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  • 學位論文

抗菌之新策略

New Antibacterial Strategies

指導教授 : 方俊民

摘要


第一部分:流感病毒與肺炎鏈球菌神經胺酸酶的雙效抑制劑 流行性感冒病毒與肺炎鏈球菌的協同作用提高了病毒感染的死亡率。肺炎鏈球菌是造成人類下呼吸道感染、敗血症、腦膜炎的主要病原體之一。病毒生命週期中,宿主細胞膜醣鏈末端的唾液酸受病毒神經胺酸酶作用剝除而釋放子代病毒,同時,被暴露出來的GalNAcβ1-4Gal醣鏈則成為肺炎鏈球菌辨識的受體。另一方面,肺炎鏈球菌的神經胺酸酶也藉由切斷唾液酸而促進其生物膜的生成,以保護細菌免受宿主免疫系統辨識以及抗生素作用。   近期的小鼠實驗顯示,抑制流感病毒的藥物同時也對降低生物膜生長以及細菌在鼻咽中的繁殖情形有顯著的效力。因此,我們以oseltamivir carboxylic acid (OC)為骨架設計了一系列衍生物,希望同時抑制流感病毒與肺炎鏈球菌神經胺酸酶,而控制病原體的生長並減輕症狀。 第二部分:抗鼠傷寒沙門氏菌之脂多醣醣疫苗開發 鼠傷寒沙門氏菌的宿主橫跨人與動物,其感染是一直未被解決的世界性公衛議題,過去的研究也都未能開發出有效益的疫苗。醣聯蛋白疫苗的合成是醣免疫學中的關鍵點,3-deoxy-D-manno-octulosonic acid (Kdo) 在革蘭氏陰性菌脂多醣中核多醣的第一位置具有高度保守性,且其衍生物可保留良好的免疫性並為免疫細胞所辨識,因此,Kdo成為開發醣疫苗一個備受關注的標的。目前仍沒有一個對Kdo具特異性的衍生化方法,進而連接載體蛋白而成具病原體特異性的醣聯蛋白抗原。   過去我們實驗室利用鄰苯二胺與Kdo進行特殊的縮合反應而成功合成醣聯疫苗。在本篇論文延續過去的研究,對過去架構的方法進行確認與修正,從中也改進了去酯質A脂多醣(LFLPS)分離的方法。接下來,我們將進一步掌握最佳的醣鏈長度以及載體蛋白連結密度,把疫苗的效用提到最高。

並列摘要


Part 1. Dual Function Agents Targeting Influenza Virus and Streptococcus pneumonia Neuraminidase Influenza virus causes annual epidemics and occasional pandemics, and has claimed millions of lives worldwide. The synergism between Streptococcus pneumoniae and influenza virus further enhances the infection mortality. S. pneumoniae remains a major cause of human lower respiratory tract infection, otitis media, bacterimia, pneumonia and meningitis despite treatment with vaccines and antibiotics. In the last stage of virus infectious cycle, neuraminidase (NA) strips sialic acid from host glycan terminal, and exposes the residue GalNAcβ1-4Gal as the receptor for pneumonia adherence. In addition, pneumonia neuraminidase (NanA) also catalyzes the release of sialic acid, which becomes the nutrient for bacterial biofilm growth. Biofilm is defensive against antibiotics, and protects bacteria from recognition by host immune system. The recent mice experiments indicate that influenza virus neuraminidase inhibitors show notable ability of reducing biofilm growth and pathogen colonization of S. pneumoniae in nasopharynx. Hence, we design a series of potential active compounds based on oseltamivir carboxylic acid skeleton to inhibit virus and pneumoniae neuraminidases simultaneously. Part 2. Synthesis, characterization, and immunogenicity of O-specific polysaccharide based glycan vaccine against Salmonella typhimurium Salmonella typhimurium infections are a serious medical and veterinary problem in the world. It causes food poisoning, and its host species across humans and animals. Up to date, there still lacks an effective vaccine for prevention of Salmonella infections. Ordinarily, immunogens are derived from proteins or fragments of peptides. Using the highly conserved glycans on the surface of immunogen or cancer cell is another way to develop vaccines. For Gram-negative bacteria, Kdo (3-deoxy-D-manno-octulosonic acid) is a highly conserved α-keto acid saccharide at the terminal of O-specific polysaccharide in lipopolysaccharide (LPS). Synthesis of glycan conjugate is a critical issue in glycan immunology. Using a specific condensation reaction between linker and O-specific polysaccharide, Ming-Cheng Chen in our lab has successfully synthesized a glycan conjugate. In this study, I further improve the separation resolution of lipid A-free LPS (LFLPS). The size and loading of LFLPS on carrier protein will be tuning to increase the vaccine efficacy.

參考文獻


1. Diavatopoulos, D. A.; Short, K. R.; Price, J. T.; Wilksch, J. J.; Brown, L. E.; Briles, D. E.; Strugnell, R. A.; Wijburg, O. L. FASEB J. 2010, 24, 1789–1798. Influenza A virus facilitates Streptococcus pneumoniae transmission and disease.
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