Preceding influenza infection impacts neutrophil response to Aspergillus fumigatus and Staphylococcus aureus

Area of Science:

• Immunology
• Infectious Diseases
• Pulmonary Medicine

Background:

• Influenza infection can lead to secondary pneumonia from bacterial or fungal pathogens.
• Neutrophils are crucial immune cells for fighting infections.
• Understanding post-influenza super-infections is vital for developing effective treatments.

Purpose of the Study:

• To investigate the immunopathological mechanisms of secondary pneumonia following influenza infection.
• To compare neutrophil transcriptional pathways in influenza-associated pulmonary aspergillosis (IAPA) and post-influenza methicillin-resistant Staphylococcus aureus (MRSA) pneumonia.

Main Methods:

• Analysis of lung neutrophil transcriptional pathways in mouse models.
• Comparison of gene expression profiles in neutrophils from single infections versus super-infections.
• Direct comparison of neutrophil pathways between IAPA and post-influenza MRSA pneumonia.

Main Results:

• Neutrophil chemotaxis and degranulation pathways were inhibited in IAPA compared to single Aspergillus fumigatus infection.
• Neutrophil recruitment and phagocytosis pathways were inhibited in IAPA compared to influenza infection alone.
• Neutrophil recruitment, degranulation, and cytokine signaling pathways were altered in post-influenza MRSA pneumonia compared to single MRSA infection or influenza infection.
• Cytokine induction and neutrophil function pathways were more inhibited in IAPA neutrophils than in post-influenza MRSA pneumonia neutrophils.

Conclusions:

• Influenza infection leads to neutrophil dysfunction.
• This dysfunction predisposes individuals to secondary bacterial and fungal infections.
• Influenza-associated super-infections involve distinct alterations in neutrophil immune responses.