Probes for INS

Crimean-Congo hemorrhagic fever virus (CCHFV) can cause severe hepatic injury in humans. However, the mechanism(s) causing this damage are poorly characterized. CCHFV produces an acute disease, including liver damage, in mice lacking type I interferon signaling (IFN-I) either due to 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 post-exposure to CCHFV, mice developed severe disease with greater than 95% mortality by six days post-exposure. In addition, we observed increased proinflammatory cytokines, chemoattractants, and liver enzymes in these mice. Extensive liver damage was evident by 4 days post-exposure and was characterized by hepatocyte necrosis and 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 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 TNF superfamily members occurred by day four post-exposure, 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 are 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 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 near complete loss of Kupffer cells. Our model system provides insight into both the molecular and cellular features of CCHFV hepatic injury.

Crimean-Congo haemorrhagic fever (CCHF) is the most medically significant tick-borne disease, being widespread in the Middle East, Asia, Africa and parts of Europe 1 . Increasing case numbers, westerly movement and broadly ranging case fatality rates substantiate the concern of CCHF as a public health threat. Ixodid ticks of the genus Hyalomma are the vector for CCHF virus (CCHFV), an arbovirus in the genus Orthonairovirus of the family Nairoviridae. CCHFV naturally infects numerous wild and domestic animals via tick bite without causing obvious disease2,3. Severe disease occurs only in humans and transmission usually happens through tick bite or contact with infected animals or humans. The only CCHF disease model is a subset of immunocompromised mice4-6. Here, we show that following CCHFV infection, cynomolgus macaques exhibited hallmark signs of human CCHF with remarkably similar viral dissemination, organ pathology and disease progression. Histopathology showed infection of hepatocytes, endothelial cells and monocytes and fatal outcome seemed associated with endothelial dysfunction manifesting in a clinical shock syndrome with coagulopathy. This non-human primate model will be an invaluable asset for CCHFV countermeasures development.