Role of a secreted form of ORF2 protein in hepatitis E virus infection

摘要 肠道传播的戊型肝炎病毒（HEV）每年感染约2000万人。HEV感染通常是 自我解决，但可以持续在个人与免疫系统减弱，并导致快速进展到 肝硬化患者HEV编码单个衣壳蛋白ORF 2。尽管如此，最近的研究表明，大多数ORF2 从HEV感染的细胞释放的蛋白质与病毒颗粒无关。的确切作用 分泌型ORF2（ORF2s）的作用知之甚少，这阻碍了我们对HEV感染的理解， 发病机制我们最近发表的工作表明，ORF2和衣壳是两种不同的翻译， 产品. ORF2s特有的信号序列通过分泌途径指导其分泌，其中作为一个信号序列， 保守的，但以前未被识别的，内部起始密码子负责衣壳的翻译， 相关ORF 2（ORF2c）。我们进一步发现ORF2以糖基化二聚体的形式存在， 抗原重叠的病毒粒子，和纯化的ORF2能够抑制抗体介导的中和HEV。 基于这些数据，我们假设ORF2作为诱饵，以逃避宿主抗体反应， 戊型肝炎病毒感染。我们的长期目标是更好地了解ORF2如何调节HEV感染和宿主 免疫力和是否有助于发病机制。本项目的目标是使用既定的 模型以测试ORF2在HEV感染中的体内作用。目的1将确定是否消除ORF2s表达 改变宿主抗体反应和急性HEV感染的过程。目标2将确定血清ORF2 干扰慢性HEV感染的抗体治疗，如果是，抗体治疗的有效性 将通过使用靶向ORF2c而不是ORF2s的抗体来改善。ORF2S作为一种 免疫诱饵是新的，并可能有重要的意义戊型肝炎病毒免疫逃避和持久性。 预期的结果将填补我们对分泌型ORF2在HEV中的作用的理解的重大空白 生命周期和发病机制，具有更有针对性的治疗潜力，目前还没有治愈。

Abstract The enterically transmitted hepatitis E virus (HEV) infects ~20 million people annually. HEV infection is usually self-resolving but can persist in individuals with a weakened immune system and result in fast progression into liver cirrhosis. HEV encodes a single capsid protein ORF2. Nonetheless, recent studies show that most ORF2 proteins released from HEV-infected cells are not associated with virus particles. The exact role(s) of the secreted ORF2 (ORF2s) plays is poorly understood, which hampers our understanding of HEV infection and pathogenesis. Our recently published work demonstrated that ORF2s and the capsid are two different translation products. A signal sequence unique to ORF2s directs its secretion via the secretory pathway, where as a conserved, but previously unrecognized, internal start codon is responsible for translation of the capsid- associated ORF2 (ORF2c). We further found that ORF2s exists as a glycosylated dimer with substantial antigenic overlap with the virion, and purified ORF2s was able to inhibit antibody-mediated neutralization of HEV. Based on these data, we hypothesize that ORF2s acts as a decoy to evade the host antibody response during HEV infection. Our long-term goal is to better understand how ORF2s modulates HEV infection and host immunity and whether it contributes to pathogenesis. The objectives of this project are to use an established rat model to test the in vivo role(s) of ORF2s in HEV infection. Aim 1 will determine if eliminating ORF2s expression alters host antibody responses and the course of acute HEV infection. Aim 2 will determine if serum ORF2s interferes with antibody therapy of chronic HEV infection, and if so whether the effectiveness of antibody therapy will be improved by using antibodies that target ORF2c but not ORF2s. The concept that ORF2S functions as an immunological decoy is novel and may have important implications for HEV immune evasion and persistence. The expected outcomes will fill a significant gap in our understanding of the role of secreted ORF2 in the HEV life cycle and pathogenesis with the potential for more targeted therapies where no cure currently exists.