Susceptibility to Lower Respiratory Infections in Childhood is Associated with Perturbation of the Cytokine Response to Pathogenic Airway Bacteria

Genetic predisposition to high BMI increases risk of early life respiratory infections and episodes of severe wheeze and asthma

BACKGROUND

High body mass index (BMI) is an established risk factor for asthma, but the underlying mechanisms remain unclear.

OBJECTIVE

To increase understanding of the BMI-asthma relationship by studying the association between genetic predisposition to higher BMI and asthma, infections and other asthma traits during childhood.

METHODS

Data were obtained from the two ongoing Copenhagen Prospective Studies on Asthma in Childhood (COPSAC) mother-child cohorts. Polygenic risk scores for adult BMI were calculated for each child. Replication was done in the large-scale register-based Integrative Psychiatric Research (iPSYCH) cohort using data on hospitalisation for asthma and infections.

RESULTS

In the COPSAC cohorts (n=974), the adult BMI polygenic risk score was significantly associated with lower respiratory tract infections (incidence rate ratio (IRR) 1.20, 95% CI 1.08-1.33, false discovery rate p-value (pFDR)=0.005) at age 0-3 years and episodes of severe wheeze (IRR 1.30, 95% CI 1.06-1.60, pFDR=0.04) at age 0-6 years. Lower respiratory tract infections partly mediated the association between the adult BMI polygenic risk score and severe wheeze (proportion mediated: 0.59, 95% CI 0.28-2.24, p-value associated with the average causal mediation effect (pACME)=2e-16). In contrast, these associations were not mediated through the child's current BMI and the polygenic risk score was not associated with an asthma diagnosis or reduced lung function up to age 18 years. The associations were replicated in iPSYCH (n=114 283), where the adult BMI polygenic risk score significantly increased the risk of hospitalisations for lower respiratory tract infections and wheeze or asthma throughout childhood to age 18 years.

CONCLUSION

Children with genetic predisposition to higher BMI had increased risk of lower respiratory tract infections and severe wheeze, independent of the child's current BMI. These results shed further light on the complex relationship between body mass BMI and asthma.

Patient-derived pathogenic microbe deposition enhances exposure risk in pediatric clinics

Healthcare-associated infections (HAIs) pose significant risks to pediatric patients in outpatient settings. To prevent HAIs, understanding the sources and transmission routes of pathogenic microorganisms is crucial. This study aimed to identify the sources of opportunistic bacterial pathogens (OBPs) in pediatric outpatient settings and determine their transmission routes. Furthermore, assessing the public health risks associated with the core OBPs is important. We collected 310 samples from various sites in pediatric outpatient areas and quantified the bacteria using qPCR and CFU counting. We also performed 16S rRNA gene and single-bacterial whole-genome sequencing to profile the transmission routes and antibiotic resistance characteristics of OBPs. We observed significant variations in microbial diversity and composition among sampling sites in pediatric outpatient settings, with active communication of the microbiota between linked areas. We found that the primary source of OBPs in multi-person contact areas was the hand surface, particularly in pediatric patients. Five core OBPs, Staphylococcus epidermidis, Acinetobacter baumannii, Pseudomonas aeruginosa, Streptococcus mitis, and Streptococcus oralis, were mainly derived from pediatric patients and spread into the environment. These OBPs accumulated at multi-person contact sites, resulting in high microbial diversity in these areas. Transmission tests confirmed the challenging spread of these pathogens, with S. epidermidis transferring from the patient's hand to the environment, leading to an increased abundance and emergence of related strains. More importantly, S. epidermidis isolated from pediatric patients carried more antibiotic-resistance genes. In addition, two strains of multidrug-resistant A. baumannii were isolated from both a child and a parent, confirming the transmission of the five core OBPs centered around pediatric patients and multi-person contact areas. Our results demonstrate that pediatric patients serve as a significant source of OBPs in pediatric outpatient settings. OBPs carried by pediatric patients pose a high public health risk. To effectively control HAIs, increasing hand hygiene measures in pediatric patients and enhancing the frequency of disinfection in multi-person contact areas remains crucial. By targeting these preventive measures, the spread of OBPs can be reduced, thereby mitigating the risk of HAIs in pediatric outpatient settings.

Bacterial colonisation of the airway in neonates and risk of asthma and allergy until age 18 years

BACKGROUND

We previously showed an association between neonatal bacterial airway colonisation and increased risk of persistent wheeze/asthma until age 5 years. Here, we study the association with persistent wheeze/asthma and allergy-related traits until age 18 years.

