Severity Of Allergic Airway Disease Research Articles

Multigenerational Epigenetic Regulation of Allergic Diseases: Utilizing an Experimental Dust Mite-Induced Asthma Model.

Environmental exposures have been linked to increased asthma risk, particularly during pregnancy and in early life. Here we use a mouse model of allergic lung disease to examine the effects of pre- and perinatal house dust mite (HDM) allergen exposure on offspring phenotypic and transcriptional outcomes in three generations. We show that maternal HDM exposure (F0) acts synergistically with adult HDM exposure, leading to enhanced airway hyperresponsiveness (AHR) and lung inflammation when compared to mice exposed solely in adulthood. Additionally, a subset of F1 males were not challenged in adulthood, and used to generate F2 progeny, which was then used to generate F3 progeny. Upon adult challenge to HDM, F2, and F3 males generated from the maternal HDM (F0) exposure lineage displayed increased airway reactivity and inflammation when compared to mice exposed solely in adulthood. These findings indicate that maternal allergen exposure is capable of enhancing either susceptibly to or severity of allergic airway disease. To examine the role of epigenetic inheritance of asthma susceptibility induced by maternal HDM exposure, we utilized a genome-wide MeDIP-seq and hMeDIP-seq analysis to identify genes differentially methylated (DMG) and hydroxymethylated (DHG), and their association with the enhanced AHR. In addition, we validated the relationship between DNA methylation and mRNA expression of the DMGs and DHGs in the male sub-generations (F1-F3). We found the expression of Kchn1, Nron, and Spag17 to be differentially hydroxymethylated and upregulated in the F1 exposed to HDM both in early life and in adulthood when compared to F1 mice exposed solely in adulthood. Kcnh1 remained upregulated in the F2 and F3 from the maternal HDM (F0) exposure lineage, when compared to F1 mice exposed solely in adulthood. In summary, we demonstrated that maternal HDM exposure in early life can alter the gene expression and phenotype of offspring upon adult HDM exposure, resulting in more severe disease. These effects persist at least two generations past the initial insult, transmitted along the paternal line.

Nasal upregulation of CST1 in dog-sensitised children with severe allergic airway disease.

The clinical presentation of children sensitised to dog dander varies from asymptomatic to severe allergic airway disease, but the genetic mechanisms underlying these differences are not clear. The objective of the present study was to investigate nasal transcriptomic profiles associated with dog dander sensitisation in school children and to reveal clinical symptoms related with these profiles. RNA was extracted from nasal epithelial cell brushings of children sensitised to dog dander and healthy controls. Blood sample analyses included IgE against dog dander, dog allergen molecules, other airborne and food allergens, basophil activation and white blood cell counts. Clinical history of asthma and rhinitis was recorded, and lung function was assessed (spirometry, methacholine provocation and exhaled nitric oxide fraction). The most overexpressed gene in children sensitised to dog dander compared to healthy controls was CST1, coding for Cystatin 1. A cluster of these children with enhanced CST1 expression showed lower forced expiratory volume in 1 s, increased bronchial hyperreactivity, pronounced eosinophilia and higher basophil allergen threshold sensitivity compared with other children sensitised to dog dander. In addition, multi-sensitisation to lipocalins was more common in this group. Overexpression of CST1 is associated with more severe allergic airway disease in children sensitised to dog dander. CST1 is thus a possible biomarker of the severity of allergic airway disease and a possible therapeutic target for the future treatment of airborne allergy.

Fungi in Mucoobstructive Airway Diseases

Asthma, chronic rhinosinusitis, and related incurable allergic afflictions of the upper and lower airways are medically important because of their association with the disabling symptom of dyspnea and, at least for asthma, the potential to cause fatal asphyxiation. Extensive research over the past two decades has uncovered both the physiological basis of airway obstruction in asthma and key governing molecular pathways. Exaggerated airway constriction in response to diverse provocative stimuli, termed airway hyperresponsiveness, is mediated through the cytokines interleukin 4 (IL-4) and IL-13 and the transcription factor signal transducer and activator of transcription 6 (STAT6). Overproduction of mucus has long been known to be an essential second component of airway obstruction and is also mediated in part through the IL-4/IL-13/STAT6 pathway. In this review, we discuss a second major signaling pathway which underlies mucus production that is mediated through proteinase-cleaved fibrinogen signaling through Toll-like receptor 4. Unexpectedly, our analysis of human sputum and paranasal sinus fluid indicates that in most cases of severe allergic airway disease, a unique type of airway fungal infection, termed airway mycosis, is pathogenically linked to these conditions. We further discuss how fungal and endogenous proteinases mediate the fibrinogenolysis that is essential to both Toll-like receptor 4 signaling and fibrin deposition that, together with mucus, contribute to airway obstruction.

