Basophil activation test for staphylococcus enterotoxins in severe asthmatic patients

Recent studies suggest that IgE to Staphylococcus aureus (SA) enterotoxins represent a risk factor for severe asthma even in asthmatic patients considered non atopic. SA enterotoxins can stimulate specific IgE responses but, acting as superantigens, they can promote a polyclonal IgE response, airway inflammation, and bronchial hyperresponsiveness. In comparison with the measurement of serum specific IgE, Basophil Activation Test (BAT) can give more relevant results because it measures only functional IgE capable of activating basophils. BAT for SA enterotoxins has never been performed until to now.METHODS:We recruited 35 patients with severe asthma treated according to GINA guidelines. They were tested for skin prick test to common aeroallergens. Total and specific IgE to SA enterotoxins (ImmunoCAP) were measured. Nasal swabs and sputum cultures were obtained. Basophil activation tests (BAT) using CD203c expression was done after stimulation with different concentrations of enterotoxins A, B, and toxic shock syndrome toxin (Sigma).RESULTSBAT for at least one of SA enterotoxin was positive in 13 among 35 severe asthmatic patients (37%), higher in non atopic than in atopic asthmatic patients (41% vs 33%). Specific IgE to SA enterotoxins were detected in 19 patients ( 54%). No relationship was observed between SA nasal colonization and the presence of IgE or the positivity of basophil activation test for SA enterotoxins.CONCLUSIONS:In this study we demonstrate the involvement of specific IgE mechanisms in severe asthmatic patients sensitised to staphylococcus enterotoxins. The potential benefit of anti-IgE therapy in this subgroup of severe asthmatic patients has to be investigated.