Equipping inner central components of influenza A virus with quantum dots.

Influenza A virus (IAV), a risk to public health, is enveloped and contains viral ribonucleoprotein (vRNP) complexes, where vRNP complexes are central to every aspect of the IAV life cycle. Labeling both the vRNP complexes and viral envelope with quantum dots (QDs) is conducive to achieving global long-term tracking of a single IAV infecting host cell, which has potential to provide valuable information for revealing mechanisms of IAV infection. However, even though some strategies for labeling of the viral envelope with QDs have been developed, there are few strategies for coupling of QDs to the vRNP complexes inside IAV so far. Herein, we devised a convenient electroporation-based strategy, coupled with antibody binding, to transfer green QDs-labeled nucleoprotein antibodies (GQDs-NPAb) into H1N1 and achieved the labeling of vRNP complexes with QDs [H1N1(GQDs)]. Under the optimal condition of 20 nM GQDs-NPAb and a single pulse with 20 ms duration and 750 V/cm pulse intensity, the actual efficiency of labeling is ca. 34% and H1N1(GQDs) can retain 93% infectivity. Then, dual labeling of H1N1 was realized by labeling the envelope of H1N1(GQDs) with red QDs (RQDs) via a mild and efficient hydrazine-aldehyde-based strategy. At the optimal RQDs concentration of 5 nM, the actual efficiency of dual labeling can reach to 11% and the dual-labeled H1N1 can retain 93% infectivity. Because of the similar components and structure of different IAV subtypes, this dual-labeling strategy is applicable to other subtypes of IAV, e.g., H9N2.