Metabolic Reprogramming of Host Cells by Virulent Francisella tularensis for Optimal Replication and Modulation of Inflammation

Abstract

A shift in macrophage metabolism from oxidative phosphorylation to aerobic glycolysis is a requirement for activation to effectively combat invading pathogens. Francisella tularensis is a facultative intracellular bacterium that causes an acute, fatal disease called tularemia. Its primary mechanism of virulence is its ability to evade and suppress inflammatory responses while replicating in the cytosol of macrophages. The means by which F. tularensis modulates macrophage activation are not fully elucidated. In this study, we demonstrate that virulent F. tularensis impairs production of inflammatory cytokines in primary macrophages by preventing their shift to aerobic glycolysis, as evidenced by the downregulation of hypoxia inducible factor 1α and failure to upregulate pfkfb3. We also show that Francisella capsule is required for this process. In addition to modulating inflammatory responses, inhibition of glycolysis in host cells is also required for early replication of virulent Francisella. Taken together, our data demonstrate that metabolic reprogramming of host cells by F. tularensis is a key component of both inhibition of host defense mechanisms and replication of the bacterium.