Asthma: defining of the persistent adult phenotypes

Targeting TNF-alpha: a novel therapeutic approach for asthma

Approximately 5% to 10% of patients with asthma have severe disease that is refractory or poorly responsive to inhaled corticosteroid therapy. These patients represent an important unmet clinical need because they experience considerable morbidity and mortality and consume a disproportionately large amount of health care resources. TNF-alpha is a proinflammatory cytokine that has been implicated in many aspects of the airway pathology in asthma. Evidence is emerging to suggest that it might play an important role in severe refractory disease. The development of novel TNF-alpha antagonists has allowed us to test the role of this cytokine in vivo. Preliminary studies have demonstrated an improvement in asthma quality of life, lung function, and airway hyperresponsiveness and a reduction in exacerbation frequency in patients treated with anti-TNF-alpha therapy. However, there is marked heterogeneity in response, suggesting that benefit is likely to be reserved to a small subgroup. Importantly, where efficacy is reported, this also needs to be considered in the context of concerns about the safety of anti-TNF-alpha therapies. Therefore the challenge for clinicians is to evaluate the risk/benefit ratio of these therapies in individual patients with asthma.

American Thoracic Society Annual International Congress

The 2007 International Congress of the American Thoracic Society (ATS) was held in San Francisco, California. It is one of the most important conferences in pulmonary medicine. It provides an annual forum for scientists and clinical investigators from academia and non-university institutions including private practices and pharmaceutical companies to share information on many aspects of pulmonary and critical care medicine, sleep disorders, pulmonary infectious diseases, malignancies of the chest and numerous aspects of diagnostic and interventional procedures in that field. This year approximately 5500 abstracts were presented and approximately 15,000 participants attended the ATS congress. Research areas covered all aspects of pulmonary diseases. Traditionally obstructive pulmonary diseases (e.g., chronic obstructive pulmonary disease and asthma) were again the main focus. The general impression from the meeting was that the focus this year shifted more to basic research of pulmonary diseases, new diagnostic techniques and tools to approximate disease progression rather than presenting new drugs for treatment. Furthermore, new ATS policies for permitting industry sponsored satellite symposia - among other possible reasons - seemed to discourage pharmaceutical companies organizing such evening meetings when compared with previous ATS conferences. When up to five of such symposia used to be normal per night in previous years, just three of these sponsored sessions per night, which were labeled as 'evening postgraduate seminars', were offered at this meeting.

Lipoxin A4 levels in asthma: relation with disease severity and aspirin sensitivity

BACKGROUND

Lipoxin (LX) A4, an endogenous anti-inflammatory eicosanoid, has been found to be low in patients with severe asthma. However, few studies also suggested more diminished LX A4 levels in aspirin-exacerbated respiratory disease (AERD) when compared with aspirin-tolerant asthma (ATA). It is, therefore, currently not clear whether the asthma severity or the presence of AERD has a primary role in the disturbed LX metabolism.

OBJECTIVE

To detect LX A4 and 15-epi-LX A4 levels in asthma patients with and without AERD of comparable severity.

METHODS

The study groups consisted of 22 subjects with AERD, 22 subjects with ATA and 10 volunteers without asthma and aspirin sensitivity. Whole-blood samples were stimulated with calcium ionophore, A23187 (5 x 10(-5) m) and A23187 (5 x 10(-5) m)+aspirin (10(-4) m). LX A4 and 15-epi-LX A4 levels were analysed by the enzyme immune assay method.

RESULTS

Severe asthma patients in both AERD [0.5 (0.8)] ng/mL and ATA [0.5 (0.45) ng/mL] groups showed diminished generation for LX A4 to stimulation with A23187 in comparison with other severity degrees in their groups (P=0.02 and 0.046, respectively). LX A4 generation in both severe groups was comparable with each other (P>0.05). Although severe cases with AERD showed a diminished capacity to generate 15-epi-LX A4, this did not reach statistical significance.

