Michael Wegmann

Prenatal lipopolysaccharide‐exposure prevents allergic sensitization and airway inflammation, but not airway responsiveness in a murine model of experimental asthma

Background Epidemiological evidence underlines the impact of prenatal environmental factors on the development of postnatal allergies. In this regard an inverse correlation between lipopolysaccharide (LPS) exposure and development of childhood allergy has been found.

Immunomodulatory Effects of Viral TLR Ligands on Experimental Asthma Depend on the Additive Effects of IL-12 and IL-10

Based on epidemiological data, the hygiene hypothesis associates poor hygienic living conditions during childhood with a lower risk for the development of allergic diseases such as bronchial asthma. The role of viral infections, and especially of viral TLR ligands, within this context remains to be clarified. Viral TLR ligands involve dsRNA and ssRNA which are recognized by TLR-3 or TLR-7, respectively. In this study, we evaluated the impact of TLR-3 or TLR-7 activation on experimental asthma in mice. Systemic application of the synthetic TLR-3 or TLR-7 ligands polycytidylic-polyinosinic acid (p(I:C)) or R-848, respectively, during the sensitization phase prevented the production of OVA-specific IgE and IgG1 Abs and subsequently abolished all features of experimental asthma including airway hyperresponsiveness and allergic airway inflammation. Furthermore, administration of p(I:C) or R-848 to animals with already established primary allergic responses revealed a markedly reduced secondary response following allergen aerosol rechallenges. In contrast to wild-type animals, application of p(I:C) or R-848 to IL-12p35−/− mice had no effect on airway inflammation, goblet cell hyperplasia, and airway hyperresponsiveness. However, in the absence of IL-12, the numbers of eosinophils and lymphocytes in bronchoalveolar lavage fluids were still significantly reduced. These partial effects could also be abolished by neutralizing anti-IL-10 Abs in IL-12p35−/− mice. These data indicate that TLR-3 or TLR-7 activation by viral TLR ligands has both preventive as well as suppressive effects on experimental asthma which is mediated by the additive effects of IL-12 and IL-10.

Allergic Airway Inflammation Inhibits Pulmonary Antibacterial Host Defense

The innate immune system of the lung is a multicomponent host defense system and in addition has an instructing role in regulating the quality and quantity of the adaptive immune response. When the interaction between innate and adaptive immunity is disturbed, pathological conditions such as asthma can develop. It was the aim of the study to investigate the effect of the allergic inflammation of the lung on the innate host defense during bacterial infection. Human bronchial epithelial cells were preincubated with Th2 cytokines and infected with Pseudomonas aeruginosa. The effect of the Th2 cytokines on the mRNA levels of antimicrobial peptides and the antimicrobial activity of HBEC was determined. To investigate the influence of an allergic inflammation on pulmonary host defense in vivo, mice sensitized and challenged with OVA were infected with P. aeruginosa, and the number of viable bacteria in the lungs was determined together with markers of inflammation like cytokines and antimicrobial peptides. Exposure of airway epithelial cells to Th2 cytokines resulted in a significantly decreased antimicrobial activity of the cells and in suppressed mRNA levels of the antimicrobial peptide human β-defensin 2. Furthermore, mice with allergic airway inflammation had significantly more viable bacteria in their lungs after infection. This was consistent with reduced levels of proinflammatory cytokines and of the antimicrobial peptide cathelin-related antimicrobial peptide. These results show that an allergic airway inflammation suppresses the innate antimicrobial host defense. The adaptive immune system modulates the functions of the pulmonary innate immune system.

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.

Induction of long-lived allergen-specific plasma cells by mucosal allergen challenge

