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Viral protease cleavage of MAVS in genetically modified mice with hepatitis A virus infection
Journal of Hepatology ( IF 25.7 ) Pub Date : 2022-09-22 , DOI: 10.1016/j.jhep.2022.09.013
Lu Sun 1 , Hui Feng 1 , Ichiro Misumi 2 , Takayoshi Shirasaki 1 , Lucinda Hensley 1 , Olga González-López 1 , Itoe Shiota 2 , Wei-Chun Chou 1 , Jenny P-Y Ting 3 , John M Cullen 4 , Dale O Cowley 5 , Jason K Whitmire 6 , Stanley M Lemon 7
Affiliation  

Background & Aims

Consistent with its relatively narrow host species range, hepatitis A virus (HAV) cannot infect C57BL/6 mice. However, in Mavs-/- mice with genetic deficiency of the innate immune signaling adaptor MAVS, HAV replicates robustly in the absence of disease. The HAV 3ABC protease cleaves MAVS in human cells, thereby disrupting virus-induced IFN responses, but it cannot cleave murine MAVS (mMAVS) due to sequence differences at the site of scission. Here, we sought to elucidate the role of 3ABC MAVS cleavage in determining HAV pathogenesis and host species range.

Methods

Using CRISPR/Cas9 gene editing, we established two independent lineages of C57BL/6 mice with knock-in mutations altering two amino acids in mMAVS (‘mMAVS-VS’), rendering it susceptible to 3ABC cleavage without loss of signaling function. We challenged homozygous Mavsvs/vs mice with HAV, and compared infection outcomes with C57BL/6 and genetically deficient Mavs-/- mice.

Results

The humanized murine mMAVS-VS protein was cleaved as efficiently as human MAVS when co-expressed with 3ABC in Huh-7 cells. In embyronic fibroblasts from Mavsvs/vs mice, mMAVS-VS was cleaved by ectopically expressed 3ABC, significantly disrupting Sendai virus-induced IFN responses. However, in contrast to Mavs-/- mice with genetic MAVS deficiency, HAV failed to establish infection in Mavsvs/vs mice, even with additional genetic knockout of Trif or Irf1. Nonetheless, when crossed with permissive Ifnar1-/- mice lacking type I IFN receptors, Mavsvs/vsIfnar1-/- mice demonstrated enhanced viral replication coupled with significant reductions in serum alanine aminotransferase, hepatocellular apoptosis, and intrahepatic inflammatory cell infiltrates compared with Ifnar1-/- mice.

Conclusions

MAVS cleavage by 3ABC boosts viral replication and disrupts disease pathogenesis, but it is not by itself sufficient to break the host-species barrier to HAV infection in mice.

Impact and implications

The limited host range of human hepatitis viruses could be explained by species-specific viral strategies that disrupt innate immune responses. Both hepatitis A virus (HAV) and hepatitis C virus express viral proteases that cleave the innate immune adaptor protein MAVS, in human but not mouse cells. However, the impact of this immune evasion strategy has never been assessed in vivo. Here we show that HAV 3ABC protease cleavage of MAVS enhances viral replication and lessens liver inflammation in mice lacking interferon receptors, but that it is insufficient by itself to overcome the cross-species barrier to infection in mice. These results enhance our understanding of how hepatitis viruses interact with the host and their impact on innate immune responses.



中文翻译:

甲型肝炎病毒感染的转基因小鼠中病毒蛋白酶对 MAVS 的裂解

背景与目标

与其相对较窄的宿主物种范围一致,甲型肝炎病毒 (HAV) 不能感染 C57BL/6 小鼠。然而,在先天免疫信号适配器 MAVS 遗传缺陷的Mavs -/-小鼠中,HAV 在没有疾病的情况下会强劲复制。HAV 3ABC 蛋白酶可裂解人类细胞中的 MAVS,从而破坏病毒诱导的IFN 反应,但由于裂解位点的序列差异,它无法裂解小鼠 MAVS (mMAVS)。在这里,我们试图阐明 3ABC MAVS 裂解在确定 HAV 发病机制和宿主物种范围中的作用。

方法

使用 CRISPR/Cas9 基因编辑,我们建立了两个独立的 C57BL/6 小鼠谱系,其敲入突变改变了 mMAVS (“mMAVS-VS”) 中的两个氨基酸,使其易于受到 3ABC 切割而不会丧失信号功能。我们用 HAV 攻击纯合Mavs vs/vs小鼠,并比较了 C57BL/6 和遗传缺陷Mavs -/-小鼠的感染结果。

结果

当在 Huh-7 细胞中与 3ABC 共表达时,人源化鼠 mMAVS-VS 蛋白的切割效率与人 MAVS 一样。在Mavs vs/vs小鼠的胚胎成纤维细胞中,mMAVS-VS 被异位表达的 3ABC 裂解,显着破坏仙台病毒诱导的 IFN 反应。然而,与具有 MAVS 遗传缺陷的Mavs -/-小鼠相比,即使额外敲除TrifIrf1基因,HAV 也未能在Mavs vs/vs小鼠中建立感染。尽管如此,当与缺乏 I 型 IFN 受体的允许性Ifnar1 -/-小鼠杂交时,与Ifnar1相比, Mavs vs/vs Ifnar1 -/-小鼠表现出病毒复制增强,同时血清丙氨酸氨基转移酶、肝细胞凋亡和肝内炎症细胞浸润显着减少。 -/-老鼠。

结论

3ABC 切割 MAVS 会促进病毒复制并破坏疾病发病机制,但其本身不足以打破小鼠体内 HAV 感染的宿主物种屏障。

影响和影响

人类肝炎病毒的宿主范围有限可以用破坏先天免疫反应的物种特异性病毒策略来解释。甲型肝炎病毒 (HAV) 和丙型肝炎病毒都表达病毒蛋白酶,可在人类而非小鼠细胞中裂解先天免疫接头蛋白 MAVS。然而,这种免疫逃避策略的影响从未在体内进行过评估。在这里,我们表明,HAV 3ABC 蛋白酶切割 MAVS 可以增强病毒复制并减轻缺乏干扰素受体的小鼠的肝脏炎症,但其本身不足以克服小鼠的跨物种感染障碍。这些结果增强了我们对肝炎病毒如何与宿主相互作用及其对先天免疫反应的影响的理解。

更新日期:2022-09-22
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