Nasal Carriage of Superantigen Producing Staphylococcus Aureus and Its Role in Pathogenesis of Allergic Rhinitis and Bronchial Asthma

Abstract

Staphylococcal enterotoxins can act as allergens and stimulate production of specific IgE with subsequent development of allergic manifestations. In addition, they act as superantigens that induce cytokine secretion with more increase of IL-4/IFN-γ ratio causing augmentation of allergic reactions. Herein we tested the hypothesis that exposure to Staphylococccus aureus and its enterotoxins induces immunological changes that contribute to the pathogenesis of allergic rhinitis and bronchial asthma. This study included 45 air way allergic patients, and 45 controls. The following were done: intradermal allergy skin testing, invitro effect of staphylococcal enterotoxin B (SEB) on cytokine secretion from separated peripheral blood mononuclear cells, detection of nasal carriage of S. aureus and its enterotoxin production by ELISA & serum levels of total IgE, SEB-specific IgE and eosinophil cationic protein (ECP) were measured. We found that nasal carriage of enterotoxin producing S. aureus in allergic patients was significantly higher than in control. Blood eosinophilia, total IgE& ECP levels were significantly higher in S. aureus nasal carrier than non-carrier patients. On in vitro exposure of PBMCs to (SEB), IFN-γ secretion was significantly less in patients than control and IL-4 secretion was significantly more in patients than control. SEB-specific IgE was detected in 15.6% of patients & not detected in control. There was a significant positive correlation between SEB-specific IgE level in patients and markers of severity of allergic reaction including blood eosinophilia, ECP and total IgE level. This study suggests that nasal carriage of enterotoxin producing S. aureus has a potential role in the development and severity of allergic airway diseases.