A Vesicular Stomatitis Virus Replicon-Based Bioassay for the Rapid and Sensitive Determination of Multi-Species Type I Interferon
Figure 5
Analysis of type I IFN stability.
(a) Human IFN-β and porcine IFN-α (each at 800 units/ml) were heated for 30 min at the indicated temperatures and thereafter diluted 1∶10 with medium containing 5% FBS. The heat-treated IFN preparations were incubated for 20 h with NHDF and PK-15 cells, respectively (8 units per 5×104 cells). Luciferase reporter activity was determined in cell lysates 5 hours post infection with VSV*ΔG(Luc). (b) Human IFN-β and (c) human IFN-λ were incubated for 30 min at 20°C with either 0.1 M HCl, 0.1 M NaOH, or H2O, and then adjusted to neutral pH. NHDF and Calu-3 cells were incubated for 20 h with fourfold serial dilutions of HCl/NaOH-treated IFN-β and IFN-λ, respectively, and subsequently infected with VSV*ΔG(Luc). Firefly luciferase activity was determined in cell lysates 5 h post infection.