β-(2,1)-低聚果糖的合成新方法及在化学组装疫苗中的应用

Vaccines made from microbes are popularly used but with many limitations such as toxic, limited scopes. Other vaccines assembled from simulated synthesized antigens are low toxic, towards many diseases but can only promote low immune response and thus need improve their efficacy. The key to improve the immune response of chemical assembled vaccines is to improve its recognition by antigen-presenting cells (APC). It has been found that the size and the surface structure of vaccines are very important to this recognition. β-(2,1)-fructan including both γ and δ type have performed potential utility as adjuvant indicating a short fragment of fructan, β-(2,1)-fructooligosaccharide, would be good surface materials of vaccines. Another study also discloses that fructan is involved in the pathway of Toll-like receptor on the surface of the antigen-presenting cells. A high efficient chemical synthetic method leading to the synthesis of β-(2,1)-fructooligosaccharide is the key to develop a new vaccines assembled with chemistry tools. Thus, introduction of β-(2,1)-fructooligosaccharide to the surface of polystyrene polymer particles would take advantages of both the good surface properties of β-(2,1)-fructooligosaccharide and the standardized quality control of polymer production. Thereby, a creative neighboring group participation protocol will be developed to prepare β-(2,1)-fructooligosaccharide and then conjugated to the polystyrene particles before antigens being assembled together, varies vaccines thus assembled will be injected to mice to observe the immune response. Vaccines with different sizes will be prepared to observe the trend of their immune response under orthogonal protocols.

微生物来源疫苗应用广泛，但是毒性大。人工模拟组装疫苗安全低毒，但是免疫活性低。增强人工疫苗活性在于增强其与抗原呈现细胞的生物识别度。人工疫苗佐剂直径及表面形态非常重要，β聚合果糖具有很好的佐剂的活性，有研究指出β聚合果糖与抗原呈现细胞表面Toll样受体有关。高效合成β果糖新方法的开发以及六聚果糖的合成是开发人工β聚合果糖佐剂的关键，将合成的β聚合果糖偶联到高分子微球表面，既可利用聚合果糖的表面特性，又可以组装标准化程度高的高分子微球疫苗。课题目标是创新性借助环外酯基参与合成β低聚果糖，并连接到高分子微球，组装不同的疫苗来研究生物活性。准备不同直径的疫苗颗粒，进而用正交的科学实验手段研究直径对疫苗免疫活性的影响。

本项目计划应用低聚果糖与高分子微球连接模拟固态天然Inulin，再吸附混合肿瘤细胞表面糖抗原，实现表面β（2,1）低聚果糖修饰的化学组装佐剂和疫苗。β（2,1）低聚果糖合成新方法学研究利用1位侧链酯基这一环外邻位酯基参与控制果糖糖苷化立体选择性， 1位侧链酯基确实能够参与糖苷化并在果糖供体活化后参与生成双五元螺环中间体，这是热力学稳定中间体，决定了糖苷化产物构型。其中，类双平伏键构象给体得到α选择性产物，在类双直立键构象给体得到β选择性的糖苷化产物。本项目还合成了肿瘤类糖抗原，一种尚未进行临床研究，但是具有seglec-7特异亲和性的结肠腺癌表面特异糖抗原 DSLc4 神经酰胺的特征六糖结构，同时也是重要的人乳寡糖DSLNT。为实现这一合成，本项目还发展了α唾液酸糖苷化新方法，并重新挖掘优化了双乙酰基保护的氨基葡萄糖糖苷化方法，两种新开发的糖苷化方法有效提高寡糖合成效率。