Effects of inhaled fluticasone propionate on CTLA-4-positive CD4+CD25+ cells in induced sputum in mild asthmatics

Role of Regulatory T cells in Airway Inflammation in Asthma

Asthma is an allergic disease characterized by chronic airway inflammation, airway hyperresponsiveness (AHR), reversibility and remodeling. Inhaled corticosteroids (ICS) are effective in many patients with asthma. However, ICS are a controlling, but not but curative treatment, and there are still many patients with refractory and difficult-to-treat asthma. The evaluation of airway inflammation by induced sputum, non-specific AHR by methacholine, and asthmatic reactions by specific allergen challenge techniques are useful not only to investigate the pathogenesis of asthma but also to help develop new drugs for asthma management. Interactions between inflammation and regulation, such as between regulatory T cells (Tregs), and AHR were investigated using these techniques. The phenotypes are Tregs characterized by expression of the forkhead box P3 (Foxp3) and cytotoxic T-lymphocyte antigen 4 (CTLA4), which are potent mediators of dominant self-tolerance. Foxp3 and CTLA4 interact with each other. In patients with mild asthma, airway Tregs were decreased and airway eosinophilic inflammation was activated with accelerated AHR. Human asthmatic attack models by allergen challenge demonstrated that airway Tregs were decreased from the baseline with late asthmatic response (LAR) in patients with dual-responder asthma, and there was a significant correlation between change in airway Tregs and LAR. Airway Tregs were increased with escalation of interleukin-10 by ICS. The investigation of Tregs may lead to new strategies for management of asthma and other allergic diseases.

Adjustment of sensitisation and challenge protocols restores functional and inflammatory responses to ovalbumin in guinea-pigs

Introduction

Inhalation of antigen in atopic asthma induces early (EAR) and late asthmatic responses (LARs), inflammatory cell infiltration and airways hyperresponsiveness (AHR). Previously, we have established a protocol of sensitisation and subsequent ovalbumin (Ova) inhalation challenge in guinea-pigs which induced these 4 features (Smith & Broadley, 2007). However, the responses of guinea-pigs to Ova challenge have recently declined, producing no LAR or AHR and diminished EAR and cells. By making cumulative modifications to the protocol, we sought to restore these features.

Methods

Guinea-pigs were sensitised with Ova (i.p. 100 or 150 μg) on days 1 and 5 or days 1, 4 and 7 and challenged with nebulised Ova (100 or 300 μg/ml, 1 h) on day 15. Airway function was measured in conscious guinea-pigs by whole-body plethysmography to record specific airway conductance (sGaw). Airway responsiveness to aerosolized histamine (0.3 mM) was determined before and 24 h after Ova challenge. Bronchoalveolar lavage was performed for total and differential inflammatory cell counts. Lung sections were stained for counting of eosinophils.

Results

Lack of AHR and LAR with the original protocol was confirmed. Increasing the Ova challenge concentration from 100 to 300 μg/ml restored AHR and eosinophils and increased the peak of the EAR. Increasing the number of sensitisation injections from 2 to 3 did not alter the responses. Increasing the Ova sensitisation concentration from 100 to 150 μg significantly increased total cells, particularly eosinophils. A LAR was revealed and lymphocytes and eosinophils increased when either the Al(OH)₃ concentration was increased or the duration between the final sensitisation injection and Ova challenge was extended from 15 to 21 days.

Discussion

This study has shown that declining allergic responses to Ova in guinea-pigs could be restored by increasing the sensitisation and challenge conditions. It has also demonstrated an important dissociation between EAR, LAR, AHR and inflammation.

Effects of different up-dosing regimens for hymenoptera venom immunotherapy on serum CTLA-4 and IL-10

Background

Cytotoxic T lymphocyte associated antigen-4 (CTLA-4) is involved in the activation pathways of T lymphocytes. It has been shown that the circulating form of CTLA-4 is elevated in patients with hymenoptera allergy and can be down regulated by immunotherapy.

Objective

to assess the effects on CTLA-4 of venom immunotherapy, given with different induction protocols: conventional (6 weeks), rush (3 days) or ultra rush (1 day).

Methods

Sera from patients with hymenoptera allergy were collected at baseline and at the end of the induction phase. CTLA-4 and IL-10 were assayed in the same samples. A subset of patients were assayed also after 12 months of VIT maintenance.

Results

Ninety-four patients were studied. Of them, 50 underwent the conventional induction, 20 the rush and 24 the ultra-rush. Soluble CTLA-4 was detectable in all patients at baseline, and significantly decreased at the end of the induction, irrespective of its duration. Of note, a significant decrease of sCTLA-4 could be seen already at 24 hours. In parallel, IL-10 significantly increased at the end of the induction. At 12 months, sCTLA-4 remained low, whereas IL-10 returned to the baseline values.

Conclusions

Serum CTLA4 is an early marker of the immunological effects of venom immunotherapy, and its changes persist after one year of maintenance treatment.