TCID50 assay

Isolated IBRV venom was subsequently diluted to 10-folds (10⁻¹ to 10⁻¹⁰) and inoculated to MDBK cells that had grown to 80%–90% confluence in 96-well microculture plates, with 8 wells for each dilution fold and 100 μL for each well. Cells without virus inoculation were set as the control. Cells were incubated at 37°C in 5% CO₂ for 1 h followed by cultivation using low serum DMEM medium (2.5% serum) at 37°C in a 5% CO₂ incubator for CPE observation. CPE was observed under a microscope for 5 consecutive days, and TCID50 was calculated by Reed–Muench method.