不對稱N-聚醣主架構之合成暨肺炎鏈球菌6A及6B血清型之疫苗研究

Abstract

醣類廣泛存在於生物體中，並參與許多重要的生物過程，例如細胞黏附、癌症進程、宿主與病原的交互作用、抗體辨識等。本文第一部分，描述複雜N-聚醣六醣主架構的化學合成，此六醣經由收斂型方法合成，並具有不對稱的支鏈結構，其結構依酵素反應模型研究之結果設計，可應用於酵素催化之選擇性醣鏈結反應，以建構多種複雜N-聚醣，其中以葡萄糖胺上之一級胺基或醯胺可有效作為區別，此六醣可接合胺基連接子以利醣晶片製備，亦可與抗體接合以利抗體之醣修飾。本文第二部分，描述肺炎鏈球菌6A及6B血清型之莢膜多醣片段合成及疫苗研究，此莢膜多醣為磷基化類四醣重複單元，共十八個寡醣片段經由收斂型方法合成，其中選取八個連接攜帶蛋白並進行小鼠疫苗實驗並探討其免疫原性，四個磷基化類四醣成功誘發辨認醣類之抗體與調理殺菌之抗體，其中兩個具有橋接磷基的類四醣具有交互保護力，此篇結果提供合成型肺炎鏈球菌疫苗發展之可能性。

Oligosaccharides widely exist in organisms and are involved in many biological processes, such as cell-cell adhesion, cancer progression, host-pathogen interaction, and antibody recognition. In part I, chemical synthesis of the main hexasaccharide of complex type N-glycans was described. This hexasaccharide was installed asymmetric branching through protecting group engineering to enable selective enzymatic glycosylation for further diversification. A convergent synthetic pathway was performed with the chemical reactions tuned, and the effective constitution of the hexasaccharide was supported by several model studies of enzymatic reactions. Amine-amide differed glucosamine was found to be the valid differentiation for enzymatic elongation. Moreover, the hexasaccharide enables amino-linker coupling for immobilization and antibody coupling for glycan modification. In part II, chemical synthesis and immunological evaluation of capsular polysaccharide fragments of Streptococcus pneumoniae serotypes 6A and 6B were described. A library of eighteen oligosaccharides, derived from capsular repeating phosphorylated pseudo-tetrasaccharides, were built through systematic convergent synthesis. Eight of them were conjugated onto carrier protein and applied to mouse immunization for immunogenicity studies. Four pseudo-tetrasaccharides with phosphate elicited glycan-binding and opsonic antibodies, and the phosphate-bridged pseudo-tetrasaccharides exhibited cross-reactivity. The results provided potential development in synthetic pneumococcal conjugate vaccines.