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  • 學位論文

抗鼠傷寒沙門氏菌之脂多醣醣疫苗開發

Synthesis, characterization, and immunogenicity of O-specific polysaccharide based glycan vaccine against Salmonella typhimurium

指導教授 : 方俊民

摘要


利用存在於病原及癌細胞表面具特異性的醣分子做為抗原,進而誘發抗體達到治療效果,已成為疫苗研究中的新策略。而在醣疫苗的開發過程中,一個有效方便的醣聯抗原合成方式,便成了具關鍵性要素的課題。對於革蘭氏陰性菌而言,連接細胞壁上O-specific polysaccharide與lipid A之間具高度保守性的Kdo (3-deoxy-D-manno-octulosonic acid),是一個極具吸引力的抗原衍生化標的,除了因為其存在於各種革蘭氏陰性菌的O-specific polysaccharide末端,由其衍生的醣聯抗原也能夠保留細菌脂多醣的抗原性,然而,目前仍沒有一個有效方法能藉由針對性的修飾Kdo,進而與攜帶蛋白連接合成具細菌特異性的醣聯蛋白抗原。 在我們的研究中,首先試圖由Kdo與鄰苯二胺連接體出發合成醣聯蛋白抗原,在以大腸桿菌脂多醣為模型的實驗裡,我們成功合成了醣聯蛋白抗原,並藉由小鼠實驗證明其抗原性。另一方面,沙門氏鼠傷寒桿菌的感染一直是嚴重的全球公衛問題,雖然經過長期的研究,目前仍然沒有有效疫苗可供運用。因此,在研究的第二部份,試圖利用我們開發的方法,應用到沙門氏鼠傷寒桿菌脂多醣的醣聯蛋白抗原合成。經過具抗原性脂多醣片段的純化與鑑定,我們已接續完成醣聯蛋白抗原的合成,而相關的小鼠免疫實驗正在進行中。未來這個方法或許可廣泛應用於革蘭氏陰性菌的醣疫苗開發,也希望能幫助沙門氏鼠傷寒桿菌的疫苗研究。

並列摘要


The synthesis of glycan conjugate is the critical issue in the glycan vaccinology. Traditionally, an immunogen is composed of protein or peptide fragments, but using the highly conservative glycan on the surface of pathogen (e.g. lipopolysaccharide, LPS) or tumor cell (e.g. Global H) as the immunogen has illuminated another direction in vaccine research. For Gram-negative bacteria, the 3-deoxy-D-manno-octulosonic acid (Kdo) is an attractive target for glycan immunogen synthesis. It is highly conservatively at the terminal of O-specific polysaccharide of LPS, and the derivatization from Kdo retains the immunogenicity for immune cell recognition. However, there is no efficient method has been developed for the synthesis of Kdo-derivatized glycan conjugates. In our study, a new method for the construction of glycan conjugate from Kdo is developed. This method is site-specific and reacts under mild acid conditions between O-specific polysaccharide and diamine linker. Utilizing the LPS of E. coli as a model, we have successfully synthesized the glycan conjugates and evaluated its immunogenicity. In another part, we target Salmonella typhimurium, which is a highly pathogenic Gram-negative bacterium worldwide. After more than thirty years’ investigation, there still lacks an efficient vaccine for S. typhimurium prevention. To further apply our conjugation method, the glycan immunogens were synthesized from the immunogenic fractions of LPS in S. typhimurium. The corresponding immunization experiment is in progress. Our strategy might promise a new approach for the development of S. typhimurium glycan vaccine.

參考文獻


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