Abstract
Pretreatment with mycobacterial Ags has been shown to be effective n preventing allergic airway inflammation from occurring in a mouse model. Because most asthmatics are treated after the development of asthma, it is crucial to determine whether mycobacterial Ags can reverse established allergic airway inflammation in the presensitized state. Our hypothesis, based upon our previous findings, is that mycobacteria treatment in presensitized mice will suppress the allergic airway inflammation with associated clinical correlates of established asthma, with the noted exception of factors associated with the early allergic response (EAR). BALB/c mice sensitized and challenged with OVA were evaluated for pulmonary functions during both the EAR and late allergic response, and airway hyperresponsiveness to methacholine. Following this, sensitized mice were randomized and treated with placebo or a single dose (1 × 105 CFUs) of bacillus Calmette-Guérin (BCG) or Mycobacterium vaccae via nasal or peritoneal injection. One week later, the mice were rechallenged with OVA and methacholine, followed by bronchoalveolar lavage (BAL) and tissue collection. Mice treated with intranasal BCG were most significantly protected from the late allergic response (p <0.02), airway hypersensitivity (p <0.001) and hyperreactivity (p <0.05) to methacholine, BAL (p <0.05) and peribronchial (p <0.01) eosinophilia, and BAL fluid IL-5 levels (p <0.01) as compared with vehicle-treated, sensitized controls. Intranasal M. vaccae treatment was less effective, suppressing airway hypersensitivity (p <0.01) and BAL eosinophilia (p <0.05). No changes were observed in the EAR, BAL fluid IL-4 levels, or serum total and Ag-specific IgE. These data suggest that mycobacterial Ags (BCG≫M. vaccae) are effective in attenuating allergic airway inflammation and associated changes in pulmonary functions in an allergen-presensitized state.