Sensitisation to Staphylococcus aureus enterotoxin – a marker of an autoimmune phenotype of severe asthma?

<bold>Background:</bold> Sensitisation to Staphylococcus Aureus by use of enterotoxin A/B specific IgE (+SE-IgE) is associated with severity in several eosinophilic diseases such as asthma and nasal polyps, but may also represent a specific asthma phenotype with a higher degree of airway autoimmunity. <bold>Aim:</bold> To describe the prevalence of sensitisation to SE-IgE among patients with severe asthma, and the association with eosinophilic inflammation and airway autoimmunity. <bold>Methods:</bold> In a population of 120 patients with severe asthma, serum staphylococcal enterotoxin A and/or B specific IgE was assessed. Sensitisation was defined as value of >0.1 kU (+SE-IgE). Key T2 biomarkers and clinical characteristics were investigated. Airway autoimmunity was defined as either positive sputum antibodies against eosinophil peroxidase (anti-EPX) or/and against macrophage receptor with collagenous structure (anti-MARCO). <bold>Results:</bold> A total of 28.3% of patients were +SE-IgE. +SE-IgE were more likely to be positive for autoimmunity than ÷SE-IgE (p=0.01). 34% of +SE-IgE patients were positive for autoimmunity vs 10% of ÷SE-IgE. +SE-IgE also had a higher total IgE in kU/L (median 436 (87-13500) vs ÷SE-IgE (median 69 (1-1830)) (p<0.001)), as well as higher blood eosinophil count in 10⁹/L (+SE-IgE: median 0.28 (0.02-1.47) vs ÷SE-IgE: median 0.18 (0.01-1.10) (p=0.03)) and sputum eosinophil % (median 5.88 (0-92)) vs (median 1.50 (0-88) respectively (p=0.01)). <bold>Conclusion:</bold> This study showed for the first time a possible link between autoimmunity and positive SE-IgE in severe asthma patients, further supporting that +SE-IgE represent a unique phenotype, which may have future implications in the choice of biologics.