Interleukin-6 overexpression and elevated granulocyte-to-lymphocyte ratio indicate hepatic stress in experimental group a Streptococcus sepsis

Group A Streptococcus (GAS) is a pathogen that is capable of colonizing various infection sites and can potentially elicit an inadequate immune response that will lead to sepsis. The processes underlying this misdirected immune reaction remain poorly understood, and reliable biomarkers for indicating impending organ failure during sepsis are still missing. The present study aims to identify parameters that can predict the onset of end-organ damage in the course of sepsis. To that extent, we investigated key aspects of the immune response in early-phase sepsis following infection of different tissues in a mouse model, using Brefeldin A to link cytokine production to specific cell types through multi-parameter flow cytometry. Subcutaneous and intravenous GAS infections resulted in clinical sepsis, which was paralleled by peripheral blood lymphopenia. Intravenous infection in particular was associated with a higher bacterial burden in the liver that strongly correlated with an increased granulocyte-to-lymphocyte ratio of the peripheral blood. Strikingly, IL-6 overexpression was more pronounced in intravenous infection and strongly correlated with hepatic stress, indicated by elevated bacterial loads in the liver. Collectively, our data highlight the potential utility of IL-6 in conjunction with an elevated granulocyte-to-lymphocyte ratio as promising early indicators of concomitant liver stress in sepsis.