On early sensitization to allergens and development of respiratory symptoms

Single and multiple time-point allergic sensitization during childhood and risk of asthma by age 13

BACKGROUND

The relationship between allergic sensitization during childhood and risk of developing asthma remains unclear.

OBJECTIVE

To analyze single time-point and temporal patterns of sensitization in childhood in relation to asthma at age 13.

METHODS

Specific IgE (sIgE) level and skin prick test (SPT) toward 22 food allergens and aeroallergens were assessed at 6, 18 months, 4, 6, and 13 years in children from the high-risk Copenhagen Prospective Studies on Asthma in Childhood₂₀₀₀ (COPSAC₂₀₀₀ ) mother-child cohort. We analyzed the association between single time-point monosensitization, polysensitization, and quantitative assessment of sensitization, that is, sum of all sIgE levels and SPT wheal sizes, against asthma at age 13. In addition, we analyzed the association between three temporal patterns of sensitization: (a) early-transient, (b) late-onset, and (c) persistent sensitization and asthma.

RESULTS

Polysensitization status measured by SPT or sIgE was at all single time-points associated with increased risk of asthma at age 13: OR range, SPT = 3.0-15.7, and sIgE = 2.6-15.7, respectively, whereas monosensitization status was inconsistently associated with asthma. Quantitative assessment of both sIgE and SPT results was associated with asthma at all single time-points: OR range, SPT = 1.3-3.6, and sIgE = 1.1-1.7. Persistent sensitization, but not early-transient or late-onset sensitization was associated with asthma by age 13: OR [95% CI], SPT = 8.9 [2.8-28.23], and sIgE = 2.9 [1.1-7.6], respectively.

CONCLUSION

Sensitization to multiple allergens at single time-points, increasing sIgE levels and SPT wheal sizes, and persistent sensitization during childhood were associated with increased risk of asthma at age 13, suggesting the use of quantitative and repetitive sensitization measurements when assessing risk of developing asthma.

Chronological changes in rhinitis symptoms present in school-aged children with allergic sensitization

Introduction

It is difficult to accurately predict the natural course of allergic rhinitis (AR), because it is affected by a wide variety of environmental influences, as well as genetic predisposition. Considering the high prevalence of allergic rhinitis in children and adolescents, caregivers should be given appropriate information regarding the disease course. This study aimed to understand the prognosis of allergic rhinitis by examining the relationship between allergic sensitization and rhinitis symptoms during this developmental period.

Methods

This cross-sectional study included 1069 children aged 9–16 years from the Korean International Study of Asthma and Allergies in Childhood Survey database who had completed health questionnaires, and for whom skin prick test results were available. Data were collected during May 2016. The distribution of sensitization and allergic symptoms was compared by age groups (elementary, middle, and high school). Data were analyzed using linear-by-linear analysis.

Results

Sensitization to at least one tested allergen differed by age (59.2%, 58.3%, 68.2%, in elementary, middle, and high school students, respectively; p = 0.025), and seasonal allergen sensitization (35.0%, 37.1%, 53.9%, respectively) increased with age (p < 0.001). Conversely, the proportion of rhinitis symptoms among sensitized children decreased as age increased (58.80%, 52.90%, 49.70%, respectively; p = 0.047). However, the rate of non-allergic rhinitis was age-independent.

Conclusion

With increasing age during childhood and adolescence, symptomatic allergic rhinitis decreases; thus, subclinical allergic rhinitis increases. This suggests that the symptoms of later-sensitized children are less clearly manifested, or that the symptoms reduce as previously sensitized children mature. This should be clarified further in a longitudinal study.

Sensitization to secretoglobin and lipocalins in a group of young children with risk of developing respiratory allergy

BACKGROUND

Multiple sensitizations in early age have been reported to be a risk for development of asthma. This study evaluates the emergence and evolution of IgE to aeroallergens among a cohort of children with physician-diagnosed atopic dermatitis and/or showing food allergy symptoms and to examine the relation to asthma development.

METHODS

Three-hundred and four children (median age 13.4 months at entry) with food allergy symptoms and/or atopic dermatitis without asthma at inclusion were analysed for IgE antibodies against food-, indoor- and outdoor-allergens and pet allergen components and correlated to the individuals' outcome on asthma inception.

RESULTS

At 2 years of follow-up, physician-diagnosed asthma was 19.7% (n = 49) and asthma diagnosed any time was 24% (n = 67). History of persistent cough and asthma of father, combination of milk- and wheat-allergy symptoms and dual sensitization to house dust mite and Japanese cedar were independent risk factors for asthma. Sensitization to dog was the most prevalent inhalant allergen at entry. Asthma children had a higher proportion of sensitization to dog, cat and horse allergens at entry compared with non-asthma children. Being sensitized to both food, house dust mite and pet allergens was strongly associated with asthma (p = 0.0006). Component resolved diagnosis for dog and cat allergens showed that IgE antibodies to Can f 1 and Fel d 1 was common even at very young age.

CONCLUSIONS

Early sensitization to inhalant allergens increases the risk of developing asthma as well as having milk and wheat allergy symptoms. Sensitization to dog, was common at an early age despite dog ownership. Sensitization to secretoglobin and lipocalins and less to serum albumins explained the pet sensitization.

Latent class analysis reveals clinically relevant atopy phenotypes in 2 birth cohorts

BACKGROUND

Phenotypes of childhood-onset asthma are characterized by distinct trajectories and functional features. For atopy, definition of phenotypes during childhood is less clear.

OBJECTIVE

We sought to define phenotypes of atopic sensitization over the first 6 years of life using a latent class analysis (LCA) integrating 3 dimensions of atopy: allergen specificity, time course, and levels of specific IgE (sIgE).

METHODS

Phenotypes were defined by means of LCA in 680 children of the Multizentrische Allergiestudie (MAS) and 766 children of the Protection against allergy: Study in Rural Environments (PASTURE) birth cohorts and compared with classical nondisjunctive definitions of seasonal, perennial, and food sensitization with respect to atopic diseases and lung function. Cytokine levels were measured in the PASTURE cohort.

RESULTS

The LCA classified predominantly by type and multiplicity of sensitization (food vs inhalant), allergen combinations, and sIgE levels. Latent classes were related to atopic disease manifestations with higher sensitivity and specificity than the classical definitions. LCA detected consistently in both cohorts a distinct group of children with severe atopy characterized by high seasonal sIgE levels and a strong propensity for asthma; hay fever; eczema; and impaired lung function, also in children without an established asthma diagnosis. Severe atopy was associated with an increased IL-5/IFN-γ ratio. A path analysis among sensitized children revealed that among all features of severe atopy, only excessive sIgE production early in life affected asthma risk.

CONCLUSIONS

LCA revealed a set of benign, symptomatic, and severe atopy phenotypes. The severe phenotype emerged as a latent condition with signs of a dysbalanced immune response. It determined high asthma risk through excessive sIgE production and directly affected impaired lung function.

Clinical phenotype and allergen sensitization in the first 2 years as predictors of atopic disorders at age 5 years

Introduction

From a birth cohort of at-risk Asian infants, we prospectively investigated the role of early onset allergen sensitization and clinical phenotypes as risk factors for atopic disorders at the age of 5 years.

Methods and materials

The study recruited 253 families with a history of allergic disease in a first degree relative from an antenatal clinic in Singapore. The children were followed prospectively to assess clinical outcomes and skin prick test was performed at 2 and 5 years of age.

Results

Allergen sensitization (food and/or house dust mites) alone at 2 years of age was not associated with increased risk of wheeze and eczema at 5 years. However, the clinical phenotype (eczema and wheeze) with or without the presence of concomitant allergen sensitization at 2 years increased this risk. For eczema, eczema alone at year 2 increased the risk of eczema at year 5 (adjOR = 7.1; 95 % CI: 1.8–27.8) and this was further increased by the presence of allergen sensitization (adjOR = 25.4; 95 % CI: 4.7–138.5) and the concomitant presence of both wheeze and allergen sensitization (adjOR = 64.9; 95 % CI: 4.7–900.0). For wheeze, wheeze alone at 2 years (adjOR = 4.5; 95 % CI: 1.4 -14.8), and wheeze with concomitant allergen sensitization and eczema (adjOR = 13.9; 95 % CI: 1.2–168.5) increased the risk of wheeze at 5 years. The exception was rhinitis, where allergen sensitization alone at 2 years (adjOR = 5.6; 95 % CI: 1.1–29.2) increased the risk of rhinitis at 5 years. Early onset of eczema at 2 years also increased the risk of rhinitis (adjOR = 6.8; 95 % CI: 2.0–23.1).