Expansion of commensal fungus Wallemia mellicola in the gastrointestinal mycobiota enhances the severity of allergic airway disease in mice.

The gastrointestinal microbiota influences immune function throughout the body. The gut-lung axis refers to the concept that alterations of gut commensal microorganisms can have a distant effect on immune function in the lung. Overgrowth of intestinal Candida albicans has been previously observed to exacerbate allergic airways disease in mice, but whether subtler changes in intestinal fungal microbiota can affect allergic airways disease is less clear. In this study we have investigated the effects of the population expansion of commensal fungus Wallemia mellicola without overgrowth of the total fungal community. Wallemia spp. are commonly found as a minor component of the commensal gastrointestinal mycobiota in both humans and mice. Mice with an unaltered gut microbiota community resist population expansion when gavaged with W. mellicola; however, transient antibiotic depletion of gut microbiota creates a window of opportunity for expansion of W. mellicola following delivery of live spores to the gastrointestinal tract. This phenomenon is not universal as other commensal fungi (Aspergillus amstelodami, Epicoccum nigrum) do not expand when delivered to mice with antibiotic-depleted microbiota. Mice with Wallemia-expanded gut mycobiota experienced altered pulmonary immune responses to inhaled aeroallergens. Specifically, after induction of allergic airways disease with intratracheal house dust mite (HDM) antigen, mice demonstrated enhanced eosinophilic airway infiltration, airway hyperresponsiveness (AHR) to methacholine challenge, goblet cell hyperplasia, elevated bronchoalveolar lavage IL-5, and enhanced serum HDM IgG1. This phenomenon occurred with no detectable Wallemia in the lung. Targeted amplicon sequencing analysis of the gastrointestinal mycobiota revealed that expansion of W. mellicola in the gut was associated with additional alterations of bacterial and fungal commensal communities. We therefore colonized fungus-free Altered Schaedler Flora (ASF) mice with W. mellicola. ASF mice colonized with W. mellicola experienced enhanced severity of allergic airways disease compared to fungus-free control ASF mice without changes in bacterial community composition.

House Dust Mite-Induced Allergic Airway Disease Is Independent of IgE and FcεRIα.

IgE contributes to disease exacerbations but not to baseline airway hyperresponsiveness (AHR) in human asthma. In rodent allergic airway disease (AAD), mast cell and IgE dependence for the induction of AHR has only been observed when mice are immunized with a relatively weak allergen without adjuvant. To evaluate the role of IgE in murine AAD that is induced by a potent allergen, we inoculated BALB/c and FVB/N background wild-type and IgE- or FcεRIα-deficient mice intratracheally with large or limiting doses of house dust mite extract (HDM) and evaluated AHR, pulmonary eosinophilia, goblet cell metaplasia, serum IgE, and lung mastocytosis. We found that neither IgE nor FcεRIα contributed to AAD, even in mice inoculated with the lowest dose of HDM, which readily induced detectable disease, but did not increase serum IgE or pulmonary mast cell levels. In contrast, high doses of HDM strikingly increased serum IgE and pulmonary mast cells, although both AHR and airway mast cell degranulation were equally elevated in wild-type and IgE-deficient mice. Surprisingly, allergen challenge of mice with severe AAD and pulmonary mastocytosis failed to acutely increase airway resistance, lung Newtonian resistance, or hysteresis. Overall, this study shows that, although mice may not reliably model acute asthma exacerbations, mechanisms that are IgE and FcεRIα independent are responsible for AHR and airway inflammation when low doses of a potent allergen are inhaled repetitively.

Programmed Death Ligand 1 Promotes Early-Life Chlamydia Respiratory Infection-Induced Severe Allergic Airway Disease.

