Can clinical response to cyclosporin in chronic severe asthma be predicted by an in vitro T-lymphocyte proliferation assay?

[Diagnosis and treatment guidelines for difficult-to-control asthma in children]

Children suffering from difficult-to-control asthma (DCA) require frequent appointments with their physician, complex treatment regimes and often admissions to hospital. Less than 5% of the asthmatic population suffer this condition. DCA must be correctly characterised to rule out false causes of DCA and requires making a differential diagnosis from pathologies that mimic asthma, comorbidity, environmental and psychological factors, and analysing the factors to determine poor treatment compliance. In true DCA cases, inflammation studies (exhaled nitric oxide, induced sputum, broncho-alveolar lavage and bronchial biopsy), pulmonary function and other clinical aspects can classify DCA into different phenotypes which could make therapeutic decision-making easier.

Asthma refractory to glucocorticoids: the role of newer immunosuppressants

Asthma is orchestrated by cytokine products of activated T cells. Glucocorticoids are thought to ameliorate asthma at least partly through T cell inhibition. Consequently, other T cell immunomodulatory agents have been assessed for asthma therapy. Since these agents may have serious unwanted effects, attention has been focused on patients with severe asthma refractory to maximal topical, and additional systemic glucocorticoid therapy. Although gold salts show a modest but significant glucocorticoid-sparing effect in severe asthma, lung function is not improved and not all patients respond. The minimum duration of a valid trial of therapy is probably 6 months. Unwanted effects include dermatitis, hepatic dysfunction, proteinuria and interstitial pneumonitis. Meta-analysis of trials of methotrexate in oral glucocorticoid-dependent asthma have confirmed that concomitant weekly methotrexate for a minimum of 3 to 6 months enables significant (approximately 20%) overall reduction in oral glucocorticoid requirements, although only approximately 60% of patients show a significant response. There is little effect on lung function. Blood count and liver function must be monitored. Opportunistic infection is rare but potentially fatal. Cyclosporine, administered for at least 3 months, is effective in only a proportion of patients with oral glucocorticoid-dependent asthma, where it may improve disease severity and/or enable oral glucocorticoid dosage reductions. Regular monitoring of renal function, blood pressure and blood concentrations of cyclosporine is required. The evidence that intravenous immunoglobulin (Ig) is of any benefit in patients with glucocorticoid-dependent asthma is at present equivocal. The therapy is expensive and associated with a high incidence of unwanted effects (fever, aseptic meningitis, urticaria). The macrolides tacrolimus (FK506) and sirolimus (rapamycin) have end effects similar to those of cyclosporine. Brequinar sodium, mycophenolate mofetil and leflunomide are inhibitors of de novo synthesis of pyrimidines and purines, to which T cells are particularly sensitive. Such drugs may in theory be beneficial for therapy of patients with oral glucocorticoid-dependent asthma. Humanized anti-CD4, anti-IgE and anti-interleukin (IL)-5 monoclonal antibodies, and other cytokine inhibitors such as soluble IL-4 receptor have entered early trials. The worth of current immunomodulatory drugs is limited since: (i) not all patients respond, and response cannot be predicted a priori; (ii) the high incidence of unwanted effects makes it difficult to assess overall benefit/risk ratios; (iii) there is increased risk of opportunistic infection and (theoretically) neoplasia; (iv) there are many relative and absolute contraindications to therapy; and (v) there is lack of knowledge about the long-term effects, beneficial or otherwise, of therapy.

Pharmacology of airway inflammation in asthma and COPD

The current asthma therapies are not cures and symptoms return soon after treatment is stopped even after long term treatment. Although inhaled glucocorticoids are highly effective in controlling airway inflammation in asthma, they are ineffective in the small group of patients with glucocorticoid-dependent and -resistant asthma. With very few exceptions, COPD is caused by tobacco smoking, and smoking cessation is the only truly effective treatment of COPD available. Current pharmacological treatment of COPD is unsatisfactory, as it does not significantly influence the severity of the disease or its natural course. Glucocorticoids are scarcely effective in COPD patients without concomitant asthma. Bronchodilators improves symptoms and quality of life, in COPD patients, but, with the exception of tiotropium, they do not significantly influence the natural course of the disease. Theophylline is the only drug which has been demonstrated to have a significant effect on airway inflammation in patients with COPD. Here we review the pharmacology of currently used antiinflammatory therapies for asthma and COPD and their proposed mechanisms of action. Recent understanding of disease mechanisms in severe steroid-dependent and -resistant asthma and in COPD, has lead to the development of novel compounds, which are in various stages of clinical development. We review the current status of some of these new potential drugs.

The role of T lymphocytes in the pathogenesis of asthma

There is considerable evidence to support a role for T cells in asthma, particularly the involvement of T(H)2 cells both in atopic allergic asthma and in nonatopic and occupational asthma. There might also be a minor contribution from T(C)2 CD8+ T cells. Several T(H)2 cytokines have the potential to modulate airway inflammation, particularly IL-13, which induces airway hyperresponsiveness independently of IgE and eosinophilia in animal models. The identification of transcription factors controlling T(H)1 and T(H)2 development further support the T(H)2 hypothesis because GATA3 is overexpressed and T-bet is underexpressed in the asthmatic airway. Specific T cell directed immunotherapy might allow induction, modulation, or both of T-cell responses, and elucidation of the mechanisms of regulatory T cells might allow further optimization of immunotherapy. Recent advances in our understanding of dendritic cell function in directing T-cell responses might uncover further therapeutic targets. The efficacy of cyclosporin A and anti-CD4 treatment in patients with chronic severe asthma argues for continued T-cell involvement, but whether remodeling contributes to pathology inaccessible to anti-inflammatory treatment or T-cell immunotherapy will be an important future question.