2.7. Virus Titration (TCID50 Determination)

The stable cell lines of LLC-PK1 with shRNA expression were harvested at 48 hpi and subjected to freeze–thaw three times. After clarification based on the standard methodology, the cell culture supernatants were collected and made into a 10-fold serial dilution (10⁻¹ to 10⁻¹⁰), and then added into 96-well plates pre-seeded with LLC-PK1 cells to determine the virus titers expressed as TCID₅₀, which was determined using the Reed–Muench method [30].