Distinct immune phenotypes in infants developing asthma during childhood

Association between parental occupational exposure and the risk of asthma in offspring: A meta-analysis and systematic review

BACKGROUND

Previous epidemiological studies have shown inconsistent results regarding the relation between the risk of asthma in offspring and parental occupational exposure. Therefore, we conducted a comprehensive and systematic collection of currently available epidemiological data to quantify the correlation between the 2.

METHODS

Related studies published before March 2023 were identified through searches of the Cochrane Library, Embase, PubMed, and Web of Science databases. The quality of included studies was assessed using the Newcastle-Ottawa Scale, while pooled odds ratios (ORs) with 95% confidence intervals (CIs) were computed using fixed-effect or random-effects models.

RESULTS

This systematic review included 10 cohort studies, with a total of 89,571 parent-child pairs included in the quantitative analysis. The results exhibited a substantial association between parental occupational exposure to allergens (OR = 1.11; 95% CI: 1.00, 1.23; P = .051) and irritants (OR = 1.19; 95% CI: 1.07, 1.32; P = .001) and an increased risk of asthma in offspring. This association was also observed in the analysis of wheezing (OR = 1.22; 95% CI: 1.11, 1.35; P < .001 and OR = 1.19; 95% CI: 1.08, 1.32; P = .001). Subgroup analysis demonstrated that maternal occupational exposure to allergens (OR = 1.07; 95% CI: 1.02, 1.12; P = .008) and irritants (OR = 1.13; 95% CI: 1.05, 1.21; P = .001) significantly increased the risk of childhood asthma. Furthermore, parental postnatal occupational exposure to allergens (OR = 1.26; 95% CI: 1.10, 1.46; P = .001) and irritants (OR = 1.26; 95% CI: 1.06, 1.49; P = .009) had a more pronounced impact on childhood asthma. Higher levels of exposure (OR = 1.26; 95% CI: 1.10, 1.46; P = .001 and OR = 1.30; 95% CI: 1.16, 1.47; P < .001) were recognized as significant risk factors for childhood asthma.

CONCLUSION

Parental occupational exposure to allergens and irritants increases the risk of asthma and wheezing in offspring, with maternal exposure, postnatal exposure, and high-dose exposure being the primary risk factors for childhood asthma.

Application of Asthma Prediction Tools in a Cohort of Infants with Severe Bronchiolitis

Background: Severe bronchiolitis is a strong childhood asthma risk factor. Early and accurate asthma prediction is key. We applied the Asthma Predictive Index (API), the modified Asthma Predictive Index (mAPI), and the Pediatric Asthma Risk Score (PARS) in a cohort of high-risk infants to predict asthma at age 6 years. Methods: We conducted a 17-center cohort of infants (age <1 year) hospitalized with severe bronchiolitis during 2011-2014. We used only infancy data to predict asthma at age 6 years. Results: The prevalence of parent-reported asthma at age 6 years was 328/880 (37%). The prevalences of a positive index/score for stringent and loose API, mAPI, and PARS were 21%, 51%, 11%, and 34%, respectively. Area under the receiver operating characteristic curves [95% confidence interval (CI)] ranged from 0.57 (95% CI 0.55-0.60) for mAPI to 0.66 (95% CI 0.63-0.70) for PARS. Conclusions: An asthma prediction tool for high-risk infants is needed to identify those who would benefit most from asthma prevention interventions.

Exposures to perfluoroalkyl substances and asthma phenotypes in childhood: an investigation of the COPSAC2010 cohort

BACKGROUND

Exposure to perfluoroalkyl substances may affect offspring immune development and thereby increase risk of childhood asthma, but the underlying mechanisms and asthma phenotype affected by such exposure is unknown.

METHODS

In the Danish COPSAC2010 cohort of 738 unselected pregnant women and their children plasma PFOS and PFOA concentrations were semi-quantified by untargeted metabolomics analyses and calibrated using a targeted pipeline in mothers (gestation week 24 and 1 week postpartum) and children (age ½, 1½ and 6 years). We examined associations between pregnancy and childhood PFOS and PFOA exposure and childhood infections, asthma, allergic sensitization, atopic dermatitis, and lung function measures, and studied potential mechanisms by integrating data on systemic low-grade inflammation (hs-CRP), functional immune responses, and epigenetics.

