H Fehrenbach

Involvement of distal airways in a chronic model of experimental asthma.

Background Bronchial asthma is characterized by chronic airway inflammation and airway remodelling which occurs in both proximal and distal airways. These changes are associated with development of airway hyper‐responsiveness and airflow limitation.

Lung endothelial monocyte-activating protein 2 is a mediator of cigarette smoke-induced emphysema in mice

Pulmonary emphysema is a disease characterized by alveolar cellular loss and inflammation. Recently, excessive apoptosis of structural alveolar cells has emerged as a major mechanism in the development of emphysema. Here, we investigated the proapoptotic and monocyte chemoattractant cytokine endothelial monocyte-activating protein 2 (EMAPII). Lung-specific overexpression of EMAPII in mice caused simplification of alveolar structures, apoptosis, and macrophage accumulation, compared with that in control transgenic mice. Additionally, in a mouse model of cigarette smoke-induced (CS-induced) emphysema, EMAPII levels were significantly increased in murine lungs. This upregulation was necessary for emphysema development, as neutralizing antibodies to EMAPII resulted in reduced alveolar cell apoptosis, inflammation, and emphysema-associated structural changes in alveoli and small airways and improved lung function. The mechanism of EMAPII upregulation involved an apoptosis-dependent feed-forward loop, since caspase-3 instillation in the lung markedly increased EMAPII expression, while caspase inhibition decreased its production, even in transgenic EMAPII mice. These findings may have clinical significance, as both current smokers and ex-smoker chronic obstructive pulmonary disease (COPD) patients had increased levels of secreted EMAPII in the bronchoalveolar lavage fluid compared with that of nonsmokers. In conclusion, we suggest that EMAPII perpetuates the mechanism of CS-induced lung emphysema in mice and, given its secretory nature, is a suitable target for neutralization antibody therapy.

Poly(inosinic-cytidylic) Acid–Triggered Exacerbation of Experimental Asthma Depends on IL-17A Produced by NK Cells

Viral infection of the respiratory tract represents the major cause of acute asthma exacerbations. dsRNA is produced as an intermediate during replication of respiratory viruses and triggers immune responses via TLR3. This study aimed at clarifying the mechanisms underlying TLR3 triggered exacerbation of experimental allergic asthma. The TLR3 ligand poly(inosinic-cytidylic) acid was applied intranasally to mice with already established experimental allergic asthma. Airway inflammation, cytokine expression, mucus production, and airway reactivity was assessed in wild-type, IL-17A, or IL-23p19–deficient, and in NK cell–depleted mice. Local application of poly(inosinic-cytidylic) acid exacerbated experimental allergic asthma in mice as characterized by enhanced release of proinflammatory cytokines, aggravated airway inflammation, and increased mucus production together with pronounced airway hyperresponsiveness. This was further associated with augmented production of IL-17 by Th17 cells and NK cells. Whereas experimental exacerbation could be induced in IL-23p19–deficient mice lacking mature, proinflammatory Th17 cells, this was not possible in mice lacking IL-17A or in NK cell–depleted animals. These experiments indicate a central role for IL-17 derived from NK cells but not from Th17 cells in the pathogenesis of virus-triggered exacerbation of experimental asthma.

A distinct microbiota composition is associated with protection from food allergy in an oral mouse immunization model

In our mouse model, gastric acid-suppression is associated with antigen-specific IgE and anaphylaxis development. We repeatedly observed non-responder animals protected from food allergy. Here, we aimed to analyse reasons for this protection. Ten out of 64 mice, subjected to oral ovalbumin (OVA) immunizations under gastric acid-suppression, were non-responders without OVA-specific IgE or IgG1 elevation, indicating protection from allergy. In these non-responders, allergen challenges confirmed reduced antigen uptake and lack of anaphylactic symptoms, while in allergic mice high levels of mouse mast-cell protease-1 and a body temperature reduction, indicative for anaphylaxis, were determined. Upon OVA stimulation, significantly lower IL-4, IL-5, IL-10 and IL-13 levels were detected in non-responders, while IL-22 was significantly higher. Comparison of fecal microbiota revealed differences of bacterial communities on single bacterial Operational-Taxonomic-Unit level between the groups, indicating protection from food allergy being associated with a distinct microbiota composition in a non-responding phenotype in this mouse model.

