Prevention of Der p2-induced allergic airway inflammation by Mycobacterium-bacillus Calmette Guerin

Epidemiologic studies suggest an inverse correlation between infection and development of allergy. The purpose of this study was to test the hypothesis whether a preexisting T helper 1 (Th1)-type immune response elicited by Mycobacterium bovis-bacillus Calmette-Guerin (BCG) immunization could suppress allergic airway inflammation induced by the mite allergen Dermatophagoides pteronyssinus group 2 (Der p2) in an animal model. C57BL/6 mice were immunized with subcutaneous injection of BCG, then intraperitoneal Der p2 emulsified in alum. Der p2-specific immunoglobulin G1 and cytokine production from splenocytes were measured after Der p2 sensitization, and pulmonary function and airway inflammation were determined after inhalation challenge with Der p2. The intraperitoneal Der p2 with alum injection was able to induce Der p2-specific immunoglobulin G1 production, which could be downregulated by the pretreatment with BCG + Der p2. The inoculation of BCG + Der p2 caused splenocytes to produce more interferon-gamma, and this level was higher than that elicited by Der p2 or buffer alone. The positive interferon-gamma-staining CD4 cells were also increased after activation by phorbol myristate acetate and ionomycin. Lung pathology examination found decreased airway inflammation (associated with the best pulmonary function and least airway desquamation) in the mice inoculated with BCG + Der p2. In this Der p2-induced allergy model, BCG inoculation with Der p2 can cause a Th1-type immune response that hinders Der p2-induced allergic sensitization and the development of airway inflammation.