J Allergy Clin Immunol. 2012 Aug;130(2):376-81.e8.

Specific IgE against Staphylococcus aureus enterotoxins: an independent risk factor for asthma

C Bachert1, MD PhD, K van Steen2,3,5, PhD, N Zhang1, MD, G Holtappels1, T Cattaert2,3, PhD, B Maus2,3,5, PhD, R Buhl4, MD PhD, C Taube4, 9, MD PhD, S Korn4, MD, M Kowalski6, MD, J Bousquet7, MD PhD, P Howarth8, MD


1) Upper Airway Research Laboratory (URL), Ghent University Hospital, Belgium

2) Systems and Modelling Unit, Montefiore Institute, University of Liège, Liège, Belgium

3) Bioinformatics and Modelling, GIGA-Research, University of Liège, Liège, Belgium

4) Pulmonary Department, Mainz University Hospital, Germany

5) Center for Medical Genetics, Ghent University Hospital, Belgium

6) Department of Allergy, Immunology and Rheumatology, Medical University of Lódź, Poland

7) University Hospital and INSERM 1080, Montpellier, France

8) Clinical and Experimental Sciences, Faculty of Medicine, Southampton University and National Institute of Health Respiratory Biomedical Research Unit, Southampton General Hospital, Southampton, UK

9) Leiden University Medical Center, Department of Pulmonology, Leiden, the Netherlands



The role of IgE in severe asthma is not fully understood. We sought to investigate whether IgE to Staphylococcus aureus enterotoxins might be relevant to disease severity in adult asthmatic patients. Specific IgE antibody concentrations in serum against enterotoxins, grass pollen (GP), and house dust mite allergens and total IgE levels were measured in adult cohorts of 69 control subjects, 152 patients with non-severe asthma, and 166 patients with severe asthma. Severe asthma was defined as inadequately controlled disease despite high-dose inhaled corticosteroids plus at least 2 other controller therapies, including oral steroids. Enterotoxin IgE positivity was significantly greater in patients with severe asthma (59.6%) than in healthy control subjects (13%, P < .001). Twenty-one percent of patients with severe asthma with enterotoxin IgE were considered non-atopic. Logistic regression analyses demonstrated significantly increased risks for enterotoxin IgE–positive subjects to have any asthma (OR, 7.25; 95% CI, 2.7-19.1) or severe asthma (OR, 11.09; 95% CI, 4.1-29.6) versus enterotoxin IgE–negative subjects. The presence of GP or house dust mite IgE antibodies was not associated with either significantly increased risk for asthma or severity. Oral steroid use and hospitalizations were significantly increased in patients with enterotoxin IgE and non-atopic asthma. GP IgE was associated with a higher FEV1 percent predicted value, and enterotoxin IgE was associated with a lower FEV1 percent predicted value. Staphylococcal enterotoxin IgE antibodies, but not IgE against inhalant allergens, are risk factors for asthma severity. We hypothesize that the presence of enterotoxin IgE in serum indicates the involvement of staphylococcal superantigens in the pathophysiology of severe asthma.

PMID: 22738677



Staphylococcus aureus (SA) frequently colonizes the nostrils; up to a third of individuals in Europe are life-long carriers of coagulase-positive SA. In some chronic rhinosinusitis (CRS) patients, particularly those with nasal polyps (CRSwNP), SA also colonizes the middle nasal meatus, which is a key region at the entrance to the sinuses. Colonization rates were as high as 67% and 87% for CRSwNP patients with asthma and aspirin sensitivity, respectively. SA may not only colonize the mucosa, but particularly in patients with polyp may also form biofilms adherent to the mucosa. Using peptide nucleic acid-fluorescence in situ hybridization, we recently demonstrated the presence of intramucosal SA especially in polyp tissue from patients with aspirin sensitivity, AERD; these bacteria were located intracellularly (1). SA recovered from the nose can synthesize and release a wide range of enterotoxins, among them the well-studied classical staphylococcal enterotoxins (SEs) SEA, SEC and SEE and toxic shock syndrome toxin-1 (TSST-1). SEs, also known as superantigens, are able to activate T cells by binding to the variable β-chain of the T cell receptors, which allows the polyclonal activation of a substantial number of T cells present in the tissue. Furthermore, SEs may activate B cells, eosinophils, epithelial cells and others, resulting in a cytokine storm locally in the tissue and the generation of a strong inflammatory response. We propose that SEs released in small amounts into the mucosal tissue by SA residing in mucosal cells leads to persistent stimulation of the local immune system, which creates changes in the innate and adaptive immune response to allow the long-term survival of the bacteria at the diseased airway. The creation of a severe Th2 bias within the tissue is part of this strategy (2).