Conclusion

In this Asian birth cohort, the clinical phenotype (eczema and wheeze) with or without concomitant allergen sensitization in the first 2 years of life were strong predictors of atopic disorders at 5 years.

Reprint of: Perinatal and early childhood environmental factors influencing allergic asthma immunopathogenesis

BACKGROUND

The prevalence of asthma has increased dramatically over the past several decades. While hereditary factors are highly important, the rapid rise outstrips the pace of genomic variation. Great emphasis has been placed on potential modifiable early life exposures leading to childhood asthma.

METHODS

We reviewed the recent medical literature for important studies discussing the role of the perinatal and early childhood exposures and the inception of childhood asthma.

RESULTS AND DISCUSSION

Early life exposure to allergens (house dust mite (HDM), furred pets, cockroach, rodent and mold), air pollution (nitrogen dioxide (NO2), ozone (O3), volatile organic compounds (VOCs), and particulate matter (PM)) and viral respiratory tract infections (Respiratory syncytial virus (RSV) and human rhinovirus (hRV)) has been implicated in the development of asthma in high risk children. Conversely, exposure to microbial diversity in the perinatal period may diminish the development of atopy and asthma symptoms.

Elucidation of pathways driving asthma pathogenesis: development of a systems-level analytic strategy

Asthma is a genetically complex, chronic lung disease defined clinically as episodic airflow limitation and breathlessness that is at least partially reversible, either spontaneously or in response to therapy. Whereas asthma was rare in the late 1800s and early 1900s, the marked increase in its incidence and prevalence since the 1960s points to substantial gene × environment interactions occurring over a period of years, but these interactions are very poorly understood (1-6). It is widely believed that the majority of asthma begins during childhood and manifests first as intermittent wheeze. However, wheeze is also very common in infancy and only a subset of wheezy children progress to persistent asthma for reasons that are largely obscure. Here, we review the current literature regarding causal pathways leading to early asthma development and chronicity. Given the complex interactions of many risk factors over time eventually leading to apparently multiple asthma phenotypes, we suggest that deeply phenotyped cohort studies combined with sophisticated network models will be required to derive the next generation of biological and clinical insights in asthma pathogenesis.

Airway wall remodeling in young and adult rats with experimentally provoked bronchial asthma

BACKGROUND

Airway wall remodeling is a typical finding in patients suffering from bronchial asthma. While morphological changes have been thoroughly described in adults, less is known about such changes in children because of the limited accessibility of relevant material. To overcome this constraint, animal asthma models may be used instead of human specimens. This study examined rats with artificially stimulated chronic asthma-like symptoms.

METHODS

Brown Norway rats of two age categories (young and adult) were sensitized by ovalbumin (OA), and their intrapulmonary airways (IA) were studied using morphometric and histochemical methods.

RESULTS

OA administration induced a significant increase in lung resistance in young animals but not in adults. The total IA wall area was significantly increased in both young and adult OA rats. In young animals, thickening of the adventitia played a more crucial role in this increase than it did in adults, in which the mucosa and the submucosa participated to a higher degree. The IA walls of young OA rats had significantly higher levels of infiltrating eosinophils than those of adult OA animals. The multiplication of goblet cells was more pronounced in adult rats, which was associated with a tendency to produce a higher proportion of acidic glycoconjugates.

CONCLUSIONS

OA stimulation affected the IA of young rats differently than those of adult animals. Changes in the outer IA layer of young rats can be triggered by activated eosinophils; however, stimulated airway epithelium can be a source of factors that influence the inner IA layers in adult rats.

Rhinovirus and the developing lung

Human rhinovirus (HRV) infections are now widely accepted as the commonest cause of acute respiratory illnesses (ARIs) in children. Advanced PCR techniques have enabled HRV infections to be identified as causative agents in most common ARIs in childhood including bronchiolitis, acute asthma, pneumonia and croup. However, the long-term implications of rhinovirus infections are less clear. The aim of this review is to examine the relationship between rhinovirus infections and disorders of the lower airways in childhood.

Exclusive breastfeeding is associated with reduced cow's milk sensitization in early childhood

BACKGROUND

Although breastfed infants have consistently been reported as having fewer infections and respiratory morbidity during infancy, none have reached a definitive conclusion as to whether breastfeeding is an effective strategy to prevent allergic diseases. This study aims to investigate the relationship between exclusive breastfeeding and sequential changes of several biomarkers of allergy, such as absolute eosinophil count, total IgE level, and specific IgE level during the first 3 yrs of life.

METHODS

This is an unselected, population-based study that is part of a prospective birth cohort called the PATCH (Prediction of Allergy in Taiwanese Children). Blood analysis was performed at ages 6, 12, 18, 24, and 36 months. Clinical records of breastfeeding and detailed questionnaires regarding to allergic diseases were also obtained.

RESULTS

Analysis comparing exclusive breastfeeding ≥4 months with those <4 months and those partially breastfed showed a decreased risk of sensitization toward cow's milk protein up to the age of 2 yr (adjusted OR for cow's milk sensitization at 12 months was 0.2 [95% CI, 0.07-0.5]), at 18 months of age it was 0.2 [95% CI, 0.07-0.5], and at 24 months of age it was 0.2 [95% CI, 0.04-0.7]). In addition, although not significant, children of the exclusive breastfeeding group showed a trend of lower absolute eosinophil counts than their counterparts at all ages, and a lower total IgE level at the age of 3 yr.

CONCLUSIONS

Results of this study suggest that exclusive breastfeeding is associated with a reduced risk of cow's milk protein sensitization during early childhood.

Perinatal and early childhood environmental factors influencing allergic asthma immunopathogenesis

BACKGROUND

The prevalence of asthma has increased dramatically over the past several decades. While hereditary factors are highly important, the rapid rise outstrips the pace of genomic variation. Great emphasis has been placed on potential modifiable early life exposures leading to childhood asthma.

METHODS

We reviewed the recent medical literature for important studies discussing the role of the perinatal and early childhood exposures and the inception of childhood asthma.

RESULTS AND DISCUSSION

Early life exposure to allergens (house dust mite (HDM), furred pets, cockroach, rodent and mold), air pollution (nitrogen dioxide (NO(2)), ozone (O(3)), volatile organic compounds (VOCs), and particulate matter (PM)) and viral respiratory tract infections (Respiratory syncytial virus (RSV) and human rhinovirus (hRV)) has been implicated in the development of asthma in high risk children. Conversely, exposure to microbial diversity in the perinatal period may diminish the development of atopy and asthma symptoms.

Defective respiratory tract immune surveillance in asthma: a primary causal factor in disease onset and progression

The relative importance of respiratory viral infections vs inhalant allergy in asthma pathogenesis is the subject of ongoing debate. Emerging data from long-term prospective birth cohorts are bringing increasing clarity to this issue, in particular through the demonstration that while both of these factors can contribute independently to asthma initiation and progression, their effects are strongest when they act in synergy to drive cycles of episodic airways inflammation. An important question is whether susceptibility to infection and allergic sensitization in children with asthma arises from common or shared defect(s). We argue here that susceptibility to recurrent respiratory viral infections, failure to generate protective immunologic tolerance to aeroallergens, and ultimately the synergistic interactions between inflammatory pathways triggered by concomitant responses to these agents all result primarily from functional deficiencies within the cells responsible for local surveillance for antigens impinging on airway surfaces: the respiratory mucosal dendritic cell (DC) network. The effects of these defects in DCs from children wtih asthma are accentuated by parallel attenuation of innate immune functions in adjacent airway epithelial cells that reduce their resistance to the upper respiratory viral infections, which are the harbingers of subsequent inflammatory events at asthma lesion site(s) in the lower airways. An important common factor underpinning the innate immune functions of these unrelated cell types is use of an overlapping series of pattern recognition receptors (exemplified by the Toll-like receptor family), and variations in the highly polymorphic genes encoding these receptors and related molecules in downstream signaling pathways appear likely contributors to these shared defects. Findings implicating recurrent respiratory infections in adult-onset asthma, much of which is nonatopic, suggest a similar role for deficient immune surveillance in this phenotype of the disease.

