Key factors in the development of asthma: atopy

Dual Effect of Low-Molecular-Weight Bioregulators of Bacterial Origin in Experimental Model of Asthma

Asthma is one of the most common noncommunicable diseases, affecting over 200 million people. A large number of drugs control asthma attacks, but there is no effective therapy. Identification of reasons for asthma and preventing this disease is a relevant task. The influence of bacterial components is necessary for the normal development of the immune system and the formation of an adequate immune response to antigens. In the absence of microorganisms or their insufficient exposure, the prerequisites are formed for excessive reactivity to harmless antigens. In the present study, we analyzed cellular and humoral factors in a standard mouse model of OVA-induced asthma modified by 5-fold intraperitoneal injection of bacterial cell wall fragments of glucosaminylmuramyl dipeptide (GMDP) 5 μg/animal or 1 μg lipopolysaccharide (LPS) per animal for 5 days before sensitization by ovalbumin (OVA). Preliminary administration of LPS or GMDP to animals significantly reduced goblet cells as well as the number of neutrophils, lymphocytes, and eosinophils in bronchoalveolar lavage, wherein GMDP corrected neutrophilia to a 2-fold degree, and LPS reduced the severity of eosinophilia by 1.9 times. With OVA administration of GMDP or LPS at the sensitization stage, an increase in the total number of bronchoalveolar lavage cells due to neutrophils, macrophages, lymphocytes, and eosinophils in relation to the group with asthma without GMDP or LPS was observed. The administration of GMDP or LPS to normal mice without asthma for 5 days had no statistically significant effect on the change in the number and population composition of cells in bronchoalveolar lavage in comparison with the control group receiving PBS. As a result of a study in a mouse model of asthma, a dual effect of LPS and GMDP was established: the introduction of LPS or GMDP before sensitization reduces neutrophilia and eosinophilia, while the introduction of LPS or GMDP together with an allergen significantly increases neutrophilia and eosinophilia. The study of the immunoglobulin status shows that in normal-asthma mice, GMDP and LPS slightly increase IgA in bronchoalveolar lavage; at the same time, in the asthma model, injections of GMDP or LPS before sensitization contribute to a significant decrease in IgA (2.6 times and 2.1 times, respectively) in BALF and IgE (2.2 times and 2.0 times, respectively) in blood serum. In an experimental model of asthma, the effect of GMDP and LPS was multidirectional: when they are repeatedly administered before sensitization, the bacterial components significantly reduce the severity of the allergic process, while in the case of a joint injection with an allergen, they increase the influx of macrophages, lymphocytes, and neutrophils into the lungs, which can aggravate the course of pathological process. Thus, the insufficient effect of antigens of a bacterial nature, in particular, with prolonged use of antibiotics can be compensated for by substances based on low-molecular-weight bioregulators of bacterial origin to establish the missing signals for innate immunity receptors, whose constant activation at a certain level is necessary to maintain homeostasis.

Dysbiosis in Pediatrics Is Associated with Respiratory Infections: Is There a Place for Bacterial-Derived Products?

Respiratory tract infections (RTIs) are common in childhood because of the physiologic immaturity of the immune system, a microbial community under development in addition to other genetic, physiological, environmental and social factors. RTIs tend to recur and severe lower viral RTIs in early childhood are not uncommon and are associated with increased risk of respiratory disorders later in life, including recurrent wheezing and asthma. Therefore, a better understanding of the main players and mechanisms involved in respiratory morbidity is necessary for a prompt and improved care as well as for primary prevention. The inter-talks between human immune components and microbiota as well as their main functions have been recently unraveled; nevertheless, more is still to be discovered or understood in the above medical conditions. The aim of this review paper is to provide the most up-to-date overview on dysbiosis in pre-school children and its association with RTIs and their complications. The potential role of non-harmful bacterial-derived products, according to the old hygiene hypothesis and the most recent trained-innate immunity concept, will be discussed together with the need of proof-of-concept studies and larger clinical trials with immunological and microbiological endpoints.

Lipopolysaccharide Exposure Alleviates Asthma in Mice by Regulating Th1/Th2 and Treg/Th17 Balance

Background

It is generally believed that endotoxin exposure exacerbates risk of developing asthmatic symptoms. However, recent studies have indicated that prior bacterial exposure may prevent future symptoms of asthma. Here, we evaluated the influence of pre-exposure to different concentrations of lipopolysaccharide (LPS) to subsequent ovalbumin (OVA) allergen sensitization and challenge.