Distal airways are protected from goblet cell metaplasia by diminished expression of IL-13 signalling components.

Increased mucus production is a critical factor impairing lung function in patients suffering from bronchial asthma, the most common chronic inflammatory lung disease worldwide.

Long-term bortezomib treatment reduces allergen-specific IgE but fails to ameliorate chronic asthma in mice.

Background: Allergen-specific immunoglobulin (Ig) E initiates the effector cascade of allergic asthma and has been identified as a valuable target for therapeutic treatment of this disease. The proteasome inhibitor bortezomib was previously shown to deplete Ig-secreting plasma cells and to efficiently suppress Ig serum titers. The present study aimed at evaluating the therapeutic potential of the proteasome inhibitor bortezomib in allergic bronchial asthma. Methods: To address this question, a chronic experimental asthma mouse model was used in a therapeutic setting. Mice were sensitized to ovalbumin (OVA) and challenged with OVA aerosol for 12 weeks. After 6 weeks of challenge, bortezomib treatment was started and continued for 1 week (short-term) or 6 weeks (long-term) with a dosage of 0.75 mg/kg body weight twice a week. Lung function, lung histology, Ig serum titers and plasma cell numbers were assessed. Results: Whereas short-term treatment lowered bronchoalveolar lavage eosinophils, long-term treatment considerably reduced serum titers of anti-OVA IgE in mice with chronic experimental asthma. However, neither short-term nor long-term treatment significantly reduced plasma cell numbers, anti-OVA IgG1 serum titers or allergic airway inflammation or ablated airway hyperresponsiveness. Conclusion: Our results suggest that bortezomib treatment has only limited value as plasma cell-depleting therapy against allergic bronchial asthma.

Composition of the immunoglobulin classic antigen-binding site regulates allergic airway inflammation in a murine model of experimental asthma.

Background When bound to mast cell FcɛRI, IgE serves as antigen receptor for allergic reactions, permitting specific identification of the allergen. Although the core of the classic antigen‐binding site is heavy chain complementarity determining region 3 (CDR‐H3), recent studies suggest that allergens might also bind IgE in a superantigen‐like fashion outside the classic antigen‐binding site.

Peripheral Erythrocytes Decrease upon Specific Respiratory Challenge with Grass Pollen Allergen in Sensitized Mice and in Human Subjects

Background and Aims Specific hyper-responsiveness towards an allergen and non-specific airway hyperreactivity both impair quality of life in patients with respiratory allergic diseases. We aimed to investigate cellular responses following specific and non-specific airway challenges locally and systemically in i) sensitized BALB/c mice challenged with grass pollen allergen Phl p 5, and in ii) grass pollen sensitized allergic rhinitis subjects undergoing specific airway challenge in the Vienna Challenge Chamber (VCC). Methods and Results BALB/c mice (n = 20) were intraperitoneally immunized with grass pollen allergen Phl p 5 and afterwards aerosol challenged with either the specific allergen Phl p 5 (n = 10) or the non-specific antigen ovalbumin (OVA) (n = 10). A protocol for inducing allergic asthma as well as allergic rhinitis, according to the united airway concept, was used. Both groups of exposed mice showed significantly reduced physical activity after airway challenge. Specific airway challenge further resulted in goblet cell hyperplasia, enhanced mucous secretion, intrapulmonary leukocyte infiltration and lymphoid follicle formation, associated with significant expression of IL-4, IL-5 and IL-13 in splenocytes and also partially in lung tissue. Concerning circulating blood cell dynamics, we observed a significant drop of erythrocyte counts, hemoglobin and hematocrit levels in both mouse groups, challenged with allergen or OVA. A significant decrease in circulating erythrocytes and hematocrit levels after airway challenges with grass pollen allergen was also found in grass pollen sensitized human rhinitis subjects (n = 42) at the VCC. The effects on peripheral leukocyte counts in mice and humans however were opposed, possibly due to the different primary inflammation sites. Conclusion Our data revealed that, besides significant leukocyte dynamics, particularly erythrocytes are involved in acute hypersensitivity reactions to respiratory allergens. A rapid recruitment of erythrocytes to the lungs to compensate for hypoxia is a possible explanation for these findings.