Epidemiology of virus-induced wheezing/asthma in children

Wheezing is a lower respiratory tract symptom induced by various viral respiratory infections. Epidemiological studies have revealed the phenotypes of wheezing in early childhood which have different risk factors for the development of asthma among school age children. The major viral species causing wheezing in children include respiratory syncytial virus, rhinovirus, human metapneumovirus and influenza viruses. It has been shown that the impact on the development of asthma is different between those virus species. Moreover, recent studies have also focused on the interaction between virus infection and other risk factors in the development of asthma, such as genetic factors or allergic sensitization. In this review, we summarize the previous findings and discuss how clinicians can effectively intervene in these viral infections to prevent the development of asthma.

The pharmacological modulation of allergen-induced asthma

Aeroallergens are the most common triggers for the development of asthma. Recent birth cohort studies have identified viral infections occurring against a background of aeroallergen sensitization as a potent risk factor for initiation of asthma. Viral infection enhances immunopathogenic potential of pre-existing inhalant allergy via modulating airway mucosal dendritic cells. By using an allergen inhalation challenge clinical model, studies have shown that the late asthma response (LAR) is associated with more pronounced allergen-induced airway inflammation and airway hyperresponsiveness. The degree of airway eosinophilia, regulated by bone marrow progenitor cells and interleukin-5 level, correlates with the magnitude of the LAR and the increase in hyperresponsiveness. Both myeloid and plasmacytoid dendritic cell subsets have been involved in the pathogenesis of allergen-induced LAR. Myeloid dendritic cells are responsible for the allergen presentation and induction of inflammation and plasmacytoid dendritic cells play a role in the resolution of allergen-induced inflammation. A variety of potential new classes of asthma medication has also been evaluated with the allergen inhalation challenge in mild asthmatic subjects. Examples are TPI ASM8, an inhaled anti-sense oligonucleotide drug product, which attenuated both early and LARs via inhibition of the target gene mRNA of chemokine receptor 3, and the common β chain of interleukin-3, interleukin-5 and granulocyte-macrophage colony-stimulating factor receptor. Anti-human antibody interleukin-13 (IM-638) significantly attenuated both early and late allergen-induced asthma response. Pitrakinra, which targets both interleukin-4 and interleukin-13, substantially diminishes allergen-induced airway responses. Allergen-induced airway responses are a valuable way to evaluate the activity of possible new therapies in asthmatic airways.

Overview of serological-specific IgE antibody testing in children

Allergic diseases are among the most common chronic conditions in the pediatric population. Allergy diagnostic testing is an important part of the evaluation/management of allergic patients because the history may not be precise enough to identify the specific allergen sensitivity. In addition to providing information about specific sensitivities, allergy diagnostic tests have some predictive value in terms of future risk of developing an allergic condition and the severity/persistence of the allergic disease. The two most commonly used methods of confirming allergen sensitization are skin testing and measurement of serum-specific IgE. Both methods have similar diagnostic value in terms of sensitivity and specificity, with both parameters varying with the clinical scenario and allergen tested. Currently, there are three US Food and Drug Administration-cleared, serum-specific IgE assays used in the United States. The three assays report comparable analytic sensitivity, with the coefficients of variation of the precision, reproducibility, and linearity being less than 15%. However, comparative studies have demonstrated significant inter-assay variability, suggesting that they detect different populations of IgE antibody in human sera or do not measure the same antibodies with the same efficiency. Current specific IgE assays utilize allergen extract reagents. Testing with these reagents may identify sensitivity to clinically irrelevant allergens. This diagnostic limitation has spurred the development of molecular diagnostic tests, also referred to as component-resolved diagnostics, which utilize purified native or recombinant allergens to detect IgE sensitivity to individual allergen molecules. These advancements in serum IgE testing may enhance the precision of allergy diagnostic testing, which may decrease the need for oral food challenges and improve the specificity of allergen immunotherapy.

Familial aggregation of allergen-specific sensitization and asthma

BACKGROUND

Familial aggregation of specific response to allergens and asthma adjusted for age and sensitization to multiple allergens was assessed in two large population cohorts.

METHODS

Allergen skin prick tests (SPTs) were administered to 1151 families in the Tucson Children's Respiratory Study (CRS) and 435 families in the Tucson Epidemiological Study of Airway Obstructive Disease (TESAOD). Sensitization was defined by wheal size ≥3 mm; physician-diagnosed asthma at age ≥8 yr was based on questionnaires. Using S.A.G.E. 6.1 software ASSOC and FCOR, familial correlations of crude and adjusted phenotypes were evaluated.

RESULTS

Crude estimates of parent-offspring (P-O) and sibling correlations were statistically significant for most allergens, ranging from 0.03 to 0.29. After adjusting for age of assessment and 'other atopy' (SPT-positive response to additional allergens), correlations were reduced by 14-71%. Sibling correlations for specific response to allergens were consistently higher than P-O correlations, but this difference was significant only for dust mite and weed mix in the TESAOD population. Familial correlation for atopic status (any positive SPTs vs. none) tended to be higher than for specific allergens. Asthma, with and without adjustment, showed greater familial correlation than either specific or general SPT response and significantly higher sibling correlation in TESAOD than in CRS, probably due to the older age of the siblings and the longer period of ascertainment.

CONCLUSIONS

Significant familial aggregation of specific response to allergen after adjustment for other atopy appears to reflect a genetic propensity toward atopy, dependent on shared familial exposures. Results also suggest that inheritance of asthma is independent of atopic sensitization.

Interaction between adaptive and innate immune pathways in the pathogenesis of atopic asthma: operation of a lung/bone marrow axis

Atopic asthma is the most common form of asthma, particularly during childhood, and in many cases it persists into adult life. Although atopy is clearly a risk factor for development of this disease, only a small subset of subjects sensitized to aeroallergens express persistent symptoms, suggesting that additional pathogenic mechanisms are involved. Recent studies have implicated respiratory viral infections as key cofactors in asthma development in atopic patients. In relation to initial expression of the asthma phenotype in early childhood, it has been shown that although both atopic sensitization and early severe lower respiratory tract infections can operate as independent asthma risk factors, the persistence of asthma is most frequent among children who experience both insults, suggesting that the relevant inflammatory pathways interact to maximally drive disease pathogenesis. Importantly, it has been established that both these factors must be operative contemporaneously for these interactions to occur (ie, the interactions are likely to be direct). Recent studies on viral-induced asthma exacerbations in atopic children have provided a plausible mechanism for these interactions. Notably, it has been demonstrated that signals triggered during the innate immune response to the virus can lead to the release of large numbers of migrating high-affinity IgE receptor-bearing bone marrow-derived precursors of mucosal dendritic cells into the blood. The subsequent trafficking of these cells to the infected airway mucosa where dendritic cell turnover is very high provides a potential mechanism for recruitment of underlying aeroallergen-specific T-helper 2 immunity into the already inflamed milieu in the infected airway mucosa.

Bacterial infections and pediatric asthma

Streptococcus pneumoniae, Haemophilus influenzae and Moraxella catarrhalis seem to have no role in asthma in children. Mycoplasma pneumoniae and Chlamydophila pneumoniae can induce wheezing and cause asthma exacerbations in children, and chronic Chlamydophila infections may even participate in asthma pathogenesis. However, studies have failed to show any benefits from antibiotics for incipient or stable pediatric asthma, as well as for asthma exacerbations in children. Exposure to antibiotics in infancy has been an independent risk factor of later asthma in many studies. A recent study applying molecular biology methods to lower airway samples provided preliminary evidence that lower airways are not sterile but have their own protective microbiota, which can be disturbed in lung diseases like asthma.

Evaluation of airway reactivity and immune characteristics as risk factors for wheezing early in life

BACKGROUND

Childhood asthma is most often characterized by recurrent wheezing, airway hyperreactivity, and atopy; however, our understanding of these relationships from early in life remains unclear. Respiratory tract illnesses and atopic sensitization early in life might produce an interaction between innate and acquired immune responses, leading to airway inflammation and heightened airway reactivity.