METHODS

We investigated the association between airway colonisation with Streptococcus pneumoniae, Moraxella catarrhalis and/or Haemophilus influenzae in 1-month-old neonates from the COPSAC2000 mother-child cohort and the development of persistent wheeze/asthma and allergy-related traits longitudinally until age 18 years using generalised estimating equations. Replication was sought in the similarly designed COPSAC2010 cohort of 700 children.

RESULTS

Neonatal airway colonisation was present in 66 (21%) out of 319 children and was associated with a 4-fold increased risk of persistent wheeze/asthma (adjusted OR 4.01 (95% CI 1.76-9.12); p<0.001) until age 7 years, but not from age 7 to 18 years. Replication in the COPSAC2010 cohort showed similar results using 16S data. Colonisation was associated with an increased number of exacerbations (adjusted incidence rate ratio 3.20 (95% CI 1.38-7.44); p<0.01) until age 7 years, but not from age 7 to 18 years. Colonisation was associated with increased levels of blood eosinophils (adjusted geometric mean ratio 1.24 (95% CI 1.06-1.44); p<0.01) and tumour necrosis factor (TNF)-α (adjusted geometric mean ratio 1.09 (95% CI 1.02-1.16); p=0.01) until age 12 years. There were no associations with lung function, bronchial reactivity, fractional exhaled nitric oxide, allergic sensitisation, total IgE or atopic dermatitis up to age 18 years.

CONCLUSIONS

Neonatal airway colonisation was associated with early-onset persistent wheeze/asthma, exacerbations, elevated blood eosinophils and elevated TNF-α in blood, most prominent in early childhood, thereafter diminishing and no longer evident by age 18 years.

Functional immunophenotyping of blood neutrophils identifies novel endotypes of viral response in preschool children with recurrent wheezing

BACKGROUND

Preschool children with recurrent wheezing are heterogeneous, with differing responses to respiratory viral infections. Although neutrophils are crucial for host defense, their function has not been studied in this population.

OBJECTIVE

We performed functional immunophenotyping on isolated blood neutrophils from 52 preschool children with recurrent wheezing (aeroallergen sensitization, n = 16; no sensitization, n = 36).

METHODS

Blood neutrophils were purified and cultured overnight with polyinosinic:polycytidylic acid [poly(I:C)] as a viral analog stimulus. Neutrophils underwent next-generation sequencing with Reactome pathway analysis and were analyzed for cytokine secretion, apoptosis, myeloperoxidase, and extracellular DNA release. CD14+ monocytes were also exposed to neutrophil culture supernatant and analyzed for markers of M1 and M2 activation.

RESULTS

A total of 495 genes, related largely to the innate immune system and neutrophil degranulation, were differently expressed in children with versus without aeroallergen sensitization. Functional experiments identified more neutrophil degranulation and extracellular trap formation (ie, more myeloperoxidase and extracellular DNA) and less neutrophil proinflammatory cytokine secretion in children with aeroallergen sensitization. Neutrophils also shifted CD14+ monocytes to a more anti-inflammatory (ie, M2) phenotype in sensitized children and a more proinflammatory (ie, M1) phenotype in nonsensitized children. Although both groups experienced viral exacerbations, annualized exacerbation rates prompting unscheduled health care were also higher in children without aeroallergen sensitization after enrollment.

CONCLUSIONS

Systemic neutrophil responses to viral infection differ by allergic phenotype and may be less effective in preschool children without allergic inflammation. Further studies of neutrophil function are needed in this population, which often has less favorable therapeutic responses to inhaled corticosteroids and other therapies directed at type 2-high inflammation.

Effect of PM2.5 air pollution on the global burden of lower respiratory infections, 1990-2019: A systematic analysis from the Global Burden of Disease Study 2019

Particulate matter (PM) air pollution is closely related to lower respiratory infections (LRIs). However, the global LRI burden attributable to PM remains unclear. Here, we provide a comprehensive assessment of the PM2.5-attributable LRI burden using data from the Global Burden and Disease Study (GBD) 2019. We found that PM2.5 air pollution contributed to approximately 0.7 million deaths and 37.6 million disability-adjusted life years (DALYs) of LRIs in 2019. The LRI burden attributable to PM2.5 has decreased from 1990 to 2019, with a more pronounced decrease in household PM2.5 than in ambient PM2.5. Unlike the decreasing trend in LRI burden due to household PM2.5 worldwide, nearly one fifth of countries experienced an increase of LRI burden due to ambient PM2.5. The burden was unevenly distributed to less developed countries, mainly in Sub-Saharan Africa. All age groups experienced a decrease in the PM2.5-attributable burden, with the most significant decrease in children younger than 10 years. Notably, individuals aged 20-84 years experienced an increase in the LRI burden attributable to ambient PM2.5. Males had higher burden than females in the elder age and higher SDI regions. This study provided an evidence-based guidance for the prevention of LRIs and control of PM2.5 air pollution.

