Characterization of a pneumococcal meningitis mouse model
Barry Mook-Kanamori1, Madelijn Geldhoff, Dirk Troost
1Department of Neurology, Center of Infection and Immunity Amsterdam (CINIMA), Academic Medical Center, Amsterdam, the Netherlands.
Background:
S. pneumoniae is the most common causative agent of meningitis, and is associated with high morbidity and mortality. We aimed to develop an integrated and representative pneumococcal meningitis mouse model resembling the human situation.
Methods:
Adult mice (C57BL/6) were inoculated in the cisterna magna with increasing doses of S. pneumoniae serotype 3 colony forming units (CFU; n = 24, 104, 105, 106 and 107 CFU) and survival studies were performed. Cerebrospinal fluid (CSF), brain, blood, spleen, and lungs were collected. Subsequently, mice were inoculated with 104 CFU S. pneumoniae serotype 3 and sacrificed at 6 (n = 6) and 30 hours (n = 6). Outcome parameters were bacterial outgrowth, clinical score, and cytokine and chemokine levels (using Luminex®) in CSF, blood and brain. Meningeal inflammation, neutrophil infiltration, parenchymal and subarachnoidal hemorrhages, microglial activation and hippocampal apoptosis were assessed in histopathological studies.
Results:
Lower doses of bacteria delayed onset of illness and time of death (median survival CFU 104, 56 hrs; 105, 38 hrs, 106, 28 hrs. 107, 24 hrs). Bacterial titers in brain and CSF were similar in all mice at the end-stage of disease independent of inoculation dose, though bacterial outgrowth in the systemic compartment was less at lower inoculation doses. At 30 hours after inoculation with 104 CFU of S. pneumoniae, blood levels of KC, IL6, MIP-2 and IFN- γ were elevated, as were brain homogenate levels of KC, MIP-2, IL-6, IL-1β and RANTES. Brain histology uniformly showed meningeal inflammation at 6 hours, and, neutrophil infiltration, microglial activation, and hippocampal apoptosis at 30 hours. Parenchymal and subarachnoidal and cortical hemorrhages were seen in 5 of 6 and 3 of 6 mice at 6 and 30 hours, respectively.
Conclusion:
We have developed and validated a murine model of pneumococcal meningitis.
Insights
This study developed a new mouse model for pneumococcal meningitis, a common cause of severe illness. The model accurately reflects human disease progression and inflammation, aiding future research.
Area of Science:
- Microbiology
- Immunology
- Neurology
Background:
- Streptococcus pneumoniae is a leading cause of meningitis, associated with significant morbidity and mortality.
- Existing models do not fully replicate the human condition of pneumococcal meningitis.
Purpose of the Study:
- To develop and validate an integrated and representative mouse model of pneumococcal meningitis.
- The model aims to mimic the human disease scenario for improved research.
Main Methods:
- Adult C57BL/6 mice were inoculated intracisternally with varying doses of S. pneumoniae serotype 3.
- Survival, bacterial load, clinical scores, cytokine/chemokine levels, and histopathology were assessed.
- Histopathology included evaluation of meningeal inflammation, neutrophil infiltration, hemorrhages, microglial activation, and apoptosis.
Main Results:
- Inoculation dose influenced survival time, with higher doses leading to shorter survival.
- Bacterial titers in CSF and brain were comparable at end-stage disease across doses.
- Elevated inflammatory markers (KC, IL-6, MIP-2, IFN-γ, IL-1β, RANTES) and neuropathological changes (inflammation, apoptosis, hemorrhage) were observed.
Conclusions:
- A validated murine model for pneumococcal meningitis has been successfully developed.
- This model provides a robust platform for studying meningitis pathogenesis and evaluating therapeutics.
