The innate immune response elicited by Group A Streptococcus is highly variable among clinical isolates and...

Area of Science:

• Microbiology
• Immunology
• Infectious Diseases

Background:

• Group A Streptococcus (GAS) causes significant global morbidity and mortality.
• Macrophages are crucial for controlling GAS infections.
• GAS invasiveness and persistence are linked to pro-inflammatory cytokine production.

Purpose of the Study:

• To investigate the correlation between GAS clinical isolate genotypes and their ability to modulate innate immune responses.
• To analyze the relationship between GAS emm types, clinical history (invasive vs. non-invasive), and macrophage interactions.
• To determine how GAS genotypes influence cytokine and interferon production.

Main Methods:

• Collected 40 independent GAS isolates prevalent in France, representing various emm types.
• Assessed GAS phagocytosis and survival in mouse bone marrow-derived macrophages.
• Quantified pro-inflammatory mediators (IL-6, TNF-α) and type I interferon (IFN-β) production.

Main Results:

• Invasive emm89 GAS isolates showed higher phagocytosis than non-invasive ones and other emm types.
• GAS survival in macrophages varied by emm type, but not by invasive status within an emm type.
• emm1 GAS induced the highest pro-inflammatory cytokine levels, while emm89 induced the earliest IFN-β production.
• Immune response variability existed within emm types, independent of survival and mediator production.

Conclusions:

• GAS emm type is a key determinant of innate immune modulation, influencing phagocytosis and cytokine profiles.
• Invasiveness status does not consistently predict macrophage interaction or inflammatory mediator production within specific GAS emm types.
• Understanding genotype-specific immune responses is crucial for managing GAS infections.