甘露糖受体MR参与隐球菌免疫逃逸的机制研究

Cryptococcus has rapidly risen to a worldwide highly recognizable major opportunistic fungal pathogen which often cause lethal infections. Mannose receptor ( MR ) is a glycoprotein receptor belonging to C type lectin-like superfamily.It is expressed in dendritic cells and macrophages, can identify cryptococcal mannose protein ( MP ) and endocytosis of Cryptococcus and present antigens to T cells,then protect the organism against cryptococcal infection. We found that cryptococcus can down-regulate MR expression in dendritic cells and macrophages, its mechanism remains unclear. In view of MR playing an important role in immunity against cryptococcal infection, we want to know how can Cryptococcus down-regulate MR expression in immune cells and its significance.We proposed to purificate cryptococcal capsular polysaccharide composition, clarifying which composition can down-regulate MR expression.Further more,we proposed to construct the MR recombinant adenovirus vector which can gene modificate DCs, and macrophage cell line which can stablely express MR protein,then observe the ability of MR overexpressing dendritic cells and macrophages in phagocytosis and killing of cryptococcus, presenting cryptococcal antigen to T cells.Finally, we proposed to observe the therapeutic effect on cryptococcosis by reinfusion of MR modified dendritic cells vaccine,providing new ideas for clinical treatment for cryptococcosis.

隐球菌是一种严重危害人类健康的医学真菌，常引起致命性感染。甘露糖受体（MR）是隐球菌甘露糖蛋白（MP）的受体，主要表达于树突状细胞(DCs)和巨噬细胞，参与吞噬隐球菌及递呈隐球菌抗原给T细胞，诱发机体对隐球菌的免疫应答。我们前期实验发现隐球菌可以下调DCs及巨噬细胞MR的表达，这有可能是其逃逸机体感染免疫的新机制。本课题拟明确隐球菌诱导下调免疫细胞MR表达的机制及意义。我们拟通过纯化隐球菌荚膜多糖成分，阐明隐球菌如何下调MR的表达。拟进一步通过构建MR重组腺病毒载体及稳定表达细胞系，观察过表达MR后DCs及巨噬细胞的吞噬和杀伤隐球菌功能、递呈隐球菌抗原能力的变化，为隐球菌是否通过下调MR表达而逃逸机体免疫应答提供依据。拟进一步通过回输过表达MR的树突状细胞疫苗，观察其对隐球菌病的预防及治疗作用，为隐球菌病的临床防治提供新的思路。

新生隐球菌是一种严重危害人类健康的医学真菌，常引起致命性感染。甘露糖受体（MR）是新生隐球菌甘露糖蛋白（MP）的受体，主要表达于树突状细胞（DCs)和巨噬细胞，残余吞噬隐球菌及递呈隐球菌抗原给T细胞，诱发机体对隐球菌的免疫应答。我们通过纯化隐球菌夹膜多糖成分，阐明隐球菌如何下调MR的表达；进一步通过构建MR重组腺病毒载体及稳定表达细胞系，观察过表达MR后DCs及巨噬细胞吞噬和杀伤隐球菌功能、递呈隐球菌抗原能力的变化，为隐球菌是否通过下调MR表达而逃逸机体免疫应答提供理论依据。我们成功纯化和鉴定了甘露糖蛋白MP和隐球菌夹膜多糖GXM，我们发现，隐球菌下调巨噬细胞MR的表达不是促进膜MR脱落成可溶性SMR所致，而是依赖于高浓度甘露糖蛋白MP，与隐球菌夹膜多糖GXM无关。第二，甘露糖蛋白MP能促进MAPK和NF-κB信号通路的活化，TLR2参与调节MR的信号传导，参与巨噬细胞杀伤隐球菌；第三，甘露糖蛋白通过活化P38 MAPK信号通路下调MR的表达；同时，我们发现过表达MR增强树突状细胞递呈甘露糖多肽抗原的能力，不影响MP刺激的DCs的表型变化，敲除MR基因降低巨噬细胞吞噬隐球菌的能力，差异均具有统计学意义（P<0.05）。综上所述，甘露糖蛋白（MP）与巨噬细胞直接接触能活化巨噬细胞的炎性信号通道，下调甘露糖受体（MR）的表达；巨噬细胞的甘露糖受体（MR）表达水平与其杀伤隐球菌的能力正相关。由此，若拟提高巨噬细胞表达MR，可为隐球菌病的防治提供新的思路。