Comparison of the effects of repetitive low-dose and single-dose antigen challenge on airway inflammation

Repetitive nasal allergen challenge in allergic rhinitis: Priming and Th2-type inflammation but no evidence of remodelling

BACKGROUND

Local tissue eosinophilia and Th2 cytokines are characteristic features of seasonal allergic rhinitis. Airway remodelling is a feature of asthma whereas evidence for remodelling in allergic rhinitis (AR) is conflicting.

OBJECTIVE

By use of a novel human repetitive nasal allergen challenge (RAC) model, we evaluated the relationship between allergic inflammation and features of remodelling in AR.

METHODS

Twelve patients with moderate-severe AR underwent 5 alternate day challenges with diluent which after 4 weeks were followed by 5 alternate day challenges with grass pollen extract. Nasal symptoms, Th1/Th2 cytokines in nasal secretion and serum were evaluated. Nasal biopsies were taken 24 hours after the 1st and 5th challenges with diluent and with allergen. Sixteen healthy controls underwent a single challenge with diluent and with allergen. Using immunohistochemistry, epithelial and submucosal inflammatory cells and remodelling markers were evaluated by computed image analysis.

RESULTS

There was an increase in early and late-phase symptoms after every allergen challenge compared to diluent (both P < .05) with evidence of both clinical and immunological priming. Nasal tissue eosinophils and IL-5 in nasal secretion increased significantly after RAC compared to corresponding diluent challenges (P < .01, P = .01, respectively). There was a correlation between submucosal mast cells and the early-phase clinical response (r = 0.79, P = .007) and an association between epithelial eosinophils and IL-5 concentrations in nasal secretion (r = 0.69, P = .06) in allergic rhinitis. No differences were observed after RAC with regard to epithelial integrity, reticular basement membrane thickness, glandular area, expression of markers of activation of airway remodelling including α-SMA, HSP-47, extracellular matrix (MMP7, 9 and TIMP-1), angiogenesis and lymphangiogenesis for AR compared with healthy controls.

CONCLUSION

Novel repetitive nasal allergen challenge in participants with severe persistent seasonal allergic rhinitis resulted in tissue eosinophilia and increases in IL-5 but no structural changes. Our data support no link between robust Th2-inflammation and development of airway remodelling in AR.

High- and low-dose allergen challenges in asthmatic patients using inhaled corticosteroids

AIMS

The inhaled allergen challenge model has been used previously to investigate the effects of novel anti-inflammatory drugs in inhaled corticosteroid (ICS)-naïve asthmatics. The aim of this study was to characterize high- and low-dose allergen challenges in asthmatic patients using ICS.

METHODS

Twenty-eight asthmatic patients taking ICS (beclomethasone equivalent <1000 μg day(-1) ) were recruited for high-dose allergen challenge, of whom 10 subsequently also had a repeat low-dose challenge comprising seven allergen challenges. Induced sputum was collected for measurements of cell counts and supernatant biomarkers.

RESULTS

The high-dose allergen challenge caused an early and late asthmatic response in 19 of 28 patients; the mean maximal fall in the forced expiratory volume in 1 s (FEV1 ) was 29.1% (SD 6.2%) and 25.1% (SD 9.6%), respectively. There was also an increase in sputum eosinophils of 6.2% (P = 0.0004), as well as supernatant eosinophil cationic protein levels. The low-dose allergen challenge caused an acute fall in FEV1 , but had no effect on FEV1 at 24 h after challenge or sputum measurements.

CONCLUSIONS

The high-dose allergen challenge in asthmatics using ICS induces a late asthmatic response associated with an increase in eosinophilic airway inflammation. This may be a suitable model for studying the effects of novel anti-inflammatory drugs added to maintenance ICS treatment.

