目的　研究大肠杆菌致病岛LEE基因群中调节基因ler对细菌致病性和免疫原性的影响 ,评价基因缺失突变疫苗株的免疫效果 ,为人致病性和出血性大肠杆菌基因缺失突变疫苗的研制提供技术路线。方法　利用兔致病性大肠杆菌REPECO1 0 3为始发菌株 ,根据同源重组的原理 ,运用自杀性载体 pCVD442技术 ,敲除位于细菌染色体上的ler基因 ,构建ler基因缺失突变株 ,通过动物实验 ,检测基因缺失突变株的致病性和免疫保护作用。结果　构建了REPECO1 0 3ler基因缺失突变株 ,并证实ler基因细菌致病岛的正调控作用和对细菌生长的负调控作用。家兔实验研究表明 ,ler基因缺失突变株无致病性 ,但保留着良好的免疫原性。结论　首次揭示了ler调节基因与细菌致病性和免疫原性的关系 ,构建的REPECO1 0 3ler基因缺失突变株安全性好 ,具有良好的免疫保护作用 ,是理想的家兔的致弱疫苗候选株。该研究为人致病性和出血性大肠杆菌疫苗的研制提供了重要的参考资料 Objective To investigate the effect of ler, a regulatory gene of LEE gene on the pathogenicity of E. coli, in the pathogenicity and immunogenicity of bacterial pathogens and to evaluate the immunogenicity of gene-deleted mutants and to evaluate the effect of ler on human pathogenic and hemorrhagic E. coli mutants Research and development to provide technical route. Methods Based on the principle of homologous recombination, the ler gene located on the bacterial chromosome was knocked down by suicide vector pCVD442 using the REPECO103 strain of pathogenic E. coli as an initial strain to construct a ler deletion mutant. , Detection of gene deletion mutant pathogenicity and immune protection. Results The REPECO1 0 3ler gene deletion mutant was constructed and the positive regulation of bacterial pathogenicity island of ler gene and negative regulation of bacterial growth were confirmed. Rabbit experimental studies have shown that ler gene deletion mutant is non-pathogenic, but retains good immunogenicity. Conclusions The relationship between ler regulatory genes and pathogenicity and immunogenicity of bacteria was revealed for the first time. The constructed REPECO1037ler gene deletion mutant is safe and has good immunoprotection, which is an ideal weakened vaccine candidate for rabbits . This study provides an important reference for the development of human pathogenic and hemorrhagic E. coli vaccines