产志贺毒素大肠埃希菌O104:H4能引起大规模疫情暴发，危及生命。抗生素加速细菌毒素释放而加重病情。目前无任何有效抗菌药或疫苗问世。本项目首次设计以O104脂多糖和志贺毒素Stx为靶标的结合疫苗，通过优化疫苗设计策略，拟实现：①抗原选取更合理——以O-特异多糖OSP和Stx2B亚单位为组分，具有双靶标，OSP位于菌体表面易被宿主识别；Stx是关键毒力因子，既作为载体蛋白，又能产生保护性抗体；②研究维度更全面——对候选疫苗的体外调理吞噬、中和毒素活性、体内保护作用、肠道定植细菌清除能力和作用机制进行全方位研究；③研究手段更高效——用一步生物交联法制备候选疫苗，优于传统化学交联；生物发光可视化技术研究疫苗对肠道定植O104菌的清除作用，实时、高效。通过本项目实施，明确脂多糖和Stx是否有潜力成为理想的保护性疫苗作用靶标，初步阐明候选疫苗作用机制，为探索该致病菌感染的有效治疗策略提供新思路。

Shiga toxin-producing Escherichia coli can cause large-scale outbreaks of infection which can be life-threatening. The use of antibiotics increases release of Shiga toxin and makes the disease worse. There are neither effective antibacterial agents, nor any vaccines available to combat this pathogen. In this project, we designed for the first time a polysaccharide-protein conjugate vaccine which targets the O104 lipopolysaccharide and Shiga toxin. By optimizing the traditional strategy of vaccine design, this project aims at: ① Improved selection of antigens. The vaccine candidate is a double-targeted vaccine with the components of O-specific polysaccharide (OSP) and Stx2B subunit. OSP locates on surface of the bacteria and is easily recognized by the host immune system. Stx2 is one of the key virulence factors of this pathogen and used as the carrier protein as well as a potential inducer of protective antibodies. ② A broader range of research. The project includes studies on phagocytic and bactericidal activity, Stx2 toxin-neutralizing activity, protective efficacy and clearance of the O104 bacteria colonized in mouse intestines of the antiserum raised to the vaccine candidate. ③ Methods of high efficiency. One-step bio-conjugation method is used in the preparation of the candidate vaccine and visualization based on bioluminescent is applied in determination of clearance of O104 bacteria colonized in the intestines. Through the implement of this project, we devote to elucidate if LPS and Stx are potential targets of the protective vaccine for STEC O104:H4, reveal the mechanism of action of the candidate vaccine, and provide new clue for exploring the effective treatment options on STEC O104:H4 infection.