Noninvasive visualization of respiratory viral infection using bioorthogonal conjugated near-infrared-emitting quantum dots.

Highly pathogenic avian influenza A viruses are emerging pandemic threats in human beings. Monitoring the in vivo dynamics of avian influenza viruses is extremely important for understanding viral pathogenesis and developing antiviral drugs. Although a number of technologies have been applied for tracking viral infection in vivo, most of them are laborious with unsatisfactory detection sensitivity. Herein we labeled avian influenza H5N1 pseudotype virus (H5N1p) with near-infrared (NIR)-emitting QDs by bioorthogonal chemistry. The conjugation of QDs onto H5N1p was highly efficient with superior stability both in vitro and in vivo. Furthermore, QD-labeled H5N1p (QD-H5N1p) demonstrated bright and sustained fluorescent signals in mouse lung tissues, allowing us to visualize respiratory viral infection in a noninvasive and real-time manner. The fluorescence signals of QD-H5N1p in lung were correlated with the severity of virus infection and significantly attenuated by antiviral agents, such as oseltamivir carboxylate and mouse antiserum against H5N1p. The biodistribution of QD-H5N1p in lungs and other organs could be easily quantified by measuring fluorescent signals and cadmium concentration of virus-conjugated QDs in tissues. Hence, virus labeling with NIR QDs provides a simple, reliable, and quantitative strategy for tracking respiratory viral infection and for antiviral drug screening.