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.

A computerized decision support tool to implement asthma guidelines for children and adolescents

BACKGROUND

Multicenter randomized controlled trials (RCTs) for asthma management that incorporate usual-care regimens could benefit from standardized application of evidence-based guidelines.

OBJECTIVE

We sought to evaluate performance of a computerized decision support tool, the Asthma Control Evaluation and Treatment (ACET) Program, to standardize usual-care regimens for asthma management in RCTs.

METHODS

Children and adolescents with persistent uncontrolled asthma living in urban census tracts were recruited into 3 multicenter RCTs (each with a usual-care arm) between 2004 and 2014. A computerized decision support tool scored asthma control and assigned an appropriate treatment step based on published guidelines. Control-level determinants (symptoms, rescue medication use, pulmonary function measure, and adherence estimates) were collected at visits and entered into the ACET Program. Changes in control levels and treatment steps were examined during the trials.

RESULTS

At screening, more than half of the participants were rated as having symptoms that were not controlled or poorly controlled. The proportion of participants who gained good control between screening and randomization increased significantly in all 3 trials. Between 51% and 70% had symptoms that were well controlled by randomization. The proportion of well-controlled participants remained constant or improved slightly from randomization until the last posttreatment visit. Nighttime symptoms were the most common control-level determinant; there were few (<1%) instances of complete overlap of factors. FEV₁ was the driver of control-level assignment in 30% of determinations.

CONCLUSION

The ACET Program decision support tool facilitated standardized asthma assessment and treatment in multicenter RCTs and was associated with attaining and maintaining good asthma control in most participants.

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.

Obstruction phenotype as a predictor of asthma severity and instability in children

BACKGROUND

Small-airways instability resulting in premature airway closure has been recognized as a risk for asthma severity and poor control. Although spirometry has limited sensitivity for detecting small-airways dysfunction, a focus on the air-trapping component of obstruction might identify a risk factor for asthma instability.

OBJECTIVE

We sought to use spirometric measurements to identify patterns of airway obstruction in children and define obstruction phenotypes that relate to asthma instability.

METHODS

Prebronchodilation and postbronchodilation spirometric data were obtained from 560 children in the Asthma Phenotypes in the Inner City study. An air-trapping obstruction phenotype (A Trpg) was defined as a forced vital capacity (FVC) z score of less than -1.64 or an increase in FVC of 10% of predicted value or greater with bronchodilation. The airflow limitation phenotype (A Limit) had an FEV1/FVC z score of less than -1.64 but not A Trpg. The no airflow limitation or air-trapping criteria (None) phenotype had neither A Trpg nor A Limit. The 3 obstruction phenotypes were assessed as predictors of number of exacerbations, asthma severity, and airway lability.

RESULTS

Patients with the A Trpg phenotype (14% of the cohort) had more exacerbations during the 12-month study compared with those with the A Limit (P < .03) and None (P < .001) phenotypes. Patients with the A Trpg phenotype also had the highest Composite Asthma Severity Index score, the highest asthma treatment step, the greatest variability in FEV1 over time, and the greatest sensitivity to methacholine challenge.

CONCLUSIONS

A Trpg and A Limit patterns of obstruction, as defined by using routine spirometric measurements, can identify obstruction phenotypes that are indicators of risk for asthma severity and instability.

Spirometry and Impulse Oscillometry in Preschool Children: Acceptability and Relationship to Maternal Smoking in Pregnancy

BACKGROUND

Comparisons of the technical acceptability of spirometry and impulse oscillometry (IOS) and clinical correlations of the measurements have not been well studied in young children. There are no large studies focused on African American and Hispanic children.

OBJECTIVES

We sought to (1) compare the acceptability of spirometry and IOS in 3- to 5-year-old children and (2) examine the relationship of maternal smoking during pregnancy to later lung function.

METHODS

Spirometry and IOS were attempted at 4 sites from the Urban Environmental and Childhood Asthma Study birth cohort at ages 3, 4, and 5 years (472, 471, and 479 children, respectively). We measured forced expiratory flow in 0.5 s (forced expiratory volume in 0.5 seconds [FEV0.5]) with spirometry and area of reactance (AX), resistance and reactance at 5 Hz (R5 and X5, respectively) using IOS.

RESULTS

Children were more likely to achieve acceptable maneuvers with spirometry than with IOS at age 3 (60% vs 46%, P < .001) and 5 years (89% vs 84%, P = .02). Performance was consistent among the 4 study sites. In children without recurrent wheeze, there were strong trends for higher FEV0.5 and lower R5 and AX over time. Maternal smoking during pregnancy was associated with higher AX at ages 4 and 5 years (P < .01 for both years). There was no significant difference in FEV0.5 between children with and without in utero exposure to smoking.