Using animal models, it has been demonstrated that SEs are able to aggravate airway inflammation in sensitized mice. SEB is able to break the normally developing tolerance and facilitate sensitization in mice when given intra-nasally together with an allergen. Data suggest that SEB not only aggravates airway inflammation, but may also facilitate IgE formation in animals. There is evidence to suggest that such effects can also been found in human nasal mucosa. We used an ex vivo human mucosal model to study the effects of SA-derived SEB and staphylococcal protein A (3). Protein A stimulation of the mucosa resulted in significant degranulation of mast cells, whereas SEB stimulation over a period of 24 h induced considerable release of pro-inflammatory and Th2-associated cytokines including IL-4, IL-5 and IL-13, and also induced the release of IL-2, which further activates T effector cells. These cytokines skewed the T cell responses even more towards the Th2 direction, contributing to the persistent severe predominantly Th2-biased inflammation in polyp disease.

The activation of B cells and their transformation into plasma cells can also be shown in nasal polyp tissue, resulting in mucosal IgE concentrations higher than 5000 kU/l IgE. Hundreds of allergen-specific IgE antibodies may be formed as part of the total IgE concentration in tissue and serum, including IgE antibodies against SEs (SE-IgE). When mucosal tissues were stimulated with anti-IgE, and inhalant allergens such as house dust mite, grass pollen or SEB, mast cell activation occurred dependent on the local IgE antibodies present, but independent from systemic IgE specificities (4). Thus, house dust mite allergen was able to degranulate nasal polyp mast cells in the absence of specific IgE to mites in serum; this is an example of truly local mast cell activation.

About 37% of mucosal tissue samples of Caucasian CRSwNP contain IgE antibodies against SEs, associated with significantly increased total IgE and ECP concentrations. A hypothesis-free modelling approach was performed in two ways, based on categorical (a marker is present/not present) or on continuous values (quantitative analysis) (5). The categorical approach identified SE-IgE as positive and interferon (IFN)-g as negative determinants for comorbid asthma in CRSwNP patients; the prevalence of comorbid asthma was significantly increased among those individuals who showed SE-IgE positivity in nasal polyp tissue (57%) compared to SE-IgE-negative patients (20%, P<0.01). Using the continuous approach, high total IgE and ECP concentrations within the polyp tissue were found to be the main positive predictors. As indicated above, both of these factors are up-regulated by SEs. These observations add support to the impact of staphylococcal superantigens on airway disease and furthermore extend their role to include severity of disease and lower airway involvement.

We therefore extended our studies involving subjects with non-severe and severe asthma disease; severe asthma was defined as inadequately controlled disease despite high-dose inhaled corticosteroids plus at least two other controller therapies including oral steroids (6). SE-IgE positivity was significantly more common in patients with severe asthma than in healthy controls, and logistic regression analyses demonstrated a significantly increased risk of any asthma in SE-IgE-positive subjects with an odds ratio (OR) of 7.2 [95% confidence interval (CI) 2.7–19.1], and of severe asthma with an OR of 11.1 (95% CI 4.1–29.6), compared with SE-IgE-negative subjects. By contrast, the presence of grass pollen or house dust mite IgE antibodies in serum was not associated with either increased risk of asthma or severity in this study. Thus, this study confirmed for the lower airways what we have observed for the upper airways!

Of interest, 21% of severely asthmatic patients with SE-IgE were considered non-atopic based on the absence of IgE to grass pollen and house dust mites and a negative skin prick test to the most frequent inhalant allergens; these patients typically had a total serum IgE level above normal values and reported a late onset of disease (Table 1). About 60–80% of patients with severe asthma were SE-IgE positive, and about one-third of these patients are non-atopic, suggesting that superantigens may be the cause of the so-called intrinsic form of asthma!

Omalizumab is an anti-IgE antibody with proven efficacy in severe asthma, only indicated for patients with an allergen-induced disease. However, it was challenging to find out whether omalizumab would also be effective in SE-IgE-positive but otherwise non-atopic patients with severe airway disease. We therefore investigated the clinical efficacy of omalizumab in patients with severe nasal polyps and comorbid asthma, with about half of the patients being allergic (7). Clinical efficacy of therapy was assessed by nasal endoscopy, sinus CT scan, evaluation of nasal and asthma symptoms, and sinus- and asthma-related quality-of-life questionnaires. We found a significant effect on the primary endpoint, a substantial decrease in total polyp score after 16 weeks, in the omalizumab group compared to baseline, which was confirmed by CT scan. Omalizumab also had a significant beneficial effect on upper and lower airway symptoms (nasal congestion, anterior rhinorrhoea, loss of sense of smell, wheezing and dyspnoea) and on the asthma-related quality-of-life score; this effect on lower and upper airway symptoms was irrespective of the atopic status of the patient. In summary, omalizumab demonstrated clinical efficacy for the treatment of nasal polyposis with comorbid asthma, supporting the importance and functionality of polyclonal IgE formation and SE-IgE in atopic and non-atopic individuals. Larger studies in patients with severe asthma are needed to confirm these data, differentiating between classically atopic and non-atopic SE-IgE-positive patients, to provide new therapeutic options for non-atopic subjects with upper, lower and combined severe airway disease involving anti-IgE strategies.

