Attenuated Salmonella typhimurium reduces ovalbumin‐induced airway inflammation and T‐helper type 2 responses in mice

Summary Cytokines produced by Th2 cells are responsible for the pathogenesis of asthma. Th1‐biased immune responses caused by attenuated salmonella have the potential to relieve asthmatic symptoms. We evaluated whether oral administration of attenuated salmonella could modulate allergic responses in a chicken ovalbumin (OVA)‐induced asthmatic murine model. Mice were fed with attenuated salmonella SL7207 one dose before and three doses during the induction of an allergic response. Lung histology, percentages of eosinophil in bronchoalveolar lavage fluid, serum levels of OVA‐specific antibodies and cytokine production by OVA‐activated splenocytes were evaluated in mice with or without the administration of SL7207. A significant reduction in pulmonary eosinophilic infiltration was observed in mice receiving attenuated salmonella. Lower levels of OVA‐specific IgG1 but higher titres of OVA‐IgG2a in serum were also detected in this group. Splenocytes from salmonella‐fed mice produced lower levels of Th2 cytokines upon OVA stimulation. The administration of attenuated salmonella significantly suppressed immunopathological symptoms in OVA‐sensitized mice. Inhibition of Th2 responses might explain the potential mechanisms. This study provides some evidence for the feasibility of attenuated salmonella as an effective vaccine for allergic diseases.