Effect of bacillus calmette-guerin (BCG) administration at various age in balb/c mice on allergic responsiveness and asthma development

Backgrounds and Aims;. There are several reports about the effect of Basil Calmette-Guerin (BCG) vaccine on development of allergic diseases. In this study we aimed to evaluate the effects of BCG administration on allergic responsiveness and asthma development at various age of life (first and second week after birth and adulthood) in Balb/c mice.Material and Method; Balb/c mice included to the study were divided into different groups according to the BCG administration time. Groups were labeled as Group IA; BCG administered at 7 th day of life, Group IB; without BCG administration at 7 th day of life, Group IIA; BCG administered at 14 th day of life, Group IIB; without BCG administration at 14 th day of life, Group IIIA; BCG administered at adulthood, Group IIIB; without BCG administration at adulthood, Group IV; no procedure was performed. In first three groups mice were sensitized intraperitoneally with OVA after 8 weeks (on 0, 7, 14 and 21 th days) and after that challenge was performed with inhaled OVA between 21-28 days to develop asthma model. Following kethamine anesthesia and servical dislocation mice were sacrificed, BAL fluid and lung tissues were taken. Cytospin slides were prepared from BAL fluid and cell morphology was determined. IL-4, IL-12, IL-10 and IFN-? were evaluated by ELISA method. Inflammation score and goblet cell count were defined on lung biopsy.Results; Eosinophil count and inflammation score was low statistically significant in groups in which BCG administered at 7th day of life and at 14th day of life compared to groups without BCG administration and group with BCG administration at adulthood (p<0.05). In all allergic sensitized mice lungs goblet cells were found, but goblet cell count was lower in BCG administered group (p<0.05). IL-4 levels were found to be lower in group IA and IIA compared to group IB and IIB and IIIA(p<0.05). IL-12 levels were higher in IIA than IIB and IIIA (p<0.05). However there was no statistically difference between Group IA and IIA. Similarly IL-10 and IFN-? levels were higher in group IA and IIA compared to IB, IIB and IIIA (p<0.05). In group IA there were statistical significant reverse correlation between IL-4 and IL-12, and between IL-4 and IL-10 (r=-0.702; p=0.023and r=-0.807; p=0.005, respectively.). In group IIA there was statistical significant reverse correlation between IL-4 and IL-12 levels (r=-0.706, p=0.023), however despite the reverse correlation between IL-4 and IL-10, it was not statistical significant. In Group IA, Group IIA and Group IIIA, there was statistical significant positive correlation between IL-12 and IFN-? (r=0.796; p=0.006, r=0.867; p=0.001; r=0.916, p=0.001).Conclusion; BCG vaccination may prevent allergic inflammation and asthma development. Because of reverse correlation between IL-4 and IL-10 and IL-12 in early administration of BCG and reverse correlation only between IL-4 and IL-12 in later vaccinated group, we may suggest that this effect mediated by Treg cells and Th1 cells in early period and by IL-12 via production from Th1 cells in late period. However to identify the exact mechanism further investigation should be performed.