BACKGROUND Allergen-specific IgE antibodies are responsible for the pathogenesis of type I hypersensitivity. In patients with allergy, IgE titers can persist in the apparent absence of allergen for years. Seasonal allergen exposure triggers clinical symptoms and enhances allergen-specific IgE. Whether allergen-specific plasma cells originating from seasonal allergen exposures can survive and become long-lived is so far unclear. OBJECTIVE We analyzed the localization and lifetimes of allergen-specific IgE-secreting, IgA-secreting, and IgG(1)-secreting plasma cells after allergen inhalation in an ovalbumin-induced murine model of allergic asthma. METHODS Ovalbumin-specific IgG(1)-secreting, IgA-secreting, and IgE-secreting cells in lungs, spleen, and bone marrow were isolated and tested for antibody secretion by the ELISpot technique. Longevity of ovalbumin-specific plasma cells was determined by cyclophosphamide treatment, which depletes proliferating plasmablasts but leaves plasma cells untouched. Ovalbumin aerosol-induced infiltrates in lungs were localized by confocal microscopy. RESULTS Long-lived ovalbumin-specific plasma cells were generated by systemic sensitization and survived in bone marrow and spleen, maintaining systemic ovalbumin-specific titers of IgG, IgA, and IgE. On inhalation of ovalbumin-containing aerosol, sensitized mice developed airway inflammation and more ovalbumin-specific IgG(1)-secreting, IgA-secreting, and IgE-secreting cells in the lungs and in secondary lymphoid organs. These plasma cells joined the pool of ovalbumin-specific plasma cells in the bone marrow and became long-lived-that is, they are resistant to cyclophosphamide. Termination of ovalbumin inhalation depleted ovalbumin-specific plasma cells from the lungs, but they persisted in spleen and bone marrow. CONCLUSION Our results show that inhalation of aerosolized allergen generates long-lived, allergen-specific IgG(1)-secreting, IgA-secreting, and IgE-secreting plasma cells that survive cytostatic treatment.

Effective prevention and therapy of experimental allergic asthma using a GATA-3–specific DNAzyme

BACKGROUND Allergic bronchial asthma is a chronic inflammatory disease of the airways. The transcription factor GATA-3 was shown to play an important role in TH2 cell activation, but also in the regulation of other cell types involved in bronchial asthma including mast cells, eosinophils, and epithelial cells. DNAzymes represent a new class of antisense molecules that combines the specificity of DNA base pairing with an inherent RNA-cleaving enzymatic activity. OBJECTIVE To develop a GATA-3 mRNA-specific DNAzyme and analyze its allergy-preventing activity in murine models of experimental allergic asthma. METHODS The most active DNAzyme (termed gd21) was selected by in vitro cleavage assays. Allergic airway inflammation was assessed by inflammatory cell and cytokine analysis within bronchoalveolar lavage. Lung histology, including goblet cell hyperplasia and lung function, was analyzed using head-out body-plethysmography. RESULTS Intranasal administration of gd21 prevented airway inflammation and mucus production and inhibited development of airway hyperresponsiveness to methacholine in models of acute allergic airway inflammation. Similar effects were also detected in a model of chronic experimental asthma. Interestingly, gd21 was at least as effective as other antisense molecules, and off-target effects were not detected. Further experiments indicated that pulmonary surfactant may facilitate the cellular uptake of gd21 by acting as an endogenous transfectant. CONCLUSION These results indicate that topical application of the GATA-3-specific DNAzyme is a promising novel approach for the treatment of allergic bronchial asthma.

Anti-ulcer treatment during pregnancy induces food allergy in mouse mothers and a Th2-bias in their offspring

The treatment of dyspeptic disorders with anti‐acids leads to an increased risk of sensitization against food allergens. As these drugs are taken by 30–50% of pregnant women due to reflux and heartburn, we aimed here to investigate the impact of maternal therapy with anti‐acids on the immune response in the offspring in a murine model. Codfish extract as model allergen was fed with or without sucralfate, an anti‐acid drug, to pregnant BALB/c mice during pregnancy and lactation. These mothers developed a codfish‐specific allergic response shown as high IgG1 and IgE antibody levels and positive skin tests. In the next step we analyzed whether this maternal sensi‐tization impacts a subsequent sensitization in the offspring. Indeed, in stimulated splenocytes of these off‐spring we found a relative Th2‐dominance, because the Thl‐ and T‐regulatory cytokines were significantly sup‐pressed. Our data provide evidence that the anti‐acid drug sucralfate supports sensitization against food in pregnant mice and favors a Th2‐milieu in their offspring. From these results we propose that anti‐acid treatment during pregnancy could be responsible for the increasing number of sensitizations against food allergens in young infants.—Schöll, I., Ackermann, U., Özdemir, C., Blümer, N., Dicke, T., Sel, S., Sel, S., Wegmann, M., Szalai, K., Knittelfelder, R., Untersmayr, E., Scheiner, O., Garn, H., Jensen‐Jarolim, E., Renz, H. Anti‐ulcer treatment during pregnancy induces food allergy in mouse mothers and a Th2‐bias in their offspring. FASEB J. 21, 1264–1270 (2007)

