Sputum cytokine mapping reveals an ‘IL-5, IL-17A, IL-25-high’ pattern associated with poorly controlled asthma.
Clin Exp Allergy. 2013 Sep;43(9):1009-17. doi: 10.1111/cea.12125.
Seys SF, Grabowski M, Adriaensen W, Decraene A, Dilissen E, Vanoirbeek JA, Dupont LJ, Ceuppens JL, Bullens DM.
Pneumology, Department of Clinical and Experimental Medicine, Catholic University of Leuven (KU Leuven), Leuven, Belgium.
BACKGROUND AND OBJECTIVE: Asthma is a heterogeneous disease with various clinical, inflammatory and molecular phenotypes. We studied sputum cytokine mRNA expression patterns in an unselected group of adult asthma patients to characterize the underlying inflammatory process.
METHODS: Differential cell counts and cytokine mRNA (quantified by real-time PCR) were analysed on sputum from 40 controls and 66 asthmatic adults. A ‘cytokine-high’ profile was defined if mRNA levels for that particular cytokine exceeded the 90th percentile value in the control population. Radar graphs were used to visualize cytokine profiles.
RESULTS: Sputum mRNA analysis confirmed heterogeneity of cytokine patterns among patients. Thirty-six patients (55%) had a Th2 cytokine pattern: ‘IL-5-high’ (n = 13), ‘IL-4-high’ (n = 17) or ‘IL-4- and IL-5-high’ (n = 6). The ‘IL-5-high’ asthma profile (n = 13) coincided with the ‘IL-25-high’ (10/13) and surprisingly also with the ‘IL-17A-high’ (11/13) profile. The ‘IL-5-/IL-25-/IL-17A-high profile was different from the ‘IL-4-high’ pattern. Patients with the ‘IL-5, IL-17A, IL-25-high’ pattern had significantly worse lung function parameters. Uncontrolled asthmatics [Asthma Control Test (ACT) < 20] had higher sputum IL-5, IL-17A and IL-25 mRNA levels compared to controlled asthmatics (P = 0.002; P = 0.002; P = 0.066) and uncontrolled asthma is more common among ‘IL-5- and IL-17A-high’ asthmatics compared to ‘IL-5-, IL-17A-low’ asthmatics (χ(2) = 3.7, P = 0.027; relative risk (RR): 1.8, 95% CI = 1.1-3.1).
CONCLUSIONS AND CLINICAL RELEVANCE: Patients with the ‘IL-5, IL-17A, IL-25-high’ airway inflammatory pattern are often uncontrolled asthmatics, despite daily treatment. It seems worthwhile to evaluate whether measuring sputum cytokine levels might be used to assess the response to increased doses of steroids in patients with asthma.
© 2013 John Wiley & Sons Ltd.
KEYWORDS: airway inflammation, asthma control, asthma phenotyping, cytokine, induced sputum
Asthma phenotyping has become very important since targeted therapies are currently being developed and tested for patients with asthma. The majority of patients (up to 85%) can be treated with corticosteroids to gain optimal control. However, a smaller group of patients is refractory to these steroids and might benefit from new anti-cytokine treatment. For the latter patients, a one size fits all approach does not apply. Our study provides a cross-sectional analysis of the cytokine expression in the airways of an unselected population of patients with asthma.
Induced sputum is a non-invasive technique to obtain cells from the lower airways. Normal sputum cytokine mRNA levels were determined in healthy control individuals. The 90th percentile value of the cytokine mRNA levels in the control population was used as a cut off value to define a ‘cytokine-high’ pattern. The patterns of aberrant sputum cytokine mRNA expression (‘cytokine-high’) were studied and visualized by radar graphs. Patients were allowed to continue their regular treatment.
Half of asthma patients were ‘IL-4-high’ and/or ‘IL-5-high’ (Th2-high asthmatics). However only a limited number of patients shared both ‘IL-4- and IL-5-high’ cytokine expression pattern (Figure 1). Instead, IL-5-high was associated with an ‘IL-17A-high’ and ‘IL-25-high’ pattern (Figure 1B). These patients had worse lung function parameters and more often uncontrolled asthma (Figure 2). Interestingly, the ‘IL-25-high’ expression pattern was restricted to patients with an ‘IL-5-high’ pattern. Analysis of the subgroup of steroid-naive asthmatics showed that these patients have an ‘IL-4-high’, ‘IL-6-high’ and ‘IL-22-high’ pattern.
We here thus confirm that a heterogeneous airway cytokine environment is present in patients with asthma. Patients with sputum a ‘IL-5-, IL-17A- and IL-25-high’ pattern had worse lung function and are more often uncontrolled, despite daily treatment. We hypothesize that patients with a high expression of a certain cytokine will benefit the most from anti-cytokine treatment to that particular cytokine. Detailed analysis of the cytokine profile in the airways of asthmatics will allow us in future to identify patients eligible to specific anti-cytokine treatment.
Figure 1. Radar plots of ‘IL-4-high’ (A) and ‘IL-5-high’ (B) patients. Radar plots were generated by presenting the proportion of “cytokine-high” patients (IL-4, IL-5, IL-6, IL-10, IL-17A, IL-22, IL-25, IL-29, IL-33, IFN-g, TNF and TSLP) as a set of points plotted along a set of axes radiating from a central point, and with the points connected by a line to visualize cytokine-high patients.
Figure 2. Lung function in relation to sputum IL-5, IL-17A and IL-25 mRNA. Cytokine mRNA was measured by RT-PCR and adjusted to b-actin. Sputum IL-5 protein levels were measured by ELISA. Patients were defined as uncontrolled asthmatics if Asthma Control Test (ACT) score was below 20/25 (39). Data were represented as median values with interquartile range. Differences between both groups were analyzed by Mann Whitney test.