Whereas proteolytic cleavage is crucial for peptide presentation by classical major histocompatibility complex (MHC) proteins to T cells, glycolipids presented by CD1 molecules are typically presented in an unmodified form. However, the mycobacterial lipid antigen mannosyl-β1-phosphomycoketide (MPM) may be processed through hydrolysis in antigen presenting cells, forming mannose and phosphomycoketide (PM). To further test the hypothesis that some lipid antigens are processed, and to generate antigens that lead to defined epitopes for future tuberculosis vaccines or diagnostic tests, we aimed to create hydrolysis-resistant MPM variants that retain their antigenicity. Here, we designed and tested three different, versatile synthetic strategies to chemically stabilize MPM analogs. Crystallographic studies of CD1c complexes with these three new MPM analogs showed anchoring of the lipid tail and phosphate group that is highly comparable to nature-identical MPM, with considerable conformational flexibility for the mannose head group. MPM-3, a difluoromethylene-modified version of MPM that is resistant to hydrolysis, showed altered recognition by cells, but not by CD1c proteins, supporting the cellular antigen processing hypothesis. Furthermore, the synthetic analogs elicited T cell responses that were cross-reactive with nature-identical MPM, fulfilling important requirements for future clinical use.

中文翻译：

---

由 CD1c 呈递给 T 细胞的抗水解分枝杆菌磷酸糖脂抗原的合理设计。

虽然蛋白水解切割对于经典主要组织相容性复合物 (MHC) 蛋白向 T 细胞的肽呈递至关重要，但由 CD1 分子呈递的糖脂通常以未经修饰的形式存在。然而，分枝杆菌脂质抗原甘露糖基-β1-磷酸霉菌酮 (MPM) 可通过抗原呈递细胞中的水解加工，形成甘露糖和磷酸霉菌酮 (PM)。为了进一步检验某些脂质抗原被加工的假设，并产生导致未来结核病疫苗或诊断测试的确定表位的抗原，我们旨在创建保留其抗原性的耐水解 MPM 变体。在这里，我们设计并测试了三种不同的通用合成策略来化学稳定 MPM 类似物。CD1c 复合物与这三种新的 MPM 类似物的晶体学研究表明，脂质尾部和磷酸基团的锚定与天然相同的 MPM 具有高度可比性，甘露糖头基团具有相当大的构象灵活性。MPM-3 是一种经二氟亚甲基修饰的 MPM，具有抗水解性，显示出细胞识别的改变，但 CD1c 蛋白没有，这支持了细胞抗原加工假说。此外，合成类似物引发的 T 细胞反应与天然相同的 MPM 发生交叉反应，满足未来临床应用的重要要求。一种耐水解的二氟亚甲基修饰的 MPM 显示出细胞识别的改变，但 CD1c 蛋白没有，这支持了细胞抗原加工假说。此外，合成类似物引发的 T 细胞反应与天然相同的 MPM 发生交叉反应，满足未来临床应用的重要要求。一种耐水解的二氟亚甲基修饰的 MPM 显示出细胞识别的改变，但 CD1c 蛋白没有，这支持了细胞抗原加工假说。此外，合成类似物引发的 T 细胞反应与天然相同的 MPM 发生交叉反应，满足未来临床应用的重要要求。