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Published on: February 23, 2014
Immune enhancement of pulmonary bactericidal activity in murine virus pneumonia
Abstract:
Bacterial multiplication in the lung associated with murine Sendai virus pneumonia is caused by virus-induced defects in pulmonary bactericidal mechanisms. The nature of this effect has been studied in animals immunized against the challenge bacteria. Mice were immunized against Proteus mirabilis by intraperitoneal inoculation and by aerosol inhalation. After the development of immunity, mice were infected aerogenically with 10(4) TCID(50) of Sendai virus. 7 days later, during the height of the bronchial inflammation and pulmonary consolidation, the mice were challenged with an aerosol of viable (35)S-labeled Proteus mirabilis or (32)P-labeled Staphylococcus aureus.Nonimmunized virus-infected animals showed marked impairment of pulmonary bactericidal activity with subsequent multiplication of the bacterial strain in the case of Proteus mirabilis. Immunized nonvirus-infected animals showed enhancement of pulmonary bactericidal activity for the homologous and heterologous strains in comparison with nonimmunized animals. Virus-infected animals immunized by aerosol showed enhanced bactericidal activity against the homologous but not the heterologous bacterial strain. Neither virus infection nor immunization had a significant effect on the transport of particles in the lung. The data demonstrated that the bacterial multiplication associated with the virus pneumonia was prevented by preceding immunization against the homologous challenge organism. The data suggest a mechanism for controlling bacterial multiplication associated with virus pneumonias.
Insights
Pre-existing immunity prevents bacterial multiplication during viral pneumonia by enhancing lung defenses. This study shows immunization can control secondary bacterial infections following viral respiratory illness.
Area of Science:
- Immunology
- Microbiology
- Pulmonary Medicine
Background:
- Viral pneumonia can lead to secondary bacterial infections due to impaired lung defenses.
- Sendai virus infection in mice causes defects in pulmonary bactericidal mechanisms, allowing bacterial growth.
Purpose of the Study:
- To investigate if prior immunization against bacteria can prevent bacterial multiplication in the lungs during Sendai virus pneumonia.
- To understand the role of immunization in modulating pulmonary bactericidal activity in the context of viral infection.
Main Methods:
- Mice were immunized against Proteus mirabilis via intraperitoneal inoculation or aerosol inhalation.
- Mice were infected with Sendai virus, followed by challenge with labeled Proteus mirabilis or Staphylococcus aureus.
- Pulmonary bactericidal activity and particle transport were assessed in virus-infected and/or immunized mice.
Main Results:
- Non-immunized, virus-infected mice exhibited impaired bacterial clearance and bacterial multiplication.
- Immunization enhanced pulmonary bactericidal activity in non-infected mice.
- Virus-infected mice immunized by aerosol showed enhanced clearance of the homologous bacteria but not heterologous bacteria.
Conclusions:
- Preceding immunization against a specific bacterium can prevent its multiplication during Sendai virus-induced pneumonia.
- Immunization strategies may offer a mechanism to control secondary bacterial infections complicating viral pneumonias.
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