Material/Methods

Four-week-old Balb/c mice were treated intranasally with varying concentrations of LPS (1 ug, 10 ug, and 100 ug) or sterile PBS for 10 days, then 2 weeks later they were exposed to OVA. Both the molecular and functional airway responses to OVA administration were assessed following prior exposure to different doses of LPS or controls. Additionally, the Th1/Th2 and Treg/Th17 balance was measured.

Results

Airway responsiveness and immune cell recruitment in the bronchoalveolar lavage (BALF) were decreased in animals exposed to a low dose of LPS (1 ug) treatment compared with the asthma group. Moderate-dose (10 ug) and high-dose (100 ug) LPS administration showed no differences from controls. Further, low-dose LPS (1 ug) exposure was associated with increased Th1 cytokines, T-bet, Treg cytokine (IL-10, TGF-β), and Foxp3 expression, but decreased Th2 cytokines (IL-4,5,13), GATA3, Th17, and ROR-γt expression compared with the asthma group. Finally, higher numbers of CD4+CD25+Foxp3+Treg cells, and CD4+INF-γ+T cells, and lower CD4+IL-4+T cells and CD4+IL-17+T cells were observed in the low-dose LPS-treated groups compared to controls.

Conclusions

Our findings suggest that prior exposure to low doses of LPS may protect from OVA-induced airway hyperresponsiveness (AHR) and histopathologic changes through regulation of the Th1/Th2 and Treg/Th17 balance.

Prenatal maternal psychosocial stress and offspring's asthma and allergic disease: A systematic review and meta-analysis

BACKGROUND

Prenatal maternal stress may influence offspring's atopic risk through sustained cortisol secretion resulting from activation of the hypothalamic-pituitary axis (HPA), leading to Th2-biased cell differentiation in the foetus. We undertook a systematic review and meta-analysis investigating the relationship between prenatal maternal psychosocial stress and risk of asthma and allergy in the offspring.

METHODS

We searched 11 electronic databases from 1960 to 2016, searched the grey literature and contacted experts in the field. Type of stress indicator included mood disorders, anxiety, exposure to violence, bereavement and socio-economic problems occurring during pregnancy, both objectively and subjectively measured. We included all possible asthma and IgE-mediated allergy outcomes. We conducted random-effects meta-analyses to synthesize the data.

RESULTS

We identified 9779 papers of which 30 studies (enrolling >6 million participants) satisfied inclusion criteria. The quality of 25 studies was moderate, 4 were strong, and one was weak. Maternal exposure to any type of stressors was associated with an increased risk of offspring atopic eczema/dermatitis (OR 1.34, 95% CI 1.22-1.47), allergic rhinitis (OR 1.30, 95% CI 1.04-1.62), wheeze (OR 1.34, 95% CI 1.16-1.54) and asthma (OR 1.15, 95% CI 1.04-1.27). Exposure to anxiety and depression had strongest effect compared to other stressors. Exposure during the third trimester had the greatest impact compared to first and second trimesters. The increased risk was stronger for early-onset and persistent than for late-onset wheeze. Bereavement of a child (HR 1.28, 95% CI 1.10-1.48) or a spouse (HR 1.40, 95% CI 1.03-1.90) increased the risk of offspring asthma.

CONCLUSIONS

Exposure to prenatal maternal psychosocial stress was associated with increased risk, albeit modestly, of asthma and allergy in the offspring. The pronounced risk during the third trimester may represent cumulative stress exposure throughout pregnancy rather than trimester-specific effect. Our findings may represent a causal effect or a result of inherent biases in studies, particularly residual confounding.