FINDINGS

Higher maternal PFOS and PFOA exposure during pregnancy showed association with a non-atopic asthma phenotype by age 6, a protection against sensitization, and no association with atopic asthma or lung function, or atopic dermatitis. The effect was primarily driven by prenatal exposure. There was no association with infection proneness, low-grade inflammation, altered immune responses or epigenetic changes.

INTERPRETATIONS

Prenatal exposure to PFOS and PFOA, but not childhood exposure, specifically increased the risk of low prevalent non-atopic asthma, whereas there was no effect on atopic asthma, lung function, or atopic dermatitis.

FUNDING

All funding received by COPSAC are listed on www.copsac.com. The Lundbeck Foundation (Grant no R16-A1694); The Novo Nordic Foundation (Grant nos NNF20OC0061029, NNF170C0025014, NNF180C0031764); The Ministry of Health (Grant no 903516); Danish Council for Strategic Research (Grant no 0603-00280B); and The Capital Region Research Foundation have provided core support to the COPSAC research center. COPSAC acknowledges the National Facility for Exposomics (SciLifeLab, Sweden) for supporting calibration of the untargeted metabolomics PFAS data. BC and AS has received funding for this project from the European Union's Horizon 2020 research and innovation programme (BC: grant agreement No. 946228 DEFEND; AS: grant agreement No. 864764 HEDIMED).

Risk Factors and Age-Related Patterns of Asthma-Like Symptoms in Early Childhood

BACKGROUND

Episodes of asthma-like symptoms in young children are common, but little is known about risk factors and their patterns for the daily symptom burden.

OBJECTIVE

We investigated a variety of possible risk factors and their age-related impact on the number of asthma-like episodes during age 0 to 3 years.

METHODS

The study population included 700 children from the Copenhagen Prospective Studies on Asthma in Childhood2010 mother-child cohort followed prospectively from birth. Asthma-like symptoms were recorded until age 3 by daily diaries. Risk factors were analyzed by quasi-Poisson regressions, and interaction with age was explored.

RESULTS

Diary data were available in 662 children. Male sex, maternal asthma, low birth weight, maternal antibiotic use, high asthma exacerbation polygenic risk score, and high airway immune score were associated with a higher number of episodes in a multivariable analysis. Maternal asthma, preterm birth, caesarean section, and low birth weight showed an increasing impact with age, whereas sibling(s) at birth showed a decreased association with age. The remaining risk factors had a stable pattern during age 0 to 3 years. For every additional clinical risk factor (male sex, low birth weight, and maternal asthma) a child had, we found 34% more episodes (incidence rate ratio: 1.34, 95% confidence interval: 1.21-1.48; P < .001).

CONCLUSION

Using unique day-to-day diary recordings, we identified risk factors for the burden of asthma-like symptoms in the first 3 years of life and described their unique age-related patterns. This provides novel insight into the origin of asthma-like symptoms in early childhood that potentially pave a path for personalized prognostics and treatment.

Genome-wide study of early and severe childhood asthma identifies interaction between CDHR3 and GSDMB

BACKGROUND

Asthma with severe exacerbation is one of the most common causes of hospitalization among young children. Exacerbations are typically triggered by respiratory infections, but the host factors causing recurrent infections and exacerbations in some children are poorly understood. As a result, current treatment options and preventive measures are inadequate.

OBJECTIVE

We sought to identify genetic interaction associated with the development of childhood asthma.

METHODS

We performed an exhaustive search for pairwise interaction between genetic single nucleotide polymorphisms using 1204 cases of a specific phenotype of early childhood asthma with severe exacerbations in patients aged 2 to 6 years combined with 5328 nonasthmatic controls. Replication was attempted in 3 independent populations, and potential underlying immune mechanisms were investigated in the COPSAC2010 and COPSAC2000 birth cohorts.

RESULTS

We found evidence of interaction, including replication in independent populations, between the known childhood asthma loci CDHR3 and GSDMB. The effect of CDHR3 was dependent on the GSDMB genotype, and this interaction was more pronounced for severe and early onset of disease. Blood immune analyses suggested a mechanism related to increased IL-17A production after viral stimulation.

