Figure 5.

Contribution of PB1-F2 to mortality. Groups of 6 mice were either mock infected with phosphate-buffered saline or infected with influenza viruses at the doses indicated in the legends and then challenged 7 days later with 10⁸ CFU of Staphylococcus aureus strain NRS-193. A) Viruses included wild-type PR8 and an isogenic virus that cannot express the viral cytotoxin PB1-F2 (PR8/ΔPB1-F2). B) Viruses included wild-type PR8, an isogenic version of PR8 expressing the 1918 PB1-F2 protein (PR8/1918 PB1-F2) and the 2009 pandemic H1N1 strain (pH1N1). An asterisk indicates a significant difference revealed by the log-rank test on the Kaplan-Meier survival data (P < .05) compared with the other 2 groups.