Objective: To evaluate mice as experimental animals for Chlamydia pneumoniae (C. Pneumoniae) infection and investigate the pathogenesis of C. pneumoniae pneumonitis.
Methods: The Icr mice were inoculated with C. pneumoniae, strain CWL-029, by the intranasal or intravenous routes. After a single inoculation, mice were killed on the 1st, 3rd, 7th, 15th, 21th, 28th and 60th day separately. The pathological changes of lung tissue were analyzed.
Results: The Icr mice were shown to be susceptible to C. pneumoniae. Inoculation of mice with C. pneumoniae induced a prolonged course of lung infection, as demonstrated by persistence of lung pathology (60 days). In the intranasal inoculation of mice, the lung pathology was characterized by patchy interstitial pneumonitis with predominately neutrophil leukocyte infiltration in the early(7 days) and lyphocytes infiltration in the later stages(14 days later) of infection. After i.v. inoculation, a similarly interstitial pneumonitis was seen, but it was milder and more patchy, especially in the early stage. C. pneumoniae DNA was detected by polymerase chain reaction(PCR) intermittently in the lung tissue. Inoculated mice developed serum IgG antibody responses.
Conclusions: The Icr mice were shown to be susceptible to C. pneumoniae and the pulmonary infection was characterized by interstitial pneumonitis, especially in mice of intranasal inoculation.