Abstract Body: Background: Influenza, primarily a respiratory disease, causes cardiac complications in up to 40% of hospitalized patients, unfortunately the mechanisms behind these complications are poorly understood. To study these in animal models, we developed a mouse-adapted 2009 pandemic H1N1 virus (A/California/4/09) that causes cardiac effects in humans. The adapted strain carries a single mutation (PB2-E158A) enhancing viral replication in mouse cells. This virus causes significant lung and cardiac issues in wild type (WT) mice and allows us to explore inflammatory pathways, such as pyroptotic cell death mediated by Gasdermin D (GSDMD), in influenza-associated cardiac phenotypes.
Aim: To understand cardiac complications of severe influenza virus infections and to develop therapeutic interventions based on this knowledge.
Approach: Mice were infected with either the parental 2009 H1N1 strain or the adapted H1N1-E158A variant at a dose of 200 TCID₅₀. In separate experiments, WT and GSDMD knockout (KO) mice were challenged with the adapted virus at the same dose. All mice were 8 weeks old and monitored for weight loss, mortality, viral titers, inflammatory products/gene signatures, and signs of cardiac electrical dysfunction and fibrosis.
Results: In WT mice, H1N1-E158A infection caused higher mortality, increased pathogenicity, more severe lung dysfunction, more severe cardiac electrical dysfunction, more severe cardiac fibrosis compared to the parental strain. Enhanced virulence was associated with higher viral titers in lungs and hearts. RNA sequencing of infected hearts revealed significant changes in pathways related to inflammation, fibrosis, circadian rhythm, and mitochondrial function, suggesting underlying drivers of heart disease. We found that GSDMD KO mice showed lower levels of mortality, cardiac inflammation, fibrosis, and electrical dysfunction, highlighting the potential of GSDMD as a therapeutic target.
Conclusion: The H1N1-E158A virus provides a model for studying cardiac complications of influenza in WT mice. Targeting the GSDMD/pyroptosis pathway to decrease inflammation may offer a promising strategy for treating influenza, including its heart complications.
Significance: This study presents the first WT mouse model of severe influenza with cardiac involvement and identifies GSDMD as a new therapeutic target, paving the way for targeted treatments.