Comparison of the roles of house dust mite allergens, ovalbumin and lipopolysaccharides in the sensitization of mice to establish a model of severe neutrophilic asthma

Neutrophilic asthma (NA) is associated with a severe disease course and poor response to corticosteroids. The present study aimed to compare the effects of various concentrations of house dust mite (HDM) allergens, ovalbumin (OVA), the major egg allergen, and lipopolysaccharide (LPS) in combination on the onset of severe NA. Female C57BL/6 mice were grouped according to a random number table and intranasally sensitized with HDM/LPS/OVA extracts on days 0, 1 and 2 of the study. In group 1, mice received 50 µg HDM + 50 µg OVA + 15 µg LPS, mice in group 2 received 50 µg HDM + 100 µg OVA + 15 µg LPS, mice in group 3 received 100 µg HDM + 50 µg OVA + 15 µg LPS and those in group 4 received 100 µg HDM + 100 µg OVA + 15 µg LPS, while mice in the control group received saline only. The mice were then challenged by OVA solution with atomized excitation on days 14, 15, 18, 19 and 20 for 30 min each. Ethology, airway hyperresponsiveness (AHR), immune cell distributions in bronchoalveolar lavage fluid (BALF), and specific cytokines interleukin 17A (IL-17A) and IL-4 in serum were assessed. Histological examination of inflammation by hematoxylin and eosin staining and immunohistochemical assessment of neutrophils (NEU), eosinophils (EOS), IL-17A and IL-4 were also performed. Compared with the control group, the HDM/OVA/LPS-sensitized groups 1-4 had markedly increased BALF cells, serum interleukin IL-17A and IL-4, inflammatory cell infiltration, EOS as well as IL-17A and IL-4 by immunohistochemical staining (all P<0.05). Among the four HDM/OVA/LPS-sensitized groups, mice of group 4 had higher AHR, a significantly higher total cell number, NEU and EOS in BALF as well as significantly higher NEU and NEU/EOS ratios according to immunohistochemical staining when compared to groups 1-3 (P<0.05 for all). In conclusion, sensitization with 100 µg HDM + 100 µg OVA + 15 µg LPS successfully established a severe asthma model with a predominantly neutrophilic inflammatory phenotype.

Extracellular vesicles, especially derived from Gram-negative bacteria, in indoor dust induce neutrophilic pulmonary inflammation associated with both Th1 and Th17 cell responses

BACKGROUND

Many bacterial components in indoor dust can evoke inflammatory pulmonary diseases. Bacteria secrete nanometre-sized vesicles into the extracellular milieu, but it remains to be determined whether bacteria-derived extracellular vesicles in indoor dust are pathophysiologically related to inflammatory pulmonary diseases.

OBJECTIVE

To evaluate whether extracellular vesicles (EV) in indoor air are related to the pathogenesis of pulmonary inflammation and/or asthma.

METHODS

Indoor dust was collected from a bed mattress in an apartment. EV were prepared by sequential ultrafiltration and ultracentrifugation. Innate and adaptive immune responses were evaluated after airway exposure of EV.

RESULTS

Repeated intranasal application of indoor-dust-induced neutrophilic pulmonary inflammation accompanied by lung infiltration of both Th1 and Th17 cells. EV 50-200 nm in diameter were present (102.5 μg protein concentration/g dust) in indoor dust. These vesicles were internalized by airway epithelial cells and alveolar macrophages, and this process was blocked by treatment of polymyxin B (an antagonist of lipopolysaccharide, an outer-membrane component of Gram-negative bacteria). Intranasal application of 0.1 or 1 μg of these vesicles for 4 weeks elicited neutrophilic pulmonary inflammation. This phenotype was accompanied by lung infiltration of both Th1 and Th17 cells, which were reversed by treatment of polymyxin B. Serum dust EV-reactive IgG1 levels were significantly higher in atopic children with asthma than in atopic healthy children and those with rhinitis or dermatitis.

CONCLUSION & CLINICAL RELEVANCE

Indoor dust EV, especially derived from Gram-negative bacteria, is a possible causative agent of neutrophilic airway diseases.

Epigenetics and prenatal influences on asthma and allergic airways disease

Uterine life is arguably the most critical time in developmental programming, when environmental exposures may have the greatest potential to influence evolving fetal structure and function. There has been substantial progress in understanding the epigenetic mechanisms through which environmental exposures can permanently alter the expression of fetal genes and contribute to the increasing propensity for many complex diseases. These concepts of "developmental origins" of disease are being applied across virtually all fields of medicine, and emerging epigenetic paradigms are the likely mechanism behind the environment-driven epidemic of asthma and allergic disease. Here, we examine the epigenetic regulation of immune development and the early immune profiles that contribute to allergic risk. In particular we review new evidence that key environmental exposures, such as microbial exposure, dietary changes, tobacco smoke, and pollutants, can induce epigenetic changes in gene expression and alter disease risk. Although most of these factors have already been clearly implicated in epidemiologic studies of asthma and allergic disease, new studies investigating the mechanisms of these effects may provide new avenues for using these pathways for disease prevention.