CONCLUSIONS

We found evidence of interaction between CDHR3 and GSDMB in development of early childhood asthma, possibly related to increased IL-17A response to viral infections. This study demonstrates the importance of focusing on specific disease subtypes for understanding the genetic mechanisms of asthma.

Effects of prenatal nutrient supplementation and early life exposures on neurodevelopment at age 10: a randomised controlled trial - the COPSYCH study protocol

INTRODUCTION

Nutrient deficiency and immune and inflammatory disturbances in early life may compromise neurodevelopment and be implicated in the aetiology of psychiatric disorders. However, current evidence is limited by its predominantly observational nature. COpenhagen Prospective Study on Neuro-PSYCHiatric Development (COPSYCH) is a research alliance between Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) and Center for Clinical Intervention and Neuropsychiatric Schizophrenia Research with the overall aim to investigate effects of prenatal and early life exposures on neurodevelopment at 10 years. COPSYCH will investigate the impact of prenatal n-3 long-chain polyunsaturated fatty acids (n-3 LCPUFA) and high-dose vitamin D supplementation on neurodevelopment reflected by brain development, neurocognition and psychopathology. Moreover, the neurodevelopmental impact of early life exposures such as infections, low grade inflammation and the gut microbiome will be scrutinised.

METHODS AND ANALYSIS

COPSYCH is based on the prospective and ongoing COPSAC2010 birth cohort of 700 mother-child pairs. Randomised controlled trials of supplementation with n-3 LCPUFA and/or high-dose vitamin D or placebo in the third trimester were embedded in a factorial 2×2 design (ClinicalTrials.gov: NCT01233297 and NCT00856947). This unique cohort provides deep phenotyping data from 14 previous clinical follow-up visits and exposure assessments since birth. The ongoing 10-year visit is a 2-day visit. Day 1 includes a comprehensive neurocognitive examination, and assessment of psychopathological dimensions, and assessment of categorical psychopathology. Day 2 includes acquisition of brain structural, diffusion and functional sequences using 3 Tesla MRI. Study outcomes are neurocognitive, psychopathological and MRI measures.

ETHICS AND DISSEMINATION

This study has been approved by the Danish National Committee on Health Research Ethics and The Danish Data Protection Agency. The study is conducted in accordance with the guiding principles of the Declaration of Helsinki. Parents gave written informed consent before enrolment.

Neonatal airway immune profiles and asthma and allergy endpoints in childhood

BACKGROUND

The immune system plays a key role in the pathogenesis of asthma and allergy, but the role of the airway cytokine and chemokine composition in vivo in early life prior to symptom development has not been described previously. Here, we aimed to examine whether the neonatal airway immune composition associates with development of allergy and asthma in childhood.

METHODS

We measured unstimulated levels of 20 immune mediators related to the Type 1, Type 2, Type 17, or regulatory immune pathways in the airway mucosal lining fluid of 620 one-month-old healthy neonates from the COPSAC₂₀₁₀ birth cohort. Allergy and asthma were diagnosed at our research clinic by predefined algorithms and objective assessments at age 6 years. Principal component analyses were used to describe the airway cytokine and chemokine composition.

RESULTS

A neonatal airway immune profile particularly characterized by enhanced IL-1β and reduced CCL26 was significantly associated with later development of elevated specific IgE to inhaled allergens, a positive skin prick test, and allergic rhinitis, but not with food sensitization. Conversely, reduced Type 17 immune-associated markers, including IL-1β and CXCL8, showed trend of association with development of early asthma endpoints.

CONCLUSIONS

Development of early asthma endpoints and inhalant allergy during the first 6 years of life seems associated with distinctly perturbed airway immune profiles in neonatal life, which is suggestive of an early origin and different pathogenesis of childhood asthma and allergy. These exploratory findings suggest pre- and perinatal life as an important window of opportunity for prevention of asthma and inhalant allergy.

