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Experimental Chlamydia pneumoniae infection in mice: effect of reinfection and passive immunization
S E Kaukoranta-Tolvanen1, A L Laurila, P Saikku
1Department of Virology, University of Helsinki, Finland.
Abstract:
NIH/S mice were infected intranasally with Chlamydia pneumoniae isolate Kajaani 6 and rechallenged after either 28 or 70 days. A partial resistance to reinfection, indicated by a reduced recovery of live organisms, was noted at both time points of rechallenge: positive isolations from lung homogenates and/or bronchoalveolar lavage fluids were observed in fewer mice and the yields of isolated chlamydiae remained smaller, as compared to primary infection. However, a previous infection did not confer any protection against inflammatory changes. A strong peribronchial and perivascular inflammation with infiltrating lymphocytes and plasma cells was noted in the lungs of primary infected, as well as reinfected, mice. The effect of passive immunization was also studied. When mice were given convalescent or hyperimmune sera intraperitoneally before inoculation, lower C. pneumoniae isolation yields were detected. As in the rechallenge experiment, marked inflammation could still be seen in the lungs, now with polymorphonuclear leukocyte infiltration. The results suggest that immunological reactions play a role in the pathogenesis of C. pneumoniae infection. Antibodies may be important in reducing the amount of infective elementary bodies, but complete clearing of C. pneumoniae could not be achieved in these experiments, even less a protection against inflammatory lung changes.
Insights
Mice previously infected with Chlamydia pneumoniae showed partial resistance to reinfection but still developed significant lung inflammation. Antibodies reduced bacterial load but did not prevent inflammation or fully clear the infection.
Area of Science:
- Immunology
- Microbiology
- Pathogenesis
Background:
- Chlamydia pneumoniae is a significant respiratory pathogen.
- Understanding the host immune response to C. pneumoniae is crucial for developing effective treatments.
Purpose of the Study:
- To investigate the development of resistance to reinfection and associated inflammatory responses following Chlamydia pneumoniae infection in mice.
- To evaluate the role of antibodies in protection against C. pneumoniae infection and associated lung inflammation.
Main Methods:
- Mice were infected intranasally with Chlamydia pneumoniae and rechallenged at different time points.
- Lung homogenates and bronchoalveolar lavage fluids were analyzed for bacterial load.
- Histopathological examination of lung tissues assessed inflammatory changes.
- Passive immunization with convalescent or hyperimmune sera was performed.
Main Results:
- Reinfection resulted in reduced bacterial loads compared to primary infection, indicating partial resistance.
- Previous infection did not protect against inflammatory lung changes, characterized by lymphocyte and plasma cell infiltration.
- Passive immunization with sera lowered C. pneumoniae isolation yields but did not prevent polymorphonuclear leukocyte infiltration and inflammation.
Conclusions:
- Immunological responses play a role in the pathogenesis of Chlamydia pneumoniae infection.
- Antibodies contribute to reducing bacterial burden but do not achieve complete clearance or prevent lung inflammation.
- Further research is needed to develop strategies for complete pathogen eradication and control of inflammation.