MECHANISM OF ANTIBODY PROTECTION AGAINST C. NEOFORMANS

描述（由申请人提供）：在美国，新型隐球菌引起8%的艾滋病患者致命的脑膜脑炎。 目前的治疗还不够，尽管进行了积极的抗真菌治疗，仍有10- 20%的患者死于隐球菌脑膜炎，并且在初始治疗期后存活的患者必须维持终生治疗以防止复发。由于这些治疗局限性，抗体被认为是预防和治疗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生命，并增加体内抗真菌药物的有效性。 先前的观察表明，这些抗体的恒定区介导的功能在决定其保护潜力方面至关重要。与这一想法一致的是我们在遗传缺陷小鼠中进行的初步研究，其显示抗体与某些Fc受体（FcR）的相互作用在介导保护中是重要的，而补体的存在可能对抗体功效有害，特别是在不存在FcR结合的情况下。在过去的几年里，我们已经开发了一个大型的重组抗体库，具有各种不同的功能特性。我们现在将抗隐球菌可变区移植到这些抗体上，以检查单独和组合的FcR结合、补体激活、亲合力和半衰期等特征对感染隐球菌的动物模型中的疗效的贡献。新人类 我们将首先通过测试FcR结合、抗体依赖性细胞介导的细胞毒性（ADCC）和补体激活来确认这些抗体的体外功能特性，并确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，我们将研究抗体功效是否取决于i）体内持久性，ii）激活补体的能力，iii）FcR的接合或iv）表面抗原的有效交联。 本文提出的实验旨在探索具有不同功能特性的抗体将具有不同程度的功效的假设。 小鼠感染C.新型隐球菌是一个特别相关的系统，因为鼠单克隆抗体目前正在进行治疗AIDS患者隐球菌脑膜炎的I期评价。 如果这项试验被证明是有希望的，那么所提出的实验将为选择最佳治疗候选者进行进一步研究提供基础。 明确定义与疗效相关的特性应该使我们能够在设计用于治疗人类疾病的有效治疗性抗体方面取得进展。

DESCRIPTION (provided by applicant): Cryptococcus neoformans causes a lethal meningoencephalitis in 8 percent of AIDS patients in the US. Current treatment is inadequate as 10-20 percent 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 vivo 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 candidates 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.