Chlamydia infections are frequent causes of respiratory illness, particularly pneumonia in infants, and are linked to permanent reductions in lung function and the induction of asthma. However, the immune responses that protect against early-life infection and the mechanisms that lead to chronic lung disease are incompletely understood. In the current study, we investigated the role of programmed death (PD)-1 and its ligands PD-L1 and PD-L2 in promoting early-life Chlamydia respiratory infection, and infection-induced airway hyperresponsiveness (AHR) and severe allergic airway disease in later life. Infection increased PD-1 and PD-L1, but not PD-L2, mRNA expression in the lung. Flow cytometric analysis of whole lung homogenates identified monocytes, dendritic cells, CD4(+), and CD8(+) T cells as major sources of PD-1 and PD-L1. Inhibition of PD-1 and PD-L1, but not PD-L2, during infection ablated infection-induced AHR in later life. Given that PD-L1 was the most highly up-regulated and its targeting prevented infection-induced AHR, subsequent analyses focused on this ligand. Inhibition of PD-L1 had no effect on Chlamydia load but suppressed infection-induced pulmonary inflammation. Infection decreased the levels of the IL-13 decoy receptor in the lung, which were restored to baseline levels by inhibition of PD-L1. Finally, inhibition of PD-L1 during infection prevented subsequent infection-induced severe allergic airways disease in later life by decreasing IL-13 levels, Gob-5 expression, mucus production, and AHR. Thus, early-life Chlamydia respiratory infection-induced PD-L1 promotes severe inflammation during infection, permanent reductions in lung function, and the development of more severe allergic airway disease in later life.

In Utero Cigarette Smoke Affects Allergic Airway Disease But Does Not Alter the Lung Methylome.

Prenatal and postnatal cigarette smoke exposure enhances the risk of developing asthma. Despite this as well as other smoking related risks, 11% of women still smoke during pregnancy. We hypothesized that cigarette smoke exposure during prenatal development generates long lasting differential methylation altering transcriptional activity that correlates with disease. In a house dust mite (HDM) model of allergic airway disease, we measured airway hyperresponsiveness (AHR) and airway inflammation between mice exposed prenatally to cigarette smoke (CS) or filtered air (FA). DNA methylation and gene expression were then measured in lung tissue. We demonstrate that HDM-treated CS mice develop a more severe allergic airway disease compared to HDM-treated FA mice including increased AHR and airway inflammation. While DNA methylation changes between the two HDM-treated groups failed to reach genome-wide significance, 99 DMRs had an uncorrected p-value < 0.001. 6 of these 99 DMRs were selected for validation, based on the immune function of adjacent genes, and only 2 of the 6 DMRs confirmed the bisulfite sequencing data. Additionally, genes near these 6 DMRs (Lif, Il27ra, Tle4, Ptk7, Nfatc2, and Runx3) are differentially expressed between HDM-treated CS mice and HDM-treated FA mice. Our findings confirm that prenatal exposure to cigarette smoke is sufficient to modify allergic airway disease; however, it is unlikely that specific methylation changes account for the exposure-response relationship. These findings highlight the important role in utero cigarette smoke exposure plays in the development of allergic airway disease.

Phase-contrast computed tomography for quantification of structural changes in lungs of asthma mouse models of different severity.

Lung imaging in mouse disease models is crucial for the assessment of the severity of airway disease but remains challenging due to the small size and the high porosity of the organ. Synchrotron inline free-propagation phase-contrast computed tomography (CT) with its intrinsic high soft-tissue contrast provides the necessary sensitivity and spatial resolution to analyse the mouse lung structure in great detail. Here, this technique has been applied in combination with single-distance phase retrieval to quantify alterations of the lung structure in experimental asthma mouse models of different severity. In order to mimic an in vivo situation as close as possible, the lungs were inflated with air at a constant physiological pressure. Entire mice were embedded in agarose gel and imaged using inline free-propagation phase-contrast CT at the SYRMEP beamline (Synchrotron Light Source, `Elettra', Trieste, Italy). The quantification of the obtained phase-contrast CT data sets revealed an increasing lung soft-tissue content in mice correlating with the degree of the severity of experimental allergic airways disease. In this way, it was possible to successfully discriminate between healthy controls and mice with either mild or severe allergic airway disease. It is believed that this approach may have the potential to evaluate the efficacy of novel therapeutic strategies that target airway remodelling processes in asthma.

