Asthma and the hygiene hypothesis

Antenatal Dexamethasone Exposure in Preterm Infants Is Associated with Allergic Diseases and the Mental Development Index in Children

Background: Antenatal steroid administration may benefit fetal lung maturity in preterm infants. Although some studies have shown that this treatment may increase asthma in childhood, the correlation between antenatal dexamethasone exposure and allergic diseases remains unclear. The purpose of this study is to investigate the association between antenatal dexamethasone and T cell expression in childhood allergic diseases. Methods: We recruited a cohort of preterm infants born at Kaohsiung Chang Gung Memorial Hospital between 2007 and 2010 with a gestational age of less than 35 weeks and body weight at birth of less than 1500 g. The status of antenatal exposure to steroids and allergic diseases were surveyed using a modified ISAAC questionnaire for subjects aged 2-5 years old. We analyzed Th1/Th2/Th17 expression of mRNA, cytokines (using the Magpix^® my-system), and mental development index (MDI). Results: Among the 40 patients that were followed, the data showed that the antenatal dexamethasone exposure group (N = 24) had a significantly higher incidence of allergic diseases (75.0% vs. 18.8%, p < 0.0001) when compared to the non-dexamethasone exposure group (N = 16), especially with regard to asthma (41.7% vs. 0.0%, p = 0.003) and allergic rhinitis (58.3% vs. 18.8%, p = 0.013), but not atopic dermatitis. No statistical difference was observed in the mRNA expression levels of total white blood cell count between the dexamethasone exposure and non-exposure groups (p > 0.05). However, the asthma group had higher IL-5 levels (p = 0.009), and the MDI was shown to be significantly higher in the dexamethasone exposure group (90.38 ± 3.31 vs. 79.94 ± 3.58, p = 0.043) while no significant difference was found between the PDI of the two groups. Conclusions: Exposure to antenatal dexamethasone in preterm infants will increase their susceptibility to allergic diseases, particularly asthma and allergic rhinitis. Preterm infants' exposure to antenatal dexamethasone also results in higher MDI scores. Such increases in allergic diseases may be related to increased IL-5 and IL-10 levels.

Cross-fostering increases TH1/TH2 expression in a prenatal dexamethasone exposure rat model

BACKGROUND

Prenatal dexamethasone exposure has been reported to increase allergy potential in childhood possibly by interference with normal immunological development in utero. This study investigated the effects of prenatal dexamethasone on T helper cell immune responses in a rat model.

METHODS

Pregnant rats received either dexamethasone 0.1 mg/kg/day or normal saline from gestational day 14-21. Off-springs were cared for by their biological mother, or cross-fostered by the opposing group. Spleen and blood samples were collected at post-natal day 7 and 120 and tested for mRNA expression and plasma cytokine levels of Th1/Th2/Th17 immune response.

RESULTS

Both Th1 (T-bet) and Th2 (GATA-3) mRNA expression were shown to have a significant increase in the prenatal dexamethasone exposure group at day 120 (p<0.05). The plasma levels for Th1 (IFNγ and IL-2) and Th2 (IL-4, IL-5, IL-13) were found to have no significant differences between the two group (p>0.05). The mRNA expression of Th17 (RORγt) showed a significant decrease at post-natal day 120 as well as the plasma level of IL-17A at day 7 (11.21±1.67 vs. 6.23±1.06 pg/ml, p = 0.02). Cross-fostering by a dexamethasone exposed mother resulted in a significant increase in Th1/Th2 mRNA expression (p<0.05) and decrease of Th17.

CONCLUSIONS

Prenatal dexamethasone exposure increased Th1, Th2 and decreased Th17 expression. Cross-fostering by a dexamethasone exposed mother results in more prominent increase of Th1 and Th2 expression.

