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.

Genetic approach identifies distinct asthma pathways in overweight vs normal weight children.

The pathogenesis of asthma in the context of excess body weight may be distinct from asthma that develops in normal weight children. The study's objective was to explore the biology of asthma in the context of obesity and normal weight status using genetic methodologies. Associations between asthma and SNPs in 49 genes were assessed, as well as, interactions between SNPs and overweight status in child participants of the Greater Cincinnati Pediatric Clinic Repository. Asthma was significantly associated with weight (OR = 1.38; P = 0.037). The number of genes and the magnitude of their associations with asthma were notably greater when considering overweight children alone vs normal weight and overweight children together. When considering weight, distinct sets of asthma-associated genes were observed, many times with opposing effects. We demonstrated that the underlying heterogeneity of asthma is likely due in part to distinct pathogenetic pathways that depend on preceding/comorbid overweight and/or allergy. It is therefore important to consider both obesity and asthma when conducting studies of asthma.

N-acetyltransferase 1 polymorphism increases cotinine levels in Caucasian children exposed to secondhand smoke: the CCAAPS birth cohort.

Cotinine is a proxy for secondhand smoke (SHS) exposure. Genetic variation along nicotine and cotinine metabolic pathways may alter the internal cotinine dose, leading to misinterpretations of exposure-health outcome associations. Caucasian children with available SHS exposure and hair cotinine data were genotyped for metabolism-related genes. SHS-exposed children had 2.4-fold higher hair cotinine (0.14±0.22 ng mg(-1)) than unexposed children (0.06±0.05 ng mg(-1), P<0.001). SHS-exposed children carrying the NAT1 minor allele had twofold higher hair cotinine (0.18 ng mg(-1) for heterozygotes and 0.17 ng mg(-1) for homozygotes) compared with major allele homozygotes (0.09 ng mg(-1), P=0.0009), even after adjustment for SHS dose. These findings support that NAT1 has a role in the metabolic pathway of nicotine/cotinine and/or their metabolites. The increased cotinine levels observed for those carrying the minor allele may lead to SHS exposure misclassification in studies utilizing cotinine as a biomarker. Additional studies are required to identify functional single-nucleotide polymorphism(s) (SNP(s)) in NAT1 and elucidate the biological consequences of the mutation(s).

Duration of day care attendance during infancy predicts asthma at the age of seven: the Cincinnati Childhood Allergy and Air Pollution Study.

BACKGROUND: Studies vary with respect to the reported effects of day care attendance on childhood asthma. OBJECTIVES: To evaluate the independent and combined effects of day care attendance and respiratory infections on the development of asthma at the age of seven in a prospective birth cohort. METHOD: At the age of seven, the study sample included 589 children with complete data of 762 enrolled at birth. Day care hours and number of respiratory infections were reported in follow-up questionnaires through age four. At 7 years of age, asthma was diagnosed in 95 children (16%), based on predefined symptoms criteria confirmed by either asthma FEV1 reversibility after bronchodilator or a positive methacholine test (PC20 ≤ 4 mg/mL). Logistic regression was used to investigate the relationships between asthma at the age of seven, cumulative hours of day care attendance and reported respiratory infections at ages 1-4. RESULTS: In the univariate analyses, day care attendance at 12 months was associated with an increased risk of asthma [odds ratio (OR) = 1.8, 95% confidence interval (CI) = 1.1-3.0]. Both upper and lower respiratory infections at 12 months also increased the likelihood of asthma [OR = 2.4 (1.4-4.1); OR = 2.3 (1.5-3.7), respectively]. In the final multivariate logistic model, cumulative hours of day care attendance and number of lower respiratory infections at 12 months were associated with asthma [OR = 1.2 (1.1-1.5); OR = 1.4 (1.2-1.7), respectively]. However, a threshold of greater than 37.5 hours per week of day care attendance was associated with a lower risk of asthma [OR = 0.6 (0.4-0.9)]. CONCLUSION: Depending on duration of attendance, day care during infancy can either increase or reduce risk of asthma at the age of seven.

Diesel exhaust particle exposure increases severity of allergic asthma in young mice.

