Figure 1. Influenza memory experienced mice are better protected against secondary bacterial infection with Staphylococcus aureus.

A) Infection scheme for memory super-infected C57BL/6 mice. Mice were infected on day 0 with A/X-31 H3N2 (X-31) and at 53 to 54 days post infection (p.i.) mice were given A/Puerto Rico/8/1934 H1N1 (PR8). MRSA USA300 (MRSA) was given on day 59 or 60 p.i. and mice were harvested on day 60 or 61 p.i. B) Percent of weight loss was calculated starting from secondary infection with PR8 for each of the treatment groups and compared to mice that received PBS only and MRSA only, with day 6 being the date that MRSA was given on (PBS= 15, acute n=17, memory n=23, PBS+MRSA n=15). C) Number of MRSA colonies plated from infected mouse lung homogenates (acute n=30, memory n=34, PBS+MRSA n=15). D) Total infiltrating cell counts, percent of monocytes, as well as percent of neutrophils were determined by cytospins using bronchoalveolar lavage fluid collected from infected mouse lungs at time of harvest (acute n=12, memory n=16, PBS+Memory n=11). E) Presence of viral protein was assessed in cDNA from total mouse lung via relative gene expression analysis of PR8 (Matrix protein) (acute n=8, memory n=8). F) Relative gene expression of interferon classes (Ifn-λ3, Ifn-γ, and Ifn-β) from total mouse lung cDNA. ND=non-detectable. p values: *<0.05, **<0.01 ***<0.001, ****<0.0001. Mouse figure was created with BioRender.com.