Long-Term Exposure to House Dust Mite Leads to the Suppression of Allergic Airway Disease Despite Persistent Lung Inflammation

Background: Allergic asthma is a major cause of worldwide morbidity and results from inadequate immune regulation in response to innocuous, environmental antigens. The need exists to understand the mechanisms that promote nonreactivity to human-relevant allergens such as house dust mite (HDM) in order to develop curative therapies for asthma. The aim of our study was to compare the effects of short-, intermediate- and long-term HDM administration in a murine asthma model and determine the ability of long-term HDM exposure to suppress allergic inflammation. Methods: C57BL/6 mice were intranasally instilled with HDM for short-term (2 weeks), intermediate-term (5 weeks) and long-term (11 weeks) periods to induce allergic airway disease (AAD). The severity of AAD was compared across all stages of the model via both immunological and pulmonary parameters. Results: Short- and intermediate-term HDM exposure stimulated the development of AAD that included eosinophilia in the bronchoalveolar lavage fluid (BALF), pronounced airway hyperreactivity (AHR) and evidence of lung inflammation. Long-term HDM exposure promoted the suppression of AAD, with a loss of BALF eosinophilia and AHR despite persistent mononuclear inflammation in the lungs. Suppression of AAD with long-term HDM exposure was associated with an increase in both Foxp3+ regulatory T cells and IL-10-positive alveolar macrophages at the site of inflammation. Conclusions: This model recapitulates the key features of human asthma and may facilitate investigation into the mechanisms that promote immunological tolerance against clinically relevant aeroallergens.

Pulmonary immunity during respiratory infections in early life and the development of severe asthma.

Asthma affects 10% of the population in Westernized countries, being most common in children. It is a heterogeneous condition characterized by chronic allergic airway inflammation, mucus hypersecretion, and airway hyperresponsiveness (AHR) to normally innocuous antigens. Combination therapies with inhaled corticosteroids and bronchodilators effectively manage mild to moderate asthma, but there are no cures, and patients with severe asthma do not respond to these treatments. The inception of asthma is linked to respiratory viral (respiratory syncytial virus, rhinovirus) and bacterial (Chlamydia, Mycoplasma) infections. The examination of mouse models of early-life infections and allergic airway disease (AAD) provides valuable insights into the mechanisms of disease inception that may lead to the development of more effective therapeutics. For example, early-life, but not adult, Chlamydia respiratory infections in mice permanently modify immunity and lung physiology. This increases the severity of AAD by promoting IL-13 expression, mucus hypersecretion, and AHR. We have identified novel roles for tumor necrosis factor-related apoptosis-inducing ligand (TRAIL) and IL-13 in promoting infection-induced pathology in early life and subsequent chronic lung disease. Genetic deletion of TRAIL or IL-13 variously protected against neonatal infection-induced inflammation, mucus hypersecretion, altered lung structure, AHR, and impaired lung function. Therapeutic neutralization of these factors prevented infection-induced severe AAD. Other novel mechanisms and avenues for intervention are also being explored. Such studies indicate the immunological mechanisms that may underpin the association between early-life respiratory infections and the development of more severe asthma and may facilitate the development of tailored preventions and treatments.

IgE and FcεRIα do not promote allergic airway disease in mice inoculated intratracheally with house dust mite extract (HYP7P.316)

Abstract The role of IgE in asthma pathogenesis is controversial. Early studies showed IgE contributed to allergic airway disease (AAD) when mice were sensitized passively by anti-ovalbumin (OVA) IgE or sensitized actively by OVA without adjuvant. Other groups found that IgE did not promote AAD that was provoked by fungal extracts or by OVA with adjuvant. We have used IgE-deficient mice and FcεRIα-deficient mice and their respective FVBN and BALB/c wild-type controls to study the IgE- and FcεRIα-dependence of AAD induced by a clinically relevant allergen and route of administration. Mice were inoculated intratracheally with house dust mite extract without adjuvant every 2 days for 7 doses. We measured airway hyperresponsiveness by both unrestrained plethysmography (Buxco) and forced oscillation (flexiVent), analyzed pulmonary inflammation by differential cell count on BALF, and sectioned lungs to quantitate goblet cell metaplasia by microscopic examination. We found no difference in any of these disease parameters between wild-type mice and gene-deficient mice, regardless of whether minimal, moderate, or more severe AAD was induced. These results complement the clinical observation that anti-IgE therapy fails to improve the underlying lung function of humans with long standing asthma, although this treatment does reduce acute exacerbations. We are currently studying the acute changes in lung function that occur upon inhalation of allergen in AAD and their dependence on the IgE axis.

