Low-Avidity Autoantibodies against Bactericidal/Permeability-Increasing Protein Occur in Gram-Negative and...

Area of Science:

• Immunology
• Microbiology
• Infectious Diseases

Background:

• Antibody autoreactivity against bactericidal/permeability-increasing protein (BPI) is associated with Pseudomonas aeruginosa infection in cystic fibrosis (CF), bronchiectasis (BE), and COPD.
• The pathogen-specific nature of BPI autoreactivity requires further investigation, particularly in acute bacteremic settings.

Purpose of the Study:

• To investigate the pathogen-specific nature of antibody autoreactivity against BPI in patients with bacteremia.
• To compare the avidity of anti-BPI IgG responses in acute bacteremia versus chronic respiratory infections.

Main Methods:

• Sera from five patient cohorts (n=214), including bacteremic patients (n=32), were analyzed for antibodies to BPI and bacterial antigens using ELISA.
• Autoantibody titers and avidity were measured. Antibody responses were correlated with bacterial culture results.

Main Results:

• Bacteremic patient sera showed significant IgG autoreactivity against BPI in infections with P. aeruginosa (64.7%) and Escherichia coli (46.7%).
• Anti-BPI IgG responses were observed in 14.9% of bacteremic patients, including those with Gram-positive bacteria like Staphylococcus aureus.
• Sera from bacteremic patients exhibited low-avidity anti-BPI IgG, contrasting with high-avidity responses seen in chronic respiratory infections.

Conclusions:

• Low-avidity anti-BPI IgG responses can be an acute response to bacteremia, irrespective of the specific pathogen.
• Chronic infection, particularly with P. aeruginosa, selects for high-avidity anti-BPI responses, suggesting implications for airway immunity.