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. Author manuscript; available in PMC: 2013 Nov 15.
Published in final edited form as: J Immunol. 2012 Oct 1;189(10):4921–4929. doi: 10.4049/jimmunol.1201916

Figure 4. Cross-reactive immunity to influenza protects from secondary infection with both gram-positive and gram-negative bacteria.

Figure 4

(A–C) C57BL/6 mice were infected with H3N2 influenza or immunized intraperitoneally with recombinant NP (rNP) using LPS/alum adjuvant; controls were mock immunized with PBS or adjuvant alone, respectively. After 21 days, mice were challenged intranasally with H1N1 influenza, followed 5 days later with serotype 3 S. pneumoniae (Spn) strain URF918 (23). (A) Survival (n=10 mice/group). (B) Bacterial burden in the lung 48 hours after Spn infection. (C) Bacterial burden in the blood 48 hours after Spn infection. Infection with H3N2 or immunization with rNP significantly increased survival (both p<0.0001 by Log rank tests) and decreased bacterial burden in lung and blood (all p=0.008 by Mann Whitney tests). (D–F) C57BL/6 mice were infected with H3N2 influenza or immunized intraperitoneally with recombinant NP (rNP) using LPS/alum adjuvant; controls were mock immunized with PBS or adjuvant alone, respectively. After 21 days, mice were challenged intranasally with H1N1 influenza, followed 5 days later with Klebsiella pneumoniae clinical isolate strain IA565 (24). (D) Survival (n=10 mice/group). (E) Bacterial burden in the lung 48 hours after Spn infection. (F) Bacterial burden in the blood 48 hours after Spn infection. Infection with H3N2 or immunization with rNP significantly increased survival (both p<0.0005 by Log rank tests), and significantly decreased bacterial burden in lung (p=0.02 and 0.008, respectively, by Mann Whitney tests).