CONCLUSION

This study indicated that diminished LX A4 generation was unique to severe asthma phenotype regardless of comorbid aspirin sensitivity. Clinical Implications Lower LX A4 levels in severe asthma would suggest a possibility for LX analogues as future treatment options in these patients.

[Hypereosinophilic asthma]

Although moderate airway infiltration by eosinophils is present in the eosinophilic inflammatory phenotype of asthma, hypereosinophilic asthma differs in its frankly elevated levels of eosinophils in the blood, induced sputum, and bronchoalveolar lavage. Some etiologic pitfalls may be tricky especially wheezing in eosinophilic pneumonia induced by drugs or parasitic infections. Idiopathic chronic eosinophilic pneumonia is associated with asthma in most cases. Churg-Strauss syndrome has asthma as a basic feature, but true systemic vasculitis with antineutrophil cytoplasmic autoantibodies is not always present. Systemic corticosteroids are the mainstay of treatment of most hypereosinophilic asthma patients.

Airway remodeling and lack of bronchodilator response in steroid-resistant asthma

BACKGROUND

Steroid-resistant (SR) asthma is characterized by airway inflammation that fails to resolve despite treatment with corticosteroids, raising concerns that resistance to steroid therapy in asthma could lead to airway remodeling.

OBJECTIVE

We sought to determine whether SR asthma is accompanied by decreased airflow reversibility and could lead to airway remodeling.

METHODS

Spirometric results were evaluated for 40 asthmatic patients defined as having SR or steroid-sensitive (SS) asthma on the basis of a 1-week course of oral prednisone. Twenty-three asthmatic patients underwent bronchoscopy with collection of bronchoalveolar lavage (BAL) fluid to analyze markers of airway remodeling in BAL fluid and cells.

RESULTS

Prednisone significantly improved FEV(1) percent predicted in SS asthma (62.0% +/- 10.9% [mean +/- SD] to 79.4% +/- 11.3%, P < .001) but not in SR asthma (66.9% +/- 10.0% to 65.9% +/- 12.1%). The bronchodilator response was significantly greater in the SS than in the SR group (Delta FEV(1) percent predicted, 33.5% +/- 22.5% vs 15.2% +/- 7.9%; P = .001), regardless of inhaled corticosteroid use. No difference in amounts of matrix metalloproteinase (MMP) 9, PMN elastase, or vascular endothelial growth factor was found in BAL fluid from both groups. Tissue inhibitor of metalloproteinases (TIMP) 1 levels were, however, significantly less in BAL fluid of patients with SR asthma compared with those in patients with SS asthma (921.9 +/- 313.4 vs 2267.0 +/- 456.8 pg/mL, P < .05), resulting in significantly higher MMP-9/TIMP-1 ratios in the BAL fluid of patients with SR asthma (0.24 +/- 0.04 vs 0.11 +/- 0.03, P < .01). Finally, dexamethasone treatment induced TIMP-1 mRNA in BAL fluid cells from patients with SS asthma (P < .01) but not in cells from patients with SR asthma.

CONCLUSION

Bronchodilator reversibility is impaired in SR asthma and is associated with a shift in MMP-9/TIMP-1 ratio caused by inability of steroids to enhance TIMP-1 production, potentially promoting proteolytic activity in airways of patients with SR asthma and contributing to chronic airway remodeling.

CLINICAL IMPLICATIONS

SR asthma might lead to irreversible airways disease.

Respiratory syncytial virus synergizes with Th2 cytokines to induce optimal levels of TARC/CCL17