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

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

Trends of Incidence, Mortality, and Risk Factors for Lower Respiratory Infections among Children under 5 Years in China from 2000 to 2019

BACKGROUND

Understanding the temporal trends in the burden of lower respiratory tract infections (LRI) and their attributable risk factors in children under 5 years is important for effective prevention strategies.

METHODS

We used incidence, mortality, and attributable risk factors of LRI among children under 5 years from the Global Burden of Diseases database to analyze health patterns in 33 provincial administrative units in China from 2000 to 2019. Trends were examined using the annual average percentage change (AAPC) by the joinpoint regression method.

RESULTS

The rates of incidence and mortality for under-5 LRI in China were 18.1 and 4134.3 per 100,000 children in 2019, with an AAPC decrease of 4.1% and 11.0% from 2000, respectively. In recent years, the under-5 LRI incidence rate has decreased significantly in 11 provinces (Guangdong, Guangxi, Guizhou, Hainan, Heilongjiang, Jiangxi, Qinghai, Sichuan, Xinjiang, Xizang, and Zhejiang) and remained stable in the other 22 provinces. The case fatality ratio was associated with the Human Development Index and the Health Resource Density Index. The largest decline in risk factors of deaths was household air pollution from solid fuels.

CONCLUSIONS

The burden of under-5 LRI in China and the provinces has declined significantly, with variation across provinces. Further efforts are needed to promote child health through the development of measures to control major risk factors.

Global burden of lower respiratory infections during the last three decades

Background

Lower respiratory infections (LRIs) cause a substantial mortality, morbidity and economic burden. The present study reported the global, regional and national burden of LRIs and their attributable risk factors in 204 countries and territories, between 1990 and 2019, by age, sex, etiology, and Socio-demographic Index (SDI).

Methods

Using publicly available data from the Global Burden of Disease (GBD) study 2019, we reported the incidence, deaths and disability-adjusted life-years (DALYs), due to LRIs. Estimates were presented as counts and age-standardized rates per 100,000 population with their associated uncertainty intervals (UIs).

Results

Globally, in 2019 there were 488.9 million (95% UI: 457.6 to 522.6) incident cases and 2.4 million (2.3-2.7) deaths due to LRIs. The global age-standardized incidence and death rates for LRIs were 6,295 (5,887.4-6,737.3) and 34.3 (31.1-37.9) per 100,000 in 2019, which represents a 23.9% (22.5-25.4) and 48.5% (42.9-54.0) decrease, respectively since 1990. In 2019, Guinea [12,390.4 (11,495.5-13,332.8)], Chad [12,208.1 (11,289.3-13,202.5)] and India [11,862.1 (11,087.0-12,749.0)] had the three highest age-standardized incidence rates of LRI. Equatorial Guinea [-52.7% (95% UI: -55.8 to -49.3)], Chile [-50.2% (95% UI: -53.4 to -47.0)] and Albania [-48.6% (95% UI: -51.7 to -45.3)] showed the largest decreases from 1990 to 2019. In 2019, a decrease in the incidence rate of LRI was observed at the global level up to the 25-29 age group, then the incidence rates increased with age. The burden of LRIs decreased with increasing SDI at both the regional and national levels. Globally, child wasting (33.1%), household air pollution from solid fuels (24.9%) and a lack of access to handwashing facilities (14.4%) made the largest contributions to the LRI burden in 2019.

Conclusions

Although the burden of LRIs decreased over the period 1990-2019, LRIs still contribute to a large number of incident cases, deaths and DALYs. Preventative programs with a focus on reducing exposure to attributable risk factors should be implemented, especially in less developed countries.