CONCLUSION

There is a higher rate of acceptable maneuvers with spirometry compared with IOS, but IOS may be a better indicator of peripheral airway function in preschool children.

Development of Asthma in Inner-City Children: Possible Roles of MAIT Cells and Variation in the Home Environment

Humans have populations of innate-like T lymphocytes with an invariant TCR α-chain that recognize nonpeptide Ags, including invariant NKT (iNKT) cells and mucosal-associated invariant T (MAIT) cells. iNKT cell involvement in human asthma is controversial, whereas there has been little analysis of MAIT cells. Using peripheral blood cells from 110 participants from the Urban Environment and Childhood Asthma (URECA) birth cohort study, these cells were analyzed for number and function. We determined whether iNKT cell or MAIT cell frequency at 1 y is correlated with the cytokine polarization of mainstream CD4+ T cells and/or the development of asthma by age 7 y. Dust samples from 300 houses were tested for iNKT cell antigenic activity. Our results show that a higher MAIT cell frequency at 1 y of age was associated with a decreased risk of asthma by age 7 y. The frequency of MAIT cells was associated with increased production of IFN-γ by activated CD4+ T cells from the URECA cohort. iNKT cell antigenic activity in bedroom dust samples was associated with higher endotoxin concentration and also with reduced risk of asthma. In conclusion, MAIT cell frequency at 1 y may reflect the tendency of the immune system toward Th1 responses and is associated with protection from asthma. Additionally, iNKT cell antigenic activity may be a marker of houses with increased microbial exposures and therefore also with protection from asthma.

Effects of Omalizumab on Rhinovirus Infections, Illnesses, and Exacerbations of Asthma

RATIONALE

Allergic inflammation has been linked to increased susceptibility to viral illnesses, but it is unclear whether this association is causal.

OBJECTIVES

To test whether omalizumab treatment to reduce IgE would shorten the frequency and duration of rhinovirus (RV) illnesses in children with allergic asthma.

METHODS

In the PROSE (Preventative Omalizumab or Step-up Therapy for Severe Fall Exacerbations) study, we examined children with allergic asthma (aged 6-17 yr; n = 478) from low-income census tracts in eight U.S. cities, and we analyzed virology for the groups randomized to treatment with guidelines-based asthma care (n = 89) or add-on omalizumab (n = 259). Weekly nasal mucus samples were analyzed for RVs, and respiratory symptoms and asthma exacerbations were recorded over a 90-day period during the fall seasons of 2012 or 2013. Adjusted illness rates (illnesses per sample) by treatment arm were calculated using Poisson regression.

MEASUREMENTS AND MAIN RESULTS

RVs were detected in 97 (57%) of 171 exacerbation samples and 2,150 (36%) of 5,959 nonexacerbation samples (OR, 2.32; P < 0.001). Exacerbations were significantly associated with detection of rhinovirus C (OR, 2.85; P < 0.001) and rhinovirus A (OR, 2.92; P < 0.001), as well as, to a lesser extent, rhinovirus B (OR, 1.98; P = 0.019). Omalizumab decreased the duration of RV infection (11.2 d vs. 12.4 d; P = 0.03) and reduced peak RV shedding by 0.4 log units (95% confidence interval, -0.77 to -0.02; P = 0.04). Finally, omalizumab decreased the frequency of RV illnesses (risk ratio, 0.64; 95% confidence interval, 0.49-0.84).

CONCLUSIONS

In children with allergic asthma, treatment with omalizumab decreased the duration of RV infections, viral shedding, and the risk of RV illnesses. These findings provide direct evidence that blocking IgE decreases susceptibility to RV infections and illness. Clinical trial registered with www.clinicaltrials.gov (NCT01430403).

Screen Time Engagement Is Increased in Urban Children With Asthma

Physical activity in children has been shown to play a role in its relationship to asthma, both in terms of prevalence and incidence. One measure of physical activity in children is sedentary behavior, which might be measured by the degree of engagement with media electronic screens. We found that children with asthma, as compared with children without asthma, engage in significantly more hours of screen time (median 35 vs 26 h/wk, P = .004). In this birth cohort, those who developed a diagnosis of asthma at 8 years of age were significantly more engaged in electronic screen time than their peers. No other clinical or lifestyle behaviors were significantly associated with a diagnosis of asthma. Further study will be needed to determine directionality of this finding.

Early-life home environment and risk of asthma among inner-city children

BACKGROUND

Environmental exposures in early life appear to play an important role in the pathogenesis of childhood asthma, but the potentially modifiable exposures that lead to asthma remain uncertain.

OBJECTIVE

We sought to identify early-life environmental risk factors for childhood asthma in a birth cohort of high-risk inner-city children.

METHODS

We examined the relationship of prenatal and early-life environmental factors to the occurrence of asthma at 7 years of age among 442 children.