Coexpression of TGF-β1 and IL-10 Enables Regulatory T Cells to Completely Suppress Airway Hyperreactivity

In allergic airway disease, Treg may play an important role in the modulation of airway hyperreactivity (AHR) and inflammation. We therefore investigated the therapeutic potential of Treg in an Ag-dependent murine asthma model. We here describe that AHR can be completely suppressed by adoptive transfer of Treg overexpressing active TGF-β1. Using mice with impaired TGF-β signaling in T cells, we could demonstrate that TGF-β signaling in recipient effector T cells or transferred Treg themselves is not required for the protective effects on AHR. However, the expression of IL-10 by Treg was found to be essential for the suppression of AHR, since Treg overexpressing active TGF-β1 but deficient in IL-10 lacked protective effects. Airway inflammation could not be significantly suppressed by wild-type or transgenic Treg. In conclusion, modulation of cytokine expression by Treg may have therapeutic potential for the treatment of AHR in asthma. The mechanisms of the effects of Treg on airway inflammation require further clarification.

Targeting Eosinophil Biology in Asthma Therapy

Due to their role as main effector cells in immune reactions against invading parasites, eosinophils have a plethora of molecules available to destroy these complex pathogens. Their role in allergic diseases such as bronchial asthma, where they do not have to conquer pathogens, is discussed controversially. However, since eosinophils were identified by Paul Ehrlich in tissue and sputum of patients with asthma, it was regarded that their important defensive role turns into its direct opposite so that these cells cause destruction of the airway tissue, ultimately leading to the formation of disease phenotype. Thus, eosinophils were identified as a prime target in therapeutic intervention of bronchial asthma. Over the last years, a number of mediators and receptors involved in the regulation of eosinophil recruitment, chemotaxis, activation, survival, and apoptosis have been identified. Some of these molecules have been addressed in vitro and in animal models of experimental asthma to evaluate their therapeutic potential in asthma. A few of these candidates have been tested in clinical studies, which produced surprising results questioning the role of eosinophils in asthma pathogenesis. This article summarizes these approaches and gives a critical overview about further candidate molecules that have been recently discussed as targets for an eosinophil-specific asthma therapy.

Nerve Growth Factor and Neurotrophin-3 Mediate Survival of Pulmonary Plasma Cells during the Allergic Airway Inflammation

Allergen-specific Abs play a pivotal role in the induction and maintenance of allergic airway inflammation. During secondary immune responses, plasma cell survival and Ab production is mediated by extrinsic factors provided by the local environment (survival niches). It is unknown whether neurotrophins, a characteristic marker of allergic airway inflammation, influence plasma cell survival in the lung. Using a mouse model of allergic asthma, we found that plasma cells from the lung and spleen are distinct subpopulations exhibiting differential expression patterns of neurotrophins and their receptors (Trks). In vitro, the nerve growth factor (NGF) and neurotrophin-3 (NT3) led to a dose-dependent increase in viability of isolated pulmonary plasma cells due to up-regulation of the antiapoptotic Bcl2 pathway. In parallel, the expression of transcription factors that stimulate the production of immunoglobulins (X-box binding protein 1 and NF-κB subunit RelA) was enhanced in plasma cells treated with NGF and NT3. These findings were supported in vivo. When the NGF pathway was blocked by intranasal application of a selective TrkA inhibitor, sensitized mice showed reduced numbers of pulmonary plasma cells and developed lower levels of allergen-specific and total serum IgE in response to OVA inhalation. This suggests that in the allergic airway inflammation, NGF/TrkA-mediated pulmonary IgE production contributes significantly to serum-IgE levels. We conclude that the neurotrophins NGF and NT3 act as survival factors for pulmonary plasma cells and thus are important regulators of the local Ab production in the allergic airway disease.