Rapid antiviral assay using QD-tagged fish virus as imaging nanoprobe

Development of rapid antiviral assays can expedite the process of screening potential agents against viral pathogens. In the present study, fluorescent quantum dots (QDs) incorporated with infectious pancreatic necrosis virus (IPNV) were used as imaging nanoprobes to detect the threshold amount of poly I:C (an interferon inducer) required to induce zebrafish cells into an antiviral state against IPNV. QD-IPNV hybrids were formed by colloidal clustering of negatively charged QDs and IPNV, using the cationic polymer polybrene (50 μg/mL). To test the screening potential of the QD-IPNV hybrids for anti-IPNV drug candidates, zebrafish ZF4 cells primed with the immunostimulant poly I:C at concentrations of 1, 5, and 10 μg/mL for 6 h were used as a model system. After poly I:C treatment, cells were exposed to the QD-IPNV hybrids for 6 h at a multiplicity of infection (MOI) of 5. The anti-IPNV effectiveness of poly I:C was assessed via fluorescence intensity of the QDs. Our results showed that ZF4 cells primed with poly I:C at 10 μg/mL were highly protected from IPNV challenge (i.e., no detection of QD fluorescence). In summary, a rapid and efficient cell-based imaging platform has been developed for assessing the anti-IPNV activity of poly I:C on ZF4 cells using QD-IPNV hybrids. This approach may be applied to a wider range of fish species and fish pathogenic viruses.