Airway responses and inflammation in subjects with asthma after four days of repeated high-single-dose allergen challenge

BACKGROUND

Both standard and low-dose allergen provocations are an established tool in asthma research to improve our understanding of the pathophysiological mechanism of allergic asthma. However, clinical symptoms are less likely to be induced. Therefore, we designed a protocol for repetitive high-dose bronchial allergen challenges to generate clinical symptoms and airway inflammation.

METHODS

A total of 27 patients aged 18 to 40 years with positive skin-prick tests and mild asthma underwent repetitive high-dose allergen challenges with household dust mites for four consecutive days. Pulmonary function and exhaled NO were measured at every visit. Induced sputum was analysed before and after the allergen challenges for cell counts, ECP, IL-5, INF-γ, IL-8, and the transcription factor Foxp3.

RESULTS

We found a significant decrease in pulmonary function, an increased use of salbutamol and the development of a late asthmatic response and bronchial hyperresponsiveness, as well as a significant induction of eNO, eosinophils, and Th-2 cytokines. Repeated provocation was feasible in the majority of patients. Two subjects had severe adverse events requiring prednisolone to cope with nocturnal asthma symptoms.

CONCLUSIONS

Repeated high-dose bronchial allergen challenges resulted in severe asthma symptoms and marked Th-2-mediated allergic airway inflammation. The high-dose challenge model is suitable only in an attenuated form in diseased volunteers for proof-of-concept studies and in clinical settings to reduce the risk of severe asthma exacerbations.

TRIAL REGISTRATION

ClinicalTrials.govNCT00677209.

Tumor necrosis factor alpha (TNF-α) autoregulates its expression and induces adhesion molecule expression in asthma

Subjects with mild asthma underwent repeated low-dose allergen exposure and bronchial biopsies were examined for the expression of TNF-α and adhesion molecules. Bronchial biopsies from moderately severe asthmatics were then tested in an explant culture system to assess the effect of Der p and CDP-870, a TNF-α blocking pegylated-antibody Fab, on expression of TNF-α and adhesion molecules. Low-dose allergen challenge significantly upregulated sub-mucosal mast cells, TNF-α(+) cells, and VCAM. When bronchial explants were exposed to Der p and CDP 870 for 24h, CDP 870 caused a significant reduction in TNF-α release both at baseline and following stimulation with Der p allergen. The bronchial biopsies showed significant upregulation of TNF-α positive cells and ICAM-1 following exposure to Der p (p=0.03) and this was reduced in the presence of CDP-870. So, allergen exposure up-regulates TNF-α expression in asthma and down-stream targets, including adhesion molecules that contribute to airway inflammation.

Prolonged eosinophil production after allergen exposure in IFN-gammaR KO mice is IL-5 dependent

Asthma is a T helper 2 (Th2)-driven inflammatory process characterized by eosinophilia. Prolonged airway eosinophilia is commonly observed in asthma exacerbations. Our aim was to evaluate whether eosinophilia in prolonged allergic inflammation is associated with a continuous supply of new eosinophils to the airways, and how this is regulated. Ovalbumin (OVA)-sensitized interferon-gamma receptor knockout mice (IFN-gammaR KO), known to maintain a long-lasting eosinophilia after allergen exposure, were compared to wild type (wt) controls. Animals were exposed to OVA or phosphate-buffered saline on three consecutive days, and bone marrow (BM), blood and bronchoalveolar lavage (BAL) samples were collected 24 h, 7 and 21 days later. Newly produced cells were labelled using bromodeoxyuridine (BrdU). Serum IL-5 was measured and its role was investigated by administration of a neutralizing anti-IL-5 antibody. In-vitro eosinophilopoiesis was examined in both groups by a colony-forming assay. Allergen challenge increased eosinophils in BM, blood and BAL, in both IFN-gammaR KO and wt mice, both 24 h and 7 days after the last allergen exposure. At 21 days after the last exposure, only IFN-gammaR KO mice maintained significantly increased eosinophil numbers. Approximately 50% of BAL granulocytes in IFN-gammaR KO were produced during the last 6 days. Interleukin (IL)-5 concentration was increased in IFN-gammaR KO mice, and anti-IL-5 reduced eosinophil numbers in all compartments. Increased numbers of eosinophil colonies were observed in IFN-gammaR KO mice after allergen exposure versus controls. In this model of a Th2-driven prolonged allergic eosinophilia, new eosinophils contribute to the extended inflammation in the airways by enhanced BM eosinophilopoiesis in an IL-5-dependent manner.

