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Heterotypic Influenza Infections Mitigate Susceptibility to Secondary Bacterial Infection

ABSTRACT: Influenza associated bacterial super-infections have devastating impacts on the lung and can result in increased risk of mortality. New strains of influenza circulate throughout the population yearly promoting the establishment of immune memory. Nearly all individuals have some degree of influenza memory prior to adulthood. Due to this we sought to understand the role of immune memory during bacterial super-infections. An influenza heterotypic immunity model was established using influenza A/PR/8/34 and A/X31. We report here that influenza experienced mice are more resistant to secondary bacterial infection with methicillin-resistant Staphylococcus aureus as determined by wasting, bacterial burden, pulmonary inflammation, and lung leak, despite significant ongoing lung remodeling. Multidimensional flow cytometry and lung transcriptomics revealed significant alterations in the lung environment in influenza-experienced mice compared with naïve animals. These include changes in the lung monocyte and T cell compartments, characterized by increased expansion of influenza tetramer specific CD8+ T cells. The protection that was seen in memory experienced mouse model is associated with the reduction in inflammatory mechanisms making the lung less susceptible to damage and subsequent bacterial colonization. These findings provide insight into how influenza heterotypic immunity re-shapes the lung environment and the immune response to a re-challenge event, which is highly relevant to the context of human infection.

ORGANISM(S): Mus musculus

PROVIDER: GSE206095 | GEO | 2022/06/27

REPOSITORIES: GEO

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Project description:Background: Pandemic H1N1 influenza A is a newly emerging strain of human influenza that is easily transmitted between people and has spread globally to over 116 countries. Human infection leads to symptoms ranging from mild to severe with lower respiratory complications observed in a small but significant number of infected individuals. Little is currently known about host immunity and Pandemic H1N1 influenza infections. Methods: We examined the pathogenic potential of the pandemic influenza A vaccine strain, A/California/07/2009 (H1N1), in ferrets, and characterized the host immune responses using microarray analysis. Gene expression profiles in lung tissue were compared with those from ferrets infected with A/Brisbane/59/2007. Results: Chemokines CCL2, CCL8, CXCL7 and CXCL10 along with the majority of ISGs were expressed early, correlated to lung pathology, and abruptly decreased expression in 5 days. Interestingly, the drop in innate immune gene expression was replaced by a significant increase in the expression of the adaptive immune genes for granzymes and immunoglobulins. Serum anti-pandemic influenza H1N1 antibodies were also observed on day 7, commensurate with the elimination of viral load. Conclusions: We propose that the innate phase of host immunity causes lung pathology and a delay or failure to effectively switch to the adaptive phase contributes to morbidity and mortality during severe human pandemic H1N1 influenza A infections. Keywords: influenza, immune response, cytokines, chemokines, lung infection, time course In the experiment with influenza A/California/07/2009 (H1N1),15 ferrets were randomly allocated to 5 groups: Day 0 (before infection), and Day 3, 5, 7 and 14 (post infection) with 3 biological replicates for each group. Likewise, a second experiment with A/Brisbane/59/2007 (H1N1) was carried out using the same experimental groups, except for a group in Day 2, instead Day 3. Ferrets were euthanized and lung tissue was excised for RNA purification on the scheduled date. The subsequent gene expression analysis was performed with Affymetrix GeneChip Canine Genome 2.0 Array. Day 0 groups were used as control.

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Heterotypic Influenza Infections Mitigate Susceptibility to Secondary Bacterial Infection

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