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，但可在免疫系统较弱的个体中持续存在，并导致快速进展为 肝硬变。HEV编码一个衣壳蛋白ORF2。然而，最近的研究表明，大多数ORF2 从感染HEV的细胞中释放的蛋白质与病毒颗粒无关。这个角色的确切角色(S) 分泌型ORF2(ORF2)的作用知之甚少，这阻碍了我们对HEV感染和 发病机制。我们最近发表的研究表明，ORF2和衣壳蛋白是两种不同的翻译 产品。ORF2特有的信号序列通过分泌途径引导其分泌，其中作为一种 保守但以前未被识别的内部起始密码子负责衣壳蛋白的翻译- 关联ORF2(ORF2c)。我们进一步发现，ORF2以糖基化二聚体的形式存在， 抗原与病毒粒子重叠，纯化的ORF2能够抑制抗体介导的HEV中和。 基于这些数据，我们假设ORF2作为诱饵来逃避宿主抗体反应 HEV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 免疫以及它是否在发病中起作用。此项目的目标是使用已建立的速率 模型，以测试ORF2在体内对HEV感染的作用(S)。目标1将确定是否消除ORF2表达 改变宿主抗体反应和急性HEV感染过程。目标2将确定血清ORF2是否 是否干扰抗体疗法治疗慢性戊型肝炎病毒感染，如果是的话，抗体疗法是否有效 将通过使用针对ORF2c而不是ORF2的抗体来改善。ORF2S的概念是作为一个 免疫诱饵是一种新的诱饵，对HEV的免疫逃避和持久性有重要意义。 预期的结果将填补我们在理解分泌型ORF2在HEV中的作用方面的一个重大空白 生命周期和发病机制，有可能在目前尚不存在治愈的情况下进行更有针对性的治疗。

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.