Virosome-masked ratiometric nanoprobes for in vivo dynamic imaging of influenza a virus infection.

In vivo fluorescent in situ visualization of viral infection dynamics is crucial for elucidating the mechanisms of viral pathogenesis. However, current approaches lack sufficient specificity and sensitivity for spatiotemporal monitoring of viral infection in vivo. Here, we proposed virosome-masked ratiometric nanoprobes (VMR-NPs) integrated with dual-stimuli-responsive near-infrared (NIR) Förster resonance energy transfer (FRET) reporters that specifically recognize influenza A virus (IAV) viral RNA (vRNA) and apurinic/apyrimidinic endonuclease 1 (APE1). Surface hemagglutinin (HA) envelope protein of IAV virosome endows VMR-NPs with enhanced host-cell association and IAV-like intracellular trafficking behavior. Following internalization, vRNA recognition together with APE1-assisted signal amplification modulates the ratiometric fluorescence output of VMR-NPs, enabling sensitive detection of infection-associated signal changes in vitro and in vivo. This study establishes an IAV virosome-masked sensing platform for imaging infection-associated IAV burden and provides a useful tool for studying virus-related biological processes.