MECHANISM OF ANTIBODY PROTECTION AGAINST C. NEOFORMANS

在美国，新型隐球菌导致8%的艾滋病患者发生致命的脑膜脑炎。 目前的治疗是不够的，因为10-20%的患者死于隐球菌性脑膜炎，尽管积极的 抗真菌治疗，并且在初始治疗期后存活的个体必须维持 终身治疗，以防止复发。由于这些治疗局限性， 作为C.新生儿感染。抗荚膜单克隆抗体 可以延长致死性感染小鼠的寿命，并增加体内抗真菌剂的有效性。 以前的观察表明，这些抗体的恒定区介导的功能是至关重要的 以确定其保护潜力。与这一想法相一致的是我们在1999年所做的初步研究。 显示抗体与某些Fc受体（FcR）的相互作用是重要的遗传缺陷小鼠 在介导保护中，虽然补体的存在可能对抗体效力有害， 特别是在没有FcR结合的情况下。在过去的几年里，我们建立了一个大型图书馆， 重组抗体具有多种不同的功能特性。我们现在将抗隐球菌 将可变区结合到这些抗体上，以检查单独和组合的这种可变区的贡献。 在动物模型中的FcR结合、补体激活、亲合力和半衰期等特征 感染C.新人类我们将首先在体外确认这些抗体的功能特性 通过检测FcR结合、抗体依赖性细胞介导的细胞毒性（ADCC）和补体激活 并测定其体内药代动力学。然后我们将测试抗C感染的体内功效。 新人类具体而言，我们将研究抗体效力是否取决于：i）在河流中的持久性，ii） 激活补体的能力，iii）FcR的接合，或iv）表面抗原的有效交联。的 这里提出的实验旨在探索具有不同抗体的假设。 功能特性的星座将具有不同程度的功效，小鼠感染C. 新生儿是一个特别相关的系统，因为鼠单克隆抗体目前正在经历 艾滋病患者隐球菌性脑膜炎治疗的I期评价。如果这次审判证明 有希望的是，所提出的实验将为选择最佳治疗候选物提供基础， 进一步研究明确定义与功效相关的属性应该使我们能够向前迈进 在设计用于治疗人类疾病的有效治疗性抗体方面。

Cryptococcus neoformans causes a lethal meningoencephalitis in 8% of AIDS patients in the US. Current treatment is inadequate as 10-20% of patients die from cryptococcal meningitis despite aggressive antifungal therapy, and individuals who survive beyond the initial treatment period must be maintained on life-long therapy to prevent relapse. Because of these therapeutic limitations, antibodies have been considered as prevention and treatment for C. neoformans infection. Anti-capsular monoclonal antibodies can prolong the life of lethally infected mice and increase the effectiveness of antifungal agents in vivo. Previous observations indicate that functions mediated by the constant regions of these antibodies are crucial in determining their protective potential. Consistent with this idea are preliminary studies we have done in genetically deficient mice showing that antibody interactions with certain Fc receptors (FcRs) are important in mediating protection, while the presence of complement may be detrimental to antibody efficacy, particularly in the absence of FcR binding. Over the past several years, we have developed a large library of recombinant antibodies with a variety of different functional properties. We will now graft anti-cryptococcal variable regions onto these antibodies to examine, both alone and in combination, the contribution of such characteristics as FcR binding, complement activation, avidity and half-life to efficacy in an animal model of infection with C. neoformans. We will first confirm the functional properties of these antibodies in vitro by testing FcR binding, antibody-dependant cell mediated cytotoxicity (ADCC), and complement activation and determine their pharmacokinetics in vivo. We will then test in vivo efficacy against infection with C. neoformans. Specifically, we will investigate whether antibody efficacy depends on: i) in rive persistence, ii) ability to activate complement, iii) engagement of FcRs, or iv) effective cross-linking of surface antigen. The experiments proposed here are designed to explore the hypothesis that antibodies with different constellations of functional properties will have differing degrees of efficacy, Murine infection with C. neoformans is a particularly relevant system because a murine monoclonal antibody is currently undergoing Phase I evaluation for the treatment of cryptococcal meningitis in AIDS patients. If this trial proves promising, the experiments proposed will provide the basis for selecting the best therapeutic candidate(s) for further study. A clear definition of what properties correlate with efficacy should allow us to move forward in designing effective therapeutic antibodies for treatment of disease in humans.