The Changes in Bacterial Microbiome Associated with Immune Disorder in Allergic Respiratory Disease

Allergic respiratory disease is a worldwide and increasingly prevalent health problem. Many researchers have identified complex changes in the microbiota of the respiratory and intestinal tracts in patients with allergic respiratory diseases. These affect immune response and influence the progression of disease. However, the diversity of bacterial changes in such cases make it difficult to identify a specific microorganism to target for adjustment. Recent research evidence suggests that common bacterial variations present in allergic respiratory disease are associated with immune disorders. This finding could lead to the discovery of potential therapeutic targets in cases of allergic respiratory disease. In this review, we summarize current knowledge of bacteria changes in cases of allergic respiratory disease, to identify changes commonly associated with immune disorders, and thus provide a theoretical basis for targeting therapies of allergic respiratory disease through effective modulation of key bacteria.

Nasopharyngeal microbial profiles associated with the risk of airway allergies in early childhood

BACKGROUND

Airway microbiota may play an important role in regulating the immune response related to allergic respiratory diseases. A molecular-based approach was used to analyze the association between nasopharyngeal microbiota, serum immunoglobin (Ig)E levels, and childhood respiratory allergies.

METHODS

Nasopharyngeal swabs were collected from children aged 36 months with three phenotypes, including allergic respiratory diseases plus atopy, atopy alone, and healthy controls for microbiome analysis using Illumina-based 16S rRNA gene sequencing.

RESULTS

In total, 87 children were enrolled, including 36 with allergic respiratory diseases plus atopy, 21 with atopy alone, and 30 healthy controls. Proteobacteria (45.7%), Firmicutes (29.3%), and Actinobacteria (15.3%) were the most prevalent phyla in the study population. Compared with healthy controls, a lower Chao1 index was found in children with allergies (P < 0.035), indicating that bacterial richness was inversely associated with airway allergies. Additionally, in comparison with healthy controls, the genera Acinetobacter, Moraxella, Asaia, and Rhodococcus were more abundant and positively correlated with total serum IgE levels in children with allergies (P < 0.01), whereas the genera Enterococcus and Rickettsia were inversely correlated with total IgE levels, and also appeared to be negatively associated with airway allergies (P < 0.01).

CONCLUSIONS

The composition of the nasopharyngeal microbiota alteration may have an influence on childhood respiratory allergies. The inverse association between bacterial richness and allergies postulated that children living in a microbially hygienic environment may increase their risk of developing respiratory allergies.

Emerging cellular and molecular interactions between the lung microbiota and lung diseases

With the discovery of the lung microbiota, its study in both pulmonary health and disease has become a vibrant area of emerging research interest. Thus far, most studies have described the lung microbiota composition in lung disease quite well, and some of these studies indicated alterations in lung microbial communities related to the onset and development of lung disease and vice versa. However, the underlying mechanisms, particularly the cellular and molecular links, are still largely unknown. In this review, we highlight the current progress in the complex cellular and molecular mechanisms by which the lung microbiome interacts with immune homeostasis and pulmonary disease pathogenesis to advance our understanding of the elaborate function of the lung microbiota in lung disease. We hope that this work can attract more attention to this still-young yet very promising field to facilitate the identification of new therapeutic targets and provide more innovative therapies. Additional accurate standard-based methodologies and technological breakthroughs are critical to propel the field forward to ultimately achieve the goal of maintaining respiratory health.

Innate IL-23/Type 17 immune responses mediate the effect of the 17q21 locus on childhood asthma

BACKGROUND

Several childhood asthma risk loci that relate to immune function have been identified by genome-wide association studies (GWAS), but the underlying mechanisms remain unknown.

OBJECTIVE

Here, we examined whether perturbed innate immune responses mediate the association between known genetic risk variants and development of childhood asthma.

METHODS

Peripheral blood mononuclear cells from 336 six-month-old infants from the Copenhagen Prospective Studies on Asthma in Childhood (COPSAC₂₀₀₀ ) cohort were stimulated in vitro with six different innate ligands (LPS, CpG, poly(I:C), R848, HDMAPP and aluminium hydroxide together with low levels of LPS) followed by quantification of 18 released cytokines and chemokines 40 h after the stimulations. The innate immune response profiles were decomposed by principal component (PC) analysis, and PC1-5 were used in mediation analyses of the effect of 25 known genetic risk variants on childhood asthma until age 7.

RESULTS

The effects of two variants from the 17q21 locus (rs7216389, rs2305480) on asthma and exacerbation risk were significantly mediated by immune parameters induced in response to ligands mimicking intracellular colonization; bacterial DNA (CpG) and double-stranded viral RNA (poly(I:C)). The Th17 and innate lymphoid cell type 3-amplifying cytokine IL-23 was the most prominent cytokine involved.

CONCLUSION

The 17q21 effect on childhood asthma and exacerbations was partly mediated by deregulation of IL-23 in response to intracellular microbial ligands, which may suggest ineffective clearance of intracellular pathogens in the lungs.