BACKGROUND: Epidemiologic studies have reported an association between diesel exhaust particle (DEP) exposure, allergic sensitization, and childhood wheezing, although the mechanisms remain unclear. While DEP is known to augment allergic responses in adult animal models, its effects on sensitization and asthma severity in young animals is unknown. OBJECTIVE: To examine the impact of different doses of DEP and allergen co-exposure on allergic sensitization and asthma characteristics in young mice, and whether Th17 as well as Th2 responses are induced. METHODS: Lungs of 3-week-old wild-type Balb/c mice were exposed by pharyngeal aspiration nine times over 3 weeks to DEP at 1.2 or 6.0 mg/kg body weight, house dust mite (HDM) at 0.8, 1.2 or 6.0 mg/kg of DEP in combination with HDM, or the same volume (50 µL) of 0.9% sterile saline. RESULTS: In young mice, exposure to 1.2 mg/kg of DEP caused no detectable lung inflammation, but 6.0 mg/kg of DEP induced neutrophilic influx. Compared to HDM or DEP alone, mice exposed to either dose of DEP together with HDM demonstrated increased allergen-specific IgE, lung inflammation, airway hyperreactivity, goblet cell metaplasia, Th2/Th17 cytokines, dendritic cells, activated T cells, effector T cells, and IL-17(pos) and IL-13(pos) /IL-17A(pos) T effector cells. CONCLUSIONS AND CLINICAL RELEVANCE: In young mice, co-exposure to DEP and HDM together exacerbated allergic sensitization and induced key characteristics of more severe asthma, including IL-17A, IL-17(pos) and IL-13(pos) /IL-17A(pos) T effector cells. While exposure to 1.2 mg/kg DEP alone caused no detectable changes, it did exacerbate allergic sensitization and asthma characteristics to a similar degree as a five-fold higher dose of DEP. This study demonstrates that exposure to DEP, even at a dose that alone causes no inflammation, exacerbates allergic asthma in young animals and suggests the importance of preventive measures to reduce the exposure of children to traffic related air pollution.

Analysis of the Ser786Pro interleukin-4 receptor alpha allelic variant in allergic and nonallergic asthma and its functional consequences.

Asthma and other atopic disorders affect a large percentage of the population. While many factors contribute to the phenotype of asthma, there is a strong genetic predisposition. IL-4 is a central mediator of allergic inflammation. Along with IL-13, it is the major cytokine responsible for the induction of IgE synthesis. Furthermore, IL-4 acts on Th0 cells and promotes their differentiation into Th2 cells resulting in the production of more IL-4 and IL-13, thereby propagating the allergic cascade. Both IL-4 and IL-13 utilize IL-4Ralpha as a component of their cognate receptor complexes. Eight polymorphisms of the IL-4Ralpha gene resulting in amino acid changes in the coding sequence have been described, and several have been associated with asthma. The central objective of this study was to elucidate the role of the Ser786Pro polymorphism in asthma and its impact on IL-4R function. One-hundred ninety-six individuals with asthma and 53 controls were genotyped for Pro786. Pro786 occurred infrequently in the general population with an allele frequency of 1.8% and, thus, is unlikely to play a major role in atopy or asthma. The Pro786 allele frequency was 1.5% in the asthma group and 2.8% in the control group. The asthma group was subdivided into allergic and nonallergic asthma, and the Pro786 allele frequencies were 1.7 and 1.0%, respectively. The data suggested linkage disequilibrium between Ser786Pro and the Gln576Arg allele, which is associated with atopy. In order to study the impact of the polymorphism on receptor signaling function, we transfected a mouse B lymphoma cell line with the wild-type and Pro786 variants of human IL-4Ralpha. The Ser786Pro polymorphism in isolation did not affect IL-4R function.

The R576 IL-4 receptor alpha allele correlates with asthma severity.

BACKGROUND: Atopic disorders, including asthma, are very prevalent, affecting up to 40% of populations, and their incidence is on the rise. Although environmental factors are important in the development of atopy, there is a strong genetic predisposition. Several genes and chromosomal regions have been linked to atopy and asthma, supporting the polygenic nature of these disorders. IL-4 and IL-13 are T(H)2 cytokines with numerous activities that contribute to allergic inflammation and asthma. Both IL-4 and IL-13 use the IL-4 receptor alpha chain (IL-4Ralpha) as a component of their respective receptor systems. Allelic variants of IL-4Ralpha have been reported, and the R576IL-4Ralpha allele was recently shown to be a risk factor for atopy. OBJECTIVE: We sought to determine whether the R576 allele was associated with the prevalence or clinical severity of asthma. METHODS: We developed a rapid, reliable, PCR-based assay to screen individuals for the R576IL-4Ralpha allele and used this assay to genotype prospectively recruited individuals with asthma (n = 149) and control subjects (n = 57). RESULTS: There was a strong association of R576IL-4Ralpha with the prevalence and clinical severity of asthma. In a prospective cohort, homozygosity for R576 was significantly increased in individuals with asthma (n = 149, P =.03; relative risk 8.2) compared with controls (n = 57). Furthermore, 1 or 2 copies R576IL-4Ralpha correlated with asthma severity establishing a genotype-phenotype relationship and suggesting a gene dosage effect. CONCLUSIONS: Thus R576IL-4Ralpha acts as an allergic asthma susceptibility and disease-modifying gene and may serve as a clinically useful marker of asthma severity.