Kupffer Cells In Action: Understanding The Mechanisms Of Hepadnaviral Persistence
Date
2023-06
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Abstract
Hepatitis B virus (HBV) is the prototypical member of Hepadnaviridae family, and a causative agent of liver disease. Despite the availability of a vaccine, an estimated 1.5 million new individuals become infected each year. HBV can establish persistent infection in hepatocytes, which can disrupt hepatic homeostasis. Kupffer cells (KCs) are liver-resident macrophages that act as the first of line of defense against infectious agents. Woodchuck hepatitis virus (WHV) is a member of Hepadnaviridae. North American woodchucks (Marmota monax) infected with WHV present a natural immunocompetent model and demonstrate comparable infection outcomes and progression to hepatocellular carcinoma. We hypothesized that KC absence in acute viral hepatitis leads to chronicity by impacting virus processing and immune responses. To investigate this, we sought to uncover the early host-virus interactions in acute WHV infection. We designed and optimized in-house WHV and woodchuck-specific assays to assess intrahepatic and systemic virus presence following WHV challenge (<24 hours) and infection (6 weeks). An intravital imaging protocol was developed to capture real-time events in a living woodchuck using purified and fluorescently labelled WHV. Clodronate liposome-mediated depletion of KCs in woodchucks was performed to evaluate pre-acute challenge and acute infection in either the presence or absence of KCs. Intravital imaging of woodchucks challenged with WHV showed first appearance of virus in the liver within 30 seconds and capture by KCs within 5-10 minutes. In addition, depletion of KCs did not impact the localization of WHV during the initial hour or 24 hours of challenge. Assessment of WHV markers, serology and liver histology revealed differences in viral and biochemical markers between the KC-depleted and non-depleted animals over the initial 6 weeks. KC depletion, prior to acute WHV infection, resulted in faster onset of acute hepatitis (elevated liver enzymes) and greater suppression of WHV DNA (in circulation and intrahepatically). However, there was no difference in WHV DNA suppression between KC-depleted and non-depleted cohorts after 6 weeks p.i, as all assayed woodchucks achieved suppression of plasma WHV DNA. This may suggest that KCs normally operate under tolerogenic conditions to prevent hepatocyte damage and hepatitis, allowing for greater viral replication and immune evasion.
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Keywords
Woodchuck Hepatitis Virus (WHV), Hepatitis B Virus (HBV), Hepadnavirus, Kupffer Cells, Innate Immunity, Intravital Microscopy (IVM)
Citation
Al-Yasiri, L. (2023). Kupffer cells in action: understanding the mechanisms of Hepadnaviral persistence (Master's thesis, University of Calgary, Calgary, Canada). Retrieved from https://prism.ucalgary.ca.