Allergen-induced airway inflammation and its therapeutic intervention

Allergen inhalation challenge has been useful for examining the mechanisms of allergen-induced airway inflammation and the associated physiological changes and for documenting the efficacy of drugs to treat asthma. Allergen inhalation by a sensitized subject results in acute bronchoconstriction, beginning within 15-30 min and lasting 1-3 hr, which can be followed by the development of a late asthmatic response. Individuals who develop both an early and late response after allergen have more marked increases in airway hyperresponsiveness, and greater increases in allergen-induced airway inflammation, particularly in airway eosinophils and basophils. All of the currently available and effective treatments for asthma modify some aspects of allergen-induced responses. These medications include short-acting and long-acting inhaled β₂-agonists, inhaled corticosteroids, cromones, methylxanthines, leukotriene inhibitors, and anti-IgE monoclonal antibody. In addition, allergen inhalation challenge has become a useful method which can, in a very limited number of patients, provide key information on the therapeutic potential of new drugs being developed to treat asthma.

Antenatal steroid therapy and childhood asthma: Is there a possible link?

This paper presents a hypothesis that fetal exposure to corticosteroids is an independent risk factor for the development of asthma in childhood. The prevalence of childhood asthma saw a dramatic rise from the 1980s up until the early 2000s. Among the explanations for the increase in asthma prevalence included interest in exposures arising in the gestational period. Overlapping the time period of the increasing prevalence of childhood asthma is the increased use of antenatal corticosteroid therapy for fetal lung maturation. Through an examination of the published literature, a time dependent association between year of birth (and hence exposure to the antenatal corticosteroids) and the relationship between preterm birth and childhood asthma is noted. A brief review of the trends in the prevalence of asthma, the use of antenatal corticosteroids including their established latent effects and the time dependant association between preterm birth and the risk of childhood asthma are provided.

The allergen bronchoprovocation model: an important tool for the investigation of new asthma anti-inflammatory therapies

Allergen bronchoprovocation tests have been used for more than two decades in the investigation of respiratory allergic diseases such as asthma and rhinitis. These bronchial challenges are now well standardized and can offer key information on the therapeutic potential of new agents and on their anti-inflammatory effects on the airways. Both standard and low-dose allergen provocations are safe when performed by experienced investigators and do not lead to persistent worsening of asthma or change in airway function. The evaluation of new therapeutic agents by these methods can also provide important information on the mechanisms of development and persistence of airway diseases.

Mouse allergen-specific antibody responses in inner-city children with asthma

BACKGROUND

Although mouse allergen exposure is common in inner-city homes, little is known about the relationships between exposure and humoral immune responses to mouse allergen in this population.

OBJECTIVE

To examine relationships between mouse allergen exposure and allergen-specific IgE and IgG responses in inner-city children with asthma.

METHODS

Inner-city children with asthma underwent skin testing and venipuncture for determination of mouse allergen-specific IgE and IgG levels. Settled dust samples were collected from their homes for allergen analysis.

RESULTS

The study population (n = 112) was predominantly African American (92%) with a mean age of 4.4 years. The prevalence rate of mouse sensitization was 25% and did not consistently increase with increasing Mus m 1 levels. Instead, the prevalence rate was lowest among those exposed to <2 microg/g, increased among those exposed to 2-7.9 microg/g and 8-29.9 microg/g, and then decreased among participants exposed to >29.9 microg/g (14%, 20%, 40%, and 28%, respectively). Similarly, the prevalence rates of mouse allergen-specific IgG and IgG(4) did not increase across increasing exposure categories. Mouse allergen-specific IgG and IgG(4) were strongly associated with IgE sensitization (odds ratios [95% CI], 82.8 [20.5-334.4] and 50.4 [14.0-181.7], respectively).

CONCLUSION

High-level exposure to mouse allergen in children may be associated with attenuated humoral responses of all isotypes rather than selective attenuation of IgE.

CLINICAL IMPLICATIONS

Protection against allergic sensitization by high-dose allergen exposure may not be mediated by preferential production of IgG over IgE.