Bifidobacterium species associated with breastfeeding produce aromatic lactic acids in the infant gut

Breastfeeding profoundly shapes the infant gut microbiota, which is critical for early life immune development, and the gut microbiota can impact host physiology in various ways, such as through the production of metabolites. However, few breastmilk-dependent microbial metabolites mediating host-microbiota interactions are currently known. Here, we demonstrate that breastmilk-promoted Bifidobacterium species convert aromatic amino acids (tryptophan, phenylalanine and tyrosine) into their respective aromatic lactic acids (indolelactic acid, phenyllactic acid and 4-hydroxyphenyllactic acid) via a previously unrecognized aromatic lactate dehydrogenase (ALDH). The ability of Bifidobacterium species to convert aromatic amino acids to their lactic acid derivatives was confirmed using monocolonized mice. Longitudinal profiling of the faecal microbiota composition and metabolome of Danish infants (n = 25), from birth until 6 months of age, showed that faecal concentrations of aromatic lactic acids are correlated positively with the abundance of human milk oligosaccharide-degrading Bifidobacterium species containing the ALDH, including Bifidobacterium longum, B. breve and B. bifidum. We further demonstrate that faecal concentrations of Bifidobacterium-derived indolelactic acid are associated with the capacity of these samples to activate in vitro the aryl hydrocarbon receptor (AhR), a receptor important for controlling intestinal homoeostasis and immune responses. Finally, we show that indolelactic acid modulates ex vivo immune responses of human CD4+ T cells and monocytes in a dose-dependent manner by acting as an agonist of both the AhR and hydroxycarboxylic acid receptor 3 (HCA3). Our findings reveal that breastmilk-promoted Bifidobacterium species produce aromatic lactic acids in the gut of infants and suggest that these microbial metabolites may impact immune function in early life.

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.

Early Microbial-Immune Interactions and Innate Immune Training of the Respiratory System during Health and Disease

Over the past two decades, several studies have positioned early-life microbial exposure as a key factor for protection or susceptibility to respiratory diseases. Birth cohorts have identified a strong link between neonatal bacterial colonization of the nasal airway and gut with the risk for respiratory infections and childhood asthma. Translational studies have provided companion mechanistic insights on how viral and bacterial exposures in early life affect immune development at the respiratory mucosal barrier. In this review, we summarize and discuss our current understanding of how early microbial–immune interactions occur during infancy, with a particular focus on the emergent paradigm of “innate immune training”. Future human-based studies including newborns and infants are needed to inform the timing and key pathways implicated in the development, maturation, and innate training of the airway immune response, and how early microbiota and virus exposures modulate these processes in the respiratory system during health and disease.

Maternal Microbiota, Early Life Colonization and Breast Milk Drive Immune Development in the Newborn

The innate immune system is the oldest protection strategy that is conserved across all organisms. Although having an unspecific action, it is the first and fastest defense mechanism against pathogens. Development of predominantly the adaptive immune system takes place after birth. However, some key components of the innate immune system evolve during the prenatal period of life, which endows the newborn with the ability to mount an immune response against pathogenic invaders directly after birth. Undoubtedly, the crosstalk between maternal immune cells, antibodies, dietary antigens, and microbial metabolites originating from the maternal microbiota are the key players in preparing the neonate’s immunity to the outer world. Birth represents the biggest substantial environmental change in life, where the newborn leaves the protective amniotic sac and is exposed for the first time to a countless variety of microbes. Colonization of all body surfaces commences, including skin, lung, and gastrointestinal tract, leading to the establishment of the commensal microbiota and the maturation of the newborn immune system, and hence lifelong health. Pregnancy, birth, and the consumption of breast milk shape the immune development in coordination with maternal and newborn microbiota. Discrepancies in these fine-tuned microbiota interactions during each developmental stage can have long-term effects on disease susceptibility, such as metabolic syndrome, childhood asthma, or autoimmune type 1 diabetes. In this review, we will give an overview of the recent studies by discussing the multifaceted emergence of the newborn innate immune development in line with the importance of maternal and early life microbiota exposure and breast milk intake.

