Progress on the labeling and single-particle tracking technologies of viruses

Abstract

Understanding and unravelling the invasion mechanisms of virus infection is of high importance for preventing and treating viral diseases. Single-virion tracking is a powerful way for exploring the mechanisms of viral infection. For successful tracking, the virus and cellular structures of interest must be fluorescently labeled; the microscope imaging technology must be sufficiently powerful for real-time single virion or viral component tracking. All fields of scientists have made great efforts and improvements. Here we will review the recent advances in virus labeling and the emerging fluorescence imaging technologies used in the imaging and tracking of viruses.

Click labeling of unnatural sugars metabolically incorporated into viral envelope glycoproteins enables visualization of single particle fusion

“…Single virus imaging has emerged as a powerful tool to delineate the virus entry pathways into host cells in spite of virus heterogeneity and the stochastic nature of viral fusion. A number of virus labeling strategies suitable for imaging single particle entry have been introduced and validated in the recent years (reviewed in (Brandenburg and Zhuang, 2007; Huang and Xie, 2014)). Among these, tagging viral proteins with GFP or other fluorescent proteins and incorporation of lipophilic dyes into the viral membrane have been most widely implemented (see for example (Burdick, Hu, and Pathak, 2013; Ewers et al, 2005; Floyd et al, 2008; Lakadamyali et al, 2003; Lampe et al, 2007; McDonald et al, 2002; Miyauchi et al, 2009)).…”

Visualization of hepatitis B virus entry – novel tools and approaches to directly follow virus entry into hepatocytes

“…Multicolour labelling of both virus particles and cellular structures reveal better insights into virus–host interactions. Multicolour labelling of different viral structural proteins also allows direct visualization of disassembly events such as membrane fusion, capsid release and the movement of subviral particles . As convenient cell culture systems for HBV and HDV infection have now been established, the contribution of virus and host factors can be evaluated by direct visualization approaches using genetically manipulated and fluorescently labelled virions or host factors.…”

“…Many fluorophores like fluorescent proteins (FPs) and chemical dyes are available, and multiple labelling strategies have been developed. Such techniques have been successfully applied to study the entry of viruses such as human immunodeficiency virus (HIV) and influenza virus . For several reasons, it is difficult to apply these techniques for HBV.…”

Seeing the unseen: Imaging rotation in cells with designer anisotropic particles

“…It has been widely used to measure complex cell dynamics and interactions (Kusumi et al, 2014; Saxton and Jacobson, 1997). Rapid progress in high-resolution optical imaging and real-time tracking techniques has led to many exciting discoveries that would have been impossible to achieve with traditional ensemble-average techniques (Ruthardt et al, 2011; Huang and Xie, 2014; Wang and Tao, 2013). For example, such techniques have revealed the “walking” mechanisms of motor proteins, such as kinesins (Yildiz et al, 2004; Asbury et al, 2003; Visscher et al, 1999), dyneins (Toba et al, 2006; DeWitt et al, 2012), and myosins (Yildiz et al, 2003; Warshaw et al, 2005), along cytoskeletal filaments with unprecedented resolution.…”