Modulation of the infant immune responses by the first pertussis vaccine administrations

Many efforts are currently made to prepare combined vaccines against most infectious pathogens, that may be administered early in life to protect infants against infectious diseases as early as possible. However, little is known about the general immune modulation induced by early vaccination. Here, we have analyzed the cytokine secretion profiles of two groups of 6-month-old infants having received as primary immunization either a whole-cell (Pw) or an acellular (Pa) pertussis vaccine in a tetravalent formulation of pertussis-tetanus-diphtheria-poliomyelitis vaccines. Both groups of infants secreted IFN-gamma in response to the Bordetella pertussis antigens filamentous haemagglutinin and pertussis toxin, and this response was correlated with antigen-specific IL-12p70 secretion, indicating that both pertussis vaccines induced Th1 cytokines. However, Pa recipients also developed a strong Th2-type cytokine response to the B. pertussis antigens, as noted previously. In addition, they induced Th2-type cytokines to the co-administrated antigen tetanus toxoïd, as well as to the food antigen beta-lactoglobulin. Furthermore, the general cytokine profile of the Pa recipients was strongly Th2-skewed at 6 months, as indicated by the cytokines induced by the mitogen phytohaemagglutinin. These data demonstrate that the cytokine profile of 6-month-old infants is influenced by the type of formulation of the pertussis vaccine they received at 2, 3 and 4 months of life. Large prospective studies would be warranted to evaluate the possible long-term consequences of this early modulation of the cytokine responses in infants.

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.

Are atopy and specific IgE to mites and molds important for adult asthma?

BACKGROUND

Atopy is known to be important for childhood asthma, but this is to our knowledge the first study on its relation with development of asthma in adulthood.

OBJECTIVES

We addressed the role of atopy, measured as total IgE and Phadiatop, and of specific IgE antibodies to mites and molds in development of adult-onset asthma.

METHODS

A population-based incident case-control study was conducted in the Pirkanmaa District in Southern Finland. All new clinically diagnosed cases of asthma 21-63 years of age were recruited 1997-2000 in the study district. A random sample of the source population formed the controls. A total of 485 cases and 665 controls provided a serum sample. Diagnosis of asthma was based on demonstration of reversibility in lung function investigations. Subjects with previous asthma were excluded. Phadiatop score and IgE antibodies were analyzed with the UniCAP system.

RESULTS

The adjusted odds ratio of asthma increased with total IgE and Phadiatop score in a dose-dependent pattern. IgE antibodies to house dust mite and storage mite were significantly related to an increased risk of asthma. Among molds, increased risk of asthma was seen in relation to IgE antibodies to Aspergillus fumigatus and Cladosporium herbarum. Population attributable fraction due to sensitization to common aeroallergens was 30% (95% CI, 23-41).

CONCLUSION

Atopy is a strong determinant of asthma in adulthood. Specific IgE antibodies to mites and some molds are significantly related to increased risk of adult-onset asthma. A considerable fraction of adult asthma could be prevented by measures to reduce atopy.

Early childhood environment related to microbial exposure and the occurrence of atopic disease at school age

BACKGROUND

There is a growing body of evidence that the early childhood environment with respect to day care attendance, older siblings, pet ownership, and early life airway infections may protect from developing atopic disease. Few studies have distinguished between atopic sensitization and symptoms, and none have evaluated independent contributions for all of these different environmental conditions.

OBJECTIVE

Examine independent effects on atopic sensitization and symptoms of day care attendance, older siblings, pet ownership, and early infancy's airway disease.

METHODS

A cross-sectional survey among 8-13-year-old school children with complete data for 1555 children.

RESULTS

After adjustment for confounders, atopic sensitization occurred less frequently in children that had attended a day care centre (OR: 0.73, 95% CI: 0.55-0.98) or had a cat or dog before 2 years of age (OR: 0.78, 95% CI: 0.61-0.99). Having older siblings yielded a nonsignificant trend towards protection (OR: 0.88, 95% CI: 0.70-1.11). For symptoms, there was no relation with having older sibs, day care attendance and pet ownership, although there was a trend towards protection for the combination of atopy and symptoms. In contrast, children with doctors' treated airway disease before age 2, more frequently reported recent symptoms of wheeze, asthma, rhinitis, or dermatitis (all P < 0.05).

CONCLUSION

Early life environmental exposure to day care, or pets may protect against atopic sensitization. Protection against symptoms only occurred if atopic sensitization was present as well.