OBJECTIVE

We hypothesized that premorbid airway reactivity and immunologic characteristics of infants without prior episodes of wheezing would be associated with subsequent wheezing during a 1-year follow-up.

METHODS

One hundred sixteen infants with chronic dermatitis were enrolled before episodes of wheezing. Airway reactivity, allergen-specific IgE levels, cytokine production by stimulated PBMCs, and percentages of dendritic cells were measured on entry, and airway reactivity was reassessed at the 1-year follow-up. Linear regression models were used to evaluate a predictor's effect on continuous outcomes.

RESULTS

Milk sensitization, egg sensitization, or both were associated with heightened airway reactivity before wheezing and after the onset of wheezing; however, these factors were not associated with an increased risk of wheezing. There was an interaction between initial airway reactivity and wheezing as a determinant of airway reactivity at follow-up. In addition, cytokine production by stimulated PBMCs was a risk factor for wheezing, whereas increased percentages of conventional dendritic cells were protective against wheezing.

CONCLUSION

Our data in a selected cohort of infants support a model with multiple risk factors for subsequent wheezing that are independent of initial airway reactivity; however, the causative factors that produce wheezing very early in life might contribute to heightened airway reactivity.

Toward improved prediction of risk for atopy and asthma among preschoolers: a prospective cohort study

BACKGROUND

Atopy and asthma are commonly initiated during early life, and there is increasing interest in the development of preventive treatments for at-risk children. However, effective methods for assessing the level of risk in individual children are lacking.

OBJECTIVE

We sought to identify clinical and laboratory biomarkers in 2-year-olds that are predictive of the risk for persistent atopy and wheeze at age 5 years.

METHODS

We prospectively studied 198 atopic family history-positive children to age 5 years. Clinical and laboratory assessments related to asthma history and atopy status were undertaken annually; episodes of acute respiratory illness were assessed and classified throughout and graded by severity.

RESULTS

Aeroallergen-specific IgE titers cycled continuously within the low range in nonatopic subjects. Atopic subjects displayed similar cycling in infancy but eventually locked into a stable pattern of upwardly trending antibody production and T(H)2-polarized cellular immunity. The latter was associated with stable expression of IL-4 receptor in allergen-specific T(H)2 memory responses, which was absent from responses during infancy. Risk for persistent wheeze was strongly linked to early sensitization and in turn to early infection. Integration of these data by means of logistic regression revealed that attaining mite-specific IgE titers of greater than 0.20 kU/L by age 2 years was associated with a 12.7% risk of persistent wheeze, increasing progressively to an 87.2% risk with increasing numbers of severe lower respiratory tract illnesses experienced.

CONCLUSION

The risk for development of persistent wheeze in children can be quantified by means of integration of measures related to early sensitization and early infections. Follow-up studies along similar lines in larger unselected populations to refine this approach are warranted.

The effects of selected probiotic strains on the development of eczema (the PandA study)

BACKGROUND

Modification of the intestinal microbiota by administration of probiotic bacteria may be a potential approach to prevent allergic disease. We aimed to study primary prevention of allergic disease in high-risk children by pre- and postnatal supplementation of selected probiotic bacteria.

METHODS

In a double-blind, randomized, placebo-controlled trial, a mixture of probiotic bacteria selected by in-vitro experiments (Bifidobacterium bifidum, Bifidobacterium lactis, and Lactococcus lactis; Ecologic Panda) was prenatally administered to mothers of high-risk children (i.e. positive family history of allergic disease) and to their offspring for the first 12 months of life.

RESULTS

Parental-reported eczema during the first 3 months of life was significantly lower in the intervention group compared with placebo, 6/50 vs 15/52 (P = 0.035). After 3 months, the incidence of eczema was similar in both groups. Cumulative incidence of parental-reported eczema at 1 and 2 years was 23/50 (intervention) vs 31/48 (placebo) and 27 (intervention) vs 34 (placebo), respectively. The number needed to treat was 5.9 at age 3 and 12 months and 6.7 at age 2 years. The intervention group was significantly more frequently colonized with higher numbers of Lc. lactis. Furthermore, at age 3 months, in vitro production of IL-5 (146 pg/ml vs 72 pg/ml; P = 0.04) was decreased in the probiotic-group compared with the placebo-group.

CONCLUSIONS

This particular combination of probiotic bacteria shows a preventive effect on the incidence of eczema in high-risk children, which seems to be sustained during the first 2 years of life. In addition to previous studies, the preventive effect appears to be established within the first 3 months of life.

The role of indoor allergens in the development of asthma

PURPOSE OF REVIEW

Asthma prevalence has markedly increased over the past 30 years. Although atopy and exposure to environmental allergens are known to exacerbate asthma, recent literature supports a causal role of indoor allergens in disease development.

RECENT FINDINGS

High-risk birth cohorts continue to point to atopy as the main risk factor for developing asthma. Exposure to perennial allergens has also been linked to the development of asthma, though with less consistency. Intervention at the level of allergen exposure and allergic immune response is promising.

SUMMARY

The current model of atopic asthma, the predominant phenotype, incorporates genetic and environmental factors in the development of disease. Although genetic factors are less malleable, the environmental component lends itself to analysis and modification.For many, the development of asthma starts with allergen exposure leading to atopic sensitization and subsequent disease. Several studies support the progression from exposure to sensitization with the potential of extremely high levels of exposure leading to tolerance. Likewise, the progression from atopy to asthma is well documented,especially in genetically predisposed children. Recent intervention trials confirm these findings and begin to show promise for the prevention of asthma by interrupting the allergen exposure==>allergen sensitization==>atopic asthma pathway.

Non-atopic intrinsic asthma and the 'family tree' of chronic respiratory disease syndromes

We present a scheme below in which the most common forms of inflammatory diseases of the respiratory tract, notably atopic and non-atopic asthma and COPD, are depicted as separate offshoots from a common 'at-risk' pathway underpinned by genotypes related to aberrations in control of host defence and tissue repair mechanisms. We propose that entrance into this pathway is initially programmed by environmental experience during infancy and early childhood, in particular by severe lower respiratory tract infection, and that further progression towards expression of specific disease phenotype(s) is determined by the nature, timing and frequency of additional environmental insults subsequently encountered. At the one extreme, early sensitization of at-risk subjects to aeroallergens can potentially drive rapid progression towards expression of the atopic asthmatic phenotype under the dual onslaught of inflammatory responses to allergens/pathogens. At the opposite end of the spectrum the drip-feed effects of occasional infections on respiratory function(s) are amplified over a longer time frame by inflammation resulting from exposure to tobacco smoke and/or related chemical pollutants. Non-atopic asthma is envisaged to fit between these two extremes, being driven essentially by the downstream effects of respiratory infections alone in at-risk subjects. An important common factor in all three disease phenotypes is that acute exacerbations are typically driven by infections, the host responses to which display a characteristic T-helper type 2-like footprint, which in our view points to underlying genotype(s) which result in unbalanced host responses to respiratory pathogens.

Pediatric asthma and related allergic and nonallergic diseases: patient-oriented evidence-based essentials that matter

Asthma is the most common medical diagnosis among hospitalized children. In the USA, asthma has accounted for approximately 15% of nonsurgical admissions to hospital in the pediatric age group. Asthma is also one of the leading causes for emergency care requirements, one of the leading causes for missed school, and a cause for considerable morbidity, disability and occasional mortality at all ages. Despite these discouraging statistics, convincing data indicate that this failure of asthma management is not the result of inadequate therapeutic potential, but instead represents ineffective delivery of medical care. Management of asthma and its major co-morbidities, allergic and nonallergic rhinitis, and atopic dermatitis requires a knowledge of the alternative therapies, natural history, and educational techniques for providing patients and families with the ability to manage these troublesome chronic disorders.