Montelukast treatment attenuates the increase in myofibroblasts following low-dose allergen challenge

RATIONALE

Airway remodeling is believed to be important in the pathophysiology of asthma, and myofibroblasts are increased in the airways of asthmatic individuals 24 h after allergen challenge. Leukotriene receptor antagonists exert antiinflammatory activity in asthma, but it is unknown whether they influence indices of airway remodeling. In the present study, we evaluated the effect of montelukast on airway myofibroblasts following low-dose allergen challenge (LDAC).

METHODS

Stable subjects with mild asthma were included in a two-center, randomized, parallel-group study. A 2-week run-in period was followed by LDAC and endobronchial biopsy. Subjects were then randomized to receive either montelukast, 10 mg/d, or placebo (n = 10 in each group) for 8 weeks in a double-blind manner; at the end of the treatment period, subjects underwent a second LDAC and endobronchial biopsy. The effect of treatment on myofibroblasts, fibroblasts, and inflammatory cells was examined using electron microscopy techniques.

RESULTS

Treatment with montelukast showed no significant difference by comparison with placebo but did show a significant within-group treatment-related decrease in airway wall myofibroblasts not seen in the placebo group. In addition, the montelukast-treated group also showed a significant within-group reduction in lymphomononuclear cells and increased neutrophils.

CONCLUSIONS

The results suggest that montelukast has an inhibitory effect on airway structural cells that play a key role in airway remodeling in allergic airway inflammation, and that montelukast may be a useful therapy to attenuate airway remodeling in asthma.

Aeroallergen prevalence in the northern New Jersey-New York City metropolitan area: a 15-year summary

BACKGROUND

Elevated environmental pollen levels result in allergic and asthmatic symptoms in sensitive individuals.

OBJECTIVE

To present data collected during a 15-year period demonstrating the seasonal pollen variation in a metropolitan area.

METHODS

Pollen was collected daily except for weekends. Pollen counts were counted using light microscopy and were used to calculate the average daily pollen count per month between March 1 and October 31 of each calendar year. The month in which each class of pollen reached the highest level (peak) was analyzed across the sampling period. Spearman p correlation coefficients were calculated to show changes in peak pollen levels across time.

RESULTS

The average daily pollen level (tree, grasses, and weeds) for each month was analyzed (1987-2002). Tree pollen peaked in May and composed 98.7% of the measurable pollen between March and May. Grass pollen had a biphasic peak (June and September), representing 42.9% of measurable pollen in July and 6.4% in September. Weed and ragweed levels peaked in September. Total weed pollen constituted 93.5% of the measurable pollen between August and October. The combined total pollen levels peaked in May. The highest annual peak tree pollen count was observed between 1992 and 1997, with a linear relationship between tree and total pollen (R2 = 0.97); highest levels of grass pollen were observed between 1993 and 1997; and highest levels of weed pollen were observed between 1993 and 1995. A trend toward declining levels of total pollen was observed between 1993 and 2002. This declining trend was most pronounced for weed pollen.

CONCLUSIONS

Aeroallergens pollinate sequentially, starting with trees in the spring, grass throughout the summer, and weeds in late summer to early fall. Pollen levels have declined from 1993 to the present. The most pronounced drop has been in weed pollen levels. Grass pollen demonstrates a biphasic pattern. Tree pollen composes most annual pollen measured in the northern New Jersey-New York City area.

Contamination of nebulizers with environmental allergens

BACKGROUND

A previous article described cockroach allergen in the nebulizer reservoir of an asthmatic patient who experienced a life-threatening exacerbation after nebulizer use.