Respiratory syncytial virus (RSV) is a ubiquitous virus that preferentially infects airway epithelial cells, causing asthma exacerbations and severe disease in immunocompromised hosts. Acute RSV infection induces inflammation in the lung. Thymus- and activation-regulated chemokine (TARC) recruits Th2 cells to sites of inflammation. We found that acute RSV infection of BALB/c mice increased TARC production in the lung. Immunization of BALB/c mice with individual RSV proteins can lead to the development of Th1- or Th2-biased T cell responses in the lung after RSV infection. We primed animals with a recombinant vaccinia virus expressing either the RSV fusion (F) protein or the RSV attachment (G) protein, inducing Th1- and Th2-biased pulmonary memory T cell responses, respectively. After RSV infection, TARC production significantly increased in the vaccinia virus G-primed animals only. These data suggest a positive feedback loop for TARC production between RSV infection and Th2 cytokines. RSV-infected lung epithelial cells cultured with IL-4 or IL-13 demonstrated a marked increase in the production of TARC. The synergistic effect of RSV and IL-4/IL-13 on TARC production reflected differential induction of NF kappa B and STAT6 by the two stimuli (both are in the TARC promoter). These findings demonstrate that RSV induces a chemokine TARC that has the potential to recruit Th2 cells to the lung.

[Environmental factors for asthma severity and allergy: results from the EGEA study]

INTRODUCTION

EGEA (Epidemiological study on the genetics and environment of asthma, bronchial hyperresponsiveness and atopy), a case control and family study including 2048 individuals, was initiated to look for environmental and genetic risk factors for asthma. A synthesis of the results obtained since 2002 on phenotypic and environmental aspects of asthma severity and allergy are presented in this article.

METHODS AND RESULTS

The results support a role for hormonal factors in asthma severity and in various allergic markers of asthma. A greater body mass index was related to a more severe asthma in women with early menarche. Associations between markers of allergy (eosinophils, IgE and atopy) and hormonal dependent events in women (premenstrual asthma, menopause and oral contraceptive use) have been found. In asthmatics, exposure to agents known to be associated with occupational asthma, active and passive smoking were associated with an increased clinical asthma severity score. The study underlines the protective role of country living and exposure to pets in early life on allergy markers in adulthood, supporting the hygiene hypothesis.

CONCLUSIONS

New hypothesis will be tested in the near future from the second stage of this survey.

Evidence for a pleiotropic QTL on chromosome 5q13 influencing both time to asthma onset and asthma score in French EGEA families

Although many genome screens have been conducted for asthma as a binary trait, there is limited information regarding the genetic factors underlying variation of asthma expression. Phenotypes related to variable disease expression include time to asthma onset and variation in clinical expression as measured by an asthma score built from EGEA data. A recent genome scan conducted for this score led to detection of a new region (18p11) not revealed by analysis of dichotomous asthma. Our goal was to characterize chromosomal regions harboring genes underlying time to asthma onset and to search for pleiotropic QTL influencing both time to asthma onset and the asthma score. We conducted a genome-wide linkage screen for time to asthma onset, modeled by martingale residuals from Cox survival model, in EGEA families with at least two asthmatic sibs. This was followed by a bivariate linkage scan of these residuals and asthma score. Univariate linkage analysis was performed using the Maximum Likelihood Binomial method that we extended to bivariate analysis. This screen revealed two regions potentially linked to time to asthma onset, 1p31 (LOD = 1.70, P = 0.003) and 5q13 (LOD = 1.87, P = 0.002). Bivariate linkage analysis led to a substantial improvement of the linkage signal on 5q13 (P = 0.00007), providing evidence for a pleiotropic QTL influencing both variation of time to asthma onset and of clinical expression. Use of quantitative phenotypes of variable disease expression and suitable statistical methodology can improve the power to detect new regions harboring genes which may play an important role in onset and course of disease.

Respirology year-in-review 2006: Basic science

The year 2006 was a good year for basic science publications in Respirology with a lot of the studies being relevant to clinical practice. In this respect many of the publications focused on biomarkers of disease and so much so that these have been discussed at the end of this review. The majority of manuscripts are related to airway diseases, respiratory infections, interstitial lung diseases and lung cancers, and are discussed under these headings.

