Effects of bacillus calmette-guerin by different dosages at different times on airway inflammation in mouse models of asthma

Objective To investigate the effects of subcutaneous injection of bacillus calmette-guerin (BCG) by different dosages at different times on the airway inflammation and airway mucus secretion in a mouse model of asthma.Methods A group of C57BL/6 mice were sensitized and challenged by ovabumin (OVA) as positive group and other mice were treated by saline as negative group.Six groups of mice were infected with BCG at different times with different dosages as follows:subcutaneous BCG 10 5 CFUs (1)4 days before (group 1),(2) 10 days after the first OVA sensitization (group 2),(3)1 hr after the last OVA challenge (group 3),(4)both 4 days before and 10 days after the first OVA sensitization (group 4).Mice in the other two groups were injected subcutaneously with BCG10 6 (group 5) or 10 4 CFUs (group 6)10 days after the first OVA sensitization.Then the bronchoalveolar lavage(BALF)eosinophil numbers and airway mucus secretion 48 hours after the last OVA challenge were analysed.Results In asthma group ,the EOS numbers in BALF were (41.16±6.42)×10 4 but these cells were scarcely seen in negative group.EOS in BALF of each BCG infected group decreased compared with the asthma group( P 0.05) as follows:(10.69±4.35)×10 4 in group 1,(7.92±2.30)×10 4 in group 2,(17.46±8.00)×10 4 in group 3,(8.71±3.83)×10 4 in group 5,and(17.19±4.49)×10 4 in group 6.When BCG 10 5 CFUs were infected twice (group 4),the decrement of EOS in BALF was more obviously( P 0.01) with inhibition ratio more than 98%.There were mucus hypersecretion in the epithelial cells in the asthma group but no mucus secretion in negative group.In BCG-infected mice mucus secretion was suppressed significantly.Conclusions Subcutaneous injection of BCG 10 5 CFUs inhibited the accumulation of EOS in BALF by twice more significantly than BCG 10 6 CFUs by single time.Either before or after OVA sensitization or after OVA challenge BCG infection can inhibit EOS accumulation in BALF and decrease mucus hypersecretion in the airway epithelial cells,suggesting that BCG could not only prevent but also treat the the airway inflammation in a mouse model of asthma.