多糖蛋白结合疫苗在预防传染病方面发挥着重要作用，如肺炎、脑膜炎和菌血症，但是现有化学交联法制备多糖蛋白结合疫苗存在安全性、产物均一性差、成本高等问题。原核生物糖基化修饰系统的发现为利用生物法合成多糖蛋白结合疫苗提供了理论基础。本研究以甲型副伤寒沙门氏菌为模型，将脑膜炎奈瑟球菌的O-糖基化修饰系统引入其中，通过对底物蛋白的修饰效率、对糖基化位点的筛选、对糖链长度的控制，以及获得的多糖蛋白结合物的免疫学特性等问题的研究，阐明O-糖基化修饰系统与载体蛋白、糖链长度、糖基化位点之间的联系，为获得病原菌多糖直接修饰载体蛋白的多糖蛋白结合物奠定理论基础，初步建立利用生物一步法制备多糖蛋白结合物的生物交联技术，同时为新型多糖蛋白结合疫苗表达系统的建立提供技术基础。

Conjugate vaccines are largely used to prevent important invasive bacterial diseases such as pneumonia, meningitis and bacteraemia. The polysaccharide antigens are extracted and purified from the bacterial organism and are activated chemically for conjugation. The unconjugated protein carrier is also manufactured by growing the natural bacterial source or a recombinant host system followed by the appropriate purification process. Due to the multiple activation points within the polysaccharide and multiple linkages on the carrier protein, the resulting conjugate is called a cross-linked network, which is highly heterogenous, unsafe and high cost. The N-glycosylation and O-glycosylation pathways of bacteria were found recently, which provide the basic theory to develop a technology of novel bio-conjugate vaccines. This study will be performed to (i) elimination O-antigen ligase gene and (ii) to reconstruct the Neisseria neningitides O-linked protein glycosylation system in Salmonella paratyphi A. The relationships between carrier proteins, O-antigen lengths, sites of glycosylation and the immunogenicity of polysaccharide -conjugated vaccines were researched and explained. For example, the polysaccharide acceptor will be replaced from the model protein PilE to the extensively used carrier proteins— tetanus toxin C fragment (TTc), dipheria toxoid mutant CRM197, cholera toxin B subunit (CTB), exoprotein A of Pseudomonas aeruginosa (EPA) in which the PglL glycosylation sites will be introduced. This new strategy of producing polysaccharide -conjugated vaccines “One-step bioconjugation technology” can develop and produce immunogenic glycoproteins in a simplified biological process that circumvents many of the challenges and uncertainties involved in currently used methods. The combination of glycoengineered bacteria expression system with established quality control methods maybe provide a mechanism for rapid production of vaccines against common severe bacterial infections produced with its unique, proprietary in-vivo glycosylation platform.