Early identification of atopy in the prediction of persistent asthma in children

The long-term solution to the asthma epidemic is thought to be prevention, and not treatment of established disease. Atopic asthma arises from gene-environment interactions, which mainly take place during a short period in prenatal and postnatal development. These interactions are not completely understood, and hence primary prevention remains an elusive goal. We argue that primary-care physicians, paediatricians, and specialists lack knowledge of the role of atopy in early life in the development of persistent asthma in children. In this review, we discuss how early identification of children at high risk is feasible on the basis of available technology and important for potential benefits to the children. Identification of an asthmatic child's atopic status in early life has practical clinical and prognostic implications, and sets the basis for future preventative strategies.

Prevention of allergic respiratory disease in infants: current aspects and future perspectives

PURPOSE OF REVIEW

Primary and secondary prevention of severe atopic disease exemplified by atopic asthma represents an increasingly prominent focus of research in paediatric allergy. We review below the rationale for this approach and recent progress in development and testing of a range of potential preventive strategies.

RECENT FINDINGS

The principal areas reviewed relate to potential and currently available treatments targeting enhancement of overall immune functions, allergen-specific immunomodulation and respiratory viral infections, particularly during early childhood.

SUMMARY

The scientific rationale for prophylaxis of atopic diseases via early intervention strategies targeting young children is increasingly supported by findings from the experimental and clinical literature and significant progress may be expected in the mid-term future.

Wheezy babies--wheezy adults? Review on long-term outcome until adulthood after early childhood wheezing

Population-based birth cohort studies have documented that about 30% of children suffer from wheezing during respiratory infection before their third birthday. Recurrent wheezing is common in early childhood, but most patients outgrow their symptoms by school age. However, recent long-term postbronchiolitis follow-up studies from Sweden and Finland have revealed that asthma is present in about 40% of young adults and over half of the cases are relapses after many symptom-free years. In population studies, the principal predictors for later asthma have been parental asthma, recurrent wheezing, atopy and eosinophilia. In the Swedish postbronchiolitis study, atopic diathesis through the development of clinical atopy, and early passive smoking through bronchial hyper-reactivity or later active smoking led to adult asthma. The Finnish postbronchiolitis follow-up stressed early recurrence of wheezing, wheezing induced by less invasive viruses than respiratory syncytial virus (RSV), early-life atopy and eosinophilia and parental asthma as predictors for adult asthma.

CONCLUSION

The majority of wheezing infants and children outgrow their symptoms by school age, but based on recent long-term follow-up studies, asthma relapses are common in young adults. These studies have highlighted parental asthma, maternal smoking and wheezing induced by other viruses than RSV as predictive factors for later asthma.

IL-5 T-cell responses to house dust mite are associated with the development of allergen-specific IgE responses and asthma in the first 5 years of life

BACKGROUND

Allergen-specific T(H)2-like cytokine responses are considered to be important in sensitization and allergic diseases.

OBJECTIVE

To examine the profile of house dust mite (HDM) stimulated T-cell cytokines and their relationship to allergic disease in children over the period of the first 5 years of life.

METHODS

Subjects with a family history of asthma who were enrolled antenatally in the Childhood Asthma Prevention Study and had skin prick tests, clinical evaluation for asthma and eczema, and in vitro assessment of lymphocyte cytokine responses to HDM extract performed at ages 18 months (n = 281), 3 years (n = 349), and 5 years (n = 370). IL-13 at 3 and 5 years and IL-5, IL-10, and IFN- gamma at 18 months, 3 years, and 5 years were measured by ELISA.

RESULTS

House dust mite-specific cytokine responses increased with age for all cytokines except IFN-gamma. HDM-specific IL-5 responses at 3 years and 5 years were significantly positively related to skin prick test positivity at 5 years. IL-5 responses at 5 years were also significantly related to asthma at 5 years. Other HDM-specific cytokine responses were not related to asthma or eczema at 5 years. Responses were not altered by a HDM avoidance intervention.

CONCLUSION

IL-5 responses to HDM, the dominant local inhalant allergen, are related to the expression of clinical illness at age 5 years.

CLINICAL IMPLICATIONS

The T-cell response to HDM, as reflected in IL-5 production, is acquired over the first years of life and may play a role in the expression of allergic airways disease.

Early-onset atopy is associated with enhanced lymphocyte cytokine responses in 11-year-old children

BACKGROUND

Early age at onset of atopy is associated with more severe asthma and increased airway responsiveness (AR); the underlying mechanism is unclear but may involve T cell responses.

OBJECTIVE

To test the hypothesis that enhanced T cell responses may be associated with early-onset atopy.

METHODS

In a longitudinal study, atopy was determined in infancy and at 6 and 11 years of age. Individuals were categorized as persistent infant-onset atopy (PIOA), early childhood-onset atopy (ECOA) and later childhood-onset atopy (LCOA). At 11 years of age, peripheral blood T cell cytokine responses, AR, exhaled nitric oxide (FE(NO)) and forced expiratory volume in 1 s were determined.

RESULTS

The age at onset of atopy was determined for 60 children, of whom 15 had PIOA, 24 had ECOA and 21 had LCOA. An additional 76 children who were never atopic were also included. T cell responses to house dust mite, including interleukin-5, -9, -10 and tumour necrosis factor alpha, were higher among children with PIA and ECOA, and lower in children with LCOA, P<0.05. In contrast, those children with LCOA or who were not atopic had the highest IL-10 response to PHA (P=0.014). Children with PIOA and ECOA, but not LCOA, had higher AR and FE(NO) compared with non-atopic children (P<0.05). The group with PIOA were more likely among the atopic children to be admitted to hospital for asthma (P<0.05) and also had lower %FEV(1) compared with non-atopic children (P=0.023).

CONCLUSIONS

Early age at sensitization is associated with enhanced T cell cytokine responses and indices of adverse asthma outcome. T cell cytokine responses might be programmed at the time of initial atopic sensitization.

Aeroallergen sensitization rates in military children with rhinitis symptoms

BACKGROUND

Childhood sensitization rates for many aeroallergens are underreported.

OBJECTIVES

To examine aeroallergen sensitization rates in military children undergoing skin testing for rhinitis and investigate the timing of atopic development for perennial and seasonal allergens.

METHODS

A skin testing database was retrospectively analyzed. Children 18 years and younger referred for rhinitis underwent skin prick testing to either a screening panel of 8 tests or a standard panel of 51 allergens.

RESULTS

A total of 209 patients underwent skin testing to the 8-test panel. Of these patients, 35.4% had at least 1 positive result. Atopy increased with age, from 6.3% in those younger than 1 year to 58.8% in those 5 years old. The most common allergens were mold mix (16.3%), cat (13.2%), dust mite mix (11.4%), tree mix (9.4%), and grass mix (9.4%). Only 4.0% were sensitized to seasonal aeroallergens before the age of 3 years. A total of 345 children underwent testing to a 51-allergen panel. A total of 80.3% had at least 1 positive test result, and the average number of positive test results was 11.4. Both the percentage of atopy and the average number of positive skin test results increased with age. The most common allergens were grasses, Alternaria, and cottonwood. Thirty-two of 51 allergens were positive in 20% or more children. Rates for many underreported allergens are presented.

CONCLUSIONS

In children, aeroallergen sensitization rates are high and increase with age. Perennial allergens predominate up to the age of 3 years. Rates for many underreported allergens are presented. Although performed in a military population, these results should be applicable to many practices.

Predicting the development of early skin test sensitization in offspring of parents with asthma

BACKGROUND

The direct causal relationship between skin sensitization and asthma are controversial until now and remains to be further researched. Our aim is to analyse the role of parental asthma in the development of skin sensitization in offspring.

MATERIALS AND METHODS

This study was performed among nuclear families (determined by index of asthma patients), and subjects included parents and offspring. Parents were subdivided into four phenotypes on the basis of skin sensitization (SPT+ or SPT-) and asthma status (AST+ or AST-) and offspring were subdivided into three age groups: 3-8, 9-14 and 15-20 years. The main tests included a standard questionnaire and skin prick tests.

RESULTS

Offspring's skin sensitization differed among parental phenotypes at all ages (P < 0.05). In the SPT+/AST-, SPT-/AST+ and SPT+/AST+ groups, offspring were significantly more likely to be allergic than the ones in SPT-/AST- group at 3-8 years. Offspring with at least one parent with asthma were significantly more likely to have positive skin prick test response than those with non-asthmatic parents at age 3-8 years and 9-14 years, but not at 15-20 years among offspring with allergic parents. Results were independent of asthma in the children and of the characteristics of atopy in the parents.