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.

Reduced IL-2 response from peripheral blood mononuclear cells exposed to bacteria at 6 months of age is associated with elevated total-IgE and allergic rhinitis during the first 7 years of life

BACKGROUND

Autoimmunity and allergy have been associated with decreased number and function of regulatory T-cells (Tregs) and low interleukin-2 (IL-2) levels. We aimed to investigate if the release of IL-2 from peripheral blood mononuclear cells (PBMCs) stimulated with pathogenic airway bacteria was associated with development of allergy-outcomes in early childhood.

METHODS

PBMCs were isolated at age 6 months in 331 infants from the Copenhagen Prospective Studies on Asthma in Childhood 2000 (COPSAC2000) mother-child cohort, and subsequently stimulated with H. influenzae, M. catarrhalis and S. pneumoniae in in vitro cultures. Levels of cytokines (IL-2, IL-10, IFN-γ, TNF-α, IL-5, IL-13 and IL-17A) were determined in the supernatant by electrochemiluminescence immunoassays. The immune profiles were analyzed for association with development of total-IgE, allergic sensitization and rhinitis during the first 7 years of life using regression models and principal component analysis (PCA).

FINDINGS

An attenuated IL-2 response to stimulation with H. influenzae (p = 0∙011) and M. catarrhalis (p = 0∙027) was associated with elevated total-IgE at age 7, which was confirmed in a multivariate PCA model including all cytokine measurements (PC2, p = 0∙032). An immune profile with both reduced IL-2 and elevated IL-5 was associated with increased risk of allergic rhinitis (PC3, p = 0∙038). We found no associations with development of allergic sensitization.

INTERPRETATION

A reduced IL-2 response from PBMCs exposed to common pathogenic airway bacteria at age 6 months was associated with elevated total-IgE and allergic rhinitis during the first 7 years of life. These findings suggest that suppressed Treg activity in early life may herald onset of allergy in early childhood, which could be a target for low-dose IL-2 trials in the future. FUND: COPSAC is funded by private and public research funds all listed on www.copsac.com.

Neonates colonized with pathogenic bacteria in the airways have a low-grade systemic inflammation

BACKGROUND AND OBJECTIVES

The development of childhood asthma is associated with neonatal colonization with pathogenic bacteria in hypopharynx. Furthermore, established asthma is associated with systemic low-grade inflammation. We here report on the association between neonatal colonization with pathogenic bacteria in hypopharynx and the development of systemic low-grade inflammation.

METHODS

Bacterial colonization of the hypopharynx with Moraxella catharralis, Haemophilus influenzae, and/or Streptococcus pneumoniae was assessed in asymptomatic children from the Copenhagen Prospective Studies on Asthma in Childhood₂₀₀₀ (COPSAC₂₀₀₀ ) cohort at age 1 month by culturing technique (N = 238) and by quantitative polymerase chain reaction (qPCR) technique (N = 249) and in the COPSAC₂₀₁₀ cohort by culturing at age 1 month (N = 622) and again at age 3 months (N = 613). Systemic low-grade inflammation was determined in both cohorts at age 6 months by measuring plasma levels of high-sensitivity C-reactive protein (hs-CRP), tumor necrosis factor-α (TNF-α), and interleukin-6 (lL-6).

RESULTS

In both cohorts, bacterial colonization was associated with increased levels of hs-CRP: COPSAC₂₀₀₀ , 1 month culturing (geometric mean ratio of colonized/noncolonized [95% CI]), 1.39 [0.97-2.01], P = .08; 1 month qPCR, 1.55 [1.14-2.10], P < .01; COPSAC₂₀₁₀ , 1 month, 1.52 [1.23-1.87], P < .01; and 3 month, 1.57 [1.30-1.90], P < .01. A multiparametric principal component analysis incorporating hs-CRP, TNF-α, and IL-6 confirmed a systemic inflammatory profile in children colonized with M. catharralis, H. influenzae. and/or S. pneumoniae in the hypopharynx compared to noncolonized children (P-values < .05).

CONCLUSION

The composition of the upper airway microbiome in early life may cause systemic low-grade inflammation.

Epidemiology and Risk Factors of Infection in Early Childhood

BACKGROUND

There is a large, unexplained variation in the frequency of childhood infections. We described incidence and risk factors of infections in early childhood.

