Investigating Hepatitis C Virus Interactions with Host Lipid Pathways that are Critical for Viral Propagation Using Small Molecule Inhibitors and Chemical Biology Methods

Hepatitis C virus (HCV) is remarkably capable of efficiently hijacking host cell pathways including lipid metabolism in the liver in order to create pro-viral environments for pathogenesis. It is becoming increasingly clear that identifying small molecule inhibitors that target host factors exploited by the virus will expand available HCV treatment options. As such, a thorough understanding of host-virus interactions is critical to the development of alternative therapeutic strategies. Hepatic lipid droplets (LDs) are recruited by HCV to play essential roles in the viral lifecycle. The intracellular location of LDs is modified upon interacting with viral structural core protein. This enables formation of platforms that support viral particle assembly. Because these interactions are non-static, capturing its dynamic processes in order to better understand viral assembly can be achieved with label-free molecular imaging enhanced with live-cell capabilities. Chemical biology approaches that includes CARS microscopy employed in a multi-modal imaging system was used to probe interactions between HCV and host LDs. By successfully tracking LD trajectories, we identified core protein’s ability to alter LD speed and control for LD directionality. Using protein expression model systems that allowed for simultaneous tracking of core protein and LDs, our data revealed that mutations in the core protein region that vary in hydrophobicity and LD binding strengths, are factors that control for differential modulation of LD kinetics. Furthermore, we measured bidirectional LD travels runs and velocities, and observed critical properties by which core protein induces LD migration towards regions of viral particle assembly. Given that many steps in the HCV lifecycle are directly linked to host lipid metabolism, it is not surprising that disrupting lipid biosynthetic pathways would negatively affect viral replication. From this outlook, we explored small molecule inhibitors that targeted several lipid metabolic pathways to study its antiviral properties. Using fluorescent probes covalently labeled to viral RNA, we captured the visualization of disrupted replication complexes upon antagonizing nuclear hormone receptors that are linked to regulating lipid homeostasis. Correspondingly, biochemistry and molecular imaging techniques were also employed to identify novel antiviral mechanisms of small molecule inhibitors that target additional HCV-dependent lipid metabolic pathways