Related Experiment Videos
Interactions between bacteria and influenza A virus in the development of influenza pneumonia
H Scheiblauer1, M Reinacher, M Tashiro
1Institut für Virologie Justus-Liebig-Universität, Giessen, Germany.
Abstract:
Different proteases from various microorganisms present in the respiratory tract were capable of enhancing influenza virus infectivity and pathogenicity in mice by proteolytic activation of hemagglutinin (HA). Aerococcus viridans, isolated from a patient with pneumonia, secreted a protease that could activate HA directly, similarly to some Staphylococcus aureus strains. The protease of Pseudomonas aeruginosa could not activate HA directly, but combined application of P. aeruginosa protease and virus into mice enhanced virus titers and pathogenicity. Generation of trypsin-like activity in bronchoalveolar lavage fluids resulting from this combination treatment may be responsible for HA activation. A similar indirect effect on HA activation was induced by streptokinase and staphylokinase, which are known to generate plasmin by plasminogen activation. It was concluded that plasminogen-activating streptococci and staphylococci facilitate viral replication and pathogenicity of plasmin-sensitive influenza virus strains by amplification of the plasminogen/plasmin system.
Insights
Microbial proteases enhance influenza virus by activating hemagglutinin (HA). Some proteases directly activate HA, while others indirectly boost influenza infectivity through systems like plasminogen/plasmin.
Area of Science:
- Microbiology
- Virology
- Biochemistry
Background:
- Respiratory tract microorganisms produce proteases.
- Proteolytic activation of viral hemagglutinin (HA) is crucial for influenza virus infectivity.
- Microbial proteases can influence influenza virus pathogenicity.
Purpose of the Study:
- To investigate the role of microbial proteases in enhancing influenza virus infectivity and pathogenicity.
- To determine the mechanisms by which different proteases affect influenza virus HA activation.
Main Methods:
- Isolation and characterization of proteases from respiratory microorganisms.
- In vitro and in vivo experiments to assess protease activity on influenza virus HA.
- Analysis of bronchoalveolar lavage fluids for enzymatic activity.
Main Results:
- Aerococcus viridans protease directly activated influenza HA, similar to some Staphylococcus aureus proteases.
- Pseudomonas aeruginosa protease indirectly enhanced influenza virus titers and pathogenicity, potentially via trypsin-like activity.
- Streptokinase and staphylokinase indirectly activated HA by generating plasmin from plasminogen.
Conclusions:
- Certain microbial proteases directly activate influenza HA, increasing infectivity.
- Indirect activation of HA by microbial proteases, through systems like plasminogen/plasmin, also enhances influenza pathogenicity.
- Plasminogen-activating bacteria contribute to influenza virus replication and severity in susceptible strains.