Metabolic labeling of enterovirus 71 with quantum dots for the study of virus receptor usage.

Fluorescent labeling and dynamic tracking is a powerful tool for exploring virus infection mechanisms. However, for small-sized viruses, virus tracking studies are usually hindered by a lack of appropriate labeling methods that do not dampen virus yield or infectivity. Here, we report a universal strategy for labeling viruses with chemical dyes and Quantum dots (QDs). Enterovirus 71 (EV71) was produced in a cell line that stably expresses a mutant methionyl-tRNA synthetase (MetRS), which can charge azidonorleucine (ANL) to the methionine sites of viral proteins during translation. Then, the ANL-containing virus was easily labeled with DBCO-AF647 and DBCO-QDs. The labeled virus shows sufficient yield and no obvious decrease in infectivity and can be used for imaging the virus entry process. Using the labeled EV71, different functions of scavenger receptor class B, member 2 (SCARB2), and heparan sulfate (HS) in EV71 infection were comparatively studied. The cell entry process of a strong HS-binding EV71 strain was investigated by real-time dynamic visualization of EV71-QDs in living cells. Taken together, our study described a universal biocompatible virus labeling method, visualized the dynamic viral entry process, and reported details of the receptor usage of EV71.