Neutralizing Antibodies to Hepatitis C

描述（由申请人提供）：干扰素和利巴韦林联合治疗已导致某些慢性HCV感染患者的临床改善。虽然聚乙二醇干扰素和利巴韦林已经实现了进一步的治疗改善，但当患者停止治疗时，病毒复制不能完全抑制，复发率高。治疗性人单克隆抗体（HMAb）是解决目前HCV感染治疗局限性的一种方法。大量IgG HCV HMAb的累积研究和初步发现支持这种方法的可行性。为了实现这一目标，HCV的一个关注点是感染性病毒体的显著部分是脂质包被的。这种观点认为，病毒粒子的低密度脂蛋白（LDL）包被可能限制了HCV包膜蛋白E1和E2被特异性抗体（Abs）识别的可用性。基于对HCV HMAb的初步研究，我们认为某些HCV E1和E2位点仍然可用于LDL包被病毒体上的Ab。基于我们先前的研究，我们假设介导病毒体进入靶细胞的E1和E2表位的特异性HMAbs比识别病毒体表面其他结构组分的Ab更有效地抑制病毒感染。其他关注点是HMAb介导的感染增强的理论可能性和HCV耐HMAb的逃逸突变体的出现。最近在建立支持持续HCV感染并产生感染性病毒体的人类细胞系方面的突破已经打开了对我们的HMAb进行详细功能表征和开发具有改善的病毒中和（Vn）活性的新型HMAb变体的途径。本项目的目标是系统地确定假设影响HCV Vn的关键参数的相互关系，并开发具有改善Vn活性的新一代治疗性抗体。HMAb的更高亲和力类似物的开发被提议作为改进中和的手段，因为具有改进的HCV结合强度的HMAb可能提供更稳定的感染保护。催化性抗体领域的最新技术发展使得开发特异性切割HCV E1和E2蛋白的抗体成为可能。从我们的HMAb中开发这种催化Ab是通过亚基改组方法提出的。催化抗体可以通过识别比常规抗体更广泛的表位来潜在地中和HCV，因为即使是功能上不重要的HCV位点的切割也会诱导产物片段中的主要构象转变。此外，催化功能应赋予HMAb多击能力，因为单个催化剂分子可重复用于切割病毒靶标的多个分子。

DESCRIPTION (provided by applicant): Therapy with combined interferon and ribavirin has led to clinical improvement for some patients with chronic HCV infection. Although further treatment improvements have been achieved with pegylated-interferon and ribavirin, viral replication is incompletely inhibited with a high relapse rate when patients discontinue treatment. Therapeutic human monoclonal antibodies (HMAbs) are an approach to address the limitations of current therapy for HCV infection. Accumulating studies and preliminary findings with a large panel of IgG HCV HMAbs support the feasibility of this approach. To achieve this goal, one concern for HCV is that a significant fraction of infectious virions are lipid coated. The view is that low density lipoprotein (LDL) coating of virions may limit the availability of HCV envelope proteins E1 and E2 for recognition by specific antibodies (Abs). Based on preliminary studies with HCV HMAbs, we believe that certain HCV E1 and E2 sites remain available to Abs on LDL-coated virions. Based on our previous studies, we hypothesize that specific HMAbs to E1 and E2 epitopes that mediate virion entry into target cells are more effective in suppressing viral infection than Abs that recognize other structural components of the virion surface. Other concerns are the theoretical possibility of HMAb mediated enhancement of infection and emergence of escape mutants of HCV resistant to HMAbs. The recent breakthroughs in establishing human cell lines that support persistent HCV infection and produce infectious virions have opened the route to detailed functional characterization of our HMAbs and development of novel HMAb variants that with improved virus neutralization (Vn) activity. The objectives of this project are to systematically determine the interrelationship of key parameters hypothesized to impact HCV Vn and develop new generation therapeutic Abs with improved Vn activity. Development of higher affinity analogs of the HMAbs is proposed as the means for improved neutralization, as HMAbs with improved HCV binding strength are likely to provide more stable protection from infection. Recent technological developments in the field of catalytic Abs have rendered feasible the development of Abs that specifically cleave HCV E1 and E2 proteins. Development of such catalytic Abs from our HMAbs is proposed by a subunit shuffling approach. The catalytic Abs can potentially neutralize HCV by recognizing a broader range of epitopes than conventional Abs, as cleavage of even functionally unimportant HCV sites should induce major conformational transitions in the product fragments. Moreover, the catalytic function should impart multi-hit capability to the HMAbs, as a single catalyst molecule is reused to cleave multiple molecules of the viral target.