Evaluation of the immunogenicity of a rBCG expressing GM-CSF and LMP2A
Objective To identify the expression of a fusion gene GCA formed from GM-CSF gene and LMP2A gene of Epstein-Barr virus （EBV） in a recombinant BCG （rBCG） and to study its immunoge-nicity.Methods The rBCG was constructed to express the fusion gene GCA and the expressed products were detected by Western blot assay .ELISA was performed to measure specific antibody titers in serum sam-ples from mice immunized with rBCG .Lactate dehydrogenase assay was used to analyze the cellular immuni-ty of mice.A mouse model of EBV-positive gastric carcinoma was established to evaluate the therapeutic effects of rBCG.Results The target proteins of GM-CSF and LMP2A were successfully expressed in rBCG . The specific antibodies were detected in rBCG immunized mice as indicated by ELISA .The maximum anti-body titer reached 1 ∶27 900 [（326.5±7.8） pg/ml] as injection with rBCG 5×10^8/mouse.The rBCG in-duced cytotoxicity of cytotoxic lymphocytes （CTLs） to EBV-positive gastric carcinoma cells （GT39） （with a killing rate of 89.6%±6.8%） was significantly higher than that of control group （P〈0.05） The sizes of tumor in PBS control group [（1964.0±548.7） mm3] and BCG group [（1268.65±72.4） mm3] were bigger than those in rBCG group [（168.64±78.80） mm3].Conclusion The rBCG expressing GM-CSF and LMP2A fusion gene was successfully constructed .The rBCG could induce humoral and cellular immune re-sponses in mice and inhibit the growth of tumor . 
 
Key words: 
GM-CSF; LMP2A; rBCG; Cytotoxic lymphocyte; Mice