Prenatal and postnatal probiotics reduces maternal but not childhood allergic diseases: a randomized, double-blind, placebo-controlled trial

BACKGROUND

The prevalence of atopic diseases has increased rapidly in recent decades globally. The administration of probiotics to reduce gastrointestinal inflammation has been popular, but its role in the prevention or treatment of allergic disease remains controversial. This study evaluated the effectiveness of prenatal and postnatal probiotics in the prevention of early childhood and maternal allergic diseases.

METHODS

In a prospective, double-blind, placebo-controlled clinical trial, pregnant women with atopic diseases determined by history, total immunoglobulin (Ig)E > 100 kU/L, and/or positive specific IgE were assigned to receive either probiotics (Lactobacillus GG; ATCC 53103; 1 × 10(10) colony-forming units daily) or placebo from the second trimester of pregnancy. Both of clinical evaluation performed by questionnaires concerning any allergic symptoms and plasma total IgE, and allergen-specific IgE were obtained in high-risk parents and children at 0, 6, 18, and 36 months of age. The primary and secondary outcomes were the point and cumulative prevalence of sensitization and developing of allergic diseases, and improvement of maternal allergic symptom score and plasma immune parameters before and after intervention, respectively.

RESULTS

In total, 191 pregnant women (LGG group, n = 95; control group, n = 96) were enrolled. No significant effects of prenatal and postnatal probiotics supplementation on sensitization, development of allergic diseases, and maternal IgE levels between placebo and LGG groups. Symptoms of maternal allergic scores improved significantly in the LGG group (P = 0.002). Maternal allergic diseases improvement was more prominent in pregnant women with IgE > 100 kU/L (P = 0.01) and significantly associated with higher interleukin-12p70 levels (P = 0.013).

CONCLUSIONS

LGG administration beginning at the second trimester of pregnancy reduced the severity of maternal allergic disease through increment of Th1 response, but not the incidence of childhood allergic sensitization or allergic diseases (ClinicalTrials.govnumber, IDNCT00325273).

Effects of glycation of the model food allergen ovalbumin on antigen uptake and presentation by human dendritic cells

Advanced glycation endproducts (AGEs) of food proteins resulting from the Maillard reaction after cooking or heating may have particular importance in food allergy. The underlying immunological mechanisms are only poorly understood. The aim of the study was to examine the effects of AGE derived from the model food allergen ovalbumin (AGE-OVA) on dendritic cells (DCs), their immunostimulatory capacity and the T-cell response compared with regular OVA. For this purpose, human immature DCs were exposed to fluorescein isothiocyanate (FITC)-labelled AGE-OVA and FITC-labelled regular OVA and uptake was analysed by flow cytometry and fluorescence microscopy. Furthermore, autologous CD4(+) T-cell proliferation and cytokine production induced by mature DCs loaded with AGE-OVA were compared with those induced by mature DCs loaded with OVA. Finally, expression of the receptor for advanced glycation endproducts (RAGE) and activation of the transcription factor nuclear factor (NF)-kappaB by AGE were investigated. Internalization of FITC-AGE-OVA by immature DCs was significantly increased compared with FITC-OVA. Blocking the mannose receptor, macropinocytosis or the scavenger receptor strongly reduced uptake of both FITC-OVA and FITC-AGE-OVA. In a comparison of CD4(+) T cells co-cultured with AGE-OVA-loaded mature DCs versus those co-cultured with OVA-loaded mature DCs, AGE-OVA DCs were found to produce more interleukin (IL)-6 and to induce a stronger T helper type 2 (Th2) and a weaker Th1 cytokine response, while there was no difference in proliferation of CD4(+) T cells. The expression of RAGE was higher on immature DCs compared with mature DCs. AGE-OVA-exposed immature DCs showed a stronger expression of RAGE and activation of the transcription factor NF-kappaB compared with OVA-loaded immature DCs. Our data indicate that AGE-OVA may be more immunogenic/allergenic than regular OVA.