A Single DH Gene Segment Is Sufficient for the Establishment of an Asthma Phenotype in a Murine Model of Allergic Airway Inflammation

Background: We have previously shown that the allergic sensitization to ovalbumin does not represent a superantigen-like immune response. In gene-targeted mice (ΔD-iD) with a single modified Diversity gene segment (DH) of the immunoglobulin heavy chain, enriched for charged amino acids, the asthma phenotype in a murine model was markedly alleviated compared to wild-type animals. Objective: We now sought to determine whether the confinement to a single DH gene segment alone leads to a reduced allergic phenotype. Methods: We examined another gene-targeted mouse strain (ΔD-DFL) with a single DH gene segment which encodes for neutral amino acids, thus reflecting the preferential repertoire in wild-type mice. Mice were sensitized intraperitoneally to ovalbumin. Results: Despite the constraint to a single DH gene segment, ΔD-DFL mice mounted high total and allergen-specific IgG1 and IgE serum levels after sensitization to ovalbumin. The affinity constants of allergen-specific IgG1 antibodies did not differ between ΔD-DFL and wild type. Following challenge with aerosolized allergen, a marked local TH2 cytokine response and an eosinophilic airway inflammation developed. Quantitative histology revealed increased mucus production and intense goblet cell metaplasia which were identical to those in wild type. Moreover, ΔD-DFL mice developed an airway hyperreactivity to methacholine and to the specific allergen, which both did not differ from those in wild-type animals. Conclusion: A single DH gene segment is sufficient for the establishment of the asthma phenotype in a murine model of allergic airway inflammation. Thus, the allergic phenotype depends on the amino acid composition and not on the diversity of the classical antigen-binding site.

IgE sensitization to inhalant allergens and the risk of airway infection and disease: A population-based study

Background Immunoglobulin E (IgE) sensitization, which is the propensity to develop IgE antibodies against common environmental allergens, is associated with a lymphocyte T-helper type 2 (Th2) skewed immune response and a high risk of allergic respiratory disease. Little is known about whether IgE sensitization confers an increased risk of respiratory infections in adults. We investigated the association between IgE sensitization and the incidence of acute airway infections, other infections and chronic lower airway disease events as recorded in nation-wide registries. Methods We included 14,849 persons from five population-based studies with measurements of serum specific IgE positivity against inhalant allergens. Participants were followed by linkage to Danish national registries (median follow-up time 11.3 years). The study-specific relative risks were estimated by Cox regression analysis, meta-analysed, and expressed as hazard ratios, HRs (95% confidence intervals, CIs). Results The relative risks for IgE sensitized vs. non-sensitized were: for pneumonia (HR = 1.20, 95% CI: 1.01, 1.41), other acute airway infection (HR = 0.86, 95% CI: 0.60, 1.22), infection (HR = 1.06, 95% CI: 0.90, 1.24), asthma (HR = 2.26, 95% CI: 1.79, 2.86), and other chronic lower airway disease (HR = 1.31, 95% CI: 1.08, 1.58). In never smokers, the higher risk of pneumonia (HR = 1.73, 95% CI: 1.23, 2.44) and asthma (HR = 3.17, 95% CI: 2.10, 4.76) among IgE sensitized was more pronounced. Conclusions IgE sensitization was associated with a higher risk of asthma, other chronic lower airway diseases, and pneumonia. However, the association between IgE sensitization and pneumonia may be explained by undiagnosed asthma causing the pneumonia. Further studies are needed for confirmation.