CONCLUSION

Parent asthma history is an independent risk factor for allergic sensitization in their offspring in a Chinese population.

Parent-initiated oral corticosteroid therapy for intermittent wheezing illnesses in children: systematic review

AIM

Intermittent wheezing illnesses, which include viral-associated wheeze and asthma, are among the most common reasons for children to present urgently to a doctor. The objectives of this systematic review were to assess the benefits and harmful effects of parent-initiated oral corticosteroids (PIOCS) in the management of intermittent wheezing illness in children.

METHODS

The Cochrane Airways Group Specialised Register, The Cochrane Controlled Trials Register (CENTRAL), MEDLINE, EMBASE, LILACS, Web of Science and Dissertation Abstracts were searched. Only randomised clinical trials studying patients aged between 1 and 18 years, with an intermittent wheezing illness were included.

RESULTS

From 572 original citations, a total of two randomised clinical trials (303 randomised participants) were included. The quality of the included trials was high; however, marked clinical heterogeneity precluded a meta-analysis. The two trials did not find evidence that PIOCS are associated with a benefit in terms of hospital admissions, unscheduled medical reviews, symptoms scores, or bronchodilator use.

CONCLUSION

Limited current evidence is available and it is inconclusive regarding the benefit from PIOCS therapy in the treatment of intermittent wheezing illnesses in children. Oral corticosteroids have a clearly defined role in the management of acute asthma in the hospital setting. Therefore, it is reasonable for clinicians to recommend PIOCS when (i) the child has a history of severe acute asthma; and (ii) the parents are able to assess asthma status. However, widespread use of PIOCS cannot be recommended until the benefits and harms can be clarified further.

A comparison of proximity and land use regression traffic exposure models and wheezing in infants

BACKGROUND

We previously reported an association between infant wheezing and residence < 100 m from stop-and-go bus and truck traffic. The use of a proximity model, however, may lead to exposure misclassification.

OBJECTIVE

Results obtained from a land use regression (LUR) model of exposure to truck and bus traffic are compared with those obtained with a proximity model. The estimates derived from the LUR model were then related to infant wheezing.

METHODS

We derived a marker of diesel combustion--elemental carbon attributable to traffic sources (ECAT)--from ambient monitoring results of particulate matter with aerodynamic diameter < 2.5 microm. We developed a multiple regression model with ECAT as the outcome variable. Variables included in the model were locations of major roads, bus routes, truck traffic count, and elevation. Model parameter estimates were applied to estimate individual ECAT levels at infants' homes.

RESULTS

The levels of estimated ECAT at the monitoring stations ranged from 0.20 to 1.02 microg/m(3). A LUR model of exposure with a coefficient of determination (R(2)) of 0.75 was applied to infants' homes. The mean (+/- SD) ambient exposure of ECAT for infants previously categorized as unexposed, exposed to stop-and-go traffic, or exposed to moving traffic was 0.32 +/- 0.06, 0.42 +/- 0.14, and 0.49 +/- 0.14 microg/m(3), respectively. Levels of ECAT from 0.30 to 0.90 mug/m(3) were significantly associated with infant wheezing.

CONCLUSIONS

The LUR model resulted in a range of ECAT individually derived for all infants' homes that may reduce the exposure misclassification that can arise from a proximity model.

High prevalence of aeroallergen sensitization among infants of atopic parents

OBJECTIVE

To present methodology to identify atopic parents and determine the prevalence of sensitization to 15 aeroallergens in their infant offspring.

STUDY DESIGN

A birth cohort of infants was identified from birth records; an infant was enrolled if 1 of the parents reported allergy respiratory symptoms and had a positive skin prick test (SPT) to a common aeroallergen. At age 1 year, these infants were tested to the same aeroallergens.

RESULTS

Of the 680 enrolled infants, 28.4% were SPT+ to 1 or more aeroallergens and/or food, and 18.0% were positive to 1 or more aeroallergens. By category of allergens, 9.7% were sensitized to pollens, 7.5% to molds, 4.3% to house dust mite and/or cockroach, and 3.4% to dog and/or cat. Of the infants who were positive to an aeroallergen, 65.7% remained positive at age 2 years.

CONCLUSIONS

Infants born to atopic parents with percutaneous sensitization to aeroallergens are at increased risk for aeroallergen sensitization during infancy, which persists to age 2 years. These findings suggest that current clinical practices, which generally avoid skin testing before age 2 years, be reassessed in this population of high-risk children.

Relationship between childhood atopy and wheeze: what mediates wheezing in atopic phenotypes?

BACKGROUND

The nature of the relationship between childhood wheeze and atopy remains uncertain.

OBJECTIVE

To characterize childhood wheeze among atopic phenotypes in a longitudinal birth cohort study.

METHODS

A whole population birth cohort (N = 1,456) was recruited in 1989. Children were seen at birth and at 1, 2, 4, and 10 years of age to obtain information on asthma and allergic disease development and relevant risk factors for these states. Skin prick testing at ages 4 (n = 980) and 10 (n = 1,036) years was used to define atopic phenotypes. Wheezing in these states was characterized, and logistic regression was used to identify independent risk factors for wheeze onset in different atopic phenotypes.

RESULTS

Wheeze ever occurred in 37% of never atopics, 38% of early childhood atopics, 65% of chronic childhood atopics, and 52% of delayed childhood atopics. Chronic childhood atopics had significant wheezing morbidity and bronchial hyperresponsiveness. Their wheezing was associated with male sex, early eczema, family history of eczema, and early tobacco exposure. Never atopic wheeze was related to maternal asthma, parental smoking, and respiratory tract infections. Exclusive breastfeeding protected against early childhood atopic wheeze. Maternal asthma, family history of urticaria, and dog ownership increased delayed childhood atopic wheeze.

CONCLUSIONS

In many respects, chronic childhood atopy is the atopic phenotype associated with the most significant forms of childhood wheezing. In such children, heritable drive, allergens, and synergy with other environmental triggers seem to be crucial determinants of wheeze onset. Where such sensitization is absent, numerous environmental factors plus genetic predisposition may assume importance for wheezing.

Modification of dendritic cell function as a tool to prevent and treat allergic asthma

Atopic asthma is a chronic inflammatory disease of the airways, characterized by airway hyperreactivity and mucus hypersecretion that result in intermittent airway obstruction. This chronic inflammation is the result of an aberrant Th2-mediated response to innocuous environmental proteins. The prevalence of this disease has increased dramatically in the industrialized world in the last decades. Current treatment is mainly based on pharmacological interventions, which control the disease but are not curative. Although the etiology is not completely understood, it becomes increasingly clear that dendritic cells play an important role in both the sensitization phase and maintenance of the disease. In this review, we explore the different possibilities to exploit dendritic cell vaccines in order to prevent the development of (or inhibit established) atopic asthma.

Defining childhood atopic phenotypes to investigate the association of atopic sensitization with allergic disease

AIMS

Although atopic sensitization is common in childhood, its relationship to clinical allergic disease remains incompletely understood. We therefore sought to explore this relationship by defining sensitization based atopic phenotypes.

METHODS

Children were recruited at birth (n = 1456) and reviewed at 1, 2, 4 and 10 years. Skin prick testing (SPT) to common allergens was done at 4 (n = 980) and 10 years (n = 1036) with lung function (n = 981), bronchial challenge (n = 784) and serum IgE (n = 953) testing at 10. Atopic phenotypes were defined, by sensitization pattern, for children with SPT at both 4 and 10 years (n = 823).

RESULTS

Of phenotyped children, 68.0% were never atopic, 4.3% early childhood atopic (only atopic at age 4), 16.5% chronic childhood atopics (at 4 and 10 years) and 11.2% delayed childhood atopics (only at 10). Never atopics showed small but identifiable prevalence of allergic diseases such as asthma, eczema and rhinitis. Amongst allergen-sensitized subjects, aeroallergen predominated over food sensitization throughout childhood. Chronic childhood atopics showed highest prevalence of lifetime plus persistent wheeze, eczema and rhinitis, increased prevalence of aeroallergen sensitization, some evidence of persistent food sensitization, significantly greater cord IgE than never atopics (P = 0.006), plus higher total IgE (P < 0.001) and bronchial hyper-responsiveness (P < 0.001) at 10 years than other phenotypes.

