目的:维甲酸诱导基因I(RIG-I)样受体(RLRs),包括RIG-I,黑色素瘤分化相关蛋白5(MDA5),和遗传学和生理学2实验室(LGP2),有义病毒RNA诱导抗病毒干扰素(IFN)应答。LGP2,不能激活IFN应答本身,调制RIG-I和MDA5信令。HDV,一种引起病毒性肝炎最严重形式的小RNA病毒,由MDA5感知。IFN诱导的潜在机制及其对HDV复制的影响尚不清楚。这里,我们旨在揭示LGP2及其临床相关变体在这些过程中的作用.
方法:在HDV易感HepaRGNTCP细胞和原代人肝细胞中耗尽RLRs。重组细胞以表达不同的LGP2版本。HDV和IFN标志物以时间分辨方式定量。通过下拉测定进行LGP2、MDA5和RNA之间的相互作用研究。
结果:LGP2对于HDV感染后诱导的MDA5介导的IFN应答是必需的。这种诱导需要LGP2的RNA结合和ATP酶活性。IFN应答仅适度地减少静止细胞中的HDV复制,但极大地抑制细胞分裂介导的HDV传播。LGP2变体(Q425R),在发展不太严重的慢性丁型肝炎的非洲人中占主导地位,介导的可检测的更高的基础和更快的HDV诱导的IFN应答以及更强的HDV抑制。机械上,LGP2RNA结合是形成稳定的MDA5-RNA复合物的先决条件。Q425RLGP2变体增强了MDA5与RNA的结合。
结论:LGP2对于由HDV诱导的抗病毒IFN应答至关重要,并稳定下游信号传导所需的MDA5-RNA相互作用。天然的Q425RLGP2是一种功能获得变体,可能有助于丁型肝炎的减毒病程。
未经证实:HDV是慢性丁型肝炎的致病病原体,一种严重的病毒性肝炎,可导致肝硬化和肝细胞癌。一旦感染,人类免疫系统感知HDV并启动抗病毒干扰素(IFN)反应。这里,我们证明了免疫传感器LGP2与MDA5协作以建立抑制HDV复制的IFN应答。我们绘制了IFN系统激活所需的LGP2决定簇,并表征了LGP2的几种天然遗传变体。据报道,其中之一在撒哈拉以南非洲人中占主导地位,可以加速HDV诱导的IFN反应,认为遗传决定因素,可能包括LGP2,可能导致该人群疾病进展较慢.我们的结果有望促进对LGP2和先天免疫感应系统其他组件的遗传变异的进一步研究。包括评估它们对病毒感染过程的可能影响。
Retinoic acid inducible gene I (RIG-I)-like receptors (RLRs), including RIG-I, melanoma differentiation-associated protein 5 (MDA5), and laboratory of genetics and physiology 2 (LGP2), sense viral RNA to induce the antiviral interferon (IFN) response. LGP2, unable to activate the IFN response itself, modulates RIG-I and MDA5 signalling. HDV, a small RNA virus causing the most severe form of viral hepatitis, is sensed by MDA5. The mechanism underlying IFN induction and its effect on HDV replication is unclear. Here, we aimed to unveil the role of LGP2 and clinically relevant variants thereof in these processes.
RLRs were depleted in HDV susceptible HepaRGNTCP cells and primary human hepatocytes. Cells were reconstituted to express different LGP2 versions. HDV and IFN markers were quantified in a time-resolved manner. Interaction studies among LGP2, MDA5, and RNA were performed by pull-down assays.
LGP2 is essential for the MDA5-mediated IFN response induced upon HDV infection. This induction requires both RNA binding and ATPase activities of LGP2. The IFN response only moderately reduced HDV replication in resting cells but profoundly suppressed cell division-mediated HDV spread. An LGP2 variant (Q425R), predominating in Africans who develop less severe chronic hepatitis D, mediated detectably higher basal and faster HDV-induced IFN response as well as stronger HDV suppression. Mechanistically, LGP2 RNA binding was a prerequisite for the formation of stable MDA5-RNA complexes. MDA5 binding to RNA was enhanced by the Q425R LGP2 variant.
LGP2 is essential to mount an antiviral IFN response induced by HDV and stabilises MDA5-RNA interaction required for downstream signalling. The natural Q425R LGP2 is a gain-of-function variant and might contribute to an attenuated course of hepatitis D.
HDV is the causative pathogen of chronic hepatitis D, a severe form of viral hepatitis that can lead to cirrhosis and hepatocellular carcinoma. Upon infection, the human immune system senses HDV and mounts an antiviral interferon (IFN) response. Here, we demonstrate that the immune sensor LGP2 cooperates with MDA5 to mount an IFN response that represses HDV replication. We mapped LGP2 determinants required for IFN system activation and characterised several natural genetic variants of LGP2. One of them reported to predominate in sub-Saharan Africans can accelerate HDV-induced IFN responses, arguing that genetic determinants, possibly including LGP2, might contribute to slower disease progression in this population. Our results will hopefully prompt further studies on genetic variations in LGP2 and other components of the innate immune sensing system, including assessments of their possible impact on the course of viral infection.