OBJECTIVE

To determine whether indoor allergens can be measured in home nebulizers.

METHODS

As part of a large study examining nebulizer use in underserved asthmatic children, visiting nurses replaced nebulizer sets in patients' homes. Twenty used sets were randomly selected for analysis, without linkage to clinical or home environmental data. Nebulizer reservoirs and negative controls (buffer and albuterol) were extracted overnight with 2 mL of buffer. For positive controls, nebulizer sets were placed in homes with cats and dogs, and other reservoirs were intentionally contaminated with cat (Fel d 1), dog (Can f 1), cockroach (Bla g 1 and Bla g 2), and mouse (Mus m 1) skin test solutions. Extracts were tested for allergens in a masked manner using enzyme-linked immunosorbent assay.

RESULTS

Of 17 reservoirs with adequate specimens for allergen detection, 5 (29%) had measurable levels for at least 1 of 5 allergens tested. One reservoir had measurable Can f 1, 2 had Bla g, 3 had Mus m 1, and none had Fel d 1 allergen. Two of 3 homes with cats where nebulizer setups were placed had measurable Fel d 1 in the reservoir, and 1 of 2 homes with dogs had measurable Can f 1. Reservoirs kept in sealed plastic bags had no detectable allergen.

CONCLUSIONS

Indoor allergens can be found in the nebulizer equipment of children with asthma, with the potential for adverse consequences. Storing nebulizer sets in sealed plastic bags may prevent contamination.

High allergen exposure as a risk factor for asthma and allergic disease

The association between pet ownership in childhood and subsequent asthma and sensitization is very controversial. Intriguing, but contradictory, reports have caused considerable uncertainty in parents who wish to avoid asthma and allergic disease in their children. This article argues that high allergen exposure is a risk factor for asthma and allergic disease. It describes dispersal of pet allergens in society and critically assesses epidemiological studies regarding how early exposure to pet allergens affects subsequent immunoglobulin E-sensitization and allergic diseases. Additionally, this article evaluates the effects of allergen exposure in already sensitized subjects with asthma. Cat and dog allergens are ubiquitous in society and may induce sensitization and allergic symptoms in predisposed individuals, regardless of pet ownership. This, in combination with selection mechanisms for pet ownership in families with a history of allergic diseases, makes it difficult to study associations between early exposure to pets and subsequent allergic disease. Nevertheless, exposure to pet allergens worsens asthma in already sensitized children. Thus, it is clear that clinicians should advise sensitized asthmatics that avoidance of exposure to indoor allergens is an important element in the treatment of allergic disease.

Neural circuitry underlying the interaction between emotion and asthma symptom exacerbation

Asthma, like many inflammatory disorders, is affected by psychological stress, suggesting that reciprocal modulation may occur between peripheral factors regulating inflammation and central neural circuitry underlying emotion and stress reactivity. Despite suggestions that emotional factors may modulate processes of inflammation in asthma and, conversely, that peripheral inflammatory signals influence the brain, the neural circuitry involved remains elusive. Here we show, using functional magnetic resonance imaging, that activity in the anterior cingulate cortex and insula to asthma-relevant emotional, compared with valence-neutral stimuli, is associated with markers of inflammation and airway obstruction in asthmatic subjects exposed to antigen. This activation accounts for > or =40% of the variance in the peripheral markers and suggests a neural basis for emotion-induced modulation of airway disease in asthma. The anterior cingulate cortex and insula have been implicated in the affective evaluation of sensory stimulation, regulation of homeostatic responses, and visceral perception. In individuals with asthma and other stress-related conditions, these brain regions may be hyperresponsive to disease-specific emotional and afferent physiological signals, which may contribute to the dysregulation of peripheral processes, such as inflammation.