Characterization of recombinant respiratory syncytial viruses with the region responsible for type 2 T-cell responses and pulmonary eosinophilia deleted from the attachment (G) protein

It is essential that preventative vaccines for respiratory syncytial virus (RSV) elicit balanced T-cell responses. Immune responses dominated by type 2 T cells against RSV antigens are believed to cause exaggerated respiratory tract disease and may also contribute to unwanted inflammation in the airways that predisposes infants to wheeze through adolescence. Here we report on the construction and characterization of recombinant RSV (rRSV) strains with amino acids 151 to 221 or 178 to 219 of the attachment (G) glycoprotein deleted (rA2cpDeltaG150-222 or rA2cpDeltaG177-220, respectively). The central ectodomain was chosen for modification because a peptide spanning amino acids 149 to 200 of G protein has recently been shown to prime several strains of naïve inbred mice for polarized type 2 T-cell responses, and peripheral blood T cells from most human donors recognize epitopes within this region. Quantitative PCR demonstrated that synthesis of nascent rRSV genomes in human lung epithelial cell lines was similar to that for the parent virus (cp-RSV). Plaque assays further indicated that rRSV replication was not sensitive to 37 degrees C, but pinpoint morphology was observed at 39 degrees C. Both rRSV strains replicated in the respiratory tracts of BALB/c mice and elicited serum neutralization and anti-F-protein immunoglobulin G titers that were equivalent to those elicited by cp-RSV and contributed to a 3.9-log(10)-unit reduction in RSV A2 levels 4 days after challenge. Importantly, pulmonary eosinophilia was significantly diminished in BALB/c mice primed with native G protein and challenged with either rA2cpDeltaG150-222 or rA2cpDeltaG177-220. These findings are important for the development of attenuated RSV vaccines.

Characterisation of atopic and non-atopic wheeze in 10 year old children

BACKGROUND

Wheezing occurs in both atopic and non-atopic children. The characteristics of atopic and non-atopic wheeze in children at 10 years of age were assessed and attempts made to identify whether different mechanisms underlie these states.

METHODS

Children were seen at birth and at 1, 2, 4 and 10 years of age in a whole population birth cohort study (n = 1456; 1373 seen at 10 years). Information was collected prospectively on inherited and early life environmental risk factors for wheezing. Skin prick testing, spirometry, and methacholine bronchial challenge were conducted at 10 years. Wheezing at 10 years of age was considered atopic or non-atopic depending on the results of the skin prick test. Independent significant risk factors for atopic and non-atopic wheeze were determined by logistic regression.

RESULTS

Atopic (10.9%) and non-atopic (9.7%) wheeze were equally common at 10 years of age. Greater bronchial hyperresponsiveness (p<0.001) and airways obstruction (p = 0.011) occurred in children with atopic wheeze than in those with non-atopic wheeze at 10 years. Children with atopic wheeze more often received treatment (p<0.001) or an asthma diagnosis for their disorder, although current morbidity at 10 years differed little for these states. Maternal asthma and recurrent chest infections at 2 years were independently significant factors for developing non-atopic wheeze. For atopic wheeze, sibling asthma, eczema at 1 year, rhinitis at 4 years, and male sex were independently significant.

CONCLUSIONS

Non-atopic wheeze is as common as atopic wheeze in children aged 10 years, but treatment is more frequent in those with atopic wheeze. Different risk factor profiles appear relevant to the presence of atopic and non-atopic wheeze at 10 years of age.

