods, as well as the influence of the type of delivery and feeding.

Management/Comorbidities of School-Aged Children with Asthma

Asthma is a complex heterogeneous disease characterized by reversible airflow obstruction. After appropriate diagnosis, the management in school-aged children centers on 3 broad domains: pharmacologic treatment, treatment of underlying comorbidities, and education of the patient and caregivers. It is important to understand that the phenotypic differences that exist in the school-aged child with asthma may impact underlying comorbid conditions as well as pharmacologic treatment choices. Following initiation of therapy, asthma control must be continually evaluated in order to optimize management.

Asthma and allergic rhinitis risk depends on house dust mite specific IgE levels in PARIS birth cohort children

Background

The natural history of allergic sensitization in childhood, and its impact on allergic disease development, needs to be clarified. This study aims to identify allergic sensitization and morbidity patterns during the first 8 years of life.

Methods

The study was conducted in the on-going population-based prospective Pollution and Asthma Risk: an Infant Study (PARIS) birth cohort. Sensitization profiles were identified by k-means clustering based upon allergen-specific IgE levels measured at 18 months and 8/9 years. Allergic morbidity profiles were identified by latent class analysis based on symptoms, symptom severity, treatments, and lifetime doctor-diagnoses of asthma, allergic rhinitis, and atopic dermatitis and on lower respiratory infections before 2 years.

Results

Five sensitization and 5 allergic morbidity patterns were established in 714 children. Children not sensitized or with isolated and low allergen-specific sensitization were grouped together (76.8%). A profile of early and transient sensitization to foods that increased the risk of asthma later in childhood was identified (4.9%). Children strongly sensitized (≥3.5 kU_A/L) to house dust mite at 8/9 years (9.0%) had the highest risk of asthma and allergic rhinitis. Finally, timothy grass pollen at 8/9 years sensitization profile (5.3%) was related to respiratory allergic diseases, as was early onset and persistent sensitization profile (4.1%), this latter being also strongly associated with atopic dermatitis.

Conclusions & Clinical Relevance

We show that accurate assessment of the risk of allergic disease should rely on earliness and multiplicity of sensitization, involved allergens, and allergen-specific IgE levels, and not considering solely allergic sensitization as a dichotomous variable (allergen-specific IgE ≥0.35 kU_A/L), as usually done. This is particularly striking for house dust mite. We are hopeful that, pending further confirmation in other populations, our findings will improve clinical practice as part of an approach to allergic disease prevention.

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

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

The Children's Respiratory and Environmental Workgroup (CREW) birth cohort consortium: design, methods, and study population

BACKGROUND

Single birth cohort studies have been the basis for many discoveries about early life risk factors for childhood asthma but are limited in scope by sample size and characteristics of the local environment and population. The Children's Respiratory and Environmental Workgroup (CREW) was established to integrate multiple established asthma birth cohorts and to investigate asthma phenotypes and associated causal pathways (endotypes), focusing on how they are influenced by interactions between genetics, lifestyle, and environmental exposures during the prenatal period and early childhood.

METHODS AND RESULTS

CREW is funded by the NIH Environmental influences on Child Health Outcomes (ECHO) program, and consists of 12 individual cohorts and three additional scientific centers. The CREW study population is diverse in terms of race, ethnicity, geographical distribution, and year of recruitment. We hypothesize that there are phenotypes in childhood asthma that differ based on clinical characteristics and underlying molecular mechanisms. Furthermore, we propose that asthma endotypes and their defining biomarkers can be identified based on personal and early life environmental risk factors. CREW has three phases: 1) to pool and harmonize existing data from each cohort, 2) to collect new data using standardized procedures, and 3) to enroll new families during the prenatal period to supplement and enrich extant data and enable unified systems approaches for identifying asthma phenotypes and endotypes.

CONCLUSIONS

The overall goal of CREW program is to develop a better understanding of how early life environmental exposures and host factors interact to promote the development of specific asthma endotypes.