The complex relationship between inflammation and lung function in severe asthma.

Asthma is a common respiratory disease affecting approximately 300 million people worldwide. Airway inflammation is thought to contribute to asthma pathogenesis, but the direct relationship between inflammation and airway hyperresponsiveness remains unclear. This study investigates the role of inflammation in a steroid-insensitive, severe allergic airway disease model and in severe asthmatics stratified by inflammatory profile. First, we utilized the TH17 cell adoptive transfer mouse model of asthma to induce pulmonary inflammation, which was lessened by TNFα neutralization or neutrophil depletion. While decreased airspace inflammation following TNFα neutralization and neutrophil depletion rescued lung compliance, neither intervention improved airway hyperresponsiveness to methacholine, and tissue inflammation remained elevated when compared to control. Further, sputum samples were collected and analyzed from 41 severe asthmatics. In severe asthmatics with elevated levels of sputum neutrophils, but low levels of eosinophils, increased inflammatory markers did not correlate with worsened lung function. This subset of asthmatics also had significantly higher levels of TH17-related cytokines in their sputum compared to other severe asthmatics with other inflammatory phenotypes. Overall, this work suggests that lung compliance may be linked with cellular inflammation in the airspace, while T cell-driven airway hyperresponsiveness may be associated with tissue inflammation and other pulmonary factors.

Severity of Allergic Airway Disease Due to House Dust Mite Allergen Is Not Increased after Clinical Recovery of Lung Infection with Chlamydia pneumoniae in Mice

Chlamydia pneumoniae is associated with chronic inflammatory lung diseases like bronchial asthma and chronic obstructive pulmonary disease. The existence of a causal link between allergic airway disease and C. pneumoniae is controversial. A mouse model was used to address the question of whether preceding C. pneumoniae lung infection and recovery modifies the outcome of experimental allergic asthma after subsequent sensitization with house dust mite (HDM) allergen. After intranasal infection, BALB/c mice suffered from pneumonia characterized by an increased clinical score, reduction of body weight, histopathology, and a bacterial load in the lungs. After 4 weeks, when infection had almost resolved clinically, HDM allergen sensitization was performed for another 4 weeks. Subsequently, mice were subjected to a methacholine hyperresponsiveness test and sacrificed for further analyses. As expected, after 8 weeks, C. pneumoniae-specific antibodies were detectable only in infected mice and the titer was significantly higher in the C. pneumoniae/HDM allergen-treated group than in the C. pneumoniae/NaCl group. Intriguingly, airway hyperresponsiveness and eosinophilia in bronchoalveolar lavage fluid were significantly lower in the C. pneumoniae/HDM allergen-treated group than in the mock/HDM allergen-treated group. We did observe a relationship between experimental asthma and chlamydial infection. Our results demonstrate an influence of sensitization to HDM allergen on the development of a humoral antibacterial response. However, our model demonstrates no increase in the severity of experimental asthma to HDM allergen as a physiological allergen after clinically resolved severe chlamydial lung infection. Our results rather suggest that allergic airway disease and concomitant cellular changes in mice are decreased following C. pneumoniae lung infection in this setting.

Stress: A Possible Link between Genetics, Epigenetics, and Childhood Asthma

Stress: A Possible Link between Genetics, Epigenetics, and Childhood Asthma

Constitutive production of IL-13 promotes early-life Chlamydia respiratory infection and allergic airway disease.

