Unraveling HBV Life Cycle by Fluorescent Microscopy Imaging

The hepatitis B virus (HBV) is a worldwide hepatotropic virus despite the availability of a highly effective vaccine. Currently, the most efficacious treatment against HBV infection is the use of interferon and nucleos(t)ide analogs, which effectively suppress viral replication but do not eradicate infection. Consequently, studies are still ongoing to identify novel molecules with antiviral properties. Interfering with HBV trafficking in infected cells is an approach that would greatly benefit from the diverse techniques of microscopy. However, several challenges arise in employing such techniques for HBV, given the unique characteristics of this virus. Notably, HBV predominantly produces non-infectious subviral particles in addition to infectious virions. Moreover, both virions and SVPs are small objects, measuring only 20 to 40 nm, which challenges their observation using conventional optical microscopy. Additional obstacles include the small size of the HBV genome and its high compaction, which restrict reverse genetics and the introduction of DNA sequences coding for fluorescent polypeptides. In this review, we will provide an overview of ongoing research efforts aimed at visualizing the different stages of the HBV life cycle within infected cells. Furthermore, we will explore solutions successfully applied to the visualization of other viruses that could potentially be adapted to HBV.