Protease-activated receptors and prostaglandins in inflammatory lung disease

Protease-activated receptors (PARs) are a novel family of G protein-coupled receptors. Signalling through PARs typically involves the cleavage of an extracellular region of the receptor by endogenous or exogenous proteases, which reveals a tethered ligand sequence capable of auto-activating the receptor. A considerable body of evidence has emerged over the past 20 years supporting a prominent role for PARs in a variety of human physiological and pathophysiological processes, and thus substantial attention has been directed towards developing drug-like molecules that activate or block PARs via non-proteolytic pathways. PARs are widely expressed within the respiratory tract, and their activation appears to exert significant modulatory influences on the level of bronchomotor tone, as well as on the inflammatory processes associated with a range of respiratory tract disorders. Nevertheless, there is debate as to whether the principal response to PAR activation is an augmentation or attenuation of airways inflammation. In this context, an important action of PAR activators may be to promote the generation and release of prostanoids, such as prostglandin E(2), which have well-established anti-inflammatory effects in the lung. In this review, we primarily focus on the relationship between PARs, prostaglandins and inflammatory processes in the lung, and highlight their potential role in selected respiratory tract disorders, including pulmonary fibrosis, asthma and chronic obstructive pulmonary disease.

Toll-like receptors and airway inflammation

The respiratory tract opens to the external environment at the oral side edge, and the other edge of the respiratory tract connects to the closed space (alveoli), and so to preserve the sterility in the terminal respiratory tract is critical for protection against pathogens. The recognition machinery for the invasion of microbes is indispensable for the preservation of the sterility in the lungs. Our general understanding of how microbes are recognized by the innate immune system has increased considerably over the past several years, and the contribution of Toll-Like Receptors (TLRs) to innate immunity is now well documented. In the meantime, it has come to understand that many inflammatory processes may depend on TLR signaling, it has been considered to be involved in the pathogenesis of airway inflammatory diseases such as airway infections, bronchial asthma, and occupational airway diseases. In this review, we focus on physiological roles of TLRs in defense mechanisms of the airways, and pathophysiological roles on airway diseases.

Trends in asthma prevalence, hospitalization risk, and inhaled corticosteroid use among alaska native and nonnative medicaid recipients younger than 20 years

BACKGROUND

Few trend data on asthma prevalence exist for U.S. indigenous populations, and none exist for Alaska Natives.

OBJECTIVE

To document the epidemiologic features of asthma in Alaska Natives and nonnatives stratified by urban (Anchorage) and rural (non-Anchorage) residence.

METHODS

We conducted a retrospective review of Alaskans younger than 20 years enrolled in Medicaid during 1999 to 2002. Asthma was defined as a claim for International Classification of Diseases, Ninth Revision, codes 493.0x to 493.9x plus asthma-associated medication during the same calendar year.

RESULTS

Among 117,080 Medicaid enrollees, the 4-year asthma prevalence was 3.1% and was 40% to 90% greater for urban residents regardless of race. Yearly prevalence increased from 1.0% to 2.2% (P < .001), with increases in all subgroups. Of 4 predominantly Alaska Native census areas, the area with resident pediatricians and previous participation in asthma research had a 4-year asthma prevalence 5- to 11-fold higher than the other areas. Among persons with asthma, yearly hospitalization risk decreased (from 9.3% to 6.8%; P = .02) concurrent with an increase in the yearly use of inhaled corticosteroids (from 50% to 64%; P < .001). Urban Alaska Natives had the greatest decrease in hospitalization risk and the greatest increase in inhaled corticosteroid use.

CONCLUSIONS

Relatively dramatic demographic differences and temporal trends in asthma prevalence occurred in the absence of known differences or changes in risk factor prevalences. This suggests a role for differences in the use of asthma as a diagnosis for respiratory illness. Failure to diagnose and thus treat asthma may affect outcomes because decreases in hospitalization risk were temporally associated with increases in inhaled corticosteroid use.