RESULTS

Higher house dust concentrations of cockroach, mouse, and cat allergens in the first 3 years of life were associated with lower risk of asthma (for cockroach allergen: odds ratio per interquartile range increase in concentration, 0.55; 95% CI, 0.36-0.86; P < .01). House dust microbiome analysis using 16S ribosomal RNA sequencing identified 202 and 171 bacterial taxa that were significantly (false discovery rate < 0.05) more or less abundant, respectively, in the homes of children with asthma. A majority of these bacteria were significantly correlated with 1 of more allergen concentrations. Other factors associated significantly positively with asthma included umbilical cord plasma cotinine concentration (odds ratio per geometric SD increase in concentration, 1.76; 95% CI, 1.00-3.09; P = .048) and maternal stress and depression scores.

CONCLUSION

Among high-risk inner-city children, higher indoor levels of pet or pest allergens in infancy were associated with lower risk of asthma. The abundance of a number of bacterial taxa in house dust was associated with increased or decreased asthma risk. Prenatal tobacco smoke exposure and higher maternal stress and depression scores in early life were associated with increased asthma risk.

Omalizumab in children with uncontrolled allergic asthma: Review of clinical trial and real-world experience

Asthma is one of the most common chronic diseases of childhood. Allergen sensitization and high frequencies of comorbid allergic diseases are characteristic of severe asthma in children. Omalizumab, an anti-IgE mAb, is the first targeted biologic therapeutic approved for the treatment of moderate-to-severe persistent allergic asthma (AA) that remains uncontrolled despite high-dose inhaled corticosteroids plus other controller medications. Since its initial licensing for use in adults and adolescents 12 years of age and older, the clinical efficacy, safety, and tolerability of omalizumab have been demonstrated in several published clinical trials in children aged 6 to less than 12 years with moderate-to-severe AA. These studies supported the approval of the pediatric indication (use in children aged ≥6 years) by the European Medicines Agency in 2009 and the US Food and Drug Administration in 2016. After this most recent change in licensing, we review the outcomes from clinical trials in children with persistent AA receiving omalizumab therapy and observational studies from the past 7 years of clinical experience in Europe. Data sources were identified by using PubMed in 2016. Guidelines and management recommendations and materials from the recent US Food and Drug Administration's Pediatric Advisory Committee meeting are also reviewed.

Endotypes of difficult-to-control asthma in inner-city African American children

African Americans have higher rates of asthma prevalence, morbidity, and mortality in comparison with other racial groups. We sought to characterize endotypes of childhood asthma severity in African American patients in an inner-city pediatric asthma population. Baseline blood neutrophils, blood eosinophils, and 38 serum cytokine levels were measured in a sample of 235 asthmatic children (6-17 years) enrolled in the NIAID (National Institute of Allergy and Infectious Diseases)-sponsored Asthma Phenotypes in the Inner City (APIC) study (ICAC (Inner City Asthma Consortium)-19). Cytokines were quantified using a MILLIPLEX panel and analyzed on a Luminex analyzer. Patients were classified as Easy-to-Control or Difficult-to-Control based on the required dose of controller medications over one year of prospective management. A multivariate variable selection procedure was used to select cytokines associated with Difficult-to-Control versus Easy-to-Control asthma, adjusting for age, sex, blood eosinophils, and blood neutrophils. In inner-city African American children, 12 cytokines were significant predictors of Difficult-to-Control asthma (n = 235). CXCL-1, IL-5, IL-8, and IL-17A were positively associated with Difficult-to-Control asthma, while IL-4 and IL-13 were positively associated with Easy-to-Control asthma. Using likelihood ratio testing, it was observed that in addition to blood eosinophils and neutrophils, serum cytokines improved the fit of the model. In an inner-city pediatric population, serum cytokines significantly contributed to the definition of Difficult-to-Control asthma endotypes in African American children. Mixed responses characterized by TH2 (IL-5) and TH17-associated cytokines were associated with Difficult-to-Control asthma. Collectively, these data may contribute to risk stratification of Difficult-to-Control asthma in the African American population.

