Is the ebb of asthma due to the decline of allergic asthma? A prospective consultation-based study by the Swiss Sentinel Surveillance Network, 1999-2005

Omalizumab for Severe Asthma: Beyond Allergic Asthma

Different subsets of asthma patients may be recognized according to the exposure trigger and the frequency and severity of clinical signs and symptoms. Regarding the exposure trigger, generally asthma can be classified as allergic (or atopic) and nonallergic (or nonatopic). Allergic and nonallergic asthma are distinguished by the presence or absence of clinical allergic reaction and in vitro IgE response to specific aeroallergens. The mechanisms of allergic asthma have been extensively studied with major advances in the last two decades. Nonallergic asthma is characterized by its apparent independence from allergen exposure and sensitization and a higher degree of severity, but little is known regarding the underlying mechanisms. Clinically, allergic and nonallergic asthma are virtually indistinguishable in exacerbations, although exacerbation following allergen exposure is typical of allergic asthma. Although they both show several distinct clinical phenotypes and different biomarkers, there are no ideal biomarkers to stratify asthma phenotypes and guide therapy in clinical practice. Nevertheless, some biomarkers may be helpful to select subsets of atopic patients which might benefit from biologic agents, such as omalizumab. Patients with severe asthma, uncontrolled besides optimal treatment, notwithstanding nonatopic, may also benefit from omalizumab therapy, although currently there are no randomized double-blind placebo controlled clinical trials to support this suggestion. However, omalizumab discontinuation according to each patient's response to therapy and pharmacoeconomical analysis are questions that remain to be answered.

Th17 response is augmented in OVA-induced asthmatic mice exposed to HDM

Background

It is widely accepted that T helper 2 (Th2) cells, Th17 cells and their cytokines orchestrate the feature of asthma. However, most of studies on asthma mechanisms use a single allergen challenge model. Actually, humans are concurrently exposed to various allergens, and the mechanism of asthma with complex allergen exposure is less well defined. To explore whether the mechanism would be altered if asthma patients are re-exposed to another allergen, we exposed the chicken egg albumin (OVA) induced-asthmatic mice to house dust mite (HDM).

Material/Methods

HE staining was used to analyze pathologic variation in lung tissue of mice in each sub-group: control group, HDM alone group, OVA alone group and OVA+HDM group. Th1, Th2 and Th17 associated gene mRNA expressions were detected by quantitative PCR; associated cytokines were determined by ELISA or immunohistochemistry.

Results

The severe of inflammatory cell infiltration, the augmentation of Th17 and Th2 related gene mRNA expressions and the increase of Th17 associated cytokines expression were shown in OVA+HDM group in comparison with OVA alone group. However, Th2 related cytokines were increased with no significant difference in OVA+HDM group compared with OVA alone group.

Conclusions

We have found that Th17 response is connected with inflammation in the OVA-induced asthmatic mice exposed to HDM. When OVA-induced asthmatic mice are re-exposed to HDM, the pathomechanism is different from OVA alone exposure. HDM, indoor allergen, may be an important interferential factor for asthma therapy. It will give an important direction in the development of future asthma therapy.