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Effects of influenza A nucleoprotein on polymorphonuclear neutrophil function
J A Cooper1, R Carcelen, R Culbreth
1Pulmonary Sections, Birmingham VA Medical Center, Alabama, USA.
The Journal of Infectious Diseases
|February 1, 1996
Summary
Influenza A nucleoprotein impairs neutrophil function, including chemotaxis and superoxide production, potentially explaining secondary bacterial pneumonia during flu infections. This protein affects neutrophil calcium levels but not degranulation.
Area of Science:
- Virology and Immunology
- Cellular Biology
Background:
- Influenza virus infection often leads to polymorphonuclear neutrophil (PMNL) dysfunction.
- This dysfunction can result in secondary bacterial pneumonia.
- A human protein inhibiting PMNLs shares homology with influenza A nucleoprotein.
Purpose of the Study:
- To investigate the effects of purified influenza A nucleoprotein on PMNL functions.
- To determine if influenza A nucleoprotein contributes to neutrophil defects during infection.
Main Methods:
- Purified influenza A nucleoprotein was used to treat PMNLs.
- Assays measured PMNL chemotaxis, superoxide production, degranulation (elastase, beta-glucuronidase release), and cytosolic calcium concentration.
Main Results:
- Purified influenza A nucleoprotein significantly inhibited PMNL chemotaxis and superoxide production.
- Nucleoprotein induced an increase in PMNL cytosolic calcium concentration.
- No significant differences were observed in FMLP-stimulated elastase or beta-glucuronidase release.
Conclusions:
- Influenza A nucleoprotein appears to be responsible for some neutrophil defects observed during influenza infection.
- These findings suggest a mechanism by which influenza virus compromises host defense against secondary bacterial infections.