Phenotypes of allergic diseases in children and their application in clinical situations

Allergic diseases, including allergic rhinitis, asthma, and atopic dermatitis, are common heterogeneous diseases that encompass diverse phenotypes and different pathogeneses. Phenotype studies of allergic diseases can facilitate the identification of risk factors and their underlying pathophysiology, resulting in the application of more effective treatment, selection of better treatment responses, and prediction of prognosis for each phenotype. In the early phase of phenotype studies in allergic diseases, artificial classifications were usually performed based on clinical features, such as triggering factors or the presence of atopy, which can result in the biased classification of phenotypes and limit the characterization of heterogeneous allergic diseases. Subsequent phenotype studies have suggested more diverse phenotypes for each allergic disease using relatively unbiased statistical methods, such as cluster analysis or latent class analysis. The classifications of phenotypes in allergic diseases may overlap or be unstable over time due to their complex interactions with genetic and encountered environmental factors during the illness, which may affect the disease course and pathophysiology. In this review, diverse phenotype classifications of allergic diseases, including atopic dermatitis, asthma, and wheezing in children, allergic rhinitis, and atopy, are described. The review also discusses the applications of the results obtained from phenotype studies performed in other countries to Korean children. Consideration of changes in the characteristics of each phenotype over time in an individual’s lifespan is needed in future studies.

Development of allergic sensitization and its relevance to paediatric asthma

PURPOSE OF REVIEW

The purpose of this review is to summarize the recent evidence on the distinct atopic phenotypes and their relationship with childhood asthma. We start by considering definitions and phenotypic classification of atopy and then review evidence on its association with asthma in children.

RECENT FINDINGS

It is now well recognized that both asthma and atopy are complex entities encompassing various different sub-groups that also differ in the way they interconnect. The lack of gold standards for diagnostic markers of atopy and asthma further adds to the existing complexity over diagnostic accuracy and definitions. Although recent statistical phenotyping studies contributed significantly to our understanding of these heterogeneous disorders, translating these findings into meaningful information and effective therapies requires further work on understanding underpinning biological mechanisms.

SUMMARY

The disaggregation of allergic sensitization may help predict how the allergic disease is likely to progress. One of the important questions is how best to incorporate tests for the assessment of allergic sensitization into diagnostic algorithms for asthma, both in terms of confirming asthma diagnosis, and the assessment of future risk.

Development of atopic sensitization in Finnish and Estonian children: A latent class analysis in a multicenter cohort

BACKGROUND

The prevalence of atopy is associated with a Western lifestyle, as shown by studies comparing neighboring regions with different socioeconomic backgrounds. Atopy might reflect various conditions differing in their susceptibility to environmental factors.

OBJECTIVE

We sought to define phenotypes of atopic sensitization in early childhood and examine their association with allergic diseases and hereditary background in Finland and Estonia.

METHODS

The analysis included 1603 Finnish and 1657 Estonian children from the DIABIMMUNE multicenter young children cohort. Specific IgE levels were measured at age 3, 4, and 5 years, respectively, and categorized into 3 CAP classes. Latent class analysis was performed with the statistical software package poLCA in R software.

RESULTS

Both populations differed in terms of socioeconomic status and environmental determinants, such as pet ownership, farm-related exposure, time spent playing outdoors, and prevalence of allergic diseases (all P < .001). Nevertheless, we found similar latent classes in both populations: an unsensitized class, a food class, 2 inhalant classes differentiating between seasonal and perennial aeroallergens, and a severe atopy class. The latter was characterized by high total and specific IgE levels and strongly associated with wheeze (odds ratio [OR], 5.64 [95% CI, 3.07-10.52] and 4.56 [95% CI, 2.35-8.52]), allergic rhinitis (OR, 22.4 [95% CI, 11.67-44.54] and 13.97 [95% CI, 7.33-26.4]), and atopic eczema (OR, 9.39 [95% CI, 4.9-19.3] and 9.5 [95% CI, 5.2-17.5] for Finland and Estonia, respectively). Environmental differences were reflected in the larger seasonal inhalant atopy class in Finland, although composition of classes was comparable between countries.

CONCLUSION

Despite profound differences in environmental exposures, there might exist genuine patterns of atopic sensitization. The distribution of these patterns might determine the contribution of atopic sensitization to disease onset.

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.

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

RATIONALE

Characterization of patterns of wheezing and allergic sensitization in early life may allow for identification of specific environmental exposures impacting asthma development.

OBJECTIVES

To define respiratory phenotypes in inner-city children and their associations with early-life environmental exposures.