Deleterious responses to pathogens during infancy may contribute to infection and associated asthma. Chlamydia respiratory infections in early life are common causes of pneumonia and lead to reduced lung function and asthma. We investigated the role of interleukin-13 (IL-13) in promoting early-life Chlamydia respiratory infection, infection-induced airway hyperresponsiveness (AHR), and severe allergic airway disease (AAD). Infected infant Il13(-/-) mice had reduced infection, inflammation, and mucus-secreting cell hyperplasia. Surprisingly, infection of wild-type (WT) mice did not increase IL-13 production but reduced IL-13Rα2 decoy receptor levels compared with sham-inoculated controls. Infection of WT but not Il13(-/-) mice induced persistent AHR. Infection and associated pathology were restored in infected Il13(-/-) mice by reconstitution with IL-13. Stat6(-/-) mice were also largely protected. Neutralization of IL-13 during infection prevented subsequent infection-induced severe AAD. Thus, early-life Chlamydia respiratory infection reduces IL-13Rα2 production, which may enhance the effects of constitutive IL-13 and promote more severe infection, persistent AHR, and AAD.

Antibodies Generated against Conserved Antigens Expressed by Bacteria and Allergen-Bearing Fungi Suppress Airway Disease

There has been a sharp rise in allergic asthma and asthma-related deaths in the developed world, in contrast to many childhood illnesses that have been reduced or eliminated. The hygiene hypothesis proposes that excessively sanitary conditions early in life result in autoimmune and allergic phenomena because of a failure of the immune system to receive proper microbial stimulation during development. We demonstrate that Abs generated against conserved bacterial polysaccharides are reactive with and dampen the immune response against chitin and Aspergillus fumigatus. A reduction in Ag uptake, cell influx, cell activation, and cytokine production occurred in the presence of anti-polysaccharide Abs, resulting in a striking decrease in the severity of allergic airway disease in mice. Overall, our results suggest that Ag exposure--derived from environmental sources, self-antigens, or vaccination--during the neonatal period has dramatic effects on the adult Ab response and modifies the development of allergic airway disease.

Chlamydia muridarum Lung Infection in Infants Alters Hematopoietic Cells to Promote Allergic Airway Disease in Mice

BackgroundViral and bacterial respiratory tract infections in early-life are linked to the development of allergic airway inflammation and asthma. However, the mechanisms involved are not well understood. We have previously shown that neonatal and infant, but not adult, chlamydial lung infections in mice permanently alter inflammatory phenotype and physiology to increase the severity of allergic airway disease by increasing lung interleukin (IL)-13 expression, mucus hyper-secretion and airway hyper-responsiveness. This occurred through different mechanisms with infection at different ages. Neonatal infection suppressed inflammatory responses but enhanced systemic dendritic cell:T-cell IL-13 release and induced permanent alterations in lung structure (i.e., increased the size of alveoli). Infant infection enhanced inflammatory responses but had no effect on lung structure. Here we investigated the role of hematopoietic cells in these processes using bone marrow chimera studies.Methodology/Principal FindingsNeonatal (<24-hours-old), infant (3-weeks-old) and adult (6-weeks-old) mice were infected with C. muridarum. Nine weeks after infection bone marrow was collected and transferred into recipient age-matched irradiated naïve mice. Allergic airway disease was induced (8 weeks after adoptive transfer) by sensitization and challenge with ovalbumin. Reconstitution of irradiated naïve mice with bone marrow from mice infected as neonates resulted in the suppression of the hallmark features of allergic airway disease including mucus hyper-secretion and airway hyper-responsiveness, which was associated with decreased IL-13 levels in the lung. In stark contrast, reconstitution with bone marrow from mice infected as infants increased the severity of allergic airway disease by increasing T helper type-2 cell cytokine release (IL-5 and IL-13), mucus hyper-secretion, airway hyper-responsiveness and IL-13 levels in the lung. Reconstitution with bone marrow from infected adult mice had no effects.ConclusionsThese results suggest that an infant chlamydial lung infection results in long lasting alterations in hematopoietic cells that increases the severity of allergic airway disease in later-life.