Anti-IgE and chemotherapy: a critical appraisal of treatment options for severe asthma

In this narrative review the scientific rationale for the development of a therapeutic modality for asthma based on decreasing the circulating and cell-bound levels of immunoglobulin-E (IgE) is outlined. The one drug that has so far entered clinical practice to do this is a humanised monoclonal antibody to the Fc portion of the IgE molecule, omalizumab. It is highly effective in reducing IgE blood levels and its established mode of delivery is by subcutaneous injection. The clinical trial development of omalizumab is reviewed and the published data and claims for its efficacy and role in clinical practice is critically appraised. The target group of omalizumab has become focused on severe asthmatics who are still symptomatic after being administered with high-dose inhaled corticosteroids plus long-acting beta-agonists. The strongest evidence for effect is in those with frequent severe exacerbations.

Quantitative sputum cell counts as a marker of airway inflammation in clinical practice

PURPOSE OF REVIEW

Bronchitis, meaning airway inflammation, is an important component of airway disease. Yet respirologists and allergists, who have stressed the importance of measurements of airway function, have been slow to introduce airway inflammation measurements into clinical practice. Of the measurements available, quantitative sputum cell counts have the most clinical value. This article provides additional information on this topic from studies published in 2005 and 2006.

RECENT FINDINGS

Airway diseases are heterogeneous within patients in terms of the disease present and the type of airway inflammation. Quantitative sputum cell counts (total cell count as well as the differential) identify noneosinophilic, mainly neutrophilic, probably infective exacerbations as common in patients with asthma and chronic obstructive pulmonary disease that may be unresponsive to corticosteroid treatment. In contrast, measurements of sputum eosinophils can be used to guide the minimum dose of corticosteroid required to control eosinophilic bronchitis and reduce eosinophilic exacerbations.

SUMMARY

Measurements of quantitative sputum cell counts need to be made available, initially by tertiary care centres, to diagnose bronchitis in airway disease and to optimize treatment. Examination of how these are complemented by indirect measures of airway inflammation, specifically exhaled nitric oxide and airway hyperresponsiveness to stimuli acting indirectly through mediator release, requires further investigation.

The reclassification of asthma based on subphenotypes

PURPOSE OF REVIEW

Despite asthma being widely regarded as a heterogeneous disease, a consensus for an accurate system of classification has not been agreed. Recent studies have suggested that the recognition of subphenotypes of asthma based on the pattern of airway inflammation may be particularly useful in increasing our understanding of the disease. The present review discusses the important literature in this field, placing current work in its historical context.

RECENT FINDINGS

The use of noninvasive markers of airway inflammation has suggested the presence of four distinct phenotypes: eosinophilic, neutrophilic, mixed inflammatory and paucigranulocytic asthma. Recent studies suggest that these subgroups may differ in their aetiology, immunopathology and response to treatment. Several studies have focused on refractory asthma as a distinct phenotype with evidence of a more distal pattern of airway inflammation and of upregulation of the tumour necrosis factor-alpha axis. Finally, novel treatment approaches targeted at specific patterns of airway inflammation are emerging, making an appreciation of subphenotypes particularly relevant.

SUMMARY

The present review will discuss limitations to current classification systems, identify key current studies based on identifying inflammatory subphenotypes and provide suggestions for a novel approach that may further improve our understanding in this area.

Asthma control or severity: that is the question

In the first National Heart Lung and Blood Institute and Global Initiative for Asthma (GINA) guidelines, the level of symptoms and airflow limitation and its variability allowed asthma to be subdivided by severity into four subcategories (intermittent, mild persistent, moderate persistent, and severe persistent). It is important to recognize, however, that asthma severity involves both the severity of the underlying disease and its responsiveness to treatment. Thus, the first update of the GINA guidelines defined asthma severity depending on the clinical features already proposed as well as the current treatment of the patient. In addition, severity is not a fixed feature of asthma, but may change over months or years, whereas the classification by severity suggests a static feature. Moreover, using severity as an outcome measure has limited value in predicting what treatment will be required and what the response to that treatment might be. Because of these considerations, the classification of asthma severity is no longer recommended as the basis for treatment decisions, a periodic assessment of asthma control being more relevant and useful.