Strain-dependent suppressive effects of BCG vaccination on asthmatic reactions in BALB/c mice

Background: The choice of BCG vaccine strain may play an important role in vaccination efficiency. Objective: To investigate whether the suppressive effects of BCG on asthma depend on the strain of BCG. Methods: Female BALB/c mice were injected intraperitoneally with 1 of 4 different strains of BCG (I X 10(6) CFU): Pasteur F1173P2, Tokyo 172, Tice, and Connaught. Seven days later, the animals were sensitized by 2 injections of ovalbumin (20 mu g) at 2-week intervals before being provoked with 1% ovalbumin aerosols on 3 successive days. Thereafter, the mice underwent a methacholine bronchial challenge and were killed to quantify the inflammatory cells and cytokines in bronchoalveolar lavage fluid and the supernatant of cultured splenocytes. Results: The eosinophil proportion in the bronchoalveolar lavage fluid was significantly lower and the concentration of interferon-gamma and the interferon-gamma-interleukin 5 (IL-5) ratio in the supernatant of cultured splenocytes were significantly higher in each of the BCG-treated groups (n = 10 per group) than in the asthma control group (n = 15). However, the methacholine sensitivity (P < .05) and IL-5 concentration (P < .01) in the supernatant of cultured splenocytes were significantly lower only in the group treated with the Tokyo strain of BCG. There was a significant positive correlation between IL-5 and IL-10 concentrations (r = 0.79; P < .001). Conclusions: The 4 strains of BCG suppressed asthma to different degrees, but all strains induced a shift in the T(H)1/T(H)2 balance toward T(H)1 without increasing IL-10-related regulatory T-cell activity.