Role of antibodies in hepatitis E virus infection

摘要 这项拟议研究的目标是更好地了解抗体在HEV感染中的作用，并确定 抗体可以预防或治疗慢性戊型肝炎病毒(HEV)感染。HEV感染通常是自我限制的， 但当免疫系统受损时，感染往往会持续下去，如果不治疗，可能会导致 严重的肝病。HEV以两种不同的病毒粒子形式存在：进入粪便的裸露病毒粒子(NHEV)和 介导病毒在宿主和准包膜HEV(EHEV)之间的传播，这些病毒粒子在 血液流动和细胞间病毒传播的媒介。EHEV颗粒表面没有病毒抗原， 因此，它们对循环中的HEV特异性抗体具有抵抗力。我们之前展示了eHEV颗粒进入细胞 通过一种新的进入机制，涉及到病毒被膜的溶酶体降解。我们最近的数据显示 HEV特异性的Ig G而不是Ig M能有效地阻止eHEV在细胞培养中的传播。我们的中央 假说是抗体通过阻止病毒在细胞内脱壳而中和eHEV 病毒膜降解的内小体/溶酶体。由自然感染HEV产生的抗体和 用截短的HEV衣壳蛋白(CP)接种对HEV感染具有高度保护作用，而抗HEV 慢性戊型肝炎病毒感染者的抗体滴度通常较低。因此，抗体可能具有潜在的 预防或治疗慢性HEV感染。尽管有这些鼓舞人心的因素，但仍有几个重大障碍。 首先，HEV CP的C末端在目前的疫苗和粪便病毒中不存在，在 EHEV颗粒。这一点很重要，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，这可能会减少疫苗诱导的抗体 对eHEV有效。其次，我们最近的工作表明，HEV产生一种分泌的衣壳诱饵 大量来自受感染的细胞，并干扰抗体介导的中和。第三，抗体摄取 肝细胞移植是一个低效的过程。在这里，我们建议克服这些障碍。目标1将测试 假设针对CP完整的病毒粒子的抗体将更有效地阻止eHEV介导的传播。我们 将确定具有完整或裂解CP的正宗HEV病毒粒子的结构，并评估抗体是否针对 含有完整CP的病毒粒子能更有效地中和eHEV。我们还将确定糖工程抗体是否与 增强的溶酶体靶向更有效地中和eHEV。目标2将检验中和假设 不结合或结合不好的抗体将更有效地阻止HEV的传播。我们还将 用冷冻-电子显微镜测定抗体复合体中CP诱饵的结构 诱饵的躲避机制。拟议工作的完成将为以下方面提供新的见解 抗体在HEV感染中的作用和预防或治疗慢性HEV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.