2.5 Data analysis
Based on the inhibition of virus growth, the half-maximal effective concentration (EC50) of aprotinin was calculated using the GraphPad Prism program (version 5; San Diego, CA, USA). This procedure is commonly known as a logistic regression using the following formula: Y = 1/1 + 10 ([logEC50 – logX] × Hillslope), where Y represents response (inhibition of virus growth), and X represents the concentration of aprotinin. Hillslope is the parameter to describe the steepness of the curve. The data analysis was performed using GraphPad Prism for Windows, and differences were evaluated by one-way ANOVA. P values less than 0.05 (P< 0.05) were considered statistically significant.