Exploiting antibody catalysis for treating Cryptococcosis

晚期HIV感染的患者有患隐球菌病的风险，这是一种破坏性的真菌感染， 主要是中枢神经系统的形式，难以治疗脑膜脑炎。大量研究 在过去的二十年中，已经表明抗体（Ab）介导的免疫可以做出关键贡献， 来抵御新型隐球菌单克隆抗体（mAb）是有前途的治疗药物， 隐球菌病试剂这种真菌在致病真菌中是不寻常的，因为它有一个大的 一种多糖胶囊，释放大量的多糖抗原到受感染的组织中， 可以干扰免疫反应，从而促进感染的持续。组织抗原是 与免疫重建炎症综合征的发病机制有关，这通常使 HIV和隐球菌感染并发症患者抗逆转录病毒治疗相关的免疫反弹 感染目前，没有从组织中去除多糖的疗法。我们小组发现， 一些单克隆抗体对C.新生儿荚膜具有降解荚膜多糖的催化活性。这 这是一个令人兴奋的发现，因为它提高了开发一种新型隐球菌病治疗方法的可能性 通过去除隐球菌细胞的荚膜并降解它们， 组织抗原沉积。本申请提出了实验以确定Ab介导的细胞因子的贡献。 催化Ab介导的保护作用，目的是为患有以下疾病的患者开发新的治疗策略： 基于组织抗原沉积物清除的艾滋病相关隐球菌病隐球菌的组织清除 将在正常和免疫缺陷小鼠中进行抗原检测以确定炎症的贡献 并模拟艾滋病患者的组织反应。我们的方法是评估现有的大型 收集单克隆抗体，以确定最有效的催化抗体，并探索抗体- 介导的催化作用影响隐球菌细胞。我们将使用Ab结合位点的定点诱变， 绘制催化结构域并产生具有无效催化活性的变体， 经典Ab功能与催化活性产生的功能之间的差异。催化抗体将被研究 以确定它们从组织中去除多糖的能力。提出了三个目标：1） 确定Ab介导的催化作用对CN囊膜的影响; 2.确定Ab介导的催化作用位点， 催化并产生具有和不具有催化活性的mAb;以及3）为了确定Ab-1的结果， 介导的GXM水解。我们预计，在这项工作完成后，我们将能够部署 艾滋病相关隐球菌病患者的新型抗体治疗。

Patients with advanced HIV infection are at risk for cryptococcosis, a devastating fungal infection that affects primarily the central nervous system in the form of a difficult to treat meningoencephalitis. Numerous studies over the past two decades have shown that antibody (Ab)-mediated immunity can make a critical contribution to host defense against Cryptococcus neoformans. Monoclonal antibodies (mAbs) are promising therapeutic reagents for cryptococcosis. This fungus is unusual among pathogenic fungi in that it has a large polysaccharide capsule that releases copious amounts of polysaccharide antigen into infected tissues, where it can interfere with the immune response and thus facilitate the persistence of infection. Tissue antigens are implicated in the pathogenesis of immune reconstitution inflammatory syndrome, which often complicates the rebound in immunity associated with antiretroviral therapy in patients with concurrent HIV and cryptococcal infection. Currently, there is no therapy to remove polysaccharide from tissues. Our group discovered that some mAbs to the C. neoformans capsule have catalytic activity that degrades the capsular polysaccharide. This is an exciting finding because it raises the possibility of developing a new type of therapy for cryptococcosis based on making cryptococcal cells vulnerable to the immune system by removing their capsule and degrading tissue antigen deposits. This application proposes experiments to ascertain the contribution of Ab-mediated catalysis to Ab-mediated protection with the goal of developing a new therapeutic strategy for patients with AIDS-associated cryptococcosis based on clearance of tissue antigen deposits. Tissue clearance of cryptococcal antigen will be done in both normal and immunodeficient mice to ascertain the contribution of inflammation to this effect and mimic tissue responses in patients with AIDS. Our approach is to evaluate a large existing collection of mAbs to identify the most effective catalytic Ab and explore the mechanisms by which Ab- mediated catalysis affects cryptococcal cells. We will use site directed mutagenesis of the Ab-binding site to map the catalytic domain and to generate variants with null catalytic activity that will allow us to discriminate between classical Ab functions from those resulting from catalytic activity. Catalytic antibodies will be studied in mouse models to ascertain their capacity to remove polysaccharide from tissue. Three aims are proposed: 1) To establish the effect of Ab-mediated catalysis on the capsule of CN; 2.To identify the site of Ab-mediated catalysis and generate mAbs with and without catalytic activity; and 3) To establish the consequences of Ab- mediated GXM hydrolysis.. We anticipate that at the completion of this work we will be in a position to deploy a new type of antibody therapy for patients with AIDS-related cryptococcosis.