Characterization of neutralizing antibody responses in HCV infected individuals.

丙型肝炎病毒是一种主要的人类病原体，全世界有2亿人感染。目前，没有预防感染的疫苗，治疗方案也只是部分有效。最初的丙型肝炎病毒感染通常是无症状的，30%的人会自动清除病毒。其余70%的人发展为终身慢性感染，导致进行性肝病、肝硬化，在某些情况下还会导致肝癌。有些人能够清除病毒的原因被认为是由于产生了强烈的细胞免疫反应，而抗体被认为在实现病毒清除方面起着监测作用。然而，测量HCV感染患者的抗体反应通常使用传统的诊断测试，而不测量有助于中和和清除病毒的抗体。我们已经开发了一种准确测量患者血清中NAb水平的检测方法。我们发现，慢性感染患者具有广泛反应性中和抗体，但自然清除病毒或通过治疗清除病毒的患者没有广泛反应性中和抗体。这一现象的可能解释是，在感染早期，抗体往往仅对感染病毒具有特异性，因此，为了检测中和抗体，必须检查同源病毒序列。此外，我们已经发现证据表明HCV可以通过掩盖抗体结合的位点来逃避中和抗体。我们拟探讨急性感染患者是否会发生对自身病毒序列的NAb，以及这些病毒序列和抗体滴度在整个感染和治疗过程中如何变化。我们还计划通过使用抗性HCV糖蛋白的诱变来确定中和抗性的机制。这些研究旨在全面了解抗体在HCV感染中的真正作用及其对病毒进化的影响。

Hepatitis C virus is a major human pathogen infecting 200 million people world-wide. Currently, there is no vaccine to prevent infection and treatment regimes are only partially effective. IInitial HCV infection is frequently asymptomatic and 30% of people spontaneously clear the virus. The remaining 70% of people develop a life-long chronic infection that causes progressive liver disease, cirrhosis and in some cases liver cancer. The reason why some people are able to clear virus has been attributed to the development of a strong cellular immune response and antibody is belived to play a monir role in achieving viral clearance. However, measurememnt of antibody responses in HCV infected pateints is routinely performed using conventional diagnostic tests that do not measure antibody that can help neutralize and clear virus. We have developed an assay that accurately measures the level of NAb in patient sera. We have found that chronically infected patients have broadly reactive neutralizing antibodies but that patients who clear virus, naturally or through treatment do not have broadly reactive neutralizing antibodies. Possibly explaining this phenomenon is that early during infection, antibody is frequently specific only to the infecting virus therefore to detect neutralizing antibodies, homologous viral sequences must be examined. In addition, we have found evidence that HCV can evade neutralzing antibodies through masking of sites to which antibodies bind. We propose to explore whether acutely infected patients develop NAb to autologous viral sequences, and how do these viral sequences and the antibody titre change throughout the course of infection and treatment. We also plan to determine the mechanism of neutralization resistance through the use of mutagenesis of resistant HCV glycoproteins. These studies are aimed at gaining a thorough understanding of the true role of antibody in HCV infection and its influence on viral evolution.