METHODS

Simple infections were captured during the first 3 years of life in the Copenhagen Prospective Studies on Asthma in Childhood 2000 birth cohort. Environmental exposures were analyzed by quasi-Poisson regression and sparse principal component analysis.

RESULTS

The 334 children experienced a median of 14 (range 2-43) infectious episodes at ages 0 to 3 years. The overall rate of infections was associated with the number of children in the day care (adjusted incidence rate ratio [aIRR] 1.09 [1.2-1.16]) and the m² per child in the day care (aIRR 0.96 [0.92-0.99]). Upper respiratory infections were also associated with the number of children in the day care (aIRR 1.11 [1.03-1.20]) and the m² per child in the day care (aIRR 0.95 [0.91-0.99]), whereas lower respiratory infections were associated with caesarean section (aIRR 1.49 [1.12-1.99]), maternal smoking (aIRR 1.66 [1.18-2.33]), older siblings (aIRR 1.54 [1.19-2.01]), and the age at entry to day care (aIRR 0.77 [0.65-0.91]). The sparse principal component analysis revealed a risk factor profile driven by tobacco exposure, social circumstances, and domestic pets, but could only be used to explain 8.4% of the infection burden.

CONCLUSIONS

Children experienced around 14 infections during the first 3 years of life, but incidences varied greatly. Environmental exposures only explained a small fraction of the variation, suggesting host factors as major determinants of infectious burden.

Rhinovirus and preschool wheeze

Rhinovirus (RV) known as the common cold virus generally only causes a mild upper respiratory infection, but severe lower respiratory symptoms have been associated with RV infections especially in asthmatic individuals. Wheezing is a symptom of airway obstruction, and preschool children wheezing with RV have been associated with increased risk of asthma at school age. There are, however, conflicting opinions as to whether there are differences in response to RV infection or whether wheezing with RV reveals a preexisting impairment that promotes asthma mainly in predisposed children. The advent of molecular diagnostics to detect respiratory viruses has led to new insights into the role of RV infections. This review will discuss recent information concerning the role of RV as an important respiratory pathogen related to early onset wheeze and exacerbation of established asthma in preschool children.

Lessons learned from birth cohort studies conducted in diverse environments

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

Airway Microbiota and the Implications of Dysbiosis in Asthma

The mucosal surfaces of the human body are typically colonized by polymicrobial communities seeded in infancy and are continuously shaped by environmental exposures. These communities interact with the mucosal immune system to maintain homeostasis in health, but perturbations in their composition and function are associated with lower airway diseases, including asthma, a developmental and heterogeneous chronic disease with various degrees and types of airway inflammation. This review will summarize recent studies examining airway microbiota dysbioses associated with asthma and their relationship with the pathophysiology of this disease.

Cord blood Streptococcus pneumoniae-specific cellular immune responses predict early pneumococcal carriage in high-risk infants in Papua New Guinea

In areas where Streptococcus pneumoniae is highly endemic, infants experience very early pneumococcal colonization of the upper respiratory tract, with carriage often persisting into adulthood. We aimed to explore whether newborns in high‐risk areas have pre‐existing pneumococcal‐specific cellular immune responses that may affect early pneumococcal acquisition. Cord blood mononuclear cells (CBMC) of 84 Papua New Guinean (PNG; high endemic) and 33 Australian (AUS; low endemic) newborns were stimulated in vitro with detoxified pneumolysin (dPly) or pneumococcal surface protein A (PspA; families 1 and 2) and compared for cytokine responses. Within the PNG cohort, associations between CBMC dPly and PspA‐induced responses and pneumococcal colonization within the first month of life were studied. Significantly higher PspA‐specific interferon (IFN)‐γ, tumour necrosis factor (TNF)‐α, interleukin (IL)‐5, IL‐6, IL‐10 and IL‐13 responses, and lower dPly‐IL‐6 responses were produced in CBMC cultures of PNG compared to AUS newborns. Higher CBMC PspA‐IL‐5 and PspA‐IL‐13 responses correlated with a higher proportion of cord CD4 T cells, and higher dPly‐IL‐6 responses with a higher frequency of cord antigen‐presenting cells. In the PNG cohort, higher PspA‐specific IL‐5 and IL‐6 CBMC responses were associated independently and significantly with increased risk of earlier pneumococcal colonization, while a significant protective effect was found for higher PspA‐IL‐10 CBMC responses. Pneumococcus‐specific cellular immune responses differ between children born in pneumococcal high versus low endemic settings, which may contribute to the higher risk of infants in high endemic settings for early pneumococcal colonization, and hence disease.