Figure 4.

Pathogenicity of FL/4/06 after 20 total lung-lung passages. (A) TCID₅₀/mL titers of FL/4/06 p20E and p20C. (B) Table breaking down MLD₅₀ values calculated using the Reed–Meunch method (31) for FL/4/06 p20E and p20C. (C) Mice challenged with doses corresponding to logTCID₅₀ of FL/4/06 p20E or p20C were followed for 14 d.p.i. for weight loss (top) and survival after challenge with 6log TCID₅₀ units (bottom). A ≥25% initial weight lost was used as a threshold for humane sacrifice of the animals. (D) Comparison of survival probability of mice challenged with 5log TCID₅₀ of p10E or p20E. No statistically significant difference in survival probability was observed. Statistical differences in TCID₅₀/mL titers were calculated using unpaired t-tests, while statistical significance between group survival was calculated through log-rank Mantel–Cox test. Statistical analysis was performed in GraphPad Prism 9.0 ** p < 0.01).