Jane M. Schuh

Airway hyperresponsiveness, but not airway remodeling, is attenuated during chronic pulmonary allergic responses to Aspergillus in CCR4−/− mice

The role of CC chemokine receptor 4 (CCR4) during the development and maintenance of Th2type allergic airway disease is controversial. In this study, we examined the role of CCR4 in the chronic allergic airway response to live Aspergillus fumigatus spores, or conidia, in A. fumigatussensitized mice. After the conidia challenge, mice lacking CCR4 (CCR4‐/‐ mice) exhibited significantly increased numbers of airway neutrophils and macrophages, and conidia were more rapidly eliminated from these mice compared with control CCR4 wild‐type (CCR4+/+) mice. Significant airway hyperresponsiveness to intravenous methacholine was observed at day 3 in CCR4‐/‐ mice, whereas at days 7 and 30, airway hyperresponsiveness was attenuated in these mice compared with control mice. A major reduction in peribronchial and airway eosinophilia was observed in CCR4‐/‐ mice at all times after conidia challenge in contrast to CCR4+/+ mice. Further, whole lung levels of interleukin (IL) 4 and IL‐5 were significantly increased in CCR4‐/‐ mice at day 3, whereas these Th2 cytokines and IL‐13 were significantly decreased at day 30 in CCR4‐/‐ mice compared with their wild‐type counterparts. Peribronchial fibrosis and goblet cell hyperplasia were similar in both groups of mice throughout the course of this model. In summary, CCR4 modulates both innate and acquired immune responses associated with chronic fungal asthma.

Stat6-Deficient Mice Develop Airway Hyperresponsiveness and Peribronchial Fibrosis during Chronic Fungal Asthma

Signal transducer and activator of transcription 6 (Stat6) is critical for Th2-mediated responses during allergic airway disease. To investigate the role of Stat6 in fungus-induced airway hyperresponsiveness and remodeling, Stat6-deficient (Stat6-/-) and Stat6-wildtype (Stat6+/+) mice were sensitized to Aspergillus fumigatus and airway disease was subsequently assessed in both groups at days 21, 30, 38, and 44 after an intratracheal challenge with live A. fumigatus conidia. At all times after conidia, histological analysis revealed an absence of goblet cell hyperplasia and markedly diminished peribronchial inflammation in Stat6-/- mice in contrast to Stat6+/+ mice. Airway hyperresponsiveness and peribronchial fibrosis in Stat6-/- mice were significantly reduced at day 21 after conidia compared with Stat6+/+ mice, but both groups exhibited significant, similar increases in these parameters at all subsequent times after conidia. In separate experiments, IL-13-responsive cells in Stat6-/- mice were targeted via the daily intranasal administration of 200 ng of IL-13-PE38QQR (IL13-PE), comprised of human IL-13 and a derivative of Pseudomonas exotoxin, from days 38 to 44 after the conidia challenge. IL13-PE treatment abolished airway hyperresponsiveness, but not peribronchial fibrosis in Stat6-/- mice. Taken together, these data demonstrate that the chronic development of airway hyperresponsiveness during fungal asthma is IL-13-dependent but Stat6-independent.

CXCR2 Is Necessary for the Development and Persistence of Chronic Fungal Asthma in Mice

The role of CXCR during allergic airway and asthmatic diseases is yet to be fully characterized. Therefore, the present study addressed the role of CXCR2 during Aspergillus fumigatus-induced asthma. Mice deficient in CXCR2 (CXCR2−/−) and wild-type counterparts (CXCR2+/+) were sensitized to A. fumigatus Ags and challenged with A. fumigatus conidia, and the resulting allergic airway disease was monitored for up to 37 days. At days 3 and 7 after conidia, CXCR2−/− mice exhibited significantly greater methacholine-induced airway hyperreactivity than did CXCR2+/+ mice. In contrast, CXCR2-deficient mice exhibited significantly less airway hyperresponsiveness than the wild-type control groups at days 14 and 37 after conidia. At all times after conidia, whole lung levels of IL-4, IL-5, and eotaxin/CC chemokine ligand 11 were significantly lower in CXCR2−/− mice than in the wild-type controls. Eosinophil and T cell, but not neutrophil, recruitment into the airways of A. fumigatus-sensitized CXCR2−/− mice was significantly impaired compared with wild-type controls at all times after the conidia challenge. Whole lung levels of IFN-γ, inflammatory protein-10/CXC ligand (CXCL) 10, and monokine induced by IFN-γ (MIG)/CXCL9 were significantly increased in CXCR2−/− mice compared with CXCR2+/+ mice at various times after conidia. Interestingly, at day 3 after conidia, neutrophil recruitment and airway hyperresponsiveness in CXCR2−/− mice was mediated by inflammatory protein-10/CXCL10 and, to a lesser degree, MIG/CXCL9. Taken together, these data suggest that CXCR2 contributes to the persistence of asthmatic disease due to A. fumigatus.