Allergy and asthma in inner-city children: possible roles of MAIT cells and variation in the home environment

Humans have two populations of innate-like T lymphocytes with an invariant T cell antigen receptor (TCR) a chain: invariant natural killer T (iNKT) cells and mucosal associated invariant T (MAIT) cells. iNKT cell involvement in human asthma has been suggested, but is controversial, while there has been little analysis of MAIT cells. Using peripheral blood cells from the urban environment and childhood asthma (URECA) birth cohort study, we carried out a comprehensive investigation to determine if iNKT cell frequency or MAIT cell frequency early in life is correlated with the cytokine polarization of mainstream CD4+T cells and/or the development of asthma by age seven. We also determined if iNKT cell antigenic activity in house dust samples was associated with environmental endotoxin or clinical outcomes including aeroallergen sensitization and recurrent wheeze at 3 and asthma at age 7. We also analyzed the correlation between cytokines released by activated iNKT and MAIT cells and various clinical outcomes. Our results shows that the frequency of MAIT cells was associated with increased production of IFNg by activated CD4+ T cells from children that did not go on to develop asthma. Moreover, an increased MAIT cell frequency early in life was associated with a decreased risk of asthma by age seven. In contrast, iNKT cell frequency early in life was not correlated with the development of asthma or allergic sensitization. iNKT cell antigen content in house dust varied greatly, and increased antigen was associated not only with endotoxin levels in the surroundings but also with protection from asthma. Together, these data suggest that MAIT cell frequency and iNKT cell antigen content at one year correlates with protection from asthma development.

Long-term pulmonary complications in perinatally HIV-infected youth

BACKGROUND

Increased incidence and prevalence of asthma have been documented for perinatally HIV-infected youth 10 to 21 years of age compared with HIV-exposed uninfected (HEU) youth.

OBJECTIVE

We sought to perform objective pulmonary function tests (PFTs) in HIV-infected and HEU youth with and without diagnosed asthma.

METHOD

Asthma was determined in 370 participants (218 HIV-infected and 152 HEU participants) by means of chart review and self-report at 13 sites. Interpretable PFTs (188 HIV-infected and 132 HEU participants) were classified as obstructive, restrictive, or normal, and reversibility was determined after bronchodilator inhalation. Values for HIV-1 RNA, CD4 and CD8 T cells, eosinophils, total IgE, allergen-specific IgE, and urinary cotinine were measured. Adjusted prevalence ratios (PRs) of asthma and PFT outcomes were determined for HIV-infected participants relative to HEU participants, controlling for age, race/ethnicity, and sex.

RESULTS

Current asthma was identified in 75 (34%) of 218 HIV-infected participants and 38 (25%) of 152 HEU participants (adjusted PR, 1.33; P = .11). The prevalence of obstructive disease did not differ by HIV status. Reversibility was less likely in HIV-infected youth than in HEU youth (17/183 [9%] vs 21/126 [17%]; adjusted PR, 0.47; P = .020) overall and among just those with obstructive PFT results (adjusted PR, 0.46; P = .016). Among HIV-infected youth with current asthma, serum IgE levels were inversely correlated with CD8 T-cell counts and positively correlated with eosinophil counts and not associated with CD4 T-cell counts. HIV-infected youth had lower association of specific IgE levels to several inhalant and food allergens compared with HEU participants and significantly lower CD4/CD8 T-cell ratios (suggesting immune imbalance).

CONCLUSION

Compared with HEU youth, HIV-infected youth demonstrated decreased reversibility of obstructive lung disease, which is atypical of asthma. This might indicate an early stage of chronic obstructive pulmonary disease. Follow-up into adulthood is warranted to further define their pulmonary outcomes.

Relationships among Maternal Stress and Depression, Type 2 Responses, and Recurrent Wheezing at Age 3 Years in Low-Income Urban Families

RATIONALE

Maternal depression and prenatal and early life stress may influence childhood wheezing illnesses, potentially through effects on immune development.

OBJECTIVES

To test the hypothesis that maternal stress and/or depression during pregnancy and early life are associated with recurrent wheezing and aeroallergen sensitivity and altered cytokine responses (enhanced type 2 or reduced virus-induced cytokine responses) from stimulated peripheral blood mononuclear cells at age 3 years.

METHODS

URECA (Urban Environment and Childhood Asthma) is a birth cohort at high risk for asthma (n = 560) in four inner cities. Maternal stress, depression, and childhood wheezing episodes were assessed by quarterly questionnaires beginning at birth. Logistic and linear regression techniques were used to examine the relation of maternal stress/depression to recurrent wheezing and peripheral blood mononuclear cell cytokine responses at age 3 years.

MEASUREMENTS AND MAIN RESULTS

Overall, 166 (36%) children had recurrent wheeze at age 3 years. Measures of maternal perceived stress at Years 2 and 3 were positively associated with recurrent wheeze (P < 0.05). Maternal depression (any year) was significantly associated with recurrent wheezing (P ≤ 0.01). These associations were also significant when considered in a longitudinal analysis of cumulative stress and depression (P ≤ 0.02). Neither stress nor depression was significantly related to aeroallergen sensitization or antiviral responses. Contrary to our original hypothesis, prenatal and Year 1 stress and depression had significant inverse associations with several type 2 cytokine responses.

CONCLUSIONS

In urban children at high risk for asthma, maternal perceived stress and depression were significantly associated with recurrent wheezing but not increased atopy or reduced antiviral responses.