Investigation of Determinants Governing Hepatitis E Virus (HEV) Host Tropism and Identification and Characterization of Small Molecules Inhibiting HEV Replication

Abstract

Each year, hepatitis E virus (HEV) infections lead to an estimated 14 million symptomatic cases, resulting in approximately 300,000 human deaths and 5,200 stillbirths. While mortality rates in healthy individuals are around 2%, HEV causes death in ~30% of infected pregnant women, as well as chronic hepatitis in the immunocompromised (e.g. organ transplant recipients and HIV-positive patients). HEV is transmitted faeco-orally, often through contaminated water, and zoonotically, via consumption of undercooked pork meat. These modes of disease spread, along with nosocomial transmission from organ and blood donations, contribute to the status of HEV as a global threat to public health. The few explored medical treatments against HEV infection cause severe side effects while remaining only partially effective and unsafe for pregnant women and fetuses. My thesis addresses two important and unmet needs in the field: firstly, given the lack of a susceptible small animal model for in vivo HEV experimentation, we aimed to identify the determinants of HEV host tropism, particularly the basis for murine resistance. To achieve this, we developed a human-murine heterokaryon assay to discern whether positive human host factors or negative murine restriction factors are responsible for the observed tropic limitations of HEV. Our data suggest that one or more endogenous negative restriction factors in murine cells account for the inability of HEV to complete its life cycle in a murine host. Identification and inactivation of such (a) putative, antagonizing element(s) may aid in the development of an urgently needed mouse model suitable for antiviral drug testing and mechanistic studies of HEV-induced immune responses and pathology. Secondly, we aimed to identify compounds with novel antiviral properties against HEV infection. We designed and executed a high-throughput screen to select potential therapeutic candidates from a library of small molecules. In doing so, we identified a single promising hit that is non-toxic at functional doses and more potent than existing drug options. Our current efforts involve determining the drug’s mechanism of action, exploring the efficacy of closely related structural analogues, and testing the drug in physiologically relevant cell culture and animal models.