Misumi Ichiro, Li You, Shirasaki Takayoshi, Yang Lixin, Kapustina Maryna, Lemon Stanley M, Whitmire Jason K
Department of Genetics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
Department of Pediatrics, The University of North Carolina at Chapel Hill, Chapel Hill, North Carolina, USA.
J Virol. 2025 Oct 23;99(10):e0139525. doi: 10.1128/jvi.01395-25. Epub 2025 Sep 19.
A limited number of studies on human subjects with type-A hepatitis have found a positive correlation between activated natural killer (NK) cell frequencies in blood and the severity of liver injury. However, without knowledge of differences in viral burdens, it remains unclear whether NK cells are elevated due to hepatitis A virus (HAV) replication and ongoing associated injury, or if NK cell responses directly cause pathogenesis. To gain insight into how NK cells respond during the early stages of hepatitis A virus infection, we generated mice that are permissive for HAV infection in the liver but are otherwise immunocompetent. HAV readily infected the liver of these hepatocyte-specific type-I interferon receptor knockout mice (), resulting in fecal virus shedding, elevated serum alanine aminotransferase levels, and immune cell infiltrates in the liver. Single-cell RNA sequencing analyses of liver leukocytes from infected mice revealed a rapid accumulation of activated NK cells in the liver within 2 days. HAV infection and liver inflammation were brief and substantially reduced in magnitude in these mice compared to global knockout mice that failed to induce substantial antiviral NK cell responses. NK cells were the principal source of interferon (IFN)-γ in mice. mice that were experimentally depleted of NK cells or IFN-γ showed greatly increased viral replication and liver damage. Moreover, IFN-γ alone was sufficient to suppress HAV replication in primary mouse hepatocytes. Collectively, these findings establish a critical role for type-I IFN induction of NK cells, their expression of IFN-γ, and protection against hepatitis A.IMPORTANCEHepatitis A virus remains a leading cause of foodborne illness among unvaccinated individuals. Infection can result in severe liver injury that can progress to fatal fulminant viral hepatitis. Despite its clinical significance, the molecular, genetic, and cellular factors influencing infection severity remain poorly understood. Previous studies of patient blood have suggested that natural killer (NK) cells cause liver injury during infection. In this study, we used mouse models of infection to characterize early cellular defenses to infection and identified a critical role for NK cells and interferon-γ in conferring rapid immune protection rather than pathogenesis.
对甲型肝炎人类受试者进行的有限数量研究发现，血液中活化自然杀伤（NK）细胞频率与肝损伤严重程度之间存在正相关。然而，在不了解病毒载量差异的情况下，尚不清楚NK细胞升高是由于甲型肝炎病毒（HAV）复制及持续相关损伤，还是NK细胞反应直接导致发病机制。为深入了解NK细胞在甲型肝炎病毒感染早期阶段的反应，我们培育了在肝脏中允许HAV感染但其他方面具有免疫活性的小鼠。HAV很容易感染这些肝细胞特异性I型干扰素受体敲除小鼠（）的肝脏，导致粪便病毒排出、血清丙氨酸转氨酶水平升高以及肝脏中的免疫细胞浸润。对感染小鼠肝脏白细胞进行的单细胞RNA测序分析显示，感染后2天内肝脏中活化NK细胞迅速积累。与未能诱导大量抗病毒NK细胞反应的全身性敲除小鼠相比，这些小鼠的HAV感染和肝脏炎症较为短暂且程度大幅降低。NK细胞是小鼠中干扰素（IFN）-γ的主要来源。实验性耗尽NK细胞或IFN-γ的小鼠显示病毒复制和肝损伤大幅增加。此外，单独的IFN-γ足以抑制原代小鼠肝细胞中的HAV复制。总体而言，这些发现确立了I型干扰素诱导NK细胞、其IFN-γ表达以及预防甲型肝炎方面的关键作用。重要性甲型肝炎病毒仍然是未接种疫苗个体食源性疾病的主要原因。感染可导致严重肝损伤，进而发展为致命的暴发性病毒性肝炎。尽管其具有临床意义，但影响感染严重程度的分子、遗传和细胞因素仍知之甚少。先前对患者血液的研究表明，自然杀伤（NK）细胞在感染期间会导致肝损伤。在本研究中，我们使用感染小鼠模型来表征对感染的早期细胞防御，并确定NK细胞和干扰素-γ在提供快速免疫保护而非发病机制方面的关键作用。