The role of CC chemokine receptor 5 (CCR5) and RANTES/CCL5 during chronic fungal asthma in mice

In the present study, we explored the role of CC chemokine receptor 5 (CCR5) in a murine model of chronic fungal asthma induced by an intrapulmonary challenge with Aspergillus fumigatus conidia (or spores). Airway hyperresponsiveness was significantly lower in A. fumigatus‐sensitized mice lacking CCR5 (CCR5‐/‐) compared with similarly sensitized wild‐type (CCR5+/+) control mice at days 2, 21, 30, and 40 after the conidia challenge. CCR5‐/‐ mice exhibited significantly less peribronchial T‐cell and eosinophil accumulation and airway‐remodeling features, such as goblet cell hyperplasia and peribronchial fibrosis, compared with CCR5+/+ mice at these times after conidia. However, both groups of mice exhibited similar allergic airway disease at day 12 after the conidia challenge. In CCR5‐/‐ mice at day 12, the allergic airway disease was associated with airway hyperresponsiveness, peribronchial allergic inflammation, and goblet cell hyperplasia. Immunoneutralization of RANTES/CCL5 in sensitized CCR5+/+ and CCR5‐/‐ mice for 12 days after the conidia challenge significantly reduced the peribronchial inflammation and airway hyperresponsiveness in comparison with control wild‐type and knockout mice at this time. These data demonstrate that functional CCR5 and RANTES/CCL5 are required for the persistence of chronic fungal asthma in mice.

Mannose-binding lectin deficiency alters the development of fungal asthma: effects on airway response, inflammation, and cytokine profile

Aspergillus fumigatus is a major fungal pathogen that may be fatal to immunocompromised individuals and causes airway hyperreactivity and remodeling in sensitized individuals. Herein, we examined the role of mannose‐binding lectin (MBL), a complement‐activating plasma protein, during ulmonary innate and allergic immune responses directed against A. fumigatus spores or conidia. Neither group of nonsensitized MBL‐A‐sufficient (MBL‐A+/+) nor ‐deficient (MBL‐A−/−) mice challenged with an intravenous or intratracheal (i.t.) bolus of A. fumigatus spores experienced fungus‐induced mortality, but marked airway remodeling was observed in MBL‐A−/− mice challenged i.t. with conidia. In a model of chronic fungal asthma, MBL‐A+/+ and MBL‐A−/− A. fumigatus‐sensitized mice were examined at days 4 and 28 after an i.t. challenge with A. fumigatus conidia. Airway hyperresponsiveness in sensitized MBL‐A−/− mice was significantly decreased at both times after conidia challenge compared with the sensitized MBL‐A+/+ group. In the sensitized MBL‐A−/− mice, whole lung T helper cell type 2 cytokine levels were significantly decreased at day 4 after conidia, and whole lung interferon‐γ levels were significantly increased at day 28 after conidia when compared with controls. However, histological evidence showed similar airway remodeling at day 28 after conidia (i.e., subepithelial fibrosis and goblet cell metaplasia) in the two groups of mice. Thus, these findings show that MBL‐A is not required for mouse survival following exposure to A. fumigatus conidia, and this murine collectin isoform contributes to the development and maintenance of airway hyperresponsiveness but not chronic airway remodeling during chronic fungal asthma.

IL-13 Fusion Cytotoxin Ameliorates Chronic Fungal-Induced Allergic Airway Disease in Mice

IL-13 has emerged as a major contributor to allergic and asthmatic responses, and as such it represents an attractive target in these diseases. In this study, IL-13-responsive cells in the lung were targeted via the intranasal administration of IL-13-PE38QQR (IL-13-PE), comprised of human IL-13 and a derivative of Pseudomonas exotoxin, to Aspergillus fumigatus-sensitized mice challenged with A. fumigatus spores, or conidia. Mice received 50, 100, or 200 ng of IL-13-PE or diluent alone (i.e., control group) on alternate days from day 14 to day 28 after the conidia challenge. The control group of mice exhibited significant airway hyperreactivity, goblet cell hyperplasia, and peribronchial fibrosis at day 28 after conidia. Although the two lower doses of IL-13-PE had limited therapeutic effects in mice with fungal-induced allergic airway disease, the highest dose of IL-13-PE tested significantly reduced all features of airway disease compared with the control group. Whole lung mRNA expression of IL-4Rα and IL-13Rα1 was markedly reduced, whereas bronchoalveolar lavage and whole lung levels of IFN-γ were significantly elevated in mice treated with 200 ng of IL-13-PE compared with the control group. This study demonstrates that a therapy designed to target IL-13-responsive cells in the lung ameliorates established fungal-induced allergic airway disease in mice.

