In Situ Bioorthogonal Metabolic Labeling for Fluorescence Imaging of Virus Infection In Vivo

Optical fluorescence imaging is an important strategy to explore the mechanism of virus–host interaction. However, current fluorescent tag labeling strategies often dampen viral infectivity. The present study explores an in situ fluorescent labeling strategy in order to preserve viral infectivity and precisely monitor viral infection in vivo. In contrast to pre‐labeling strategy, mice are first intranasally infected with azide‐modified H5N1 pseudotype virus (N₃‐H5N1p), followed by injection of dibenzocyclooctyl (DBCO)‐functionalized fluorescence 6 h later. The results show that DBCO dye directly conjugated to N₃‐H5N1p in lung tissues through in vivo bioorthogonal chemistry with high specificity and efficacy. More remarkably, in situ labeling rather than conventional prelabeling strategy effectively preserves viral infectivity and immunogenicity both in vitro and in vivo. Hence, in situ bioorthogonal viral labeling is a promising and reliable strategy for imaging and tracking viral infection in vivo.