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Role of polymorphonuclear neutrophils in a murine model of Chlamydia psittaci-induced abortion
A J Buendía1, R M De Oca, J A Navarro
1Departamento de Patología Animal (Microbiología e Inmunología), Facultad de Veterinaria, Universidad de Murcia, Murcia, Spain.
Abstract:
To assess the role of polymorphonuclear neutrophils (PMNs) in Chlamydia psittaci infection in a pregnant mouse model, pregnant and nonpregnant Swiss OF1 mice were depleted of PMNs by treatment with the RB6-8C5 monoclonal antibody before intraperitoneal infection with C. psittaci serotype 1. Nondepleted mice served as infection controls. Depleted mice aborted earlier and had a much higher mortality rate than nondepleted mice. Bacteriological analysis showed that the number of chlamydiae isolated from the spleens of depleted mice at 5 and 7 days postinfection was 100 times greater than that isolated from nondepleted mice. Histopathological analysis of the placentas of depleted mice showed widespread necrosis of the uteroplacental units, with weak immunoreaction to chlamydial antigen, while the placentas of nondepleted mice showed substantial neutrophil infiltration but no large areas of necrosis, with moderate to strong immunoreaction to chlamydial antigen. The livers of depleted mice showed numerous chlamydial inclusions in the hepatocytes, delayed microgranuloma formation, and in the pregnant animals extensive coagulative periportal necrosis. The livers of nondepleted mice displayed multiple small foci of PMNs and mononuclear cells with microgranuloma formation. Among this group of mice, the pregnant animals always had more hepatic damage than nonpregnant animals. Our results suggest that PMNs play an essential role in the response to C. psittaci primary infection, preventing the uncontrolled multiplication of chlamydiae in the liver and spleen.
Insights
Polymorphonuclear neutrophils (PMNs) are crucial for controlling Chlamydia psittaci infection. Depleting PMNs in pregnant mice led to increased bacterial load, higher mortality, and severe placental damage.
Area of Science:
- Immunology
- Microbiology
- Reproductive Biology
Background:
- Chlamydia psittaci is an important zoonotic pathogen.
- The role of polymorphonuclear neutrophils (PMNs) in C. psittaci infection, particularly during pregnancy, remains unclear.
Purpose of the Study:
- To investigate the role of PMNs in C. psittaci infection using a pregnant mouse model.
- To determine the impact of PMN depletion on infection outcome, bacterial load, and tissue pathology.
Main Methods:
- PMN depletion in pregnant and nonpregnant mice using the RB6-8C5 monoclonal antibody.
- Intraperitoneal infection with C. psittaci serotype 1.
- Bacteriological, histopathological, and immunohistochemical analyses of spleen, placenta, and liver tissues.
Main Results:
- PMN-depleted mice exhibited earlier abortion, higher mortality, and a 100-fold increase in splenic C. psittaci load compared to controls.
- Histopathology revealed widespread placental necrosis in depleted mice, while controls showed neutrophil infiltration and moderate chlamydial antigen immunoreaction.
- Depleted mice had numerous hepatic chlamydial inclusions, delayed granuloma formation, and severe periportal necrosis, especially in pregnant animals.
Conclusions:
- PMNs play a critical role in the host response to primary C. psittaci infection.
- PMNs are essential for controlling chlamydial multiplication in the liver and spleen.
- PMN deficiency exacerbates C. psittaci infection, leading to severe pathology and increased mortality, particularly in pregnant hosts.