结核杆菌PIM抗原表位的设计、合成与免疫活性研究

The research of Mycobacterium tuberculosis glycolipidic vaccine is the frontier topic of developing a new anti-tuberculosis vaccine in the world, and the identification of the epitope structure is the key to the design of the vaccine. The lipopolysaccharide PIM molecule is an important component of the cell wall of Mycobacterium tuberculosis, as well as an ideal target antigen for the research and development of anti-tuberculosis vaccine. Previous studies have found that CD1b-restricted T cells can specifically recognize PIM antigens and induce the immune response. However, the precise structure of PIM epitope binding to CD1b protein has not yet been determined. The aim of this project is to study the glycolipidic antigen Ac2PIM2 which come from the cell wall of Mycobacterium tuberculosis as the research object, a series of PIM structural compounds with different acylation forms were designed and synthesized by mimic the process of PIM molecule presented by CD1b proteins in antigen-presenting cells; Screening out the minimal PIM structure required for binding to CD1b protein by the evaluation of immunological activity in vitro, and elucidating the mechanism of PIM antigen binding to CD1b protein; Balb/C mice were immunized with the selected PIM epitope and immunoadjuvant, and the antibody titer in sera of the immunized mice were investigated by ELISA method, combining with the structure-activity relationship, we hope to find high titer PIM epitope. It will provide a new strategy for the study of novel anti-tuberculosis vaccine.

结核杆菌糖脂疫苗的研究是国际上研发新型抗结核疫苗的前沿课题，抗原表位结构的确定是疫苗设计的关键。脂多糖PIM分子是结核杆菌细胞壁的重要组分，是研发抗结核疫苗的良好靶标抗原。申请人前期研究发现CD1b限制性T细胞能特异性识别PIM抗原产生免疫应答，但是PIM抗原与CD1b蛋白结合的抗原表位结构尚未确定。本项目以结核杆菌糖脂抗原Ac2PIM2分子为研究对象，通过模拟CD1b蛋白在抗原提呈细胞中呈递PIM抗原的过程，设计合成一系列不同酰化形式的PIM结构化合物；经体外免疫活性实验筛选出与CD1b蛋白结合的最小结构的PIM抗原表位，阐明PIM抗原与CD1b蛋白的作用机制；并将筛选的PIM抗原表位与免疫佐剂混合接种Balb/C小鼠，ELISA法考察小鼠血清中的抗体效价水平，结合构效关系，以期发现效价高的PIM抗原表位，为研究新型抗结核疫苗提供新的策略。

脂多糖PIM分子是结核杆菌细胞壁的重要组分，在结核杆菌感染人体的过程中发挥着重要的作用。CD1分子与MHC-Ⅰ类分子的结构相似，可以提呈PIM糖脂抗原刺激T细胞产生免疫应答。本项目通过模拟天然脂多糖PIM分子在抗原提呈细胞中的加工过程，设计合成了6种不同酰化形式的非天然PIM抗原结构，考察其免疫活性并结合构效关系，初步揭示了PIM抗原表位与CD1分子的相互作用机制，为开发新一代抗结核疫苗提供了新的策略。