CONCLUSION

A proportion of childhood eczema, rhinitis and asthma is nonatopic. The commonest childhood pattern of atopy is chronic sensitization, associated with early, persisting and clinically significant allergic disease. The currently accepted childhood 'Allergic March' may oversimplify the natural history of childhood atopy and allergic disease.

Induction and inhibition of the Th2 phenotype spread: implications for childhood asthma

The interactions between genetic and environmental factors play a major role in the development of childhood asthma. We hypothesized that a pre-existing Th2/asthmatic response can promote Th2 responses to newly encountered Ags (i.e., phenotype spread). To test this hypothesis, we developed a mouse model in which the requirements for the induction and inhibition of phenotype spread to a clinically relevant neo-allergen (i.e., ragweed) were investigated. Our results indicate that 1) phenotype spread to the neo-allergen can be induced only within the first 8 h after a bronchial challenge with the first Ag (OVA); 2) Th2 differentiation of naive CD4(+) T cells occurs in bronchial lymph nodes; 3) trafficking of naive CD4(+) T cells to local lymph nodes and IL-4 produced by OVA-activated Th2 cells play essential roles in the differentiation of naive CD4(+) T cells to Th2 cells; and 4) suppression of the production of chemokines involved in the homing of naive CD4(+) T and Th2 cells to bronchial lymph nodes by a TLR9 agonist inhibited phenotype spread and abrogated the consequent development of experimental asthma. These findings provide a mechanistic insight into Th2 phenotype spread and offer an animal model for testing relevant immunomodulatory interventions.

A review of the effects of breastfeeding on respiratory infections, atopy, and childhood asthma

The etiology of childhood asthma is not fully understood. Early exposure to certain respiratory infections may be protective for atopy and/or asthma whereas some infections have been suggested to exert the opposite effects. Wheezing lower respiratory illness (LRI) in the first year of life and atopy are independently associated with increased risk for current asthma in childhood and their effects are mediated via different causal pathways. These risk factors are multiplicative when they operate concommitantly within individual children. Exclusive breastfeeding protects against asthma via effects on both these pathways, as well as through other as yet undefined mechanisms. Furthermore, exclusive breastfeeding may protect against asthma and may reduce the incidence of lower respiratory illness, especially respiratory syncytial virus (RSV). We have previously demonstrated a protective effect of exclusive breastfeeding on asthmatic traits in children. The aim of this review was to clarify this protective association from intermediate associations with respiratory infections, atopy, or through other facets of breastfeeding. The bioactivity of breast milk and subsequent pathways that may act upon the development of asthma in children are explored.

Drug development strategies for asthma: in search of a new paradigm

The spiraling costs of asthma treatment seem set to continue rising, given the equivocal performance of the latest generation of specific anti-inflammatory drugs in trials in adult asthmatics. We argue that the continuation of this trend is inevitable unless there is a substantial realignment of entrenched drug development policy in the pharmaceutical industry and a parallel shift in licensing policy by regulatory authorities to encourage the development of drugs capable of halting the progression from acute to chronic asthma when the disease first manifests in childhood. The theoretical framework for such an approach, including proof-of-principle data from studies in children with early-stage disease and a range of candidate drugs, already exists. What is needed is informed debate on the risks versus potential benefits of this approach.

Asthma, allergy, and upper airway disease

The practitioner must be aware of the strong interrelationship between asthma, allergy, eczema, otitis media, viral upper respiratory infection, and sinusitis. When allergy, eczema, otitis media (particularly after the age of 2 years), viral upper respiratory infection, or sinusitis is present in a patient, asthma must be considered as possible sequelae. If a patient has symptoms of intermittent or persistent asthma, consideration must be given to the presence of allergy, eczema, otitis media, viral upper respiratory infection, or sinusitis as comorbid conditions or possible triggers for the asthma symptoms. Failure to evaluate the entire upper and lower airway for these interrelated conditions will result in incomplete treatment and incomplete symptom relief [61]. This article reviews the strong association between diseases of the upper and lower airway [62,63]. Treatment and control of upper airway symptoms is essential for control of asthma symptoms. Control of allergy, eczema, otitis, sinusitis, and viral symptoms result in improved outcomes for asthma patients. Reduction of these asthma triggers and comorbid conditions is also likely to reduce asthma medication requirements while improving symptoms status.

Age-specific relationship between CD14 and atopy in a cohort assessed from age 8 to 25 years

CD14 influences postnatal switching of T helper cell responses. CD14 C-159T has been associated with altered CD14 and IgE levels in cross-sectional studies. Identifying whether associations vary with age requires data from children of the same age followed longitudinally over many years. In this study, an unselected population with extensive longitudinal data was used to test the hypothesis that CD14 C-159T was associated with early-onset atopy. A total of 305 subjects were assessed on up to seven occasions between ages 8 and 25 years by questionnaire, histamine challenge, and skin prick test. For atopy, airway hyperresponsiveness (AHR), and wheeze, each subject was classified as having early onset, late onset, or no disease onset during follow-up. Compared with subjects with -159CT and -159TT, subjects with -159CC had an odds ratio of 2.2 (p = 0.018) for early-onset atopy and an odds ratio of 2.6 (p = 0.019) for early-onset AHR. Cross-sectional analysis showed increased prevalence of -159CC in subjects with atopy and AHR in childhood but not adulthood. These data suggest that the influence of CD14 -159C on the atopic phenotype may be age specific, exerting an effect during midchildhood, which is no longer apparent by early adulthood.

Early sensitisation and development of allergic airway disease - risk factors and predictors

The development and phenotypic expression of allergic airway disease depends on a complex interaction between genetic and several environmental factors, such as exposure to food, inhalant allergens and non-specific adjuvant factors (e.g. tobacco smoke, air pollution and infections). The first months of life seem to be a particularly vulnerable period and there is evidence that sensitisation is related to the level of allergen exposure during early life. At present, the combination of atopic heredity and elevated cord-blood IgE seems to result in the best predictive discrimination as regards development of allergic disease at birth. Early sensitisation, cow's milk allergy and atopic eczema are predictors for later development of allergic airway disease. Exposure to indoor allergens, especially house dust mite allergens, is a risk factor for sensitisation and development of asthma later in childhood in high-risk infants and infants with early atopic manifestations.

The role of allergy in the development of airway inflammation in children

The primary immune response to allergens is the prototypic T-helper cell type 2 (Th2) response. This occurs prenatally, favoured by the normal Th2-skewed immune response of pregnancy. The immune system matures during the early years of life. The immune responses, primarily determined by genetic susceptibility, are also influenced by exposure to allergens and infections, which may reverse their direction. Although wheezing is observed before 2 years of age, this is usually not attributable to allergy, and the majority of the wheezers do not develop asthma. The development of allergic asthma can be considered to be a two-stage process. The first stage involves the development of allergen-specific immunological memory against inhaled allergens. This happens in childhood and polarises the immune response towards a Th2 phenotype. These individuals are therefore more prone to developing allergic inflammation. Stage two involves the consolidation and maintenance of this polarised Th2 response, leading to a state of chronic airway inflammation. This second phase is influenced by various factors, for example respiratory viral infections, repeated indoor and outdoor allergen exposure, environmental tobacco smoke and air pollutants. The persistent airway inflammation leads to tissue remodelling and airway hyperresponsiveness, the clinical sine qua non of asthma.

Food allergy: what can be done to prevent progression to asthma?

OBJECTIVES

The primary objective of this review is to discuss risk factors for asthma development in food allergen-sensitized children. In the paper we discuss the possible measures to prevent progression to asthma by allergen and other adjuvant factor avoidance.

DATA SOURCES

A review from literature of articles on these topics was performed.

STUDY SELECTION

Relevant publications on asthma risk factors and implementation of protective factors were critically evaluated.

