A recombinant BCG vaccine generates a Th1-like response and inhibits IgE synthesis in BALB/c mice

The tubercle vaccine, bacille Calmette-Guerin (BCG), is a strong inducer of T-helper type 1 (Th1) responsiveness, and it has been suggested that recom binant BCG (rBCG), which produces and secretes antigens, may be used to pre vent allergic diseases. The effects of rBCG vaccination on allergic respons es in a murine model were examined in this study. A BCG-Escherichia coli sh uttle vector was developed with the promoter and signal sequence of the alp ha-antigen of Mycobacterium bovis, and the vector was tested using E. coli beta-galactosidase as the model antigen and allergen. This vector enabled t he expression of the E. coli beta-galactosidase gene in BCG, which was dete cted in its protein extract by immunoblotting analysis. Vaccination of mice with a single dose of 106 recombinant BCG generated a beta-galactosidase-s pecific antibody response. The splenocytes of vaccinated mice compared with controls produced significantly higher amounts of interferon-gamma (IFN-ga mma) (P < 0.01) and interleukin-2 (IL-2) (P < 0.05) and lower amounts of IL -5 (P < 0.01). Mice vaccinated with rBCG had significantly less (P < 0.01) serum IgE compared with controls. These results together demonstrate that r BCG secreting antigens or allergens may be utilized for the induction of a Th1-like response and the down-regulation of IgE antibody response.