Current and emerging nonsteroidal anti-inflammatory therapies targeting specific mechanisms in asthma and allergy

Today inhaled corticosteroids (ICS) are regarded as the first-line controller anti-inflammatory treatment in the management of asthma. However, there is an increasing awareness of the risk of long-term adverse effects of ICS and that asthma is not only an organ-specific disease but also a systemic and small airway disease. This thinking has called for systemic treatment alternatives to treat asthma targeting more disease-specific mechanisms without influencing normal physiologic functions. Blocking of disease-specific mediators is a mechanism utilized by anti-leukotrienes and anti-immunoglobulin E treatment, each proven to be effective in both asthma and allergic rhinitis.Different cytokine-modifying strategies have been tested in clinical trials with variable results, some disappointing and some encouraging. Anti-interleukin (IL)-5 monoclonal antibody treatment effectively reduces the number of eosinophils locally in the airways and in peripheral blood in asthmatic patients. Unfortunately, this marked effect on eosinophils was not associated with an improvement in bronchial hyperresponsiveness and/or symptoms. Clinical trials with a recombinant soluble IL-4 receptor have been somewhat more successful at improving asthma control and allowing reduction of ICS therapy in asthma. Treatment with recombinant IL-12 had an effect on bronchial hyperresponsiveness and eosinophilic response, but was associated with unacceptable adverse effects. Other interesting cytokine-modulating treatments include those targeting IL-9, IL-10, IL-12 and IL-13.Immune-modulating treatment with bacterial antigens represents another strategy, originating from the hypothesis that some bacterial infections guide the immune system towards a T helper (Th) type 1 immune response. Mycobacterium vaccae, Bacille Calmette-Guerin (BCG) and immunostimulatory DNA sequences have all been tested in clinical trials, with encouraging results. Future asthma and allergy treatment will probably include not only one but also two or more disease-modifying agents administered to the same patient.

Interleukin-12-independent down-modulation of cockroach antigen-induced asthma in mice by intranasal exposure to bacterial lipopolysaccharide

Several studies have shown that exposure to bacterial lipopolysaccharide (LPS) can either prevent or inhibit asthma in humans and laboratory rodents. Much emphasis has been placed on the role of cytokines and chemokines in the establishment and maintenance of allergic airway disease. Therefore, it is of interest to study the role of LPS in affecting airway pathology and lung cytokine and chemokine responses in the maintenance phase of asthma. Increasing doses of LPS were administered into the airways of mice presensitized with cockroach allergen (CRAg), then allergic airway disease parameters were assessed after CRAg challenge. Airway hyperresponsiveness after antigen challenge decreased at the highest dose of LPS tested, which was accompanied by a decrease in airway and lung eosinophils. However, a dramatic increase in lung inflammation because of neutrophil influx was observed. Measurement of cytokines in lungs of LPS-treated, CRAg-sensitized mice indicated that interleukin (IL)-12 levels were increased by LPS treatment in a dose-dependent manner, as were levels of several inflammatory chemokines. In contrast, levels of IL-4, IL-13, IL-5, and IL-10 were reduced in whole lung homogenates only of high-dose LPS-treated mice. Intranasal administration of neutralizing anti-IL-12 at the time of high-dose LPS challenge reduced lung IL-12, interferon-gamma, CXCL9, and CXCL10 but did not affect levels of the other chemokines or Th2-type cytokines, and did not restore AHR. These findings suggest that the amelioration of airway hyperresponsiveness observed in LPS-treated, CRAg-sensitized mice is coincident with an immune deviation of the lung inflammatory response, independent of IL-12.

The relationships between atopy, rhinitis and asthma: pathophysiological considerations

PURPOSE OF REVIEW

A close relationship has been described between atopy, allergic rhinitis and asthma. The purpose of this work was to review recent data that have become available on the interactions between these conditions and the ways in which they influence one another.