Immune response to hepatitis B vaccine in asthmatic children

Asthma is a disease that demonstrates chronic Th2 lymphocyte-mediated pulmonary inflammation. We hypothesized that cytokines produced by asthmatic lung inflammation bias the immune response to antigens administered systemically toward a Th2 response, as assessed by serum IgE antibody and lymphocyte-secreted IL-4 and IL-5. We also hypothesized that treatment of asthmatic children with local anti-inflammatory agents reduces this cytokine-mediated Th2 influence. We systemically immunized groups of asthmatic children (n=29) who were participating in a long-term, randomized, placebo-controlled clinical trial of inhaled anti-inflammatory therapy (Childhood Asthma Management Program) and nonasthmatic children (n=12) with hepatitis B (Hep B) antigen, and examined their antigen-specific antibody and lymphocyte cytokine secretion profiles. The asthmatic population demonstrated an increased amount of Th2-mediated serum IgE anti-Hep B antibody, as compared to nonasthmatic children; but comparable amounts of IgG1, IgG2, IgG3, IgA, and IgM anti-Hep B antibody and lymphocyte IFNgamma, IL4, and IL5. There was no significant difference of antibody isotype or cytokine production between asthmatic subjects receiving treatment with budesonide or nedocromil, as compared to placebo. In conclusion, there is a subtle bias in responses to systemic immunization in children with asthma, but anti-inflammatory therapy does not affect this bias. The findings support the concept that the Th2 bias may be largely genetic. Importantly, we confirmed that children with asthma, including even those on inhaled corticosteroids, responded to Hep B immunization as well as did nonasthmatic children with the major isotypes of anti-Hep B antibody, suggesting that vaccine protection against hepatitis B is not influenced by inhaled steroid therapy.

Recall helper T cell response: T helper 1 cell-resistant allergic susceptibility without biasing uncommitted CD4 T cells

Effector and memory T lymphocytes differ significantly, and there is no experimental evidence that memory cells are sufficient to render an otherwise normal individual susceptible to localized allergic inflammation. Furthermore, nothing is known about the kinetics of memory responses after inhalation of antigen or interplay between an allergen-specific memory helper T (Th) cell Th2 population and uncommitted or competing Th1 cells. To study these processes, T cell receptor-transgenic CD4(+) effector cells were generated in vitro, transferred into naive recipients, and allowed to resume a quiescent state. Inhalation of protein antigen reactivated these Ag-specific Th2 donor cells, leading to allergic pulmonary inflammation and airway hyperreactivity. Susceptibility was correlated with the size of the input Th2 population, but Th1 cells neither enhanced nor reduced inflammation in this model. Importantly, the reactivation of these antigen-experienced cells by inhaled antigen did not skew the cytokine balance of recipient-derived T cells recruited to the lung nor did it inhibit the development of donor-derived Th1 cells from uncommitted antigen-experienced cells that form a normal part of immune responses. These data indicate that a quiescent memory Th2-cell population can create susceptibility to allergic pulmonary inflammation in a manner refractory to inhibition by Th1 cells or endogenous inhibitory mechanisms.

ISAAC-based asthma and atopic symptoms among Ha Noi school children

Childhood asthma and atopy prevalence patterns in the developing world are only beginning to be defined. No such information exists for Vietnam. Estimates would assist in anticipating health service needs as well as add to the growing database on global patterns of atopy. To estimate the prevalence of atopic symptoms in school children in Ha Noi, Vietnam, a cross-sectional survey was conducted of children aged 5- to 11-years-old in two schools using the parent self-administered International Study of Asthma and Allergies in Childhood (ISAAC) questionnaire. The response rate was 66.4% (969 responses). The overall prevalence of selected symptoms were: 'ever wheezed' 24.9%, 'wheezed in past 12 months' 14.9%, 'ever had asthma' 12.1%, 'doctor-diagnosed asthma' 13.9%, 'ever experienced allergic rhinitis (AR) symptoms' 34.9%, 'AR-conjunctivitis symptoms in past 12 months' 10.7%, 'ever had hay fever' 7.8%, 'doctor-diagnosed hay fever' 11.2%, 'ever had eczema' 3.3% and 'doctor-diagnosed eczema' 3.2%. Kappa statistics demonstrated high within symptom category consistency for 'ever had asthma/doctor-diagnosed asthma' (0.728) and 'ever had eczema/doctor-diagnosed eczema' (0.906). Age and gender adjusted odds ratios (OR) were also consistently significant across wheeze and allergic rhinitis symptom categories [highest OR = 10.10 (95% CI 6.23-16.35) between allergic rhinoconjunctivitis and wheeze in past 12 months]. There is a high prevalence of ISAAC-based symptoms in school children in Ha Noi, Vietnam, often above global averages. The high level of association between atopic symptoms suggests some degree of reliability and validity. Childhood atopy symptom prevalence in Vietnam is more similar to that in developed countries rather than developing countries.

