Abstract: Objective The purpose of this study is to observe the protective effect of rAAV-BF infected mice against lethal dose of E.coli.Methods The rBF protein in CHO cells、mice injected muscle and serum were detected by Dot-blot、Western blot、immunohistochemistry assay and a modified enzyme linked immunosorbent assay(ELISA),the levels of endotoxin were measured by reagent kits,establishing MLD E.coli causing death model for the detection of the mice resistant to MLD E.coli infection after administration with rAAV-BF.Results (1)The presence of rBF protein was detected in CHO cells and injected mice muscle, serum from the gene transfected mice could neutralize endotoxin and kills E.coli.(2)The survival rate of Balb/c and C57BL/6 mice of rAAV group（30%-40%）was significantly higher than control group（0%）.Serum endotoxin level of rAAV-BF group mice was significantly lower than that control group. rAAV-BF plus antibiotics have synergistic effect：the survival rate of rAAV-BF group was significantly higher than that of control group; the survival rate（85%） of rAAV-BF infected C57BL/6 mice was significantly higher than that of Balb/c mice（65%）.Conclusion rAAV-BF infected mice have restistence to lethal dose of E.coli, which might provide the base to protect clinical high risk patients from being infected by bacteria and accordingly to reduce mortality.

Key words: AAV2-BPI1-199-Fc, 1 recombinant virus, BPI1-199-Fc, 1 recombinant protein, Gram-negative bacteria(GNB), Endotoxin, Minimal lethal dose(MLD)