The role of p38 MAPK in rhinovirus-induced monocyte chemoattractant protein-1 production by monocytic-lineage cells

Viral respiratory infections are a major cause of asthma exacerbations and can contribute to the pathogenesis of asthma. Major group human rhinovirus enters cells by binding to the cell surface molecule ICAM-1 that is present on epithelial and monocytic lineage cells. The focus of the resulting viral infection is in bronchial epithelia. However, previous studies of the cytokine dysregulation that follows rhinovirus infection have implicated monocytic lineage cells in establishing the inflammatory environment even though productive infection is not a result. We have determined that human alveolar macrophages and human peripheral blood monocytes release MCP-1 upon exposure to human rhinovirus 16 (HRV16). Indeed, we have found p38 MAPK activation in human alveolar macrophages within 15 min of exposure to HRV16, and this activation lasts up to 1 h. The targets of p38 MAPK activation include transcriptional activators of the MCP-1 promoter. The transcription factor ATF-2, a p38 MAPK substrate, is phosphorylated 45 min after HRV16 exposure. Furthermore, IkappaBalpha, the inhibitor of the transcription factor NF-kappaB, is degraded. Prevention of HRV16 binding was effective in blocking p38 MAPK activation, ATF-2 phosphorylation, and MCP-1 release. This is the first report of a relationship between HRV16 exposure, MCP-1 release and monocytic-lineage cells suggesting that MCP-1 plays a role in establishing the inflammatory microenvironment initiated in the human airway upon exposure to rhinovirus.

Investigative bronchoprovocation and bronchoscopy in airway diseases

RATIONALE

Basic and clinical research strategies used for many lung diseases have depended on volunteer subjects undergoing bronchoscopy to establish access to the airways to collect biological specimens and tissue, perhaps with added bronchoprovocation in asthma syndromes. These procedures have yielded a wealth of important scientific information. Since the last critical review more than a decade ago, some of the techniques and applications have changed, and untoward events have occurred, raising safety concerns and increasing institutional review scrutiny.

OBJECTIVES AND METHODS

To reappraise these investigational methods in the context of current knowledge, the National Heart, Lung, and Blood Institute and the National Institute of Allergy and Infectious Diseases of the National Institutes of Health convened a working group to review these procedures used for airway disease research, emphasizing asthma and chronic obstructive pulmonary disease.

MAIN RESULTS

The group reaffirmed the scientific importance of investigative bronchoscopy and bronchoprovocation, even as less invasive technologies evolve. The group also considered the safety of bronchoscopy and bronchoprovocation with methacholine and antigen to be acceptable for volunteer subjects and patients, but stressed the need to monitor this closely and to emphasize proper training of participating medical research personnel. Issues were raised about vulnerable volunteers, especially children who need surrogates for informed consent.

CONCLUSION

This review of investigative bronchoscopy and bronchoprovocation could serve as the basis for future guidelines for the use of these procedures in the United States.

Contamination of nebulizer equipment with cockroach allergen: there's a bug in the system!

BACKGROUND

Physicians often have anecdotal reports of patients describing increased asthma symptoms after the use of nebulizers; however, there are few published reports of nebulizer-associated exacerbations.

OBJECTIVE

To present 2 cases of asthmatic children who experienced a life-threatening exacerbation of their symptoms after nebulizer use.

METHODS

Case 2's nebulizer was tested for cockroach allergen by washing the medication reservoir with 2 mL of sterile filtered 1% phosphate-buffered saline, 0.05% bovine serum albumin, and Tween 20 overnight with rotation. The patient's sealed albuterol nebulizer medication was used as a control. The control albuterol and test solutions were analyzed for Blattella germanica 1 and 2 allergens using a monoclonal antibody-based immunoenzymetric assay.

RESULTS

The reservoir from case 2 was found to have measurable levels of both Bla g 1 and Bla g 2. The control albuterol solution had no measurable cockroach allergen. An insect found in the nebulizer box of case 2 was identified as an infantile German cockroach.

CONCLUSIONS

Nebulizer use provides an opportunity for antigen exposure directly to small airways, which may lead to severe allergic reactions in patients using contaminated equipment.