Enhanced calcium signaling to bradykinin in airway smooth muscle from hyperresponsive inbred rats

Inbred Fischer 344 rats display airway hyperresponsiveness (AHR) in vivo compared with the normoresponsive Lewis strain. Fischer AHR has been linked with increased airway smooth muscle (ASM) contraction ex vivo and enhanced ASM cell intracellular Ca(2+) mobilization in response to serotonin compared with Lewis. To determine the generality of this association, we tested whether bradykinin (BK) also stimulates greater contraction of Fischer airways and greater Ca(2+) mobilization in Fischer ASM cells. Explants of Fischer intraparenchymal airways constricted faster and to a greater degree in response to BK than Lewis airways. BK also evoked higher Ca(2+) transients in Fischer than in Lewis ASM cells. ASM cell B(2) receptor expression was similar between the two strains. BK activated both phosphatidylinositide-specific phospholipase C (PI-PLC) and phosphatidylcholine-specific PLC to mobilize Ca(2+) in Fischer and Lewis ASM cells. PI-PLC activity, as measured by inositol polyphosphate accumulation, was similar in the two strains. PKC inhibition with GF109203X, Go6973, or Go6983 attenuated BK-mediated Ca(2+) transients in Fischer cells, whereas GF109203X potentiated while Go6976 and Go6983 did not affect Ca(2+) transients in Lewis cells. Enhanced Ca(2+) mobilization in ASM cells can arise from variations in PKC and may be an important component of nonspecific, innate AHR.

Influence of lipopolysaccharide exposure on airway function and allergic responses in developing mice

Exposure to endotoxin has been associated with an exacerbation of asthmatic responses in humans and animal models. However, recent evidence suggests that microbial exposure in early life may protect from the development of asthma and atopy. In this study, we sought to evaluate the effects of lipopolysaccaride (LPS) on airway function in developing mice. In addition, we evaluated the influence of LPS on subsequent allergen sensitization and challenge. Under light anesthesia, 2-3-week-old Balb/c mice received a single intranasal instillation of LPS or sterile physiologic saline. Measurements of airway function were obtained in unrestrained animals, using whole-body plethysmography. Airway responsiveness was expressed in terms of % enhanced pause (Penh) increase from baseline to aerosolized methacholine (Mch). In additional studies, we assessed the functional and cellular responses to ovalbumin sensitization and challenge following prior exposure to LPS. We found that exposure to LPS induced transient airway hyperresponsiveness to Mch. These functional changes were associated with the recruitment of neutrophils and lymphocytes into the bronchoalveolar lavage (BAL) fluid. Airway responsiveness after allergen sensitization and challenge was decreased by prior exposure to LPS. The analysis of BAL cells and cytokines (interferon-gamma and interleukin-4) did not reveal alterations in the overall Th1/Th2 balance. Our findings suggest that LPS leads to airway hyperresponsiveness in developing mice, and may protect against the development of allergen-driven airway dysfunction.

Serving the underserved: school-based asthma intervention programs

Asthma is a common and costly disease, which disproportionately affects young, ethnic minority, and impoverished individuals. A heightened public awareness has catalyzed a variety of efforts to reduce the impact of childhood asthma in the United States. Despite these efforts, however, at-risk groups continue to suffer excess morbidity. Strategies are required that can specifically address the needs of underserved communities. We review the underlying rationale and progress of school-based programs designed to assist asthmatic children.

Issues in understanding pediatric asthma: epidemiology and genetics

Asthma is a heterogeneous disease characterized by varying phenotypes. Ongoing research is focused on identifying which children who have wheezing early will progress to childhood asthma. Genetic factors, predominantly atopy and a parental history of asthma as well as environmental stimuli, are key components in the development of asthma. Investigation into immunologic processes indicates that atopic children may have a cytokine imbalance or dysregulation in which the transition from T helper 2 (T(H)2)-type to T(H)1-type immunity is delayed. Several risk factors have been identified in the pathophysiology of asthma, including sensitization and exposure to cockroaches, house dust mites, and the mold Alternaria alternata, among other aeroallergens. Viral respiratory infections, primarily those caused by respiratory syncytial virus, are a significant risk factor for the development of childhood wheezing in the first decade of life. A number of prospective epidemiologic studies are investigating, among other issues, the relations among cytokine dysregulation, respiratory tract infections, and allergen exposure and sensitization in the development of asthma. Identifying the pathogenic mechanisms should enable clinicians to identify children at high risk and thereby to treat childhood asthma more effectively.