Exploring Crimean-Congo Hemorrhagic Fever Virus-Induced Hepatic Injury Using Antibody-Mediated Type I Interferon Blockade in Mice

Abstract

Crimean-Congo hemorrhagic fever virus (CCHFV) can cause severe hepatic injury in humans. However, the mechanism(s) causing this damage is poorly characterized. CCHFV produces an acute disease, including liver damage, in mice lacking type I interferon (IFN-I) signaling due to either STAT-1 gene deletion or disruption of the IFN-I receptor 1 gene. Here, we explored CCHFV-induced liver pathogenesis in mice using an antibody to disrupt IFN-I signaling. When IFN-I blockade was induced within 24 h postexposure to CCHFV, mice developed severe disease with greater than 95% mortality by 6 days postexposure. In addition, we observed increased proinflammatory cytokines, chemoattractants, and liver enzymes in these mice. Extensive liver damage was evident by 4 days postexposure and was characterized by hepatocyte necrosis and the loss of CLEC4F-positive Kupffer cells. Similar experiments in CCHFV-exposed NOD-SCID-γ (NSG), Rag2-deficient, and perforin-deficient mice also demonstrated liver injury, suggesting that cytotoxic immune cells are dispensable for hepatic damage. Some apoptotic liver cells contained viral RNA, while other apoptotic liver cells were negative, suggesting that cell death occurred by both intrinsic and extrinsic mechanisms. Protein and transcriptional analysis of livers revealed that activation of tumor necrosis factor superfamily members occurred by day 4 postexposure, implicating these molecules as factors in liver cell death. These data provide insights into CCHFV-induced hepatic injury and demonstrate the utility of antibody-mediated IFN-I blockade in the study of CCHFV pathogenesis in mice. IMPORTANCE CCHFV is an important human pathogen that is both endemic and emerging throughout Asia, Africa, and Europe. A common feature of acute disease is liver injury ranging from mild to fulminant hepatic failure. The processes through which CCHFV induces severe liver injury are unclear, mostly due to the limitations of existing small-animal systems. The only small-animal model in which CCHFV consistently produces severe liver damage is mice lacking IFN-I signaling. In this study, we used antibody-mediated blockade of IFN-I signaling in mice to study CCHFV liver pathogenesis in various transgenic mouse systems. We found that liver injury did not depend on cytotoxic immune cells and observed extensive activation of death receptor signaling pathways in the liver during acute disease. Furthermore, acute CCHFV infection resulted in a nearly complete loss of Kupffer cells. Our model system provides insight into both the molecular and the cellular features of CCHFV hepatic injury.

Fluorescent Crimean-Congo hemorrhagic fever virus illuminates tissue tropism patterns and identifies early mononuclear phagocytic cell targets in Ifnar-/- mice

“…Largely, our findings were consistent with reports in other mouse models. We saw a peripheral blood lymphopenia correlating with increasing disease severity, similar to observations made in Stat-1 -/- [5] and Rag2 -/mice [10], and increases in plasma levels of pro-inflammatory cytokines (IL-6 and IL-18) and chemoattractants (CCL2, CXCL1, and CXCL10) reported in the C57BL/6J (BL6) IFN-1-blockade disease model [10]. We did, however, note some variation in intensity of cytokine level changes than those reported in other mice.…”

“…In animal models of disease, identifying immunological parallels with and divergences from human disease is critical to support applicability of the model and guide translational studies. In addition to Ifnar -/mice, Stat-1 -/- [5], Rag2 -/mice [10], and NSG-SGM3 humanized [8] mice have been reported to develop clinical signs following CCHFV infection. Ifnar -/mice are deficient in type I IFN signaling; Stat-1 -/mice are deficient in type I, type II, and type III signaling; Rag2 -/mice are unable to generate mature T or B lymphocytes; and humanized mice have a variety of potential alterations to the immune response based on deficiencies in the mouse background and humanization approach.…”

“…Despite their limitations, IFN-deficient mice have been instrumental in facilitating the study of CCHFV pathogenesis in vivo. To date, dissemination of viral RNA and antigen in susceptible animals has been described using traditional techniques, such as PCR, immunohistochemistry (IHC), and in situ hybridization [7,8,10]. A limitation to studies using antibody-based staining techniques is the need for efficient co-staining processes to recognize and differentiate CCHFV epitopes from cellular epitopes; such studies can be challenging to both perform and interpret.…”

The Utility of Human Immune System Mice for High-Containment Viral Hemorrhagic Fever Research

“…Susceptibility to disease from CCHFV in mice has been limited to strains deficient in type I interferon responses [67,68]. These mice show a very rapid and highly lethal disease progression [69,70], which is likely largely due to their genetically defective antiviral response rather than a faithful recapitulation of human Crimean-Congo hemorrhagic fever (CCHF)-pathogenesis [70].…”

Crimean-Congo Hemorrhagic Fever Mouse Model Recapitulating Human Convalescence

“…These data suggest that host responses, although effective in controlling viral replication, may contribute to the severe tissue pathology seen in these mice. However, studies in mice deficient in adaptive immune responses demonstrated that mice could develop severe tissue pathology in the absence of cytolytic T-cell activity, suggesting this host response is dispensable for tissue damage following CCHFV infection (31). Further studies are needed to determine whether host responses to CCHFV infection contribute to the pathogenesis of CCHFV.…”