Exploring Peripheral and Cardiac Immune Responses in a Pneumosepsis Mouse Model with Group A Streptococcus.

Area of Science:

• * Microbiology and Immunology
• * Pathogen-host interactions

Background:

• * Streptococcus pyogenes (Group A Streptococcus, GAS) is a significant human pathogen causing diverse infections.
• * GAS colonization in the nasopharynx can lead to severe conditions like pneumosepsis.
• * Streptokinase, a GAS virulence factor, activates human plasminogen, aiding bacterial spread and potentially influencing immune responses.

Purpose of the Study:

• * To investigate systemic and cardiac immune cell responses during GAS pneumonia and pneumosepsis.
• * To explore the role of human plasminogen in GAS infection dynamics.
• * To identify potential biomarkers for differentiating local versus systemic GAS infections.

Main Methods:

• * Development of a murine pneumosepsis model using a transgenic mouse strain expressing human plasminogen.
• * Analysis of blood immune cell profiles and plasma protein levels.
• * Examination of cardiac immune cell infiltration in infected animals.

Main Results:

• * Human plasminogen is critical for GAS colonization and systemic dissemination from the nasopharynx.
• * Pneumosepsis significantly alters blood immune cell and plasma protein profiles, suggesting potential diagnostic biomarkers.
• * Invasive infections lead to increased pro-inflammatory immune cells in the heart, potentially displacing resident macrophages.

Conclusions:

• * The developed murine model is effective for studying GAS pneumonia and pneumosepsis pathophysiology.
• * Human plasminogen plays a crucial role in GAS systemic spread.
• * Immune cell changes in blood and heart offer insights into infection severity and potential therapeutic targets.