Role of antibodies in hepatitis E virus infection

总结 这项研究的目的是更好地了解抗体在HEV感染中的作用，并确定抗体是否与HEV感染有关。 抗体可以预防或治疗慢性戊型肝炎病毒（HEV）感染。HEV感染通常是自限性的， 但当免疫系统受损时，感染经常持续存在，如果不治疗，可能导致 严重的肝病。HEV以两种不同的病毒体形式存在：脱落到粪便中的裸病毒体（nHEV）和 介导宿主之间的病毒传播，以及在宿主中循环的准包膜HEV（eHEV）病毒体。 血液和介导病毒在细胞间传播。eHEV颗粒表面缺乏病毒抗原， 因此它们对循环的HEV特异性抗体具有抗性。我们先前表明eHEV颗粒进入细胞 通过一种新的进入机制，涉及病毒包膜的溶酶体降解。我们最近的数据显示 HEV特异性IgG，而不是IgM，有效地阻断eHEV介导的细胞培养物中的传播。我们的中央 假设是抗体通过阻止细胞内病毒的脱壳而在细胞内中和eHEV。 内体/溶酶体，其中病毒膜降解。天然HEV感染产生的抗体， 用截短的HEV衣壳蛋白（CP）接种对HEV感染具有高度保护性，而抗HEV 慢性HEV感染患者的抗体滴度通常较低。因此，抗体可能有潜力， 预防或治疗慢性HEV感染。尽管作出了这些努力，但仍存在一些重大障碍。 首先，HEV CP的C末端，其不存在于当前的疫苗和粪便病毒中，在疫苗中是完整的。 eHEV颗粒这是重要的，因为结构建模表明，C末端的存在， CP显著改变了病毒粒子的表面结构，这可能使疫苗诱导的抗体减少， 对eHEV有效。其次，我们最近的工作表明，HEV产生一个衣壳诱饵， 从感染的细胞中大量释放并干扰抗体介导的中和。第三，抗体摄取 是一个低效的过程。在此，我们建议克服这些障碍。目标1将测试 假设靶向具有完整CP的病毒体的抗体将更有效地阻断eHEV介导的传播。我们 将确定具有完整或裂解CP的真实HEV病毒体的结构，并评估抗体是否靶向 具有完整CP的病毒粒子更有效地中和eHEV。我们还将确定糖工程抗体是否具有 增强的溶酶体靶向更有效地中和eHEV。目标2将检验以下假设： 不与诱饵结合或结合差的抗体将更有效地阻断HEV传播。我们还将 通过冷冻电镜确定与抗体复合的CP诱饵的结构，以获得更好的理解 诱饵的逃避机制完成拟议的工作将提供新的见解， 抗体在戊型肝炎病毒感染中作用以及预防或治疗慢性戊型肝炎病毒感染的策略。

Summary The goal of the proposed study is to better understand the role of antibodies in HEV infection and determine if antibodies can prevent or cure chronic hepatitis E virus (HEV) infection. HEV infections are usually self-limited, but the infections frequently persist when the immune system is compromised and if left untreated, can lead to serious liver disease. HEV exists in two distinct virion forms: naked virions (nHEV) that are shed into feces and mediate virus transmission between hosts, and quasi-enveloped HEV (eHEV) virions that circulate in the bloodstream and mediate virus spread between cells. The eHEV particles lack viral antigens on their surface, thus they are resistant to circulating HEV-specific antibodies. We previously show that eHEV particles enter cells via a novel entry mechanism that involves lysosomal degradation of the viral envelope. Our recent data show that HEV-specific IgG, but not IgM, effectively block eHEV-mediated spread in cell culture. Our central hypothesis is that antibodies neutralize eHEV intracellularly by preventing virus uncoating in the endosome/lysosome where the viral membrane degrades. Antibodies generated by natural HEV infection and vaccination with truncated HEV capsid proteins (CP) are highly protective against HEV infection, while anti-HEV antibody titers are usually low in patients with chronic HEV infection. Thus, antibodies may have the potential to prevent or treat chronic HEV infection. Despite these encouragements, there are several significant roadblocks. First, the C terminus of the HEV CP, which is not present in the current vaccine and the fecal virus, is intact in the eHEV particles. This is important since structural modeling suggests that the presence of the C terminus of CP significantly alters the surface structure of the virion which likely makes vaccine-induced antibodies less effective against eHEV. Second, our recent work indicates that HEV produces a capsid decoy that is secreted from infected cells in a large quantity and interferes with antibody-mediated neutralization. Third, antibody uptake by hepatocytes is an inefficient process. Here we propose to overcome these obstacles. Aim 1 will test the hypothesis that antibodies targeting virions with intact CP will block eHEV-mediated spread more efficiently. We will determine the structure of authentic HEV virions with intact or cleaved CP and assess if antibodies targeting virions with intact CP neutralize eHEV more efficiently. We will also determine if glycoengineered antibodies with enhanced lysosomal targeting neutralize eHEV more efficiently. Aim 2 will test the hypothesis that neutralizing antibodies that do not bind or bind poorly to the decoy will block HEV spread more efficiently. We will also determine the structure of the CP decoy in complex with antibodies by cryo-EM to gain a better understanding of the evasion mechanism by the decoy. The completion of the proposed work will provide novel insights into the role of antibodies in HEV infection and inform strategies to prevent or cure chronic HEV infection.