RECENT FINDINGS

Recent findings support previous observations suggesting that atopic dermatitis and rhinitis often accompany or precede the development of asthma. Further data support the notion that early-life exposure to domestic animals, a farming environment, passive smoking, and being raised in a large family, may be protective against the development of atopy and/or allergic diseases, although this seems modulated by genetic factors. Furthermore, the appearance of house-dust-mite-specific immunoglobulin E antibodies in early childhood has been identified as a major risk factor for the development of asthma in children with atopic dermatitis; and the association between sensitization to specific allergens and airway hyperresponsiveness was reported to be the strongest for indoor allergens such as house-dust-mite and cat. Allergen exposure can increase airway responsiveness in non-asthmatic subjects with allergic rhinitis and is associated with an increase in markers of lower airway inflammation, particularly with indoor allergens. Furthermore, nasal allergen provocation can induce bronchial inflammation and vice versa, suggesting close interrelations between upper and lower airways.

SUMMARY

In summary, the recent observations on the relationships between atopy, rhinitis and asthma support the hypothesis of a unique systemic condition with variable manifestations, which may develop following an imbalance between T helper cell types 1 and 2 lymphocyte populations. The latter may be influenced by environmental exposure in early life. Upper- and lower-airway inflammatory events influence each other, supporting the concept of 'united airways'. Further studies should look at the relationships between these conditions to identify individuals at high-risk of developing them and develop strategies to possibly prevent their onset.

Early predictors of asthma

A number of recent cohort and cross-sectional studies have contributed substantial knowledge to factors that influence the early development of asthma. Here, we summarize the recent evidence for the role of early life events such as prenatal factors, infections, diet and allergen exposure, and discuss the implications for future preventative strategies.

Effects of socioeconomic status on presentation with acute lower respiratory tract disease in children in Salvador, Northeast Brazil

Two different socioeconomic groups of children with pneumonia were studied, and their clinical and demographic aspects were evaluated. The diagnosis of pneumonia was based on findings of cough and tachypnea, or on crackles on auscultation or on radiologically confirmed infiltrate. This was a prospective cross-sectional study conducted at the Professor Hosannah de Oliveira Pediatric Center, which cares for children of lower socioeconomic status (PHOPC), and at one private hospital which cares for children from middle to high socioeconomic status (Aliança Hospital, AH). Demographics and clinical differences were assessed by the Pearson chi-square test or Fisher's exact test as appropriate; means of continuous variables were compared by Mann-Whitney U-test. In a 26-month period, 3,431 cases were recruited. The 2,476 cases identified at the PHOPC were younger than the 955 identified at AH (2.2 +/- 2.3 vs. 4.5 +/- 3.1 years, P < 0.0001) and had higher scores for severity (3.5 +/- 1.5 vs. 2.7 +/- 1.7, P < 0.0001), duration of hospitalization (days) (10.9 +/- 12.1 vs. 6.2 +/- 7, P < 0.0001), frequency of tobacco smoker in the household (48% vs. 31%, P < 0.0001), cardiopathy (15.3% vs. 5.9%, P = 0.003), fever (44.4% vs. 36.3%, P = 0.0001), tachypnea (67.6% vs. 32.3%, P < 0.0001), crackles (69.5% vs. 64.9%, P = 0.02), somnolence (19.9% vs. 10.4%, P < 0.0001), malnutrition (13.7% vs. 5%, P < 0.0001), hospitalization rate (27.4% vs. 22.5%, P = 0.003), and death (0.9% vs. 0.1%, P = 0.009). However, other features were more frequent among AH cases: parent's university level of education (38.2% vs. 1.0%, P < 0.0001), underlying chronic illness (40.6% vs. 28.5%, P < 0.0001), asthma (62.7% vs. 50.8%, P = 0.01), rhinitis (9.2% vs. 0.4%, P < 0.0001), previous use of antibiotics (34.3% vs. 27.1%, P = 0.001), and wheezing (53.1% vs. 42.2%, P < 0.0001). Children of lower socioeconomic status have more serious lower respiratory tract disease, whereas children with pneumonia of middle to high socioeconomic status have more allergic diseases (rhinitis, asthma) and wheezing.