Antibodies generated against conserved antigens suppress allergic airway disease (125.13)

Abstract There has been a sharp rise in allergic asthma and asthma-related deaths in the developed world. The hygiene hypothesis proposes that excessively sanitary conditions early in life result in autoimmune and allergic phenomena because of a failure of the immune system to receive proper microbial stimulation during development. Chitin, a biopolymer of N-acetyl glucosamine (GlcNAc), is produced by many allergen-bearing organisms including: fungi, the exoskeleton of insects, crabs, shrimp and parasitic nematodes. We demonstrate that antibodies generated against chitin and other conserved bacterial polysaccharides, induced by neonatal vaccination or passive transfer, are reactive with and dampen the immune response against chitin and Aspergillus fumigatus. In the presence of anti-polysaccharide antibodies, we observed a marked reduction in antigen uptake, cell influx, cellular activation, and cytokine production, resulting in a striking decrease in the severity of allergic airway disease in mice. Our results suggest that antigen exposure, during the neonatal period, from environmental sources, self-antigens, or vaccination, have dramatic effects on the adult B cell repertoire and subsequent antibody responses, modulating the immune response to potential allergens later in life and thus dampening development of allergic airway disease. We propose an adjunct hypothesis that antibodies may contribute to the mechanism of protection proposed by the hygiene hypothesis.

Early-life chlamydial lung infection enhances allergic airways disease through age-dependent differences in immunopathology

Asthma typically originates in early-life, and the impact of infection during immunologic maturation is a critical factor in disease pathogenesis. The progression of aberrant T(H)2 cell responses and disease development has been attributed to a lack of infections. However, exposure to specific pathogens such as Chlamydia may alter immunologic programming and predispose to asthma. To investigate the effects of chlamydial infection at different ages on allergic airways disease in later life. Neonatal, infant, or adult BALB/c mice were infected and 6 weeks later were sensitized and subsequently challenged with ovalbumin. Hallmark features of allergic airways disease were compared with uninfected allergic and nonallergic controls. Early-life (neonatal and infant) but not adult chlamydial infection enhanced the development of hallmark features of asthma in ovalbumin-induced allergic airways disease. Notably early-life infection increased mucus-secreting cell numbers, IL-13 expression, and airway hyperresponsiveness. Neonatal infection attenuated eosinophil influx and ovalbumin-specific T(H)2 cytokine release and numbers of activated myeloid dendritic cells (DCs) in lymph nodes. By contrast, infant infection augmented features of allergic inflammation with increased airway eosinophils, T(H)2 cytokine, and DC responses. Both neonatal and infant infection increased systemic DC-induced IL-13 release from CD4(+) T cells. The timing of infection had significant effects on lung structure because neonatal but not infant or adult infection induced increases in alveolar diameter. Early-life respiratory chlamydial infections modulate immune responses, alter lung function and structure, and enhance the severity of allergic airways disease in later life.

The extracellular matrix protein mindin regulates trafficking of murine eosinophils into the airspace.

Asthma remains a major cause of morbidity and hospitalizations in developed nations. Despite the widespread prevalence of this disease, the genetic and environmental factors that mediate development and progression of allergic airways disease remain poorly understood. Pulmonary recruitment of eosinophils is believed to contribute to many cardinal features of allergic airways disease. Therefore, it is paramount to understand host factors that contribute to pulmonary eosinophil recruitment into the lungs. Mindin is a component of pulmonary extracellular matrix, which can regulate inflammatory cell recruitment. We characterized the role of mindin in the severity of allergic airways disease using established murine models. There were no baseline differences in wild-type and mindin-deficient animals in cell counts or airway physiology. Using the OVA murine model of allergic airways disease, we observed that mindin-deficient animals have less-severe allergic airways disease with fewer airspace eosinophils and lower lung-lavage levels of inflammatory Th2 cytokines such as IL-13 and IL-4. Furthermore, mindin-deficient animals have reduced airway hyper-responsiveness after methacholine challenge. To determine the role of mindin in eosinophil trafficking, independent of antigen immunization or T lymphocyte activation, we instilled IL-13 directly into the lungs of mice. In this model, mindin regulates eosinophil recruitment into the airspace. In vitro experiments demonstrate that mindin can enhance eotaxin-mediated eosinophil adhesion and migration, which are dependent on the expression of integrins alphaMbeta2 and alpha4beta1. In conclusion, these data suggest that mindin participates in integrin-dependent trafficking of eosinophils and can contribute to the severity of allergic airways disease.