METHODS

Data were collected prospectively from 442 children in the URECA (Urban Environment and Childhood Asthma) birth cohort through age 7 years, reflecting symptoms (wheezing), aeroallergen sensitization, pulmonary function, and body mass index. Latent class mixed models identified trajectories of wheezing, allergic sensitization, and pulmonary function. Cluster analysis defined nonoverlapping groups (termed phenotypes). Potential associations between phenotypes and early-life environmental exposures were examined.

MEASUREMENTS AND MAIN RESULTS

Five phenotypes were identified and mainly differentiated by patterns of wheezing and allergic sensitization (low wheeze/low atopy; low wheeze/high atopy; transient wheeze/low atopy; high wheeze/low atopy; high wheeze/high atopy). Asthma was most often present in the high-wheeze phenotypes, with greatest respiratory morbidity among children with frequent wheezing and allergic sensitization. These phenotypes differentially related to early-life exposures, including maternal stress and depression, antenatal environmental tobacco smoke, house dust microbiome, and allergen content (all P < 0.05). Prenatal smoke exposure, maternal stress, and depression were highest in the high-wheeze/low-atopy phenotype. The high-wheeze/high-atopy phenotype was associated with low household microbial richness and diversity. Early-life aeroallergen exposure was low in high-wheeze phenotypes.

CONCLUSIONS

Patterns of wheezing, allergic sensitization, and lung function identified five respiratory phenotypes among inner-city children. Early-life environmental exposure to stress, depression, tobacco smoke, and indoor allergens and microbes differentially associate with specific phenotypes.

Allergen-induced activation of natural killer cells represents an early-life immune response in the development of allergic asthma

BACKGROUND

Childhood asthma in inner-city populations is a major public health burden, and understanding early-life immune mechanisms that promote asthma onset is key to disease prevention. Children with asthma demonstrate a high prevalence of aeroallergen sensitization and TH2-type inflammation; however, the early-life immune events that lead to TH2 skewing and disease development are unknown.

OBJECTIVE

We sought to use RNA sequencing of PBMCs collected at age 2 years to determine networks of immune responses that occur in children with allergy and asthma.

METHODS

In an inner-city birth cohort with high asthma risk, we compared gene expression using RNA sequencing in PBMCs collected at age 2 years between children with 2 or more aeroallergen sensitizations, including dust mite, cockroach, or both, by age 3 years and asthma by age 7 years (cases) and matched control subjects who did not have any aeroallergen sensitization or asthma by age 7 years.

RESULTS

PBMCs from the cases showed higher levels of expression of natural killer (NK) cell-related genes. After cockroach or dust mite allergen but not tetanus antigen stimulation, PBMCs from the cases compared with the control subjects showed differential expression of 244 genes. This gene set included upregulation of a densely interconnected NK cell-like gene network reflecting a pattern of cell activation and induction of inflammatory signaling molecules, including the key TH2-type cytokines IL9, IL13, and CCL17, as well as a dendritic cell-like gene network, including upregulation of CD1 lipid antigen presentation molecules. The NK cell-like response was reproducible in an independent group of children with later-onset allergic sensitization and asthma and was found to be specific to only those children with both aeroallergen sensitization and asthma.

CONCLUSION

These findings provide important mechanistic insight into an early-life immune pathway involved in TH2 polarization, leading to the development of allergic asthma.

Phenotypes of Recurrent Wheezing in Preschool Children: Identification by Latent Class Analysis and Utility in Prediction of Future Exacerbation

BACKGROUND

Recurrent preschool wheezing is a heterogeneous disorder with significant morbidity, yet little is known about phenotypic determinants and their impact on clinical outcomes.

OBJECTIVE

Latent class analysis (LCA) was used to identify latent classes of recurrent preschool wheeze and their association with future exacerbations and inhaled corticosteroid (ICS) treatment response.

METHODS

Data from 5 clinical trials of 1708 children aged 12 to 71 months with recurrent wheezing were merged. LCA was performed on 10 demographic, exposure, and sensitization variables to determine the optimal number of latent classes. The primary outcome was the annualized rate of wheezing exacerbations requiring systemic corticosteroids during the study intervention period; the secondary outcome was the time to first exacerbation. Exploratory analyses examined the effect of daily ICS treatment on exacerbation outcomes.

