Patients With Asthma Only Sensitized to Staphylococcus aureus Enterotoxins Have More Exacerbations, Airflow Limitation, and Higher Levels of Sputum IL-5 and IgE.

BACKGROUND: Staphylococcus aureus enterotoxins (SE) may act as superantigens and induce an intense T-cell activation, causing local production of polyclonal IgE and resultant eosinophil activation. OBJECTIVE: To assess whether asthma with sensitization to SE but not to common aeroallergens (AAs) displays different inflammatory characteristics. METHODS: We conducted a prospective study on a series of 110 consecutive patients with asthma recruited from the University Asthma Clinic of Liège. We compared clinical, functional, and inflammatory characteristics of this general population of patients with asthma categorized into 4 groups according to sensitization to AAs and/or SE. We also compared sputum supernatant cytokines in patients sensitized to SE or not. RESULTS: Patients with asthma sensitized only to AAs represented 30%, while 29% were sensitized to both AAs and SE. One-fifth of the population had no specific IgE. Sensitization to SE but not to AA (21%) was associated with later onset of disease, higher rate of exacerbations, nasal polyps, and more severe airway obstruction. As for airway type 2 biomarkers, patients presenting with specific IgE against SE displayed higher fractional exhaled nitric oxide, sputum IgE, and sputum IL-5 levels but not IL-4. We confirm that the presence of specific IgE against SE is associated with elevated serum IgE to levels well above those observed in patients sensitized only to AAs. CONCLUSIONS: Our study suggests that asthma specialists should measure specific IgE against SE during the phenotyping process because it may allow the identification of a subgroup of patients with more asthma exacerbations, more nasal polyposis and chronic sinusitis, lower lung function, and more intense type 2 inflammation.