An update on the impact of Staphylococcus aureus enterotoxins in chronic sinusitis with nasal polyposis

Abstract

Nasal polyps in adults, characterized by abundant eosinophils, local overproduction of immunoglobulin E, and often associated with asthma, have been appreciated as an eosinophilic inflammation, potentially of allergic origin, but unrelated to a bacterial impact. Evidence accumulates, however, that Staphylococcus aureus colonizes chronic rhinosinusitis with, but not without polyps, with significantly increased prevalence. The germs release enterotoxins, which act as superantigens and induce a topical multiclonal IgE-formation as well as a severe, possibly steroid-insensitive eosinophilic inflammation. Recently, S. aureus could be demonstrated to reside intraepithelially, and potentially to release superantigens into the tissue from within the epithelial cells. An immune defect, either in the innate or adaptive immunity, might be responsible for this phenomenon. Follicle-like structures and lymphocyte accumulations, specifically binding enterotoxins, can be found within the polyp tissues, giving rise to local IgE formation. The superantigen-induced immune response also leads to a modulation of the severity of the eosinophilic inflammation, and may be linked to lower airway co-morbidity in polyp patients. Interestingly, IgE antibodies to enterotoxins can be found in the majority of aspirin-sensitive polyp tissues, associated with a substantial increase in ECP and IL-5. The possible role of S. aureus enterotoxins in polyp disease in Europe, the US and Asia has meanwhile been supported by several studies, demonstrating the presence of IgE antibodies to enterotoxins and inflammatory consequences in nasal polyp tissue. First studies also point to an involvement of S. aureus derived enterotoxins in lower airway disease, such as severe asthma and exacerbated COPD, clearly suggesting a clinical need for diagnosis and treatment of the germ and its related effects. Therapeutic approaches are so far empirical, and need further study, also serving to proof the clinical relevance of the concept.