RESULTS

Children with familiar history of atopy and sensitization to food proteins in early infancy are at high risk of subsequent respiratory allergic diseases and require specific prevention. Because early allergic sensitization is a significant risk factor for later development of asthma, prevention of asthma by early allergen avoidance is mandatory in high-risk children. Adjuvant factors such as tobacco smoke and mold exposure may act as nonspecific triggers for the development of atopy. The role of protective factors such as infections in early life, breast-feeding, a "healthy" diet needs to be evaluated in prospective studies. Pharmacologic intervention with antihistamines led to significant reduction in incidence of asthma in high-risk children, but confirmatory longitudinal studies in large populations are necessary.

CONCLUSIONS

There is now accumulating evidence that preventing exposure to house-dust mite may significantly reduce the prevalence of childhood asthma. However, allergen avoidance can not be recommended as the only strategy. Avoidance of adjuvant factors and implementation of potential protective factors aimed to reduce the risk to progression to asthma need to be evaluated in prospective studies.

The role of airway dendritic cell populations in regulation of T-cell responses to inhaled antigens: atopic asthma as a paradigm

Chronic atopic asthma in adulthood represents the end stage of a disease process that is initiated during the perinatal period, when the naive immune system is first confronted with potentially allergenic airborne antigens. The initial phase involves compartmentalization of immunological memory into either the T-helper (Th)-1 or Th2 cytokine phenotypes, in atopic and nonatopics, respectively, and in a subset of atopics, this results in chronic Th2 cytokine-driven inflammation in the airways. Dendritic cells appear to play a key role in directing the memory generation process, and in subsequently controlling the intensity and duration of the ensuing Th-cell responses responsible for this inflammation.

Risk factors determining allergic airway diseases in Turkish subjects

With regard to changes in life-style after the 1980s, the reflection of environmental factors on the evolution of allergic airway disease (AAD) has not yet been analyzed in Turkey. In this trial, we aimed to determine the factors related to AAD in Turkish subjects. Patients diagnosed as having asthma and/or rhinitis with positive skin prick tests (SPTs) were accepted as members of the "atopic group" (n = 235). Subjects demonstrated to have negative SPTs and no clinical evidence of any atopic disorder were accepted as members of the "nonatopic control group" (n = 84). Data obtained from a questionnaire applied cross-sectionally to the study groups were compared for risk factor analysis. According to the results of univariate analysis, nonatopic controls were found to have been born in villages more frequently than those in the atopic group (14.3% vs. 4.7%, p = 0.02). Atopic group members had lived in apartments during childhood more frequently than nonatopic controls (53.6% vs. 38%, p = 0.04). A topic group members, particularly the asthmatics, had lower sibship size (< or = 1 sibling) (41.3% vs. 16.7%, p = 0.0003) and nonatopic subjects had higher sibship size (> or = 3 siblings) (73.8% vs. 43.4%, p < 0.0001). The rate of maternal atopy was higher in the atopic group (24.7% vs. 9.5%, p = 0.02). Place of birth, sibship size, and atopic status of the mother, but not house type, were found to be significant in the multivariate analysis. As a conclusion, rural life-style seems to have a protective effect on the development of atopy in Turkey. On the contrary, factors directly or indirectly related to urban life-style during early childhood were found to be associated with the allergic airway diseases.

Effect of age on allergen-induced structural airway changes in brown Norway rats

It remains to be fully established whether allergen-induced airway inflammation and remodeling are influenced by age. The aim of the present study was to compare allergen-induced airway changes in young and adult rats. Brown Norway rats were sensitized at 4 weeks of age (young) or 13 weeks of age (adult) and exposed to aerosolized ovalbumin (OA) or phosphate-buffered saline for 2 weeks. In both age groups OA exposure induced an increase in OA-specific Immunoglobulin E and in the number of peribronchial eosinophils. OA-challenged animals also developed an increase in total airway wall area, enhanced fibronectin deposition, and goblet cell hyperplasia. Both inflammatory and structural alterations were more pronounced in the airways of young compared with adult OA-exposed rats. The number of peribronchial eosinophils was increased in young animals (685.4 +/- 75.0 versus 389.9 +/- 37.8/mm2 in adult rats; p < 0.001). A higher degree of goblet cell hyperplasia was observed in young rats (65.37 +/- 4.68 versus 34.74 +/- 3.68/mm basement membrane in adult rats; p < 0.001) and area of fibronectin deposition in the airway wall was higher in young compared with adult animals (5.08 +/- 0.46 versus 3.62 +/- 0.29 microm2/microm basement membrane; p < 0.005). In conclusion, in young rats airways are more susceptible to allergen-induced inflammatory and structural airway changes.

Do levels of immunoglobulin G antibodies to foods predict the development of immunoglobulin E antibodies to cat, dog and/or mite?

BACKGROUND

In children at high risk of inhalation allergy, food sensitization is associated with an increased risk for sensitization to inhalant allergens. Furthermore, this association was also found in a cross-sectional study.

OBJECTIVE

To examine in a prospective study, whether levels of IgG to foods (i.e. mixture of wheat and rice, mixture of soy bean and peanut, egg white, cow's milk, meat, orange and potato) indicate an increased risk for the future development of IgE antibodies to inhalant allergens in a low-risk population and whether they can be used as predictors of the subsequent development of IgE antibodies in young, initially IgE-negative children.

METHODS

Coughing children, aged 1-5, visiting their GPs, were tested for IgE antibodies to mite, dog and cat (RAST) and IgG (ELISA) to foods. All IgE-negative children were retested for IgE antibodies after two years. The IgG results (66 percentiles) of the first blood sample were compared to the RAST-scores of the second blood sample.

RESULTS

After two years, 51 out of 397 (12.8%) originally IgE-negative children, had become IgE-positive for cat, dog and/or mite. An increased IgG antibody level to wheat-rice (OR = 2.2) and to orange (OR = 2.0) indicated an increased risk of developing IgE to cat, dog or mite allergens. In addition to IgG to a mixture of wheat-rice and orange; total IgE, breastfeeding, eczema as a baby and age were the most important predictors for the subsequent development of IgE to inhalant allergens.

DISCUSSION

An increased IgG antibody level to a mixture of wheat-rice or orange, indicates an increased risk of developing IgE to cat, dog or mite allergens. This indicates that excessive activity of the mucosal immune system is present before IgE antibodies to airborne allergens can be demonstrated. Nevertheless, IgG to foods is not very helpful (with a positive predictive value of 16.5%, and negative predictive value of 90.6%) in identifying individual children at risk in clinical practice. However, besides other risk factors, IgG to wheat-rice and to orange could be useful as a screening test for studies in the early identification, i.e. before IgE antibodies can be detected, of children with an increased risk of developing IgE antibodies in the future.

The pattern of atopic sensitization is associated with the development of asthma in childhood

BACKGROUND

Even though atopic sensitization has been shown to be strongly associated with childhood asthma, asthma eventually develops in only one third of atopic children.

OBJECTIVE

The aim of this study was to prospectively investigate the pattern of atopic sensitization typically associated with the development of asthma in childhood.

METHODS

The German Multicenter Allergy Study followed 1314 children from birth to the age of 7 years. Parental questionnaires on asthma and asthmatic symptoms were completed 6 times up to the age of 2 years and from then on yearly. Determination of specific IgE to 9 food and inhalant allergens was performed yearly, and at the age of 7 years, a bronchial histamine challenge was conducted.

RESULTS

Onset of atopic sensitization in atopic children with current asthma at the age of 7 years was significantly earlier than in atopic children without current asthma (39.4% before age 1 year vs 21.0%, P =.015). Early atopic sensitization without any sensitization to inhalant allergens at the age of 7 years conferred no increased risk for asthma at this age. Only those children sensitized to any allergen early in life and sensitized to inhalant allergens by the age of 7 years were at a significantly increased risk of being asthmatic at this age (odds ratio, 10.12; 95% CI, 3.81-26.88). However, even in this group of persistently sensitized children, the risk of being asthmatic at the age of 7 years was only increased if a positive parental history of asthma or atopy was present (odds ratio, 15.56; 95% CI, 5.78-41.83), with the effect being strongest for maternal asthma.

CONCLUSION

Our results indicate that an underlying factor pertaining to asthma and maternal transmission may determine both a certain pattern of sensitization and the expression of asthma.