RESULTS

Four latent classes of recurrent wheezing were identified; these were not distinguished by current symptoms or historical exacerbations but differed with regard to allergen sensitization and/or exposures. Annualized exacerbation rates (mean ± SEM/year) were 0.65 ± 0.06 for class 1 ("minimal sensitization"), 0.93 ± 0.10 for class 2 ("sensitization with indoor pet exposure"), 0.60 ± 0.07 for class 3 ("sensitization with tobacco smoke exposure"), and 0.81 ± 0.10 for class 4 ("multiple sensitization and eczema") (P < .001). In a research setting of high adherence, daily ICS treatment improved exacerbation rates in classes 2 and 4 but not the other groups.

CONCLUSIONS

Sensitization and exposure assessments are useful in the prediction of future exacerbation and may identify children most likely to respond favorably to daily ICS treatment.

Food allergy phenotypes: The key to personalized therapy

Food allergies (FAs) are of increasing public health concern and are characterized by a large spectrum of diseases. Their diversity is well known for immunologic pathways (IgE, non-IgE-mediated FAs) and natural history. Many other factors and patient characteristics are involved including type of food, exposure route, allergic comorbidities, gender, racial and ethnic backgrounds, cofactors and health conditions. Food allergen components and sensitization profiles are also involved in FA phenotypes. A new approach to chronic disorders based on the identification of phenotypes through extensive knowledge of all the complex components is also applicable to FAs and could lead towards integrative care management. Diagnostic biomarkers for FAs are emerging which also contribute to better care modalities. The aim of this article was to highlight current knowledge regarding the phenotypic diversity of FA. This review will focus on IgE-mediated FAs and how identifying phenotypes may help to better understand the pathophysiological complexity, improve diagnosis and lead to personalized treatment strategies.

Delayed gut microbiota development in high-risk for asthma infants is temporarily modifiable by Lactobacillus supplementation

Gut microbiota dysbiosis and metabolic dysfunction in infancy precedes childhood atopy and asthma development. Here we examined gut microbiota maturation over the first year of life in infants at high risk for asthma (HR), and whether it is modifiable by early-life Lactobacillus supplementation. We performed a longitudinal comparison of stool samples collected from HR infants randomized to daily oral Lactobacillus rhamnosus GG (HRLGG) or placebo (HRP) for 6 months, and healthy (HC) infants. Meconium microbiota of HRP participants is distinct, follows a delayed developmental trajectory, and is primarily glycolytic and depleted of a range of anti-inflammatory lipids at 6 months of age. These deficits are partly rescued in HRLGG infants, but this effect was lost at 12 months of age, 6 months after cessation of supplementation. Thus we show that early-life gut microbial development is distinct, but plastic, in HR infants. Our findings offer a novel strategy for early-life preventative interventions.

Gut microbial dysbiosis in infancy is associated with childhood atopy and the development of asthma. Here, the authors show that gut microbiota perturbation is evident in the very earliest stages of postnatal life, continues throughout infancy, and can be partially rescued by Lactobacillus supplementation in high-risk for asthma infants.

Classification of Pediatric Asthma: From Phenotype Discovery to Clinical Practice

Advances in big data analytics have created an opportunity for a step change in unraveling mechanisms underlying the development of complex diseases such as asthma, providing valuable insights that drive better diagnostic decision-making in clinical practice, and opening up paths to individualized treatment plans. However, translating findings from data-driven analyses into meaningful insights and actionable solutions requires approaches and tools which move beyond mining and patterning longitudinal data. The purpose of this review is to summarize recent advances in phenotyping of asthma, to discuss key hurdles currently hampering the translation of phenotypic variation into mechanistic insights and clinical setting, and to suggest potential solutions that may address these limitations and accelerate moving discoveries into practice. In order to advance the field of phenotypic discovery, greater focus should be placed on investigating the extent of within-phenotype variation. We advocate a more cautious modeling approach by "supervising" the findings to delineate more precisely the characteristics of the individual trajectories assigned to each phenotype. Furthermore, it is important to employ different methods within a study to compare the stability of derived phenotypes, and to assess the immutability of individual assignments to phenotypes. If we are to make a step change toward precision (stratified or personalized) medicine and capitalize on the available big data assets, we have to develop genuine cross-disciplinary collaborations, wherein data scientists who turn data into information using algorithms and machine learning, team up with medical professionals who provide deep insights on specific subjects from a clinical perspective.