Probiotic Escherichia coli Nissle 1917 Suppresses Allergen-Induced Th2 Responses in the Airways

Background: Recent clinical trials, epidemiological studies and animal experiments have suggested that probiotics may help suppress the development of allergic responses. Objective: To investigate whether the application of the probiotic Escherichia coli strain Nissle 1917 (EcN) protects mice from developing ovalbumin (OVA)-specific T helper-2 responses in the airways. Methods: OVA-specific Th2 responses were induced by 2 intraperitoneal (i.p.) injections with OVA/alum followed by 1 intranasal (i.n.) challenge with OVA. EcN was given orally during the entire sensitization and challenge period, together with OVA/alum during the i.p. sensitizations, or i.n. before or during the airway challenge with OVA. Results: We found that when the bacteria were given together with OVA/alum airway eosinophilia, airway hyper-reactivity, goblet cell metaplasia and IL-5 levels in the bronchoalveolar lavage and mediastinal lymph node cell cultures were reduced. This effect was associated with increased numbers of IFN-gamma producing T helper-1 cells and IFN-gamma levels in the airways and strongly increased OVA-specific IgG(2a) titers in the serum. The suppressive effect on airway eosinophilia was dependent on IFN-gamma but not TLR-4. Applying EcN i.n. or orally did not reduce the development of allergen-specific Th2 responses. Conclusions: Our results suggest that EcN can inhibit the development of allergic responses when the bacteria are present at the site of Th2 cell priming and that this immunomodulatory effect is due to a shift from Th2 to Th1 response. The data support the hypothesis that probiotics may help reduce allergic responses and that EcN may also be used as adjuvant therapy to induce allergen-specific Th1 responses. Copyright (c) 2009 S. Karger AG, Basel