Characteristics and Mechanisms of a Sphingolipid-associated Childhood Asthma Endotype

Rationale: A link among sphingolipids, 17q21 genetic variants, and childhood asthma has been suggested, but the underlying mechanisms and characteristics of such an asthma endotype remain to be elucidated.Objectives: To study the sphingolipid-associated childhood asthma endotype using multiomic data.Methods: We used untargeted liquid chromatography-mass spectrometry plasma metabolomic profiles at the ages of 6 months and 6 years from more than 500 children in the COPSAC₂₀₁₀ (Copenhagen Prospective Studies on Asthma in Childhood) birth cohort focusing on sphingolipids, and we integrated the 17q21 genotype and nasal gene expression of SPT (serine palmitoyl-CoA transferase) (i.e., the rate-limiting enzyme in de novo sphingolipid synthesis) in relation to asthma development and lung function traits from infancy until the age 6 years. Replication was sought in the independent VDAART (Vitamin D Antenatal Asthma Reduction Trial) cohort.Measurements and Main Results: Lower concentrations of ceramides and sphingomyelins at the age of 6 months were associated with an increased risk of developing asthma before age 3, which was also observed in VDAART. At the age of 6 years, lower concentrations of key phosphosphingolipids (e.g., sphinganine-1-phosphate) were associated with increased airway resistance. This relationship was dependent on the 17q21 genotype and nasal SPT gene expression, with significant interactions occurring between the genotype and the phosphosphingolipid concentrations and between the genotype and SPT expression, in which lower phosphosphingolipid concentrations and reduced SPT expression were associated with increasing numbers of at-risk alleles. However, the findings did not pass the false discovery rate threshold of <0.05.Conclusions: This exploratory study suggests the existence of a childhood asthma endotype with early onset and increased airway resistance that is characterized by reduced sphingolipid concentrations, which are associated with 17q21 genetic variants and expression of the SPT enzyme.

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.

Human β-Defensin 2 Mutations Are Associated With Asthma and Atopy in Children and Its Application Prevents Atopic Asthma in a Mouse Model

Asthma and allergies are complex, chronic inflammatory diseases in which genetic and environmental factors are crucial. Protection against asthma and allergy development in the context of farming environment is established by early animal contact, unpasteurized milk consumption and gut microbiota maturation. The human β-defensin 2 (hBD-2) is a host defense peptide present almost exclusively in epithelial tissues, with pronounced immunomodulatory properties, which has recently been shown to ameliorate asthma and IBD in animal models. We hypothesized that adequate hBD-2 secretion plays a role in the protection against asthma and allergy development and that genetic variations in the complex gene locus coding for hBD-2 may be a risk factor for developing these diseases, if as a consequence, hBD-2 is insufficiently produced. We used MALDI-TOF MS genotyping, sequencing and a RFLP assay to study the genetic variation including mutations, polymorphisms and copy number variations in the locus harboring both genes coding for hBD-2 (DEFB4A and DEFB4B). We administered hBD-2 orally in a mouse model of house dust mite (HDM)-asthma before allergy challenge to explore its prophylactic potential, thereby mimicking a protective farm effect. Despite the high complexity of the region harboring DEFB4A and DEFB4B we identified numerous genetic variants to be associated with asthma and allergy in the GABRIELA Ulm population of 1,238 children living in rural areas, including rare mutations, polymorphisms and a lack of the DEFB4A. Furthermore, we found that prophylactic oral administration of hBD-2 significantly curbed lung resistance and pulmonary inflammation in our HDM mouse model. These data indicate that inadequate genetic capacity for hBD-2 is associated with increased asthma and allergy risk while adequate and early hBD-2 administration (in a mouse model) prevents atopic asthma. This suggests that hBD-2 could be involved in the protective farm effect and may be an excellent candidate to confer protection against asthma development.

Primary prevention of asthma: from risk and protective factors to targeted strategies for prevention

Asthma is a complex disease that often starts in childhood. Genomic and environmental factors as well as aberrant immune maturation early in life can contribute to the onset of disease, with great disparity over time and geographical regions. Epidemiological studies have scrutinised environmental exposures and attempted to translate these exposures into prevention strategies. Some approaches for patients with asthma have been successful (eg, smoking ban, the Finnish Asthma Programme), and primary prevention of wheeze in pre-school children (age 0-5 years) by the supplementation of vitamin D or fish oil, or both, to pregnant women seems promising. Several recent prevention initiatives are based on strong asthma-protective environmental microbial exposures associated with traditional rural lifestyles. Preclinical studies with various bacterial lysates, bacterial and dietary metabolites, or helminthic compounds have yielded promising results that await translation into clinical practice. Given the immense societal and individual burden of asthma, there is an urgent need to further develop novel strategies to eradicate the disease.