Aspergillus and asthma – any link?

The innate immune and acquired immune responses are not separate, parallel systems but form interdependent components of a single integrated immune response. This is nicely highlighted by an expanding database demonstrating that the innate immune response provides the acquired immune response with information about the origin of the antigen and the type of response required via pattern recognition receptors (PRRs). Aspergillus is among a growing list of allergens that can aggravate asthmatic responses. Significant pulmonary pathology is associated with Aspergillus-induced allergic and asthmatic lung disease characterized by increased Th2 cytokine generation, IgE and IgG, eosinophilia, airway hyper-responsiveness and airway remodeling. Experimental data from a model of chronic fungal asthma demonstrate that thymus associated and regulated chemokine (TARC/CCL17) and macrophage derived chemokine (MDC/CCL22), working via CCR4, directly impair the innate anti-fungal immune response, thereby promoting the maintenance of acquired Th2-mediated asthmatic disease. Both chemokines appear to accomplish this by regulating the expression of PRRs such as toll like receptors (TLRs) and triggering receptor expressed on myeloid cells (TREM-1) by immune cells. Thus, the link between Aspergillus and asthma appears to reside in the magnitude and appropriateness of the host innate immune response, and ongoing research is revealing promising targets for therapy.

μ-Chain–Deficient Mice Possess B-1 Cells and Produce IgG and IgE, but Not IgA, following Systemic Sensitization and Inhalational Challenge in a Fungal Asthma Model

Allergic bronchopulmonary aspergillosis is often difficult to treat and results in morbidity associated with chronic airway changes. This study assessed the requirement for B cells and their products in the allergic pulmonary phenotype in a murine model of fungal allergic asthma that mimics allergic bronchopulmonary aspergillosis. C57BL/6 and μMT mice (assumed to lack peripheral B cells) were sensitized with Aspergillus fumigatus extract and challenged with two inhalation exposures of live conidia to induce airway disease. Airway hyperresponsiveness after methacholine challenge, peribronchovascular inflammation, goblet cell metaplasia, and fibrotic remodeling of the airways was similar between μMT mice and their wild-type counterparts (C57BL/6). Surprisingly, even in the absence of the μ-chain, these μMT mice produced IgE and IgG Abs, although the Abs induced did not have specificity for A. fumigatus Ags. In contrast, IgA was not detected in either the lavage fluid or serum of μMT mice that had been exposed to A. fumigatus. Our findings also reveal the existence of CD19+CD9+IgD+ B-1 cells in the lungs of the μMT animals. These data show the μMT mice to have a developmental pathway independent of the canonical μ-chain route that allows for their survival upon antigenic challenge with A. fumigatus conidia, although this pathway does not seem to allow for the normal development of Ag-specific repertoires. Additionally, this study shows that IgA is not required for either clearance or containment of A. fumigatus in the murine lung, as fungal outgrowth was not observed in the μMT animals after multiple inhalation exposures to live conidia.

Intrapulmonary targeting of RANTES/CCL5-responsive cells prevents chronic fungal asthma

Regulated upon activation in normal T cells, expressed, and secreted (RANTES)/CCL5 is abundantly expressed during atopic asthma, suggesting that it is an important mediator of this disease. The contribution of intrapulmonary RANTES/CCL5‐sensitive cells during Aspergillus fumigatus‐induced airway disease in mice was assessed in this study. The intranasal delivery of a chimeric protein comprised of RANTES/CCL5 and a truncated version of Pseudomonas exotoxin A (RANTES‐PE38) significantly attenuated serum IgE, peribronchial eosinophilia, and airway hyperreactivity when it was administered from day 0 to 15 after intratracheal conidia challenge in A. fumigatus‐sensitized mice but had little effect when delivered from day 15 to 30 after conidia challenge. Intranasal RANTES‐PE38 treatment enhanced macrophage recruitment and accelerated fungal clearance in the lungs of RANTES‐PE38‐treated mice. These data reveal a major role for RANTES/CCL5 and its receptors in the development of fungal asthma yet reveal only a modest role in the chronic remodeling of the allergic airway in this disease.

Chemokines and cytokines: axis and allies in asthma and allergy

Allergic asthma can be precipitated by many factors. For the atopic person, fungus, pollen, dust mites, cockroach antigens, and diesel exhaust are all agents that may trigger an allergic attack. Cytokines and chemokines are integral mediators of fungal asthma. From the earliest time points, they recruit and activate the cells required for the clearance of fungus as well as being critical factors involved in the immunopathology of this disease. In the final analysis, it is clear that these mediators can act to the benefit or the detriment of the host.