Intratracheal administration of Mycobacterium vaccae as a long term effect on airway histopathology of chronic asthma in BALB/c mice

Abstract

Rationale To evaluate whether intratracheal M. vaccae administration may provide a therapeutic effect and long-term protection on airway histopathology of already established chronic asthma in BALB/c mice. Methods BALB/c were divided into four groups. Chronic asthma model was established in groups I, II and III as per protocol. Mice in group IV served as controls. Groups I and II were also treated with 10μl of 10 7CFU of M. vaccae intratracheally (i.t.) (days 42-45-48). Group III did not receive any M. vaccae. Two days after the last i.t. instillation lungs were taken out for histopathologic evaluation from mice in Group I, III and IV. To evaluate long-term efficacy of M. vaccae, mice in Group II were challenged with OVA nebulization three weeks after the last i.t. instillation, and then were sacrificed. Results All of the histopathologic characteristics evaluated in all airways were significantly more in Group III when compared to controls. All of the histopathologic parameters of Group I were significantly less than those of Group III. Comparison of Group II and III, revealed histological parameters were significantly less in Group II. Comparison of Group I and II revealed histological parameters were significantly more in Group I. There was no difference in some of the parameters in comparison of Group I and controls. Most of the histopathologic parameters were not significantly different in Group II when compared with controls. Conclusions M. vaccae administration may provide an effective and long-term therapeutic strategy in treatment of histopathologic changes in murine model of chronic asthma.