Neutralizing Antibodies to Hepatitis C

描述(申请人提供)：干扰素和利巴韦林的联合治疗已导致一些慢性丙型肝炎病毒感染患者的临床改善。尽管聚乙二醇化干扰素和利巴韦林的治疗取得了进一步的改善，但病毒复制并未完全被抑制，当患者停止治疗时，复发率很高。治疗性人类单抗(HMAbs)是解决目前丙型肝炎病毒感染治疗局限性的一种方法。对大量的免疫球蛋白、丙型肝炎病毒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，丙型肝炎病毒的一个担忧是，相当大一部分感染性病毒粒子是被脂类包裹的。有观点认为，低密度脂蛋白(LDL)包裹在病毒粒子上可能会限制丙型肝炎病毒包膜蛋白E1和E2被特异性抗体(Abs)识别的可能性。基于对丙型肝炎病毒HMAb的初步研究，我们认为，在低密度脂蛋白包裹的病毒粒子上，某些丙型肝炎病毒E1和E2位点仍然可供抗体使用。根据我们以前的研究，我们假设，与识别病毒粒子表面其他结构成分的抗体相比，介导病毒粒子进入靶细胞的针对E1和E2表位的特异性HMAb在抑制病毒感染方面更有效。其他令人担忧的问题是HMAb介导的感染增强和抗HMAb的丙型肝炎病毒逃逸突变出现的理论可能性。最近在建立支持持续丙型肝炎病毒感染和产生感染性病毒粒子的人类细胞系方面的突破，为详细描述我们的HMAb的功能和开发具有改进的病毒中和(VN)活性的新型HMAb变体开辟了道路。该项目的目标是系统地确定影响丙型肝炎病毒VN的关键参数之间的相互关系，并开发具有改善VN活性的新一代治疗性抗体。建议开发更高亲和力的HMAb类似物作为改进中和的手段，因为具有更好的丙型肝炎病毒结合强度的HMAb可能提供更稳定的感染保护。最近催化抗体领域的技术发展已经使开发特异性切割丙型肝炎病毒E1和E2蛋白的抗体成为可能。从我们的HMAbs发展这种催化抗体是通过亚基改组方法提出的。催化抗体通过识别比常规抗体更广泛的表位而潜在地中和丙型肝炎病毒，因为即使是功能上不重要的丙型肝炎病毒位点的切割也会在产物片段中诱导主要的构象转变。此外，催化功能应该赋予HMAbs多次命中的能力，因为单个催化剂分子被重复使用来裂解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.