In summary, we hypothesize that the presence of enterotoxin IgE in serum indicates the involvement of staphylococcal superantigens in the pathophysiology of severe asthma. This involvement is most likely to be mediated by both superantigen effects on T cell activation, with a bias towards Th2 cells and against T regulatory cells, and the production of IgE in mucosal plasma cells.



1) Corriveau MN, Zhang N, HoltappelsG, Van Roy N, Bachert C. Detection of Staphylococcus aureus in Nasal Tissue with Peptide Nucleic Acid – Fluorescence In Situ Hybridization. Am J Rhinol Allergy 2009;23:461-465

2) Bachert C, P Gevaert, G Holtappels, SGO Johansson, P van Cauwenberge. Total and specific IgE in nasal polyps is related to local eosinophilic inflammation. J Allergy Clin Immunol 2001;107:607-614

3) Patou J, Van Zele T, Gevaert P, Holtappels G, Van Cauwenberge P, Bachert C. Staphylococcus aureus enterotoxin B, protein A and lipoteichoic acid stimulations in nasal polyps. J Allergy Clin Immunol. 2008;121:110-5

4) Zhang N, G Holtappels, P Gevaert, J Patou, B Dhaliwal, H Gould, C Bachert. Mucosal tissue polyclonal IgE is functional in response to allergen and SEB. Allergy 2011;66:141-8

5) Bachert C, Nan Zhang, Gabriele Holtappels, Lizzi De Lobel, Paul can Cauwenberge, Liu Shixi, Ping Lin, Jean Bousquet, Kristel van Steen. Presence of IL-5 protein and IgE-antibodies to staphylococcal enterotoxins in nasal polyps is associated with co-morbid asthma. JACI 2010;126:962-8

6) Bachert C, K van Steen, N Zhang, G Holtappels, T Cattaert, B Maus, R Buhl, C Taube, S Korn, M Kowalski, J Bousquet, P Howarth. Specific IgE against Staphylococcus aureus enterotoxins: an independent risk factor for asthma. J Allergy Clin Immunol. 2012 Aug;130(2):376-381

7) Gevaert P, L Calus, T Van Zele, K Blomme, N De Ruyck, W Bauters, P Hellings, G Brusselle, D De Bacquer, P van Cauwenberge, C Bachert. Omalizumab is effective in allergic and non-allergic patients with nasal polyposis and co-morbid asthma. J Allergy Clin Immunol 2013;131:110-116


Table 1.

Claus Bachert-table1

Differentiation of patients with severe asthma based on atopy (IgE antibodies to grass and/or house dust mite allergens) and Staphylococcus aureus enterotoxin-specific IgE in serum. Atopic subjects report a significantly earlier onset of disease compared to non-atopic subjects; specifically SE-IgE positive severe asthmatics show a late onset of disease (“intrinsic asthma”). The combination of atopy and SE-IgE positivity significantly increases serum total IgE concentrations; however, also non-atopic SE-IgE positive subjects have increased serum IgE values. Lung function and body mass index were not different between groups. From: Bachert C, Zhang N. Chronic rhinosinusitis and asthma: novel understanding of the role of IgE “above atopy”. J Intern Med. 2012;272:133-43


C. Bachert is also affiliated with the Division of ENT Diseases, Clintec, Karolinska Institutet, Stockholm, Sweden. Supported by grants to C.B. from the Flemish Scientific Research Board, FWO, nos. A12/5-HB-KH3 and G.0436.04, and the Interuniversity Attraction Poles Programme (IUAP), Belgian state, Belgian Science Policy P6/35, and to P.H. from the UK Medical Research Council, G0800649 (Wessex Severe Asthma Cohort), and by the Global Allergy and Asthma European Network (GA2LEN). T.C. is a Postdoctoral Researcher of the Fonds de la Recherche Scientifique (FNRS). T.C. and K.S. acknowledge research support by the Belgian Network BioMAGNet (Bioinformatics and Modelling: from Genomes to Networks), funded by the Interuniversity Attraction Poles Programme (Phase VI/4), and by the IST Programme of the European Community under the PASCAL2 Network of Excellence (Pattern Analysis, Statistical Modelling and Computational Learning), IST-2007-216886.



Claus Bachert, MD, PhD

Upper Airway Research Laboratory (URL),

Ghent University Hospital

De Pintelaan 185, 9000 Ghent, Belgium

Tel 0032 9240 6423    Fax 0032 9240 4993

e-mail: claus.bachert@ugent.be

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